EEG、fNIRS，TMS与EyeLink同步记录的研究论文，按第一作者名字首字母排序。您可以使用关键字搜索，比如P300, Gamma band, NIRS等。您也可以按作者姓名搜索。如果您发现我们漏掉了部分EyeLink论文，请邮件联系！
Rick A Adams; Markus Bauer; Dimitris Pinotsis; Karl J Friston Dynamic causal modelling of eye movements during pursuit: Confirming precision-encoding in V1 using MEG Journal Article Neuroimage, 132 , pp. 175–189, 2016. @article{Adams2016, title = {Dynamic causal modelling of eye movements during pursuit: Confirming precision-encoding in V1 using MEG}, author = {Rick A Adams and Markus Bauer and Dimitris Pinotsis and Karl J Friston}, url = {http://dx.doi.org/10.1016/j.neuroimage.2016.02.055}, doi = {10.1016/j.neuroimage.2016.02.055}, year = {2016}, date = {2016-01-01}, journal = {Neuroimage}, volume = {132}, pages = {175--189}, publisher = {The Authors}, abstract = {This paper shows that it is possible to estimate the subjective precision (inverse variance) of Bayesian beliefs during oculomotor pursuit. Subjects viewed a sinusoidal target, with or without random fluctuations in its motion. Eye trajectories and magnetoencephalographic (MEG) data were recorded concurrently. The target was periodically occluded, such that its reappearance caused a visual evoked response field (ERF). Dynamic causal modelling (DCM) was used to fit models of eye trajectories and the ERFs. The DCM for pursuit was based on predictive coding and active inference, and predicts subjects' eye movements based on their (subjective) Bayesian beliefs about target (and eye) motion. The precisions of these hierarchical beliefs can be inferred from behavioural (pursuit) data. The DCM for MEG data used an established biophysical model of neuronal activity that includes parameters for the gain of superficial pyramidal cells, which is thought to encode precision at the neuronal level. Previous studies (using DCM of pursuit data) suggest that noisy target motion increases subjective precision at the sensory level: i.e., subjects attend more to the target's sensory attributes. We compared (noisy motion-induced) changes in the synaptic gain based on the modelling of MEG data to changes in subjective precision estimated using the pursuit data. We demonstrate that imprecise target motion increases the gain of superficial pyramidal cells in V1 (across subjects). Furthermore, increases in sensory precision – inferred by our behavioural DCM – correlate with the increase in gain in V1, across subjects. This is a step towards a fully integrated model of brain computations, cortical responses and behaviour that may provide a useful clinical tool in conditions like schizophrenia.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper shows that it is possible to estimate the subjective precision (inverse variance) of Bayesian beliefs during oculomotor pursuit. Subjects viewed a sinusoidal target, with or without random fluctuations in its motion. Eye trajectories and magnetoencephalographic (MEG) data were recorded concurrently. The target was periodically occluded, such that its reappearance caused a visual evoked response field (ERF). Dynamic causal modelling (DCM) was used to fit models of eye trajectories and the ERFs. The DCM for pursuit was based on predictive coding and active inference, and predicts subjects' eye movements based on their (subjective) Bayesian beliefs about target (and eye) motion. The precisions of these hierarchical beliefs can be inferred from behavioural (pursuit) data. The DCM for MEG data used an established biophysical model of neuronal activity that includes parameters for the gain of superficial pyramidal cells, which is thought to encode precision at the neuronal level. Previous studies (using DCM of pursuit data) suggest that noisy target motion increases subjective precision at the sensory level: i.e., subjects attend more to the target's sensory attributes. We compared (noisy motion-induced) changes in the synaptic gain based on the modelling of MEG data to changes in subjective precision estimated using the pursuit data. We demonstrate that imprecise target motion increases the gain of superficial pyramidal cells in V1 (across subjects). Furthermore, increases in sensory precision – inferred by our behavioural DCM – correlate with the increase in gain in V1, across subjects. This is a step towards a fully integrated model of brain computations, cortical responses and behaviour that may provide a useful clinical tool in conditions like schizophrenia. |
Kivilcim Afacan-Seref; Natalie A Steinemann; Annabelle Blangero; Simon P Kelly Dynamic interplay of value and sensory information in high-speed decision making Journal Article Current Biology, 28 (5), pp. 795–802, 2018. @article{Afacan-Seref2018, title = {Dynamic interplay of value and sensory information in high-speed decision making}, author = {Kivilcim Afacan-Seref and Natalie A Steinemann and Annabelle Blangero and Simon P Kelly}, doi = {10.1016/j.cub.2018.01.071}, year = {2018}, date = {2018-03-01}, journal = {Current Biology}, volume = {28}, number = {5}, pages = {795--802}, abstract = {In dynamic environments, split-second sensorimotor decisions must be prioritized according to potential payoffs to maximize overall rewards. The impact of relative value on deliberative perceptual judgments has been examined extensively [1–6], but relatively little is known about value-biasing mechanisms in the common situation where physical evidence is strong but the time to act is severely limited. In prominent decision models, a noisy but statistically stationary representation of sensory evidence is integrated over time to an action-triggering bound, and value-biases are affected by starting the integrator closer to the more valuable bound. Here, we show significant departures from this account for humans making rapid sensory-instructed action choices. Behavior was best explained by a simple model in which the evidence representation—and hence, rate of accumulation—is itself biased by value and is non-stationary, increasing over the short decision time frame. Because the value bias initially dominates, the model uniquely predicts a dynamic ‘‘turn-around'' effect on low-value cues, where the accumulator first launches toward the incorrect action but is then re-routed to the correct one. This was clearly exhibited in electrophysiological signals reflecting motor preparation and evidence accumulation. Finally, we construct an extended model that implements this dynamic effect through plausible sensory neural response modulations and demonstrate the correspondence between decision signal dynamics simulated from a behavioral fit of that model and the empirical decision signals. Our findings suggest that value and sensory information can exert simultaneous and dynamically countervailing influences on the trajectory of the accumulation-to-bound process, driving rapid, sensory-guided actions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In dynamic environments, split-second sensorimotor decisions must be prioritized according to potential payoffs to maximize overall rewards. The impact of relative value on deliberative perceptual judgments has been examined extensively [1–6], but relatively little is known about value-biasing mechanisms in the common situation where physical evidence is strong but the time to act is severely limited. In prominent decision models, a noisy but statistically stationary representation of sensory evidence is integrated over time to an action-triggering bound, and value-biases are affected by starting the integrator closer to the more valuable bound. Here, we show significant departures from this account for humans making rapid sensory-instructed action choices. Behavior was best explained by a simple model in which the evidence representation—and hence, rate of accumulation—is itself biased by value and is non-stationary, increasing over the short decision time frame. Because the value bias initially dominates, the model uniquely predicts a dynamic ‘‘turn-around'' effect on low-value cues, where the accumulator first launches toward the incorrect action but is then re-routed to the correct one. This was clearly exhibited in electrophysiological signals reflecting motor preparation and evidence accumulation. Finally, we construct an extended model that implements this dynamic effect through plausible sensory neural response modulations and demonstrate the correspondence between decision signal dynamics simulated from a behavioral fit of that model and the empirical decision signals. Our findings suggest that value and sensory information can exert simultaneous and dynamically countervailing influences on the trajectory of the accumulation-to-bound process, driving rapid, sensory-guided actions. |
C J Aine; H J Bockholt; J R Bustillo; J M Cañive; A Caprihan; C Gasparovic; F M Hanlon; J M Houck; R E Jung; J Lauriello; J Liu; A R Mayer; N I Perrone-Bizzozero; S Posse; J M Stephen; J A Turner; V P Clark; Vince D Calhoun Multimodal neuroimaging in schizophrenia: Description and dissemination Journal Article Neuroinformatics, 15 (4), pp. 343–364, 2017. @article{Aine2017, title = {Multimodal neuroimaging in schizophrenia: Description and dissemination}, author = {C J Aine and H J Bockholt and J R Bustillo and J M Ca{ñ}ive and A Caprihan and C Gasparovic and F M Hanlon and J M Houck and R E Jung and J Lauriello and J Liu and A R Mayer and N I Perrone-Bizzozero and S Posse and J M Stephen and J A Turner and V P Clark and Vince D Calhoun}, doi = {10.1007/s12021-017-9338-9}, year = {2017}, date = {2017-01-01}, journal = {Neuroinformatics}, volume = {15}, number = {4}, pages = {343--364}, publisher = {Neuroinformatics}, abstract = {In this paper we describe an open-access collection ofmultimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also present- ed from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network's collaborative informatics and neuroimaging suite (COINS).}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we describe an open-access collection ofmultimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also present- ed from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network's collaborative informatics and neuroimaging suite (COINS). |
Micah Allen; Darya Frank; D Samuel Schwarzkopf; Francesca Fardo; Joel S Winston; Tobias U Hauser; Geraint Rees Unexpected arousal modulates the influence of sensory noise on confidence Journal Article eLife, 5 , pp. 1–17, 2016. @article{Allen2016, title = {Unexpected arousal modulates the influence of sensory noise on confidence}, author = {Micah Allen and Darya Frank and D {Samuel Schwarzkopf} and Francesca Fardo and Joel S Winston and Tobias U Hauser and Geraint Rees}, doi = {10.7554/eLife.18103}, year = {2016}, date = {2016-01-01}, journal = {eLife}, volume = {5}, pages = {1--17}, abstract = {Human perception is invariably accompanied by a graded feeling of confidence that guides metacognitive awareness and decision-making. It is often assumed that this arises solely from the feed-forward encoding of the strength or precision of sensory inputs. In contrast, interoceptive inference models suggest that confidence reflects a weighted integration of sensory precision and expectations about internal states, such as arousal. Here we test this hypothesis using a novel psychophysical paradigm, in which unseen disgust-cues induced unexpected, unconscious arousal just before participants discriminated motion signals of variable precision. Across measures of perceptual bias, uncertainty, and physiological arousal we found that arousing disgust cues modulated the encoding of sensory noise. Furthermore, the degree to which trial-by-trial pupil fluctuations encoded this nonlinear interaction correlated with trial level confidence. Our results suggest that unexpected arousal regulates perceptual precision, such that subjective confidence reflects the integration of both external sensory and internal, embodied states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Human perception is invariably accompanied by a graded feeling of confidence that guides metacognitive awareness and decision-making. It is often assumed that this arises solely from the feed-forward encoding of the strength or precision of sensory inputs. In contrast, interoceptive inference models suggest that confidence reflects a weighted integration of sensory precision and expectations about internal states, such as arousal. Here we test this hypothesis using a novel psychophysical paradigm, in which unseen disgust-cues induced unexpected, unconscious arousal just before participants discriminated motion signals of variable precision. Across measures of perceptual bias, uncertainty, and physiological arousal we found that arousing disgust cues modulated the encoding of sensory noise. Furthermore, the degree to which trial-by-trial pupil fluctuations encoded this nonlinear interaction correlated with trial level confidence. Our results suggest that unexpected arousal regulates perceptual precision, such that subjective confidence reflects the integration of both external sensory and internal, embodied states. |
Lucía Amoruso; Agustín Ibáñez; Bruno Fonseca; Sebastián Gadea; Lucas Sedeño; Mariano Sigman; Adolfo M García; Ricardo Fraiman; Daniel Fraiman Variability in functional brain networks predicts expertise during action observation Journal Article NeuroImage, 146 , pp. 690–700, 2017. @article{Amoruso2017, title = {Variability in functional brain networks predicts expertise during action observation}, author = {Lucía Amoruso and Agustín Ibá{ñ}ez and Bruno Fonseca and Sebastián Gadea and Lucas Sede{ñ}o and Mariano Sigman and Adolfo M García and Ricardo Fraiman and Daniel Fraiman}, doi = {10.1016/j.neuroimage.2016.09.041}, year = {2017}, date = {2017-01-01}, journal = {NeuroImage}, volume = {146}, pages = {690--700}, publisher = {Elsevier}, abstract = {Observing an action performed by another individual activates, in the observer, similar circuits as those involved in the actual execution of that action. This activation is modulated by prior experience; indeed, sustained training in a particular motor domain leads to structural and functional changes in critical brain areas. Here, we capitalized on a novel graph-theory approach to electroencephalographic data (Fraiman et al., 2016) to test whether variability in functional brain networks implicated in Tango observation can discriminate between groups differing in their level of expertise. We found that experts and beginners significantly differed in the functional organization of task-relevant networks. Specifically, networks in expert Tango dancers exhibited less variability and a more robust functional architecture. Notably, these expertise-dependent effects were captured within networks derived from electrophysiological brain activity recorded in a very short time window (2 s). In brief, variability in the organization of task-related networks seems to be a highly sensitive indicator of long-lasting training effects. This finding opens new methodological and theoretical windows to explore the impact of domain-specific expertise on brain plasticity, while highlighting variability as a fruitful measure in neuroimaging research.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Observing an action performed by another individual activates, in the observer, similar circuits as those involved in the actual execution of that action. This activation is modulated by prior experience; indeed, sustained training in a particular motor domain leads to structural and functional changes in critical brain areas. Here, we capitalized on a novel graph-theory approach to electroencephalographic data (Fraiman et al., 2016) to test whether variability in functional brain networks implicated in Tango observation can discriminate between groups differing in their level of expertise. We found that experts and beginners significantly differed in the functional organization of task-relevant networks. Specifically, networks in expert Tango dancers exhibited less variability and a more robust functional architecture. Notably, these expertise-dependent effects were captured within networks derived from electrophysiological brain activity recorded in a very short time window (2 s). In brief, variability in the organization of task-related networks seems to be a highly sensitive indicator of long-lasting training effects. This finding opens new methodological and theoretical windows to explore the impact of domain-specific expertise on brain plasticity, while highlighting variability as a fruitful measure in neuroimaging research. |
Jamila Andoh; Reiko Matsushita; Robert J Zatorre Asymmetric interhemispheric transfer in the auditory network: Evidence from TMS, resting-state fMRI, and diffusion imaging Journal Article Journal of Neuroscience, 43 (43), pp. 14602–14611, 2015. @article{Andoh2015, title = {Asymmetric interhemispheric transfer in the auditory network: Evidence from TMS, resting-state fMRI, and diffusion imaging}, author = {Jamila Andoh and Reiko Matsushita and Robert J Zatorre}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.2333-15.2015}, doi = {10.1523/JNEUROSCI.2333-15.2015}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neuroscience}, volume = {43}, number = {43}, pages = {14602--14611}, abstract = {Hemispheric asymmetries in human auditory cortical function and structure are still highly debated. Brain stimulation approaches can complement correlational techniques by uncovering causal influences. Previous studies have shown asymmetrical effects of transcranial magnetic stimulation (TMS) on task performance, but it is unclear whether these effects are task-specific or reflect intrinsic network properties. To test how modulation of auditory cortex (AC) influences functional networks and whether this influence is asymmetrical, the present study measured resting-state fMRI connectivity networks in 17 healthy volunteers before and immediately after TMS (continuous theta burst stimulation) to the left or right AC, and the vertex as a control. We also examined the relationship between TMS-induced interhemispheric signal propagation and anatomical properties of callosal auditory fibers as measured with diffusion-weighted MRI. We found that TMS to the right AC, but not the left, resulted in widespread connectivity decreases in auditory- and motor-related networks in the resting state. Individual differences in the degree of change in functional connectivity between auditory cortices after TMS applied over the right AC were negatively related to the volume of callosal auditory fibers. The findings show that TMS-induced network modulation occurs, even in the absence of an explicit task, and that the magnitude of the effect differs across individuals as a function of callosal structure, supporting a role for the corpus callosum in mediating functional asymmetry. The findings support theoretical models emphasizing hemispheric differences in network organization and are of practical significance in showing that brain stimulation studies need to take network-level effects into account.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hemispheric asymmetries in human auditory cortical function and structure are still highly debated. Brain stimulation approaches can complement correlational techniques by uncovering causal influences. Previous studies have shown asymmetrical effects of transcranial magnetic stimulation (TMS) on task performance, but it is unclear whether these effects are task-specific or reflect intrinsic network properties. To test how modulation of auditory cortex (AC) influences functional networks and whether this influence is asymmetrical, the present study measured resting-state fMRI connectivity networks in 17 healthy volunteers before and immediately after TMS (continuous theta burst stimulation) to the left or right AC, and the vertex as a control. We also examined the relationship between TMS-induced interhemispheric signal propagation and anatomical properties of callosal auditory fibers as measured with diffusion-weighted MRI. We found that TMS to the right AC, but not the left, resulted in widespread connectivity decreases in auditory- and motor-related networks in the resting state. Individual differences in the degree of change in functional connectivity between auditory cortices after TMS applied over the right AC were negatively related to the volume of callosal auditory fibers. The findings show that TMS-induced network modulation occurs, even in the absence of an explicit task, and that the magnitude of the effect differs across individuals as a function of callosal structure, supporting a role for the corpus callosum in mediating functional asymmetry. The findings support theoretical models emphasizing hemispheric differences in network organization and are of practical significance in showing that brain stimulation studies need to take network-level effects into account. |
Ayelet Arazi; Gil Gonen-Yaacovi; Ilan Dinstein The Magnitude of Trial-By-Trial Neural Variability Is Reproducible over Time and across Tasks in Humans Journal Article eNeuro, 4 (6), pp. ENEURO.0292–17.2017, 2017. @article{Arazi2017b, title = {The Magnitude of Trial-By-Trial Neural Variability Is Reproducible over Time and across Tasks in Humans}, author = {Ayelet Arazi and Gil Gonen-Yaacovi and Ilan Dinstein}, doi = {10.1523/ENEURO.0292-17.2017}, year = {2017}, date = {2017-01-01}, journal = {eNeuro}, volume = {4}, number = {6}, pages = {ENEURO.0292--17.2017}, abstract = {Numerous studies have shown that neural activity in sensory cortices is remarkably variable over time and across trials even when subjects are presented with an identical repeating stimulus or task. This trial-by-trial neural variability is relatively large in the prestimulus period and considerably smaller (quenched) following stimulus presentation. Previous studies have suggested that the magnitude of neural variability affects behavior such that perceptual performance is better on trials and in individuals where variability quenching is larger. To what degree are neural variability magnitudes of individual subjects flexible or static? Here, we used EEG recordings from adult humans to demonstrate that neural variability magnitudes in visual cortex are remarkably consistent across different tasks and recording sessions. While magnitudes of neural variability differed dramatically across individual subjects, they were surprisingly stable across four tasks with different stimuli, temporal structures, and attentional/cognitive demands as well as across experimental sessions separated by one year. These experiments reveal that, in adults, neural variability magnitudes are mostly solidified individual characteristics that change little with task or time, and are likely to predispose individual subjects to exhibit distinct behavioral capabilities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Numerous studies have shown that neural activity in sensory cortices is remarkably variable over time and across trials even when subjects are presented with an identical repeating stimulus or task. This trial-by-trial neural variability is relatively large in the prestimulus period and considerably smaller (quenched) following stimulus presentation. Previous studies have suggested that the magnitude of neural variability affects behavior such that perceptual performance is better on trials and in individuals where variability quenching is larger. To what degree are neural variability magnitudes of individual subjects flexible or static? Here, we used EEG recordings from adult humans to demonstrate that neural variability magnitudes in visual cortex are remarkably consistent across different tasks and recording sessions. While magnitudes of neural variability differed dramatically across individual subjects, they were surprisingly stable across four tasks with different stimuli, temporal structures, and attentional/cognitive demands as well as across experimental sessions separated by one year. These experiments reveal that, in adults, neural variability magnitudes are mostly solidified individual characteristics that change little with task or time, and are likely to predispose individual subjects to exhibit distinct behavioral capabilities. |
Ryszard Auksztulewicz; Karl Friston Attentional enhancement of auditory mismatch responses: A DCM/MEG study Journal Article Cerebral Cortex, 25 (11), pp. 4273–4283, 2015. @article{Auksztulewicz2015, title = {Attentional enhancement of auditory mismatch responses: A DCM/MEG study}, author = {Ryszard Auksztulewicz and Karl Friston}, doi = {10.1093/cercor/bhu323}, year = {2015}, date = {2015-01-01}, journal = {Cerebral Cortex}, volume = {25}, number = {11}, pages = {4273--4283}, abstract = {Despite similar behavioral effects, attention and expectation influence evoked responses differently: Attention typically enhances event-related responses, whereas expectation reduces them. This dissociation has been reconciled under predictive coding, where prediction errors are weighted by precision associated with attentional modulation. Here, we tested the predictive coding account of attention and expectation using magnetoencephalography and modeling. Temporal attention and sensory expectation were orthogonally manipulated in an auditory mismatch paradigm, revealing opposing effects on evoked response amplitude. Mismatch negativity (MMN) was enhanced by attention, speaking against its supposedly pre-attentive nature. This interaction effect was modeled in a canonical microcircuit using dynamic causal modeling, comparing models with modulation of extrinsic and intrinsic connectivity at different levels of the auditory hierarchy. While MMN was explained by recursive interplay of sensory predictions and prediction errors, attention was linked to the gain of inhibitory interneurons, consistent with its modulation of sensory precision.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Despite similar behavioral effects, attention and expectation influence evoked responses differently: Attention typically enhances event-related responses, whereas expectation reduces them. This dissociation has been reconciled under predictive coding, where prediction errors are weighted by precision associated with attentional modulation. Here, we tested the predictive coding account of attention and expectation using magnetoencephalography and modeling. Temporal attention and sensory expectation were orthogonally manipulated in an auditory mismatch paradigm, revealing opposing effects on evoked response amplitude. Mismatch negativity (MMN) was enhanced by attention, speaking against its supposedly pre-attentive nature. This interaction effect was modeled in a canonical microcircuit using dynamic causal modeling, comparing models with modulation of extrinsic and intrinsic connectivity at different levels of the auditory hierarchy. While MMN was explained by recursive interplay of sensory predictions and prediction errors, attention was linked to the gain of inhibitory interneurons, consistent with its modulation of sensory precision. |
Mariana Babo-Rebelo; Craig G Richter; Catherine Tallon-Baudry Neural responses to heartbeats in the default network encode the self in spontaneous thoughts Journal Article Journal of Neuroscience, 36 (30), pp. 7829–7840, 2016. @article{Babo-Rebelo2016, title = {Neural responses to heartbeats in the default network encode the self in spontaneous thoughts}, author = {Mariana Babo-Rebelo and Craig G Richter and Catherine Tallon-Baudry}, url = {http://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.0262-16.2016}, doi = {10.1523/JNEUROSCI.0262-16.2016}, year = {2016}, date = {2016-01-01}, journal = {Journal of Neuroscience}, volume = {36}, number = {30}, pages = {7829--7840}, abstract = {The default network (DN) has been consistently associated with self-related cognition, but also to bodily state monitoring and autonomic regulation. We hypothesized that these two seemingly disparate functional roles of the DN are functionally coupled, in line with theories proposing that selfhood is grounded in the neural monitoring of internal organs, such as the heart. We measured with magnetoencephalograhy neural responses evoked by heartbeats while human participants freely mind-wandered. When interrupted by a visual stimulus at random intervals, participants scored the self-relatedness of the interrupted thought. They evaluated their involvement as the first-person perspective subject or agent in the thought ("I"), and on another scale to what degree they were thinking about themselves ("Me"). During the interrupted thought, neural responses to heartbeats in two regions of the DN, the ventral precuneus and the ventromedial prefrontal cortex, covaried, respectively, with the "I" and the "Me" dimensions of the self, even at the single-trial level. No covariation between self-relatedness and peripheral autonomic measures (heart rate, heart rate variability, pupil diameter, electrodermal activity, respiration rate, and phase) or alpha power was observed. Our results reveal a direct link between selfhood and neural responses to heartbeats in the DN and thus directly support theories grounding selfhood in the neural monitoring of visceral inputs. More generally, the tight functional coupling between self-related processing and cardiac monitoring observed here implies that, even in the absence of measured changes in peripheral bodily measures, physiological and cognitive functions have to be considered jointly in the DN.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The default network (DN) has been consistently associated with self-related cognition, but also to bodily state monitoring and autonomic regulation. We hypothesized that these two seemingly disparate functional roles of the DN are functionally coupled, in line with theories proposing that selfhood is grounded in the neural monitoring of internal organs, such as the heart. We measured with magnetoencephalograhy neural responses evoked by heartbeats while human participants freely mind-wandered. When interrupted by a visual stimulus at random intervals, participants scored the self-relatedness of the interrupted thought. They evaluated their involvement as the first-person perspective subject or agent in the thought ("I"), and on another scale to what degree they were thinking about themselves ("Me"). During the interrupted thought, neural responses to heartbeats in two regions of the DN, the ventral precuneus and the ventromedial prefrontal cortex, covaried, respectively, with the "I" and the "Me" dimensions of the self, even at the single-trial level. No covariation between self-relatedness and peripheral autonomic measures (heart rate, heart rate variability, pupil diameter, electrodermal activity, respiration rate, and phase) or alpha power was observed. Our results reveal a direct link between selfhood and neural responses to heartbeats in the DN and thus directly support theories grounding selfhood in the neural monitoring of visceral inputs. More generally, the tight functional coupling between self-related processing and cardiac monitoring observed here implies that, even in the absence of measured changes in peripheral bodily measures, physiological and cognitive functions have to be considered jointly in the DN. |
Dominik R Bach; Nicholas Furl; Gareth Barnes; Raymond J Dolan Sustained magnetic responses in temporal cortex reflect instantaneous significance of approaching and receding sounds Journal Article PLoS ONE, 10 (7), pp. 1–13, 2015. @article{Bach2015, title = {Sustained magnetic responses in temporal cortex reflect instantaneous significance of approaching and receding sounds}, author = {Dominik R Bach and Nicholas Furl and Gareth Barnes and Raymond J Dolan}, doi = {10.1371/journal.pone.0134060}, year = {2015}, date = {2015-01-01}, journal = {PLoS ONE}, volume = {10}, number = {7}, pages = {1--13}, abstract = {Rising sound intensity often signals an approaching sound source and can serve as a powerful warning cue, eliciting phasic attention, perception biases and emotional responses. How the evaluation of approaching sounds unfolds over time remains elusive. Here, we capitalised on the temporal resolution of magnetoencephalograpy (MEG) to investigate in humans a dynamic encoding of perceiving approaching and receding sounds. We compared magnetic responses to intensity envelopes of complex sounds to those of white noise sounds, in which intensity change is not perceived as approaching. Sustained magnetic fields over temporal sensors tracked intensity change in complex sounds in an approximately linear fashion, an effect not seen for intensity change in white noise sounds, or for overall intensity. Hence, these fields are likely to track approach/recession, but not the apparent (instantaneous) distance of the sound source, or its intensity as such. As a likely source of this activity, the bilateral inferior temporal gyrus and right temporo-parietal junction emerged. Our results indicate that discrete temporal cortical areas parametrically encode behavioural significance in moving sound sources where the signal unfolded in a manner reminiscent of evidence accumulation. This may help an understanding of how acoustic percepts are evaluated as behaviourally relevant, where our results highlight a crucial role of cortical areas.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Rising sound intensity often signals an approaching sound source and can serve as a powerful warning cue, eliciting phasic attention, perception biases and emotional responses. How the evaluation of approaching sounds unfolds over time remains elusive. Here, we capitalised on the temporal resolution of magnetoencephalograpy (MEG) to investigate in humans a dynamic encoding of perceiving approaching and receding sounds. We compared magnetic responses to intensity envelopes of complex sounds to those of white noise sounds, in which intensity change is not perceived as approaching. Sustained magnetic fields over temporal sensors tracked intensity change in complex sounds in an approximately linear fashion, an effect not seen for intensity change in white noise sounds, or for overall intensity. Hence, these fields are likely to track approach/recession, but not the apparent (instantaneous) distance of the sound source, or its intensity as such. As a likely source of this activity, the bilateral inferior temporal gyrus and right temporo-parietal junction emerged. Our results indicate that discrete temporal cortical areas parametrically encode behavioural significance in moving sound sources where the signal unfolded in a manner reminiscent of evidence accumulation. This may help an understanding of how acoustic percepts are evaluated as behaviourally relevant, where our results highlight a crucial role of cortical areas. |
Cathleen Bache; Anne Springer; Hannes Noack; Waltraud Stadler; Franziska Kopp; Ulman Lindenberger; Markus Werkle-Bergner 10-month-old infants are sensitive to the time course of perceived actions: Eye-tracking and EEG evidence Journal Article Frontiers in Psychology, 8 , pp. 1–18, 2017. @article{Bache2017, title = {10-month-old infants are sensitive to the time course of perceived actions: Eye-tracking and EEG evidence}, author = {Cathleen Bache and Anne Springer and Hannes Noack and Waltraud Stadler and Franziska Kopp and Ulman Lindenberger and Markus Werkle-Bergner}, doi = {10.3389/fpsyg.2017.01170}, year = {2017}, date = {2017-01-01}, journal = {Frontiers in Psychology}, volume = {8}, pages = {1--18}, abstract = {Research has shown that infants are able to track a moving target efficiently – even if it is transiently occluded from sight. This basic ability allows prediction of when and where events happen in everyday life. Yet, it is unclear whether, and how, infants internally represent the time course of ongoing movements to derive predictions. In this study, 10-month-old crawlers observed the video of a same-aged crawling baby that was transiently occluded and reappeared in either a temporally continuous or non-continuous manner (i.e., delayed by 500 ms vs. forwarded by 500 ms relative to the real-time movement). Eye movement and rhythmic neural brain activity (EEG) were measured simultaneously. Eye movement analyses showed that infants were sensitive to slight temporal shifts in movement continuation after occlusion. Furthermore, brain activity associated with sensorimotor processing differed between observation of continuous and non-continuous movements. Early sensitivity to an action's timing may hence be explained within the internal real-time simulation account of action observation. Overall, the results support the hypothesis that 10-month-old infants are well prepared for internal representation of the time course of observed movements that are within the infants' current motor repertoire.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Research has shown that infants are able to track a moving target efficiently – even if it is transiently occluded from sight. This basic ability allows prediction of when and where events happen in everyday life. Yet, it is unclear whether, and how, infants internally represent the time course of ongoing movements to derive predictions. In this study, 10-month-old crawlers observed the video of a same-aged crawling baby that was transiently occluded and reappeared in either a temporally continuous or non-continuous manner (i.e., delayed by 500 ms vs. forwarded by 500 ms relative to the real-time movement). Eye movement and rhythmic neural brain activity (EEG) were measured simultaneously. Eye movement analyses showed that infants were sensitive to slight temporal shifts in movement continuation after occlusion. Furthermore, brain activity associated with sensorimotor processing differed between observation of continuous and non-continuous movements. Early sensitivity to an action's timing may hence be explained within the internal real-time simulation account of action observation. Overall, the results support the hypothesis that 10-month-old infants are well prepared for internal representation of the time course of observed movements that are within the infants' current motor repertoire. |
Daniel Baldauf; Robert Desimone Neural mechanisms of object-based attention Journal Article Science, 344 (6182), pp. 424–427, 2014. @article{Baldauf2014, title = {Neural mechanisms of object-based attention}, author = {Daniel Baldauf and Robert Desimone}, doi = {10.1126/science.1247003}, year = {2014}, date = {2014-01-01}, journal = {Science}, volume = {344}, number = {6182}, pages = {424--427}, abstract = {How we attend to objects and their features that cannot be separated by location is not understood. We presented two temporally and spatially overlapping streams of objects, faces versus houses, and used magnetoencephalography and functional magnetic resonance imaging to separate neuronal responses to attended and unattended objects. Attention to faces versus houses enhanced the sensory responses in the fusiform face area (FFA) and parahippocampal place area (PPA), respectively. The increases in sensory responses were accompanied by induced gamma synchrony between the inferior frontal junction, IFJ, and either FFA or PPA, depending on which object was attended. The IFJ appeared to be the driver of the synchrony, as gamma phases were advanced by 20 ms in IFJ compared to FFA or PPA. Thus, the IFJ may direct the flow of visual processing during object-based attention, at least in part through coupled oscillations with specialized areas such as FFA and PPA. W}, keywords = {}, pubstate = {published}, tppubtype = {article} } How we attend to objects and their features that cannot be separated by location is not understood. We presented two temporally and spatially overlapping streams of objects, faces versus houses, and used magnetoencephalography and functional magnetic resonance imaging to separate neuronal responses to attended and unattended objects. Attention to faces versus houses enhanced the sensory responses in the fusiform face area (FFA) and parahippocampal place area (PPA), respectively. The increases in sensory responses were accompanied by induced gamma synchrony between the inferior frontal junction, IFJ, and either FFA or PPA, depending on which object was attended. The IFJ appeared to be the driver of the synchrony, as gamma phases were advanced by 20 ms in IFJ compared to FFA or PPA. Thus, the IFJ may direct the flow of visual processing during object-based attention, at least in part through coupled oscillations with specialized areas such as FFA and PPA. W |
Snigdha Banerjee; Adam C Snyder; Sophie Molholm; John J Foxe Journal of Neuroscience, 31 (27), pp. 9923–9932, 2011. @article{Banerjee2011, title = {Oscillatory alpha-band mechanisms and the deployment of spatial attention to anticipated auditory and visual target locations: Supramodal or sensory-specific control mechanisms?}, author = {Snigdha Banerjee and Adam C Snyder and Sophie Molholm and John J Foxe}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.4660-10.2011}, doi = {10.1523/JNEUROSCI.4660-10.2011}, year = {2011}, date = {2011-01-01}, journal = {Journal of Neuroscience}, volume = {31}, number = {27}, pages = {9923--9932}, abstract = {Oscillatory alpha-band activity (8-15 Hz) over parieto-occipital cortex in humans plays an important role in suppression of processing for inputs at to-be-ignored regions of space, with increased alpha-band power observed over cortex contralateral to locations expected to contain distractors. It is unclear whether similar processes operate during deployment of spatial attention in other sensory modalities. Evidence from lesion patients suggests that parietal regions house supramodal representations of space. The parietal lobes are prominent generators of alpha oscillations, raising the possibility that alpha is a neural signature of supramodal spatial attention. Furthermore, when spatial attention is deployed within vision, processing of task-irrelevant auditory inputs at attended locations is also enhanced, pointing to automatic links between spatial deployments across senses. Here, we asked whether lateralized alpha-band activity is also evident in a purely auditory spatial-cueing task and whether it had the same underlying generator configuration as in a purely visuospatial task. If common to both sensory systems, this would provide strong support for "supramodal" attention theory. Alternately, alpha-band differences between auditory and visual tasks would support a sensory-specific account. Lateralized shifts in alpha-band activity were indeed observed during a purely auditory spatial task. Crucially, there were clear differences in scalp topographies of this alpha activity depending on the sensory system within which spatial attention was deployed. Findings suggest that parietally generated alpha-band mechanisms are central to attentional deployments across modalities but that they are invoked in a sensory-specific manner. The data support an "interactivity account," whereby a supramodal system interacts with sensory-specific control systems during deployment of spatial attention.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Oscillatory alpha-band activity (8-15 Hz) over parieto-occipital cortex in humans plays an important role in suppression of processing for inputs at to-be-ignored regions of space, with increased alpha-band power observed over cortex contralateral to locations expected to contain distractors. It is unclear whether similar processes operate during deployment of spatial attention in other sensory modalities. Evidence from lesion patients suggests that parietal regions house supramodal representations of space. The parietal lobes are prominent generators of alpha oscillations, raising the possibility that alpha is a neural signature of supramodal spatial attention. Furthermore, when spatial attention is deployed within vision, processing of task-irrelevant auditory inputs at attended locations is also enhanced, pointing to automatic links between spatial deployments across senses. Here, we asked whether lateralized alpha-band activity is also evident in a purely auditory spatial-cueing task and whether it had the same underlying generator configuration as in a purely visuospatial task. If common to both sensory systems, this would provide strong support for "supramodal" attention theory. Alternately, alpha-band differences between auditory and visual tasks would support a sensory-specific account. Lateralized shifts in alpha-band activity were indeed observed during a purely auditory spatial task. Crucially, there were clear differences in scalp topographies of this alpha activity depending on the sensory system within which spatial attention was deployed. Findings suggest that parietally generated alpha-band mechanisms are central to attentional deployments across modalities but that they are invoked in a sensory-specific manner. The data support an "interactivity account," whereby a supramodal system interacts with sensory-specific control systems during deployment of spatial attention. |
Snigdha Banerjee; Hans Peter Frey; Sophie Molholm; John J Foxe European Journal of Neuroscience, 41 (6), pp. 818–834, 2015. @article{Banerjee2015, title = {Interests shape how adolescents pay attention: The interaction of motivation and top-down attentional processes in biasing sensory activations to anticipated events}, author = {Snigdha Banerjee and Hans Peter Frey and Sophie Molholm and John J Foxe}, doi = {10.1111/ejn.12810}, year = {2015}, date = {2015-01-01}, journal = {European Journal of Neuroscience}, volume = {41}, number = {6}, pages = {818--834}, abstract = {The voluntary allocation of attention to environmental inputs is a crucial mechanism of healthy cognitive functioning, and is probably influenced by an observer's level of interest in a stimulus. For example, an individual who is passionate about soccer but bored by botany will obviously be more attentive at a soccer match than an orchid show. The influence of monetary rewards on attention has been examined, but the impact of more common motivating factors (i.e. the level of interest in the materials under observation) remains unclear, especially during development. Here, stimulus sets were designed based on survey measures of the level of interest of adolescent participants in several item classes. High-density electroencephalography was recorded during a cued spatial attention task in which stimuli of high or low interest were presented in separate blocks. The motivational impact on performance of a spatial attention task was assessed, along with event-related potential measures of anticipatory top-down attention. As predicted, performance was improved for the spatial target detection of high interest items. Further, the impact of motivation was observed in parieto-occipital processes associated with anticipatory top-down spatial attention. The anticipatory activity over these regions was also increased for high vs. low interest stimuli, irrespective of the direction of spatial attention. The results also showed stronger anticipatory attentional and motivational modulations over the right vs. left parieto-occipital cortex. These data suggest that motivation enhances top-down attentional processes, and can independently shape activations in sensory regions in anticipation of events. They also suggest that attentional functions across hemispheres may not fully mature until late adolescence.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The voluntary allocation of attention to environmental inputs is a crucial mechanism of healthy cognitive functioning, and is probably influenced by an observer's level of interest in a stimulus. For example, an individual who is passionate about soccer but bored by botany will obviously be more attentive at a soccer match than an orchid show. The influence of monetary rewards on attention has been examined, but the impact of more common motivating factors (i.e. the level of interest in the materials under observation) remains unclear, especially during development. Here, stimulus sets were designed based on survey measures of the level of interest of adolescent participants in several item classes. High-density electroencephalography was recorded during a cued spatial attention task in which stimuli of high or low interest were presented in separate blocks. The motivational impact on performance of a spatial attention task was assessed, along with event-related potential measures of anticipatory top-down attention. As predicted, performance was improved for the spatial target detection of high interest items. Further, the impact of motivation was observed in parieto-occipital processes associated with anticipatory top-down spatial attention. The anticipatory activity over these regions was also increased for high vs. low interest stimuli, irrespective of the direction of spatial attention. The results also showed stronger anticipatory attentional and motivational modulations over the right vs. left parieto-occipital cortex. These data suggest that motivation enhances top-down attentional processes, and can independently shape activations in sensory regions in anticipation of events. They also suggest that attentional functions across hemispheres may not fully mature until late adolescence. |
Mareike Bayer; Valentina Rossi; Naomi Vanlessen; Annika Grass; Annekathrin Schacht; Gilles Pourtois Independent effects of motivation and spatial attention in the human visual cortex Journal Article Social Cognitive and Affective Neuroscience, 12 (1), pp. 146–156, 2017. @article{Bayer2017a, title = {Independent effects of motivation and spatial attention in the human visual cortex}, author = {Mareike Bayer and Valentina Rossi and Naomi Vanlessen and Annika Grass and Annekathrin Schacht and Gilles Pourtois}, doi = {10.1093/scan/nsw162}, year = {2017}, date = {2017-01-01}, journal = {Social Cognitive and Affective Neuroscience}, volume = {12}, number = {1}, pages = {146--156}, abstract = {Motivation and attention constitute major determinants of human perception and action. Nonetheless, it remains a matter of debate whether motivation effects on the visual cortex depend on the spatial attention system, or rely on independent pathways. This study investigated the impact of motivation and spatial attention on the activity of the human primary and extrastriate visual cortex by employing a factorial manipulation of the two factors in a cued pattern discrimination task. During stimulus presentation, we recorded event-related potentials and pupillary responses. Motivational relevance increased the amplitudes of the C1 component at ∼70 ms after stimulus onset. This modulation occurred independently of spatial attention effects, which were evident at the P1 level. Furthermore, motivation and spatial attention had independent effects on preparatory activation as measured by the contingent negative variation; and pupil data showed increased activation in response to incentive targets. Taken together, these findings suggest independent pathways for the influence of motivation and spatial attention on the activity of the human visual cortex.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Motivation and attention constitute major determinants of human perception and action. Nonetheless, it remains a matter of debate whether motivation effects on the visual cortex depend on the spatial attention system, or rely on independent pathways. This study investigated the impact of motivation and spatial attention on the activity of the human primary and extrastriate visual cortex by employing a factorial manipulation of the two factors in a cued pattern discrimination task. During stimulus presentation, we recorded event-related potentials and pupillary responses. Motivational relevance increased the amplitudes of the C1 component at ∼70 ms after stimulus onset. This modulation occurred independently of spatial attention effects, which were evident at the P1 level. Furthermore, motivation and spatial attention had independent effects on preparatory activation as measured by the contingent negative variation; and pupil data showed increased activation in response to incentive targets. Taken together, these findings suggest independent pathways for the influence of motivation and spatial attention on the activity of the human visual cortex. |
Mareike Bayer; Katja Ruthmann; Annekathrin Schacht The impact of personal relevance on emotion processing: Evidence from event-related potentials and pupillary responses Journal Article Social Cognitive and Affective Neuroscience, 12 (9), pp. 1470–1479, 2017. @article{Bayer2017b, title = {The impact of personal relevance on emotion processing: Evidence from event-related potentials and pupillary responses}, author = {Mareike Bayer and Katja Ruthmann and Annekathrin Schacht}, doi = {10.1093/scan/nsx075}, year = {2017}, date = {2017-01-01}, journal = {Social Cognitive and Affective Neuroscience}, volume = {12}, number = {9}, pages = {1470--1479}, abstract = {Emotional stimuli attract attention and lead to increased activity in the visual cortex. The present study investigated the impact of personal relevance on emotion processing by presenting emotional words within sentences that referred to participants' significant others or to unknown agents. In event-related potentials, personal relevance increased visual cortex activity within 100 ms after stimulus onset and the amplitudes of the Late Positive Complex (LPC). Moreover, personally relevant contexts gave rise to augmented pupillary responses and higher arousal ratings, suggesting a general boost of attention and arousal. Finally, personal relevance increased emotion-related ERP effects starting around 200 ms after word onset; effects for negative words compared to neutral words were prolonged in duration. Source localizations of these interactions revealed activations in prefrontal regions, in the visual cortex and in the fusiform gyrus. Taken together, these results demonstrate the high impact of personal relevance on reading in general and on emotion processing in particular.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Emotional stimuli attract attention and lead to increased activity in the visual cortex. The present study investigated the impact of personal relevance on emotion processing by presenting emotional words within sentences that referred to participants' significant others or to unknown agents. In event-related potentials, personal relevance increased visual cortex activity within 100 ms after stimulus onset and the amplitudes of the Late Positive Complex (LPC). Moreover, personally relevant contexts gave rise to augmented pupillary responses and higher arousal ratings, suggesting a general boost of attention and arousal. Finally, personal relevance increased emotion-related ERP effects starting around 200 ms after word onset; effects for negative words compared to neutral words were prolonged in duration. Source localizations of these interactions revealed activations in prefrontal regions, in the visual cortex and in the fusiform gyrus. Taken together, these results demonstrate the high impact of personal relevance on reading in general and on emotion processing in particular. |
Brett C Bays; Kristina M Visscher; Christophe C Le Dantec; Aaron R Seitz Alpha-band EEG activity in perceptual learning Journal Article Journal of Vision, 15 (10), pp. 1–12, 2015. @article{Bays2015, title = {Alpha-band EEG activity in perceptual learning}, author = {Brett C Bays and Kristina M Visscher and Christophe C {Le Dantec} and Aaron R Seitz}, url = {http://jov.arvojournals.org/article.aspx?doi=10.1167/15.10.7}, doi = {10.1167/15.10.7}, year = {2015}, date = {2015-01-01}, journal = {Journal of Vision}, volume = {15}, number = {10}, pages = {1--12}, abstract = {In studies of perceptual learning (PL), subjects are typically highly trained across many sessions to achieve perceptual benefits on the stimuli in those tasks. There is currently significant debate regarding what sources of brain plasticity underlie these PL-based learning improvements. Here we investigate the hypothesis that PL, among other mechanisms, leads to task automaticity, especially in the presence of the trained stimuli. To investigate this hypothesis, we trained participants for eight sessions to find an oriented target in a field of near-oriented distractors and examined alpha-band activity, which modulates with attention to visual stimuli, as a possible measure of automaticity. Alpha-band activity was acquired via electroencephalogram (EEG), before and after training, as participants performed the task with trained and untrained stimuli. Results show that participants underwent significant learning in this task (as assessed by threshold, accuracy, and reaction time improvements) and that alpha power increased during the pre-stimulus period and then underwent greater desynchronization at the time of stimulus presentation following training. However, these changes in alpha-band activity were not specific to the trained stimuli, with similar patterns of posttraining alpha power for trained and untrained stimuli. These data are consistent with the view that participants were more efficient at focusing resources at the time of stimulus presentation and are consistent with a greater automaticity of task performance. These findings have implications for PL, as transfer effects from trained to untrained stimuli may partially depend on differential effort of the individual at the time of stimulus processing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In studies of perceptual learning (PL), subjects are typically highly trained across many sessions to achieve perceptual benefits on the stimuli in those tasks. There is currently significant debate regarding what sources of brain plasticity underlie these PL-based learning improvements. Here we investigate the hypothesis that PL, among other mechanisms, leads to task automaticity, especially in the presence of the trained stimuli. To investigate this hypothesis, we trained participants for eight sessions to find an oriented target in a field of near-oriented distractors and examined alpha-band activity, which modulates with attention to visual stimuli, as a possible measure of automaticity. Alpha-band activity was acquired via electroencephalogram (EEG), before and after training, as participants performed the task with trained and untrained stimuli. Results show that participants underwent significant learning in this task (as assessed by threshold, accuracy, and reaction time improvements) and that alpha power increased during the pre-stimulus period and then underwent greater desynchronization at the time of stimulus presentation following training. However, these changes in alpha-band activity were not specific to the trained stimuli, with similar patterns of posttraining alpha power for trained and untrained stimuli. These data are consistent with the view that participants were more efficient at focusing resources at the time of stimulus presentation and are consistent with a greater automaticity of task performance. These findings have implications for PL, as transfer effects from trained to untrained stimuli may partially depend on differential effort of the individual at the time of stimulus processing. |
Jeffrey S Bedwell; Christopher C Spencer; Chi C Chan; Pamela D Butler; Pejman Sehatpour; Joseph Schmidt The P1 visual-evoked potential, red light, and transdiagnostic psychiatric symptoms Journal Article Brain Research, 1687 , pp. 144–154, 2018. @article{Bedwell2018, title = {The P1 visual-evoked potential, red light, and transdiagnostic psychiatric symptoms}, author = {Jeffrey S Bedwell and Christopher C Spencer and Chi C Chan and Pamela D Butler and Pejman Sehatpour and Joseph Schmidt}, doi = {10.1016/j.brainres.2018.03.002}, year = {2018}, date = {2018-01-01}, journal = {Brain Research}, volume = {1687}, pages = {144--154}, publisher = {Elsevier B.V.}, abstract = {A reduced P1 visual-evoked potential amplitude has been reported across several psychiatric disorders, including schizophrenia-spectrum, bipolar, and depressive disorders. In addition, a difference in P1 amplitude change to a red background compared to its opponent color, green, has been found in schizophrenia-spectrum samples. The current study examined whether specific psychiatric symptoms that related to these P1 abnormalities in earlier studies would be replicated when using a broad transdiagnostic sample. The final sample consisted of 135 participants: 26 with bipolar disorders, 25 with schizophrenia-spectrum disorders, 19 with unipolar depression, 62 with no current psychiatric disorder, and 3 with disorders in other categories. Low (8%) and high (64%) contrast check arrays were presented on gray, green, and red background conditions during electroencephalogram, while an eye tracker monitored visual fixation on the stimuli. Linear regressions across the entire sample (N = 135) found that greater severity of both clinician-rated and self-reported delusions/magical thinking correlated with a reduced P1 amplitude on the low contrast gray (neutral) background condition. In addition, across the entire sample, higher self-reported constricted affect was associated with a larger decrease in P1 amplitude (averaged across contrast conditions) to the red, compared to green, background. All relationships remained statistically significant after covarying for diagnostic class, suggesting that they are relatively transdiagnostic in nature. These findings indicate that early visual processing abnormalities may be more directly related to specific transdiagnostic symptoms such as delusions and constricted affect rather than specific psychiatric diagnoses or broad symptom factor scales.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A reduced P1 visual-evoked potential amplitude has been reported across several psychiatric disorders, including schizophrenia-spectrum, bipolar, and depressive disorders. In addition, a difference in P1 amplitude change to a red background compared to its opponent color, green, has been found in schizophrenia-spectrum samples. The current study examined whether specific psychiatric symptoms that related to these P1 abnormalities in earlier studies would be replicated when using a broad transdiagnostic sample. The final sample consisted of 135 participants: 26 with bipolar disorders, 25 with schizophrenia-spectrum disorders, 19 with unipolar depression, 62 with no current psychiatric disorder, and 3 with disorders in other categories. Low (8%) and high (64%) contrast check arrays were presented on gray, green, and red background conditions during electroencephalogram, while an eye tracker monitored visual fixation on the stimuli. Linear regressions across the entire sample (N = 135) found that greater severity of both clinician-rated and self-reported delusions/magical thinking correlated with a reduced P1 amplitude on the low contrast gray (neutral) background condition. In addition, across the entire sample, higher self-reported constricted affect was associated with a larger decrease in P1 amplitude (averaged across contrast conditions) to the red, compared to green, background. All relationships remained statistically significant after covarying for diagnostic class, suggesting that they are relatively transdiagnostic in nature. These findings indicate that early visual processing abnormalities may be more directly related to specific transdiagnostic symptoms such as delusions and constricted affect rather than specific psychiatric diagnoses or broad symptom factor scales. |
Christian Bellebaum; Klaus-Peter Hoffmann; Irene Daum Post-saccadic updating of visual space in the posterior parietal cortex in humans Journal Article Behavioural Brain Research, 163 (2), pp. 194–203, 2005. @article{Bellebaum2005a, title = {Post-saccadic updating of visual space in the posterior parietal cortex in humans}, author = {Christian Bellebaum and Klaus-Peter Hoffmann and Irene Daum}, doi = {10.1016/j.bbr.2005.05.007}, year = {2005}, date = {2005-01-01}, journal = {Behavioural Brain Research}, volume = {163}, number = {2}, pages = {194--203}, abstract = {Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate. In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step task to elucidate the time course of the updating process. In the experimental condition updating of visual space was required, because both saccade targets had already disappeared before the first saccade was executed. A similar task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150 and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude that extraretinal information about the first saccade is integrated with motor information about the second saccade in the inter-saccade interval.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate. In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step task to elucidate the time course of the updating process. In the experimental condition updating of visual space was required, because both saccade targets had already disappeared before the first saccade was executed. A similar task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150 and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude that extraretinal information about the first saccade is integrated with motor information about the second saccade in the inter-saccade interval. |
Daniel Belyusar; Adam C Snyder; Hans Peter Frey; Mark R Harwood; Josh Wallman; John J Foxe Oscillatory alpha-band suppression mechanisms during the rapid attentional shifts required to perform an anti-saccade task Journal Article NeuroImage, 65 , pp. 395–407, 2013. @article{Belyusar2013, title = {Oscillatory alpha-band suppression mechanisms during the rapid attentional shifts required to perform an anti-saccade task}, author = {Daniel Belyusar and Adam C Snyder and Hans Peter Frey and Mark R Harwood and Josh Wallman and John J Foxe}, doi = {10.1016/j.neuroimage.2012.09.061}, year = {2013}, date = {2013-01-01}, journal = {NeuroImage}, volume = {65}, pages = {395--407}, abstract = {Neuroimaging has demonstrated anatomical overlap between covert and overt attention systems, although behavioral and electrophysiological studies have suggested that the two systems do not rely on entirely identical circuits or mechanisms. In a parallel line of research, topographically-specific modulations of alpha-band power (~. 8-14. Hz) have been consistently correlated with anticipatory states during tasks requiring covert attention shifts. These tasks, however, typically employ cue-target-interval paradigms where attentional processes are examined across relatively protracted periods of time and not at the rapid timescales implicated during overt attention tasks. The anti-saccade task, where one must first covertly attend for a peripheral target, before executing a rapid overt attention shift (i.e. a saccade) to the opposite side of space, is particularly well-suited for examining the rapid dynamics of overt attentional deployments. Here, we asked whether alpha-band oscillatory mechanisms would also be associated with these very rapid overt shifts, potentially representing a common neural mechanism across overt and covert attention systems. High-density electroencephalography in conjunction with infra-red eye-tracking was recorded while participants engaged in both pro- and anti-saccade task blocks. Alpha power, time-locked to saccade onset, showed three distinct phases of significantly lateralized topographic shifts, all occurring within a period of less than 1. s, closely reflecting the temporal dynamics of anti-saccade performance. Only two such phases were observed during the pro-saccade task. These data point to substantially more rapid temporal dynamics of alpha-band suppressive mechanisms than previously established, and implicate oscillatory alpha-band activity as a common mechanism across both overt and covert attentional deployments.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Neuroimaging has demonstrated anatomical overlap between covert and overt attention systems, although behavioral and electrophysiological studies have suggested that the two systems do not rely on entirely identical circuits or mechanisms. In a parallel line of research, topographically-specific modulations of alpha-band power (~. 8-14. Hz) have been consistently correlated with anticipatory states during tasks requiring covert attention shifts. These tasks, however, typically employ cue-target-interval paradigms where attentional processes are examined across relatively protracted periods of time and not at the rapid timescales implicated during overt attention tasks. The anti-saccade task, where one must first covertly attend for a peripheral target, before executing a rapid overt attention shift (i.e. a saccade) to the opposite side of space, is particularly well-suited for examining the rapid dynamics of overt attentional deployments. Here, we asked whether alpha-band oscillatory mechanisms would also be associated with these very rapid overt shifts, potentially representing a common neural mechanism across overt and covert attention systems. High-density electroencephalography in conjunction with infra-red eye-tracking was recorded while participants engaged in both pro- and anti-saccade task blocks. Alpha power, time-locked to saccade onset, showed three distinct phases of significantly lateralized topographic shifts, all occurring within a period of less than 1. s, closely reflecting the temporal dynamics of anti-saccade performance. Only two such phases were observed during the pro-saccade task. These data point to substantially more rapid temporal dynamics of alpha-band suppressive mechanisms than previously established, and implicate oscillatory alpha-band activity as a common mechanism across both overt and covert attentional deployments. |
Lysianne Beynel; Alan Chauvin; Nathalie Guyader; Sylvain Harquel; Thierry Bougerol; Christian Marendaz; David Szekely What saccadic eye movements tell us about TMS-induced neuromodulation of the DLPFC and mood changes: A pilot study in bipolar disorders Journal Article Frontiers in Integrative Neuroscience, 8 , pp. 1–8, 2014. @article{Beynel2014, title = {What saccadic eye movements tell us about TMS-induced neuromodulation of the DLPFC and mood changes: A pilot study in bipolar disorders}, author = {Lysianne Beynel and Alan Chauvin and Nathalie Guyader and Sylvain Harquel and Thierry Bougerol and Christian Marendaz and David Szekely}, doi = {10.3389/fnint.2014.00065}, year = {2014}, date = {2014-01-01}, journal = {Frontiers in Integrative Neuroscience}, volume = {8}, pages = {1--8}, abstract = {The study assumed that the antisaccade (AS) task is a relevant psychophysical tool to assess (i) short-term neuromodulation of the dorsolateral prefrontal cortex (DLPFC) induced by intermittent theta burst stimulation (iTBS); and (ii) mood change occurring during the course of the treatment. Saccadic inhibition is known to strongly involve the DLPFC, whose neuromodulation with iTBS requires less stimulation time and lower stimulation intensity, as well as results in longer aftereffects than the conventional repetitive transcranial magnetic stimulation (rTMS). Active or sham iTBS was applied every day for 3 weeks over the left DLPFC of 12 drug-resistant bipolar depressed patients. To assess the iTBS-induced short-term neuromodulation, the saccadic task was performed just before (S1) and just after (S2) the iTBS session, the first day of each week. Mood was evaluated through Montgomery and Asberg Depression Rating Scale (MADRS) scores and the difference in scores between the beginning and the end of treatment was correlated with AS performance change between these two periods. As expected, only patients from the active group improved their performance from S1 to S2 and mood improvement was significantly correlated with AS performance improvement. In addition, the AS task also discriminated depressive bipolar patients from healthy control subjects. Therefore, the AS task could be a relevant and useful tool for clinicians to assess if the Transcranial magnetic stimulation (TMS)-induced short-term neuromodulation of the DLPFC occurs as well as a “trait vs. state” objective marker of depressive mood disorder.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The study assumed that the antisaccade (AS) task is a relevant psychophysical tool to assess (i) short-term neuromodulation of the dorsolateral prefrontal cortex (DLPFC) induced by intermittent theta burst stimulation (iTBS); and (ii) mood change occurring during the course of the treatment. Saccadic inhibition is known to strongly involve the DLPFC, whose neuromodulation with iTBS requires less stimulation time and lower stimulation intensity, as well as results in longer aftereffects than the conventional repetitive transcranial magnetic stimulation (rTMS). Active or sham iTBS was applied every day for 3 weeks over the left DLPFC of 12 drug-resistant bipolar depressed patients. To assess the iTBS-induced short-term neuromodulation, the saccadic task was performed just before (S1) and just after (S2) the iTBS session, the first day of each week. Mood was evaluated through Montgomery and Asberg Depression Rating Scale (MADRS) scores and the difference in scores between the beginning and the end of treatment was correlated with AS performance change between these two periods. As expected, only patients from the active group improved their performance from S1 to S2 and mood improvement was significantly correlated with AS performance improvement. In addition, the AS task also discriminated depressive bipolar patients from healthy control subjects. Therefore, the AS task could be a relevant and useful tool for clinicians to assess if the Transcranial magnetic stimulation (TMS)-induced short-term neuromodulation of the DLPFC occurs as well as a “trait vs. state” objective marker of depressive mood disorder. |
Annabelle Blangero; Simon P Kelly Neural signature of value-based sensorimotor prioritization in humans Journal Article Journal of Neuroscience, 37 (44), pp. 10725–10737, 2017. @article{Blangero2017, title = {Neural signature of value-based sensorimotor prioritization in humans}, author = {Annabelle Blangero and Simon P Kelly}, doi = {10.1523/JNEUROSCI.1164-17.2017}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neuroscience}, volume = {37}, number = {44}, pages = {10725--10737}, abstract = {In situations in which impending sensory events demand fast action choices, we must be ready to prioritize higher-value courses of action to avoid missed opportunities. When such a situation first presents itself, stimulus-action contingencies and their relative value must be encoded to establish a value-biased state of preparation for an impending sensorimotor decision. Here, we sought to identify neurophysiological signatures of such processes in the human brain (both female and male). We devised a task requiring fast action choices based on the discrimination of a simple visual cue in which the differently valued sensory alternatives were presented 750-800 ms before as peripheral "targets" that specified the stimulus-action mapping for the upcoming decision. In response to the targets, we identified a discrete, transient, spatially selective signal in the event-related potential (ERP), which scaled with relative value and strongly predicted the degree of behavioral bias in the upcoming decision both across and within subjects. This signal is not compatible with any hitherto known ERP signature of spatial selection and also bears novel distinctions with respect to characterizations of value-sensitive, spatially selective activity found in sensorimotor areas of nonhuman primates. Specifically, a series of follow-up experiments revealed that the signal was reliably invoked regardless of response laterality, response modality, sensory feature, and reward valence. It was absent, however, when the response deadline was relaxed and the strategic need for biasing removed. Therefore, more than passively representing value or salience, the signal appears to play a versatile and active role in adaptive sensorimotor prioritization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In situations in which impending sensory events demand fast action choices, we must be ready to prioritize higher-value courses of action to avoid missed opportunities. When such a situation first presents itself, stimulus-action contingencies and their relative value must be encoded to establish a value-biased state of preparation for an impending sensorimotor decision. Here, we sought to identify neurophysiological signatures of such processes in the human brain (both female and male). We devised a task requiring fast action choices based on the discrimination of a simple visual cue in which the differently valued sensory alternatives were presented 750-800 ms before as peripheral "targets" that specified the stimulus-action mapping for the upcoming decision. In response to the targets, we identified a discrete, transient, spatially selective signal in the event-related potential (ERP), which scaled with relative value and strongly predicted the degree of behavioral bias in the upcoming decision both across and within subjects. This signal is not compatible with any hitherto known ERP signature of spatial selection and also bears novel distinctions with respect to characterizations of value-sensitive, spatially selective activity found in sensorimotor areas of nonhuman primates. Specifically, a series of follow-up experiments revealed that the signal was reliably invoked regardless of response laterality, response modality, sensory feature, and reward valence. It was absent, however, when the response deadline was relaxed and the strategic need for biasing removed. Therefore, more than passively representing value or salience, the signal appears to play a versatile and active role in adaptive sensorimotor prioritization. |
Indu P Bodala; Junhua Li; Nitish V Thakor; Hasan Al-Nashash EEG and eye tracking demonstrate vigilance enhancement with challenge integration Journal Article Frontiers in Human Neuroscience, 10 , pp. 1–12, 2016. @article{Bodala2016, title = {EEG and eye tracking demonstrate vigilance enhancement with challenge integration}, author = {Indu P Bodala and Junhua Li and Nitish V Thakor and Hasan Al-Nashash}, url = {http://journal.frontiersin.org/Article/10.3389/fnhum.2016.00273/abstract}, doi = {10.3389/fnhum.2016.00273}, year = {2016}, date = {2016-01-01}, journal = {Frontiers in Human Neuroscience}, volume = {10}, pages = {1--12}, abstract = {Maintaining vigilance is possibly the first requirement for surveillance tasks where personnel are faced with monotonous yet intensive monitoring tasks. Decrement in vigilance in such situations could result in dangerous consequences such as accidents, loss of life and system failure. In this paper, we investigate the possibility to enhance vigilance or sustained attention using ‘challenge integration', a strategy that integrates a primary task with challenging stimuli. A primary surveillance task (identifying an intruder in a simulated factory environment) and a challenge stimulus (periods of rain obscuring the surveillance scene) were employed to test the changes in vigilance levels. The effect of integrating challenging events (resulting from artificially simulated rain) into the task were compared to the initial monotonous phase. EEG and eye tracking data is collected and analyzed for n = 12 subjects. Frontal midline theta power and frontal theta to parietal alpha power ratio which are used as measures of engagement and attention allocation show an increase due to challenge integration (p textless 0.05 in each case). Relative delta band power of EEG also shows statistically significant suppression on the frontoparietal and occipital cortices due to challenge integration (p textless 0.05). Saccade amplitude, saccade velocity and blink rate obtained from eye tracking data exhibit statistically significant changes during the challenge phase of the experiment (p textless 0.05 in each case). From the correlation analysis between the statistically significant measures of eye tracking and EEG, we infer that saccade amplitude and saccade velocity decrease with vigilance decrement along with frontal midline theta and frontal theta to parietal alpha ratio. Conversely, blink rate and relative delta power increase with vigilance decrement. However, these measures exhibit a reverse trend when challenge stimulus appears in the task suggesting vigilance enhancement. Moreover, the mean reaction time is lower for the challenge integrated phase (RT mean = 3.65 ± 1.4 secs) compared to initial monotonous phase without challenge (RT mean = 4.6 ± 2.7 secs). Our work shows that vigilance level, as assessed by response of these vital signs, is enhanced by challenge integration.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Maintaining vigilance is possibly the first requirement for surveillance tasks where personnel are faced with monotonous yet intensive monitoring tasks. Decrement in vigilance in such situations could result in dangerous consequences such as accidents, loss of life and system failure. In this paper, we investigate the possibility to enhance vigilance or sustained attention using ‘challenge integration', a strategy that integrates a primary task with challenging stimuli. A primary surveillance task (identifying an intruder in a simulated factory environment) and a challenge stimulus (periods of rain obscuring the surveillance scene) were employed to test the changes in vigilance levels. The effect of integrating challenging events (resulting from artificially simulated rain) into the task were compared to the initial monotonous phase. EEG and eye tracking data is collected and analyzed for n = 12 subjects. Frontal midline theta power and frontal theta to parietal alpha power ratio which are used as measures of engagement and attention allocation show an increase due to challenge integration (p textless 0.05 in each case). Relative delta band power of EEG also shows statistically significant suppression on the frontoparietal and occipital cortices due to challenge integration (p textless 0.05). Saccade amplitude, saccade velocity and blink rate obtained from eye tracking data exhibit statistically significant changes during the challenge phase of the experiment (p textless 0.05 in each case). From the correlation analysis between the statistically significant measures of eye tracking and EEG, we infer that saccade amplitude and saccade velocity decrease with vigilance decrement along with frontal midline theta and frontal theta to parietal alpha ratio. Conversely, blink rate and relative delta power increase with vigilance decrement. However, these measures exhibit a reverse trend when challenge stimulus appears in the task suggesting vigilance enhancement. Moreover, the mean reaction time is lower for the challenge integrated phase (RT mean = 3.65 ± 1.4 secs) compared to initial monotonous phase without challenge (RT mean = 4.6 ± 2.7 secs). Our work shows that vigilance level, as assessed by response of these vital signs, is enhanced by challenge integration. |
Adam Borowicz Using a multichannel Wiener filter to remove eye-blink artifacts from EEG data Journal Article Biomedical Signal Processing and Control, 45 , pp. 246–255, 2018. @article{Borowicz2018, title = {Using a multichannel Wiener filter to remove eye-blink artifacts from EEG data}, author = {Adam Borowicz}, doi = {10.1016/j.bspc.2018.05.012}, year = {2018}, date = {2018-01-01}, journal = {Biomedical Signal Processing and Control}, volume = {45}, pages = {246--255}, publisher = {Elsevier Ltd}, abstract = {This paper presents a novel method for removing ocular artifacts from EEG recordings. The proposed approach is based on time-domain linear filtering. Instead of directly estimating the artifact-free signal, we propose to obtain the eye-blink signal first, using a multichannel Wiener filter (MWF) and a small subset of the frontal electrodes, so that extra EOG sensors are unnecessary. Then, the estimate of the eye-blink signal is subtracted from the noisy EEG signal in accordance with principles of regression analysis. We have performed numerical simulations so as to compare our approach to the independent component analysis (ICA) that is commonly used in EEG enhancement. Our experiments show that the MWF-based approach can perform better than the ICA in terms of eye-blink cancellation and signal distortions. Besides that, the proposed approach is conceptually simpler and better suited to real-time applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a novel method for removing ocular artifacts from EEG recordings. The proposed approach is based on time-domain linear filtering. Instead of directly estimating the artifact-free signal, we propose to obtain the eye-blink signal first, using a multichannel Wiener filter (MWF) and a small subset of the frontal electrodes, so that extra EOG sensors are unnecessary. Then, the estimate of the eye-blink signal is subtracted from the noisy EEG signal in accordance with principles of regression analysis. We have performed numerical simulations so as to compare our approach to the independent component analysis (ICA) that is commonly used in EEG enhancement. Our experiments show that the MWF-based approach can perform better than the ICA in terms of eye-blink cancellation and signal distortions. Besides that, the proposed approach is conceptually simpler and better suited to real-time applications. |
S E Bosch; S F W Neggers; S Van Der Stigchel The role of the frontal eye fields in oculomotor competition: Image-guided TMS enhances contralateral target selection Journal Article Cerebral Cortex, 23 (4), pp. 824–832, 2013. @article{Bosch2013, title = {The role of the frontal eye fields in oculomotor competition: Image-guided TMS enhances contralateral target selection}, author = {S E Bosch and S F W Neggers and S {Van Der Stigchel}}, doi = {10.1093/cercor/bhs075}, year = {2013}, date = {2013-01-01}, journal = {Cerebral Cortex}, volume = {23}, number = {4}, pages = {824--832}, abstract = {In order to execute a correct eye movement to a target in a search display, a saccade program toward the target element must be activated, while saccade programs toward distracting elements must be inhibited. The aim of the present study was to elucidate the role of the frontal eye fields (FEFs) in oculomotor competition. Functional magnetic resonance imaging-guided single-pulse transcranial magnetic stimulation (TMS) was administered over either the left FEF, the right FEF, or the vertex (control site) at 3 time intervals after target presentation, while subjects performed an oculomotor capture task. When TMS was applied over the FEF contralateral to the visual field where a target was presented, there was less interference of an ipsilateral distractor compared with FEF stimulation ipsilateral to the target's visual field or TMS over vertex. Furthermore, TMS over the FEFs decreased latencies of saccades to the contralateral visual field, irrespective of whether the saccade was directed to the target or to the distractor. These findings show that single-pulse TMS over the FEFs enhances the selection of a target in the contralateral visual field and decreases saccade latencies to the contralateral visual field.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to execute a correct eye movement to a target in a search display, a saccade program toward the target element must be activated, while saccade programs toward distracting elements must be inhibited. The aim of the present study was to elucidate the role of the frontal eye fields (FEFs) in oculomotor competition. Functional magnetic resonance imaging-guided single-pulse transcranial magnetic stimulation (TMS) was administered over either the left FEF, the right FEF, or the vertex (control site) at 3 time intervals after target presentation, while subjects performed an oculomotor capture task. When TMS was applied over the FEF contralateral to the visual field where a target was presented, there was less interference of an ipsilateral distractor compared with FEF stimulation ipsilateral to the target's visual field or TMS over vertex. Furthermore, TMS over the FEFs decreased latencies of saccades to the contralateral visual field, irrespective of whether the saccade was directed to the target or to the distractor. These findings show that single-pulse TMS over the FEFs enhances the selection of a target in the contralateral visual field and decreases saccade latencies to the contralateral visual field. |
Harriet R Brown; Karl J Friston The functional anatomy of attention: A DCM study Journal Article Frontiers in Human Neuroscience, 7 (December), 2013. @article{Brown2013, title = {The functional anatomy of attention: A DCM study}, author = {Harriet R Brown and Karl J Friston}, url = {http://journal.frontiersin.org/article/10.3389/fnhum.2013.00784/abstract}, doi = {10.3389/fnhum.2013.00784}, year = {2013}, date = {2013-01-01}, journal = {Frontiers in Human Neuroscience}, volume = {7}, number = {December}, abstract = {Recent formulations of attention—in terms of predictive coding—associate attentional gain with the expected precision of sensory information. Formal models of the Posner paradigm suggest that validity effects can be explained in a principled (Bayes optimal) fashion in terms of a cue-dependent setting of precision or gain on the sensory channels reporting anticipated target locations, which is updated selectively by invalid targets. This normative model is equipped with a biologically plausible process theory in the form of predictive coding, where precision is encoded by the gain of superficial pyramidal cells reporting prediction error. We used dynamic causal modeling to assess the evidence in magnetoencephalographic responses for cue-dependent and top-down updating of superficial pyramidal cell gain. Bayesian model comparison suggested that it is almost certain that differences in superficial pyramidal cells gain—and its top-down modulation—contribute to observed responses; and we could be more than 80% certain that anticipatory effects on post-synaptic gain are limited to visual (extrastriate) sources. These empirical results speak to the role of attention in optimizing perceptual inference and its formulation in terms of predictive coding.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent formulations of attention—in terms of predictive coding—associate attentional gain with the expected precision of sensory information. Formal models of the Posner paradigm suggest that validity effects can be explained in a principled (Bayes optimal) fashion in terms of a cue-dependent setting of precision or gain on the sensory channels reporting anticipated target locations, which is updated selectively by invalid targets. This normative model is equipped with a biologically plausible process theory in the form of predictive coding, where precision is encoded by the gain of superficial pyramidal cells reporting prediction error. We used dynamic causal modeling to assess the evidence in magnetoencephalographic responses for cue-dependent and top-down updating of superficial pyramidal cell gain. Bayesian model comparison suggested that it is almost certain that differences in superficial pyramidal cells gain—and its top-down modulation—contribute to observed responses; and we could be more than 80% certain that anticipatory effects on post-synaptic gain are limited to visual (extrastriate) sources. These empirical results speak to the role of attention in optimizing perceptual inference and its formulation in terms of predictive coding. |
M R Burke; R O Coats Dissociation of the rostral and dorsolateral prefrontal cortex during sequence learning in saccades: A TMS investigation Journal Article Experimental Brain Research, 234 (2), pp. 597–604, 2016. @article{Burke2016, title = {Dissociation of the rostral and dorsolateral prefrontal cortex during sequence learning in saccades: A TMS investigation}, author = {M R Burke and R O Coats}, doi = {10.1007/s00221-015-4495-2}, year = {2016}, date = {2016-01-01}, journal = {Experimental Brain Research}, volume = {234}, number = {2}, pages = {597--604}, publisher = {Springer Berlin Heidelberg}, abstract = {This experiment sought to find whether differences exist between the dorsolateral prefrontal cortex (DLPFC) and the medial rostral prefrontal cortex (MRPFC) for performing stimulus-independent and stimulus-oriented tasks, respectively. To find a causal relationship in these areas, we employed the use of trans-cranial magnetic stimulation (TMS). Prefrontal areas were stimulated whilst participants performed random or predictable sequence learning tasks at stimulus onset (1st presentation of the sequence only for both Random and Predictable), or during the inter-sequence interval. Overall, we found that during the predictable task a significant decrease in saccade latency, gain and duration was found when compared to the randomised conditions, as expected and observed previously. However, TMS stimulation in DLPFC during the delay in the predictive sequence learning task reduced this predictive ability by delaying the saccadic onset and generating abnormal reductions in saccadic gains during prediction. In contrast, we found that stimulation during a delay in MRPFC reversed the normal effects on peak velocity of the task with the predictive task revealing higher peak velocity than the randomised task. These findings provide causal evidence for independent functions of DLPFC and MRPFC in performing stimulus-independent processing during sequence learning in saccades.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This experiment sought to find whether differences exist between the dorsolateral prefrontal cortex (DLPFC) and the medial rostral prefrontal cortex (MRPFC) for performing stimulus-independent and stimulus-oriented tasks, respectively. To find a causal relationship in these areas, we employed the use of trans-cranial magnetic stimulation (TMS). Prefrontal areas were stimulated whilst participants performed random or predictable sequence learning tasks at stimulus onset (1st presentation of the sequence only for both Random and Predictable), or during the inter-sequence interval. Overall, we found that during the predictable task a significant decrease in saccade latency, gain and duration was found when compared to the randomised conditions, as expected and observed previously. However, TMS stimulation in DLPFC during the delay in the predictive sequence learning task reduced this predictive ability by delaying the saccadic onset and generating abnormal reductions in saccadic gains during prediction. In contrast, we found that stimulation during a delay in MRPFC reversed the normal effects on peak velocity of the task with the predictive task revealing higher peak velocity than the randomised task. These findings provide causal evidence for independent functions of DLPFC and MRPFC in performing stimulus-independent processing during sequence learning in saccades. |
Florence Campana; Ignacio Rebollo; Anne Urai; Valentin Wyart; Catherine Tallon-Baudry Conscious vision proceeds from global to local content in goal-directed tasks and spontaneous vision Journal Article Journal of Neuroscience, 36 (19), pp. 5200–5213, 2016. @article{Campana2016, title = {Conscious vision proceeds from global to local content in goal-directed tasks and spontaneous vision}, author = {Florence Campana and Ignacio Rebollo and Anne Urai and Valentin Wyart and Catherine Tallon-Baudry}, url = {http://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.3619-15.2016}, doi = {10.1523/JNEUROSCI.3619-15.2016}, year = {2016}, date = {2016-01-01}, journal = {Journal of Neuroscience}, volume = {36}, number = {19}, pages = {5200--5213}, abstract = {The reverse hierarchy theory (Hochstein and Ahissar, 2002) makes strong, but so far untested, predictions on conscious vision. In this theory, local details encoded in lower-order visual areas are unconsciously processed before being automatically and rapidly combined into global information in higher-order visual areas, where conscious percepts emerge. Contingent on current goals, local details can afterward be consciously retrieved. This model therefore predicts that (1) global information is perceived faster than local details, (2) global information is computed regardless of task demands during early visual processing, and (3) spontaneous vision is dominated by global percepts. We designed novel textured stimuli that are, as opposed to the classic Navon's letters, truly hierarchical (i.e., where global information is solely defined by local information but where local and global orientations can still be manipulated separately). In line with the predictions, observers were systematically faster reporting global than local properties of those stimuli. Second, global information could be decoded from magneto-encephalographic data during early visual processing regardless of task demands. Last, spontaneous subjective reports were dominated by global information and the frequency and speed of spontaneous global perception correlated with the accuracy and speed in the global task. No such correlation was observed for local information. We therefore show that information at different levels of the visual hierarchy is not equally likely to become conscious; rather, conscious percepts emerge preferentially at a global level. We further show that spontaneous reports can be reliable and are tightly linked to objective performance at the global level.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The reverse hierarchy theory (Hochstein and Ahissar, 2002) makes strong, but so far untested, predictions on conscious vision. In this theory, local details encoded in lower-order visual areas are unconsciously processed before being automatically and rapidly combined into global information in higher-order visual areas, where conscious percepts emerge. Contingent on current goals, local details can afterward be consciously retrieved. This model therefore predicts that (1) global information is perceived faster than local details, (2) global information is computed regardless of task demands during early visual processing, and (3) spontaneous vision is dominated by global percepts. We designed novel textured stimuli that are, as opposed to the classic Navon's letters, truly hierarchical (i.e., where global information is solely defined by local information but where local and global orientations can still be manipulated separately). In line with the predictions, observers were systematically faster reporting global than local properties of those stimuli. Second, global information could be decoded from magneto-encephalographic data during early visual processing regardless of task demands. Last, spontaneous subjective reports were dominated by global information and the frequency and speed of spontaneous global perception correlated with the accuracy and speed in the global task. No such correlation was observed for local information. We therefore show that information at different levels of the visual hierarchy is not equally likely to become conscious; rather, conscious percepts emerge preferentially at a global level. We further show that spontaneous reports can be reliable and are tightly linked to objective performance at the global level. |
Almudena Capilla; Pascal Belin; Joachim Gross The early spatio-temporal correlates and task independence of cerebral voice processing studied with MEG Journal Article Cerebral Cortex, 23 (6), pp. 1388–1395, 2013. @article{Capilla2013, title = {The early spatio-temporal correlates and task independence of cerebral voice processing studied with MEG}, author = {Almudena Capilla and Pascal Belin and Joachim Gross}, doi = {10.1093/cercor/bhs119}, year = {2013}, date = {2013-01-01}, journal = {Cerebral Cortex}, volume = {23}, number = {6}, pages = {1388--1395}, abstract = {Functional magnetic resonance imaging studies have repeatedly provided evidence for temporal voice areas (TVAs) with particular sensitivity to human voices along bilateral mid/anterior superior temporal sulci and superior temporal gyri (STS/STG). In contrast, electrophysiological studies of the spatio-temporal correlates of cerebral voice processing have yielded contradictory results, finding the earliest correlates either at ∼300-400 ms, or earlier at ∼200 ms ("fronto-temporal positivity to voice", FTPV). These contradictory results are likely the consequence of different stimulus sets and attentional demands. Here, we recorded magnetoencephalography activity while participants listened to diverse types of vocal and non-vocal sounds and performed different tasks varying in attentional demands. Our results confirm the existence of an early voice-preferential magnetic response (FTPVm, the magnetic counterpart of the FTPV) peaking at about 220 ms and distinguishing between vocal and non-vocal sounds as early as 150 ms after stimulus onset. The sources underlying the FTPVm were localized along bilateral mid-STS/STG, largely overlapping with the TVAs. The FTPVm was consistently observed across different stimulus subcategories, including speech and non-speech vocal sounds, and across different tasks. These results demonstrate the early, largely automatic recruitment of focal, voice-selective cerebral mechanisms with a time-course comparable to that of face processing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Functional magnetic resonance imaging studies have repeatedly provided evidence for temporal voice areas (TVAs) with particular sensitivity to human voices along bilateral mid/anterior superior temporal sulci and superior temporal gyri (STS/STG). In contrast, electrophysiological studies of the spatio-temporal correlates of cerebral voice processing have yielded contradictory results, finding the earliest correlates either at ∼300-400 ms, or earlier at ∼200 ms ("fronto-temporal positivity to voice", FTPV). These contradictory results are likely the consequence of different stimulus sets and attentional demands. Here, we recorded magnetoencephalography activity while participants listened to diverse types of vocal and non-vocal sounds and performed different tasks varying in attentional demands. Our results confirm the existence of an early voice-preferential magnetic response (FTPVm, the magnetic counterpart of the FTPV) peaking at about 220 ms and distinguishing between vocal and non-vocal sounds as early as 150 ms after stimulus onset. The sources underlying the FTPVm were localized along bilateral mid-STS/STG, largely overlapping with the TVAs. The FTPVm was consistently observed across different stimulus subcategories, including speech and non-speech vocal sounds, and across different tasks. These results demonstrate the early, largely automatic recruitment of focal, voice-selective cerebral mechanisms with a time-course comparable to that of face processing. |
Nathan Caruana; Peter de Lissa; Genevieve McArthur The neural time course of evaluating self-initiated joint attention bids Journal Article Brain and Cognition, 98 , pp. 43–52, 2015. @article{Caruana2015a, title = {The neural time course of evaluating self-initiated joint attention bids}, author = {Nathan Caruana and Peter de Lissa and Genevieve McArthur}, url = {http://dx.doi.org/10.1016/j.bandc.2015.06.001}, doi = {10.1016/j.bandc.2015.06.001}, year = {2015}, date = {2015-01-01}, journal = {Brain and Cognition}, volume = {98}, pages = {43--52}, publisher = {Elsevier Inc.}, abstract = {Background: During interactions with other people, we constantly evaluate the significance of our social partner's gaze shifts in order to coordinate our behaviour with their perspective. In this study, we used event-related potentials (ERPs) to investigate the neural time course of evaluating gaze shifts that signal the success of self-initiated joint attention bids. Method: Nineteen participants were allocated to a "social" condition, in which they played a cooperative game with an anthropomorphic virtual character whom they believed was controlled by a human partner in a nearby laboratory. Participants were required to initiate joint attention towards a target. In response, the virtual partner shifted his gaze congruently towards the target - thus achieving joint attention - or incongruently towards a different location. Another 19 participants completed the same task in a non-social "control" condition, in which arrows, believed to be controlled by a computer program, pointed at a location that was either congruent or incongruent with the participant's target fixation. Results: In the social condition, ERPs to the virtual partner's incongruent gaze shifts evoked significantly larger P350 and P500 peaks compared to congruent gaze shifts. This P350 and P500 morphology was absent in both the congruent and incongruent control conditions. Discussion: These findings are consistent with previous claims that gaze shifts differing in their social significance modulate central-parietal ERPs 350. ms following the onset of the gaze shift. Our control data highlights the social specificity of the observed P350 effect, ruling out explanations pertaining to attention modulation or error detection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: During interactions with other people, we constantly evaluate the significance of our social partner's gaze shifts in order to coordinate our behaviour with their perspective. In this study, we used event-related potentials (ERPs) to investigate the neural time course of evaluating gaze shifts that signal the success of self-initiated joint attention bids. Method: Nineteen participants were allocated to a "social" condition, in which they played a cooperative game with an anthropomorphic virtual character whom they believed was controlled by a human partner in a nearby laboratory. Participants were required to initiate joint attention towards a target. In response, the virtual partner shifted his gaze congruently towards the target - thus achieving joint attention - or incongruently towards a different location. Another 19 participants completed the same task in a non-social "control" condition, in which arrows, believed to be controlled by a computer program, pointed at a location that was either congruent or incongruent with the participant's target fixation. Results: In the social condition, ERPs to the virtual partner's incongruent gaze shifts evoked significantly larger P350 and P500 peaks compared to congruent gaze shifts. This P350 and P500 morphology was absent in both the congruent and incongruent control conditions. Discussion: These findings are consistent with previous claims that gaze shifts differing in their social significance modulate central-parietal ERPs 350. ms following the onset of the gaze shift. Our control data highlights the social specificity of the observed P350 effect, ruling out explanations pertaining to attention modulation or error detection. |
Nathan Caruana; Peter de Lissa; Genevieve McArthur Beliefs about human agency influence the neural processing of gaze during joint attention Journal Article Social Neuroscience, 12 (2), pp. 194–206, 2017. @article{Caruana2017b, title = {Beliefs about human agency influence the neural processing of gaze during joint attention}, author = {Nathan Caruana and Peter de Lissa and Genevieve McArthur}, doi = {10.1080/17470919.2016.1160953}, year = {2017}, date = {2017-01-01}, journal = {Social Neuroscience}, volume = {12}, number = {2}, pages = {194--206}, publisher = {Routledge}, abstract = {The current study measured adults' P350 and N170 ERPs while they interacted with a character in a virtual reality paradigm. Some participants believed the character was controlled by a human ("avatar" condition}, keywords = {}, pubstate = {published}, tppubtype = {article} } The current study measured adults' P350 and N170 ERPs while they interacted with a character in a virtual reality paradigm. Some participants believed the character was controlled by a human ("avatar" condition |
Marta Castellano; Michael Plöchl; Raul Vicente; Gordon Pipa Neuronal oscillations form parietal/frontal networks during contour integration Journal Article Frontiers in Integrative Neuroscience, 8 , pp. 1–13, 2014. @article{Castellano2014, title = {Neuronal oscillations form parietal/frontal networks during contour integration}, author = {Marta Castellano and Michael Plöchl and Raul Vicente and Gordon Pipa}, url = {http://journal.frontiersin.org/article/10.3389/fnint.2014.00064/abstract}, doi = {10.3389/fnint.2014.00064}, year = {2014}, date = {2014-01-01}, journal = {Frontiers in Integrative Neuroscience}, volume = {8}, pages = {1--13}, abstract = {The ability to integrate visual features into a global coherent percept that can be further categorized and manipulated are fundamental abilities of the neural system. While the processing of visual information involves activation of early visual cortices, the recruitment of parietal and frontal cortices has been shown to be crucial for perceptual processes. Yet is it not clear how both cortical and long-range oscillatory activity leads to the integration of visual features into a coherent percept. Here, we will investigate perceptual grouping through the analysis of a contour categorization task, where the local elements that form contour must be linked into a coherent structure, which is then further processed and manipulated to perform the categorization task. The contour formation in our visual stimulus is a dynamic process where, for the first time, visual perception of contours is disentangled from the onset of visual stimulation or from motor preparation, cognitive processes that until now have been behaviorally attached to perceptual processes. Our main finding is that, while local and long-range synchronization at several frequencies seem to be an ongoing phenomena, categorization of a contour could only be predicted through local oscillatory activity within parietal/frontal sources, which in turn, would synchronize at gamma (textgreater30 Hz) frequency. Simultaneously, fronto-parietal beta (13-30 Hz) phase locking forms a network spanning across neural sources that are not category specific. Both long range networks, i.e., the gamma network that is category specific, and the beta network that is not category specific, are functionally distinct but spatially overlapping. Altogether, we show that a critical mechanism underlying contour categorization involves oscillatory activity within parietal/frontal cortices, as well as its synchronization across distal cortical sites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The ability to integrate visual features into a global coherent percept that can be further categorized and manipulated are fundamental abilities of the neural system. While the processing of visual information involves activation of early visual cortices, the recruitment of parietal and frontal cortices has been shown to be crucial for perceptual processes. Yet is it not clear how both cortical and long-range oscillatory activity leads to the integration of visual features into a coherent percept. Here, we will investigate perceptual grouping through the analysis of a contour categorization task, where the local elements that form contour must be linked into a coherent structure, which is then further processed and manipulated to perform the categorization task. The contour formation in our visual stimulus is a dynamic process where, for the first time, visual perception of contours is disentangled from the onset of visual stimulation or from motor preparation, cognitive processes that until now have been behaviorally attached to perceptual processes. Our main finding is that, while local and long-range synchronization at several frequencies seem to be an ongoing phenomena, categorization of a contour could only be predicted through local oscillatory activity within parietal/frontal sources, which in turn, would synchronize at gamma (textgreater30 Hz) frequency. Simultaneously, fronto-parietal beta (13-30 Hz) phase locking forms a network spanning across neural sources that are not category specific. Both long range networks, i.e., the gamma network that is category specific, and the beta network that is not category specific, are functionally distinct but spatially overlapping. Altogether, we show that a critical mechanism underlying contour categorization involves oscillatory activity within parietal/frontal cortices, as well as its synchronization across distal cortical sites. |
Dario Cazzoli; René M Müri; Christopher Kennard; Clive R Rosenthal The role of the right posterior parietal cortex in letter migration between words Journal Article Journal of Cognitive Neuroscience, 27 (2), pp. 377–386, 2015. @article{Cazzoli2015a, title = {The role of the right posterior parietal cortex in letter migration between words}, author = {Dario Cazzoli and René M Müri and Christopher Kennard and Clive R Rosenthal}, year = {2015}, date = {2015-01-01}, journal = {Journal of Cognitive Neuroscience}, volume = {27}, number = {2}, pages = {377--386}, abstract = {When briefly presented with pairs of words, skilled readers can sometimes report words with migrated letters (e.g., they report hunt when presented with the words hint and hurt). This and other letter migration phenomena have been often used to investigate factors that influence reading such as letter position coding. However, the neural basis of letter migration is poorly understood. Previous evidence has implicated the right posterior parietal cortex (PPC) in processing visuospatial attributes and lexical properties during word reading. The aim of this study was to assess this putative role by combining an inhibitory TMS protocol with a letter migration paradigm, which was designed to examine the contributions of visuospatial attributes and lexical factors. Temporary interference with the right PPC led to three specific effects on letter migration. First, the number of letter migrations was significantly increased only in the group with active stimulation (vs. a sham stimulation group or a control group without stimulation), and there was no significant effect on other error types. Second, this effect occurred only when letter migration could result in a meaningful word (migration vs. control context). Third, the effect of active stimulation on the number of letter migrations was lateralized to target words presented on the left. Our study thus demonstrates that the right PPC plays a specific and causal role in the phenomenon of letter migration. The nature of this role cannot be explained solely in terms of visuospatial attention, rather it involves an interplay between visuospatial attentional and word reading-specific factors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When briefly presented with pairs of words, skilled readers can sometimes report words with migrated letters (e.g., they report hunt when presented with the words hint and hurt). This and other letter migration phenomena have been often used to investigate factors that influence reading such as letter position coding. However, the neural basis of letter migration is poorly understood. Previous evidence has implicated the right posterior parietal cortex (PPC) in processing visuospatial attributes and lexical properties during word reading. The aim of this study was to assess this putative role by combining an inhibitory TMS protocol with a letter migration paradigm, which was designed to examine the contributions of visuospatial attributes and lexical factors. Temporary interference with the right PPC led to three specific effects on letter migration. First, the number of letter migrations was significantly increased only in the group with active stimulation (vs. a sham stimulation group or a control group without stimulation), and there was no significant effect on other error types. Second, this effect occurred only when letter migration could result in a meaningful word (migration vs. control context). Third, the effect of active stimulation on the number of letter migrations was lateralized to target words presented on the left. Our study thus demonstrates that the right PPC plays a specific and causal role in the phenomenon of letter migration. The nature of this role cannot be explained solely in terms of visuospatial attention, rather it involves an interplay between visuospatial attentional and word reading-specific factors. |
Chang-Mao Chao; Philip Tseng; Tzu Yu Hsu; Jia-Han Su; Ovid J L Tzeng; Daisy L Hung; Neil G Muggleton; Chi-Hung Juan Predictability of saccadic behaviors is modified by transcranial magnetic stimulation over human posterior parietal cortex Journal Article Human Brain Mapping, 32 (11), pp. 1961–1972, 2011. @article{Chao2011, title = {Predictability of saccadic behaviors is modified by transcranial magnetic stimulation over human posterior parietal cortex}, author = {Chang-Mao Chao and Philip Tseng and Tzu Yu Hsu and Jia-Han Su and Ovid J L Tzeng and Daisy L Hung and Neil G Muggleton and Chi-Hung Juan}, doi = {10.1002/hbm.21162}, year = {2011}, date = {2011-01-01}, journal = {Human Brain Mapping}, volume = {32}, number = {11}, pages = {1961--1972}, abstract = {Predictability in the visual environment provides a powerful cue for efficient processing of scenes and objects. Recently, studies have suggested that the directionality and magnitude of saccade curvature can be informative as to how the visual system processes predictive information. The pres-ent study investigated the role of the right posterior parietal cortex (rPPC) in shaping saccade curva-tures in the context of predictive and non-predictive visual cues. We used an orienting paradigm that incorporated manipulation of target location predictability and delivered transcranial magnetic stimulation (TMS) over rPPC. Participants were presented with either an informative or uninforma-tive cue to upcoming target locations. Our results showed that rPPC TMS generally increased sac-cade latency and saccade error rates. Intriguingly, rPPC TMS increased curvatures away from the distractor only when the target location was unpredictable and decreased saccadic errors towards the distractor. These effects on curvature and accuracy were not present when the target location was predictable. These results dissociate the strong contingency between saccade latency and saccade curvature and also indicate that rPPC plays an important role in allocating and suppressing attention to distractors when the target demands visual disambiguation. Furthermore, the present study sug-gests that, like the frontal eye fields, rPPC is critically involved in determining saccade curvature and the generation of saccadic behaviors under conditions of differing target predictability.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Predictability in the visual environment provides a powerful cue for efficient processing of scenes and objects. Recently, studies have suggested that the directionality and magnitude of saccade curvature can be informative as to how the visual system processes predictive information. The pres-ent study investigated the role of the right posterior parietal cortex (rPPC) in shaping saccade curva-tures in the context of predictive and non-predictive visual cues. We used an orienting paradigm that incorporated manipulation of target location predictability and delivered transcranial magnetic stimulation (TMS) over rPPC. Participants were presented with either an informative or uninforma-tive cue to upcoming target locations. Our results showed that rPPC TMS generally increased sac-cade latency and saccade error rates. Intriguingly, rPPC TMS increased curvatures away from the distractor only when the target location was unpredictable and decreased saccadic errors towards the distractor. These effects on curvature and accuracy were not present when the target location was predictable. These results dissociate the strong contingency between saccade latency and saccade curvature and also indicate that rPPC plays an important role in allocating and suppressing attention to distractors when the target demands visual disambiguation. Furthermore, the present study sug-gests that, like the frontal eye fields, rPPC is critically involved in determining saccade curvature and the generation of saccadic behaviors under conditions of differing target predictability. |
Magdalena Chechlacz; Glyn W Humphreys; Stamatios N Sotiropoulos; Christopher Kennard; Dario Cazzoli Structural organization of the corpus callosum predicts attentional shifts after continuous theta burst stimulation Journal Article Journal of Neuroscience, 35 (46), pp. 15353–15368, 2015. @article{Chechlacz2015, title = {Structural organization of the corpus callosum predicts attentional shifts after continuous theta burst stimulation}, author = {Magdalena Chechlacz and Glyn W Humphreys and Stamatios N Sotiropoulos and Christopher Kennard and Dario Cazzoli}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.2610-15.2015}, doi = {10.1523/JNEUROSCI.2610-15.2015}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neuroscience}, volume = {35}, number = {46}, pages = {15353--15368}, abstract = {Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes in brain activation suggest that the effects of rTMS may depend on both interhemispheric and intrahemispheric interactions between cortical loci controlling visual attention. Here, we investigated whether variability in the structural organization of human white matter pathways subserving visual attention, as assessed by diffusion magnetic resonance imaging and tractography, could explain interindividual differences in the effects of rTMS. Most participants showed a rightward shift in the allocation of spatial attention after rTMS over the right intraparietal sulcus (IPS), but the size of this effect varied largely across participants. Conversely, rTMS over the left IPS resulted in strikingly opposed individual responses, with some participants responding with rightward and some with leftward attentional shifts. We demonstrate that microstructural and macrostructural variability within the corpus callosum, consistent with differential effects on cross-hemispheric interactions, predicts both the extent and the direction of the response to rTMS. Together, our findings suggest that the corpus callosum may have a dual inhibitory and excitatory function in maintaining the interhemispheric dynamics that underlie the allocation of spatial attention.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes in brain activation suggest that the effects of rTMS may depend on both interhemispheric and intrahemispheric interactions between cortical loci controlling visual attention. Here, we investigated whether variability in the structural organization of human white matter pathways subserving visual attention, as assessed by diffusion magnetic resonance imaging and tractography, could explain interindividual differences in the effects of rTMS. Most participants showed a rightward shift in the allocation of spatial attention after rTMS over the right intraparietal sulcus (IPS), but the size of this effect varied largely across participants. Conversely, rTMS over the left IPS resulted in strikingly opposed individual responses, with some participants responding with rightward and some with leftward attentional shifts. We demonstrate that microstructural and macrostructural variability within the corpus callosum, consistent with differential effects on cross-hemispheric interactions, predicts both the extent and the direction of the response to rTMS. Together, our findings suggest that the corpus callosum may have a dual inhibitory and excitatory function in maintaining the interhemispheric dynamics that underlie the allocation of spatial attention. |
Jing Chen; Matteo Valsecchi; Karl R Gegenfurtner LRP predicts smooth pursuit eye movement onset during the ocular tracking of self-generated movements Journal Article Journal of Neurophysiology, 116 (1), pp. 18–29, 2016. @article{Chen2016d, title = {LRP predicts smooth pursuit eye movement onset during the ocular tracking of self-generated movements}, author = {Jing Chen and Matteo Valsecchi and Karl R Gegenfurtner}, url = {http://jn.physiology.org/lookup/doi/10.1152/jn.00184.2016}, doi = {10.1152/jn.00184.2016}, year = {2016}, date = {2016-01-01}, journal = {Journal of Neurophysiology}, volume = {116}, number = {1}, pages = {18--29}, abstract = {Several studies indicated that human observers are very efficient at tracking self-generated hand movements with their gaze, yet it is not clear whether this is simply a byproduct of the predictability of self-generated actions or if it results from a deeper coupling of the somatomotor and oculomotor systems. In a first behavioral experiment we compared pursuit performance as observers either followed their own finger or tracked a dot whose motion was externally generated but mimicked their finger motion. We found that even when the dot motion was completely predictable both in terms of onset time and in terms of kinematics, pursuit was not identical to the one produced as the observers tracked their finger, as evidenced by increased rate of catch-up saccades and by the fact that in the initial phase of the movement gaze was lagging behind the dot, whereas it was ahead of the finger. In a second experiment we recorded EEG in the attempt to find a direct link between the finger motor preparation, indexed by the lateralized readiness potential (LRP), and the latency of smooth pursuit. After taking into account finger movement onset variability, we observed larger LRP amplitudes associated with earlier smooth pursuit onset across trials. The same held across subjects, where average LRP onset correlated with average eye latency. The evidence from both experiments concurs to indicate that a strong coupling exists between the motor systems leading to eye and finger movements and that simple top-down predictive signals are unlikely to support optimal coordination.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Several studies indicated that human observers are very efficient at tracking self-generated hand movements with their gaze, yet it is not clear whether this is simply a byproduct of the predictability of self-generated actions or if it results from a deeper coupling of the somatomotor and oculomotor systems. In a first behavioral experiment we compared pursuit performance as observers either followed their own finger or tracked a dot whose motion was externally generated but mimicked their finger motion. We found that even when the dot motion was completely predictable both in terms of onset time and in terms of kinematics, pursuit was not identical to the one produced as the observers tracked their finger, as evidenced by increased rate of catch-up saccades and by the fact that in the initial phase of the movement gaze was lagging behind the dot, whereas it was ahead of the finger. In a second experiment we recorded EEG in the attempt to find a direct link between the finger motor preparation, indexed by the lateralized readiness potential (LRP), and the latency of smooth pursuit. After taking into account finger movement onset variability, we observed larger LRP amplitudes associated with earlier smooth pursuit onset across trials. The same held across subjects, where average LRP onset correlated with average eye latency. The evidence from both experiments concurs to indicate that a strong coupling exists between the motor systems leading to eye and finger movements and that simple top-down predictive signals are unlikely to support optimal coordination. |
Jing Chen; Matteo Valsecchi; Karl R Gegenfurtner Enhanced brain responses to color during smooth-pursuit eye movements Journal Article Journal of Neurophysiology, 118 , pp. 749–754, 2017. @article{Chen2017a, title = {Enhanced brain responses to color during smooth-pursuit eye movements}, author = {Jing Chen and Matteo Valsecchi and Karl R Gegenfurtner}, doi = {10.1152/jn.00208.2017}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neurophysiology}, volume = {118}, pages = {749--754}, abstract = {Eye movements alter visual perceptions in a number of ways. During smooth pursuit eye movements, previous studies reported decreased detection threshold for colored stimuli and for high-spatial-frequency luminance stimuli, suggesting a boost in the parvocellular system. The present study investigated the underlying neural mechanism using EEG in human participants. Participants followed a moving target with smooth pursuit eye movements while steady-state visually Evoked potentials (SSVEPs) were elicited by equiluminant red-green flickering gratings in the background. SSVEP responses to color gratings were 18.9% higher during smooth pursuit than during fixation. There was no enhancement of SSVEPs by smooth pursuit when the flickering grating was defined by luminance instead of color. This result provides physiological evidence that the chromatic response in the visual system is boosted by the execution of smooth pursuit eye movements in humans. Since the response improvement is thought to be due to an improved response in the parvocellular system, SSVEPs to equiluminant stimuli could provide a direct test of parvocellular signaling, especially in populations where an explicit behavioral response from the participant is not feasible.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Eye movements alter visual perceptions in a number of ways. During smooth pursuit eye movements, previous studies reported decreased detection threshold for colored stimuli and for high-spatial-frequency luminance stimuli, suggesting a boost in the parvocellular system. The present study investigated the underlying neural mechanism using EEG in human participants. Participants followed a moving target with smooth pursuit eye movements while steady-state visually Evoked potentials (SSVEPs) were elicited by equiluminant red-green flickering gratings in the background. SSVEP responses to color gratings were 18.9% higher during smooth pursuit than during fixation. There was no enhancement of SSVEPs by smooth pursuit when the flickering grating was defined by luminance instead of color. This result provides physiological evidence that the chromatic response in the visual system is boosted by the execution of smooth pursuit eye movements in humans. Since the response improvement is thought to be due to an improved response in the parvocellular system, SSVEPs to equiluminant stimuli could provide a direct test of parvocellular signaling, especially in populations where an explicit behavioral response from the participant is not feasible. |
Hui-Yan Chiau; Neil G Muggleton; Chi-Hung Juan Exploring the contributions of the supplementary eye field to subliminal inhibition using double-pulse transcranial magnetic stimulation Journal Article Human Brain Mapping, 38 , pp. 339–351, 2017. @article{Chiau2017, title = {Exploring the contributions of the supplementary eye field to subliminal inhibition using double-pulse transcranial magnetic stimulation}, author = {Hui-Yan Chiau and Neil G Muggleton and Chi-Hung Juan}, doi = {10.1002/hbm.23364}, year = {2017}, date = {2017-01-01}, journal = {Human Brain Mapping}, volume = {38}, pages = {339--351}, abstract = {It is widely accepted that the supplementary eye fields (SEF) are involved in the control of voluntary eye movements. However, recent evidence suggests that SEF may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. ([2007]: Neuron 54:697-711) showed that patients with micro-lesions of the SEF demonstrated an absence of subliminal inhibition as evoked by masked-prime stimuli. Here, we used double-pulse transcranial magnetic stimulation (TMS) in healthy volunteers to investigate the role of SEF in subliminal priming. We applied double-pulse TMS at two time windows in a masked-prime task: the first during an early phase, 20-70 ms after the onset of the mask but before target presentation, during which subliminal inhibition is present; and the second during a late phase, 20-70 ms after target onset, during which the saccade is being prepared. We found no effect of TMS with the early time window of stimulation, whereas a reduction in the benefit of an incompatible subliminal prime stimulus was found when SEF TMS was applied at the late time window. These findings suggest that there is a role for SEF related to the effects of subliminal primes on eye movements, but the results do not support a role in inhibiting the primed tendency.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is widely accepted that the supplementary eye fields (SEF) are involved in the control of voluntary eye movements. However, recent evidence suggests that SEF may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. ([2007]: Neuron 54:697-711) showed that patients with micro-lesions of the SEF demonstrated an absence of subliminal inhibition as evoked by masked-prime stimuli. Here, we used double-pulse transcranial magnetic stimulation (TMS) in healthy volunteers to investigate the role of SEF in subliminal priming. We applied double-pulse TMS at two time windows in a masked-prime task: the first during an early phase, 20-70 ms after the onset of the mask but before target presentation, during which subliminal inhibition is present; and the second during a late phase, 20-70 ms after target onset, during which the saccade is being prepared. We found no effect of TMS with the early time window of stimulation, whereas a reduction in the benefit of an incompatible subliminal prime stimulus was found when SEF TMS was applied at the late time window. These findings suggest that there is a role for SEF related to the effects of subliminal primes on eye movements, but the results do not support a role in inhibiting the primed tendency. |
Hak Soo Choi; Shinjung Kim; Donghoon Lee; Chang Seok Kim; Myung Yung Jeong Synchronized tracking of brain cognitive processing using EEG and vision signals Journal Article Applied Spectroscopy Reviews, 51 (7-9), pp. 592–602, 2016. @article{Choi2016, title = {Synchronized tracking of brain cognitive processing using EEG and vision signals}, author = {Hak Soo Choi and Shinjung Kim and Donghoon Lee and Chang Seok Kim and Myung Yung Jeong}, url = {http://dx.doi.org/10.1080/05704928.2016.1166373}, doi = {10.1080/05704928.2016.1166373}, year = {2016}, date = {2016-01-01}, journal = {Applied Spectroscopy Reviews}, volume = {51}, number = {7-9}, pages = {592--602}, publisher = {Taylor & Francis}, abstract = {Many efforts have been made to understand the neural mechanisms of the human brain. However, visualization of human brain processing has been a main challenge in the field. It is still largely unknown how the human brain allocates attention to target objects while excluding unrelated information in a complex visual environment. Using simultaneous electroencephalogram and eye tracking measurements, in this study, we analyzed two brain regions separately to detect the brain wave activity during visual information processing. We observed an activation difference between sensory (P100) and cognitive (P300) processing, and the behavioral response was improved by providing valid cue-target location information. Furthermore, neural processing was evaluated according to the specific area of brain activation and eye movements during cognitive processing. Our results demonstrate the correlation between behavior performance and visual stimuli and suggest an advantage of combined paradigms for efficient visual information processing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Many efforts have been made to understand the neural mechanisms of the human brain. However, visualization of human brain processing has been a main challenge in the field. It is still largely unknown how the human brain allocates attention to target objects while excluding unrelated information in a complex visual environment. Using simultaneous electroencephalogram and eye tracking measurements, in this study, we analyzed two brain regions separately to detect the brain wave activity during visual information processing. We observed an activation difference between sensory (P100) and cognitive (P300) processing, and the behavioral response was improved by providing valid cue-target location information. Furthermore, neural processing was evaluated according to the specific area of brain activation and eye movements during cognitive processing. Our results demonstrate the correlation between behavior performance and visual stimuli and suggest an advantage of combined paradigms for efficient visual information processing. |
Hoseok Choi; Seho Lee; Jeyeon Lee; Kyeongran Min; Seokbeen Lim; Jinsick Park; Kyoung ha Ahn; In Young Kim; Kyoung-Min Lee; Dong Pyo Jang Long-term evaluation and feasibility study of the insulated screw electrode for ECoG recording Journal Article Journal of Neuroscience Methods, 308 , pp. 261–268, 2018. @article{Choi2018, title = {Long-term evaluation and feasibility study of the insulated screw electrode for ECoG recording}, author = {Hoseok Choi and Seho Lee and Jeyeon Lee and Kyeongran Min and Seokbeen Lim and Jinsick Park and Kyoung ha Ahn and In Young Kim and Kyoung-Min Lee and Dong Pyo Jang}, doi = {10.1016/j.jneumeth.2018.06.027}, year = {2018}, date = {2018-01-01}, journal = {Journal of Neuroscience Methods}, volume = {308}, pages = {261--268}, publisher = {Elsevier}, abstract = {Background: A screw-shaped electrode can offer a compromise between signal quality and invasiveness. However, the standard screw electrode can be vulnerable to electrical noise while directly contact with the skull or skin, and the feasibility and stability for chronic implantation in primate have not been fully evaluated. New Method: We designed a novel screw electrocorticogram (ECoG) electrode composed of three parts: recording electrode, insulator, and nut. The recording electrode was made of titanium with high biocompatibility and high electrical conductivity. Zirconia is used for insulator and nut to prevent electrical noise. Result: In computer simulations, the screw ECoG with insulator showed a significantly higher performance in signal acquisition compared to the condition without insulator. In a non-human primate, using screw ECoG, clear visual-evoked potential (VEP) waveforms were obtained, VEP components were reliably maintained, and the electrode's impedance was stable during the whole evaluation period. Moreover, it showed higher SNR and wider frequency band compared to the electroencephalogram (EEG). We also observed the screw ECoG has a higher sensitivity that captures different responses on various stimuli than the EEG. Comparison: The screw ECoG showed reliable electrical characteristic and biocompatibility for three months, that shows great promise for chronic implants. These results contrasted with previous reports that general screw electrode was only applicable for acute applications. Conclusion: The suggested electrode can offer whole-brain monitoring with high signal quality and minimal invasiveness. The screw ECoG can be used to provide more in-depth understanding, not only relationship between functional networks and cognitive behavior, but also pathomechanisms in brain diseases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: A screw-shaped electrode can offer a compromise between signal quality and invasiveness. However, the standard screw electrode can be vulnerable to electrical noise while directly contact with the skull or skin, and the feasibility and stability for chronic implantation in primate have not been fully evaluated. New Method: We designed a novel screw electrocorticogram (ECoG) electrode composed of three parts: recording electrode, insulator, and nut. The recording electrode was made of titanium with high biocompatibility and high electrical conductivity. Zirconia is used for insulator and nut to prevent electrical noise. Result: In computer simulations, the screw ECoG with insulator showed a significantly higher performance in signal acquisition compared to the condition without insulator. In a non-human primate, using screw ECoG, clear visual-evoked potential (VEP) waveforms were obtained, VEP components were reliably maintained, and the electrode's impedance was stable during the whole evaluation period. Moreover, it showed higher SNR and wider frequency band compared to the electroencephalogram (EEG). We also observed the screw ECoG has a higher sensitivity that captures different responses on various stimuli than the EEG. Comparison: The screw ECoG showed reliable electrical characteristic and biocompatibility for three months, that shows great promise for chronic implants. These results contrasted with previous reports that general screw electrode was only applicable for acute applications. Conclusion: The suggested electrode can offer whole-brain monitoring with high signal quality and minimal invasiveness. The screw ECoG can be used to provide more in-depth understanding, not only relationship between functional networks and cognitive behavior, but also pathomechanisms in brain diseases. |
Evy Cleeren; Cindy Casteels; Karolien Goffin; Peter Janssen; Wim Van Paesschen Ictal perfusion changes associated with seizure progression in the amygdala kindling model in the rhesus monkey Journal Article Epilepsia, 56 (9), pp. 1366–1375, 2015. @article{Cleeren2015, title = {Ictal perfusion changes associated with seizure progression in the amygdala kindling model in the rhesus monkey}, author = {Evy Cleeren and Cindy Casteels and Karolien Goffin and Peter Janssen and Wim {Van Paesschen}}, doi = {10.1111/epi.13077}, year = {2015}, date = {2015-01-01}, journal = {Epilepsia}, volume = {56}, number = {9}, pages = {1366--1375}, abstract = {OBJECTIVE: Amygdala kindling is a widely used animal model for studying mesial temporal lobe epileptogenesis. In the macaque monkey, electrical amygdala kindling develops slowly and provides an opportunity for investigating ictal perfusion changes during epileptogenesis. METHODS: Two rhesus monkeys were electrically kindled through chronically implanted electrodes in the right amygdala over a period of 16 and 17 months. Ictal perfusion single photon emission computed tomography (SPECT) imaging was performed during each of the four predefined clinical stages. RESULTS: Afterdischarge duration increased slowly over 477 days for monkey K and 515 days for monkey S (18 ± 8 s in stage I; 52 ± 13 s in stage IV). During this time, the animals progressed through four clinical stages ranging from interrupting ongoing behavior to bilateral convulsions. Ictal SPECT perfusion imaging showed well-localized but widely distributed regions of hyperperfusion and hypoperfusion, in both cortical and subcortical structures, at every seizure stage. A large portion of the ictal network was involved in the early stages of epileptogenesis and subsequently expanded over time as seizure severity evolved. SIGNIFICANCE: Our data indicate that the different mesial temporal lobe seizure types occur within a common network affecting several parts of the brain, and that seizure severity may be determined by seizure-induced epileptogenesis within a bihemispheric network that is implicated from the start of the process.}, keywords = {}, pubstate = {published}, tppubtype = {article} } OBJECTIVE: Amygdala kindling is a widely used animal model for studying mesial temporal lobe epileptogenesis. In the macaque monkey, electrical amygdala kindling develops slowly and provides an opportunity for investigating ictal perfusion changes during epileptogenesis. METHODS: Two rhesus monkeys were electrically kindled through chronically implanted electrodes in the right amygdala over a period of 16 and 17 months. Ictal perfusion single photon emission computed tomography (SPECT) imaging was performed during each of the four predefined clinical stages. RESULTS: Afterdischarge duration increased slowly over 477 days for monkey K and 515 days for monkey S (18 ± 8 s in stage I; 52 ± 13 s in stage IV). During this time, the animals progressed through four clinical stages ranging from interrupting ongoing behavior to bilateral convulsions. Ictal SPECT perfusion imaging showed well-localized but widely distributed regions of hyperperfusion and hypoperfusion, in both cortical and subcortical structures, at every seizure stage. A large portion of the ictal network was involved in the early stages of epileptogenesis and subsequently expanded over time as seizure severity evolved. SIGNIFICANCE: Our data indicate that the different mesial temporal lobe seizure types occur within a common network affecting several parts of the brain, and that seizure severity may be determined by seizure-induced epileptogenesis within a bihemispheric network that is implicated from the start of the process. |
Brian A Coffman; Piyadasa Kodituwakku; Elizabeth L Kodituwakku; Lucinda Romero; Nirupama Muniswamy Sharadamma; David Stone; Julia M Stephen Primary visual response (M100) delays in adolescents with FASD as measured with MEG Journal Article Human Brain Mapping, 34 (11), pp. 2852–2862, 2013. @article{Coffman2013, title = {Primary visual response (M100) delays in adolescents with FASD as measured with MEG}, author = {Brian A Coffman and Piyadasa Kodituwakku and Elizabeth L Kodituwakku and Lucinda Romero and Nirupama Muniswamy Sharadamma and David Stone and Julia M Stephen}, doi = {10.1002/hbm.22110}, year = {2013}, date = {2013-01-01}, journal = {Human Brain Mapping}, volume = {34}, number = {11}, pages = {2852--2862}, abstract = {Fetal alcohol spectrum disorders (FASD) are debilitating, with effects of prenatal alcohol exposure persisting into adolescence and adulthood. Complete characterization of FASD is crucial for the development of diagnostic tools and intervention techniques to decrease the high cost to individual families and society of this disorder. In this experiment, we investigated visual system deficits in adolescents (12-21 years) diagnosed with an FASD by measuring the latency of patients' primary visual M100 responses using MEG. We hypothesized that patients with FASD would demonstrate delayed primary visual responses compared to controls. M100 latencies were assessed both for FASD patients and age-matched healthy controls for stimuli presented at the fovea (central stimulus) and at the periphery (peripheral stimuli; left or right of the central stimulus) in a saccade task requiring participants to direct their attention and gaze to these stimuli. Source modeling was performed on visual responses to the central and peripheral stimuli and the latency of the first prominent peak (M100) in the occipital source timecourse was identified. The peak latency of the M100 responses were delayed in FASD patients for both stimulus types (central and peripheral), but the difference in latency of primary visual responses to central vs. peripheral stimuli was significant only in FASD patients, indicating that, while FASD patients' visual systems are impaired in general, this impairment is more pronounced in the periphery. These results suggest that basic sensory deficits in this population may contribute to sensorimotor integration deficits described previously in this disorder.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fetal alcohol spectrum disorders (FASD) are debilitating, with effects of prenatal alcohol exposure persisting into adolescence and adulthood. Complete characterization of FASD is crucial for the development of diagnostic tools and intervention techniques to decrease the high cost to individual families and society of this disorder. In this experiment, we investigated visual system deficits in adolescents (12-21 years) diagnosed with an FASD by measuring the latency of patients' primary visual M100 responses using MEG. We hypothesized that patients with FASD would demonstrate delayed primary visual responses compared to controls. M100 latencies were assessed both for FASD patients and age-matched healthy controls for stimuli presented at the fovea (central stimulus) and at the periphery (peripheral stimuli; left or right of the central stimulus) in a saccade task requiring participants to direct their attention and gaze to these stimuli. Source modeling was performed on visual responses to the central and peripheral stimuli and the latency of the first prominent peak (M100) in the occipital source timecourse was identified. The peak latency of the M100 responses were delayed in FASD patients for both stimulus types (central and peripheral), but the difference in latency of primary visual responses to central vs. peripheral stimuli was significant only in FASD patients, indicating that, while FASD patients' visual systems are impaired in general, this impairment is more pronounced in the periphery. These results suggest that basic sensory deficits in this population may contribute to sensorimotor integration deficits described previously in this disorder. |
Eleanor J Cole; Nick E Barraclough; Peter G Enticott Investigating mirror system (MS) activity in adults with ASD when inferring others' intentions using both TMS and EEG Journal Article Journal of Autism and Developmental Disorders, 48 (7), pp. 2350–2367, 2018. @article{Cole2018, title = {Investigating mirror system (MS) activity in adults with ASD when inferring others' intentions using both TMS and EEG}, author = {Eleanor J Cole and Nick E Barraclough and Peter G Enticott}, doi = {10.1007/s10803-018-3492-2}, year = {2018}, date = {2018-07-01}, journal = {Journal of Autism and Developmental Disorders}, volume = {48}, number = {7}, pages = {2350--2367}, publisher = {Springer US}, abstract = {ASD is associated with mentalizing deficits that may correspond with atypical mirror system (MS) activation. We investigated MS activity in adults with and without ASD when inferring others' intentions using TMS-induced motor evoked potentials (MEPs) and mu suppression measured by EEG. Autistic traits were measured for all participants. Our EEG data show, high levels of autistic traits predicted reduced right mu (8–10 Hz) suppression when mentalizing. Higher left mu (8–10 Hz) suppression was associated with superior mentalizing performances. Eye-tracking and TMS data showed no differences associated with autistic traits. Our data suggest ASD is associated with reduced right MS activity when mentalizing, TMS-induced MEPs and mu suppression measure different aspects of MS functioning and the MS is directly involved in inferring intentions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } ASD is associated with mentalizing deficits that may correspond with atypical mirror system (MS) activation. We investigated MS activity in adults with and without ASD when inferring others' intentions using TMS-induced motor evoked potentials (MEPs) and mu suppression measured by EEG. Autistic traits were measured for all participants. Our EEG data show, high levels of autistic traits predicted reduced right mu (8–10 Hz) suppression when mentalizing. Higher left mu (8–10 Hz) suppression was associated with superior mentalizing performances. Eye-tracking and TMS data showed no differences associated with autistic traits. Our data suggest ASD is associated with reduced right MS activity when mentalizing, TMS-induced MEPs and mu suppression measure different aspects of MS functioning and the MS is directly involved in inferring intentions. |
Thérèse Collins Visual target selection and motor planning define attentional enhancement at perceptual processing stages Journal Article Frontiers in Human Neuroscience, 4 , pp. 1–10, 2010. @article{Collins2010, title = {Visual target selection and motor planning define attentional enhancement at perceptual processing stages}, author = {Thér{è}se Collins}, url = {http://journal.frontiersin.org/article/10.3389/neuro.09.014.2010/abstract}, doi = {10.3389/neuro.09.014.2010}, year = {2010}, date = {2010-01-01}, journal = {Frontiers in Human Neuroscience}, volume = {4}, pages = {1--10}, abstract = {Extracting information from the visual field can be achieved by covertly orienting attention to different regions, or by making saccades to bring areas of interest onto the fovea. While much research has shown a link between covert attention and saccade preparation, the nature of that link remains a matter of dispute. Covert presaccadic orienting could result from target selection or from planning a motor act toward an object. We examined the contribution of visual target selection and motor preparation to attentional orienting in humans by dissociating these two habitually aligned processes with saccadic adaptation. Adaptation introduces a discrepancy between the visual target evoking a saccade and the motor metrics of that saccade, which, unbeknownst to the participant, brings the eyes to a different spatial location. We examined attentional orienting by recording event-related potentials (ERPs) to task-irrelevant visual probes flashed during saccade preparation at four equidistant locations including the visual target location and the upcoming motor endpoint. ERPs as early as 130-170 ms post-probe were modulated by attention at both the visual target and motor endpoint locations. These results indicate that both target selection and motor preparation determine the focus of spatial attention, resulting in enhanced processing of stimuli at early visual-perceptual stages.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Extracting information from the visual field can be achieved by covertly orienting attention to different regions, or by making saccades to bring areas of interest onto the fovea. While much research has shown a link between covert attention and saccade preparation, the nature of that link remains a matter of dispute. Covert presaccadic orienting could result from target selection or from planning a motor act toward an object. We examined the contribution of visual target selection and motor preparation to attentional orienting in humans by dissociating these two habitually aligned processes with saccadic adaptation. Adaptation introduces a discrepancy between the visual target evoking a saccade and the motor metrics of that saccade, which, unbeknownst to the participant, brings the eyes to a different spatial location. We examined attentional orienting by recording event-related potentials (ERPs) to task-irrelevant visual probes flashed during saccade preparation at four equidistant locations including the visual target location and the upcoming motor endpoint. ERPs as early as 130-170 ms post-probe were modulated by attention at both the visual target and motor endpoint locations. These results indicate that both target selection and motor preparation determine the focus of spatial attention, resulting in enhanced processing of stimuli at early visual-perceptual stages. |
Thérèse Collins; Pierre O Jacquet TMS over posterior parietal cortex disrupts trans-saccadic visual stability Journal Article Brain Stimulation, 11 (2), pp. 390–399, 2018. @article{Collins2018, title = {TMS over posterior parietal cortex disrupts trans-saccadic visual stability}, author = {Thér{è}se Collins and Pierre O Jacquet}, doi = {10.1016/j.brs.2017.11.019}, year = {2018}, date = {2018-01-01}, journal = {Brain Stimulation}, volume = {11}, number = {2}, pages = {390--399}, abstract = {Background: Saccadic eye movements change the retinal location of visual objects, but we do not experience the visual world as constantly moving, we perceive it as seamless and stable. This visual stability may be achieved by an internal or efference copy of each saccade that, combined with the retinal information, allows the visual system to cancel out or ignore the self-caused retinal motion. Objective: The current study investigated the underlying brain mechanisms responsible for visual stability in humans with online transcranial magnetic stimulation (TMS). Methods: We used two classic tasks that measure efference copy: the double-step task and the in-flight displacement task. The double-step task requires subjects to make two memory-guided saccades, the second of which depends on an accurate internal copy of the first. The in-flight displacement task requires subjects to report the relative location of a (possibly displaced) target across a saccade. In separate experimental sessions, subjects participated in each task while we delivered online 3-pulse TMS over frontal eye fields (FEF), posterior parietal cortex, or vertex. TMS was contingent on saccade execution. Results: Second saccades were not disrupted in the double-step task, but surprisingly, TMS over FEF modified the metrics of the ongoing saccade. Spatiotopic performance in the in-flight displacement task was altered following TMS over parietal cortex, but not FEF or vertex. Conclusion: These results suggest that TMS disrupted eye-centered position coding in the parietal cortex. Trans-saccadic correspondence, and visual stability, may therefore causally depend on parietal maps.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: Saccadic eye movements change the retinal location of visual objects, but we do not experience the visual world as constantly moving, we perceive it as seamless and stable. This visual stability may be achieved by an internal or efference copy of each saccade that, combined with the retinal information, allows the visual system to cancel out or ignore the self-caused retinal motion. Objective: The current study investigated the underlying brain mechanisms responsible for visual stability in humans with online transcranial magnetic stimulation (TMS). Methods: We used two classic tasks that measure efference copy: the double-step task and the in-flight displacement task. The double-step task requires subjects to make two memory-guided saccades, the second of which depends on an accurate internal copy of the first. The in-flight displacement task requires subjects to report the relative location of a (possibly displaced) target across a saccade. In separate experimental sessions, subjects participated in each task while we delivered online 3-pulse TMS over frontal eye fields (FEF), posterior parietal cortex, or vertex. TMS was contingent on saccade execution. Results: Second saccades were not disrupted in the double-step task, but surprisingly, TMS over FEF modified the metrics of the ongoing saccade. Spatiotopic performance in the in-flight displacement task was altered following TMS over parietal cortex, but not FEF or vertex. Conclusion: These results suggest that TMS disrupted eye-centered position coding in the parietal cortex. Trans-saccadic correspondence, and visual stability, may therefore causally depend on parietal maps. |
Joshua D Cosman; Kaleb A Lowe; Wolf Zinke; Geoffrey F Woodman; Jeffrey D Schall Prefrontal control of visual distraction Journal Article Current Biology, 28 (3), pp. 414–420, 2018. @article{Cosman2018, title = {Prefrontal control of visual distraction}, author = {Joshua D Cosman and Kaleb A Lowe and Wolf Zinke and Geoffrey F Woodman and Jeffrey D Schall}, doi = {10.1016/j.cub.2017.12.023}, year = {2018}, date = {2018-02-01}, journal = {Current Biology}, volume = {28}, number = {3}, pages = {414--420}, abstract = {Avoiding distraction by conspicuous but irrelevant stimuli is critical to accomplishing daily tasks. Regions of prefrontal cortex control attention by enhancing the representation of task-relevant information in sensory cortex, which can be measured in modulation of both single neurons and event-related electrical potentials (ERPs) on the cranial surface [1, 2]. When irrelevant information is particularly conspicuous, it can distract attention and interfere with the selection of behaviorally relevant information. Such distraction can be minimized via top-down control [3–5], but the cognitive and neural mechanisms giving rise to this control over distraction remain uncertain and debated [6–9]. Bridging neurophysiology to electrophysiology, we simultaneously recorded neurons in prefrontal cortex and ERPs over extrastriate visual cortex to track the processing of salient distractors during a visual search task. Critically, when the salient distractor was successfully ignored, but not otherwise, we observed robust suppression of salient distractor representations. Like target selection, the distractor suppression was observed in prefrontal cortex before it appeared over extrastriate cortical areas. Furthermore, all prefrontal neurons that showed suppression of the task-irrelevant distractor also contributed to selecting the target. This suggests a common prefrontal mechanism is responsible for both selecting task-relevant and suppressing task-irrelevant information in sensory cortex. Taken together, our results resolve a long-standing debate over the mechanisms that prevent distraction, and provide the first evidence directly linking suppressed neural firing in prefrontal cortex with surface ERP measures of distractor suppression.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Avoiding distraction by conspicuous but irrelevant stimuli is critical to accomplishing daily tasks. Regions of prefrontal cortex control attention by enhancing the representation of task-relevant information in sensory cortex, which can be measured in modulation of both single neurons and event-related electrical potentials (ERPs) on the cranial surface [1, 2]. When irrelevant information is particularly conspicuous, it can distract attention and interfere with the selection of behaviorally relevant information. Such distraction can be minimized via top-down control [3–5], but the cognitive and neural mechanisms giving rise to this control over distraction remain uncertain and debated [6–9]. Bridging neurophysiology to electrophysiology, we simultaneously recorded neurons in prefrontal cortex and ERPs over extrastriate visual cortex to track the processing of salient distractors during a visual search task. Critically, when the salient distractor was successfully ignored, but not otherwise, we observed robust suppression of salient distractor representations. Like target selection, the distractor suppression was observed in prefrontal cortex before it appeared over extrastriate cortical areas. Furthermore, all prefrontal neurons that showed suppression of the task-irrelevant distractor also contributed to selecting the target. This suggests a common prefrontal mechanism is responsible for both selecting task-relevant and suppressing task-irrelevant information in sensory cortex. Taken together, our results resolve a long-standing debate over the mechanisms that prevent distraction, and provide the first evidence directly linking suppressed neural firing in prefrontal cortex with surface ERP measures of distractor suppression. |
Michael Dambacher; Reinhold Kliegl Synchronizing timelines: Relations between fixation durations and N400 amplitudes during sentence reading Journal Article Brain Research, 1155 (1), pp. 147–162, 2007. @article{Dambacher2007, title = {Synchronizing timelines: Relations between fixation durations and N400 amplitudes during sentence reading}, author = {Michael Dambacher and Reinhold Kliegl}, doi = {10.1016/j.brainres.2007.04.027}, year = {2007}, date = {2007-01-01}, journal = {Brain Research}, volume = {1155}, number = {1}, pages = {147--162}, abstract = {We examined relations between eye movements (single-fixation durations) and RSVP-based event-related potentials (ERPs; N400s) recorded during reading the same sentences in two independent experiments. Longer fixation durations correlated with larger N400 amplitudes. Word frequency and predictability of the fixated word as well as the predictability of the upcoming word accounted for this covariance in a path-analytic model. Moreover, larger N400 amplitudes entailed longer fixation durations on the next word, a relation accounted for by word frequency. This pattern offers a neurophysiological correlate for the lag-word frequency effect on fixation durations: word processing is reliably expressed not only in fixation durations on currently fixated words, but also in those on subsequently fixated words.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We examined relations between eye movements (single-fixation durations) and RSVP-based event-related potentials (ERPs; N400s) recorded during reading the same sentences in two independent experiments. Longer fixation durations correlated with larger N400 amplitudes. Word frequency and predictability of the fixated word as well as the predictability of the upcoming word accounted for this covariance in a path-analytic model. Moreover, larger N400 amplitudes entailed longer fixation durations on the next word, a relation accounted for by word frequency. This pattern offers a neurophysiological correlate for the lag-word frequency effect on fixation durations: word processing is reliably expressed not only in fixation durations on currently fixated words, but also in those on subsequently fixated words. |
Sangita Dandekar; Claudio Privitera; Thom Carney; Stanley A Klein Neural saccadic response estimation during natural viewing Sangita Journal Article Journal of Neurophysiology, 107 (4), pp. 1776–1790, 2011. @article{Dandekar2011, title = {Neural saccadic response estimation during natural viewing Sangita}, author = {Sangita Dandekar and Claudio Privitera and Thom Carney and Stanley A Klein}, doi = {10.1111/j.1469-7998.1981.tb03488.x}, year = {2011}, date = {2011-01-01}, journal = {Journal of Neurophysiology}, volume = {107}, number = {4}, pages = {1776--1790}, abstract = {Studying neural activity during natural viewing conditions is not often attempted. Isolating the neural response of a single saccade is necessary to study neural activity during natural viewing; however, the close temporal spacing of saccades that occurs during natural viewing makes it difficult to determine the response to a single saccade. Herein, a general linear model (GLM) approach is applied to estimate the EEG neural saccadic response for different segments of the saccadic main sequence separately. It is determined that, in visual search conditions, neural responses estimated by conventional event-related averaging are significantly and systematically distorted relative to GLM estimates due to the close temporal spacing of saccades during visual search. Before the GLM is applied, analyses are applied that demonstrate that saccades during visual search with intersaccadic spacings as low as 100-150 ms do not exhibit significant refractory effects. Therefore, saccades displaying different intersaccadic spacings during visual search can be modeled using the same regressor in a GLM. With the use of the GLM approach, neural responses were separately estimated for five different ranges of saccade amplitudes during visual search. Occipital responses time locked to the onsets of saccades during visual search were found to account for, on average, 79 percent of the variance of EEG activity in a window 90-200 ms after the onsets of saccades for all five saccade amplitude ranges that spanned a range of 0.2-6.0 degrees. A GLM approach was also used to examine the lateralized ocular artifacts associated with saccades. Possible extensions of the methods presented here to account for the superposition of microsaccades in event-related EEG studies conducted in nominal fixation conditions are discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Studying neural activity during natural viewing conditions is not often attempted. Isolating the neural response of a single saccade is necessary to study neural activity during natural viewing; however, the close temporal spacing of saccades that occurs during natural viewing makes it difficult to determine the response to a single saccade. Herein, a general linear model (GLM) approach is applied to estimate the EEG neural saccadic response for different segments of the saccadic main sequence separately. It is determined that, in visual search conditions, neural responses estimated by conventional event-related averaging are significantly and systematically distorted relative to GLM estimates due to the close temporal spacing of saccades during visual search. Before the GLM is applied, analyses are applied that demonstrate that saccades during visual search with intersaccadic spacings as low as 100-150 ms do not exhibit significant refractory effects. Therefore, saccades displaying different intersaccadic spacings during visual search can be modeled using the same regressor in a GLM. With the use of the GLM approach, neural responses were separately estimated for five different ranges of saccade amplitudes during visual search. Occipital responses time locked to the onsets of saccades during visual search were found to account for, on average, 79 percent of the variance of EEG activity in a window 90-200 ms after the onsets of saccades for all five saccade amplitude ranges that spanned a range of 0.2-6.0 degrees. A GLM approach was also used to examine the lateralized ocular artifacts associated with saccades. Possible extensions of the methods presented here to account for the superposition of microsaccades in event-related EEG studies conducted in nominal fixation conditions are discussed. |
Sangita Dandekar; Jian Ding; Claudio Privitera; Thom Carney; Stanley A Klein The fixation and saccade P3 Journal Article PLoS ONE, 7 (11), pp. 1–14, 2012. @article{Dandekar2012, title = {The fixation and saccade P3}, author = {Sangita Dandekar and Jian Ding and Claudio Privitera and Thom Carney and Stanley A Klein}, doi = {10.1371/journal.pone.0048761}, year = {2012}, date = {2012-01-01}, journal = {PLoS ONE}, volume = {7}, number = {11}, pages = {1--14}, abstract = {Although most instances of object recognition during natural viewing occur in the presence of saccades, the neural correlates of objection recognition have almost exclusively been examined during fixation. Recent studies have indicated that there are post-saccadic modulations of neural activity immediately following eye movement landing; however, whether post-saccadic modulations affect relatively late occurring cognitive components such as the P3 has not been explored. The P3 as conventionally measured at fixation is commonly used in brain computer interfaces, hence characterizing the post-saccadic P3 could aid in the development of improved brain computer interfaces that allow for eye movements. In this study, the P3 observed after saccadic landing was compared to the P3 measured at fixation. No significant differences in P3 start time, temporal persistence, or amplitude were found between fixation and saccade trials. Importantly, sensory neural responses canceled in the target minus distracter comparisons used to identify the P3. Our results indicate that relatively late occurring cognitive neural components such as the P3 are likely less sensitive to post saccadic modulations than sensory neural components and other neural activity occurring shortly after eye movement landing. Furthermore, due to the similarity of the fixation and saccade P3, we conclude that the P3 following saccadic landing could possibly be used as a viable signal in brain computer interfaces allowing for eye movements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although most instances of object recognition during natural viewing occur in the presence of saccades, the neural correlates of objection recognition have almost exclusively been examined during fixation. Recent studies have indicated that there are post-saccadic modulations of neural activity immediately following eye movement landing; however, whether post-saccadic modulations affect relatively late occurring cognitive components such as the P3 has not been explored. The P3 as conventionally measured at fixation is commonly used in brain computer interfaces, hence characterizing the post-saccadic P3 could aid in the development of improved brain computer interfaces that allow for eye movements. In this study, the P3 observed after saccadic landing was compared to the P3 measured at fixation. No significant differences in P3 start time, temporal persistence, or amplitude were found between fixation and saccade trials. Importantly, sensory neural responses canceled in the target minus distracter comparisons used to identify the P3. Our results indicate that relatively late occurring cognitive neural components such as the P3 are likely less sensitive to post saccadic modulations than sensory neural components and other neural activity occurring shortly after eye movement landing. Furthermore, due to the similarity of the fixation and saccade P3, we conclude that the P3 following saccadic landing could possibly be used as a viable signal in brain computer interfaces allowing for eye movements. |
M Davare; A Zénon; G Pourtois; M Desmurget; E Olivier Role of the medial part of the intraparietal sulcus in implementing movement direction Journal Article Cerebral Cortex, 22 (6), pp. 1382–1394, 2012. @article{Davare2012, title = {Role of the medial part of the intraparietal sulcus in implementing movement direction}, author = {M Davare and A Zénon and G Pourtois and M Desmurget and E Olivier}, doi = {10.1093/cercor/bhr210}, year = {2012}, date = {2012-01-01}, journal = {Cerebral Cortex}, volume = {22}, number = {6}, pages = {1382--1394}, abstract = {The contribution of the posterior parietal cortex (PPC) to visually guided movements has been originally inferred from observations made in patients suffering from optic ataxia. Subsequent electrophysiological studies in monkeys and functional imaging data in humans have corroborated the key role played by the PPC in sensorimotor transformations underlying goal-directed movements, although the exact contribution of this structure remains debated. Here, we used transcranial magnetic stimulation (TMS) to interfere transiently with the function of the left or right medial part of the intraparietal sulcus (mIPS) in healthy volunteers performing visually guided movements with the right hand. We found that a "virtual lesion" of either mIPS increased the scattering in initial movement direction (DIR), leading to longer trajectory and prolonged movement time, but only when TMS was delivered 100-160 ms before movement onset and for movements directed toward contralateral targets. Control experiments showed that deficits in DIR consequent to mIPS virtual lesions resulted from an inappropriate implementation of the motor command underlying the forthcoming movement and not from an inaccurate computation of the target localization. The present study indicates that mIPS plays a causal role in implementing specifically the direction vector of visually guided movements toward objects situated in the contralateral hemifield.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The contribution of the posterior parietal cortex (PPC) to visually guided movements has been originally inferred from observations made in patients suffering from optic ataxia. Subsequent electrophysiological studies in monkeys and functional imaging data in humans have corroborated the key role played by the PPC in sensorimotor transformations underlying goal-directed movements, although the exact contribution of this structure remains debated. Here, we used transcranial magnetic stimulation (TMS) to interfere transiently with the function of the left or right medial part of the intraparietal sulcus (mIPS) in healthy volunteers performing visually guided movements with the right hand. We found that a "virtual lesion" of either mIPS increased the scattering in initial movement direction (DIR), leading to longer trajectory and prolonged movement time, but only when TMS was delivered 100-160 ms before movement onset and for movements directed toward contralateral targets. Control experiments showed that deficits in DIR consequent to mIPS virtual lesions resulted from an inappropriate implementation of the motor command underlying the forthcoming movement and not from an inaccurate computation of the target localization. The present study indicates that mIPS plays a causal role in implementing specifically the direction vector of visually guided movements toward objects situated in the contralateral hemifield. |
Ido Davidesco; Michal Harel; Michal Ramot; Uri Kramer; Svetlana Kipervasser; Fani Andelman; Miri Y Neufeld; Gadi Goelman; Itzhak Fried; Rafael Malach Spatial and object-based attention modulates broadband high-frequency responses across the human visual cortical hierarchy Journal Article Journal of Neuroscience, 33 (3), pp. 1228–1240, 2013. @article{Davidesco2013, title = {Spatial and object-based attention modulates broadband high-frequency responses across the human visual cortical hierarchy}, author = {Ido Davidesco and Michal Harel and Michal Ramot and Uri Kramer and Svetlana Kipervasser and Fani Andelman and Miri Y Neufeld and Gadi Goelman and Itzhak Fried and Rafael Malach}, doi = {10.1523/JNEUROSCI.3181-12.2013}, year = {2013}, date = {2013-01-01}, journal = {Journal of Neuroscience}, volume = {33}, number = {3}, pages = {1228--1240}, abstract = {One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation ofboth spatial and object-based attention. They were presented with composite stimuli, consisting ofa small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one ofthe objects. We found a consistent increase in broadband high-frequency (30–90Hz) power, but not in visual evoked potentials, associated with spatial attention starting withV1/V2 and continuing throughout the visual hierarchy. The magnitude ofthe attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation ofboth spatial and object-based attention. They were presented with composite stimuli, consisting ofa small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one ofthe objects. We found a consistent increase in broadband high-frequency (30–90Hz) power, but not in visual evoked potentials, associated with spatial attention starting withV1/V2 and continuing throughout the visual hierarchy. The magnitude ofthe attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties. |
Federica Degno; Otto Loberg; Chuanli Zang; Manman Zhang; Nick Donnelly; Simon P Liversedge Parafoveal previews and lexical frequency in natural reading: Evidence from eye movements and fixation-related potentials. Journal Article Journal of Experimental Psychology: General, 148 (3), pp. 453–474, 2019. @article{Degno2019, title = {Parafoveal previews and lexical frequency in natural reading: Evidence from eye movements and fixation-related potentials.}, author = {Federica Degno and Otto Loberg and Chuanli Zang and Manman Zhang and Nick Donnelly and Simon P Liversedge}, doi = {10.1037/xge0000494}, year = {2019}, date = {2019-01-01}, journal = {Journal of Experimental Psychology: General}, volume = {148}, number = {3}, pages = {453--474}, abstract = {Participants' eye movements and electroencephalogram (EEG) signal were recorded as they read sentences displayed according to the gaze-contingent boundary paradigm. Two target words in each sentence were manipulated for lexical frequency (high vs. low frequency) and parafoveal preview of each target word (identical vs. string of random letters vs. string of Xs). Eye movement data revealed visual parafoveal-on-foveal (PoF) effects, as well as foveal visual and orthographic preview effects and word frequency effects. Fixation-related potentials (FRPs) showed visual and orthographic PoF effects as well as foveal visual and orthographic preview effects. Our results replicated the early preview positivity effect (Dimigen, Kliegl, & Sommer, 2012) in the X-string preview condition, and revealed different neural correlates associated with a preview comprised of a string of random letters relative to a string of Xs. The former effects seem likely to reflect difficulty associated with the integration of parafoveal and foveal information, as well as feature overlap, while the latter reflect inhibition, and potentially disruption, to processing underlying reading. Interestingly, and consistent with Kretzschmar, Schlesewsky, and Staub (2015), no frequency effect was reflected in the FRP measures. The findings provide insight into the neural correlates of parafoveal processing and written word recognition in reading and demonstrate the value of utilizing ecologically valid paradigms to study well established phenomena that occur as text is read naturally.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Participants' eye movements and electroencephalogram (EEG) signal were recorded as they read sentences displayed according to the gaze-contingent boundary paradigm. Two target words in each sentence were manipulated for lexical frequency (high vs. low frequency) and parafoveal preview of each target word (identical vs. string of random letters vs. string of Xs). Eye movement data revealed visual parafoveal-on-foveal (PoF) effects, as well as foveal visual and orthographic preview effects and word frequency effects. Fixation-related potentials (FRPs) showed visual and orthographic PoF effects as well as foveal visual and orthographic preview effects. Our results replicated the early preview positivity effect (Dimigen, Kliegl, & Sommer, 2012) in the X-string preview condition, and revealed different neural correlates associated with a preview comprised of a string of random letters relative to a string of Xs. The former effects seem likely to reflect difficulty associated with the integration of parafoveal and foveal information, as well as feature overlap, while the latter reflect inhibition, and potentially disruption, to processing underlying reading. Interestingly, and consistent with Kretzschmar, Schlesewsky, and Staub (2015), no frequency effect was reflected in the FRP measures. The findings provide insight into the neural correlates of parafoveal processing and written word recognition in reading and demonstrate the value of utilizing ecologically valid paradigms to study well established phenomena that occur as text is read naturally. |
Sergio Delle Monache; Francesco Lacquaniti; Gianfranco Bosco Journal of Neurophysiology, 118 (3), pp. 1809–1823, 2017. @article{DelleMonache2017, title = {Differential contributions to the interception of occluded ballistic trajectories by the temporoparietal junction, area hMT/V5+, and the intraparietal cortex}, author = {Sergio {Delle Monache} and Francesco Lacquaniti and Gianfranco Bosco}, doi = {10.1152/jn.00068.2017}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neurophysiology}, volume = {118}, number = {3}, pages = {1809--1823}, abstract = {The ability to catch objects when tran- siently occluded from view suggests their motion can be extrapolated. Intraparietal cortex (IPS) plays a major role in this process along with other brain structures, depending on the task. For example, intercep- tion of objects under Earth's gravity effects may depend on time-to-contact predictions derived from integration of visual signals processed by hMT/V5⫹ with a priori knowledge of gravity residing in the temporoparietal junction (TPJ). To investigate this issue further, we disrupted TPJ, hMT/V5⫹, and IPS activities with transcranial magnetic stimulation (TMS) while subjects intercepted computer- simulated projectile trajectories perturbed randomly with either hypo- or hypergravity effects. In experiment 1, trajectories were occluded either 750 or 1,250 ms before landing. Three subject groups underwent triple-pulse TMS (tpTMS, 3 pulses at 10 Hz) on one target area (TPJ | hMT/V5⫹ | IPS) and on the vertex (control site), timed at either trajectory perturbation or occlusion. In experiment 2, trajectories were entirely visible and participants received tpTMS on TPJ and hMT/ V5+ with same timing as experiment 1. tpTMS of TPJ, hMT/V5⫹, and IPS affected differently the interceptive timing. TPJ stimulation affected preferentially responses to 1-g motion, hMT/V5+ all response types, and IPS stimulation induced opposite effects on 0-g and 2-g responses, being ineffective on 1-g responses. Only IPS stimulation was effective when applied after target disappearance, implying this area might elaborate memory representations of occluded target motion. Results are compatible with the idea that IPS, TPJ, and hMT/V5+ contribute to distinct aspects of visual motion extrapolation, perhaps through parallel processing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The ability to catch objects when tran- siently occluded from view suggests their motion can be extrapolated. Intraparietal cortex (IPS) plays a major role in this process along with other brain structures, depending on the task. For example, intercep- tion of objects under Earth's gravity effects may depend on time-to-contact predictions derived from integration of visual signals processed by hMT/V5⫹ with a priori knowledge of gravity residing in the temporoparietal junction (TPJ). To investigate this issue further, we disrupted TPJ, hMT/V5⫹, and IPS activities with transcranial magnetic stimulation (TMS) while subjects intercepted computer- simulated projectile trajectories perturbed randomly with either hypo- or hypergravity effects. In experiment 1, trajectories were occluded either 750 or 1,250 ms before landing. Three subject groups underwent triple-pulse TMS (tpTMS, 3 pulses at 10 Hz) on one target area (TPJ | hMT/V5⫹ | IPS) and on the vertex (control site), timed at either trajectory perturbation or occlusion. In experiment 2, trajectories were entirely visible and participants received tpTMS on TPJ and hMT/ V5+ with same timing as experiment 1. tpTMS of TPJ, hMT/V5⫹, and IPS affected differently the interceptive timing. TPJ stimulation affected preferentially responses to 1-g motion, hMT/V5+ all response types, and IPS stimulation induced opposite effects on 0-g and 2-g responses, being ineffective on 1-g responses. Only IPS stimulation was effective when applied after target disappearance, implying this area might elaborate memory representations of occluded target motion. Results are compatible with the idea that IPS, TPJ, and hMT/V5+ contribute to distinct aspects of visual motion extrapolation, perhaps through parallel processing. |
Gerard Derosiere; Pierre-Alexandre Klein; Sylvie Nozaradan; Alexandre Zénon; André Mouraux; Julie Duque Visuomotor correlates of conflict expectation in the context of motor decisions Journal Article Journal of Neuroscience, 38 (44), pp. 9486–9504, 2018. @article{Derosiere2018, title = {Visuomotor correlates of conflict expectation in the context of motor decisions}, author = {Gerard Derosiere and Pierre-Alexandre Klein and Sylvie Nozaradan and Alexandre Zénon and André Mouraux and Julie Duque}, doi = {10.1523/jneurosci.0623-18.2018}, year = {2018}, date = {2018-01-01}, journal = {Journal of Neuroscience}, volume = {38}, number = {44}, pages = {9486--9504}, abstract = {Many behaviors require choosing between conflicting options competing against each other in visuomotor areas. Such choices can benefit from top-down control processes engaging frontal areas in advance of conflict when it is anticipated. Yet, very little is known about how this proactive control system shapes the visuomotor competition. Here, we used electroencephalography in human subjects (male and female) to identify the visual and motor correlates of conflict expectation in a version ofthe Eriksen Flanker task that required left or right responses according to the direction of a central target arrow surrounded by congruent or incongruent (conflicting) flankers. Visual conflict was either highly expected (it occurred in 80% of trials; mostly incongruent blocks) or very unlikely (20% of trials; mostly congruent blocks). We evaluated selective attention in the visual cortex by recording target- and flanker-related steady-state visual- evoked potentials (SSVEPs) and probed action selection by measuring response-locked potentials (RLPs) in the motor cortex. Conflict expectation enhanced accuracy in incongruent trials, but this improvement occurred at the cost ofspeed in congruent trials. Intriguingly, this behavioral adjustment occurred while visuomotor activity was less finely tuned: target-related SSVEPs were smaller while flanker related SSVEPs were higher in mostly incongruent blocks than in mostly congruent blocks, and incongruent trials were associated with larger RLPs in the ipsilateral (nonselected) motor cortex. Hence, our data suggest that conflict expectation recruits control processes that augment the tolerance for inappropriate visuomotor activations (rather than processes that down regulate their amplitude), allowing for overflow activity to occur without having it turn into the selection of an incorrect response.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Many behaviors require choosing between conflicting options competing against each other in visuomotor areas. Such choices can benefit from top-down control processes engaging frontal areas in advance of conflict when it is anticipated. Yet, very little is known about how this proactive control system shapes the visuomotor competition. Here, we used electroencephalography in human subjects (male and female) to identify the visual and motor correlates of conflict expectation in a version ofthe Eriksen Flanker task that required left or right responses according to the direction of a central target arrow surrounded by congruent or incongruent (conflicting) flankers. Visual conflict was either highly expected (it occurred in 80% of trials; mostly incongruent blocks) or very unlikely (20% of trials; mostly congruent blocks). We evaluated selective attention in the visual cortex by recording target- and flanker-related steady-state visual- evoked potentials (SSVEPs) and probed action selection by measuring response-locked potentials (RLPs) in the motor cortex. Conflict expectation enhanced accuracy in incongruent trials, but this improvement occurred at the cost ofspeed in congruent trials. Intriguingly, this behavioral adjustment occurred while visuomotor activity was less finely tuned: target-related SSVEPs were smaller while flanker related SSVEPs were higher in mostly incongruent blocks than in mostly congruent blocks, and incongruent trials were associated with larger RLPs in the ipsilateral (nonselected) motor cortex. Hence, our data suggest that conflict expectation recruits control processes that augment the tolerance for inappropriate visuomotor activations (rather than processes that down regulate their amplitude), allowing for overflow activity to occur without having it turn into the selection of an incorrect response. |
Joost C Dessing; Michael Vesia; Douglas J Crawford The role of areas MT+/V5 and SPOC in spatial and temporal control of manual interception: An rTMS study Journal Article Frontiers in Behavioral Neuroscience, 7 , pp. 1–13, 2013. @article{Dessing2013, title = {The role of areas MT+/V5 and SPOC in spatial and temporal control of manual interception: An rTMS study}, author = {Joost C Dessing and Michael Vesia and Douglas J Crawford}, doi = {10.3389/fnbeh.2013.00015}, year = {2013}, date = {2013-01-01}, journal = {Frontiers in Behavioral Neuroscience}, volume = {7}, pages = {1--13}, abstract = {Manual interception, such as catching or hitting an approaching ball, requires the hand to contact a moving object at the right location and at the right time. Many studies have examined the neural mechanisms underlying the spatial aspects of goal-directed reaching, but the neural basis of the spatial and temporal aspects of manual interception are largely unknown. Here, we used repetitive transcranial magnetic stimulation (rTMS) to investigate the role of the human middle temporal visual motion area (MT+/V5) and superior parieto-occipital cortex (SPOC) in the spatial and temporal control of manual interception. Participants were required to reach-to-intercept a downward moving visual target that followed an unpredictably curved trajectory, presented on a screen in the vertical plane. We found that rTMS to MT+/V5 influenced interceptive timing and positioning, whereas rTMS to SPOC only tended to increase the spatial variance in reach end points for selected target trajectories. These findings are consistent with theories arguing that distinct neural mechanisms contribute to spatial, temporal, and spatiotemporal control of manual interception.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Manual interception, such as catching or hitting an approaching ball, requires the hand to contact a moving object at the right location and at the right time. Many studies have examined the neural mechanisms underlying the spatial aspects of goal-directed reaching, but the neural basis of the spatial and temporal aspects of manual interception are largely unknown. Here, we used repetitive transcranial magnetic stimulation (rTMS) to investigate the role of the human middle temporal visual motion area (MT+/V5) and superior parieto-occipital cortex (SPOC) in the spatial and temporal control of manual interception. Participants were required to reach-to-intercept a downward moving visual target that followed an unpredictably curved trajectory, presented on a screen in the vertical plane. We found that rTMS to MT+/V5 influenced interceptive timing and positioning, whereas rTMS to SPOC only tended to increase the spatial variance in reach end points for selected target trajectories. These findings are consistent with theories arguing that distinct neural mechanisms contribute to spatial, temporal, and spatiotemporal control of manual interception. |
Hélène Devillez; Nathalie Guyader; Anne Guérin-Dugué An eye fixation-related potentials analysis of the P300 potential for fixations onto a target object when exploring natural scenes Journal Article Journal of Vision, 15 (13), pp. 1–31, 2015. @article{Devillez2015, title = {An eye fixation-related potentials analysis of the P300 potential for fixations onto a target object when exploring natural scenes}, author = {Hél{è}ne Devillez and Nathalie Guyader and Anne Guérin-Dugué}, url = {http://jov.arvojournals.org/article.aspx?doi=10.1167/15.13.20}, doi = {10.1167/15.13.20}, year = {2015}, date = {2015-01-01}, journal = {Journal of Vision}, volume = {15}, number = {13}, pages = {1--31}, abstract = {The P300 event-related potential has been extensively studied in electroencephalography with classical paradigms that force observers to not move their eyes. This potential is classically used to infer whether a target or a task-relevant stimulus was presented. Few researches have studied this potential through more ecological paradigms where observers were able to move their eyes. In this study, we examined with an ecological paradigm and an adapted methodology the P300 potential using a visual search task that involves eye movements to actively explore natural scenes and during which eye movements and electroencephalographic activity were coregistered. Averaging the electroencephalography signal time-locked to fixation onsets, a P300 potential was observed for fixations onto the target object but not for other fixations recorded for the same visual search or for fixations recorded during the free viewing without any task. Our approach consists of using control experimental conditions with similar eye movements to ensure that the P300 potential was attributable to the fact that the observer gazed at the target rather than to other factors such as eye movement pattern (the size of the previous saccade) or the ‘‘overlap issue'' between the potentials elicited by two successive fixations. We also proposed to model the time overlap issue of the potentials elicited by consecutive fixations with various durations. Our results show that the P300 potential can be studied in ecological situations without any constraint on the type of visual exploration, with some precautions in the interpretation of results due to the overlap issue.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The P300 event-related potential has been extensively studied in electroencephalography with classical paradigms that force observers to not move their eyes. This potential is classically used to infer whether a target or a task-relevant stimulus was presented. Few researches have studied this potential through more ecological paradigms where observers were able to move their eyes. In this study, we examined with an ecological paradigm and an adapted methodology the P300 potential using a visual search task that involves eye movements to actively explore natural scenes and during which eye movements and electroencephalographic activity were coregistered. Averaging the electroencephalography signal time-locked to fixation onsets, a P300 potential was observed for fixations onto the target object but not for other fixations recorded for the same visual search or for fixations recorded during the free viewing without any task. Our approach consists of using control experimental conditions with similar eye movements to ensure that the P300 potential was attributable to the fact that the observer gazed at the target rather than to other factors such as eye movement pattern (the size of the previous saccade) or the ‘‘overlap issue'' between the potentials elicited by two successive fixations. We also proposed to model the time overlap issue of the potentials elicited by consecutive fixations with various durations. Our results show that the P300 potential can be studied in ecological situations without any constraint on the type of visual exploration, with some precautions in the interpretation of results due to the overlap issue. |
Joao C Dias; Paul Sajda; J P Dmochowski; Lucas C Parra EEG precursors of detected and missed targets during free-viewing search Journal Article Journal of Vision, 13 (13), pp. 1–19, 2013. @article{Dias2013, title = {EEG precursors of detected and missed targets during free-viewing search}, author = {Joao C Dias and Paul Sajda and J P Dmochowski and Lucas C Parra}, url = {http://jov.arvojournals.org/Article.aspx?doi=10.1167/13.13.13}, doi = {10.1167/13.13.13}, year = {2013}, date = {2013-01-01}, journal = {Journal of Vision}, volume = {13}, number = {13}, pages = {1--19}, abstract = {When scanning a scene, the target of our search may be in plain sight and yet remain unperceived. Conversely, at other times the target may be perceived in the periphery prior to fixation. There is ample behavioral and neurophysiological evidence to suggest that in some constrained visual-search tasks, targets are detected prior to fixational eye movements. However, limited human data are available during unconstrained search to determine the time course of detection, the brain areas involved, and the neural correlates of failures to detect a foveated target. Here, we recorded and analyzed electroencephalographic (EEG) activity during free-viewing visual search, varying the task difficulty to compare neural signatures for detected and unreported ("missed") targets. When carefully controlled to remove eye-movement-related potentials, saccade-locked EEG shows that: (a) "Easy" targets may be detected as early as 150 ms prior to foveation, as indicated by a premotor potential associated with a button response; (b) object-discriminating occipital activity emerges during the saccade to target; and (c) success and failures to detect a target are accompanied by a modulation in alpha-band power over fronto-central areas as well as altered saccade dynamics. Taken together, these data suggest that target detection during free viewing can begin prior to and continue during a saccade, with failure or success in reporting a target possibly resulting from inhibition or activation of fronto-central processing areas associated with saccade control.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When scanning a scene, the target of our search may be in plain sight and yet remain unperceived. Conversely, at other times the target may be perceived in the periphery prior to fixation. There is ample behavioral and neurophysiological evidence to suggest that in some constrained visual-search tasks, targets are detected prior to fixational eye movements. However, limited human data are available during unconstrained search to determine the time course of detection, the brain areas involved, and the neural correlates of failures to detect a foveated target. Here, we recorded and analyzed electroencephalographic (EEG) activity during free-viewing visual search, varying the task difficulty to compare neural signatures for detected and unreported ("missed") targets. When carefully controlled to remove eye-movement-related potentials, saccade-locked EEG shows that: (a) "Easy" targets may be detected as early as 150 ms prior to foveation, as indicated by a premotor potential associated with a button response; (b) object-discriminating occipital activity emerges during the saccade to target; and (c) success and failures to detect a target are accompanied by a modulation in alpha-band power over fronto-central areas as well as altered saccade dynamics. Taken together, these data suggest that target detection during free viewing can begin prior to and continue during a saccade, with failure or success in reporting a target possibly resulting from inhibition or activation of fronto-central processing areas associated with saccade control. |
Adele Diederich; Annette Schomburg; Marieke Van Vugt Fronto-central theta oscillations are related to oscillations in saccadic response times (SRT): An EEG and behavioral data analysis Journal Article PLoS ONE, 9 (11), pp. 1–14, 2014. @article{Diederich2014, title = {Fronto-central theta oscillations are related to oscillations in saccadic response times (SRT): An EEG and behavioral data analysis}, author = {Adele Diederich and Annette Schomburg and Marieke {Van Vugt}}, doi = {10.1371/journal.pone.0112974}, year = {2014}, date = {2014-01-01}, journal = {PLoS ONE}, volume = {9}, number = {11}, pages = {1--14}, abstract = {The phase reset hypothesis states that the phase of an ongoing neural oscillation, reflecting periodic fluctuations in neural activity between states of high and low excitability, can be shifted by the occurrence of a sensory stimulus so that the phase value become highly constant across trials (Schroeder et al., 2008). From EEG/MEG studies it has been hypothesized that coupled oscillatory activity in primary sensory cortices regulates multi sensory processing (Senkowski et al. 2008). We follow up on a study in which evidence of phase reset was found using a purely behavioral paradigm by including also EEG measures. In this paradigm, presentation of an auditory accessory stimulus was followed by a visual target with a stimulus-onset asynchrony (SOA) across a range from 0 to 404 ms in steps of 4 ms. This fine-grained stimulus presentation allowed us to do a spectral analysis on the mean SRT as a function of the SOA, which revealed distinct peak spectral components within a frequency range of 6 to 11 Hz with a modus of 7 Hz. The EEG analysis showed that the auditory stimulus caused a phase reset in 7-Hz brain oscillations in a widespread set of channels. Moreover, there was a significant difference in the average phase at which the visual target stimulus appeared between slow and fast SRT trials. This effect was evident in three different analyses, and occurred primarily in frontal and central electrodes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The phase reset hypothesis states that the phase of an ongoing neural oscillation, reflecting periodic fluctuations in neural activity between states of high and low excitability, can be shifted by the occurrence of a sensory stimulus so that the phase value become highly constant across trials (Schroeder et al., 2008). From EEG/MEG studies it has been hypothesized that coupled oscillatory activity in primary sensory cortices regulates multi sensory processing (Senkowski et al. 2008). We follow up on a study in which evidence of phase reset was found using a purely behavioral paradigm by including also EEG measures. In this paradigm, presentation of an auditory accessory stimulus was followed by a visual target with a stimulus-onset asynchrony (SOA) across a range from 0 to 404 ms in steps of 4 ms. This fine-grained stimulus presentation allowed us to do a spectral analysis on the mean SRT as a function of the SOA, which revealed distinct peak spectral components within a frequency range of 6 to 11 Hz with a modus of 7 Hz. The EEG analysis showed that the auditory stimulus caused a phase reset in 7-Hz brain oscillations in a widespread set of channels. Moreover, there was a significant difference in the average phase at which the visual target stimulus appeared between slow and fast SRT trials. This effect was evident in three different analyses, and occurred primarily in frontal and central electrodes. |
Rosanne M van Diepen; Lee M Miller; Ali Mazaheri; Joy J Geng The role of alpha activity in spatial and feature-based attention. Journal Article eNeuro, 3 (5), pp. 1–11, 2016. @article{Diepen2016, title = {The role of alpha activity in spatial and feature-based attention.}, author = {Rosanne M van Diepen and Lee M Miller and Ali Mazaheri and Joy J Geng}, url = {http://eneuro.sfn.org/cgi/doi/10.1523/ENEURO.0204-16.2016}, doi = {10.1523/ENEURO.0204-16.2016}, year = {2016}, date = {2016-01-01}, journal = {eNeuro}, volume = {3}, number = {5}, pages = {1--11}, abstract = {Modulations in alpha oscillations (?10 Hz) are typically studied in the context of anticipating upcoming stimuli. Alpha power decreases in sensory regions processing upcoming targets compared to regions processing distracting input, thereby likely facilitating processing of relevant information while suppressing irrelevant. In this electroencephalography study using healthy human volunteers, we examined whether modulations in alpha power also occur after the onset of a bilaterally presented target and distractor. Spatial attentionwasmanipulated through spatial cues and feature-based attention through adjusting the color-similarity of distractors to the target. Consistent with previous studies, we found that informative spatial cues induced a relative decrease of pretarget alpha power at occipital electrodes contralateral to the expected target location. Interestingly, this pattern reemerged relatively late (300–750 ms) after stimulus onset, suggesting that lateralized alpha reflects not only preparatory attention, but also ongoing attentive stimulus processing. Uninformative cues (i.e., conveying no information about the spatial location of the target) resulted in an interaction between spatial attention and feature-based attention in post-target alpha lateralization. When the target was paired with a low-similarity distractor, post-target alpha was lateralized (500–900 ms). Crucially, the lateralization was absent when target selection was ambig- uous because the distractor was highly similar to the target. Instead, during this condition, midfrontal theta was increased, indicative of reactive conflict resolution. Behaviorally, the degree of alpha lateralization was negatively correlated with the reaction time distraction cost induced by target–distractor similarity. These results suggest a pivotal role for poststimulus alpha lateralization in protecting sensory processing of target information.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Modulations in alpha oscillations (?10 Hz) are typically studied in the context of anticipating upcoming stimuli. Alpha power decreases in sensory regions processing upcoming targets compared to regions processing distracting input, thereby likely facilitating processing of relevant information while suppressing irrelevant. In this electroencephalography study using healthy human volunteers, we examined whether modulations in alpha power also occur after the onset of a bilaterally presented target and distractor. Spatial attentionwasmanipulated through spatial cues and feature-based attention through adjusting the color-similarity of distractors to the target. Consistent with previous studies, we found that informative spatial cues induced a relative decrease of pretarget alpha power at occipital electrodes contralateral to the expected target location. Interestingly, this pattern reemerged relatively late (300–750 ms) after stimulus onset, suggesting that lateralized alpha reflects not only preparatory attention, but also ongoing attentive stimulus processing. Uninformative cues (i.e., conveying no information about the spatial location of the target) resulted in an interaction between spatial attention and feature-based attention in post-target alpha lateralization. When the target was paired with a low-similarity distractor, post-target alpha was lateralized (500–900 ms). Crucially, the lateralization was absent when target selection was ambig- uous because the distractor was highly similar to the target. Instead, during this condition, midfrontal theta was increased, indicative of reactive conflict resolution. Behaviorally, the degree of alpha lateralization was negatively correlated with the reaction time distraction cost induced by target–distractor similarity. These results suggest a pivotal role for poststimulus alpha lateralization in protecting sensory processing of target information. |
Mithun Diwakar; Deborah L Harrington; Jun Maruta; Jamshid Ghajar; Fady El-Gabalawy; Laura Muzzatti; Maurizio Corbetta; Ming-xiong Xiong Huang; Roland R Lee Filling in the gaps: Anticipatory control of eye movements in chronic mild traumatic brain injury Journal Article NeuroImage: Clinical, 8 , pp. 210–223, 2015. @article{Diwakar2015, title = {Filling in the gaps: Anticipatory control of eye movements in chronic mild traumatic brain injury}, author = {Mithun Diwakar and Deborah L Harrington and Jun Maruta and Jamshid Ghajar and Fady El-Gabalawy and Laura Muzzatti and Maurizio Corbetta and Ming-xiong Xiong Huang and Roland R Lee}, url = {http://dx.doi.org/10.1016/j.nicl.2015.04.011}, doi = {10.1016/j.nicl.2015.04.011}, year = {2015}, date = {2015-01-01}, journal = {NeuroImage: Clinical}, volume = {8}, pages = {210--223}, publisher = {Elsevier B.V.}, abstract = {A barrier in the diagnosis of mild traumatic brain injury (mTBI) stems from the lack of measures that are adequately sensitive in detecting mild head injuries. MRI and CT are typically negative in mTBI patients with persistent symptoms of post-concussive syndrome (PCS), and characteristic difficulties in sustaining attention often go undetected on neuropsychological testing, which can be insensitive to momentary lapses in concentration. Conversely, visual tracking strongly depends on sustained attention over time and is impaired in chronic mTBI patients, especially when tracking an occluded target. This finding suggests deficient internal anticipatory control in mTBI, the neural underpinnings of which are poorly understood. The present study investigated the neuronal bases for deficient anticipatory control during visual tracking in 25 chronic mTBI patients with persistent PCS symptoms and 25 healthy control subjects. The task was performed while undergoing magnetoencephalography (MEG), which allowed us to examine whether neural dysfunction associated with anticipatory control deficits was due to altered alpha, beta, and/or gamma activity. Neuropsychological examinations characterized cognition in both groups. During MEG recordings, subjects tracked a predictably moving target that was either continuously visible or randomly occluded (gap condition). MEG source-imaging analyses tested for group differences in alpha, beta, and gamma frequency bands. The results showed executive functioning, information processing speed, and verbal memory deficits in the mTBI group. Visual tracking was impaired in the mTBI group only in the gap condition. Patients showed greater error than controls before and during target occlusion, and were slower to resynchronize with the target when it reappeared. Impaired tracking concurred with abnormal beta activity, which was suppressed in the parietal cortex, especially the right hemisphere, and enhanced in left caudate and frontaloral areas. Regional beta-amplitude demonstrated high classification accuracy (92%) compared to eye-tracking (65%) and neuropsychological variables (80%). These findings show that deficient internal anticipatory control in mTBI is associated with altered beta activity, which is remarkably sensitive given the heterogeneity of injuries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A barrier in the diagnosis of mild traumatic brain injury (mTBI) stems from the lack of measures that are adequately sensitive in detecting mild head injuries. MRI and CT are typically negative in mTBI patients with persistent symptoms of post-concussive syndrome (PCS), and characteristic difficulties in sustaining attention often go undetected on neuropsychological testing, which can be insensitive to momentary lapses in concentration. Conversely, visual tracking strongly depends on sustained attention over time and is impaired in chronic mTBI patients, especially when tracking an occluded target. This finding suggests deficient internal anticipatory control in mTBI, the neural underpinnings of which are poorly understood. The present study investigated the neuronal bases for deficient anticipatory control during visual tracking in 25 chronic mTBI patients with persistent PCS symptoms and 25 healthy control subjects. The task was performed while undergoing magnetoencephalography (MEG), which allowed us to examine whether neural dysfunction associated with anticipatory control deficits was due to altered alpha, beta, and/or gamma activity. Neuropsychological examinations characterized cognition in both groups. During MEG recordings, subjects tracked a predictably moving target that was either continuously visible or randomly occluded (gap condition). MEG source-imaging analyses tested for group differences in alpha, beta, and gamma frequency bands. The results showed executive functioning, information processing speed, and verbal memory deficits in the mTBI group. Visual tracking was impaired in the mTBI group only in the gap condition. Patients showed greater error than controls before and during target occlusion, and were slower to resynchronize with the target when it reappeared. Impaired tracking concurred with abnormal beta activity, which was suppressed in the parietal cortex, especially the right hemisphere, and enhanced in left caudate and frontaloral areas. Regional beta-amplitude demonstrated high classification accuracy (92%) compared to eye-tracking (65%) and neuropsychological variables (80%). These findings show that deficient internal anticipatory control in mTBI is associated with altered beta activity, which is remarkably sensitive given the heterogeneity of injuries. |
Peter H Donaldson; Caroline Gurvich; Joanne Fielding; Peter G Enticott Exploring associations between gaze patterns and putative human mirror neuron system activity Journal Article Frontiers in Human Neuroscience, 9 , pp. 1–10, 2015. @article{Donaldson2015, title = {Exploring associations between gaze patterns and putative human mirror neuron system activity}, author = {Peter H Donaldson and Caroline Gurvich and Joanne Fielding and Peter G Enticott}, url = {http://journal.frontiersin.org/Article/10.3389/fnhum.2015.00523/abstract}, doi = {10.3389/fnhum.2015.00523}, year = {2015}, date = {2015-01-01}, journal = {Frontiers in Human Neuroscience}, volume = {9}, pages = {1--10}, abstract = {The human mirror neuron system (MNS) is hypothesized to be crucial to social cognition. Given that key MNS-input regions such as the superior temporal sulcus are involved in biological motion processing, and mirror neuron activity in monkeys has been shown to vary with visual attention, aberrant MNS function may be partly attributable to atypical visual input. To examine the relationship between gaze pattern and interpersonal motor resonance (IMR; an index of putative MNS activity), healthy right-handed participants aged 18–40 (n = 26) viewed videos of transitive grasping actions or static hands, whilst the left primary motor cortex received transcranial magnetic stimulation. Motor- evoked potentials recorded in contralateral hand muscles were used to determine IMR. Participants also underwent eyetracking analysis to assess gaze patterns whilst viewing the same videos. No relationship was observed between predictive gaze and IMR. However, IMR was positively associated with fixation counts in areas of biological motion in the videos, and negatively associated with object areas. These findings are discussed with reference to visual influences on the MNS, and the possibility that MNS atypicalities might be influenced by visual processes such as aberrant gaze pattern.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The human mirror neuron system (MNS) is hypothesized to be crucial to social cognition. Given that key MNS-input regions such as the superior temporal sulcus are involved in biological motion processing, and mirror neuron activity in monkeys has been shown to vary with visual attention, aberrant MNS function may be partly attributable to atypical visual input. To examine the relationship between gaze pattern and interpersonal motor resonance (IMR; an index of putative MNS activity), healthy right-handed participants aged 18–40 (n = 26) viewed videos of transitive grasping actions or static hands, whilst the left primary motor cortex received transcranial magnetic stimulation. Motor- evoked potentials recorded in contralateral hand muscles were used to determine IMR. Participants also underwent eyetracking analysis to assess gaze patterns whilst viewing the same videos. No relationship was observed between predictive gaze and IMR. However, IMR was positively associated with fixation counts in areas of biological motion in the videos, and negatively associated with object areas. These findings are discussed with reference to visual influences on the MNS, and the possibility that MNS atypicalities might be influenced by visual processes such as aberrant gaze pattern. |
Grace Edwards; Céline Paeye; Philippe Marque; Rufin VanRullen; Patrick Cavanagh Predictive position computations mediated by parietal areas: TMS evidence Journal Article NeuroImage, 153 , pp. 49–57, 2017. @article{Edwards2017, title = {Predictive position computations mediated by parietal areas: TMS evidence}, author = {Grace Edwards and Céline Paeye and Philippe Marque and Rufin VanRullen and Patrick Cavanagh}, doi = {10.1016/j.neuroimage.2017.03.043}, year = {2017}, date = {2017-01-01}, journal = {NeuroImage}, volume = {153}, pages = {49--57}, abstract = {When objects move or the eyes move, the visual system can predict the consequence and generate a percept of the target at its new position. This predictive localization may depend on eye movement control in the frontal eye fields (FEF) and the intraparietal sulcus (IPS) and on motion analysis in the medial temporal area (MT). Across two experiments we examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, right MT, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion, both presented in the contralateral visual field. In trans-saccadic fusion trials, participants saccade toward a stimulus that is replaced with another stimulus during the saccade. Frequently, predictive position mechanisms lead to a fused percept of pre- and post-saccade stimuli (Paeye et al., 2017). We found that rTMS to IPS significantly decreased the frequency of perceiving trans-saccadic fusion within the first 10 min after stimulation. In the flash grab illusion, a target is flashed on a moving background leading to the percept that the target has shifted in the direction of the motion after the flash (Cavanagh and Anstis, 2013). In the first experiment, the reduction in the flash grab illusion after rTMS to IPS and FEF did not reach significance. In the second experiment, using a stronger version of the flash grab, the illusory shift did decrease significantly after rTMS to IPS although not after rTMS to FEF or to MT. These findings suggest that right IPS contributes to predictive position perception during saccades and motion processing in the contralateral visual field.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When objects move or the eyes move, the visual system can predict the consequence and generate a percept of the target at its new position. This predictive localization may depend on eye movement control in the frontal eye fields (FEF) and the intraparietal sulcus (IPS) and on motion analysis in the medial temporal area (MT). Across two experiments we examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, right MT, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion, both presented in the contralateral visual field. In trans-saccadic fusion trials, participants saccade toward a stimulus that is replaced with another stimulus during the saccade. Frequently, predictive position mechanisms lead to a fused percept of pre- and post-saccade stimuli (Paeye et al., 2017). We found that rTMS to IPS significantly decreased the frequency of perceiving trans-saccadic fusion within the first 10 min after stimulation. In the flash grab illusion, a target is flashed on a moving background leading to the percept that the target has shifted in the direction of the motion after the flash (Cavanagh and Anstis, 2013). In the first experiment, the reduction in the flash grab illusion after rTMS to IPS and FEF did not reach significance. In the second experiment, using a stronger version of the flash grab, the illusory shift did decrease significantly after rTMS to IPS although not after rTMS to FEF or to MT. These findings suggest that right IPS contributes to predictive position perception during saccades and motion processing in the contralateral visual field. |
Grace Edwards; Rufin VanRullen; Patrick Cavanagh Decoding trans-saccadic memory Journal Article Journal of Neuroscience, 38 (5), pp. 1114–1123, 2018. @article{Edwards2018, title = {Decoding trans-saccadic memory}, author = {Grace Edwards and Rufin VanRullen and Patrick Cavanagh}, doi = {10.1523/jneurosci.0854-17.2017}, year = {2018}, date = {2018-01-01}, journal = {Journal of Neuroscience}, volume = {38}, number = {5}, pages = {1114--1123}, abstract = {We examine whether peripheral information at a planned saccade target affects immediate post-saccadic processing at the fovea on saccade landing. Current neuroimaging research suggests that pre-saccadic stimulation has a late effect on post-saccadic processing, in contrast to the early effect seen in behavioral studies. Human participants (both male and female) were instructed to saccade toward a face or a house that, on different trials, remained the same, changed, or disappeared during the saccade. We used a multivariate pattern analysis (MVPA) of electroencephalography (EEG) data to decode face versus house processing directly after the saccade. The classifier was trained on separate trials without a saccade, where a house or face was presented at the fovea. When the saccade target remained the same across the saccade, we could reliably decode the target 123 ms after saccade offset. In contrast, when the target was changed during the saccade, the new target was decoded at a later time-point, 151 ms after saccade offset. The "same" condition advantage suggests that congruent pre-saccadic information facilitates processing of the post-saccadic stimulus compared to incongruent information. Finally, the saccade target could be decoded above chance even when it had been removed during the saccade, albeit with a slower time-course (162 ms) and poorer signal strength. These findings indicate that information about the (peripheral) pre-saccadic stimulus is transferred across the saccade so that it becomes quickly available and influences processing at its expected, new retinal position (the fovea).}, keywords = {}, pubstate = {published}, tppubtype = {article} } We examine whether peripheral information at a planned saccade target affects immediate post-saccadic processing at the fovea on saccade landing. Current neuroimaging research suggests that pre-saccadic stimulation has a late effect on post-saccadic processing, in contrast to the early effect seen in behavioral studies. Human participants (both male and female) were instructed to saccade toward a face or a house that, on different trials, remained the same, changed, or disappeared during the saccade. We used a multivariate pattern analysis (MVPA) of electroencephalography (EEG) data to decode face versus house processing directly after the saccade. The classifier was trained on separate trials without a saccade, where a house or face was presented at the fovea. When the saccade target remained the same across the saccade, we could reliably decode the target 123 ms after saccade offset. In contrast, when the target was changed during the saccade, the new target was decoded at a later time-point, 151 ms after saccade offset. The "same" condition advantage suggests that congruent pre-saccadic information facilitates processing of the post-saccadic stimulus compared to incongruent information. Finally, the saccade target could be decoded above chance even when it had been removed during the saccade, albeit with a slower time-course (162 ms) and poorer signal strength. These findings indicate that information about the (peripheral) pre-saccadic stimulus is transferred across the saccade so that it becomes quickly available and influences processing at its expected, new retinal position (the fovea). |
John M Egan; Gerard M Loughnane; Helen Fletcher; Emma Meade; Edmund C Lalor A gaze independent hybrid-BCI based on visual spatial attention Journal Article Journal of Neural Engineering, 14 (4), pp. 1–8, 2017. @article{Egan2017, title = {A gaze independent hybrid-BCI based on visual spatial attention}, author = {John M Egan and Gerard M Loughnane and Helen Fletcher and Emma Meade and Edmund C Lalor}, doi = {10.1088/1741-2552/aa6bb2}, year = {2017}, date = {2017-01-01}, journal = {Journal of Neural Engineering}, volume = {14}, number = {4}, pages = {1--8}, publisher = {IOP Publishing}, abstract = {Objective. Brain-computer interfaces (BCI) use measures of brain activity to convey a user's intent without the need for muscle movement. Hybrid designs, which use multiple measures of brain activity, have been shown to increase the accuracy of BCIs, including those based on EEG signals reflecting covert attention. Our study examined whether incorporating a measure of the P3 response improved the performance of a previously reported attention-based BCI design that incorporates measures of steady-state visual evoked potentials (SSVEP) and alpha band modulations. Approach. Subjects viewed stimuli consisting of two bi-laterally located flashing white boxes on a black background. Streams of letters were presented sequentially within the boxes, in random order. Subjects were cued to attend to one of the boxes without moving their eyes, and they were tasked with counting the number of target-letters that appeared within. P3 components evoked by target appearance, SSVEPs evoked by the flashing boxes, and power in the alpha band are modulated by covert attention, and the modulations can be used to classify trials as left-attended or right-attended. Main Results. We showed that classification accuracy was improved by including a P3 feature along with the SSVEP and alpha features (the inclusion of a P3 feature lead to a 9% increase in accuracy compared to the use of SSVEP and Alpha features alone). We also showed that the design improves the robustness of BCI performance to individual subject differences. Significance. These results demonstrate that incorporating multiple neurophysiological indices of covert attention can improve performance in a gaze-independent BCI.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objective. Brain-computer interfaces (BCI) use measures of brain activity to convey a user's intent without the need for muscle movement. Hybrid designs, which use multiple measures of brain activity, have been shown to increase the accuracy of BCIs, including those based on EEG signals reflecting covert attention. Our study examined whether incorporating a measure of the P3 response improved the performance of a previously reported attention-based BCI design that incorporates measures of steady-state visual evoked potentials (SSVEP) and alpha band modulations. Approach. Subjects viewed stimuli consisting of two bi-laterally located flashing white boxes on a black background. Streams of letters were presented sequentially within the boxes, in random order. Subjects were cued to attend to one of the boxes without moving their eyes, and they were tasked with counting the number of target-letters that appeared within. P3 components evoked by target appearance, SSVEPs evoked by the flashing boxes, and power in the alpha band are modulated by covert attention, and the modulations can be used to classify trials as left-attended or right-attended. Main Results. We showed that classification accuracy was improved by including a P3 feature along with the SSVEP and alpha features (the inclusion of a P3 feature lead to a 9% increase in accuracy compared to the use of SSVEP and Alpha features alone). We also showed that the design improves the robustness of BCI performance to individual subject differences. Significance. These results demonstrate that incorporating multiple neurophysiological indices of covert attention can improve performance in a gaze-independent BCI. |
B V Ehinger; P Konig; José P Ossandón Predictions of visual content across eye movements and their modulation by inferred information Journal Article Journal of Neuroscience, 35 (19), pp. 7403–7413, 2015. @article{Ehinger2015, title = {Predictions of visual content across eye movements and their modulation by inferred information}, author = {B V Ehinger and P Konig and José P Ossandón}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.5114-14.2015}, doi = {10.1523/JNEUROSCI.5114-14.2015}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neuroscience}, volume = {35}, number = {19}, pages = {7403--7413}, abstract = {The brain is proposed to operate through probabilistic inference, testing and refining predictions about the world. Here, we search for neural activity compatible with the violation of active predictions, learned from the contingencies between actions and the consequent changes in sensory input. We focused on vision, where eye movements produce stimuli shifts that could, in principle, be predicted. We compared, in humans, error signals to saccade-contingent changes of veridical and inferred inputs by contrasting the electroencephalographic activity after saccades to a stimulus presented inside or outside the blind spot. We observed early (textless250 ms) and late (textgreater250 ms) error signals after stimulus change, indicating the violation of sensory and associative predictions, respectively. Remarkably, the late response was diminished for blind-spot trials. These results indicate that predictive signals occur across multiple levels of the visual hierarchy, based on generative models that differentiate between signals that originate from the outside world and those that are inferred.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The brain is proposed to operate through probabilistic inference, testing and refining predictions about the world. Here, we search for neural activity compatible with the violation of active predictions, learned from the contingencies between actions and the consequent changes in sensory input. We focused on vision, where eye movements produce stimuli shifts that could, in principle, be predicted. We compared, in humans, error signals to saccade-contingent changes of veridical and inferred inputs by contrasting the electroencephalographic activity after saccades to a stimulus presented inside or outside the blind spot. We observed early (textless250 ms) and late (textgreater250 ms) error signals after stimulus change, indicating the violation of sensory and associative predictions, respectively. Remarkably, the late response was diminished for blind-spot trials. These results indicate that predictive signals occur across multiple levels of the visual hierarchy, based on generative models that differentiate between signals that originate from the outside world and those that are inferred. |
Tomer Fekete; Felix D C C Beacher; Jiook Cha; Denis Rubin; Lilianne R Mujica-Parodi Small-world network properties in prefrontal cortex correlate with predictors of psychopathology risk in young children: A NIRS study Journal Article NeuroImage, 85 , pp. 345–353, 2014. @article{Fekete2014, title = {Small-world network properties in prefrontal cortex correlate with predictors of psychopathology risk in young children: A NIRS study}, author = {Tomer Fekete and Felix D C C Beacher and Jiook Cha and Denis Rubin and Lilianne R Mujica-Parodi}, url = {http://www.embase.com/search/results?subaction=viewrecord&from=export&id=L52701783%0Ahttp://dx.doi.org/10.1016/j.neuroimage.2013.07.022%0Ahttp://sfx.nelliportaali.fi/nelli30b?sid=EMBASE&wobble=10538119&id=doi:10.1016%2Fj.neuroimage.2013.07.022&atitle=Small-}, doi = {10.1016/j.neuroimage.2013.07.022}, year = {2014}, date = {2014-01-01}, journal = {NeuroImage}, volume = {85}, pages = {345--353}, publisher = {4}, address = {// Age}, abstract = {Near infrared spectroscopy (NIRS) is an emerging imaging technique that is relatively inexpensive, portable, and particularly well suited for collecting data in ecological settings. Therefore, it holds promise as a potential neurodiagnostic for young children. We set out to explore whether NIRS could be utilized in assessing the risk of developmental psychopathology in young children. A growing body of work indicates that temperament at young age is associated with vulnerability to psychopathology later on in life. In particular, it has been shown that low effortful control (EC), which includes the focusing and shifting of attention, inhibitory control, perceptual sensitivity, and a low threshold for pleasure, is linked to conditions such as anxiety, depression and attention deficit hyperactivity disorder (ADHD). Physiologically, EC has been linked to a control network spanning among other sites the prefrontal cortex. Several psychopathologies, such as depression and ADHD, have been shown to result in compromised small-world network properties. Therefore we set out to explore the relationship between EC and the small-world properties of PFC using NIRS. NIRS data were collected from 44 toddlers, ages 3-5, while watching naturalistic stimuli (movie clips). Derived complex network measures were then correlated to EC as derived from the Children's Behavior Questionnaire (CBQ). We found that reduced levels of EC were associated with compromised small-world properties of the prefrontal network. Our results suggest that the longitudinal NIRS studies of complex network properties in young children hold promise in furthering our understanding of developmental psychopathology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Near infrared spectroscopy (NIRS) is an emerging imaging technique that is relatively inexpensive, portable, and particularly well suited for collecting data in ecological settings. Therefore, it holds promise as a potential neurodiagnostic for young children. We set out to explore whether NIRS could be utilized in assessing the risk of developmental psychopathology in young children. A growing body of work indicates that temperament at young age is associated with vulnerability to psychopathology later on in life. In particular, it has been shown that low effortful control (EC), which includes the focusing and shifting of attention, inhibitory control, perceptual sensitivity, and a low threshold for pleasure, is linked to conditions such as anxiety, depression and attention deficit hyperactivity disorder (ADHD). Physiologically, EC has been linked to a control network spanning among other sites the prefrontal cortex. Several psychopathologies, such as depression and ADHD, have been shown to result in compromised small-world network properties. Therefore we set out to explore the relationship between EC and the small-world properties of PFC using NIRS. NIRS data were collected from 44 toddlers, ages 3-5, while watching naturalistic stimuli (movie clips). Derived complex network measures were then correlated to EC as derived from the Children's Behavior Questionnaire (CBQ). We found that reduced levels of EC were associated with compromised small-world properties of the prefrontal network. Our results suggest that the longitudinal NIRS studies of complex network properties in young children hold promise in furthering our understanding of developmental psychopathology. |
I C Fiebelkorn; A C Snyder; M R Mercier; J S Butler; S Molholm; J J Foxe Cortical cross-frequency coupling predicts perceptual outcomes Journal Article NeuroImage, 69 , pp. 126–137, 2013. @article{Fiebelkorn2013, title = {Cortical cross-frequency coupling predicts perceptual outcomes}, author = {I C Fiebelkorn and A C Snyder and M R Mercier and J S Butler and S Molholm and J J Foxe}, url = {http://dx.doi.org/10.1016/j.neuroimage.2012.11.021}, doi = {10.1016/j.neuroimage.2012.11.021}, year = {2013}, date = {2013-01-01}, journal = {NeuroImage}, volume = {69}, pages = {126--137}, publisher = {Elsevier Inc.}, abstract = {Functional networks are comprised of neuronal ensembles bound through synchronization across multiple intrinsic oscillatory frequencies. Various coupled interactions between brain oscillators have been described (e.g., phase-amplitude coupling), but with little evidence that these interactions actually influence perceptual sensitivity. Here, electroencephalographic (EEG) recordings were made during a sustained-attention task to demonstrate that cross-frequency coupling has significant consequences for perceptual outcomes (i.e., whether participants detect a near-threshold visual target). The data reveal that phase-detection relationships at higher frequencies are dependent on the phase of lower frequencies, such that higher frequencies alternate between periods when their phase is either strongly or weakly predictive of visual-target detection. Moreover, the specific higher frequencies and scalp topographies linked to visual-target detection also alternate as a function of lower-frequency phase. Cross-frequency coupling between lower (i.e., delta and theta) and higher frequencies (e.g., low- and high-beta) thus results in dramatic fluctuations of visual-target detection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Functional networks are comprised of neuronal ensembles bound through synchronization across multiple intrinsic oscillatory frequencies. Various coupled interactions between brain oscillators have been described (e.g., phase-amplitude coupling), but with little evidence that these interactions actually influence perceptual sensitivity. Here, electroencephalographic (EEG) recordings were made during a sustained-attention task to demonstrate that cross-frequency coupling has significant consequences for perceptual outcomes (i.e., whether participants detect a near-threshold visual target). The data reveal that phase-detection relationships at higher frequencies are dependent on the phase of lower frequencies, such that higher frequencies alternate between periods when their phase is either strongly or weakly predictive of visual-target detection. Moreover, the specific higher frequencies and scalp topographies linked to visual-target detection also alternate as a function of lower-frequency phase. Cross-frequency coupling between lower (i.e., delta and theta) and higher frequencies (e.g., low- and high-beta) thus results in dramatic fluctuations of visual-target detection. |
Ruth Filik; Hartmut Leuthold; Katie Wallington; Jemma Page Testing theories of irony processing using eye-tracking and ERPs Journal Article Journal of Experimental Psychology: Learning, Memory, and Cognition, 40 (3), pp. 811–828, 2014. @article{Filik2014, title = {Testing theories of irony processing using eye-tracking and ERPs}, author = {Ruth Filik and Hartmut Leuthold and Katie Wallington and Jemma Page}, doi = {10.1037/a0035658}, year = {2014}, date = {2014-01-01}, journal = {Journal of Experimental Psychology: Learning, Memory, and Cognition}, volume = {40}, number = {3}, pages = {811--828}, abstract = {Not much is known about how people comprehend ironic utterances, and to date, most studies have simply compared processing of ironic versus non-ironic statements. A key aspect of the graded salience hypothesis, distinguishing it from other accounts (such as the standard pragmatic view and direct access view), is that it predicts differences between processing of familiar and unfamiliar ironies. Specifically, if an ironic utterance is familiar, then the ironic interpretation should be available without the need for extra inferential processes, whereas for unfamiliar ironies, the literal interpretation would be computed first, and a mismatch with context would lead to a re-interpretation of the statement as being ironic. We recorded participants' eye movements while they were reading (Experiment 1), and electrical brain activity while they were listening to (Experiment 2), familiar and unfamiliar ironies compared to non-ironic controls. Results show disruption to eye movements and an N400-like effect for unfamiliar ironies only, supporting the predictions of the graded salience hypothesis. In addition, in Experiment 2, a late positivity was found for both familiar and unfamiliar ironic materials, compared to non-ironic controls. We interpret this positivity as reflecting ongoing conflict between the literal and ironic interpretations of the utterance.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Not much is known about how people comprehend ironic utterances, and to date, most studies have simply compared processing of ironic versus non-ironic statements. A key aspect of the graded salience hypothesis, distinguishing it from other accounts (such as the standard pragmatic view and direct access view), is that it predicts differences between processing of familiar and unfamiliar ironies. Specifically, if an ironic utterance is familiar, then the ironic interpretation should be available without the need for extra inferential processes, whereas for unfamiliar ironies, the literal interpretation would be computed first, and a mismatch with context would lead to a re-interpretation of the statement as being ironic. We recorded participants' eye movements while they were reading (Experiment 1), and electrical brain activity while they were listening to (Experiment 2), familiar and unfamiliar ironies compared to non-ironic controls. Results show disruption to eye movements and an N400-like effect for unfamiliar ironies only, supporting the predictions of the graded salience hypothesis. In addition, in Experiment 2, a late positivity was found for both familiar and unfamiliar ironic materials, compared to non-ironic controls. We interpret this positivity as reflecting ongoing conflict between the literal and ironic interpretations of the utterance. |
Thomas Fischer; Sven-Thomas Graupner; Boris M Velichkovsky; Sebastian Pannasch Attentional dynamics during free picture viewing: Evidence from oculomotor behavior and electrocortical activity Journal Article Frontiers in Systems Neuroscience, 7 , pp. 1–9, 2013. @article{Fischer2013, title = {Attentional dynamics during free picture viewing: Evidence from oculomotor behavior and electrocortical activity}, author = {Thomas Fischer and Sven-Thomas Graupner and Boris M Velichkovsky and Sebastian Pannasch}, url = {http://journal.frontiersin.org/article/10.3389/fnsys.2013.00017/abstract}, doi = {10.3389/fnsys.2013.00017}, year = {2013}, date = {2013-01-01}, journal = {Frontiers in Systems Neuroscience}, volume = {7}, pages = {1--9}, abstract = {Most empirical evidence on attentional control is based on brief presentations of rather abstract stimuli. Results revealed indications for a dynamic interplay between bottom-up and top-down attentional mechanisms. Here we used a more naturalistic task to examine temporal signatures of attentional mechanisms on fine and coarse time scales. Subjects had to inspect digitized copies of 60 paintings, each shown for 40 s. We simultaneously measured oculomotor behavior and electrophysiological correlates of brain activity to compare early and late intervals (1) of inspection time of each picture (picture viewing) and (2) of the full experiment (time on task). For picture viewing, we found an increase in fixation duration and a decrease of saccadic amplitude while these parameters did not change with time on task. Furthermore, early in picture viewing we observed higher spatial and temporal similarity of gaze behavior. Analyzing electrical brain activity revealed changes in three components (C1, N1 and P2) of the eye fixation-related potential (EFRP); during picture viewing; no variation was obtained for the power in the frontal beta- and in the theta activity. Time on task analyses demonstrated no effects on the EFRP amplitudes but an increase of power in the frontal theta and beta band activity. Thus, behavioral and electrophysiological measures similarly show characteristic changes during picture viewing, indicating a shifting balance of its underlying (bottom-up and top-down) attentional mechanisms. Time on task also modulated top-down attention but probably represents a different attentional mechanism.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Most empirical evidence on attentional control is based on brief presentations of rather abstract stimuli. Results revealed indications for a dynamic interplay between bottom-up and top-down attentional mechanisms. Here we used a more naturalistic task to examine temporal signatures of attentional mechanisms on fine and coarse time scales. Subjects had to inspect digitized copies of 60 paintings, each shown for 40 s. We simultaneously measured oculomotor behavior and electrophysiological correlates of brain activity to compare early and late intervals (1) of inspection time of each picture (picture viewing) and (2) of the full experiment (time on task). For picture viewing, we found an increase in fixation duration and a decrease of saccadic amplitude while these parameters did not change with time on task. Furthermore, early in picture viewing we observed higher spatial and temporal similarity of gaze behavior. Analyzing electrical brain activity revealed changes in three components (C1, N1 and P2) of the eye fixation-related potential (EFRP); during picture viewing; no variation was obtained for the power in the frontal beta- and in the theta activity. Time on task analyses demonstrated no effects on the EFRP amplitudes but an increase of power in the frontal theta and beta band activity. Thus, behavioral and electrophysiological measures similarly show characteristic changes during picture viewing, indicating a shifting balance of its underlying (bottom-up and top-down) attentional mechanisms. Time on task also modulated top-down attention but probably represents a different attentional mechanism. |
Joshua J Foster; Emma M Bsales; Russell J Jaffe; Edward Awh Alpha-band activity reveals spontaneous representations of spatial position in visual working memory Journal Article Current Biology, 27 (20), pp. 3216–3223, 2017. @article{Foster2017, title = {Alpha-band activity reveals spontaneous representations of spatial position in visual working memory}, author = {Joshua J Foster and Emma M Bsales and Russell J Jaffe and Edward Awh}, doi = {10.1016/j.cub.2017.09.031}, year = {2017}, date = {2017-01-01}, journal = {Current Biology}, volume = {27}, number = {20}, pages = {3216--3223}, publisher = {Elsevier Ltd.}, abstract = {An emerging view suggests that spatial position is an integral component of working memory (WM), such that non-spatial features are bound to locations regardless of whether space is relevant [1, 2]. For instance, past work has shown that stimulus position is spontaneously remembered when non-spatial fea- tures are stored. Item recognition is enhanced when memoranda appear at the same location where they were encoded [3–5], and accessing non-spatial infor- mation elicits shifts of spatial attention to the original position of the stimulus [6, 7]. However, these find- ings do not establish that a persistent, active repre- sentation of stimulus position is maintained in WM because similar effects have also been documented following storage in long-termmemory [8, 9]. Here we show that the spatial position of the memorandum is actively coded by persistent neural activity during a non-spatial WM task. We used a spatial encoding model in conjunction with electroencephalogram (EEG) measurements of oscillatory alpha-band (8– 12 Hz) activity to track active representations of spatial position. The position of the stimulus varied trial to trial but was wholly irrelevant to the tasks. We nevertheless observed active neural representa- tions of the original stimulus position that persisted throughout the retention interval. Further experi- ments established that these spatial representations are dependent on the volitional storage of non- spatial features rather than being a lingering effect of sensory energy or initial encoding demands. These findings provide strong evidence that online spatial representations are spontaneously main- tained in WM—regardless of task relevance—during the storage of non-spatial features.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An emerging view suggests that spatial position is an integral component of working memory (WM), such that non-spatial features are bound to locations regardless of whether space is relevant [1, 2]. For instance, past work has shown that stimulus position is spontaneously remembered when non-spatial fea- tures are stored. Item recognition is enhanced when memoranda appear at the same location where they were encoded [3–5], and accessing non-spatial infor- mation elicits shifts of spatial attention to the original position of the stimulus [6, 7]. However, these find- ings do not establish that a persistent, active repre- sentation of stimulus position is maintained in WM because similar effects have also been documented following storage in long-termmemory [8, 9]. Here we show that the spatial position of the memorandum is actively coded by persistent neural activity during a non-spatial WM task. We used a spatial encoding model in conjunction with electroencephalogram (EEG) measurements of oscillatory alpha-band (8– 12 Hz) activity to track active representations of spatial position. The position of the stimulus varied trial to trial but was wholly irrelevant to the tasks. We nevertheless observed active neural representa- tions of the original stimulus position that persisted throughout the retention interval. Further experi- ments established that these spatial representations are dependent on the volitional storage of non- spatial features rather than being a lingering effect of sensory energy or initial encoding demands. These findings provide strong evidence that online spatial representations are spontaneously main- tained in WM—regardless of task relevance—during the storage of non-spatial features. |
Steven L Franconeri; Jason M Scimeca; Jessica C Roth; Sarah A Helseth; Lauren E Kahn Flexible visual processing of spatial relationships Journal Article Cognition, 122 (2), pp. 210–227, 2012. @article{Franconeri2012, title = {Flexible visual processing of spatial relationships}, author = {Steven L Franconeri and Jason M Scimeca and Jessica C Roth and Sarah A Helseth and Lauren E Kahn}, url = {http://dx.doi.org/10.1016/j.cognition.2011.11.002}, doi = {10.1016/j.cognition.2011.11.002}, year = {2012}, date = {2012-01-01}, journal = {Cognition}, volume = {122}, number = {2}, pages = {210--227}, publisher = {Elsevier B.V.}, abstract = {Visual processing breaks the world into parts and objects, allowing us not only to examine the pieces individually, but also to perceive the relationships among them. There is work exploring how we perceive spatial relationships within structures with existing representations, such as faces, common objects, or prototypical scenes. But strikingly, there is little work on the perceptual mechanisms that allow us to flexibly represent arbitrary spatial relationships, e.g., between objects in a novel room, or the elements within a map, graph or diagram. We describe two classes of mechanism that might allow such judgments. In the simultaneous class, both objects are selected concurrently. In contrast, we propose a sequential class, where objects are selected individually over time. We argue that this latter mechanism is more plausible even though it violates our intuitions. We demonstrate that shifts of selection do occur during spatial relationship judgments that feel simultaneous, by tracking selection with an electrophysiological correlate. We speculate that static structure across space may be encoded as a dynamic sequence across time. Flexible visual spatial relationship processing may serve as a case study of more general visual relation processing beyond space, to other dimensions such as size or numerosity.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Visual processing breaks the world into parts and objects, allowing us not only to examine the pieces individually, but also to perceive the relationships among them. There is work exploring how we perceive spatial relationships within structures with existing representations, such as faces, common objects, or prototypical scenes. But strikingly, there is little work on the perceptual mechanisms that allow us to flexibly represent arbitrary spatial relationships, e.g., between objects in a novel room, or the elements within a map, graph or diagram. We describe two classes of mechanism that might allow such judgments. In the simultaneous class, both objects are selected concurrently. In contrast, we propose a sequential class, where objects are selected individually over time. We argue that this latter mechanism is more plausible even though it violates our intuitions. We demonstrate that shifts of selection do occur during spatial relationship judgments that feel simultaneous, by tracking selection with an electrophysiological correlate. We speculate that static structure across space may be encoded as a dynamic sequence across time. Flexible visual spatial relationship processing may serve as a case study of more general visual relation processing beyond space, to other dimensions such as size or numerosity. |
H P Frey; S P Kelly; E C Lalor; J J Foxe Early spatial attentional modulation of inputs to the fovea Journal Article Journal of Neuroscience, 30 (13), pp. 4547–4551, 2010. @article{Frey2010, title = {Early spatial attentional modulation of inputs to the fovea}, author = {H P Frey and S P Kelly and E C Lalor and J J Foxe}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.5217-09.2010}, doi = {10.1523/JNEUROSCI.5217-09.2010}, year = {2010}, date = {2010-01-01}, journal = {Journal of Neuroscience}, volume = {30}, number = {13}, pages = {4547--4551}, abstract = {Attending to a specific spatial location modulates responsivity of neurons with receptive fields processing that part of the environment. A major outstanding question is whether attentional modulation operates differently for the foveal (central) representation of the visual field than it does for the periphery. Indeed, recent animal electrophysiological recordings suggest that attention differentially affects spatial integration for central and peripheral receptive fields in primary visual cortex. In human electroencephalographic recordings, spatial attention to peripheral locations robustly modulates activity in early visual regions, but it has been claimed that this mechanism does not operate in foveal vision. Here, however, we show clear early attentional modulation of foveal stimulation with the same timing and cortical sources as seen for peripheral stimuli, demonstrating that attentional gain control operates similarly across the entire field of view. These results imply that covertly attending away from the center of gaze, which is a common paradigm in behavioral and electrophysiological studies of attention, results in a precisely timed push–pull mechanism. While the amplitude of the initial response to stimulation at attended peripheral locations is significantly increased beginning at 80 ms, the amplitude of the response to foveal stimulation begins to be attenuated.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Attending to a specific spatial location modulates responsivity of neurons with receptive fields processing that part of the environment. A major outstanding question is whether attentional modulation operates differently for the foveal (central) representation of the visual field than it does for the periphery. Indeed, recent animal electrophysiological recordings suggest that attention differentially affects spatial integration for central and peripheral receptive fields in primary visual cortex. In human electroencephalographic recordings, spatial attention to peripheral locations robustly modulates activity in early visual regions, but it has been claimed that this mechanism does not operate in foveal vision. Here, however, we show clear early attentional modulation of foveal stimulation with the same timing and cortical sources as seen for peripheral stimuli, demonstrating that attentional gain control operates similarly across the entire field of view. These results imply that covertly attending away from the center of gaze, which is a common paradigm in behavioral and electrophysiological studies of attention, results in a precisely timed push–pull mechanism. While the amplitude of the initial response to stimulation at attended peripheral locations is significantly increased beginning at 80 ms, the amplitude of the response to foveal stimulation begins to be attenuated. |
Aline Frey; Gelu Ionescu; Benoît Lemaire; Francisco López-Orozco; Thierry Baccino; Anne Guérin-Dugué Decision-making in information seeking on texts: an eye-fixation-related potentials investigation Journal Article Frontiers in Systems Neuroscience, 7 , pp. 1–22, 2013. @article{Frey2013, title = {Decision-making in information seeking on texts: an eye-fixation-related potentials investigation}, author = {Aline Frey and Gelu Ionescu and Beno{î}t Lemaire and Francisco López-Orozco and Thierry Baccino and Anne Guérin-Dugué}, url = {http://journal.frontiersin.org/article/10.3389/fnsys.2013.00039/abstract}, doi = {10.3389/fnsys.2013.00039}, year = {2013}, date = {2013-01-01}, journal = {Frontiers in Systems Neuroscience}, volume = {7}, pages = {1--22}, abstract = {Reading on a web page is known to be not linear and people need to make fast decisions about whether they have to stop or not reading. In such context, reading, and decision-making processes are intertwined and this experiment attempts to separate them through electrophysiological patterns provided by the Eye-Fixation-Related Potentials technique (EFRPs). We conducted an experiment in which EFRPs were recorded while participants read blocks of text that were semantically highly related, moderately related, and unrelated to a given goal. Participants had to decide as fast as possible whether the text was related or not to the semantic goal given at a prior stage. Decision making (stopping information search) may occur when the paragraph is highly related to the goal (positive decision) or when it is unrelated to the goal (negative decision). EFRPs were analyzed on and around typical eye fixations: either on words belonging to the goal (target), subjected to a high rate of positive decisions, or on low frequency unrelated words (incongruent), subjected to a high rate of negative decisions. In both cases, we found EFRPs specific patterns (amplitude peaking between 51 to 120 ms after fixation onset) spreading out on the next words following the goal word and the second fixation after an incongruent word, in parietal and occipital areas. We interpreted these results as delayed late components (P3b and N400), reflecting the decision to stop information searching. Indeed, we show a clear spill-over effect showing that the effect on word N spread out on word N + 1 and N + 2.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Reading on a web page is known to be not linear and people need to make fast decisions about whether they have to stop or not reading. In such context, reading, and decision-making processes are intertwined and this experiment attempts to separate them through electrophysiological patterns provided by the Eye-Fixation-Related Potentials technique (EFRPs). We conducted an experiment in which EFRPs were recorded while participants read blocks of text that were semantically highly related, moderately related, and unrelated to a given goal. Participants had to decide as fast as possible whether the text was related or not to the semantic goal given at a prior stage. Decision making (stopping information search) may occur when the paragraph is highly related to the goal (positive decision) or when it is unrelated to the goal (negative decision). EFRPs were analyzed on and around typical eye fixations: either on words belonging to the goal (target), subjected to a high rate of positive decisions, or on low frequency unrelated words (incongruent), subjected to a high rate of negative decisions. In both cases, we found EFRPs specific patterns (amplitude peaking between 51 to 120 ms after fixation onset) spreading out on the next words following the goal word and the second fixation after an incongruent word, in parietal and occipital areas. We interpreted these results as delayed late components (P3b and N400), reflecting the decision to stop information searching. Indeed, we show a clear spill-over effect showing that the effect on word N spread out on word N + 1 and N + 2. |
Hans Peter Frey; Sophie Molholm; Edmund C Lalor; Natalie N Russo; John J Foxe Atypical cortical representation of peripheral visual space in children with an autism spectrum disorder Journal Article European Journal of Neuroscience, 38 (1), pp. 2125–2138, 2013. @article{Frey2013a, title = {Atypical cortical representation of peripheral visual space in children with an autism spectrum disorder}, author = {Hans Peter Frey and Sophie Molholm and Edmund C Lalor and Natalie N Russo and John J Foxe}, url = {http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=emed11&NEWS=N&AN=2013425482}, doi = {10.1111/ejn.12243}, year = {2013}, date = {2013-01-01}, journal = {European Journal of Neuroscience}, volume = {38}, number = {1}, pages = {2125--2138}, abstract = {A key feature of early visual cortical regions is that they contain discretely organized retinotopic maps. Titration of these maps must occur through experience, and the fidelity of their spatial tuning will depend on the consistency and accuracy of the eye movement system. Anomalies in fixation patterns and the ballistics of eye movements are well documented in autism spectrum disorder (ASD), with off-center fixations a hallmark of the phenotype. We hypothesized that these atypicalities might affect the development of visuo-spatial maps and specifically that peripheral inputs might receive altered processing in ASD. Using high-density recordings of visual evoked potentials (VEPs) and a novel system-identification approach known as VESPA (visual evoked spread spectrum analysis), we assessed sensory responses to centrally and peripherally presented stimuli. Additionally, input luminance was varied to bias responsiveness to the magnocellular system, given previous suggestions of magnocellular-specific deficits in ASD. Participants were 22 ASD children (7-17 years of age) and 31 age- and performance-IQ-matched neurotypical controls. Both VEP and VESPA responses to central presentations were indistinguishable between groups. In contrast, peripheral presentations resulted in significantly greater early VEP and VESPA amplitudes in the ASD cohort. We found no evidence that anomalous enhancement was restricted to magnocellular-biased responses. The extent of peripheral response enhancement was related to the severity of stereotyped behaviors and restricted interests, cardinal symptoms of ASD. The current results point to differential visuo-spatial cortical mapping in ASD, shedding light on the consequences of peculiarities in gaze and stereotyped visual behaviors often reported by clinicians working with this population.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A key feature of early visual cortical regions is that they contain discretely organized retinotopic maps. Titration of these maps must occur through experience, and the fidelity of their spatial tuning will depend on the consistency and accuracy of the eye movement system. Anomalies in fixation patterns and the ballistics of eye movements are well documented in autism spectrum disorder (ASD), with off-center fixations a hallmark of the phenotype. We hypothesized that these atypicalities might affect the development of visuo-spatial maps and specifically that peripheral inputs might receive altered processing in ASD. Using high-density recordings of visual evoked potentials (VEPs) and a novel system-identification approach known as VESPA (visual evoked spread spectrum analysis), we assessed sensory responses to centrally and peripherally presented stimuli. Additionally, input luminance was varied to bias responsiveness to the magnocellular system, given previous suggestions of magnocellular-specific deficits in ASD. Participants were 22 ASD children (7-17 years of age) and 31 age- and performance-IQ-matched neurotypical controls. Both VEP and VESPA responses to central presentations were indistinguishable between groups. In contrast, peripheral presentations resulted in significantly greater early VEP and VESPA amplitudes in the ASD cohort. We found no evidence that anomalous enhancement was restricted to magnocellular-biased responses. The extent of peripheral response enhancement was related to the severity of stereotyped behaviors and restricted interests, cardinal symptoms of ASD. The current results point to differential visuo-spatial cortical mapping in ASD, shedding light on the consequences of peculiarities in gaze and stereotyped visual behaviors often reported by clinicians working with this population. |
Hans Peter Frey; Anita M Schmid; Jeremy W Murphy; Sophie Molholm; Edmund C Lalor; John J Foxe Modulation of early cortical processing during divided attention to non-contiguous locations Journal Article European Journal of Neuroscience, 39 (9), pp. 1499–1507, 2014. @article{Frey2014, title = {Modulation of early cortical processing during divided attention to non-contiguous locations}, author = {Hans Peter Frey and Anita M Schmid and Jeremy W Murphy and Sophie Molholm and Edmund C Lalor and John J Foxe}, doi = {10.1111/ejn.12523}, year = {2014}, date = {2014-01-01}, journal = {European Journal of Neuroscience}, volume = {39}, number = {9}, pages = {1499--1507}, abstract = {We often face the challenge of simultaneously attending to multiple non-contiguous regions of space. There is ongoing debate as to how spatial attention is divided under these situations. Whereas, for several years, the predominant view was that humans could divide the attentional spotlight, several recent studies argue in favor of a unitary spotlight that rhythmically samples relevant locations. Here, this issue was addressed by the use of high-density electrophysiology in concert with the multifocal m-sequence technique to examine visual evoked responses to multiple simultaneous streams of stimulation. Concurrently, we assayed the topographic distribution of alpha-band oscillatory mechanisms, a measure of attentional suppression. Participants performed a difficult detection task that required simultaneous attention to two stimuli in contiguous (undivided) or non-contiguous parts of space. In the undivided condition, the classic pattern of attentional modulation was observed, with increased amplitude of the early visual evoked response and increased alpha amplitude ipsilateral to the attended hemifield. For the divided condition, early visual responses to attended stimuli were also enhanced, and the observed multifocal topographic distribution of alpha suppression was in line with the divided attention hypothesis. These results support the existence of divided attentional spotlights, providing evidence that the corresponding modulation occurs during initial sensory processing time-frames in hierarchically early visual regions, and that suppressive mechanisms of visual attention selectively target distracter locations during divided spatial attention.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We often face the challenge of simultaneously attending to multiple non-contiguous regions of space. There is ongoing debate as to how spatial attention is divided under these situations. Whereas, for several years, the predominant view was that humans could divide the attentional spotlight, several recent studies argue in favor of a unitary spotlight that rhythmically samples relevant locations. Here, this issue was addressed by the use of high-density electrophysiology in concert with the multifocal m-sequence technique to examine visual evoked responses to multiple simultaneous streams of stimulation. Concurrently, we assayed the topographic distribution of alpha-band oscillatory mechanisms, a measure of attentional suppression. Participants performed a difficult detection task that required simultaneous attention to two stimuli in contiguous (undivided) or non-contiguous parts of space. In the undivided condition, the classic pattern of attentional modulation was observed, with increased amplitude of the early visual evoked response and increased alpha amplitude ipsilateral to the attended hemifield. For the divided condition, early visual responses to attended stimuli were also enhanced, and the observed multifocal topographic distribution of alpha suppression was in line with the divided attention hypothesis. These results support the existence of divided attentional spotlights, providing evidence that the corresponding modulation occurs during initial sensory processing time-frames in hierarchically early visual regions, and that suppressive mechanisms of visual attention selectively target distracter locations during divided spatial attention. |
Galit Fuhrmann Alpert; Ran Manor; Assaf B Spanier; Leon Y Deouell; Amir B Geva Spatiotemporal representations of rapid visual target detection: A single-trial EEG classification algorithm Journal Article IEEE Transactions on Biomedical Engineering, 61 (8), pp. 2290–2303, 2014. @article{FuhrmannAlpert2014a, title = {Spatiotemporal representations of rapid visual target detection: A single-trial EEG classification algorithm}, author = {Galit {Fuhrmann Alpert} and Ran Manor and Assaf B Spanier and Leon Y Deouell and Amir B Geva}, doi = {10.1109/TBME.2013.2289898}, year = {2014}, date = {2014-01-01}, journal = {IEEE Transactions on Biomedical Engineering}, volume = {61}, number = {8}, pages = {2290--2303}, abstract = {Brain computer interface applications, developed for both healthy and clinical populations, critically depend on decoding brain activity in single trials. The goal of the present study was to detect distinctive spatiotemporal brain patterns within a set of event related responses. We introduce a novel classification algorithm, the spatially weighted FLD-PCA (SWFP), which is based on a two-step linear classification of event-related responses, using fisher linear discriminant (FLD) classifier and principal component analysis (PCA) for dimensionality reduction. As a benchmark algorithm, we consider the hierarchical discriminant component Analysis (HDCA), introduced by Parra, et al. 2007. We also consider a modified version of the HDCA, namely the hierarchical discriminant principal component analysis algorithm (HDPCA). We compare single-trial classification accuracies of all the three algorithms, each applied to detect target images within a rapid serial visual presentation (RSVP, 10 Hz) of images from five different object categories, based on single-trial brain responses. We find a systematic superiority of our classification algorithm in the tested paradigm. Additionally, HDPCA significantly increases classification accuracies compared to the HDCA. Finally, we show that presenting several repetitions of the same image exemplars improve accuracy, and thus may be important in cases where high accuracy is crucial.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Brain computer interface applications, developed for both healthy and clinical populations, critically depend on decoding brain activity in single trials. The goal of the present study was to detect distinctive spatiotemporal brain patterns within a set of event related responses. We introduce a novel classification algorithm, the spatially weighted FLD-PCA (SWFP), which is based on a two-step linear classification of event-related responses, using fisher linear discriminant (FLD) classifier and principal component analysis (PCA) for dimensionality reduction. As a benchmark algorithm, we consider the hierarchical discriminant component Analysis (HDCA), introduced by Parra, et al. 2007. We also consider a modified version of the HDCA, namely the hierarchical discriminant principal component analysis algorithm (HDPCA). We compare single-trial classification accuracies of all the three algorithms, each applied to detect target images within a rapid serial visual presentation (RSVP, 10 Hz) of images from five different object categories, based on single-trial brain responses. We find a systematic superiority of our classification algorithm in the tested paradigm. Additionally, HDPCA significantly increases classification accuracies compared to the HDCA. Finally, we show that presenting several repetitions of the same image exemplars improve accuracy, and thus may be important in cases where high accuracy is crucial. |
Galit Fuhrmann Alpert; Ran Manor; Assaf B Spanier; Leon Y Deouell; Amir B Geva Spatio-temporal representations of rapid visual target detection: A single trial EEG classification Journal Article IEEE Transactions on Biomedical Engineering, 61 (8), pp. 2290–2303, 2014. @article{FuhrmannAlpert2014b, title = {Spatio-temporal representations of rapid visual target detection: A single trial EEG classification}, author = {Galit {Fuhrmann Alpert} and Ran Manor and Assaf B Spanier and Leon Y Deouell and Amir B Geva}, year = {2014}, date = {2014-01-01}, journal = {IEEE Transactions on Biomedical Engineering}, volume = {61}, number = {8}, pages = {2290--2303}, abstract = {Brain computer interface applications, developed for both healthy and clinical populations, critically depend on decod- ing brain activity in single trials. The goal of the present study was to detect distinctive spatiotemporal brain patterns within a set of event related responses. We introduce a novel classification algo- rithm, the spatially weighted FLD-PCA (SWFP), which is based on a two-step linear classification of event-related responses, using fisher linear discriminant (FLD) classifier and principal compo- nent analysis (PCA) for dimensionality reduction. As a benchmark algorithm, we consider the hierarchical discriminant component Analysis (HDCA), introduced by Parra, et al. 2007. We also con- sider a modified version of the HDCA, namely the hierarchical discriminant principal component analysis algorithm (HDPCA). We compare single-trial classification accuracies of all the three algorithms, each applied to detect target images within a rapid serial visual presentation (RSVP, 10 Hz) of images from five dif- ferent object categories, based on single-trial brain responses. We find a systematic superiority of our classification algorithm in the tested paradigm.Additionally, HDPCA significantly increases clas- sification accuracies compared to the HDCA. Finally, we show that presenting several repetitions of the same image exemplars im- prove accuracy, and thus may be important in cases where high accuracy is crucial.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Brain computer interface applications, developed for both healthy and clinical populations, critically depend on decod- ing brain activity in single trials. The goal of the present study was to detect distinctive spatiotemporal brain patterns within a set of event related responses. We introduce a novel classification algo- rithm, the spatially weighted FLD-PCA (SWFP), which is based on a two-step linear classification of event-related responses, using fisher linear discriminant (FLD) classifier and principal compo- nent analysis (PCA) for dimensionality reduction. As a benchmark algorithm, we consider the hierarchical discriminant component Analysis (HDCA), introduced by Parra, et al. 2007. We also con- sider a modified version of the HDCA, namely the hierarchical discriminant principal component analysis algorithm (HDPCA). We compare single-trial classification accuracies of all the three algorithms, each applied to detect target images within a rapid serial visual presentation (RSVP, 10 Hz) of images from five dif- ferent object categories, based on single-trial brain responses. We find a systematic superiority of our classification algorithm in the tested paradigm.Additionally, HDPCA significantly increases clas- sification accuracies compared to the HDCA. Finally, we show that presenting several repetitions of the same image exemplars im- prove accuracy, and thus may be important in cases where high accuracy is crucial. |
D Gagnon Transcranial magnetic stimulation of frontal oculomotor regions during smooth pursuit Journal Article Journal of Neuroscience, 26 (2), pp. 458–466, 2006. @article{Gagnon2006, title = {Transcranial magnetic stimulation of frontal oculomotor regions during smooth pursuit}, author = {D Gagnon}, doi = {10.1523/JNEUROSCI.2789-05.2006}, year = {2006}, date = {2006-01-01}, journal = {Journal of Neuroscience}, volume = {26}, number = {2}, pages = {458--466}, abstract = {Both the frontal eye fields (FEFs) and supplementary eye fields (SEFs) are known to be involved in smooth pursuit eye movements. It has been shown recently that stimulation of the smooth-pursuit area of the FEF [frontal pursuit area (FPA)] in monkey increases the pursuit response to unexpected changes in target motion during pursuit. In the current study, we applied transcranial magnetic stimulation (TMS) to the FPA and SEF in humans during sinusoidal pursuit to assess its effects on the pursuit response to predictable, rather than unexpected, changes in target motion. For the FPA, we found that TMS applied immediately before the target reversed direction increased eye velocity in the new direction, whereas TMS applied in mid-cycle, immediately before the target began to slow, decreased eye velocity. For the SEF, TMS applied at target reversal increased eye velocity in the new direction but had no effect on eye velocity when applied at mid-cycle. TMS of the control region (leg region of the somatosensory cortex) did not affect eye velocity at either point. Previous stimulation studies of FPA during pursuit have suggested that this region is involved in controlling the gain of the transformation of visual signals into pursuit motor commands. The current results suggest that the gain of the transformation of predictive signals into motor commands is also controlled by the FPA. The effect of stimulation of the SEF is distinct from that of the FPA and suggests that its role in sinusoidal pursuit is primarily at the target direction reversal.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Both the frontal eye fields (FEFs) and supplementary eye fields (SEFs) are known to be involved in smooth pursuit eye movements. It has been shown recently that stimulation of the smooth-pursuit area of the FEF [frontal pursuit area (FPA)] in monkey increases the pursuit response to unexpected changes in target motion during pursuit. In the current study, we applied transcranial magnetic stimulation (TMS) to the FPA and SEF in humans during sinusoidal pursuit to assess its effects on the pursuit response to predictable, rather than unexpected, changes in target motion. For the FPA, we found that TMS applied immediately before the target reversed direction increased eye velocity in the new direction, whereas TMS applied in mid-cycle, immediately before the target began to slow, decreased eye velocity. For the SEF, TMS applied at target reversal increased eye velocity in the new direction but had no effect on eye velocity when applied at mid-cycle. TMS of the control region (leg region of the somatosensory cortex) did not affect eye velocity at either point. Previous stimulation studies of FPA during pursuit have suggested that this region is involved in controlling the gain of the transformation of visual signals into pursuit motor commands. The current results suggest that the gain of the transformation of predictive signals into motor commands is also controlled by the FPA. The effect of stimulation of the SEF is distinct from that of the FPA and suggests that its role in sinusoidal pursuit is primarily at the target direction reversal. |
Steffen Gais; Sabine Köster; Andreas Sprenger; Judith Bethke; Wolfgang Heide; Hubert Kimmig Sleep is required for improving reaction times after training on a procedural visuo-motor task Journal Article Neurobiology of Learning and Memory, 90 (4), pp. 610–615, 2008. @article{Gais2008, title = {Sleep is required for improving reaction times after training on a procedural visuo-motor task}, author = {Steffen Gais and Sabine Köster and Andreas Sprenger and Judith Bethke and Wolfgang Heide and Hubert Kimmig}, url = {http://dx.doi.org/10.1016/j.nlm.2008.07.016}, doi = {10.1016/j.nlm.2008.07.016}, year = {2008}, date = {2008-01-01}, journal = {Neurobiology of Learning and Memory}, volume = {90}, number = {4}, pages = {610--615}, abstract = {Sleep has been found to enhance consolidation of many different forms of memory. However in most procedural tasks, a sleep-independent, fast learning component interacts with slow, sleep-dependent improvements. Here, we show that in humans a visuo-motor saccade learning task shows no improvements during training, but only during a delayed recall testing after a period of sleep. Subjects were trained in a prosaccade task (saccade to a visual target). Performance was tested in the prosaccade and the antisaccade task (saccade to opposite direction of the target) before training, after a night of sleep or sleep deprivation, after a night of recovery sleep, and finally in a follow-up test 4 weeks later. We found no immediate improvement in saccadic reaction time (SRT) during training, but a delayed reduction in SRT, indicating a slow-learning process. This reduction occurred only after a period of sleep, i.e. after the first night in the sleep group and after recovery sleep in the sleep deprivation group. This improvement was stable during the 4-week follow-up. Saccadic training can thus induce covert changes in the saccade generation pathway. During the following sleep period, these changes in turn bring about overt performance improvements, presuming a learning effect based on synaptic tagging.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Sleep has been found to enhance consolidation of many different forms of memory. However in most procedural tasks, a sleep-independent, fast learning component interacts with slow, sleep-dependent improvements. Here, we show that in humans a visuo-motor saccade learning task shows no improvements during training, but only during a delayed recall testing after a period of sleep. Subjects were trained in a prosaccade task (saccade to a visual target). Performance was tested in the prosaccade and the antisaccade task (saccade to opposite direction of the target) before training, after a night of sleep or sleep deprivation, after a night of recovery sleep, and finally in a follow-up test 4 weeks later. We found no immediate improvement in saccadic reaction time (SRT) during training, but a delayed reduction in SRT, indicating a slow-learning process. This reduction occurred only after a period of sleep, i.e. after the first night in the sleep group and after recovery sleep in the sleep deprivation group. This improvement was stable during the 4-week follow-up. Saccadic training can thus induce covert changes in the saccade generation pathway. During the following sleep period, these changes in turn bring about overt performance improvements, presuming a learning effect based on synaptic tagging. |
Matthew A Gannon; Stephanie M Long; Nathan A Parks Homeostatic plasticity in human extrastriate cortex following a simulated peripheral scotoma Journal Article Experimental Brain Research, 235 (11), pp. 3391–3401, 2017. @article{Gannon2017, title = {Homeostatic plasticity in human extrastriate cortex following a simulated peripheral scotoma}, author = {Matthew A Gannon and Stephanie M Long and Nathan A Parks}, doi = {10.1007/s00221-017-5042-0}, year = {2017}, date = {2017-01-01}, journal = {Experimental Brain Research}, volume = {235}, number = {11}, pages = {3391--3401}, publisher = {Springer Berlin Heidelberg}, abstract = {Neuroimaging and patient work over the past decade have indicated that, following retinal deafferenta- tion, the human visual cortex undergoes a large-scale and enduring reorganization of its topography such that the clas- sical retinotopic organization of deafferented visual cortex remaps to represent non-classical regions of visual space. Such long-term visual reorganization is proposed to occur through changes in the functional balance of deafferented visual circuits that engage more lasting changes through activity-dependent neuroplasticity. Here, we investigated the short-term changes in functional balance (short-term plastic- ity; homeostatic plasticity) that occur within deafferented human visual cortices. We recorded electroencephalogram (EEG) while observers were conditioned for 6 s with a simu- lated retinal scotoma (artificial scotoma) positioned 8.0° in the periphery. Visual evoked potentials (VEPs) evoked by the onset of sinusoidal visual probes that varied in their tilt were used to examine changes in cortical excitability within and around cortical representations of the simulated sco- toma. Psychophysical orientation functions obtained from discrimination of visual probe tilt were used to examine alterations in the stimulus selectivity within the scotoma representations. Consistent with a mechanism of homeo- static disinhibition, an early extrastriate component of the VEP (the early phase P1) exhibited increased amplitude fol- lowing the condition with a simulated scotoma relative to a stimulus-matched control condition. This increased visual cortical response was associated with a reduction in the slope of the psychophysical orientation function, suggesting a broader tuning of neural populations within scotoma repre- sentations. Together, these findings support a mechanism of disinhibition in promoting visual plasticity and topographi- cal reorganization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Neuroimaging and patient work over the past decade have indicated that, following retinal deafferenta- tion, the human visual cortex undergoes a large-scale and enduring reorganization of its topography such that the clas- sical retinotopic organization of deafferented visual cortex remaps to represent non-classical regions of visual space. Such long-term visual reorganization is proposed to occur through changes in the functional balance of deafferented visual circuits that engage more lasting changes through activity-dependent neuroplasticity. Here, we investigated the short-term changes in functional balance (short-term plastic- ity; homeostatic plasticity) that occur within deafferented human visual cortices. We recorded electroencephalogram (EEG) while observers were conditioned for 6 s with a simu- lated retinal scotoma (artificial scotoma) positioned 8.0° in the periphery. Visual evoked potentials (VEPs) evoked by the onset of sinusoidal visual probes that varied in their tilt were used to examine changes in cortical excitability within and around cortical representations of the simulated sco- toma. Psychophysical orientation functions obtained from discrimination of visual probe tilt were used to examine alterations in the stimulus selectivity within the scotoma representations. Consistent with a mechanism of homeo- static disinhibition, an early extrastriate component of the VEP (the early phase P1) exhibited increased amplitude fol- lowing the condition with a simulated scotoma relative to a stimulus-matched control condition. This increased visual cortical response was associated with a reduction in the slope of the psychophysical orientation function, suggesting a broader tuning of neural populations within scotoma repre- sentations. Together, these findings support a mechanism of disinhibition in promoting visual plasticity and topographi- cal reorganization. |
Nigel Gebodh; Isabel M Vanegas; Simon P Kelly Effects of stimulus size and contrast on the initial primary visual cortical response in humans Journal Article Brain Topography, 30 (4), pp. 450–460, 2017. @article{Gebodh2017, title = {Effects of stimulus size and contrast on the initial primary visual cortical response in humans}, author = {Nigel Gebodh and Isabel M Vanegas and Simon P Kelly}, doi = {10.1007/s10548-016-0530-2}, year = {2017}, date = {2017-01-01}, journal = {Brain Topography}, volume = {30}, number = {4}, pages = {450--460}, publisher = {Springer US}, abstract = {Decades of intracranial electrophysiological investigation into the primary visual cortex (V1) have produced many fundamental insights into the computations carried out in low-level visual circuits of the brain. Some of the most important work has been simply concerned with the precise measurement of neural response variations as a function of elementary stimulus attributes such as contrast and size. Surprisingly, such simple but fundamental characterization of V1 responses has not been carried out in human electrophysiology. Here we report such a detailed characterization for the initial “C1” component of the scalp-recorded visual evoked potential (VEP). The C1 is known to be dominantly generated by initial afferent activation in V1, but is difficult to record reliably due to interindividual anatomical variability. We used pattern-pulse multifocal VEP mapping to identify a stimulus position that activates the left lower calcarine bank in each individual, and afterwards measured robust negative C1s over posterior midline scalp to gratings presented sequentially at that location. We found clear and systematic increases in C1 peak amplitude and decreases in peak latency with increasing size as well as with increasing contrast. With a sample of 15 subjects and ~180 trials per condition, reliable C1 amplitudes of −0.46 µV were evoked at as low a contrast as 3.13% and as large as −4.82 µV at 100% contrast, using stimuli of 3.33° diameter. A practical implication is that by placing sufficiently-sized stimuli to target favorable calcarine cortical loci, robust V1 responses can be measured at contrasts close to perceptual thresholds, which could greatly facilitate principled studies of early visual perception and attention.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Decades of intracranial electrophysiological investigation into the primary visual cortex (V1) have produced many fundamental insights into the computations carried out in low-level visual circuits of the brain. Some of the most important work has been simply concerned with the precise measurement of neural response variations as a function of elementary stimulus attributes such as contrast and size. Surprisingly, such simple but fundamental characterization of V1 responses has not been carried out in human electrophysiology. Here we report such a detailed characterization for the initial “C1” component of the scalp-recorded visual evoked potential (VEP). The C1 is known to be dominantly generated by initial afferent activation in V1, but is difficult to record reliably due to interindividual anatomical variability. We used pattern-pulse multifocal VEP mapping to identify a stimulus position that activates the left lower calcarine bank in each individual, and afterwards measured robust negative C1s over posterior midline scalp to gratings presented sequentially at that location. We found clear and systematic increases in C1 peak amplitude and decreases in peak latency with increasing size as well as with increasing contrast. With a sample of 15 subjects and ~180 trials per condition, reliable C1 amplitudes of −0.46 µV were evoked at as low a contrast as 3.13% and as large as −4.82 µV at 100% contrast, using stimuli of 3.33° diameter. A practical implication is that by placing sufficiently-sized stimuli to target favorable calcarine cortical loci, robust V1 responses can be measured at contrasts close to perceptual thresholds, which could greatly facilitate principled studies of early visual perception and attention. |
Hagar Gelbard-Sagiv; Efrat Magidov; Haggai Sharon; Talma Hendler Noradrenaline modulates visual perception and late visually evoked activity Journal Article Current Biology, 28 , pp. 2239–2249, 2018. @article{Gelbard-Sagiv2018, title = {Noradrenaline modulates visual perception and late visually evoked activity}, author = {Hagar Gelbard-Sagiv and Efrat Magidov and Haggai Sharon and Talma Hendler}, doi = {10.1016/j.cub.2018.05.051}, year = {2018}, date = {2018-01-01}, journal = {Current Biology}, volume = {28}, pages = {2239--2249}, abstract = {An identical sensory stimulus may or may not be incorporated into perceptual experience, depending on the behavioral and cognitive state of the organism. What determines whether a sensory stimulus will be perceived? While different behavioral and cognitive states may share a similar profile of electrophysiology, metabolism, and early sensory responses, neuromodulation is often different and therefore may constitute a key mechanism enabling perceptual awareness. Specifically, noradrenaline improves sensory responses, correlates with orienting toward behaviorally relevant stimuli, and is markedly reduced during sleep, while experience is largely ‘‘disconnected'' from external events. Despite correlative evidence hinting at a relationship between noradrenaline and perception, causal evidence remains absent. Here, we pharmacologically down- and upregulated noradrenaline signaling in healthy volunteers using clonidine and reboxetine in double-blind placebo-controlled experiments, testing the effects on perceptual abilities and visually evoked electroencephalography (EEG) and fMRI responses. We found that detection sensitivity, discrimination accuracy, and subjective visibility change in accordance with noradrenaline (NE) levels, whereas decision bias (criterion) is not affected. Similarly, noradrenaline increases the consistency of EEG visually evoked potentials, while lower noradrenaline levels delay response components around 200 ms. Furthermore, bloodoxygen-level-dependent (BOLD) fMRI activations in high-order visual cortex selectively vary along with noradrenaline signaling. Taken together, these results point to noradrenaline as a key factor causally linking visual awareness to external world events.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An identical sensory stimulus may or may not be incorporated into perceptual experience, depending on the behavioral and cognitive state of the organism. What determines whether a sensory stimulus will be perceived? While different behavioral and cognitive states may share a similar profile of electrophysiology, metabolism, and early sensory responses, neuromodulation is often different and therefore may constitute a key mechanism enabling perceptual awareness. Specifically, noradrenaline improves sensory responses, correlates with orienting toward behaviorally relevant stimuli, and is markedly reduced during sleep, while experience is largely ‘‘disconnected'' from external events. Despite correlative evidence hinting at a relationship between noradrenaline and perception, causal evidence remains absent. Here, we pharmacologically down- and upregulated noradrenaline signaling in healthy volunteers using clonidine and reboxetine in double-blind placebo-controlled experiments, testing the effects on perceptual abilities and visually evoked electroencephalography (EEG) and fMRI responses. We found that detection sensitivity, discrimination accuracy, and subjective visibility change in accordance with noradrenaline (NE) levels, whereas decision bias (criterion) is not affected. Similarly, noradrenaline increases the consistency of EEG visually evoked potentials, while lower noradrenaline levels delay response components around 200 ms. Furthermore, bloodoxygen-level-dependent (BOLD) fMRI activations in high-order visual cortex selectively vary along with noradrenaline signaling. Taken together, these results point to noradrenaline as a key factor causally linking visual awareness to external world events. |
Edden M Gerber; Tal Golan; Robert T Knight; Leon Y Deouell Cortical representation of persistent visual stimuli Journal Article NeuroImage, 161 , pp. 67–79, 2017. @article{Gerber2017, title = {Cortical representation of persistent visual stimuli}, author = {Edden M Gerber and Tal Golan and Robert T Knight and Leon Y Deouell}, doi = {10.1016/j.neuroimage.2017.08.028}, year = {2017}, date = {2017-01-01}, journal = {NeuroImage}, volume = {161}, pages = {67--79}, publisher = {Elsevier Ltd}, abstract = {Research into visual neural activity has focused almost exclusively on onset- or change-driven responses and little is known about how information is encoded in the brain during sustained periods of visual perception. We used intracranial recordings in humans to determine the degree to which the presence of a visual stimulus is persistently encoded by neural activity. The correspondence between stimulus duration and neural response duration was strongest in early visual cortex and gradually diminished along the visual hierarchy, such that is was weakest in inferior-temporal category-selective regions. A similar posterior-anterior gradient was found within inferior temporal face-selective regions, with posterior but not anterior sites showing persistent face-selective activity. The results suggest that regions that appear uniform in terms of their category selectivity are dissociated by how they temporally represent a stimulus in support of ongoing visual perception, and delineate a large-scale organizing principle of the ventral visual stream.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Research into visual neural activity has focused almost exclusively on onset- or change-driven responses and little is known about how information is encoded in the brain during sustained periods of visual perception. We used intracranial recordings in humans to determine the degree to which the presence of a visual stimulus is persistently encoded by neural activity. The correspondence between stimulus duration and neural response duration was strongest in early visual cortex and gradually diminished along the visual hierarchy, such that is was weakest in inferior-temporal category-selective regions. A similar posterior-anterior gradient was found within inferior temporal face-selective regions, with posterior but not anterior sites showing persistent face-selective activity. The results suggest that regions that appear uniform in terms of their category selectivity are dissociated by how they temporally represent a stimulus in support of ongoing visual perception, and delineate a large-scale organizing principle of the ventral visual stream. |
Mónika Gergelyfi; Benvenuto Jacob; Etienne Olivier; Alexandre Zénon Dissociation between mental fatigue and motivational state during prolonged mental activity Journal Article Frontiers in Behavioral Neuroscience, 9 , pp. 1–15, 2015. @article{Gergelyfi2015, title = {Dissociation between mental fatigue and motivational state during prolonged mental activity}, author = {Mónika Gergelyfi and Benvenuto Jacob and Etienne Olivier and Alexandre Zénon}, url = {http://journal.frontiersin.org/Article/10.3389/fnbeh.2015.00176/abstract}, doi = {10.3389/fnbeh.2015.00176}, year = {2015}, date = {2015-01-01}, journal = {Frontiers in Behavioral Neuroscience}, volume = {9}, pages = {1--15}, abstract = {Mental fatigue (MF) is commonly observed following prolonged cognitive activity and can have major repercussions on the daily life of patients as well as healthy individuals. Despite its important impact, the cognitive processes involved in MF remain largely unknown. An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement. Here, to test this hypothesis, we measured various neural, autonomic, psychometric and behavioral signatures of MF and motivation (EEG, ECG, pupil size, eye blinks, Skin conductance responses (SCRs), questionnaires and performance in a working memory (WM) task) in healthy volunteers, while MF was induced by Sudoku tasks performed for 120 min. Moreover extrinsic motivation was manipulated by using different levels of monetary reward. We found that, during the course of the experiment, the participants' subjective feeling of fatigue increased and their performance worsened while their blink rate and heart rate variability (HRV) increased. Conversely, reward-induced EEG, pupillometric and skin conductance signal changes, regarded as indicators of task engagement, remained constant during the experiment, and failed to correlate with the indices of MF. In addition, MF did not affect a simple reaction time task, despite the strong influence of extrinsic motivation on this task. Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF. These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mental fatigue (MF) is commonly observed following prolonged cognitive activity and can have major repercussions on the daily life of patients as well as healthy individuals. Despite its important impact, the cognitive processes involved in MF remain largely unknown. An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement. Here, to test this hypothesis, we measured various neural, autonomic, psychometric and behavioral signatures of MF and motivation (EEG, ECG, pupil size, eye blinks, Skin conductance responses (SCRs), questionnaires and performance in a working memory (WM) task) in healthy volunteers, while MF was induced by Sudoku tasks performed for 120 min. Moreover extrinsic motivation was manipulated by using different levels of monetary reward. We found that, during the course of the experiment, the participants' subjective feeling of fatigue increased and their performance worsened while their blink rate and heart rate variability (HRV) increased. Conversely, reward-induced EEG, pupillometric and skin conductance signal changes, regarded as indicators of task engagement, remained constant during the experiment, and failed to correlate with the indices of MF. In addition, MF did not affect a simple reaction time task, despite the strong influence of extrinsic motivation on this task. Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF. These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources. |
Marcello Giannini; David M Alexander; Andrey R Nikolaev; Cees van Leeuwen Large-scale traveling waves in EEG activity following eye movement Journal Article Brain Topography, 31 (4), pp. 608–622, 2018. @article{Giannini2018, title = {Large-scale traveling waves in EEG activity following eye movement}, author = {Marcello Giannini and David M Alexander and Andrey R Nikolaev and Cees van Leeuwen}, doi = {10.1007/s10548-018-0622-2}, year = {2018}, date = {2018-01-01}, journal = {Brain Topography}, volume = {31}, number = {4}, pages = {608--622}, publisher = {Springer US}, abstract = {In spontaneous, stimulus-evoked, and eye-movement evoked EEG, the oscillatory signal shows large scale, dynamically organized patterns of phase. We investigated eye-movement evoked patterns in free-viewing conditions. Participants viewed photographs of natural scenes in anticipation of a memory test. From 200 ms intervals following saccades, we estimated the EEG phase gradient over the entire scalp, and the wave activity, i.e. the goodness of fit of a wave model involving a phase gradient assumed to be smooth over the scalp. In frequencies centered at 6.5 Hz, large-scale phase organization occurred, peaking around 70 ms after fixation onset and taking the form of a traveling wave. According to the wave gradient, most of the times the wave spreads from the posterior-inferior to anterior–superior direction. In these directions, the gradients depended on the size and direction of the saccade. Wave propagation velocity decreased in the course of the fixation, particularly in the interval from 50 to 150 ms after fixation onset. This interval corresponds to the fixation-related lambda activity, which reflects early perceptual processes following fixation onset. We conclude that lambda activity has a prominent traveling wave component. This component consists of a short-term whole-head phase pattern of specific direction and velocity, which may reflect feedforward propagation of visual information at fixation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In spontaneous, stimulus-evoked, and eye-movement evoked EEG, the oscillatory signal shows large scale, dynamically organized patterns of phase. We investigated eye-movement evoked patterns in free-viewing conditions. Participants viewed photographs of natural scenes in anticipation of a memory test. From 200 ms intervals following saccades, we estimated the EEG phase gradient over the entire scalp, and the wave activity, i.e. the goodness of fit of a wave model involving a phase gradient assumed to be smooth over the scalp. In frequencies centered at 6.5 Hz, large-scale phase organization occurred, peaking around 70 ms after fixation onset and taking the form of a traveling wave. According to the wave gradient, most of the times the wave spreads from the posterior-inferior to anterior–superior direction. In these directions, the gradients depended on the size and direction of the saccade. Wave propagation velocity decreased in the course of the fixation, particularly in the interval from 50 to 150 ms after fixation onset. This interval corresponds to the fixation-related lambda activity, which reflects early perceptual processes following fixation onset. We conclude that lambda activity has a prominent traveling wave component. This component consists of a short-term whole-head phase pattern of specific direction and velocity, which may reflect feedforward propagation of visual information at fixation. |
Lauren R Godier; Jessica C Scaife; Sven Braeutigam; Rebecca J Park Enhanced early neuronal processing of food pictures in Anorexia Nervosa: A magnetoencephalography study Journal Article Psychiatry Journal, 2016 , pp. 1–13, 2016. @article{Godier2016, title = {Enhanced early neuronal processing of food pictures in Anorexia Nervosa: A magnetoencephalography study}, author = {Lauren R Godier and Jessica C Scaife and Sven Braeutigam and Rebecca J Park}, url = {http://www.hindawi.com/journals/psychiatry/2016/1795901/}, doi = {10.1155/2016/1795901}, year = {2016}, date = {2016-01-01}, journal = {Psychiatry Journal}, volume = {2016}, pages = {1--13}, abstract = {Neuroimaging studies in Anorexia Nervosa (AN) have shown increased activation in reward and cognitive control regions in response to food, and a behavioral attentional bias (AB) towards food stimuli is reported. This study aimed to further investigate the neural processing of food using magnetoencephalography (MEG). Participants were 13 females with restricting-type AN, 14 females recovered from restricting-type AN, and 15 female healthy controls. MEG data was acquired whilst participants viewed high- and low-calorie food pictures. Attention was assessed with a reaction time task and eye tracking. Time-series analysis suggested increased neural activity in response to both calorie conditions in the AN groups, consistent with an early AB. Increased activity was observed at 150 ms in the current AN group. Neuronal activity at this latency was at normal level in the recovered group; however, this group exhibited enhanced activity at 320 ms after stimulus. Consistent with previous studies, analysis in source space and behavioral data suggested enhanced attention and cognitive control processes in response to food stimuli in AN. This may enable avoidance of salient food stimuli and maintenance of dietary restraint in AN. A later latency of increased activity in the recovered group may reflect a reversal of this avoidance, with source space and behavioral data indicating increased visual and cognitive processing of food stimuli.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Neuroimaging studies in Anorexia Nervosa (AN) have shown increased activation in reward and cognitive control regions in response to food, and a behavioral attentional bias (AB) towards food stimuli is reported. This study aimed to further investigate the neural processing of food using magnetoencephalography (MEG). Participants were 13 females with restricting-type AN, 14 females recovered from restricting-type AN, and 15 female healthy controls. MEG data was acquired whilst participants viewed high- and low-calorie food pictures. Attention was assessed with a reaction time task and eye tracking. Time-series analysis suggested increased neural activity in response to both calorie conditions in the AN groups, consistent with an early AB. Increased activity was observed at 150 ms in the current AN group. Neuronal activity at this latency was at normal level in the recovered group; however, this group exhibited enhanced activity at 320 ms after stimulus. Consistent with previous studies, analysis in source space and behavioral data suggested enhanced attention and cognitive control processes in response to food stimuli in AN. This may enable avoidance of salient food stimuli and maintenance of dietary restraint in AN. A later latency of increased activity in the recovered group may reflect a reversal of this avoidance, with source space and behavioral data indicating increased visual and cognitive processing of food stimuli. |
Tal Golan; Ido Davidesco; Meir Meshulam; David M Groppe; Pierre Mégevand; Erin M Yeagle; Matthew S Goldfinger; Michal Harel; Lucia Melloni; Charles E Schroeder; D L Deouell; Ashesh D Mehta; Rafael Malach Human intracranial recordings link suppressed transients rather than 'filling-in' to perceptual continuity across blinks Journal Article eLife, 5 , pp. 1–28, 2016. @article{Golan2016, title = {Human intracranial recordings link suppressed transients rather than 'filling-in' to perceptual continuity across blinks}, author = {Tal Golan and Ido Davidesco and Meir Meshulam and David M Groppe and Pierre Mégevand and Erin M Yeagle and Matthew S Goldfinger and Michal Harel and Lucia Melloni and Charles E Schroeder and D L Deouell and Ashesh D Mehta and Rafael Malach}, doi = {10.7554/eLife.17243}, year = {2016}, date = {2016-01-01}, journal = {eLife}, volume = {5}, pages = {1--28}, abstract = {We hardly notice our eye blinks, yet an externally generated retinal interruption of a similar duration is perceptually salient. We examined the neural correlates of this perceptual distinction using intracranially measured ECoG signals from human visual cortex in 14 patients. In early visual areas (V1 and V2), the disappearance of the stimulus due to either invisible blinks or salient blank video frames ('gaps') led to a similar drop in activity level, followed by a positive overshoot beyond baseline, triggered by stimulus reappearance. Ascending the visual hierarchy, the reappearance-related overshoot gradually subsided for blinks but not for gaps. By contrast, the disappearance-related drop did not follow the perceptual distinction - it was actually slightly more pronounced for blinks than for gaps. These findings suggest that blinks' limited visibility compared with gaps is correlated with suppression of blink-related visual activity transients, rather than with 'filling-in' of the occluded content during blinks.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We hardly notice our eye blinks, yet an externally generated retinal interruption of a similar duration is perceptually salient. We examined the neural correlates of this perceptual distinction using intracranially measured ECoG signals from human visual cortex in 14 patients. In early visual areas (V1 and V2), the disappearance of the stimulus due to either invisible blinks or salient blank video frames ('gaps') led to a similar drop in activity level, followed by a positive overshoot beyond baseline, triggered by stimulus reappearance. Ascending the visual hierarchy, the reappearance-related overshoot gradually subsided for blinks but not for gaps. By contrast, the disappearance-related drop did not follow the perceptual distinction - it was actually slightly more pronounced for blinks than for gaps. These findings suggest that blinks' limited visibility compared with gaps is correlated with suppression of blink-related visual activity transients, rather than with 'filling-in' of the occluded content during blinks. |
Gil Gonen-Yaacovi; Ayelet Arazi; Nitzan Shahar; Anat Karmon; Shlomi Haar; Nachshon Meiran; Ilan Dinstein Increased ongoing neural variability in ADHD Journal Article Cortex, 81 , pp. 50–63, 2016. @article{Gonen-Yaacovi2016, title = {Increased ongoing neural variability in ADHD}, author = {Gil Gonen-Yaacovi and Ayelet Arazi and Nitzan Shahar and Anat Karmon and Shlomi Haar and Nachshon Meiran and Ilan Dinstein}, url = {http://dx.doi.org/10.1016/j.cortex.2016.04.010}, doi = {10.1016/j.cortex.2016.04.010}, year = {2016}, date = {2016-01-01}, journal = {Cortex}, volume = {81}, pages = {50--63}, publisher = {Elsevier Ltd}, abstract = {Attention Deficit Hyperactivity Disorder (ADHD) has been described as a disorder where frequent lapses of attention impair the ability of an individual to focus/attend in a sustained manner, thereby generating abnormally large intra-individual behavioral variability across trials. Indeed, increased reaction time (RT) variability is a fundamental behavioral characteristic of individuals with ADHD found across a large number of cognitive tasks. But what is the underlying neurophysiology that might generate such behavioral instability? Here, we examined trial-by-trial EEG response variability to visual and auditory stimuli while subjects' attention was diverted to an unrelated task at the fixation cross. Comparisons between adult ADHD and control participants revealed that neural response variability was significantly larger in the ADHD group as compared with the control group in both sensory modalities. Importantly, larger trial-by-trial variability in ADHD was apparent before and after stimulus presentation as well as in trials where the stimulus was omitted, suggesting that ongoing (rather than stimulus-evoked) neural activity is continuously more variable (noisier) in ADHD. While the patho-physiological mechanisms causing this increased neural variability remain unknown, they appear to act continuously rather than being tied to a specific sensory or cognitive process.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Attention Deficit Hyperactivity Disorder (ADHD) has been described as a disorder where frequent lapses of attention impair the ability of an individual to focus/attend in a sustained manner, thereby generating abnormally large intra-individual behavioral variability across trials. Indeed, increased reaction time (RT) variability is a fundamental behavioral characteristic of individuals with ADHD found across a large number of cognitive tasks. But what is the underlying neurophysiology that might generate such behavioral instability? Here, we examined trial-by-trial EEG response variability to visual and auditory stimuli while subjects' attention was diverted to an unrelated task at the fixation cross. Comparisons between adult ADHD and control participants revealed that neural response variability was significantly larger in the ADHD group as compared with the control group in both sensory modalities. Importantly, larger trial-by-trial variability in ADHD was apparent before and after stimulus presentation as well as in trials where the stimulus was omitted, suggesting that ongoing (rather than stimulus-evoked) neural activity is continuously more variable (noisier) in ADHD. While the patho-physiological mechanisms causing this increased neural variability remain unknown, they appear to act continuously rather than being tied to a specific sensory or cognitive process. |
Tom A de Graaf; Felix Duecker; Martin H P Fernholz; Alexander T Sack Spatially specific vs. unspecific disruption of visual orientation perception using chronometric pre-stimulus TMS Journal Article Frontiers in Behavioral Neuroscience, 9 (5), pp. 1–11, 2015. @article{Graaf2015, title = {Spatially specific vs. unspecific disruption of visual orientation perception using chronometric pre-stimulus TMS}, author = {Tom A de Graaf and Felix Duecker and Martin H P Fernholz and Alexander T Sack}, url = {http://journal.frontiersin.org/article/10.3389/fnbeh.2015.00005/abstract}, doi = {10.3389/fnbeh.2015.00005}, year = {2015}, date = {2015-01-01}, journal = {Frontiers in Behavioral Neuroscience}, volume = {9}, number = {5}, pages = {1--11}, abstract = {Transcranial magnetic stimulation (TMS) over occipital cortex can impair visual processing. Such ‘TMS masking' has repeatedly been shown at several stimulus onset asynchronies (SOAs), with TMS pulses generally applied after the onset of a visual stimulus. Following increased interest in the neuronal state-dependency of visual processing, we recently explored the efficacy of TMS at ‘negative SOAs', when no visual processing can yet occur. We could reveal pre-stimulus TMS disruption, with results moreover hinting at two separate mechanisms in occipital cortex biasing subsequent orientation perception. Here we extended this work, including a chronometric design to map the temporal dynamics of spatially specific and unspecific mechanisms of state-dependent visual processing, while moreover controlling for TMS-induced pupil covering. TMS pulses applied 60-40 ms prior to a visual stimulus decreased orientation processing independent of stimulus location, while a local suppressive effect was found for TMS applied 30-10 ms pre-stimulus. These results contribute to our understanding of spatiotemporal mechanisms in occipital cortex underlying the state-dependency of visual processing, providing a basis for future work to link pre-stimulus TMS suppression effects to other known visual biasing mechanisms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Transcranial magnetic stimulation (TMS) over occipital cortex can impair visual processing. Such ‘TMS masking' has repeatedly been shown at several stimulus onset asynchronies (SOAs), with TMS pulses generally applied after the onset of a visual stimulus. Following increased interest in the neuronal state-dependency of visual processing, we recently explored the efficacy of TMS at ‘negative SOAs', when no visual processing can yet occur. We could reveal pre-stimulus TMS disruption, with results moreover hinting at two separate mechanisms in occipital cortex biasing subsequent orientation perception. Here we extended this work, including a chronometric design to map the temporal dynamics of spatially specific and unspecific mechanisms of state-dependent visual processing, while moreover controlling for TMS-induced pupil covering. TMS pulses applied 60-40 ms prior to a visual stimulus decreased orientation processing independent of stimulus location, while a local suppressive effect was found for TMS applied 30-10 ms pre-stimulus. These results contribute to our understanding of spatiotemporal mechanisms in occipital cortex underlying the state-dependency of visual processing, providing a basis for future work to link pre-stimulus TMS suppression effects to other known visual biasing mechanisms. |
Sven-Thomas Graupner; Boris M Velichkovsky; Sebastian Pannasch; Johannes Marx Surprise, surprise: Two distinct components in the visually evoked distractor effect Journal Article Psychophysiology, 44 (2), pp. 251–261, 2007. @article{Graupner2007, title = {Surprise, surprise: Two distinct components in the visually evoked distractor effect}, author = {Sven-Thomas Graupner and Boris M Velichkovsky and Sebastian Pannasch and Johannes Marx}, doi = {10.1111/j.1469-8986.2007.00504.x}, year = {2007}, date = {2007-01-01}, journal = {Psychophysiology}, volume = {44}, number = {2}, pages = {251--261}, abstract = {The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found. |
Sven-Thomas Graupner; Sebastian Pannasch; Boris M Velichkovsky International Journal of Psychophysiology, 80 (1), pp. 54–62, 2011. @article{Graupner2011, title = {Saccadic context indicates information processing within visual fixations: Evidence from event-related potentials and eye-movements analysis of the distractor effect}, author = {Sven-Thomas Graupner and Sebastian Pannasch and Boris M Velichkovsky}, url = {http://dx.doi.org/10.1016/j.ijpsycho.2011.01.013}, doi = {10.1016/j.ijpsycho.2011.01.013}, year = {2011}, date = {2011-01-01}, journal = {International Journal of Psychophysiology}, volume = {80}, number = {1}, pages = {54--62}, publisher = {Elsevier B.V.}, abstract = {Attention, visual information processing, and oculomotor control are integrated functions of closely related brain mechanisms. Recently, it was shown that the processing of visual distractors appearing during a fixation is modulated by the amplitude of its preceding saccade (Pannasch & Velichkovsky, 2009). So far, this was demonstrated only at the behavioral level in terms of saccadic inhibition. The present study investigated distractor-related brain activity with cortical eye fixation-related potentials (EFRPs). Moreover, the following saccade was included as an additional classification criterion. Eye movements and EFRPs were recorded during free visual exploration of paintings. During some of the fixations, a visual distractor was shown as an annulus around the fixation position, 100. ms after the fixation onset. The saccadic context of a fixation was classified by its preceding and following saccade amplitudes with the cut-off criterion set to 4° of visual angle. The prolongation of fixation duration induced by distractors was largest for fixations preceded and followed by short saccades. EFRP data revealed a difference in distractor-related P2 amplitude between the saccadic context conditions, following the same trend as in eye movements. Furthermore, influences of the following saccade amplitude on the latency of the saccadic inhibition and on the N1 amplitude were found. The EFRP results cannot be explained by the influence of saccades per se since this bias was removed by subtracting the baseline from the distractor EFRP. Rather, the data suggest that saccadic context indicates differences in how information is processed within single visual fixations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Attention, visual information processing, and oculomotor control are integrated functions of closely related brain mechanisms. Recently, it was shown that the processing of visual distractors appearing during a fixation is modulated by the amplitude of its preceding saccade (Pannasch & Velichkovsky, 2009). So far, this was demonstrated only at the behavioral level in terms of saccadic inhibition. The present study investigated distractor-related brain activity with cortical eye fixation-related potentials (EFRPs). Moreover, the following saccade was included as an additional classification criterion. Eye movements and EFRPs were recorded during free visual exploration of paintings. During some of the fixations, a visual distractor was shown as an annulus around the fixation position, 100. ms after the fixation onset. The saccadic context of a fixation was classified by its preceding and following saccade amplitudes with the cut-off criterion set to 4° of visual angle. The prolongation of fixation duration induced by distractors was largest for fixations preceded and followed by short saccades. EFRP data revealed a difference in distractor-related P2 amplitude between the saccadic context conditions, following the same trend as in eye movements. Furthermore, influences of the following saccade amplitude on the latency of the saccadic inhibition and on the N1 amplitude were found. The EFRP results cannot be explained by the influence of saccades per se since this bias was removed by subtracting the baseline from the distractor EFRP. Rather, the data suggest that saccadic context indicates differences in how information is processed within single visual fixations. |
Sarah Gregory; Marco Fusca; Geraint Rees; Samuel D Schwarzkopf; Gareth Barnes Gamma frequency and the spatial tuning of primary visual cortex Journal Article PLoS ONE, 11 (6), pp. 1–12, 2016. @article{Gregory2016a, title = {Gamma frequency and the spatial tuning of primary visual cortex}, author = {Sarah Gregory and Marco Fusca and Geraint Rees and Samuel D Schwarzkopf and Gareth Barnes}, doi = {10.1371/journal.pone.0157374}, year = {2016}, date = {2016-01-01}, journal = {PLoS ONE}, volume = {11}, number = {6}, pages = {1--12}, abstract = {Visual stimulation produces oscillatory gamma responses in human primary visual cortex (V1) that also relate to visual perception. We have shown previously that peak gamma frequency positively correlates with central V1 cortical surface area. We hypothesized that people with larger V1 would have smaller receptive fields and that receptive field size, not V1 are, might explain this relationship. Here we set out to test this hypothesis directly by investigating the relationship between fMRI estimated population receptive field (pRF) size and gamma frequency in V1. We stimulated both the near-centre and periphery of the visual field using both large and small stimuli in each location and replicated our previous finding of a positive correlation between V1 surface area and peak gamma frequency. Counter to our expectation, we found that between participants V1 size (and not pRF size) accounted for most of the variability in gamma frequency. Within-participants we found that gamma frequency increased, rather than decreased, with stimulus eccentricity directly contradicting our initial hypothesis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Visual stimulation produces oscillatory gamma responses in human primary visual cortex (V1) that also relate to visual perception. We have shown previously that peak gamma frequency positively correlates with central V1 cortical surface area. We hypothesized that people with larger V1 would have smaller receptive fields and that receptive field size, not V1 are, might explain this relationship. Here we set out to test this hypothesis directly by investigating the relationship between fMRI estimated population receptive field (pRF) size and gamma frequency in V1. We stimulated both the near-centre and periphery of the visual field using both large and small stimuli in each location and replicated our previous finding of a positive correlation between V1 surface area and peak gamma frequency. Counter to our expectation, we found that between participants V1 size (and not pRF size) accounted for most of the variability in gamma frequency. Within-participants we found that gamma frequency increased, rather than decreased, with stimulus eccentricity directly contradicting our initial hypothesis. |
M Guitart-Masip; G R Barnes; A Horner; Markus Bauer; R J Dolan; E Duzel Synchronization of medial temporal lobe and prefrontal rhythms in human decision making Journal Article Journal of Neuroscience, 33 (2), pp. 442–451, 2013. @article{Guitart-Masip2013, title = {Synchronization of medial temporal lobe and prefrontal rhythms in human decision making}, author = {M Guitart-Masip and G R Barnes and A Horner and Markus Bauer and R J Dolan and E Duzel}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.2573-12.2013}, doi = {10.1523/JNEUROSCI.2573-12.2013}, year = {2013}, date = {2013-01-01}, journal = {Journal of Neuroscience}, volume = {33}, number = {2}, pages = {442--451}, abstract = {Optimal decision making requires that we integrate mnemonic information regarding previous decisions with value signals that entail likely rewards and punishments. The fact that memory and value signals appear to be coded by segregated brain regions, the hippocampus in the case of memory and sectors of prefrontal cortex in the case of value, raises the question as to how they are integrated during human decision making. Using magnetoencephalography to study healthy human participants, we show increased theta oscillations over frontal and temporal sensors during nonspatial decisions based on memories from previous trials. Using source reconstruction we found that the medial temporal lobe (MTL), in a location compatible with the anterior hippocampus, and the anterior cingulate cortex in the medial wall of the frontal lobe are the source of this increased theta power. Moreover, we observed a correlation between theta power in the MTL source and behavioral performance in decision making, supporting a role for MTL theta oscillations in decision-making performance. These MTL theta oscillations were synchronized with several prefrontal sources, including lateral superior frontal gyrus, dorsal anterior cingulate gyrus, and medial frontopolar cortex. There was no relationship between the strength of synchronization and the expected value of choices. Our results indicate a mnemonic guidance of human decision making, beyond anticipation of expected reward, is supported by hippocampal-prefrontal theta synchronization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Optimal decision making requires that we integrate mnemonic information regarding previous decisions with value signals that entail likely rewards and punishments. The fact that memory and value signals appear to be coded by segregated brain regions, the hippocampus in the case of memory and sectors of prefrontal cortex in the case of value, raises the question as to how they are integrated during human decision making. Using magnetoencephalography to study healthy human participants, we show increased theta oscillations over frontal and temporal sensors during nonspatial decisions based on memories from previous trials. Using source reconstruction we found that the medial temporal lobe (MTL), in a location compatible with the anterior hippocampus, and the anterior cingulate cortex in the medial wall of the frontal lobe are the source of this increased theta power. Moreover, we observed a correlation between theta power in the MTL source and behavioral performance in decision making, supporting a role for MTL theta oscillations in decision-making performance. These MTL theta oscillations were synchronized with several prefrontal sources, including lateral superior frontal gyrus, dorsal anterior cingulate gyrus, and medial frontopolar cortex. There was no relationship between the strength of synchronization and the expected value of choices. Our results indicate a mnemonic guidance of human decision making, beyond anticipation of expected reward, is supported by hippocampal-prefrontal theta synchronization. |
Seref Can Gurel; Miguel Castelo-Branco; Alexander T Sack; Felix Duecker Assessing the functional role of frontal eye fields in voluntary and reflexive saccades using continuous theta burst stimulation Journal Article Frontiers in Neuroscience, 12 , pp. 1–11, 2018. @article{Gurel2018, title = {Assessing the functional role of frontal eye fields in voluntary and reflexive saccades using continuous theta burst stimulation}, author = {Seref Can Gurel and Miguel Castelo-Branco and Alexander T Sack and Felix Duecker}, doi = {10.3389/fnins.2018.00944}, year = {2018}, date = {2018-01-01}, journal = {Frontiers in Neuroscience}, volume = {12}, pages = {1--11}, abstract = {The frontal eye fields (FEFs) are core nodes of the oculomotor system contributing to saccade planning, control, and execution. Here, we aimed to reveal hemispheric asymmetries between left and right FEF in both voluntary and reflexive saccades toward horizontal and vertical targets. To this end, we applied fMRI-guided continuous theta burst stimulation (cTBS) over either left or right FEF and assessed the consequences of this disruption on saccade latencies. Using a fully counterbalanced within-subject design, we measured saccade latencies before and after the application of cTBS in eighteen healthy volunteers. In general, saccade latencies on both tasks were susceptible to our experimental manipulations, that is, voluntary saccades were slower than reflexive saccades, and downward saccades were slower than upward saccades. Contrary to our expectations, we failed to reveal any TMS-related effects on saccade latencies, and Bayesian analyses provided strong support in favor of a TMS null result for both tasks. Keeping in mind the interpretative challenges of null results, we discuss possible explanations for this absence of behavioral TMS effects, focusing on methodological differences compared to previous studies (task parameters and online vs. offline TMS interventions). We also speculate about what our results might reveal about the functional role of FEF.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The frontal eye fields (FEFs) are core nodes of the oculomotor system contributing to saccade planning, control, and execution. Here, we aimed to reveal hemispheric asymmetries between left and right FEF in both voluntary and reflexive saccades toward horizontal and vertical targets. To this end, we applied fMRI-guided continuous theta burst stimulation (cTBS) over either left or right FEF and assessed the consequences of this disruption on saccade latencies. Using a fully counterbalanced within-subject design, we measured saccade latencies before and after the application of cTBS in eighteen healthy volunteers. In general, saccade latencies on both tasks were susceptible to our experimental manipulations, that is, voluntary saccades were slower than reflexive saccades, and downward saccades were slower than upward saccades. Contrary to our expectations, we failed to reveal any TMS-related effects on saccade latencies, and Bayesian analyses provided strong support in favor of a TMS null result for both tasks. Keeping in mind the interpretative challenges of null results, we discuss possible explanations for this absence of behavioral TMS effects, focusing on methodological differences compared to previous studies (task parameters and online vs. offline TMS interventions). We also speculate about what our results might reveal about the functional role of FEF. |
Tjerk P Gutteling; Helene M Van Ettinger-Veenstra; Leon J Kenemans; Sebastiaan F W Neggers Journal of Cognitive Neuroscience, 22 (9), pp. 1931–1943, 2010. @article{Gutteling2010, title = {Lateralized frontal eye field activity precedes occipital activity shortly before saccades: Evidence for cortico-cortical feedback as a mechanism underlying covert attention shifts}, author = {Tjerk P Gutteling and Helene M {Van Ettinger-Veenstra} and Leon J Kenemans and Sebastiaan F W Neggers}, doi = {10.1162/jocn.2009.21342}, year = {2010}, date = {2010-01-01}, journal = {Journal of Cognitive Neuroscience}, volume = {22}, number = {9}, pages = {1931--1943}, abstract = {When an eye movement is prepared, attention is shifted toward the saccade end-goal. This coupling of eye movements and spatial attention is thought to be mediated by cortical connections between the FEFs and the visual cortex. Here, we present evidence for the existence of these connections. A visual discrimination task was performed while recording the EEG. Discrimination performance was significantly improved when the discrimination target and the saccade target matched. EEG results show that frontal activity precedes occipital activity contralateral to saccade direction when the saccade is prepared but not yet executed; these effects were absent in fixation conditions. This is consistent with the idea that the FEF exerts a direct modulatory influence on the visual cortex and enhances perception at the saccade end-goal.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When an eye movement is prepared, attention is shifted toward the saccade end-goal. This coupling of eye movements and spatial attention is thought to be mediated by cortical connections between the FEFs and the visual cortex. Here, we present evidence for the existence of these connections. A visual discrimination task was performed while recording the EEG. Discrimination performance was significantly improved when the discrimination target and the saccade target matched. EEG results show that frontal activity precedes occipital activity contralateral to saccade direction when the saccade is prepared but not yet executed; these effects were absent in fixation conditions. This is consistent with the idea that the FEF exerts a direct modulatory influence on the visual cortex and enhances perception at the saccade end-goal. |
T P Gutteling; L P Selen; W P Medendorp Parallax-sensitive remapping of visual space in occipito-parietal alpha-band activity during whole-body motion Journal Article Journal of Neurophysiology, 113 , pp. 1574–1584, 2015. @article{Gutteling2015, title = {Parallax-sensitive remapping of visual space in occipito-parietal alpha-band activity during whole-body motion}, author = {T P Gutteling and L P Selen and W P Medendorp}, year = {2015}, date = {2015-01-01}, journal = {Journal of Neurophysiology}, volume = {113}, pages = {1574--1584}, abstract = {Despite the constantly changing retinal image due to eye, head, and body movements, we are able to maintain a stable representation of the visual environment. Various studies on retinal image shifts caused by saccades have suggested that occipital and parietal areas correct for these perturbations by a gaze-centered remapping of the neural image. However, such a uniform, rotational, remapping mechanism cannot work during translations when objects shift on the retina in a more complex, depth-dependent fashion due to motion parallax. Here we tested whether the brain's activity patterns show parallax-sensitive remapping of remembered visual space during whole-body motion. Under continuous recording of electroencephalography (EEG), we passively translated human subjects while they had to remember the location of a world-fixed visual target, briefly presented in front of or behind the eyes' fixation point prior to the motion. Using a psychometric approach we assessed the quality of the memory update, which had to be made based on vestibular feedback and other extraretinal motion cues. All subjects showed a variable amount of parallax-sensitive updating errors, i.e., the direction of the errors depended on the depth of the target relative to fixation. The EEG recordings show a neural correlate of this parallax-sensitive remapping in the alpha-band power at occipito-parietal electrodes. At parietal electrodes, the strength of these alpha-band modulations correlated significantly with updating performance. These results suggest that alpha-band oscillatory activity reflects the time-varying updating of gaze-centered spatial information during parallax-sensitive remapping during whole-body motion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Despite the constantly changing retinal image due to eye, head, and body movements, we are able to maintain a stable representation of the visual environment. Various studies on retinal image shifts caused by saccades have suggested that occipital and parietal areas correct for these perturbations by a gaze-centered remapping of the neural image. However, such a uniform, rotational, remapping mechanism cannot work during translations when objects shift on the retina in a more complex, depth-dependent fashion due to motion parallax. Here we tested whether the brain's activity patterns show parallax-sensitive remapping of remembered visual space during whole-body motion. Under continuous recording of electroencephalography (EEG), we passively translated human subjects while they had to remember the location of a world-fixed visual target, briefly presented in front of or behind the eyes' fixation point prior to the motion. Using a psychometric approach we assessed the quality of the memory update, which had to be made based on vestibular feedback and other extraretinal motion cues. All subjects showed a variable amount of parallax-sensitive updating errors, i.e., the direction of the errors depended on the depth of the target relative to fixation. The EEG recordings show a neural correlate of this parallax-sensitive remapping in the alpha-band power at occipito-parietal electrodes. At parietal electrodes, the strength of these alpha-band modulations correlated significantly with updating performance. These results suggest that alpha-band oscillatory activity reflects the time-varying updating of gaze-centered spatial information during parallax-sensitive remapping during whole-body motion. |
Tjerk P Gutteling; W P Medendorp Role of alpha-band oscillations in spatial updating across whole body motion Journal Article Frontiers in Psychology, 7 , pp. 1–12, 2016. @article{Gutteling2016, title = {Role of alpha-band oscillations in spatial updating across whole body motion}, author = {Tjerk P Gutteling and W P Medendorp}, doi = {10.3389/fpsyg.2016.00671}, year = {2016}, date = {2016-01-01}, journal = {Frontiers in Psychology}, volume = {7}, pages = {1--12}, abstract = {When moving around in the world, we have to keep track of important locations in our surroundings. In this process, called spatial updating, we must estimate our body motion and correct representations of memorized spatial locations in accordance with this motion. While the behavioral characteristics of spatial updating across whole body motion have been studied in detail, its neural implementation lacks detailed study. Here we use electro-encephalography (EEG) to distinguish various spectral components of this process. Subjects gazed at a central body-fixed point in otherwise complete darkness, while a target was briefly flashed, either left or right from this point. Subjects had to remember the location of this target as either moving along with the body or remaining fixed in the world while being translated sideways on a passive motion platform. After the motion, subjects had to indicate the remembered target location in the instructed reference frame using a mouse response. While the body motion, as detected by the vestibular system, should not affect the representation of body-fixed targets, it should interact with the representation of a world-centered target to update its location relative to the body. We show that the initial presentation of the visual target induced a reduction of alpha band power in contralateral parieto-occipital areas, which evolved to a sustained increase during the subsequent memory period. Motion of the body led to a reduction of alpha band power in central parietal areas extending to lateral parieto-temporal areas, irrespective of whether the targets had to be memorized relative to world or body. When updating a world-fixed target, its internal representation shifts hemispheres, only when subjects' behavioral responses suggested an update across the body midline. Our results suggest that parietal cortex is involved in both self-motion estimation and the selective application of this motion information to maintaining target locations as fixed in the world or fixed to the body.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When moving around in the world, we have to keep track of important locations in our surroundings. In this process, called spatial updating, we must estimate our body motion and correct representations of memorized spatial locations in accordance with this motion. While the behavioral characteristics of spatial updating across whole body motion have been studied in detail, its neural implementation lacks detailed study. Here we use electro-encephalography (EEG) to distinguish various spectral components of this process. Subjects gazed at a central body-fixed point in otherwise complete darkness, while a target was briefly flashed, either left or right from this point. Subjects had to remember the location of this target as either moving along with the body or remaining fixed in the world while being translated sideways on a passive motion platform. After the motion, subjects had to indicate the remembered target location in the instructed reference frame using a mouse response. While the body motion, as detected by the vestibular system, should not affect the representation of body-fixed targets, it should interact with the representation of a world-centered target to update its location relative to the body. We show that the initial presentation of the visual target induced a reduction of alpha band power in contralateral parieto-occipital areas, which evolved to a sustained increase during the subsequent memory period. Motion of the body led to a reduction of alpha band power in central parietal areas extending to lateral parieto-temporal areas, irrespective of whether the targets had to be memorized relative to world or body. When updating a world-fixed target, its internal representation shifts hemispheres, only when subjects' behavioral responses suggested an update across the body midline. Our results suggest that parietal cortex is involved in both self-motion estimation and the selective application of this motion information to maintaining target locations as fixed in the world or fixed to the body. |
Julia Habicht; Mareike Finke; Tobias Neher Auditory acclimatization to bilateral hearing aids: Effects on sentence-in-noise processing times and speech-evoked potentials Journal Article Ear and Hearing, 39 (1), pp. 161–171, 2018. @article{Habicht2018, title = {Auditory acclimatization to bilateral hearing aids: Effects on sentence-in-noise processing times and speech-evoked potentials}, author = {Julia Habicht and Mareike Finke and Tobias Neher}, doi = {10.1097/AUD.0000000000000476}, year = {2018}, date = {2018-01-01}, journal = {Ear and Hearing}, volume = {39}, number = {1}, pages = {161--171}, abstract = {Objectives: Using a longitudinal design, the present study sought to substantiate indications from two previous cross-sectional studies that hearing aid (HA) experience leads to improved speech processing abilities as quantified using eye-gaze measurements. Another aim was to explore potential concomitant changes in event-related potentials (ERPs) to speech stimuli. Design: Groups of elderly novice (novHA) and experienced (expHA) HA users matched in terms of age and working memory capacity participated. The novHA users were acclimatized to bilateral HA fittings for up to 24 weeks. The expHA users continued to use their own HAs during the same period. The participants' speech processing abilities were assessed after 0 weeks (novHA: N = 16; expHA: N = 14), 12 weeks (novHA: N = 16; expHA: N = 14), and 24 weeks (N = 10 each). To that end, an eye-tracking paradigm was used for estimating how quickly the participants could grasp the meaning of sentences presented against background noise together with two similar pictures that either correctly or incorrectly depicted the meaning conveyed by the sentences (the “processing time”). Additionally, ERPs were measured with an active oddball paradigm requiring the participants to categorize word stimuli as living (targets) or nonliving (nontargets) entities. For all measurements, the stimuli were spectrally shaped according to individual real-ear insertion gains and presented via earphones. Results: Concerning the processing times, no changes across time were found for the expHA group. After 0 weeks of HA use, the novHA group had significantly longer (poorer) processing times than the expHA group, consistent with previous findings. After 24 weeks, a significant mean improvement of ~30% was observed for the novHA users, leading to a performance comparable with that of the expHA group. Concerning the ERPs, no changes across time were found. Conclusions: The results from this exploratory study are consistent with the view that auditory acclimatization to HAs positively impacts speech comprehension in noise. Further research is needed to substantiate them.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objectives: Using a longitudinal design, the present study sought to substantiate indications from two previous cross-sectional studies that hearing aid (HA) experience leads to improved speech processing abilities as quantified using eye-gaze measurements. Another aim was to explore potential concomitant changes in event-related potentials (ERPs) to speech stimuli. Design: Groups of elderly novice (novHA) and experienced (expHA) HA users matched in terms of age and working memory capacity participated. The novHA users were acclimatized to bilateral HA fittings for up to 24 weeks. The expHA users continued to use their own HAs during the same period. The participants' speech processing abilities were assessed after 0 weeks (novHA: N = 16; expHA: N = 14), 12 weeks (novHA: N = 16; expHA: N = 14), and 24 weeks (N = 10 each). To that end, an eye-tracking paradigm was used for estimating how quickly the participants could grasp the meaning of sentences presented against background noise together with two similar pictures that either correctly or incorrectly depicted the meaning conveyed by the sentences (the “processing time”). Additionally, ERPs were measured with an active oddball paradigm requiring the participants to categorize word stimuli as living (targets) or nonliving (nontargets) entities. For all measurements, the stimuli were spectrally shaped according to individual real-ear insertion gains and presented via earphones. Results: Concerning the processing times, no changes across time were found for the expHA group. After 0 weeks of HA use, the novHA group had significantly longer (poorer) processing times than the expHA group, consistent with previous findings. After 24 weeks, a significant mean improvement of ~30% was observed for the novHA users, leading to a performance comparable with that of the expHA group. Concerning the ERPs, no changes across time were found. Conclusions: The results from this exploratory study are consistent with the view that auditory acclimatization to HAs positively impacts speech comprehension in noise. Further research is needed to substantiate them. |
Carlos M Hamamé; Juan R Vidal; Marcela Perrone-Bertolotti; Tomas Ossandón; Karim Jerbi; Philippe Kahane; Olivier Bertrand; Jean Philippe Lachaux Functional selectivity in the human occipitotemporal cortex during natural vision: Evidence from combined intracranial EEG and eye-tracking Journal Article NeuroImage, 95 , pp. 276–286, 2014. @article{Hamame2014, title = {Functional selectivity in the human occipitotemporal cortex during natural vision: Evidence from combined intracranial EEG and eye-tracking}, author = {Carlos M Hamamé and Juan R Vidal and Marcela Perrone-Bertolotti and Tomas Ossandón and Karim Jerbi and Philippe Kahane and Olivier Bertrand and Jean Philippe Lachaux}, url = {http://dx.doi.org/10.1016/j.neuroimage.2014.03.025}, doi = {10.1016/j.neuroimage.2014.03.025}, year = {2014}, date = {2014-01-01}, journal = {NeuroImage}, volume = {95}, pages = {276--286}, publisher = {Elsevier Inc.}, abstract = {Eye movements are a constant and essential component of natural vision, yet, most of our knowledge about the human visual system comes from experiments that restrict them. This experimental constraint is mostly in place to control visual stimuli presentation and to avoid artifacts in non-invasive measures of brain activity, however, this limitation can be overcome with intracranial EEG (iEEG) recorded from epilepsy patients. Moreover, the high-frequency components of the iEEG signal (between about 50 and 150. Hz) can provide a proxy of population-level spiking activity in any cortical area during free-viewing. We combined iEEG with high precision eye-tracking to study fine temporal dynamics and functional specificity in the fusiform face (FFA) and visual word form area (VWFA) while patients inspected natural pictures containing faces and text. We defined the first local measure of visual (electrophysiological) responsiveness adapted to free-viewing in humans: amplitude modulations in the high-frequency activity range (50-150. Hz) following fixations (fixation-related high-frequency response). We showed that despite the large size of receptive fields in the ventral occipito-temporal cortex, neural activity during natural vision of realistic cluttered scenes is mostly dependent upon the category of the foveated stimulus - suggesting that category-specificity is preserved during free-viewing and that attention mechanisms might filter out the influence of objects surrounding the fovea.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Eye movements are a constant and essential component of natural vision, yet, most of our knowledge about the human visual system comes from experiments that restrict them. This experimental constraint is mostly in place to control visual stimuli presentation and to avoid artifacts in non-invasive measures of brain activity, however, this limitation can be overcome with intracranial EEG (iEEG) recorded from epilepsy patients. Moreover, the high-frequency components of the iEEG signal (between about 50 and 150. Hz) can provide a proxy of population-level spiking activity in any cortical area during free-viewing. We combined iEEG with high precision eye-tracking to study fine temporal dynamics and functional specificity in the fusiform face (FFA) and visual word form area (VWFA) while patients inspected natural pictures containing faces and text. We defined the first local measure of visual (electrophysiological) responsiveness adapted to free-viewing in humans: amplitude modulations in the high-frequency activity range (50-150. Hz) following fixations (fixation-related high-frequency response). We showed that despite the large size of receptive fields in the ventral occipito-temporal cortex, neural activity during natural vision of realistic cluttered scenes is mostly dependent upon the category of the foveated stimulus - suggesting that category-specificity is preserved during free-viewing and that attention mechanisms might filter out the influence of objects surrounding the fovea. |
Siobhán Harty; Peter R Murphy; Ian H Robertson; Redmond G O'Connell Parsing the neural signatures of reduced error detection in older age Journal Article NeuroImage, 161 , pp. 43–55, 2017. @article{Harty2017, title = {Parsing the neural signatures of reduced error detection in older age}, author = {Siobhán Harty and Peter R Murphy and Ian H Robertson and Redmond G O'Connell}, doi = {10.1016/j.neuroimage.2017.08.032}, year = {2017}, date = {2017-01-01}, journal = {NeuroImage}, volume = {161}, pages = {43--55}, abstract = {Recent work has demonstrated that explicit error detection relies on a neural evidence accumulation process that can be traced in the human electroencephalogram (EEG). Here, we sought to establish the impact of natural aging on this process by recording EEG from young (18–35 years) and older adults (65–88 years) during the performance of a Go/No-Go paradigm in which participants were required to overtly signal their errors. Despite performing the task with equivalent accuracy, older adults reported substantially fewer errors, and the timing of their reports were both slower and more variable. These behavioral differences were linked to three key neurophysiological changes reflecting distinct parameters of the error detection decision process: a reduction in medial frontal delta/theta (2–7 Hz) activity, indicating diminished top-down input to the decision process; a slower rate of evidence accumulation as indexed by the rate of rise of a centro-parietal signal, known as the error positivity; and a higher motor execution threshold as indexed by lateralized beta-band (16–30 Hz) activity. Our data provide novel insight into how the natural aging process affects the neural underpinnings of error detection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent work has demonstrated that explicit error detection relies on a neural evidence accumulation process that can be traced in the human electroencephalogram (EEG). Here, we sought to establish the impact of natural aging on this process by recording EEG from young (18–35 years) and older adults (65–88 years) during the performance of a Go/No-Go paradigm in which participants were required to overtly signal their errors. Despite performing the task with equivalent accuracy, older adults reported substantially fewer errors, and the timing of their reports were both slower and more variable. These behavioral differences were linked to three key neurophysiological changes reflecting distinct parameters of the error detection decision process: a reduction in medial frontal delta/theta (2–7 Hz) activity, indicating diminished top-down input to the decision process; a slower rate of evidence accumulation as indexed by the rate of rise of a centro-parietal signal, known as the error positivity; and a higher motor execution threshold as indexed by lateralized beta-band (16–30 Hz) activity. Our data provide novel insight into how the natural aging process affects the neural underpinnings of error detection. |