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2014 |
Stephanie Waechter; Andrea L. Nelson; Caitlin A. Wright; Ashley Hyatt; Jonathan Oakman Measuring attentional bias to threat: Reliability of dot probe and eye movement indices Journal Article In: Cognitive Therapy and Research, vol. 38, no. 3, pp. 313–333, 2014. @article{Waechter2014, A variety of methodological paradigms, including dot probe and eye movement tasks, have been used to examine attentional biases to threat in anxiety disorders. Unfortunately, little attention has been devoted to the psychometric properties of measures from these paradigms. In the current study, participants selected for high and low social anxiety completed a dot probe and eye movement task using angry, disgust and happy facial expressions paired with neutral expressions. Results indicated that dot probe bias scores, eye movement first fixa- tion indices, and eye movement proportions of viewing time in the first 1,500 ms had unacceptably low reliability. However, eye movement indices of attentional bias over the full 5,000 ms time course had excellent reliability. Individuals' dot probe and eye movement biases were largely uncorrelated across the two tasks and demonstrated little relation with social anxiety scores. Implications for future research are discussed. |
Angelina Paolozza; Carmen Rasmussen; Jacqueline Pei; Ana Hanlon-Dearman; Sarah M. Nikkel; Gail Andrew; Audrey McFarlane; Dawa Samdup; James N. Reynolds Deficits in response inhibition correlate with oculomotor control in children with fetal alcohol spectrum disorder and prenatal alcohol exposure Journal Article In: Behavioural Brain Research, vol. 259, pp. 97–105, 2014. @article{Paolozza2014, Children with fetal alcohol spectrum disorder (FASD) or prenatal alcohol exposure (PAE) frequently exhibit impairment on tasks measuring inhibition. The objective of this study was to determine if a performance-based relationship exists between psychometric tests and eye movement tasks in children with FASD. Participants for this dataset were aged 5-17 years and included those diagnosed with an FASD (n= 72), those with PAE but no clinical FASD diagnosis (n= 21), and typically developing controls (n= 139). Participants completed a neurobehavioral test battery, which included the NEPSY-II subtests of auditory attention, response set, and inhibition. Each participant completed a series of saccadic eye movement tasks, which included the antisaccade and memory-guided tasks. Both the FASD and the PAE groups performed worse than controls on the subtest measures of attention and inhibition. Compared with controls, the FASD group made more errors on the antisaccade and memory-guided tasks. Among the combined FASD/PAE group, inhibition and switching errors were negatively correlated with direction errors on the antisaccade task but not on the memory-guided task. There were no significant correlations in the control group. These data suggests that response inhibition deficits in children with FASD/PAE are associated with difficulty controlling saccadic eye movements which may point to overlapping brain regions damaged by prenatal alcohol exposure. The results of this study demonstrate that eye movement control tasks directly relate to outcome measures obtained with psychometric tests that are used during FASD diagnosis, and may therefore help with early identification of children who would benefit from a multidisciplinary diagnostic assessment. |
David A. Paul; Elon Gaffin-Cahn; Eric B. Hintz; Giscard J. Adeclat; Tong Zhu; Zoë R. Williams; G. Edward Vates; Bradford Z. Mahon White matter changes linked to visual recovery after nerve decompression Journal Article In: Science Translational Medicine, vol. 6, no. 266, pp. 266ra173, 2014. @article{Paul2014, The relationship between the integrity of white matter tracts and cortical function in the human brain remains poorly understood. We investigate reversible white matter injury, in this case patients with compression of the optic chiasm by pituitary gland tumors, to study the structural and functional changes that attend spontaneous recovery of cortical function and visual abilities after surgical removal of the tumor and subsequent decompression of the nerves. We show that compression of the optic chiasm led to demyelination of the optic tracts, which reversed as quickly as 4 weeks after nerve decompression. Furthermore, variability across patients in the severity of demyelination in the optic tracts predicted visual ability and functional activity in early cortical visual areas. Preoperative measurements of myelination in the optic tracts predicted the magnitude of visual recovery after surgery. These data indicate that rapid regeneration of myelin in the human brain is a component of the normalization of cortical activity, and ultimately the recovery of sensory and cognitive function, after nerve decompression. More generally, our findings demonstrate the use of diffusion tensor imaging as an in vivo measure of myelination in the human brain. |
Andrea Phillipou; Susan Lee Rossell; David Jonathan Castle; Caroline T. Gurvich; Larry Allen Abel Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa Journal Article In: Investigative Ophthalmology & Visual Science, vol. 55, no. 12, pp. 8366–8370, 2014. @article{Phillipou2014, PURPOSE. The factors contributing to the cause and maintenance of anorexia nervosa (AN) are poorly understood, though increasing interest surrounds the neurobiological underpinnings of the condition. The examination of saccadic eye movements has proven useful in our understanding of the neurobiology of some other psychiatric illnesses, as they utilize identifiable brain circuits. Square wave jerks (SWJs), which describe an involuntary saccade away and back to fixation, have been observed to occur at abnormally high rates in neurodegenerative disorders and some psychiatric illnesses, but have not been examined in AN. Therefore, the aim of this study was to investigate whether individuals with AN and healthy control (HC) individuals differ in SWJ rate during attempted fixation. METHODS. Square wave jerk frequency was compared across 23 female participants with AN and 22 HC participants matched for age, sex, and premorbid intelligence. RESULTS. Anorexia nervosa participants were found to make SWJs at a significantly higher rate than HC participants. The rate of SWJs in AN was also found to negatively correlate with anxiety. Square wave jerk rate and anxiety were found to correctly classify groups, with an accuracy of 87% for AN participants and 95.5% for HCs. CONCLUSIONS. Given our current understanding of saccadic eye movements, the findings suggest a potential role of c-aminobutyric acid (GABA) in the superior colliculus, frontal eye fields, or posterior parietal cortex in the psychopathology of AN. |
Elmar H. Pinkhardt; Hazem Issa; Martin Gorges; Reinhart Jürgens; Dorothée Lulé; Johanna Heimrath; Hans Peter Müller; Albert C. Ludolph; Wolfgang Becker; Jan Kassubek In: Journal of Neurology, vol. 261, no. 4, pp. 791–803, 2014. @article{Pinkhardt2014, Small vessel cerebrovascular disease (SVCD) is one of the most frequent vessel disorders in the aged brain. Among the spectrum of neurological disturbances related to SVCD, oculomotor dysfunction is a not well understood symptom- in particular, it remains unclear whether vascular lesion load in specific brain regions affects oculomotor function independent of cognitive decline in SVCD patients or whether the effect of higher brain function deficits prevails. In this study, we examined a cohort of 25 SVCD patients and 19 healthy controls using video-oculographic eye movement recording in a laboratory environment, computer-based MRI assessment of white matter lesion load (WMLL), assessment of extrapyramidal motor deficits, and psychometric testing. In comparison to controls, the mean WMLL of patients was significantly larger than in controls. With respect to eye movement control, patients performed significantly worse than controls in almost all aspects of oculomotion. Likewise, patients showed a significantly worse performance in all but one of the neuropsychological tests. Oculomotor deficits in SVCD correlated with the patients' cognitive dysfunctioning while there was only weak evidence for a direct effect of WMLL on eye movement control. In conclusion, oculomotor impairment in SVCD seems to be mainly contingent upon cognitive deterioration in SVCD while WMLL might have only a minor specific effect upon oculomotor pathways. |
Katrin H. Preller; Marcus Herdener; Leonhard Schilbach; Philliipp Stampfli; Lea M. Hulka; Matthias Vonmoos; Nina Ingold; Kai Vogeley; Philippe N. Tobler; Erich Seifritz; Boris B. Quednow Functional changes of the reward system underlie blunted response to social gaze in cocaine users Journal Article In: Proceedings of the National Academy of Sciences, vol. 111, no. 7, pp. 2842–2847, 2014. @article{Preller2014, Social interaction deficits in drug users likely impede treatment, increase the burden of the affected families, and consequently contribute to the high costs for society associated with addiction. Despite its significance, the neural basis of altered social interaction in drug users is currently unknown. Therefore, we investigated basal social gaze behavior in cocaine users by applying behavioral, psychophysiological, and functional brain-imaging methods. In study I, 80 regular cocaine users and 63 healthy controls completed an interactive paradigm in which the participants' gaze was recorded by an eye-tracking device that controlled the gaze of an anthropomorphic virtual character. Valence ratings of different eye-contact conditions revealed that cocaine users show diminished emotional engagement in social interaction, which was also supported by reduced pupil responses. Study II investigated the neural underpinnings of changes in social reward processing observed in study I. Sixteen cocaine users and 16 controls completed a similar interaction paradigm as used in study I while undergoing functional magnetic resonance imaging. In response to social interaction, cocaine users displayed decreased activation of the medial orbitofrontal cortex, a key region of reward processing. Moreover, blunted activation of the medial orbitofrontal cortex was significantly correlated with a decreased social network size, reflecting problems in real-life social behavior because of reduced social reward. In conclusion, basic social interaction deficits in cocaine users as observed here may arise from altered social reward processing. Consequently, these results point to the importance of reinstatement of social reward in the treatment of stimulant addiction. |
Alby Richard; Jan Churan; Veronica Whitford; Gillian A. O'Driscoll; Debra Titone; Christopher C. Pack Perisaccadic perception of visual space in people with schizophrenia Journal Article In: Journal of Neuroscience, vol. 34, no. 14, pp. 4760–4765, 2014. @article{Richard2014, Corollary discharge signals are found in the nervous systems of many animals, where they serve a large variety of functions related to the integration of sensory and motor signals. In humans, an important corollary discharge signal is generated by oculomotor structures and communicated to sensory systems in concert with the execution of each saccade. This signal is thought to serve a number of purposes related to the maintenance of accurate visual perception. The properties of the oculomotor corollary discharge can be probed by asking subjects to localize stimuli that are flashed briefly around the time of a saccade. The results of such experiments typically reveal large errors in localization. Here, we have exploited these well-known psychophysical effects to assess the potential dysfunction of corollary discharge signals in people with schizophrenia. In a standard perisaccadic localization task, we found that, compared with controls, patients with schizophrenia exhibited larger errors in localizing visual stimuli. The pattern of errors could be modeled as an overdamped corollary discharge signal that encodes instantaneous eye position. The dynamics of this signal predicted symptom severity among patients, suggesting a possible mechanistic basis for widely observed behavioral manifestations of schizophrenia. |
Richard Kunert; Christoph Scheepers Speed and accuracy of dyslexic versus typical word recognition: An eye-movement investigation Journal Article In: Frontiers in Psychology, vol. 5, pp. 1129, 2014. @article{Kunert2014, Developmental dyslexia is often characterized by a dual deficit in both word recognition accuracy and general processing speed. While previous research into dyslexic word recognition may have suffered from speed-accuracy trade-off, the present study employed a novel eye-tracking task that is less prone to such confounds. Participants (10 dyslexics and 12 controls) were asked to look at real word stimuli, and to ignore simultaneously presented non-word stimuli, while their eye-movements were recorded. Improvements in word recognition accuracy over time were modeled in terms of a continuous non-linear function. The words' rhyme consistency and the non-words' lexicality (unpronounceable, pronounceable, pseudohomophone) were manipulated within-subjects. Speed-related measures derived from the model fits confirmed generally slower processing in dyslexics, and showed a rhyme consistency effect in both dyslexics and controls. In terms of overall error rate, dyslexics (but not controls) performed less accurately on rhyme-inconsistent words, suggesting a representational deficit for such words in dyslexics. Interestingly, neither group showed a pseudohomophone effect in speed or accuracy, which might call the task-independent pervasiveness of this effect into question. The present results illustrate the importance of distinguishing between speed- vs. accuracy-related effects for our understanding of dyslexic word recognition. |
Chia-lin Lee; Daniel Mirman; Laurel J. Buxbaum Abnormal dynamics of activation of object use information in apraxia: Evidence from eyetracking Journal Article In: Neuropsychologia, vol. 59, no. 1, pp. 13–26, 2014. @article{Lee2014, Action representations associated with object use may be incidentally activated during visual object processing, and the time course of such activations may be influenced by lexical-semantic context (e.g., Lee, Middleton, Mirman, Kalénine, & Buxbaum (2012). Journal of Experimental Psychology: Human Perception and Performance, 39(1), 257-270). In this study we used the "visual world" eye-tracking paradigm to examine whether a deficit in producing skilled object-use actions (apraxia) is associated with abnormalities in incidental activation of action information, and assessed the neuroanatomical substrates of any such deficits. Twenty left hemisphere stroke patients, ten of whom were apraxic, performed a task requiring identification of a named object in a visual display containing manipulation-related and unrelated distractor objects. Manipulation relationships among objects were not relevant to the identification task. Objects were cued with neutral ("S/he saw the. . .."), or action-relevant ("S/he used the. . ..") sentences. Non-apraxic participants looked at use-related non-target objects significantly more than at unrelated non-target objects when cued both by neutral and action-relevant sentences, indicating that action information is incidentally activated. In contrast, apraxic participants showed delayed activation of manipulation-based action information during object identification when cued by neutral sentences. The magnitude of delayed activation in the neutral sentence condition was reliably predicted by lower scores on a test of gesture production to viewed objects, as well as by lesion loci in the inferior parietal and posterior temporal lobes. However, when cued by a sentence containing an action verb, apraxic participants showed fixation patterns that were statistically indistinguishable from non-apraxic controls. In support of grounded theories of cognition, these results suggest that apraxia and temporal-parietal lesions may be associated with abnormalities in incidental activation of action information from objects. Further, they suggest that the previously-observed facilitative role of action verbs in the retrieval of object-related action information extends to participants with apraxia. |
Carly J. Leonard; Benjamin M. Robinson; Britta Hahn; James M. Gold; Steven J. Luck Enhanced distraction by magnocellular salience signals in schizophrenia Journal Article In: Neuropsychologia, vol. 56, no. 1, pp. 359–366, 2014. @article{Leonard2014, Research on schizophrenia has provided evidence of both impaired attentional control and dysfunctional magnocellular sensory processing. The present study tested the hypothesis that these impairments may be related, such that people with schizophrenia would be differentially distracted by stimuli that strongly activate the magnocellular pathway. To accomplish this, we used a visual attention paradigm from the basic cognitive neuroscience literature designed to assess the capture of attention by salient but irrelevant stimuli. Participants searched for a target shape in an array of non-target shapes. On some trials, a salient distractor was presented that either selectively activated the parvocellular system (parvo-biased distractors) or activated both the magnocellular and parvocellular systems (magno+parvo distractors). For both manual reaction times and eye movement measures, the magno+parvo distractors captured attention more strongly than the parvo-biased distractors in people with schizophrenia, but the opposite pattern was observed in matched healthy control participants. These results indicate that attentional control deficits in schizophrenia may arise, at least in part, by means of an interaction with magnocellular sensory dysfunction. |
Steven J. Luck; Clara McClenon; Valerie M. Beck; Andrew Hollingworth; Carly J. Leonard; Britta Hahn; Benjamin M. Robinson; James M. Gold Hyperfocusing in schizophrenia: Evidence from interactions between working memory and eye movements Journal Article In: Journal of Abnormal Psychology, vol. 123, no. 4, pp. 783–795, 2014. @article{Luck2014, Recent research suggests that processing resources are focused more narrowly but more intensely in people with schizophrenia (PSZ) than in healthy control subjects (HCS), possibly reflecting local cortical circuit abnormalities. This hyperfocusing hypothesis leads to the counterintuitive prediction that, although PSZ cannot store as much information in working memory as HCS, the working memory representations that are present in PSZ may be more intense than those in HCS. To test this hypothesis, we used a task in which participants make a saccadic eye movement to a peripheral target and avoid a parafoveal nontarget while they are holding a color in working memory. Previous research with this task has shown that the parafoveal nontarget is more distracting when it matches the color being held in working memory. This effect should be enhanced in PSZ if their working memory representations are more intense. Consistent with this prediction, we found that the effect of a match between the distractor color and the memory color was larger in PSZ than in HCS. We also observed evidence that PSZ hyperfocused spatially on the region surrounding the fixation point. These results provide further evidence that some aspects of cognitive dysfunction in schizophrenia may be a result of a narrower and more intense focusing of processing resources. |
Maria Matziridi; Mijke O. Hartendorp; Eli Brenner; Jeroen B. J. Smeets Does perisaccadic compression require foveal vision? Journal Article In: Perception, vol. 43, no. 11, pp. 1214–1224, 2014. @article{Matziridi2014, People make systematic errors when localizing a stimulus that is presented briefly near the time of a saccade. These errors have been interpreted as compression towards the position that is fixated after the saccade. Normally, fixating a position means that its image falls on the fovea. Macular degeneration (MD) damages the central retina, obliterating foveal vision. Many people with MD adopt a new retinal locus for fixation, called the preferred retinal locus (PRL). If the compression of space during the saccade is a special characteristic of the fovea, possibly due to the high density of cones that is found in the fovea, one might expect people lacking central vision to show no compression of space around the time of a saccade. If the compression of space during the saccade is related to the position that is fixated after the saccade, one would expect compression towards the PRL, despite the lack of a high density of cones in this area. We found that a person with MD showed a clear compression towards her PRL. We conclude that perisaccadic compression is related to the position that is fixated after the saccade rather than to the high density of receptors in the fovea. |
Xiao Gao; Xiao Deng; Jia Yang; Shuang Liang; Jie Liu; Hong Chen Eyes on the bodies: An eye tracking study on deployment of visual attention among females with body dissatisfaction Journal Article In: Eating Behaviors, vol. 15, no. 4, pp. 540–549, 2014. @article{Gao2014, Visual attentional bias has important functions during the appearance social comparisons. However, for the limitations of experimental paradigms or analysis methods in previous studies, the time course of attentional bias to thin and fat body images among women with body dissatisfaction (BD) has still been unclear. In using free reviewing task combined with eye movement tracking, and based on event-related analyses of the critical first eye movement events, as well as epoch-related analyses of gaze durations, the current study investigated different attentional bias components to body shape/part images during 15. s presentation time among 34 high BD and 34 non-BD young women. In comparison to the controls, women with BD showed sustained maintenance biases on thin and fat body images during both early automatic and late strategic processing stages. This study highlights a clear need for research on the dynamics of attentional biases related to body image and eating disturbances. |
Stephan Geuter; Matthias Gamer; Selim Onat; Christian Büchel Parametric trial-by-trial prediction of pain by easily available physiological measures Journal Article In: Pain, vol. 155, no. 5, pp. 994–1001, 2014. @article{Geuter2014, Pain is commonly assessed by subjective reports on rating scales. However, in many experimental and clinical settings, an additional, objective indicator of pain is desirable. In order to identify an objective, parametric signature of pain intensity that is predictive at the individual stimulus level across subjects, we recorded skin conductance and pupil diameter responses to heat pain stimuli of different durations and temperatures in 34 healthy subjects. The temporal profiles of trial-wise physiological responses were characterized by component scores obtained from principal component analysis. These component scores were then used as predictors in a linear regression analysis, resulting in accurate pain predictions for individual trials. Using the temporal information encoded in the principal component scores explained the data better than prediction by a single summary statistic (ie, maximum amplitude). These results indicate that perceived pain is best reflected by the temporal dynamics of autonomic responses. Application of the regression model to an independent data set of 20 subjects resulted in a very good prediction of the pain ratings demonstrating the generalizability of the identified temporal pattern. Utilizing the readily available temporal information from skin conductance and pupil diameter responses thus allows parametric prediction of pain in human subjects. |
Fatema F. Ghasia; Deepak Gulati; Edward L. Westbrook; Aasef G. Shaikh Viewing condition dependence of the gaze-evoked nystagmus in Arnold Chiari type 1 malformation Journal Article In: Journal of the Neurological Sciences, vol. 339, no. 1-2, pp. 134–139, 2014. @article{Ghasia2014, Saccadic eye movements rapidly shift gaze to the target of interest. Once the eyes reach a given target, the brainstem ocular motor integrator utilizes feedback from various sources to assure steady gaze. One of such sources is cerebellum whose lesion can impair neural integration leading to gaze-evoked nystagmus. The gaze evoked nystagmus is characterized by drifts moving the eyes away from the target and a null position where the drifts are absent. The extent of impairment in the neural integration for two opposite eccentricities might determine the location of the null position. Eye in the orbit position might also determine the location of the null. We report this phenomenon in a patient with Arnold Chiari type 1 malformation who had intermittent esotropia and horizontal gaze-evoked nystagmus with a shift in the null position. During binocular viewing, the null was shifted to the right. During monocular viewing, when the eye under cover drifted nasally (secondary to the esotropia), the null of the gaze-evoked nystagmus reorganized toward the center. We speculate that the output of the neural integrator is altered from the bilateral conflicting eye in the orbit position secondary to the strabismus. This could possibly explain the reorganization of the location of the null position. |
George T. Gitchel; Paul A. Wetzel; Abu Qutubuddin; Mark S. Baron Experimental support that ocular tremor in Parkinson's disease does not originate from head movement Journal Article In: Parkinsonism and Related Disorders, vol. 20, no. 7, pp. 743–747, 2014. @article{Gitchel2014, Introduction: Our recent report of ocular tremor in Parkinson's disease (PD) has raised considerable controversy as to the origin of the tremor. Using an infrared based eye tracker and a magnetic head tracker, we reported that ocular tremor was recordable in PD subjects with no apparent head tremor. However, other investigators suggest that the ocular tremor may represent either transmitted appendicular tremor or subclinical head tremor inducing the vestibulo-ocular reflex (VOR). The present study aimed to further investigate the origin of ocular tremor in PD. Methods: Eye movements were recorded in 8 PD subjects both head free, and with full head restraint by means of a head holding device and a dental impression bite plate. Head movements were recorded independently using both a high sensitivity tri-axial accelerometer and a magnetic tracking system, each synchronized to the eye tracker. Results: Ocular tremor was observed in all 8 PD subjects and was not influenced by head free and head fixed conditions. Both magnetic tracking and accelerometer recordings supported that the ocular tremor was fully independent of head position. Conclusion: The present study findings support our initial findings that ocular tremor is a fundamental feature of PD unrelated to head movements. Although the utility of ocular tremor for diagnostic purposes requires validation, current findings in large cohorts of PD subjects suggestits potential as a reliable clinical biomarker. |
Jennifer L. Greenberg; Lillian Reuman; Andrea S. Hartmann; Irina Kasarskis; Sabine Wilhelm Visual hot spots: An eye tracking study of attention bias in body dysmorphic disorder Journal Article In: Journal of Psychiatric Research, vol. 57, no. 1, pp. 125–132, 2014. @article{Greenberg2014, Attentional biases have been implicated in the development and maintenance of BDD. In particular, a visual attention bias toward one's unattractive features and others' attractive features (negative bias), might underlie BDD symptoms. Healthy individuals typically pay more attention to others' unattractive and their own attractive features (positive bias). This study used eye tracking to examine visual attention in individuals with BDD relative to healthy controls (HC). We also explored the role of avoidance in attention bias. Participants with BDD and primary face/head concerns ( n = 19) and HC ( n = 20) completed computerized tasks and questionnaires. Eye movement data (i.e., fixations, dwell time) were recorded while participants viewed images of their own and a control face (selected for average attractiveness and neutral expression). Participants rated distress and perceived most and least attractive features of their own and another face. BDD participants demonstrated a negative mean total bias score compared to HC (fixation: p = 0.24; dwell: p = 0.08). Age (fixation: p = 0.006; dwell: p = 0.03) and gender (fixation: p = 0.03; dwell: p = 0.03) moderated the relationship. Avoidance was associated with a positive bias in BDD. Results suggest individuals with BDD overfocus on negative attributes, a potential factor in the disorder's etiology and maintenance. Conversely, HC had a more balanced focus on their traits. Elucidating the role of attention bias could help to identify risk and maintenance factors in BDD. |
Simon J. Hickman; Naz Raoof; Rebecca J. McLean; Irene Gottlob Vision and multiple sclerosis Journal Article In: Multiple Sclerosis and Related Disorders, vol. 3, no. 1, pp. 3–16, 2014. @article{Hickman2014, Multiple sclerosis can affect vision in many ways, including optic neuritis, chronic optic neuropathy, retrochiasmal visual field defects, higher order cortical processing, double vision, nystagmus and also by related ocular conditions such as uveitis. There are also side effects from recently introduced multiple sclerosis treatments that can affect vision. This review will discuss all these aspects and how they come together to cause visual symptoms. It will then focus on practical aspects of how to recognise when there is a vision problem in a multiple sclerosis patient and on what treatments are available to improve vision. |
Shuo Wang; Juan Xu; Ming Jiang; Qi Zhao; Rene Hurlemann; Ralph Adolphs Autism spectrum disorder, but not amygdala lesions, impairs social attention in visual search Journal Article In: Neuropsychologia, vol. 63, pp. 259–274, 2014. @article{Wang2014f, People with autism spectrum disorders (ASD) have pervasive impairments in social interactions, a diagnostic component that may have its roots in atypical social motivation and attention. One of the brain structures implicated in the social abnormalities seen in ASD is the amygdala. To further characterize the impairment of people with ASD in social attention, and to explore the possible role of the amygdala, we employed a series of visual search tasks with both social (faces and people with different postures, emotions, ages, and genders) and non-social stimuli (e.g., electronics, food, and utensils). We first conducted trial-wise analyses of fixation properties and elucidated visual search mechanisms. We found that an attentional mechanism of initial orientation could explain the detection advantage of non-social targets. We then zoomed into fixation-wise analyses. We defined target-relevant effects as the difference in the percentage of fixations that fell on target-congruent vs. target-incongruent items in the array. In Experiment 1, we tested 8 high-functioning adults with ASD, 3 adults with focal bilateral amygdala lesions, and 19 controls. Controls rapidly oriented to target-congruent items and showed a strong and sustained preference for fixating them. Strikingly, people with ASD oriented significantly less and more slowly to target-congruent items, an attentional deficit especially with social targets. By contrast, patients with amygdala lesions performed indistinguishably from controls. In Experiment 2, we recruited a different sample of 13 people with ASD and 8 healthy controls, and tested them on the same search arrays but with all array items equalized for low-level saliency. The results replicated those of Experiment 1. In Experiment 3, we recruited 13 people with ASD, 8 healthy controls, 3 amygdala lesion patients and another group of 11 controls and tested them on a simpler array. Here our group effect for ASD strongly diminished and all four subject groups showed similar target-relevant effects. These findings argue for an attentional deficit in ASD that is disproportionate for social stimuli, cannot be explained by low-level visual properties of the stimuli, and is more severe with high-load top-down task demands. Furthermore, this deficit appears to be independent of the amygdala, and not evident from general social bias independent of the target-directed search. |
David E. Warren; Melissa C. Duff Not so fast: Hippocampal amnesia slows word learning despite successful fast mapping Journal Article In: Hippocampus, vol. 24, no. 8, pp. 920–933, 2014. @article{Warren2014, The human hippocampus is widely believed to be necessary for the rapid acquisition of new declarative relational memories. However, processes supporting on-line inferential word use ("fast mapping") may also exercise a dissociable learning mechanism and permit rapid word learning without the hippocampus (Sharon et al. (2011) Proc Natl Acad Sci USA 108:1146-1151). We investigated fast mapping in severely amnesic patients with hippocampal damage (N = 4), mildly amnesic patients (N = 6), and healthy comparison participants (N = 10) using on-line measures (eye movements) that reflected ongoing processing. All participants studied unique word-picture associations in two encoding conditions. In the explicit-encoding condition, uncommon items were paired with their names (e.g., "This is a numbat."). In the fast mapping study condition, participants heard an instruction using a novel word (e.g., "Click on the numbat.") while two items were presented (an uncommon target such as a numbat, and a common distracter such as a dog). All groups performed fast mapping well at study, and on-line eye movement measures did not reveal group differences. However, while comparison participants showed robust word learning irrespective of encoding condition, severely amnesic patients showed no evidence of learning after fast mapping or explicit encoding on any behavioral or eye-movement measure. Mildly amnesic patients showed some learning, but performance was unaffected by encoding condition. The findings are consistent with the following propositions: the hippocampus is not essential for on-line fast mapping of novel words; but is necessary for the rapid learning of arbitrary relational information irrespective of encoding conditions. |
Emily Wiecek; Kameran Lashkari; Steven C. Dakin; Peter J. Bex Novel quantitative assessment of metamorphopsia in maculopathy Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 1, pp. 494–504, 2014. @article{Wiecek2014, PURPOSE: Patients with macular disease often report experiencing metamorphopsia (visual distortion). Although typically measured with Amsler charts, more quantitative assessments of perceived distortion are desirable to effectively monitor the presence, progression, and remediation of visual impairment. METHODS: Participants with binocular (n = 33) and monocular (n = 50) maculopathy across seven disease groups, and control participants (n = 10) with no identifiable retinal disease completed a modified Amsler grid assessment (presented on a computer screen with eye tracking to ensure fixation compliance) and two novel assessments to measure metamorphopsia in the central 5° of visual field. A total of 81% (67/83) of participants completed a hyperacuity task where they aligned eight dots in the shape of a square, and 64% (32/50) of participants with monocular distortion completed a spatial alignment task using dichoptic stimuli. Ten controls completed all tasks. RESULTS: Horizontal and vertical distortion magnitudes were calculated for each of the three assessments. Distortion magnitudes were significantly higher in patients than controls in all assessments. There was no significant difference in magnitude of distortion across different macular diseases. There were no significant correlations between overall magnitude of distortion among any of the three measures and no significant correlations in localized measures of distortion. CONCLUSIONS: Three alternative quantifications of monocular spatial distortion in the central visual field generated uncorrelated estimates of visual distortion. It is therefore unlikely that metamorphopsia is caused solely by retinal displacement, but instead involves additional top-down information, knowledge about the scene, and perhaps, cortical reorganization. |
Keir X. X. Yong; Timothy J. Shakespeare; Dave Cash; Susie M. D. Henley; Jennifer M. Nicholas; Gerard R. Ridgway; Hannah L. Golden; Elizabeth K. Warrington; Amelia M. Carton; Diego Kaski; Jonathan M. Schott; Jason D. Warren; Sebastian J. Crutch Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population Journal Article In: Brain, vol. 137, no. 12, pp. 3284–3299, 2014. @article{Yong2014, Crowding is a breakdown in the ability to identify objects in clutter, and is a major constraint on object recognition. Crowding particularly impairs object perception in peripheral, amblyopic and possibly developing vision. Here we argue that crowding is also a critical factor limiting object perception in central vision of individuals with neurodegeneration of the occipital cortices. In the current study, individuals with posterior cortical atrophy (n=26), typical Alzheimer's disease (n=17) and healthy control subjects (n=14) completed centrally-presented tests of letter identification under six different flanking conditions (unflanked, and with letter, shape, number, same polarity and reverse polarity flankers) with two different target-flanker spacings (condensed, spaced). Patients with posterior cortical atrophy were significantly less accurate and slower to identify targets in the condensed than spaced condition even when the target letters were surrounded by flankers of a different category. Importantly, this spacing effect was observed for same, but not reverse, polarity flankers. The difference in accuracy between spaced and condensed stimuli was significantly associated with lower grey matter volume in the right collateral sulcus, in a region lying between the fusiform and lingual gyri. Detailed error analysis also revealed that similarity between the error response and the averaged target and flanker stimuli (but not individual target or flanker stimuli) was a significant predictor of error rate, more consistent with averaging than substitution accounts of crowding. Our findings suggest that crowding in posterior cortical atrophy can be regarded as a pre-attentive process that uses averaging to regularize the pathologically noisy representation of letter feature position in central vision. These results also help to clarify the cortical localization of feature integration components of crowding. More broadly, we suggest that posterior cortical atrophy provides a neurodegenerative disease model for exploring the basis of crowding. These data have significant implications for patients with, or who will go on to develop, dementia-related visual impairment, in whom acquired excessive crowding likely contributes to deficits in word, object, face and scene perception. |
Elena I. Ivleva; Amanda F. Moates; Jordan P. Hamm; Ira H. Bernstein; Hugh B. O'Neill; Darwynn Cole; Brett A. Clementz; Gunvant K. Thaker; Carol A. Tamminga In: Schizophrenia Bulletin, vol. 40, no. 3, pp. 642–652, 2014. @article{Ivleva2014, BACKGROUND: This study examined smooth pursuit eye movement (SPEM), prepulse inhibition (PPI), and auditory event-related potentials (ERP) to paired stimuli as putative endophenotypes of psychosis across the schizophrenia-bipolar disorder dimension. METHODS: Sixty-four schizophrenia probands (SZP), 40 psychotic bipolar I disorder probands (BDP), 31 relatives of SZP (SZR), 26 relatives of BDP (BDR), and 53 healthy controls (HC) were tested. Standard clinical characterization, SPEM, PPI, and ERP measures were administered. RESULTS: There were no differences between either SZP and BDP or SZR and BDR on any of the SPEM, PPI, or ERP measure. Compared with HC, SZP and BDP had lower SPEM maintenance and predictive pursuit gain and ERP theta/alpha and beta magnitudes to the initial stimulus. PPI did not differ between the psychosis probands and HC. Compared with HC, SZR and BDR had lower predictive pursuit gain and ERP theta/alpha and beta magnitudes to the first stimulus with differences ranging from a significant to a trend level. Neither active symptoms severity nor concomitant medications were associated with neurophysiological outcomes. SPEM, PPI, and ERP scores had low intercorrelations. CONCLUSION: These findings support SPEM predictive pursuit and lower frequency auditory ERP activity in a paired stimuli paradigm as putative endophenotypes of psychosis common to SZ and BD probands and relatives. PPI did not differ between the psychosis probands and HC. Future studies in larger scale psychosis family samples targeting putative psychosis endophenotypes and underlying molecular and genetic mediators may aid in the development of biology-based diagnostic definitions. |
Pavitra Jayaramachandran; Frank A. Proudlock; Nita Odedra; Irene Gottlob; Rebecca J. McLean A randomized controlled trial comparing soft contact lens and rigid gas-permeable lens wearing in infantile nystagmus Journal Article In: Ophthalmology, vol. 121, no. 9, pp. 1827–1836, 2014. @article{Jayaramachandran2014, Objective: To perform the first randomized controlled trial comparing soft contact lens (SCL) with rigid gas-permeable lens (RGPL) wearing in infantile nystagmus (IN), using spectacle wear as a baseline. Design: Randomized, controlled cross-over trial with an intention-to-treat design. Participants and Controls: A total of 24 participants with IN (12 idiopathic, 12 with albinism). Methods: Participants were randomized into 1 of 2 treatment arms receiving the following sequence of treatments (2-3 weeks for each treatment): (A) spectacles, SCL, RGPL, and spectacle wear; or (B) spectacles, RGPL, SCL, and spectacle wear. Main Outcome Measures: The main outcome measure was mean intensity of nystagmus at the null region viewing at 1.2 m. Secondary outcome measures included the same measure at 0.4 m viewing and across the horizontal meridian (measured over a ±30° range at 3° intervals) for distance and near. The nystagmus foveation characteristics were similarly assessed over ±30° and at the null region at 1.2 m and 0.4 m viewing. Visual outcome measures included best-corrected visual acuity (BCVA) at 4 m and 0.4 m, gaze-dependent visual acuity (GDVA) (i.e., visual acuity when maintaining gaze angles over a ±30° range at 10° intervals) at 4 m, and reading performance at 0.4 m derived from the Radner reading chart. Results: There were no significant differences between SCL and RGPL wearing for any nystagmus characteristics or compared with spectacle wearing. The BCVA, reading acuity, and critical print size were significantly worse for SCL wearing compared with RGPL and baseline spectacle wear (P<0.05), although mean differences were less than 1 logarithm of the minimum angle of resolution (logMAR) line. Conclusions: Nystagmus was not significantly different during SCL and RGPL wearing in IN, and contact lens wearing does not significantly reduce nystagmus compared with baseline spectacle wearing. The wearing of SCL leads to a small but statistically significant deterioration in visual function compared with both RGPL and spectacle wearing at baseline, although mean effect sizes were not clinically relevant. |
Sunjung Kim; Linda J. Lombardino; Wind Cowles; Lori J. Altmann Investigating graph comprehension in students with dyslexia: An eye tracking study Journal Article In: Research in Developmental Disabilities, vol. 35, no. 7, pp. 1609–1622, 2014. @article{Kim2014, The purpose of this study was to examine graph comprehension in college students with developmental dyslexia. We investigated how graph types (line, vertical bar, and horizontal bar graphs), graphic patterns (single and double graphic patterns), and question types (point locating and comparison questions) differentially affect graph comprehension of students with and without dyslexia. Groups were compared for (1) reaction times for answering comprehension questions based on graphed data and (2) eye gaze times for specific graph subregions (x-axis, y-axis, pattern, legend, question, and answer). Dyslexic readers were significantly slower in their graph comprehension than their peers with group differences becoming more robust with the increasing complexity of graphs and tasks. In addition, dyslexic readers' initial eye gaze viewing times for linguistic subregions (question and answer) and total viewing times for both linguistic (question and answer) and nonlinguistic (pattern) subregions were significantly longer than their control peers' times. In spite of using elementary-level paragraphs for comprehension and simple graph forms, young adults with dyslexia needed more time to process linguistic and nonlinguistic stimuli. These findings are discussed relative to theories proposed to address fundamental processing deficits in individuals with dyslexia. |
Paul Roux; Baudoin Forgeot d'Arc; Christine Passerieux; Franck Ramus Is the Theory of Mind deficit observed in visual paradigms in schizophrenia explained by an impaired attention toward gaze orientation? Journal Article In: Schizophrenia Research, vol. 157, no. 1-3, pp. 78–83, 2014. @article{Roux2014, Schizophrenia is associated with poor Theory of Mind (ToM), particularly in goal and belief attribution to others. It is also associated with abnormal gaze behaviors toward others: individuals with schizophrenia usually look less to others' face and gaze, which are crucial epistemic cues that contribute to correct mental states inferences. This study tests the hypothesis that impaired ToM in schizophrenia might be related to a deficit in visual attention toward gaze orientation.We adapted a previous non-verbal ToM paradigm consisting of animated cartoons allowing the assessment of goal and belief attribution. In the true and false belief conditions, an object was displaced while an agent was either looking at it or away, respectively. Eye movements were recorded to quantify visual attention to gaze orientation (proportion of time participants spent looking at the head of the agent while the target object changed locations).29 patients with schizophrenia and 29 matched controls were tested. Compared to controls, patients looked significantly less at the agent's head and had lower performance in belief and goal attribution. Performance in belief and goal attribution significantly increased with the head looking percentage. When the head looking percentage was entered as a covariate, the group effect on belief and goal attribution performance was not significant anymore.Patients' deficit on this visual ToM paradigm is thus entirely explained by a decreased visual attention toward gaze. |
D. Samuel Schwarzkopf; Elaine J. Anderson; Benjamin Haas; Sarah J. White; Geraint Rees Larger extrastriate population receptive fields in autism spectrum disorders Journal Article In: Journal of Neuroscience, vol. 34, no. 7, pp. 2713–2724, 2014. @article{Schwarzkopf2014, Previous behavioral research suggests enhanced local visual processing in individuals with autism spectrum disorders (ASDs). Here we used functional MRI and population receptive field (pRF) analysis to test whether the response selectivity of human visual cortex is atypical in individuals with high-functioning ASDs compared with neurotypical, demographically matched controls. For each voxel, we fitted a pRF model to fMRI signals measured while participants viewed flickering bar stimuli traversing the visual field. In most extrastriate regions, perifoveal pRFs were larger in the ASD group than in controls. We observed no differences in V1 or V3A. Differences in the hemodynamic response function, eye movements, or increased measurement noise could not account for these results; individuals with ASDs showed stronger, more reliable responses to visual stimulation. Interestingly, pRF sizes also correlated with individual differences in autistic traits but there were no correlations with behavioral measures of visual processing. Our findings thus suggest that visual cortex in ASDs is not characterized by sharper spatial selectivity. Instead, we speculate that visual cortical function in ASDs may be characterized by extrastriate cortical hyperexcitability or differential attentional deployment. |
Aasef G. Shaikh; Fatema F. Ghasia Gaze holding after anterior-inferior temporal lobectomy Journal Article In: Neurological Sciences, vol. 35, no. 11, pp. 1749–1756, 2014. @article{Shaikh2014, Eye position-sensitive neurons are found in parietooccipital and anterior-inferior temporal cortex. Putative role of these neurons is to facilitate transformation of reference frame from the retina-fixed to world-fixed coordinates and assure precise action. We assessed the nature of ocular motor disorder in a subject who had selective resection of the right anterior-inferior temporal cortex for the treatment of intractable epilepsy from cortical dysplasia. The gaze was stable when the subject was viewing straight-ahead, but centrally directed drifts in the eye position were seen during eccentric horizontal gaze holding. Eye-in-orbit position determined drift velocity and its direction. Conjugate and sinusoidal vertical oscillations were also present. Horizontal drifts and vertical oscillations became prominent and disconjugate in the absence of visual cue. The gaze-holding deficit was consistent with impairment in neural integration, but in the absence of cerebellar and visual deficits. We speculate that brainstem neural integrator might receive cortical feedback regarding world-fixed coordinates. Visual system might calibrate this process. Hence the lesion of the anterior-inferior temporal lobe leads to impairment in the function of neural integrator. Vision might be used to calibrate such feedback, hence the lack of visual cue further impairs the function of the neural integrator leading to worsening of gaze-holding deficits. |
Martha M. Shiell; François Champoux; Robert J. Zatorre Enhancement of visual motion detection thresholds in early deaf people Journal Article In: PLoS ONE, vol. 9, no. 2, pp. e90498, 2014. @article{Shiell2014, In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions. |
Nicholas D. Smith; Fiona C. Glen; Vera M. Mönter; David P. Crabb Using eye tracking to assess reading performance in patients with glaucoma: A within-person study Journal Article In: Journal of Ophthalmology, vol. 2014, pp. 1–10, 2014. @article{Smith2014, Reading is often cited as a demanding task for patients with glaucomatous visual field (VF) loss, yet reading speed varies widely between patients and does not appear to be predicted by standard visual function measures. This within-person study aimed to investigate reading duration and eye movements when reading short passages of text in a patient's worse eye (most VF damage) when compared to their better eye (least VF damage). Reading duration and saccade rate were significantly different on average in the worse eye when compared to the better eye (P < 0.001) in 14 patients with glaucoma that had median (interquartile range) between-eye difference in mean deviation (MD; a standard clinical measure for VF loss) of 9.8 (8.3 to 14.8) dB; differences were not related to the size of the difference in MD between eyes. Patients with a more pronounced effect of longer reading duration on their worse eye made a larger proportion of "regressions" (backward saccades) and "unknown" EMs (not adhering to expected reading patterns) when reading with the worse eye when compared to the better eye. A between-eye study in patients with asymmetric disease, coupled with eye tracking, provides a useful experimental design for exploring reading performance in glaucoma. |
Steven D. Stagg; Karina J. Linnell; Pamela Heaton Investigating eye movement patterns, language, and social ability in children with autism spectrum disorder Journal Article In: Development and Psychopathology, vol. 26, no. 2, pp. 529–537, 2014. @article{Stagg2014, Although all intellectually high-functioning children with autism spectrum disorder (ASD) display core social and communication deficits, some develop language within a normative timescale and others experience significant delays and subsequent language impairment. Early attention to social stimuli plays an important role in the emergence of language, and reduced attention to faces has been documented in infants later diagnosed with ASD. We investigated the extent to which patterns of attention to social stimuli would differentiate early and late language onset groups. Children with ASD (mean age = 10 years) differing on language onset timing (late/normal) and a typically developing comparison group completed a task in which visual attention to interacting and noninteracting human figures was mapped using eye tracking. Correlations on visual attention data and results from tests measuring current social and language ability were conducted. Patterns of visual attention did not distinguish typically developing children and ASD children with normal language onset. Children with ASD and late language onset showed significantly reduced attention to salient social stimuli. Associations between current language ability and social attention were observed. Delay in language onset is associated with current language skills as well as with specific eye-tracking patterns. |
Jianliang Tong; Jun Maruta; Kristin J. Heaton; Alexis L. Maule; Jamshid Ghajar Adaptation of visual tracking synchronization after one night of sleep deprivation Journal Article In: Experimental Brain Research, vol. 232, no. 1, pp. 121–131, 2014. @article{Tong2014, The temporal delay between sensory input and motor execution is a fundamental constraint in interactions with the environment. Predicting the temporal course of a stimulus and dynamically synchronizing the required action with the stimulus are critical for offsetting this constraint, and this prediction-synchronization capacity can be tested using visual tracking of a target with predictable motion. Although the role of temporal prediction in visual tracking is assumed, little is known of how internal predictions interact with the behavioral outcome or how changes in the cognitive state influence such interaction. We quantified and compared the predictive visual tracking performance of military volunteers before and after one night of sleep deprivation. The moment-to-moment synchronization of visual tracking during sleep deprivation deteriorated with sensitivity changes greater than 40 %. However, increased anticipatory saccades maintained the overall temporal accuracy with near zero phase error. Results suggest that acute sleep deprivation induces instability in visuomotor prediction, but there is compensatory visuomotor adaptation. Detection of these visual tracking features may aid in the identification of insufficient sleep. |
Hiroshi Ueda; Kohske Takahashi; Katsumi Watanabe Effects of direct and averted gaze on the subsequent saccadic response Journal Article In: Attention, Perception, and Psychophysics, vol. 76, no. 4, pp. 1085–1092, 2014. @article{Ueda2014a, The saccadic latency to visual targets is susceptible to the properties of the currently fixated objects. For example, the disappearance of a fixation stimulus prior to presentation of a peripheral target shortens saccadic latencies (the gap effect). In the present study, we investigated the influences of a social signal from a facial fixation stimulus (i.e., gaze direction) on subsequent saccadic responses in the gap paradigm. In Experiment 1, a cartoon face with a direct or averted gaze was used as a fixation stimulus. The pupils of the face were unchanged (overlap), disappeared (gap), or were translated vertically to make or break eye contact (gaze shift). Participants were required to make a saccade toward a target to the left or the right of the fixation stimulus as quickly as possible. The results showed that the gaze direction influenced saccadic latencies only in the gaze shift condition, but not in the gap or overlap condition; the direct-to-averted gaze shift (i.e., breaking eye contact) yielded shorter saccadic latencies than did the averted-to-direct gaze shift (i.e., making eye contact). Further experiments revealed that this effect was eye contact specific (Exp. 2) and that the appearance of an eye gaze immediately before the saccade initiation also influenced the saccadic latency, depending on the gaze direction (Exp. 3). These results suggest that the latency of target-elicited saccades can be modulated not only by physical changes of the fixation stimulus, as has been seen in the conventional gap effect, but also by a social signal from the attended fixation stimulus. |
Cyril Vienne; Laurent Sorin; Laurent Blondé; Quan Huynh-Thu; Pascal Mamassian Effect of the accommodation-vergence conflict on vergence eye movements Journal Article In: Vision Research, vol. 100, pp. 124–133, 2014. @article{Vienne2014, With the broader use of stereoscopic displays, a flurry of research activity about the accommodation- vergence conflict has emerged to highlight the implications for the human visual system. In stereoscopic displays, the introduction of binocular disparities requires the eyes to make vergence movements. In this study, we examined vergence dynamics with regard to the conflict between the stimulus-to- accommodation and the stimulus-to-vergence. In a first experiment, we evaluated the immediate effect of the conflict on vergence responses by presenting stimuli with conflicting disparity and focus on a stereoscopic display (i.e. increasing the stereoscopic demand) or by presenting stimuli with matched disparity and focus using an arrangement of displays and a beam splitter (i.e. focus and disparity specifying the same locations). We found that the dynamics of vergence responses were slower overall in the first case due to the conflict between accommodation and vergence. In a second experiment, we examined the effect of a prolonged exposure to the accommodation-vergence conflict on vergence responses, in which participants judged whether an oscillating depth pattern was in front or behind the fixation plane. An increase in peak velocity was observed, thereby suggesting that the vergence system has adapted to the stereoscopic demand. A slight increase in vergence latency was also observed, thus indicating a small decline of vergence performance. These findings offer a better understanding and document how the vergence system behaves in stereoscopic displays. We describe what stimuli in stereo-movies might produce these oculomotor effects, and discuss potential applications perspectives. |
Corinne R. Vokoun; Xin Huang; Meyer B. Jackson; Michele A. Basso Response normalization in the superficial layers of the superior colliculus as a possible mechanism for saccadic averaging Journal Article In: Journal of Neuroscience, vol. 34, no. 23, pp. 7976–7987, 2014. @article{Vokoun2014, How does the brain decide where to look? Neuronal networks within the superior colliculus (SC) encode locations of intended eye movements. When faced with multiple targets, the relative activities of neuronal populations compete for the selection of a saccade. However, the computational principles underlying saccadic choices remain poorly understood. We used voltage imaging of slices of rat SC to record circuit dynamics of population responses to single- and dual-site electrical stimulation to begin to reveal some of the principles of how populations of neurons interact. Stimulation of two distant sites simultaneously within the SC produced two distinct peaks of activity, whereas stimulation of two nearby sites simultaneously exhibited a single, merged peak centered between the two sites. The distances required to produce merged peaks of activity corresponded to target separations that evoked averaging saccades in humans performing a corresponding dual target task. The merged activity was well accounted for by a linear weighed summation and a divisive normalization of the responses evoked by the single-site stimulations. Interestingly, the merging of activity occurred within the superficial SC, suggesting a novel pathway for saccadic eye movement choice. |
Simone Vossel; Christoph Mathys; Jean Daunizeau; Markus Bauer; Jon Driver; Karl J. Friston; Klaas E. Stephan Spatial attention, precision, and bayesian inference: A study of saccadic response speed Journal Article In: Cerebral Cortex, vol. 24, no. 6, pp. 1436–1450, 2014. @article{Vossel2014a, Inferring the environment's statistical structure and adapting behavior accordingly is a fundamental modus operandi of the brain. A simple form of this faculty based on spatial attentional orienting can be studied with Posner's location-cueing paradigm in which a cue indicates the target location with a known probability. The present study focuses on a more complex version of this task, where probabilistic context (percentage of cue validity) changes unpredictably over time, thereby creating a volatile environment. Saccadic response speed (RS) was recorded in 15 subjects and used to estimate subject-specific parameters of a Bayesian learning scheme modeling the subjects' trial-by-trial updates of beliefs. Different response models-specifying how computational states translate into observable behavior-were compared using Bayesian model selection. Saccadic RS was most plausibly explained as a function of the precision of the belief about the causes of sensory input. This finding is in accordance with current Bayesian theories of brain function, and specifically with the proposal that spatial attention is mediated by a precision-dependent gain modulation of sensory input. Our results provide empirical support for precision-dependent changes in beliefs about saccade target locations and motivate future neuroimaging and neuropharmacological studies of how Bayesian inference may determine spatial attention. |
Benchi Wang; Matthew D. Hilchey; Xiaohua Cao; Zhiguo Wang The spatial distribution of inhibition of return revisited: No difference found between manual and saccadic responses Journal Article In: Neuroscience Letters, vol. 578, pp. 128–132, 2014. @article{Wang2014a, Inhibition of return (IOR) commonly refers to the effect of prolonged response times to targets at previously attended locations. It is a well-documented fact that IOR is not restricted to previously attended locations, but rather has a spatial gradient. Based on a myriad of manual/saccadic dissociations, many researchers now believe that there are at least two forms of IOR completely dissociable on the basis of response type. The present study evaluated whether these two forms of IOR are encoded in similar representations of space. Across a range of conditions, there was little indication that the two forms could be differentiated on the basis of their spatial distributions. Furthermore, the present study also found that the gradient of IOR was steepest for cues appearing nearest fixation. |
C. -A. Wang; S. E. Boehnke; Laurent Itti; D. P. Munoz Transient pupil response is modulated by contrast-based saliency Journal Article In: Journal of Neuroscience, vol. 34, no. 2, pp. 408–417, 2014. @article{Wang2014b, The sudden appearance of a novel stimulus in the environment initiates a series of orienting responses that include coordinated shifts of gaze and attention, and also transient changes in pupil size. Although numerous studies have identified a significant effect of stimulus saliency on shifts of gaze and attention, saliency effects on pupil size are less understood. To examine salience-evoked pupil responses, we presented visual, auditory, or audiovisual stimuli while monkeys fixated a central visual spot. Transient pupil dilation was elicited after visual stimulus presentation regardless of target luminance relative to background, and auditory stimuli also evoked similar pupil responses. Importantly, the evoked pupil response was modulated by contrast-based saliency, with faster and larger pupil responses following the presentation of more salient stimuli. The initial transient component of pupil dilation was qualitatively similar to that evoked by weak microstimulation of the midbrain superior colliculus. The pupil responses elicited by audiovisual stimuli were well predicted by a linear summation of each modality response. Together, the results suggest that the transient pupil response, as one component of orienting, is modulated by contrast-based saliency, and the superior colliculus is likely involved in its coordination. |
Mark Wexler; Thérèse Collins Orthogonal steps relieve saccadic suppression Journal Article In: Journal of vision, vol. 14, no. 2, pp. 1–9, 2014. @article{Wexler2014, Although the retinal position of objects changes with each saccadic eye movement, we perceive the visual world to be stable. How this visual stability or constancy arises is debated. Cancellation accounts propose that the retinal consequences of eye movements are compensated for by an equal-but-opposite eye movement signal. Assumption accounts propose that saccade-induced retinal displacements are ignored because we have a prior belief in a stable world. Saccadic suppression of displacement-the fact that small displacements of the visual targets during saccades go unnoticed-argues in favor of assumption accounts. Extinguishing the target before the displacement unmasks it, arguing in favor of cancellation accounts. We show that an irrelevant displacement of the target orthogonal to saccade direction unmasks displacements parallel to saccade direction, and therefore relieves saccadic suppression of displacement. This result suggests that visual stability arises from the interplay between cancellation and assumption mechanisms: When the post-saccadic target position falls within an elliptic region roughly equivalent to habitual saccadic variability, displacements are not seen and stability is assumed. When the displacements fall outside this region, as with our orthogonal steps, displacements are seen and positions are remapped. |
Andreas Widmann; Ralf Engbert; Erich Schroger Microsaccadic responses indicate fast categorization of sounds: A novel approach to study auditory cognition Journal Article In: Journal of Neuroscience, vol. 34, no. 33, pp. 11152–11158, 2014. @article{Widmann2014, The mental chronometry of the human brain's processing of sounds to be categorized as targets has intensively been studied in cognitive neuroscience. According to current theories, a series of successive stages consisting of the registration, identification, and categorization of the sound has to be completed before participants are able to report the sound as a target by button press after ∼300-500 ms. Here we use miniature eye movements as a tool to study the categorization of a sound as a target or nontarget, indicating that an initial categorization is present already after 80-100 ms. During visual fixation, the rate of microsaccades, the fastest components of miniature eye movements, is transiently modulated after auditory stimulation. In two experiments, we measured microsaccade rates in human participants in an auditory three-tone oddball paradigm (including rare nontarget sounds) and observed a difference in the microsaccade rates between targets and nontargets as early as 142 ms after sound onset. This finding was replicated in a third experiment with directed saccades measured in a paradigm in which tones had to be matched to score-like visual symbols. Considering the delays introduced by (motor) signal transmission and data analysis constraints, the brain must have differentiated target from nontarget sounds as fast as 80-100 ms after sound onset in both paradigms. We suggest that predictive information processing for expected input makes higher cognitive attributes, such as a sound's identity and category, available already during early sensory processing. The measurement of eye movements is thus a promising approach to investigate hearing. |
Irene Ablinger; Kerstin Heyden; Christian Vorstius; Katja Halm; Walter Huber; Ralph Radach An eye movement based reading intervention in lexical and segmental readers with acquired dyslexia Journal Article In: Neuropsychological Rehabilitation, vol. 24, no. 6, pp. 833–867, 2014. @article{Ablinger2014a, Due to their brain damage, aphasic patients with acquired dyslexia often rely to a greater extent on lexical or segmental reading procedures. Thus, therapy intervention is mostly targeted on the more impaired reading strategy. In the present work we introduce a novel therapy approach based on real-time measurement of patients' eye movements as they attempt to read words. More specifically, an eye movement contingent technique of stepwise letter de-masking was used to support sequential reading, whereas fixation-dependent initial masking of non-central letters stimulated a lexical (parallel) reading strategy. Four lexical and four segmental readers with acquired central dyslexia received our intensive reading intervention. All participants showed remarkable improvements as evident in reduced total reading time, a reduced number of fixations per word and improved reading accuracy. Both types of intervention led to item-specific training effects in all subjects. A generalisation to untrained items was only found in segmental readers after the lexical training. Eye movement analyses were also used to compare word processing before and after therapy, indicating that all patients, with one exclusion, maintained their preferred reading strategy. However, in several cases the balance between sequential and lexical processing became less extreme, indicating a more effective individual interplay of both word processing routes. |
Noor Z. Al Dahhan; George K. Georgiou; Rickie Hung; Douglas P. Munoz; Rauno Parrila; John R. Kirby Eye movements of university students with and without reading difficulties during naming speed tasks Journal Article In: Annals of Dyslexia, vol. 64, no. 2, pp. 137–150, 2014. @article{AlDahhan2014, Although naming speed (NS) has been shown to predict reading into adulthood and differentiate between adult dyslexics and controls, the question remains why NS is related to reading. To address this question, eye movement methodology was combined with three letter NS tasks (the original letter NS task by Denckla & Rudel, Cortex 10:186-202, 1974, and two more developed by Compton, The Journal of Special Education 37:81-94, 2003, with increased phonological or visual similarity of the letters). Twenty undergraduate students with reading difficulties (RD) and 27 without (NRD) were tested on letter NS tasks (eye movements were recorded during the NS tasks), phonological processing, and reading fluency. The results indicated first that the RD group was slower than the NRD group on all NS tasks with no differences between the NS tasks. In addition, the NRD group had shorter fixation durations, longer saccades, and fewer saccades and fixations than the RD group. Fixation duration and fixation count were significant predictors of reading fluency even after controlling for phonological processing measures. Taken together, these findings suggest that the NS-reading relationship is due to two factors: less able readers require more time to acquire stimulus information during fixation and they make more saccades. |
Sheena K. Au-Yeung; Johanna K. Kaakinen; Valerie Benson Cognitive perspective-taking during scene perception in autism spectrum disorder: Evidence from eye movements Journal Article In: Autism Research, vol. 7, no. 1, pp. 84–93, 2014. @article{AuYeung2014, The present study examined how eye movements during scene viewing are modulated by adopting psychological perspectives in both adults with autism spectrum disorders (ASD) and typically developing adults. In the current study, participants viewed house scenes with either non-perspective-taking (look for valuable items/features of the house that need fixing) or perspective-taking instructions (imagine that you are a burglar/repairman) while their eye movements were recorded. The eye movement measures revealed that for the “look for the valuable items” and burglar perspective task, the ASD group showed typical relevance effects (the preference to look at schema-relevant compared with schema-irrelevant targets) in their eye movements. However, we found subtle processing differences between the groups that were related to initial orienting to and processing of schema-relevant items for the “look for the features that need fixing” and the repairman perspective-taking task. There was an absence of a relevance effect for the ASD group for the repairman perspective and its non-perspective-taking equivalent instruction showing that the identification of items relevant to those schemas was more difficult for the ASD group. The present findings suggest that resolving ambiguity may be a defining feature of complex information processing deficits in ASD. |
Elizabeth H. Beck; Anthony A. Amato; Steven A. Greenberg; Elizabeth H. Beck Improvement of internuclear ophthalmoparesis in multiple sclerosis with dalfampridine Journal Article In: Neurology, vol. 83, pp. 192–194, 2014. @article{Beck2014, Internuclear ophthalmoparesis (INO) in multiple sclerosis (MS) is due to demyelination of the medial longitudinal fasciculus (MLF) and provides an acces- sible model for studying consequences of raised body temperature and fatigue on central demyelination.1,2 Prompted by one of our patient's report of vision improvement after initiating dalfampridine, a potas- sium channel blocker prescribed for gait impairment,3 we measured this drug's effects on 3 patients with MS with bilateral INO. All showed changes in horizontal saccadic conjugacy consistent with improved trans- mission of the neural pulse responsible for adducting movements. |
Natalie Bruin; Devon C. Bryant; Claudia L. R. Gonzalez "Left neglected," but only in far space: Spatial biases in healthy participants revealed in a visually guided grasping task Journal Article In: Frontiers in Neurology, vol. 5, pp. 4, 2014. @article{Bruin2014, Hemispatial neglect is a common outcome of stroke that is characterized by the inability to orient toward, and attend to stimuli in contralesional space. It is established that hemispatial neglect has a perceptual component, however, the presence and severity of motor impairments is controversial. Establishing the nature of space use and spatial biases during visually guided actions amongst healthy individuals is critical to understanding the presence of visuomotor deficits in patients with neglect. Accordingly, three experiments were conducted to investigate the effect of object spatial location on patterns of grasping. Experiment 1 required right-handed participants to reach and grasp for blocks in order to construct 3D models. The blocks were scattered on a tabletop divided into equal size quadrants: left near, left far, right near, and right far. Identical sets of building blocks were available in each quadrant. Space use was dynamic, with participants initially grasping blocks from right near space and tending to "neglect" left far space until the final stages of the task. Experiment 2 repeated the protocol with left-handed participants. Remarkably, left-handed participants displayed a similar pattern of space use to right-handed participants. In Experiment 3 eye movements were examined to investigate whether "neglect" for grasping in left far reachable space had its origins in attentional biases. It was found that patterns of eye movements mirrored patterns of reach-to-grasp movements. We conclude that there are spatial biases during visually guided grasping, specifically, a tendency to neglect left far reachable space, and that this "neglect" is attentional in origin. The results raise the possibility that visuomotor impairments reported among patients with right hemisphere lesions when working in contralesional space may result in part from this inherent tendency to "neglect" left far space irrespective of the presence of unilateral visuospatial neglect. |
Louis F. Dell'Osso; Faruk H. Orge; Jonathan B. Jacobs; Zhong I. Wang; Louis F. Dell'Osso; Faruk H. Orge; Jonathan B. Jacobs; Zhong I. Wang Fusion maldevelopment (latent/manifest latent) nystagmus syndrome: Effects of four-muscle tenotomy and reattachment Journal Article In: Journal of Pediatric Ophthalmology & Strabismus, vol. 51, no. 3, pp. 180–188, 2014. @article{DellOsso2014, PURPOSE: To examine the waveform and clinical effects of the four-muscle tenotomy and reattachment procedure in fusion maldevelopment nystagmus syndrome (FMNS) and to compare them to those documented in infantile nystagmus syndrome (INS) and acquired nystagmus. METHODS: Both infrared reflection and high-speed digital video systems were used to record the eye movements in a patient with FMNS (before and after tenotomy and reattachment). Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software. Model simulations and predictions were performed using the authors' behavioral ocular motor system model in MATLAB Simulink (The MathWorks, Inc., Natick, MA). RESULTS: The model predicted, and the patient's data confirmed, that the tenotomy and reattachment procedure produces improvements in FMN waveforms across a broader field of gaze and decreases the Alexander's law variation. The patient's tenotomy and reattachment plots of NAFX after surgery versus gaze angle were higher and had lower slope than before surgery. Clinically, despite moderate improvements in both peak measured acuity and stereoacuity, dramatic improvements in the patient's abilities and lifestyle resulted. CONCLUSIONS: The four-muscle tenotomy and reattachment nystagmus surgery produced beneficial therapeutic effects on FMN waveforms that are similar to those demonstrated in INS and acquired nystagmus. These results support the authors' prior recommendation that tenotomy and reattachment nystagmus should be added to required strabismus procedures in patients who also have FMNS (ie, perform tenotomy and reattachment on all unoperated muscles in the plane of the nystagmus). Furthermore, when strabismus surgery is not required, four-muscle tenotomy and reattachment may be used to improve FMN waveforms and visual function. |
Matt J. Dunn; Tom H. Margrain; J. Margaret Woodhouse; Fergal A. Ennis; Christopher M. Harris; Jonathan T. Erichsen Grating visual acuity in infantile nystagmus in the absence of image motion Journal Article In: Investigative Ophthalmology & Visual Science, vol. 55, no. 4, pp. 2682–2686, 2014. @article{Dunn2014, PURPOSE: Infantile nystagmus (IN) consists of largely horizontal oscillations of the eyes that usually begin shortly after birth. The condition is almost always associated with lower-than-normal visual acuity (VA). This is assumed to be at least partially due to motion blur induced by the eye movements. Here, we investigated the effect of image motion on VA. METHODS: Grating stimuli were presented, illuminated by either multiple tachistoscopic flashes (0.76 ms) to circumvent retinal image motion, or under constant illumination, to subjects with horizontal idiopathic IN and controls. A staircase procedure was used to estimate VA (by judging direction of tilt) under each condition. Orientation-specific effects were investigated by testing gratings oriented about both the horizontal and vertical axes. RESULTS: Nystagmats had poorer VA than controls under both constant and tachistoscopic illumination. Neither group showed a significant difference in VA between illumination conditions. Nystagmats performed worse for vertically oriented gratings, even under tachistoscopic conditions (P < 0.01), but there was no significant effect of orientation in controls. CONCLUSIONS: The fact that VA was not significantly affected by either illumination condition strongly suggests that the eye movements themselves do not significantly degrade VA in adults with IN. Treatments and therapies that seek to modify and/or reduce eye movements may therefore be fundamentally limited in any improvement that can be achieved with respect to VA. |
Ricki-Leigh Elliot; Linda E. Campbell; Mick Hunter; Gavin Cooper; Jessica L. Melville; Kathryn L. McCabe; Louise Newman; Carmel M. Loughland When I look into my baby's eyes... infant emotion recognition by mothers with Borderline Personality Disorder Journal Article In: Infant Mental Health Journal, vol. 35, pp. 21–32, 2014. @article{Elliot2014, Mothers with borderline personality disorder (BPD) have disturbed relationships with their infants, possibly associated with poor nonverbal cue perception. Individuals with BPD are poor at recognizing emotion in adults and tend to misattribute neutral (i.e., no emotion) as sad. This study extends previous research by examining how mothers with BPD perceive known (own) and unknown (control) infant stimuli depicting happy, sad, and neutral emotions. The sample consisted of 13 women diagnosed with BPD and 13 healthy control mothers. All participants completed clinical and parenting questionnaires and an infant emotion recognition task. Compared to control mothers, mothers with BPD were significantly poorer at infant emotion recognition overall, but especially neutral expressions which were misattributed most often as sad. Performance was not related to disturbed parenting but rather mothers' age and illness duration. Neither the BPD nor control mothers showed enhanced accuracy for emotional displays of their own verses unknown infant-face images. Although the sample size was small, this study provides evidence that mothers with BPD negatively misinterpret neutral images, which may impact sensitive responding to infant emotional cues. These findings have implications for clinical practiceand the development of remediation programs targeting emotion-perception disturbances in mothers with BPD. |
Jonas Everaert; Wouter Duyck; Ernst H. W. Koster Attention, interpretation, and memory biases in subclinical depression: A proof-of-principle test of the combined cognitive biases hypothesis Journal Article In: Emotion, vol. 14, no. 2, pp. 331–340, 2014. @article{Everaert2014, Emotional biases in attention, interpretation, and memory are viewed as important cognitive processes underlying symptoms of depression. To date, there is a limited understanding of the interplay among these processing biases. This study tested the dependence of memory on depression-related biases in attention and interpretation. Subclinically depressed and non- depressed participants completed a computerized version of the scrambled sentences test (measuring interpretation bias) while their eye movements were recorded (measuring attention bias). This task was followed by an incidental free recall test of previously constructed interpretations (measuring memory bias). Path analysis revealed a good fit for the model in which selective orienting of attention was associated with interpretation bias, which in turn was associated with a congruent bias in memory. Also, a good fit was observed for a path model in which biases in the maintenance of attention and interpretation were associated with memory bias. Both path models attained a superior fit compared to path models without the theorized functional relations among processing biases. These findings enhance understanding of how mechanisms of attention and interpretation regulate what is remembered. As such, they offer support for the combined cognitive biases hypothesis or the notion that emotionally biased cognitive processes are not isolated mechanisms but instead influence each other. Implications for theoretical models and emotion regulation across the spectrum of depressive symptoms are discussed. |
Gerardo Fernández; Jochen Laubrock; Pablo Mandolesi; Oscar Colombo; Osvaldo Agamennoni Registering eye movements during reading in Alzheimers disease: Difficulties in predicting upcoming words Journal Article In: Journal of Clinical and Experimental Neuropsychology, vol. 36, no. 3, pp. 302–316, 2014. @article{Fernandez2014, Reading requires the fine integration of attention, ocular movements, word identification, and language comprehension, among other cognitive parameters. Several of the associated cognitive processes such as working memory and semantic memory are known to be impaired by Alzheimer's disease (AD). This study analyzes eye movement behavior of 18 patients with probable AD and 40 age-matched controls during Spanish sentence reading. Controls focused mainly on word properties and considered syntactic and semantic structures. At the same time, controls' knowledge and prediction about sentence meaning and grammatical structure are quite evident when we consider some aspects of visual exploration, such as word skipping, and forward saccades. By contrast, in the AD group, the predictability effect of the upcoming word was absent, visual exploration was less focused, fixations were much longer, and outgoing saccade amplitudes were smaller than those in controls. The altered visual exploration and the absence of a contextual predictability effect might be related to impairments in working memory and long-term memory retrieval functions. These eye movement measures demonstrate considerable sensitivity with respect to evaluating cognitive processes in Alzheimer's disease. They could provide a user-friendly marker of early disease symptoms and of its posterior progression. |
Gerardo Fernández; Facundo Manes; Nora P. Rotstein; Oscar Colombo; Pablo Mandolesi; Luis E. Politi; Osvaldo Agamennoni Lack of contextual-word predictability during reading in patients with mild Alzheimer disease Journal Article In: Neuropsychologia, vol. 62, no. 1, pp. 143–151, 2014. @article{Fernandez2014a, In the present work we analyzed the effect of contextual word predictability on the eye movement behavior of patients with mild Alzheimer disease (AD) compared to age-matched controls, by using the eyetracking technique and lineal mixed models. Twenty AD patients and 40 age-matched controls participated in the study. We first evaluated gaze duration during reading low and highly predictable sentences. AD patients showed an increase in gaze duration, compared to controls, both in sentences of low or high predictability. In controls, highly predictable sentences led to shorter gaze durations; by contrary, AD patients showed similar gaze durations in both types of sentences. Similarly, gaze duration in controls was affected by the cloze predictability of word N and N+1, whereas it was the same in AD patients. In contrast, the effects of word frequency and word length were similar in controls and AD patients. Our results imply that contextual-word predictability, whose processing is proposed to require memory retrieval, facilitated reading behavior in healthy subjects, but this facilitation was lost in early AD patients. This loss might reveal impairments in brain areas such as those corresponding to working memory, memory retrieval, and semantic memory functions that are already present at early stages of AD. In contrast, word frequency and length processing might require less complex mechanisms, which were still retained by AD patients. To the best of our knowledge, this is the first study measuring how patients with early AD process well-defined words embedded in sentences of high and low predictability. Evaluation of the resulting changes in eye movement behavior might provide a useful tool for a more precise early diagnosis of AD. |
Tyler R. Peel; Kevin D. Johnston; Stephen G. Lomber; Brian D. Corneil Bilateral saccadic deficits following large and reversible inactivation of unilateral frontal eye field Journal Article In: Journal of Neurophysiology, vol. 111, no. 2, pp. 415–433, 2014. @article{Peel2014, Inactivation permits direct assessment of the functional contribution of a given brain area to behavior. Previous inactivation studies of the frontal eye field (FEF) have either used large permanent ablations or reversible pharmacological techniques that only inactivate a small volume of tissue. Here we evaluated the impact of large, yet reversible, FEF inactivation on visually guided, delayed, and memory-guided saccades, using cryoloops implanted in the arcuate sulcus. While FEF inactivation produced the expected triad of contralateral saccadic deficits (increased reaction time, decreased accuracy and peak velocity) and performance errors (neglect or misdirected saccades), we also found consistent increases in reaction times of ipsiversive saccades in all three tasks. In addition, FEF inactivation did not increase the proportion of premature saccades to ipsilateral targets, as was predicted on the basis of pharmacological studies. Consistent with previous studies, greater deficits accompanied saccades toward extinguished visual cues. Our results attest to the functional contribution of the FEF to saccades in both directions. We speculate that the comparative effects of different inactivation techniques relate to the volume of inactivated tissue within the FEF. Larger inactivation volumes may reveal the functional contribution of more sparsely distributed neurons within the FEF, such as those related to ipsiversive saccades. Furthermore, while focal FEF inactivation may disinhibit the mirroring site in the other FEF, larger inactivation volumes may induce broad disinhibition in the other FEF that paradoxically prolongs oculomotor processing via increased competitive interactions. |
Nicholas S. C. Price; J. Blum Motion perception correlates with volitional but not reflexive eye movements Journal Article In: Neuroscience, vol. 277, pp. 435–445, 2014. @article{Price2014, Visually-driven actions and perception are traditionally ascribed to the dorsal and ventral visual streams of the cortical processing hierarchy. However, motion perception and the control of tracking eye movements both depend on sensory motion analysis by neurons in the dorsal stream, suggesting that the same sensory circuits may underlie both action and perception. Previous studies have suggested that multiple sensory modules may be responsible for the perception of low- and high-level motion, or the detection versus identification of motion direction. However, it remains unclear whether the sensory processing systems that contribute to direction perception and the control of eye movements have the same neuronal constraints. To address this, we examined inter-individual variability across 36 observers, using two tasks that simultaneously assessed the precision of eye movements and direction perception: in the smooth pursuit task, observers volitionally tracked a small moving target and reported its direction; in the ocular following task, observers reflexively tracked a large moving stimulus and reported its direction. We determined perceptual-oculomotor correlations across observers, defined as the correlation between each observer's mean perceptual precision and mean oculomotor precision. Across observers, we found that: (i) mean perceptual precision was correlated between the two tasks; (ii) mean oculomotor precision was correlated between the tasks, and (iii) oculomotor and perceptual precision were correlated for volitional smooth pursuit, but not reflexive ocular following. Collectively, these results demonstrate that sensory circuits with common neuronal constraints subserve motion perception and volitional, but not reflexive eye movements. |
Claudio M. Privitera; Thom Carney; Stanley A. Klein; Mario Aguilar Analysis of microsaccades and pupil dilation reveals a common decisional origin during visual search Journal Article In: Vision Research, vol. 95, pp. 43–50, 2014. @article{Privitera2014, During free viewing visual search, observers often refixate the same locations several times before and after target detection is reported with a button press. We analyzed the rate of microsaccades in the sequence of refixations made during visual search and found two important components. One related to the visual content of the region being fixated; fixations on targets generate more microsaccades and more microsaccades are generated for those targets that are more difficult to disambiguate. The other empathizes non-visual decisional processes; fixations containing the button press generate more microsaccades than those made on the same target but without the button press. Pupil dilation during the same refixations reveals a similar modulation. We inferred that generic sympathetic arousal mechanisms are part of the articulated complex of perceptual processes governing fixational eye movements. |
Michaël Sassi; Maarten Demeyer; Johan Wagemans Peripheral contour grouping and saccade targeting: The role of mirror symmetry Journal Article In: Symmetry, vol. 6, no. 1, pp. 1–22, 2014. @article{Sassi2014, Integrating shape contours in the visual periphery is vital to our ability to locate objects and thus make targeted saccadic eye movements to efficiently explore our surroundings. We tested whether global shape symmetry facilitates peripheral contour integration and saccade targeting in three experiments, in which observers responded to a successful peripheral contour detection by making a saccade towards the target shape. The target contours were horizontally (Experiment 1) or vertically (Experiments 2 and 3) mirror symmetric. Observers responded by making a horizontal (Experiments 1 and 2) or vertical (Experiment 3) eye movement. Based on an analysis of the saccadic latency and accuracy, we conclude that the figure-ground cue of global mirror symmetry in the periphery has little effect on contour integration or on the speed and precision with which saccades are targeted towards objects. The role of mirror symmetry may be more apparent under natural viewing conditions with multiple objects competing for attention, where symmetric regions in the visual field can pre-attentively signal the presence of objects, and thus attract eye movements. |
Sebastian Schneegans; John P. Spencer; Gregor Schoner; Seongmin Hwang; Andrew Hollingworth Dynamic interactions between visual working memory and saccade target selection Journal Article In: Journal of Vision, vol. 14, no. 11, pp. 1–23, 2014. @article{Schneegans2014, Recent psychophysical experiments have shown that working memory for visual surface features interacts with saccadic motor planning, even in tasks where the saccade target is unambiguously specified by spatial cues. Specifically, a match between a memorized color and the color of either the designated target or a distractor stimulus influences saccade target selection, saccade amplitudes, and latencies in a systematic fashion. To elucidate these effects, we present a dynamic neural field model in combination with new experimental data. The model captures the neural processes underlying visual perception, working memory, and saccade planning relevant to the psychophysical experiment. It consists of a low-level visual sensory representation that interacts with two separate pathways: a spatial pathway implementing spatial attention and saccade generation, and a surface feature pathway implementing color working memory and feature attention. Due to bidirectional coupling between visual working memory and feature attention in the model, the working memory content can indirectly exert an effect on perceptual processing in the low-level sensory representation. This in turn biases saccadic movement planning in the spatial pathway, allowing the model to quantitatively reproduce the observed interaction effects. The continuous coupling between representations in the model also implies that modulation should be bidirectional, and model simulations provide specific predictions for complementary effects of saccade target selection on visual working memory. These predictions were empirically confirmed in a new experiment: Memory for a sample color was biased toward the color of a task- irrelevant saccade target object, demonstrating the bidirectional coupling between visual working memory and perceptual processing. |
Alexander C. Schütz; Dirk Kerzel; David Souto Saccadic adaptation induced by a perceptual task Journal Article In: Journal of Vision, vol. 14, no. 5, pp. 1–19, 2014. @article{Schuetz2014a, The human motor system and muscles are subject to fluctuations in the short and long term. Motor adaptation is classically thought of as a low-level process that compensates for the error between predicted and executed movements in order to maintain movement accuracy. Contrary to a low-level account, accurate movements might be only a means to support high-level behavioral and perceptual goals. To isolate the influence of high-level goals in adaptation of saccadic eye movements, we manipulated perceptual task requirements in the absence of low-level errors. Observers had to discriminate one character within a peripheral array of characters. Between trials, the location of this character within the array was changed. This manipulation led to an immediate strategic change and a slower, gradual adaptation of saccade amplitude and direction. These changes had a similar magnitude to classical saccade adaptation and transferred at least partially to reactive saccades without a perceptual task. These results suggest that a perceptual task can modify oculomotor commands by generating a top-down error signal in saccade maps just like a bottom-up visual position error. Hence saccade adaptation not only maintains saccadic targeting accuracy, but also optimizes gaze behavior for the behavioral goal, showing that perception shapes even low-level oculomotor mechanisms. |
Mehrdad Seirafi; Peter De Weerd; Beatrice De Gelder Suppression of face perception during saccadic eye movements Journal Article In: Journal of Ophthalmology, vol. 2014, pp. 1–7, 2014. @article{Seirafi2014, Lack of awareness of a stimulus briefly presented during saccadic eye movement is known as saccadic omission. Studying the reduced visibility of visual stimuli around the time of saccade-known as saccadic suppression-is a key step to investigate saccadic omission. To date, almost all studies have been focused on the reduced visibility of simple stimuli such as flashes and bars. The extension of the results from simple stimuli to more complex objects has been neglected. In two experimental tasks, we measured the subjective and objective awareness of a briefly presented face stimuli during saccadic eye movement. In the first task, we measured the subjective awareness of the visual stimuli and showed that in most of the trials there is no conscious awareness of the faces. In the second task, we measured objective sensitivity in a two-alternative forced choice (2AFC) face detection task, which demonstrated chance-level performance. Here, we provide the first evidence of complete suppression of complex visual stimuli during the saccadic eye movement. |
Eva Siegenthaler; Francisco M. Costela; Michael B. Mccamy; Leandro Luigi Di Stasi; Jorge Otero-Millan; Andreas Sonderegger; Rudolf Groner; Stephen L. Macknik; Susana Martinez-Conde Task difficulty in mental arithmetic affects microsaccadic rates and magnitudes Journal Article In: European Journal of Neuroscience, vol. 39, no. 2, pp. 287–294, 2014. @article{Siegenthaler2014, Microsaccades are involuntary, small-magnitude saccadic eye movements that occur during attempted visual fixation. Recent research has found that attention can modulate microsaccade dynamics, but few studies have addressed the effects of task difficulty on microsaccade parameters, and those have obtained contradictory results. Further, no study to date has investigated the influence of task difficulty on microsaccade production during the performance of non-visual tasks. Thus, the effects of task difficulty on microsaccades, isolated from sensory modality, remain unclear. Here we investigated the effects of task difficulty on microsaccades during the performance of a non-visual, mental arithmetic task with two levels of complexity. We found that microsaccade rates decreased and microsaccade magnitudes increased with increased task difficulty. We propose that changes in microsaccade rates and magnitudes with task difficulty are mediated by the effects of varying attentional inputs on the rostral superior colliculus activity map. |
Jeroen D. Silvis; Mieke Donk The effects of saccade-contingent changes on oculomotor capture: Salience is important even beyond the first oculomotor response Journal Article In: Attention, Perception, and Psychophysics, vol. 76, no. 6, pp. 1803–1814, 2014. @article{Silvis2014a, Whenever a novel scene is presented, visual salience merely plays a transient role in oculomotor selection. Unique stimulus properties, such as a distinct and, thereby, salient color, affect the oculomotor response only when observers react relatively quickly. For slower responses, or for consecutive ones, salience-driven effects appear completely absent. To date, however, the circumstances that may reinstate the effects of salience over multiple eye movements are still unclear. Recent research shows that changes to a scene can attract gaze, even when these changes occur without a transient signal (i.e., during an eye movement). The aim of the present study was to investigate whether this capture is mediated through salience-driven or memory-guided processes. In three experiments, we examined how the nature of a change in salience that occurred during an eye movement affected consecutive saccades. The results demonstrate that the oculomotor system is exclusively susceptible to increases in salience from one fixation to the next, but only when these increases result in a uniquely high salience level. This suggests that even in the case of a saccade-contingent change, oculomotor selection behavior can be affected by salience-driven mechanisms, possibly to allow the automatic detection of uniquely distinct objects at any moment. The results and implications will be discussed in relation to current views on visual selection. |
Sarit F. A. Szpiro; Miriam Spering; Marisa Carrasco Perceptual learning modifies untrained pursuit eye movements Journal Article In: Journal of Vision, vol. 14, no. 8, pp. 1–13, 2014. @article{Szpiro2014, Perceptual learning improves detection and discrimination of relevant visual information in mature humans, revealing sensory plasticity. Whether visual perceptual learning affects motor responses is unknown. Here we implemented a protocol that enabled us to address this question. We tested a perceptual response (motion direction estimation, in which observers overestimate motion direction away from a reference) and a motor response (voluntary smooth pursuit eye movements). Perceptual training led to greater overestimation and, remarkably, it modified untrained smooth pursuit. In contrast, pursuit training did not affect overestimation in either pursuit or perception, even though observers in both training groups were exposed to the same stimuli for the same time period. A second experiment revealed that estimation training also improved discrimination, indicating that overestimation may optimize perceptual sensitivity. Hence, active perceptual training is necessary to alter perceptual responses, and an acquired change in perception suffices to modify pursuit, a motor response. |
Krzysztof Templin; Piotr Didyk; Karol Myszkowski; Mohamed M Hefeeda; Hans-Peter Seidel; Wojciech Matusik Modeling and optimizing eye vergence response to stereoscopic cuts Journal Article In: ACM Transactions on Graphics, vol. 33, no. 4, pp. 1–8, 2014. @article{Templin2014, Sudden temporal depth changes, such as cuts that are introduced by video edits, can significantly degrade the quality of stereoscopic content. Since usually not encountered in the real world, they are very challenging for the audience. This is because the eye vergence has to constantly adapt to new disparities in spite of conflicting accommodation requirements. Such rapid disparity changes may lead to confusion, reduced understanding of the scene, and overall attractiveness of the content. In most cases the problem cannot be solved by simply matching the depth around the transition, as this would require flattening the scene completely. To better understand this limitation of the human visual system, we conducted a series of eye-tracking experiments. The data obtained allowed us to derive and evaluate a model describing adaptation of vergence to disparity changes on a stereoscopic display. Besides computing user-specific models, we also estimated parameters of an average observer model. This enables a range of strategies for minimizing the adaptation time in the audience. |
Antonia F. Ten Brink; Tanja C. W. Nijboer; Nathan Van der Stoep; Stefan Van der Stigchel The influence of vertically and horizontally aligned visual distractors on aurally guided saccadic eye movements Journal Article In: Experimental Brain Research, vol. 232, no. 4, pp. 1357–1366, 2014. @article{TenBrink2014, Eye movements towards a new target can be guided or disrupted by input from multiple modalities. The degree of oculomotor competition evoked by a distractor depends on both distractor and target properties, such as distractor salience or certainty regarding the target location. The ability to localize the target is particularly important when studying saccades made towards auditory targets, since determination of elevation and azimuth of a sound are based on different processes, and these processes may be affected independently by a distractor. We investigated the effects of a visual distractor on saccadic eye movements made to an auditory target in a two-dimensional plane. Results showed that the competition evoked by a vertical visual distractor was stronger compared with a horizontal visual distractor. The eye movements that were not captured by the vertical visual distractor were still influenced by it: a deviation of endpoints was seen in the direction of the visual distractor. Furthermore, the interference evoked by a high-contrast visual distractor was stronger compared with low-contrast visual stimuli, which was reflected by a faster initiation of an eye movement towards the high-contrast visual distractor and a stronger shift of endpoints in the direction of the high-contrast visual distractor. Together, these findings show that the influence of a visual distractor on aurally guided eye movements depends strongly on its location relative to the target, and to a lesser extent, on stimulus contrast. |
Richard A. I. Bethlehem; Serge O. Dumoulin; Edwin S. Dalmaijer; Miranda Smit; Tos T. J. M. Berendschot; Tanja C. W. Nijboer; Stefan Van Der Stigchel Decreased fixation stability of the preferred retinal location in juvenile macular degeneration Journal Article In: PLoS ONE, vol. 9, no. 6, pp. e100171, 2014. @article{Bethlehem2014, Macular degeneration is the main cause for diminished visual acuity in the elderly. The juvenile form of macular degeneration has equally detrimental consequences on foveal vision. To compensate for loss of foveal vision most patients with macular degeneration adopt an eccentric preferred retinal location that takes over tasks normally performed by the healthy fovea. It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision. Here, we investigated whether the fixation characteristics of the preferred retinal locus resemble those of the healthy fovea. For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker. The fixation-offset paradigm measures release from fixation under different fixation conditions and has been shown useful to distinguish between foveal and non-foveal fixation. We measured eye-movements in nine healthy age-matched controls and five patients with juvenile macular degeneration. In addition, we performed a simulation with the same task in a group of five healthy controls. Our results show that the preferred retinal locus does not adopt a foveal type of fixation but instead drifts further away from its original fixation and has overall increased fixation instability. Furthermore, the fixation instability is most pronounced in low frequency eye-movements representing a slow drift from fixation. We argue that the increased fixation instability cannot be attributed to fixation under an unnatural angle. Instead, diminished visual acuity in the periphery causes reduced oculomotor control and results in increased fixation instability. |
Matthew W. Bridgman; Warren S. Brown; Michael L. Spezio; Matthew K. Leonard; Ralph Adolphs; Lynn K. Paul Facial emotion recognition in agenesis of the corpus callosum Journal Article In: Journal of Neurodevelopmental Disorders, vol. 6, pp. 1–14, 2014. @article{Bridgman2014, BACKGROUND: Impaired social functioning is a common symptom of individuals with developmental disruptions in callosal connectivity. Among these developmental conditions, agenesis of the corpus callosum provides the most extreme and clearly identifiable example of callosal disconnection. To date, deficits in nonliteral language comprehension, humor, theory of mind, and social reasoning have been documented in agenesis of the corpus callosum. Here, we examined a basic social ability as yet not investigated in this population: recognition of facial emotion and its association with social gaze. METHODS: Nine individuals with callosal agenesis and nine matched controls completed four tasks involving emotional faces: emotion recognition from upright and inverted faces, gender recognition, and passive viewing. Eye-tracking data were collected concurrently on all four tasks and analyzed according to designated facial regions of interest. RESULTS: Individuals with callosal agenesis exhibited impairments in recognizing emotions from upright faces, in particular lower accuracy for fear and anger, and these impairments were directly associated with diminished attention to the eye region. The callosal agenesis group exhibited greater consistency in emotion recognition across conditions (upright vs. inverted), with poorest performance for fear identification in both conditions. The callosal agenesis group also had atypical facial scanning (lower fractional dwell time in the eye region) during gender naming and passive viewing of faces, but they did not differ from controls on gender naming performance. The pattern of results did not differ when taking into account full-scale intelligence quotient or presence of autism spectrum symptoms. CONCLUSIONS: Agenesis of the corpus callosum results in a pattern of atypical facial scanning characterized by diminished attention to the eyes. This pattern suggests that reduced callosal connectivity may contribute to the development and maintenance of emotion processing deficits involving reduced attention to others' eyes. |
Florian Brugger; Michael Schüpbach; Michel Koenig; René M. Müri; Stephan Bohlhalter; Alain Kaelin-Lang; Christian P. Kamm; Georg Kägi The clinical spectrum of ataxia with oculomotor apraxia type 2 Journal Article In: Movement Disorders Clinical Practice, vol. 1, no. 2, pp. 106–109, 2014. @article{Brugger2014, Ataxia with oculomotor apraxia type 2 (AOA2) is an inherited disorder caused by mutations within both alleles of the senataxin gene. First symptoms are usually recognized before the age of 30. Unlike several other autosomal recessive cerebellar ataxia syndromes, levels of alpha-fetoprotein are nearly always elevated in AOA2 and thus narrowing down the differential diagnosis list. We present 3 video cases illustrating and expanding the clinical spectrum of AOA2, with 1 case bearing a novel mutation with cervical dystonia as the first symptom, the absence of neuropathy, and a disease onset beyond the age of 40. Furthermore, all patients were assessed by oculographic analysis, which revealed distinct patterns of oculomotor abnormalities. The clinical spectrum of AOA2 might be even broader than previously described in larger series. Oculography might be a useful tool to detect subclinical oculomotor apraxia in this disorder. |
Robyn Burton; Nicholas D. Smith; David P. Crabb Eye movements and reading in glaucoma: observations on patients with advanced visual field loss Journal Article In: Graefe's Archive for Clinical and Experimental Ophthalmology, vol. 252, no. 10, pp. 1621–1630, 2014. @article{Burton2014, PURPOSE: To investigate the relationship between reading speed and eye movements in patients with advanced glaucomatous visual field (VF) defects and age-similar visually healthy people.$backslash$n$backslash$nMETHODS: Eighteen patients with advanced bilateral VF defects (mean age: 71, standard deviation [SD]: 7 years) and 39 controls (mean age: 67, SD: 8 years) had reading speed measured using short passages of text on a computer set-up incorporating eye tracking. Scanpaths were plotted and analysed from these experiments to derive measures of 'perceptual span' (total number of letters read per number of saccades) and 'text saturation' (the distance between the first and last fixation on lines of text). Another eye movement measure, termed 'saccadic frequency' (total number of saccades made to read a single word), was derived from a separate lexical decision task, where words were presented in isolation.$backslash$n$backslash$nRESULTS: Significant linear association was demonstrated between perceptual span and reading speed in patients (R (2) = 0.42) and controls (R (2) = 0.56). Linear association between saccadic frequency during the LDT and reading speed was also found in patients (R (2) = 0.42), but not in controls (R (2) = 0.02). Patients also exhibited greater average text saturation than controls (P = 0.004).$backslash$n$backslash$nCONCLUSION: Some, but not all, patients with advanced VF defects read slower than controls using short text passages. Differences in eye movement behaviour may partly account for this variability in patients. These patients were shown to saturate lines of text more during reading, which may explain previously-reported difficulties with sustained reading. |
Thomas Busigny; Goedele Van Belle; Boutheina Jemel; Anthony Hosein; Sven Joubert; Bruno Rossion Face-specific impairment in holistic perception following focal lesion of the right anterior temporal lobe Journal Article In: Neuropsychologia, vol. 56, no. 1, pp. 312–333, 2014. @article{Busigny2014, Recent studies have provided solid evidence for pure cases of prosopagnosia following brain damage. The patients reported so far have posterior lesions encompassing either or both the right inferior occipital cortex and fusiform gyrus, and exhibit a critical impairment in generating a sufficiently detailed holistic percept to individualize faces. Here, we extended these observations to include the prosopagnosic patient LR (Bukach, Bub, Gauthier, & Tarr, 2006), whose damage is restricted to the anterior region of the right temporal lobe. First, we report that LR is able to discriminate parametrically defined individual exemplars of nonface object categories as accurately and quickly as typical observers, which suggests that the visual similarity account of prosopagnosia does not explain his impairments. Then, we show that LR does not present with the typical face inversion effect, whole-part advantage, or composite face effect and, therefore, has impaired holistic perception of individual faces. Moreover, the patient is more impaired at matching faces when the facial part he fixates is masked than when it is selectively revealed by means of gaze contingency. Altogether these observations support the view that the nature of the critical face impairment does not differ qualitatively across patients with acquired prosopagnosia, regardless of the localization of brain damage: all these patients appear to be impaired to some extent at what constitutes the heart of our visual expertise with faces, namely holistic perception at a sufficiently fine-grained level of resolution to discriminate exemplars of the face class efficiently. This conclusion raises issues regarding the existing criteria for diagnosis/classification of patients as cases of apperceptive or associative prosopagnosia. |
Aurélie Calabrèse; Jean-Baptiste Bernard; Géraldine Faure; Louis Hoffart; Eric Castet Eye movements and reading speed in macular disease: The shrinking perceptual span hypothesis requires and is supported by a mediation analysis Journal Article In: Investigative Ophthalmology & Visual Science, vol. 55, no. 6, pp. 3638–3645, 2014. @article{Calabrese2014, Purpose. Reading speed of patients with Central Field Loss (CFL) correlates with the size of saccades (measured in letters per forward saccade - L/FS). We assessed whether this effect is mediated by the total number of fixations, by the average fixation duration, or by a mixture of both. Methods. We measured eye movements (with a video eyetracker) of 35 AMD and 4 Stargardt patients (better eye decimal acuity from 0.08 to 0.3) while they monocularly read single-line French sentences continuously displayed on a screen. All patients had a dense scotoma covering the fovea, as assessed with MP1 microperimetry, and therefore used eccentric viewing. Results were analyzed with regression-based mediation analysis, a modeling framework that informs on the underlying factors by which an independent variable affects a dependent variable. Results. Reading speed and average fixation duration are negatively correlated, a result that was not observed in prior studies with CFL patients. This effect of fixation duration on reading speed is still significant when partialling out the effect of the total number of fixations (slope:-0.75, p<0.001). Despite this large effect of fixation duration, mediation analysis shows that the effect of L/FS on reading speed is fully mediated by the total number of fixations (effect size: 0.96; CI[0.82, 1.12]) and not by fixation duration (effect size: 0.02; CI[-0.11,0.14]). Conclusions. Results are consistent with the shrinking perceptual span hypothesis: reading speed decreases with the average number of letters traversed on each forward saccade, an effect fully mediated by the total number of fixations. |
Michael Coesmans; Christian H. Röder; Albertine E. Smit; Sebastiaan K. E. Koekkoek; Chris I. De Zeeuw; Maarten A. Frens; Josef N. Geest Cerebellar motor learning deficits in medicated and medication-free men with recent-onset schizophrenia Journal Article In: Journal of Psychiatry and Neuroscience, vol. 39, no. 1, pp. 3–11, 2014. @article{Coesmans2014, BACKGROUND: The notion that cerebellar deficits may underlie clinical symptoms in people with schizophrenia is tested by evaluating 2 forms of cerebellar learning in patients with recent-onset schizophrenia. A potential medication effect is evaluated by including patients with or without antipsychotics. METHODS: We assessed saccadic eye movement adaptation and eyeblink conditioning in men with recent-onset schizophrenia who were taking antipsychotic medication or who were antipsychotic-free and in age-matched controls. RESULTS: We included 39 men with schizophrenia (10 who were taking clozapine, 16 who were taking haloperidol and 13 who were antipsychotic-free) and 29 controls in our study. All participants showed significant saccadic adaptation. Adaptation strength did not differ between healthy controls and men with schizophrenia. The speed of saccade adaptation, however, was significantly lower in men with schizophrenia. They showed a significantly lower increase in the number of conditioned eyeblink responses. Over all experiments, no consistent effects of medication were observed. These outcomes did not correlate with age, years of education, psychopathology or dose of antipsychotics. LIMITATIONS: As patients were not randomized for treatment, an influence of confounding variables associated with medication status cannot be excluded. Individual patients also varied along the schizophrenia spectrum despite the relative homogeneity with respect to onset of illness and short usage of medication. Finally, the relatively small number of participants may have concealed effects as a result of insufficient statistical power. CONCLUSION: We found several cerebellar learning deficits in men with schizophrenia that we cannot attribute to the use of antipsychotics. Although this finding, combined with the fact that deficits are already present in patients with recent-onset schizophrenia, could suggest that cerebellar impairments are a trait deficit in people with schizophrenia. This should be confirmed in longitudinal studies. |
Benjamin A. Wolfe; David Whitney Facilitating recognition of crowded faces with presaccadic attention Journal Article In: Frontiers in Human Neuroscience, vol. 8, pp. 103, 2014. @article{Wolfe2014, In daily life, we make several saccades per second to objects we cannot normally recognize in the periphery due to visual crowding. While we are aware of the presence of these objects, we cannot identify them and may, at best, only know that an object is present at a particular location. The process of planning a saccade involves a presaccadic attentional component known to be critical for saccadic accuracy, but whether this or other presaccadic processes facilitate object identification as opposed to object detection-especially with high level natural objects like faces-is less clear. In the following experiments, we show that presaccadic information about a crowded face reduces the deleterious effect of crowding, facilitating discrimination of two emotional faces, even when the target face is never foveated. While accurate identification of crowded objects is possible in the absence of a saccade, accurate identification of a crowded object is considerably facilitated by presaccadic attention. Our results provide converging evidence for a selective increase in available information about high level objects, such as faces, at a presaccadic stage. |
Yoshiko Yabe; Melvyn A. Goodale; Hiroaki Shigemasu Temporal order judgments are disrupted more by reflexive than by voluntary saccades Journal Article In: Journal of Neurophysiology, vol. 111, no. 10, pp. 2103–2108, 2014. @article{Yabe2014, We do not always perceive the sequence of events as they actually unfold. For example, when two events occur before a rapid eye movement (saccade), the interval between them is often perceived as shorter than it really is and the order of those events can be sometimes reversed (Morrone MC, Ross J, Burr DC. Nat Neurosci 8: 950-954, 2005). In the present article we show that these misperceptions of the temporal order of events critically depend on whether the saccade is reflexive or voluntary. In the first experiment, participants judged the temporal order of two visual stimuli that were presented one after the other just before a reflexive or voluntary saccadic eye movement. In the reflexive saccade condition, participants moved their eyes to a target that suddenly appeared. In the voluntary saccade condition, participants moved their eyes to a target that was present already. Similarly to the above-cited study, we found that the temporal order of events was often misjudged just before a reflexive saccade to a suddenly appearing target. However, when people made a voluntary saccade to a target that was already present, there was a significant reduction in the probability of misjudging the temporal order of the same events. In the second experiment, the reduction was seen in a memory-delay task. It is likely that the nature of the motor command and its origin determine how time is perceived during the moments preceding the motor act. |
Shlomit Yuval-Greenberg; Elisha P. Merriam; David J. Heeger Spontaneous microsaccades reflect shifts in covert attention Journal Article In: Journal of Neuroscience, vol. 34, no. 41, pp. 13693–13700, 2014. @article{YuvalGreenberg2014, Microsaccade rate during fixation is modulated by the presentation of a visual stimulus. When the stimulus is an endogenous attention cue, the ensuing microsaccades tend to be directed toward the cue. This finding has been taken as evidence that microsaccades index the locus of spatial attention. But the vast majority of microsaccades that subjects make are not triggered by visual stimuli. Under natural viewing conditions, spontaneous microsaccades occur frequently (2-3 Hz), even in the absence of a stimulus or a task. While spontaneous microsaccades may depend on low-level visual demands, such as retinal fatigue, image fading, or fixation shifts, it is unknown whether their occurrence corresponds to changes in the attentional state. We developed a protocol to measure whether spontaneous microsaccades reflect shifts in spatial attention. Human subjects fixated a cross while microsaccades were detected from streaming eye-position data. Detection of a microsaccade triggered the appearance of a peripheral ring of grating patches, which were followed by an arrow (a postcue) indicating one of them as the target. The target was either congruent or incongruent (opposite) with respect to the direction of the microsaccade (which preceded the stimulus). Subjects reported the tilt of the target (clockwise or counterclockwise relative to vertical). We found that accuracy was higher for congruent than for incongruent trials. We conclude that the direction of spontaneous microsaccades is inherently linked to shifts in spatial attention. |
Eckart Zimmermann; S. Born; Gereon R. Fink; P. Cavanagh Masking produces compression of space and time in the absence of eye movements Journal Article In: Journal of Neurophysiology, vol. 112, no. 12, pp. 3066–3076, 2014. @article{Zimmermann2014a, Whenever the visual stream is abruptly disturbed by eye movements, blinks, masks, or flashes of light, the visual system needs to retrieve the new locations of current targets and to reconstruct the timing of events to straddle the interruption. This process may introduce position and timing errors. We here report that very similar errors are seen in human subjects across three different paradigms when disturbances are caused by either eye movements, as is well known, or, as we now show, masking. We suggest that the characteristic effects of eye movements on position and time, spatial and temporal compression and saccadic suppression of displacement, are consequences of the interruption and the subsequent reconnection and are seen also when visual input is masked without any eye movements. Our data show that compression and suppression effects are not solely a product of ocular motor activity but instead can be properties of a correspondence process that links the targets of interest across interruptions in visual input, no matter what their source. |
Eckart Zimmermann; M. Concetta Morrone; David C. Burr The visual component to saccadic compression Journal Article In: Journal of Vision, vol. 14, no. 12, pp. 13–, 2014. @article{Zimmermann2014, Visual objects presented around the time of saccadic eye movements are strongly mislocalized towards the saccadic target, a phenomenon known as "saccadic compression." Here we show that perisaccadic compression is modulated by the presence of a visual saccadic target. When subjects saccaded to the center of the screen with no visible target, perisaccadic localization was more veridical than when tested with a target. Presenting a saccadic target sometime before saccade initiation was sufficient to induce mislocalization. When we systematically varied the onset of the saccade target, we found that it had to be presented around 100 ms before saccade execution to cause strong mislocalization: saccadic targets presented after this time caused progressively less mislocalization. When subjects made a saccade to screen center with a reference object placed at various positions, mislocalization was focused towards the position of the reference object. The results suggest that saccadic compression is a signature of a mechanism attempting to match objects seen before the saccade with those seen after. |
Sébastien Miellet; Roberto Caldara; Christopher Gillberg; Monika Raju; Helen Minnis Disinhibited reactive attachment disorder symptoms impair social judgements from faces Journal Article In: Psychiatry Research, vol. 215, no. 3, pp. 747–752, 2014. @article{Miellet2014, Typically developing adults and children can rapidly reach consensus regarding the trustworthiness of unfamiliar faces. Maltreated children can have problems with trusting others, yet those with the disinhibited form of reactive attachment disorder (dRAD) can be indiscriminately friendly. Whether children with dRAD symptoms appraise and conform to typical judgements about trustworthiness of faces is still unknown. We recorded eye movements of 10 maltreated dRAD children and 10 age and gender matched typically developing control children while they made social judgements from faces. Children were presented with a series of pairs of faces previously judged by adults to have high or low attractiveness or trustworthiness ratings. Typically developing children reached a consensus regarding which faces were the most trustworthy and attractive. There was less agreement among the children with dRAD symptoms. Judgments from the typically developing children showed a strong correlation between the attractiveness and trustworthiness tasks. This was not the case for the dRAD group, who showed less agreement and no significant correlation between trustworthiness and attractiveness judgments. Finally, both groups of children sampled the eye region to perform social judgments. Our data offer a unique insight in children with dRAD symptoms, providing novel and important knowledge for their rehabilitation. |
M. Miller; L. Chukoskie; M. Zinni; Jeanne Townsend; D. Trauner Dyspraxia, motor function and visual–motor integration in autism Journal Article In: Behavioural Brain Research, vol. 269, no. 4, pp. 95–102, 2014. @article{Miller2014, This project assessed dyspraxia in high-functioning school aged children with autism with a focus on Ideational Praxis. We examined the association of specific underlying motor function including eye movement with ideational dyspraxia (sequences of skilled movements) as well as the possible role of visual-motor integration in dyspraxia. We found that compared to IQ-, sex- and age-matched typically developing children, the children with autism performed significantly worse on: Ideational and Buccofacial praxis; a broad range of motor tests, including measures of simple motor skill, timing and accuracy of saccadic eye movements and motor coordination; and tests of visual-motor integration. Impairments in individual children with autism were heterogeneous in nature, although when we examined the praxis data as a function of a qualitative measure representing motor timing, we found that children with poor motor timing performed worse on all praxis categories and had slower and less accurate eye movements while those with regular timing performed as well as typical children on those same tasks. Our data provide evidence that both motor function and visual-motor integration contribute to dyspraxia. We suggest that dyspraxia in autism involves cerebellar mechanisms of movement control and the integration of these mechanisms with cortical networks implicated in praxis. |
Kenichiro Miura; Ryota Hashimoto; Michiko Fujimoto; Hidenaga Yamamori; Yuka Yasuda; Kazutaka Ohi; Satomi Umeda-Yano; Masaki Fukunaga; Masao Iwase; Masatoshi Takeda An integrated eye movement score as a neurophysiological marker of schizophrenia Journal Article In: Schizophrenia Research, vol. 160, no. 1-3, pp. 228–229, 2014. @article{Miura2014, In this study, we aimed to create an integrated eye movement rating scale that indicates the degree to which the eye movements are abnormal, and examined the relationship between the eye movement score and conventional scales of symptom severity and social and cognitive functioning in patients with schizophrenia. The eye movements of 40 patients with schizophrenia and 69 healthy subjects aged 15 to 68 years old were recorded. All subjects were biologically unrelated and were of Japanese descent. The integrated eye movement score represents the dimensions of schizophrenia that are, in large part, different from the dimensions represented by the conventional scales. Therefore, the score will effectively assist physicians' diagnosis together with conventional symptom/functioning scales, and, in particular, may be useful in the early diagnosis of schizophrenia or its prodrome where subjective symptoms are relatively obscure. The significance of eye movement scores primarily lies in diagnosis of schizophrenia, although this score is not to replace DSM-V diagnostic criteria or any other criteria that rely on history, observation and self-report. A similar methodology using eye movement characteristics may be usable to distinguish schizophrenia from bipolar mania, schizoaffective disorder and autism and so on, and future studies should test this possibility. |
Zhenlan Jin; Scott N. J. Watamaniuk; Aarlenne Zein Khan; Elena Potapchuk; Stephen J. Heinen Motion integration for ocular pursuit does not hinder perceptual segregation of moving objects Journal Article In: Journal of Neuroscience, vol. 34, no. 17, pp. 5835–5841, 2014. @article{Jin2014, When confronted with a complex moving stimulus, the brain can integrate local element velocities to obtain a single motion signal, or segregate the elements to maintain awareness of their identities. The integrated motion signal can drive smooth-pursuit eye movements (Heinen and Watamaniuk, 1998), whereas the segregated signal guides attentive tracking of individual elements in multiple-object tracking tasks (MOT; Pylyshyn and Storm, 1988). It is evident that these processes can occur simultaneously, because we can effortlessly pursue ambulating creatures while inspecting disjoint moving features, such as arms and legs, but the underlying mechanism is unknown. Here, we provide evidence that separate neural circuits perform the mathematically opposed operations of integration and segregation, by demonstrating with a dual-task paradigm that the two processes do not share attentional resources. Human observers attentively tracked a subset of target elements composing a small MOT stimulus, while pursuing it ocularly as it translated across a computer display. Integration of the multidot stimulus yielded optimal pursuit. Importantly, performing MOT while pursuing the stimulus did not degrade performance on either task compared with when each was performed alone, indicating that they did not share attention. A control experiment showed that pursuit was not driven by integration of only the nontargets, leaving the MOT targets free for segregation. Nor was a predictive strategy used to pursue the stimulus, because sudden changes in its global velocity were accurately followed. The results suggest that separate neural mechanisms can simultaneously segregate and integrate the same motion signals. |
Stephanie A. H. Jones; Christopher D. Cowper-Smith; David A. Westwood Directional interactions between current and prior saccades Journal Article In: Frontiers in Human Neuroscience, vol. 8, pp. 872, 2014. @article{Jones2014, One way to explore how prior sensory and motor events impact eye movements is to ask someone to look to targets located about a central point, returning gaze to the central point after each eye movement. Concerned about the contribution of this return to center movement, Anderson et al. (2008) used a sequential saccade paradigm in which participants made a continuous series of saccades to peripheral targets that appeared to the left or right of the currently fixated location in a random sequence (the next eye movement began from the last target location). Examining the effects of previous saccades (n-x) on current saccade latency (n), they found that saccadic reaction times (RT) were reduced when the direction of the current saccade matched that of a preceding saccade (e.g., two left saccades), even when the two saccades in question were separated by multiple saccades in any direction. We examined if this pattern extends to conditions in which targets appear inside continuously marked locations that provide stable visual features (i.e., target "placeholders") and when saccades are prompted by central arrows. Participants completed 3 conditions: peripheral targets (PT; continuous, sequential saccades to peripherally presented targets) without placeholders; PT with placeholders; and centrally presented arrows (CA; left or right pointing arrows at the currently fixated location instructing participants to saccade to the left or right). We found reduced saccadic RT when the immediately preceding saccade (n-1) was in the same (vs. opposite) direction in the PT without placeholders and CA conditions. This effect varied when considering the effect of the previous 2-5 (n-x) saccades on current saccade latency (n). The effects of previous eye movements on current saccade latency may be determined by multiple, time-varying mechanisms related to sensory (i.e., retinotopic location), motor (i.e., saccade direction), and environmental (i.e., persistent visual objects) factors. |
D. Jonikaitis; Artem V. Belopolsky Target-distractor competition in the oculomotor system is spatiotopic Journal Article In: Journal of Neuroscience, vol. 34, no. 19, pp. 6687–6691, 2014. @article{Jonikaitis2014, In natural scenes, multiple visual stimuli compete for selection; however, each saccade displaces the stimulus representations in retinotopicaly organized visual and oculomotor maps. In the present study, we used saccade curvature to investigate whether oculomotor competition across eye movements is represented in retinotopic or spatiotopic coordinates. Participants performed a sequence of saccades and we induced oculomotor competition by briefly presenting a task-irrelevant distractor at different times during the saccade sequence. Despite the intervening saccade, the second saccade curved away from a spatial representation of the distractor that was presented before the first saccade. Furthermore, the degree of saccade curvature increased with the salience of the distractor presented before the first saccade. The results suggest that spatiotopic representations of target-distractor competition are crucial for successful interaction with objects of interest despite the intervening eye movements. |
Kei Kanari; Hirohiko Kaneko Standard deviation of luminance distribution affects lightness and pupillary response Journal Article In: Journal of the Optical Society of America A, vol. 31, no. 12, pp. 2795–2805, 2014. @article{Kanari2014, We examined whether the standard deviation (SD) of luminance distribution serves as information of illumination. We measured the lightness of a patch presented in the center of a scrambled-dot pattern while manipulating the SD of the luminance distribution. Results showed that lightness decreased as the SD of the surround stimulus increased. We also measured pupil diameter while viewing a similar stimulus. The pupil diameter decreased as the SD of luminance distribution of the stimuli increased. We confirmed that these results were not obtained because of the increase of the highest luminance in the stimulus. Furthermore, results of field measurements revealed a correlation between the SD of luminance distribution and illuminance in natural scenes. These results indicated that the visual system refers to the SD of the luminance distribution in the visual stimulus to estimate the scene illumination. |
Min Suk Kang; Geoffrey F. Woodman The neurophysiological index of visual working memory maintenance is not due to load dependent eye movements Journal Article In: Neuropsychologia, vol. 56, no. 1, pp. 63–72, 2014. @article{Kang2014, The Contralateral Delayed Activity (CDA) is slow negative potential found during a variety of tasks, providing an important measure of the representation of information in visual working memory. However, it is studied using stimulus arrays in which the to-be-remembered objects are shown in the periphery of the left or the right visual field. Our goal was to determine whether fixational eye movements in the direction of the memoranda might underlie the CDA. We found that subjects' gaze was shifted toward the visual field of the memoranda during the retention interval, with its magnitude increasing with the set size. However, the CDA was clearly observed even when the subjects' gaze shifts were absent. In addition, the magnitude of the subjects' gaze shifts was unrelated to their visual working memory capacity measured with behavioral data, unlike the CDA. Finally, the onset latency of the set size dependent eye movements followed the onset of the set size dependent CDA. Thus, our findings clearly show that the CDA does not represent a simple inability to maintain fixation during visual working memory maintenance, but that this neural index of representation in working memory appears to induce eye movements toward the locations of the objects being remembered. |
Koji Kashihara; Kazuo Okanoya; Nobuyuki Kawai Emotional attention modulates microsaccadic rate and direction Journal Article In: Psychological Research, vol. 78, no. 2, pp. 166–179, 2014. @article{Kashihara2014, Involuntary microsaccades and voluntary saccades reflect human brain activities during attention and cognitive tasks. Our eye movements can also betray our emotional state. However, the effects of attention to emotion on microsaccadic activity remain unknown. The present study was conducted in healthy volunteers to investigate the effects of devoting attention to exogenous emotional stimuli on microsaccadic response, with change in pupil size as an index of sympathetic nervous system activity. Event-related responses to unpleasant images significantly inhibited the rate of microsaccade appearance and altered pupil size (Experiment 1). Additionally, microsaccadic responses to covert orienting of attention to emotional stimuli appeared significantly in the anti-direction to a target, with a fast reaction time (Experiment 2). Therefore, we concluded that attentional shifts induced by exogenous emotional stimuli can modulate microsaccadic activities. Future studies of the interaction between miniature eye movements and emotion may be beneficial in the assessment of pathophysiological responses in mental disorders. |
Afsheen Khan; Sally A. McFadden; Mark R. Harwood; Josh Wallman Salient distractors can induce saccade adaptation Journal Article In: Journal of Ophthalmology, vol. 2014, pp. 1–11, 2014. @article{Khan2014, When saccadic eye movements consistently fail to land on their intended target, saccade accuracy is maintained by gradually adapting the movement size of successive saccades. The proposed error signal for saccade adaptation has been based on the distance between where the eye lands and the visual target (retinal error). We studied whether the error signal could alternatively be based on the distance between the predicted and actual locus of attention after the saccade. Unlike conventional adaptation experiments that surreptitiously displace the target once a saccade is initiated towards it, we instead attempted to draw attention away from the target by briefly presenting salient distractor images on one side of the target after the saccade. To test whether less salient, more predictable distractors would induce less adaptation, we separately used fixed random noise distractors. We found that both visual attention distractors were able to induce a small degree of downward saccade adaptation but significantly more to the more salient distractors. As in conventional adaptation experiments, upward adaptation was less effective and salient distractors did not significantly increase amplitudes. We conclude that the locus of attention after the saccade can act as an error signal for saccade adaptation. |
Eileen Kowler; Cordelia D. Aitkin; Nicholas M. Ross; Elio M. Santos; Min Zhao Davida Teller Award Lecture 2013: The importance of prediction and anticipation in the control of smooth pursuit eye movements Journal Article In: Journal of Vision, vol. 14, no. 5, pp. 1–16, 2014. @article{Kowler2014, The ability of smooth pursuit eye movements to anticipate the future motion of targets has been known since the pioneering work of Dodge, Travis, and Fox (1930) and Westheimer (1954). This article reviews aspects of anticipatory smooth eye movements, focusing on the roles of the different internal or external cues that initiate anticipatory pursuit.We present new results showing that the anticipatory smooth eye movements evoked by different cues differ substantially, even when the cues are equivalent in the information conveyed about the direction of future target motion. Cues that convey an easily interpretable visualization of the motion path produce faster anticipatory smooth eye movements than the other cues tested, including symbols associated arbitrarily with the path, and the same target motion tested repeatedly over a block of trials. The differences among the cues may be understood within a common predictive framework in which the cues differ in the level of subjective certainty they provide about the future path. Pursuit may be driven by a combined signal in which immediate sensory motion, and the predictions about future motion generated by sets of cues, are weighted according to their respective levels of certainty. Anticipatory smooth eye movements, an overt indicator of expectations and predictions, may not be operating in isolation, but may be part of a global process in which the brain analyzes available cues, formulates predictions, and uses them to control perceptual, motor, and cognitive processes. |
Wouter Kruijne; Stefan Van der Stigchel; Martijn Meeter A model of curved saccade trajectories: Spike rate adaptation in the brainstem as the cause of deviation away Journal Article In: Brain and Cognition, vol. 85, no. 1, pp. 259–270, 2014. @article{Kruijne2014, The trajectory of saccades to a target is often affected whenever there is a distractor in the visual field. Distractors can cause a saccade to deviate towards their location or away from it. The oculomotor mechanisms that produce deviation towards distractors have been thoroughly explored in behavioral, neurophysiological and computational studies. The mechanisms underlying deviation away, on the other hand, remain unclear. Behavioral findings suggest a mechanism of spatially focused, top-down inhibition in a saccade map, and deviation away has become a tool to investigate such inhibition. However, this inhibition hypothesis has little neuroanatomical or neurophysiological support, and recent findings go against it. Here, we propose that deviation away results from an unbalanced saccade drive from the brainstem, caused by spike rate adaptation in brainstem long-lead burst neurons. Adaptation to stimulation in the direction of the distractor results in an unbalanced drive away from it. An existing model of the saccade system was extended with this theory. The resulting model simulates a wide range of findings on saccade trajectories, including findings that have classically been interpreted to support inhibition views. Furthermore, the model replicated the effect of saccade latency on deviation away, but predicted this effect would be absent with large (400. ms) distractor-target onset asynchrony. This prediction was confirmed in an experiment, which demonstrates that the theory both explains classical findings on saccade trajectories and predicts new findings. |
Alexandre Lang; Chrystal Gaertner; Elham Ghassemi; Qing Yang; Christophe Orssaud; Zoï Kapoula Saccade-vergence properties remain more stable over short-time repetition under overlap than under gap task: A preliminary study Journal Article In: Frontiers in Human Neuroscience, vol. 8, pp. 372, 2014. @article{Lang2014, Under natural circumstances, saccade-vergence eye movements are among the most frequently occurring. This study examines the properties of such movements focusing on short-term repetition effects. Are such movements robust over time or are they subject to tiredness? 12 healthy adults performed convergent and divergent combined eye movements either in a gap task (i.e., 200 ms between the end of the fixation stimulus and the beginning of the target stimulus) or in an overlap task (i.e., the peripheral target begins 200 ms before the end of the fixation stimulus). Latencies were shorter in the gap task than in the overlap task for both saccade and vergence components. Repetition had no effect on latency, which is a novel result. In both tasks, saccades were initiated later and executed faster (mean and peak velocities) than the vergence component. The mean and peak velocities of both components decreased over trials in the gap task but remained constant in the overlap task. This result is also novel and has some clinical implications. Another novel result concerns the accuracy of the saccade component that was better in the gap than in the overlap task. The accuracy also decreased over trials in the gap task but remained constant in the overlap task. The major result of this study is that under a controlled mode of initiation (overlap task) properties of combined eye movements are more stable than under automatic triggering (gap task). These results are discussed in terms of saccade-vergence interactions, convergence-divergence specificities and repetition versus adaptation protocols. |
Stephen Layfield; Wesley Burge; William G. Mitchell; Lesley A. Ross; Christine Denning; Frank Amthor; Kristina M. Visscher The effect of speed of processing training on microsaccade amplitude Journal Article In: PLoS ONE, vol. 9, no. 9, pp. e107808, 2014. @article{Layfield2014, Older adults experience cognitive deficits that can lead to driving errors and a loss of mobility. Fortunately, some of these deficits can be ameliorated with targeted interventions which improve the speed and accuracy of simultaneous attention to a central and a peripheral stimulus called Speed of Processing training. To date, the mechanisms behind this effective training are unknown. We hypothesized that one potential mechanism underlying this training is a change in distribution of eye movements of different amplitudes. Microsaccades are small amplitude eye movements made when fixating on a stimulus, and are thought to counteract the "visual fading" that occurs when static stimuli are presented. Due to retinal anatomy, larger microsaccadic eye movements are needed to move a peripheral stimulus between receptive fields and counteract visual fading. Alternatively, larger microsaccades may decrease performance due to neural suppression. Because larger microsaccades could aid or hinder peripheral vision, we examine the distribution of microsaccades during stimulus presentation. Our results indicate that there is no statistically significant change in the proportion of large amplitude microsaccades during a Useful Field of View-like task after training in a small sample of older adults. Speed of Processing training does not appear to result in changes in microsaccade amplitude, suggesting that the mechanism underlying Speed of Processing training is unlikely to rely on microsaccades. |
Dongpyo Lee; Howard Poizner; Daniel M. Corcos; Denise Y. P. Henriques Unconstrained reaching modulates eye-hand coupling Journal Article In: Experimental Brain Research, vol. 232, no. 1, pp. 211–223, 2014. @article{Lee2014b, Eye–hand coordination is a crucial element of goal-directed movements. However, few studies have looked at the extent to which unconstrained movements of the eyes and hand made to targets influence each other. We studied human participants who moved either their eyes or both their eyes and hand to one of three static or flashed targets presented in 3D space. The eyes were directed, and hand was located at a common start position on either the right or left side of the body. We found that the velocity and scatter of memory-guided saccades (flashed targets) differed significantly when produced in combination with a reaching movement than when produced alone. Specifically, when accompanied by a reach, peak saccadic velocities were lower than when the eye moved alone. Peak saccade velocities, as well as latencies, were also highly correlated with those for reaching movements, especially for the briefly flashed targets compared to the continuous visible target. The scatter of saccade endpoints was greater when the saccades were produced with the reaching movement than when produced without, and the size of the scatter for both saccades and reaches was weakly correlated. These findings suggest that the saccades and reaches made to 3D targets are weakly to moderately coupled both temporally and spatially and that this is partly the result of the arm movement influencing the eye movement. Taken together, this study provides further evidence that the oculomotor and arm motor systems interact above and beyond any common target representations shared by the two motor systems. |
Delphine Lévy-Bencheton; Denis Pélisson; Muriel T. N. Panouillères; Christian Urquizar; Caroline Tilikete; Laure Pisella Adaptation of scanning saccades co-occurs in different coordinate systems Journal Article In: Journal of Neurophysiology, vol. 111, no. 12, pp. 2505–2515, 2014. @article{LevyBencheton2014, Plastic changes of saccades (i.e., following saccadic adaptation) do not transfer between oppositely directed saccades, except when multiple directions are trained simultaneously, suggesting a saccadic planning in retinotopic coordinates. Interestingly, a recent study in human healthy subjects revealed that after an adaptive increase of rightward-scanning saccades, both leftward and rightward double-step, memory-guided saccades, triggered toward the adapted endpoint, were modified, revealing that target location was coded in spatial coordinates (Zimmermann et al. 2011). However, as the computer screen provided a visual frame, one alternative hypothesis could be a coding in allocentric coordinates. Here, we questioned whether adaptive modifications of saccadic planning occur in multiple coordinate systems. We reproduced the paradigm of Zimmermann et al. (2011) using target light-emitting diodes in the dark, with and without a visual frame, and tested different saccades before and after adaptation. With double-step, memory-guided saccades, we reproduced the transfer of adaptation to leftward saccades with the visual frame but not without, suggesting that the coordinate system used for saccade planning, when the frame is visible, is allocentric rather than spatiotopic. With single-step, memory-guided saccades, adaptation transferred to leftward saccades, both with and without the visual frame, revealing a target localization in a coordinate system that is neither retinotopic nor allocentric. Finally, with single-step, visually guided saccades, the classical, unidirectional pattern of amplitude change was reproduced, revealing retinotopic coordinate coding. These experiments indicate that the same procedure of adaptation modifies saccadic planning in multiple coordinate systems in parallel-each of them revealed by the use of different saccade tasks in postadaptation. |
Moshe Fried; Eteri Tsitsiashvili; Yoram S. Bonneh; Anna Sterkin; Tamara Wygnanski-Jaffe; Tamir Epstein; Uri Polat ADHD subjects fail to suppress eye blinks and microsaccades while anticipating visual stimuli but recover with medication Journal Article In: Vision Research, vol. 101, pp. 62–72, 2014. @article{Fried2014, Oculomotor behavior and parameters are known to be affected by the allocation of attention and could potentially be used to investigate attention disorders. We explored the oculomotor markers of Attention-deficit/hyperactivity disorder (ADHD) that are involuntary and quantitative and that could be used to reveal the core-affected mechanisms, as well as be used for differential diagnosis. We recorded eye movements in a group of 22 ADHD-diagnosed patients with and without medication (methylphenidate) and in 22 control observers while performing the test of variables of attention (t.o.v.a.). We found that the average microsaccade and blink rates were higher in the ADHD group, especially in the time interval around stimulus onset. These rates increased monotonically over session time for both groups, but with significantly faster increments in the unmedicated ADHD group. With medication, the level and time course of the microsaccade rate were fully normalized to the control level, regardless of the time interval within trials. In contrast, the pupil diameter decreased over time within sessions and significantly increased above the control level with medication. We interpreted the suppression of microsaccades and eye blinks around the stimulus onset as reflecting a temporal anticipation mechanism for the transient allocation of attention, and their overall rates as inversely reflecting the level of arousal. We suggest that ADHD subjects fail to maintain sufficient levels of arousal during a simple and prolonged task, which limits their ability to dynamically allocate attention while anticipating visual stimuli. This impairment normalizes with medication and its oculomotor quantification could potentially be used for differential diagnosis. |
Fatema F. Ghasia; Aasef G. Shaikh Source of high-frequency oscillations in oblique saccade trajectory Journal Article In: Experimental Eye Research, vol. 121, pp. 5–10, 2014. @article{Ghasia2014a, Most common eye movements, oblique saccades, feature rapid velocity, precise amplitude, but curved trajectory that is variable from trial-to-trial. In addition to curvature and inter-trial variability, the oblique saccade trajectory also features high-frequency oscillations. A number of studies proposed the physiological basis of the curvature and inter-trial variability of the oblique saccade trajectory, but kinematic characteristics of high-frequency oscillations are yet to be examined. We measured such oscillations and compared their properties with orthogonal pure horizontal and pure vertical oscillations generated during pure vertical and pure horizontal saccades, respectively. We found that the frequency of oscillations during oblique saccades ranged between 15 and 40Hz, consistent with the frequency of orthogonal saccadic oscillations during pure horizontal or pure vertical saccades. We also found that the amplitude of oblique saccade oscillations was larger than pure horizontal and pure vertical saccadic oscillations. These results suggest that the superimposed high-frequency sinusoidal oscillations upon the oblique saccade trajectory represent reverberations of disinhibited circuit of reciprocally innervated horizontal and vertical burst generators. |
Esther G. González; Linda Lillakas; Naomi Greenwald; Brenda L. Gallie; Martin J. Steinbach Unaffected smooth pursuit but impaired motion perception in monocularly enucleated observers Journal Article In: Vision Research, vol. 101, pp. 151–157, 2014. @article{Gonzalez2014, The objective of this paper was to study the characteristics of closed-loop smooth pursuit eye movements of 15 unilaterally eye enucleated individuals and 18 age-matched controls and to compare them to their performance in two tests of motion perception: relative motion and motion coherence. The relative motion test used a brief (150. ms) small stimulus with a continuously present fixation target to preclude pursuit eye movements. The duration of the motion coherence trials was 1. s, which allowed a brief pursuit of the stimuli. Smooth pursuit data were obtained with a step-ramp procedure. Controls were tested both monocularly and binocularly. The data showed worse performance by the enucleated observers in the relative motion task but no statistically significant differences in motion coherence between the two groups. On the other hand, the smooth pursuit gain of the enucleated participants was as good as that of controls for whom we found no binocular advantage. The data show that enucleated observers do not exhibit deficits in the afferent or sensory pathways or in the efferent or motor pathways of the steady-state smooth pursuit system even though their visual processing of motion is impaired. |
Andrei Gorea; Delphine Rider; Qing Yang A unified comparison of stimulus-driven, endogenous mandatory and 'free choice' saccades Journal Article In: PLoS ONE, vol. 9, no. 2, pp. e88990, 2014. @article{Gorea2014, It has been claimed that saccades arising from the three saccade triggering modes-stimulus-driven, endogenous mandatory and 'free choice'-are driven by distinct mechanisms. We tested this claim by instructing observers to saccade from a white or black fixation disc to a same polarity (white or black) disc flashed for 100 or 200 ms presented either alone (Exo), or together with an opposite (Endo) or same (EndoFC) polarity disc (blocked and mixed sessions). Target(s) and distractor were presented at three inter-stimulus intervals (ISIs) relative to the fixation offset (ISI: -200, 0, +200 ms) and were displayed at random locations within a 4°-to-6° eccentricity range. The statistical analysis showed a global saccade triggering mode effect on saccade reaction times (SRTs) with Endo and EndoFC SRTs longer by about 27 ms than Exo-triggered ones but no effect for the Endo-EndoFC comparison. SRTs depended on both ISI (the "gap-effect"), and target duration. Bimodal best fits of the SRT-distributions were found in 65% of cases with their count not different across the three triggering modes. Percentages of saccades in the 'fast' and 'slow' ranges of bimodal fits did not depend on the triggering modes either. Bimodality tests failed to assert a significant difference between these modes. An analysis of the timing of a putative inhibition by the distractor (Endo) or by the duplicated target (EndoFC) yielded no significant difference between Endo and EndoFC saccades but showed a significant shortening with ISI similar to the SRT shortening suggesting that the distractor-target mutual inhibition is itself inhibited by 'fixation' neurons. While other experimental paradigms may well sustain claims of distinct mechanisms subtending the three saccade triggering modes, as here defined reflexive and voluntary saccades appear to differ primarily in the effectiveness with which inhibitory processes slow down the initial fast rise of the saccade triggering signal. |
Harriet Goschy; A. Isabel Koch; Hermann J. Müller; Michael Zehetleitner Early top-down control over saccadic target selection: Evidence from a systematic salience difference manipulation Journal Article In: Attention, Perception, and Psychophysics, vol. 76, no. 2, pp. 367–382, 2014. @article{Goschy2014, Previous research on the contribution of top-down control to saccadic target selection has suggested that eye movements, especially short-latency saccades, are primarily salience driven. The present study was designed to systematically examine top-down influences as a function of time and relative salience difference between target and distractor. Observers performed a saccadic selection task, requiring them to make an eye movement to an orientation-defined target, while ignoring a color-defined distractor. The salience of the distractor was varied (five levels), permitting the percentage of target and distractor fixations to be analyzed as a function of the salience difference between the target and distractor. This analysis revealed the same pattern of results for both the overall and the short-latency saccades: When the target and distractor were of comparable salience, the vast majority of saccades went directly to the target; even distractors somewhat more salient than the target led to significantly fewer distractor, as compared with target, fixations. To quantify the amount of top-down control applied, we estimated the point of equal selection probability for the target and distractor. Analyses of these estimates revealed that, to be selected with equal probability to the target, a distractor had to have a considerably greater bottom-up salience, as compared with the target. This difference suggests a strong contribution of top-down control to saccadic target selection-even for the earliest saccades. |
Michael J. Gray; Annabelle Blangero; James P. Herman; Josh Wallman; Mark R. Harwood Adaptation of naturally paced saccades Journal Article In: Journal of Neurophysiology, vol. 111, no. 11, pp. 2343–2354, 2014. @article{Gray2014, In the natural environment, humans make saccades almost continuously. In many eye movement experiments, however, observers are required to fixate for unnaturally long periods of time. The resulting long and monotonous experimental sessions can become especially problematic when collecting data in a clinical setting, where time can be scarce and subjects easily fatigued. With this in mind, we tested whether the well-studied motor learning process of saccade adaptation could be induced with a dramatically shortened intertrial interval. Observers made saccades to targets that stepped left or right either ∼250 ms or ∼1,600 ms after the saccade landed. In experiment I, we tested baseline saccade parameters to four different target amplitudes (5°, 10°, 15°, and 20°) in the two timing settings. In experiments II and III, we adapted 10° saccades via 2° intrasaccadic steps either backwards or forwards, respectively. Seven subjects performed eight separate adaptation sessions (2 intertrial timings × 2 adaptation direction × 2 session trial lengths). Adaptation proceeded remarkably similarly in both timing conditions across the multiple sessions. In the faster-paced sessions, robust adaptation was achieved in under 2 min, demonstrating the efficacy of our approach to streamlining saccade adaptation experiments. Although saccade amplitudes were similar between conditions, the faster-paced condition unexpectedly resulted in significantly higher peak velocities in all subjects. This surprising finding demonstrates that the stereotyped "main sequence" relationship between saccade amplitude and peak velocity is not as fixed as originally thought. |
Xiao-Jing Gu; Ming Hu; Bing Li; Xin-Tian Hu The role of contrast adaptation in saccadic suppression in humans Journal Article In: PLoS ONE, vol. 9, no. 1, pp. e86542, 2014. @article{Gu2014, The idea of retinal and ex-retinal sources of saccadic suppression has long been established in previous studies. However, how they are implemented in local circuit remains unknown. Researchers have suggested that saccadic suppression was probably achieved by contrast gain control, but this possibility has never been directly tested. In this study, we manipulated contrast gain control by contrast-adapting observers with sinusoidal gratings of different contrasts. Presaccadic and fixational contrast thresholds were measured and compared to give estimates of saccadic suppression at different adaptation states. Our results reconfirmed the selective saccadic suppression in achromatic condition, and further showed that, achromatic saccadic suppression diminished as contrast adaptation was accentuated, whereas no significant chromatic saccadic suppression was induced by greater contrast adaptation. Our data provided evidence for the involvement of contrast gain control in saccadic suppression in achromatic channel. We also discussed how the negative correlation between contrast adaptation and saccadic suppression could be interpreted with contrast gain control. |
Reza Azadi; Mark R. Harwood Visual cues that are effective for contextual saccade adaptation Journal Article In: Journal of Neurophysiology, vol. 111, no. 11, pp. 2307–2319, 2014. @article{Azadi2014, The accuracy of saccades, as maintained by saccade adaptation, has been shown to be context dependent: able to have different amplitude movements to the same retinal displacement dependent on motor contexts such as orbital starting location. There is conflicting evidence as to whether purely visual cues also effect contextual saccade adaptation and, if so, what function this might serve. We tested what visual cues might evoke contextual adaptation. Over 5 experiments, 78 naive subjects made saccades to circularly moving targets, which stepped outward or inward during the saccade depending on target movement direction, speed, or color and shape. To test if the movement or context postsaccade were critical, we stopped the postsaccade target motion ( experiment 4 ) or neutralized the contexts by equating postsaccade target speed to an intermediate value ( experiment 5 ). We found contextual adaptation in all conditions except those defined by color and shape. We conclude that some, but not all, visual cues before the saccade are sufficient for contextual adaptation. We conjecture that this visual contextuality functions to allow for different motor states for different coordinated movement patterns, such as coordinated saccade and pursuit motor planning. |
Pablo A. Barrionuevo; Nathaniel Nicandro; J. Jason McAnany; Andrew J. Zele; Paul Gamlin; Dingcai Cao Assessing rod, cone, and melanopsin contributions to human pupil flicker responses Journal Article In: Investigative Ophthalmology & Visual Science, vol. 55, no. 2, pp. 719–727, 2014. @article{Barrionuevo2014, PURPOSE: We determined the relative contributions of rods, cones, and melanopsin to pupil responses in humans using temporal sinusoidal stimulation for light levels spanning the low mesopic to photopic range. METHODS: A four-primary Ganzfeld photostimulator controlled flicker stimulations at seven light levels (-2.7 to 2 log cd/m(2)) and five frequencies (0.5-8 Hz). Pupil diameter was measured using a high-resolution eye tracker. Three kinds of sinusoidal photoreceptor modulations were generated using silent substitution: rod modulation, cone modulation, and combined rod and cone modulation in phase (experiment 1) or cone phase shifted (experiment 2) from a fixed rod phase. The melanopsin excitation was computed for each condition. A vector sum model was used to estimate the relative contribution of rods, cones, and melanopsin to the pupil response. RESULTS: From experiment 1, the pupil frequency response peaked at 1 Hz at two mesopic light levels for the three modulation conditions. Analyzing the rod-cone phase difference for the combined modulations (experiment 2) identified a V-shaped response amplitude with a minimum between 135° and 180°. The pupil response phases increased as cone modulation phase increased. The pupil amplitude increased with increasing light level for cone, and combined (in-phase rod and cone) modulation, but not for the rod modulation. CONCLUSIONS: These results demonstrate that cone- and rod-pathway contributions are more predominant than melanopsin contribution to the phasic pupil response. The combined rod, cone, and melanopsin inputs to the phasic state of the pupil light reflex follow linear summation. |