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2019 |
Heather J. Ferguson; Jo Black; David Williams Distinguishing reality from fantasy in adults with autism spectrum disorder: Evidence from eye movements and reading Journal Article In: Journal of Memory and Language, vol. 106, pp. 95–107, 2019. @article{Ferguson2019, Understanding fictional events requires one to distinguish reality from fantasy, and thus engages high-level processes including executive functions and imagination, both of which are impaired in autism spectrum disorder (ASD). We examined how adults with and without ASD make sense of reality-violating fantasy narratives by testing real-time understanding of counterfactuals. Participants were eye-tracked as they read narratives that depicted novel counterfactual scenarios that violate reality (e.g. “If margarine contained detergent, Mum could use margarine in her washing/baking” Experiment 1), or counterfactual versions of known fictional worlds (e.g. “If Harry Potter had lost all his magic powers, he would use his broom to sweep/fly” Experiment 2). Results revealed anomaly detection effects in the early moments of processing (immediately in Experiment 1, and from the post-critical region in Experiment 2), which were not modulated by group. We discuss these findings in relation to the constraints from real-world and fantasy contexts that compete to influence language comprehension, and identify a dissociation between ToM impairments and counterfactual processing abilities. |
Eva Findelsberger; Florian Hutzler; Stefan Hawelka Spill the load: Mixed evidence for a foveal load effect, reliable evidence for a spillover effect in eye-movement control during reading Journal Article In: Attention, Perception, and Psychophysics, vol. 81, no. 5, pp. 1442–1453, 2019. @article{Findelsberger2019, It has been hypothesized that the processing difficulty of the fixated word (i.e., “foveal load”) modulates the amount of parafoveal preprocessing of the next word. Evidence for the hypothesis has been provided by the application of parafoveal masks within the boundary paradigm. Other studies that applied alternative means of manipulating the parafoveal preview (i.e., visual degradation) could not replicate the effect of foveal load. The present study examined the effect of foveal load by directly comparing the application of parafoveal masks (Exp. 1) with the alternative manipulation of visually degrading the parafoveal preview (Exp. 2) in adult readers. Contrary to expectation, we did not find the foveal-load interaction in the first experiment with traditional letter masks. We did, however, find the expected interaction in the second experiment with visually degraded previews. Both experiments revealed a spillover effect indicating that the processing of a word is not (always) fully completed when the reader already fixates the next word (i.e., processing “spills over” to the next word). The implications for models of eye-movement control in reading are discussed. |
Gemma Fitzsimmons; Mark J. Weal; Denis Drieghe The impact of hyperlinks on reading text Journal Article In: PLoS ONE, vol. 14, no. 2, pp. e0210900, 2019. @article{Fitzsimmons2019, There has been debate about whether blue hyperlinks on the Web cause disruption to reading. A series of eye tracking experiments were conducted to explore if coloured words in black text had any impact on reading behaviour outside and inside a Web environment. Experiment 1 and 2 explored the saliency of coloured words embedded in single sentences and the impact on reading behaviour. In Experiment 3, the effects of coloured words/hyperlinks in passages of text in a Web-like environment was explored. Experiment 1 and 2 showed that multiple coloured words in text had no negative impact on reading behaviour. However, if the sentence featured only a single coloured word, a reduction in skipping rates was observed. This suggests that the visual saliency associated with a single coloured word may signal to the reader that the word is important, whereas this signalling is reduced when multiple words are coloured. In Experiment 3, when reading passages of text containing hyperlinks in a Web environment, participants showed a tendency to re-read sentences that contained hyperlinked, uncommon words compared to hyperlinked, common words. Hyperlinks highlight important information and suggest additional content, which for more difficult concepts, invites rereading of the preceding text. |
Kathleen C. Fraser; Kristina Lundholm Fors; Marie Eckerström; Fredrik Öhman; Dimitrios Kokkinakis Predicting MCI status from multimodal language data using cascaded classifiers Journal Article In: Frontiers in Aging Neuroscience, vol. 11, pp. 205, 2019. @article{Fraser2019, Recent work has indicated the potential utility of automated language analysis for the detection of mild cognitive impairment (MCI). Most studies combining language processing and machine learning for the prediction of MCI focus on a single language task; here, we consider a cascaded approach to combine data from multiple language tasks. A cohort of 26 MCI participants and 29 healthy controls completed three language tasks: picture description, reading silently, and reading aloud. Information from each task is captured through different modes (audio, text, eye-tracking, and comprehension questions). Features are extracted from each mode, and used to train a series of cascaded classifiers which output predictions at the level of features, modes, tasks, and finally at the overall session level. The best classification result is achieved through combining the data at the task level (AUC = 0.88 |
Cheryl Frenck-Mestre; Seung Kyung Kim; Hyeree Choo; Alain Ghio; Julia Herschensohn; Sungryong Koh Look and listen! The online processing of Korean case by native and non-native speakers Journal Article In: Language, Cognition and Neuroscience, vol. 34, no. 3, pp. 385–404, 2019. @article{FrenckMestre2019, We used a forced choice visual world paradigm to examine when listeners integrate case when processing Korean, in native speakers and two groups of adult L2 learners. The L2 learners varied as concerns the typological proximity between their L1 (French or Kazakh) and Korean. Processing was compared for canonical (SOV) and scrambled (OSV) word order. Nominal case marking was either accusative (NOM-ACC) or dative (NOM-DAT). Native Koreans showed anticipatory looks to the correct image, regardless of word order or case. Neither L2 group showed anticipatory looks to the correct image prior to the final auditory verb. Both L2 groups demonstrated superior performance for the dative. However, the Kazakh group showed better capacities to correctly interpret utterances based on case than the French. Our results provide evidence of the incremental nature of processing in Korean for native speakers and, for L2 learners, the effect of L1–L2 overlap and specific case marking |
Lee Friedman; Oleg V. Komogortsev Assessment of the effectiveness of 7 biometric feature normalization techniques Journal Article In: IEEE Transactions on Information Forensics and Security, vol. 14, no. 10, pp. 2528–2536, 2019. @article{Friedman2019, The importance of normalizing biometric features or matching scores is understood in the multimodal biometric case, but there is less attention to the unimodal case. Prior reports assess the effectiveness of normalization directly on biometric performance. We propose that this process is logically comprised of two independent steps: (1) methods to equalize the effect of each biometric feature on the similarity scores calculated from all the features together and (2) methods of weighting the normalized features to optimize biometric performance. In this report, we address step 1 only and focus exclusively on normally distributed features. We show how differences in the variance of features lead to differences in the strength of the influence of each feature on the similarity scores produced from all the features. Since these differences in variance have nothing to do with importance in the biometric sense, it makes no sense to allow them to have greater weight in the assessment of biometric performance. We employed two types of features: (1) real eye-movement features and (2) synthetic features. We compare six variance normalization methods (histogram equalization, L1-normalization, median normalization, z-score normalization, min-max normalization, and L-infinite normalization) and one distance metric (Mahalanobis distance) in terms of how well they reduce the impact of the variance differences. The effectiveness of different techniques on real data depended on the strength of the inter-correlation of the features. For weakly correlated real features and synthetic features, histogram equalization was the best method followed by L1 normalization. |
Isidora Gatarić The cognitive processing of derived nouns with ambiguous suffixes: Behavioral and eye-emovement study Journal Article In: Primenjena Psihologija, vol. 12, no. 1, pp. 85–104, 2019. @article{Gataric2019, The primary aim of this research has been to investigate whether the suffix ambiguity affects the lexical processing of derived nouns in Serbian. Consequently, in the Experiment 1, the derived nouns were presented isolated to participants in the visual lexical decision task. Bearing in mind that the sentence context was important for the lexical processing, the Experiment 2 was designed as an eye-movement study with the sentences (with derived nouns from the Experiment 1) as stimuli. To the best of our knowledge, the similar experimental study was not performed before in the Serbian language, and therefore this study represents the first attempt to investigate this phenomenon in Serbian. An identical statistical analysis was used to analyze the data collected in both experiments, the Generalized Additive Mixed Models (GAMMs). The final results of all GAMMs analyses suggested that the suffixal ambiguity did not affect the lexical processing of derived nouns in Serbian, regardless of whether they were displayed isolated or in the sentence context. The observed results supported the a-morphous perspective in the morpho-lexical processing, as well as the distributed morphology insights from the theoretical linguistics. |
Martina Micai; Mila Vulchanova; David Saldaña Do individuals with autism change their reading behavior to adapt to errors in the text? Journal Article In: Journal of Autism and Developmental Disorders, vol. 39, pp. 4232–4243, 2019. @article{Micai2019, Reading monitoring is poorly explored, but it may have an impact on well-documented reading comprehension difficulties in autism. This study explores reading monitoring through the impact of instructions and different error types on reading behavior. Individuals with autism and matched controls read correct sentences and sentences containing orthographic and semantic errors. Prior to the task, participants were given instructions either to focus on semantic or orthographic errors. Analysis of eye-movements showed that the group with autism, differently from controls, were less influenced by the error's type in the regression-out to-error measure, showing less change in eye-movements behavior between error types. Individuals with autism might find it more difficult to adapt their reading strategies to various reading materials and task demands. |
Evelyn Milburn; Tessa Warren Idioms show effects of meaning relatedness and dominance similar to those seen for ambiguous words Journal Article In: Psychonomic Bulletin & Review, vol. 26, no. 2, pp. 591–598, 2019. @article{Milburn2019, Does the language comprehension system resolve ambiguities for single- and multiple-word units similarly? We investigate this question by examining whether two constructs with robust effects on ambiguous word processing – meaning relatedness and meaning dominance – have similar influences on idiom processing. Eye tracking showed that: (1) idioms with more related figurative and literal meanings were read faster, paralleling findings for ambiguous words, and (2) meaning relatedness and meaning dominance interacted to drive eye movements on idioms just as they do on polysemous ambiguous words. These findings are consistent with a language comprehension system that resolves ambiguities similarly regardless of literality or the number of words in the unit. |
Jonathan Mirault; Joshua Snell; Jonathan Grainger Reading without spaces revisited: The role of word identification and sentence-level constraints Journal Article In: Acta Psychologica, vol. 195, pp. 22–29, 2019. @article{Mirault2019, The present study examined the relative contribution of bottom-up word identification and top-down sentence-level constraints in facilitating the reading of text printed without between-word spacing. We compared reading of grammatically correct sentences and shuffled versions of the same words presented both with normal spacing and without spaces. We found that reading was hampered by removing sentence structure as well as by removing spaces. A significantly greater impact of sentence structure when reading unspaced text was found in probe word identification accuracies and total viewing times per word, whereas the impact of sentence structure on the probability of making a regressive eye movement was greater when reading normally spaced text. Crucially, we also found that the length of the currently fixated word determined the amplitude of forward saccades leaving that word during the reading of unspaced text. We conclude that the relative ease with which skilled readers can read unspaced text is due to a combination of an increased use of bottom-up word identification in guiding the timing and targeting of eye movements, plus an increased interactivity between word identification and sentence level processing. |
Jonathan Mirault; Joshua Snell; Jonathan Grainger Reading without spaces: The role of precise letter order Journal Article In: Attention, Perception, and Psychophysics, vol. 81, no. 3, pp. 846–860, 2019. @article{Mirault2019a, Prior research points to efficient identification of embedded words as a key factor in facilitating the reading of text printed without spacing between words. Here we further tested the primary role of bottom-up word identification by altering this process with a letter transposition manipulation. In two experiments, we examined silent reading and reading aloud of normal sentences and sentences containing words with letter transpositions, in both normally spaced and unspaced conditions. We predicted that letter transpositions should be particularly harmful for reading unspaced text. In line with our prediction, the majority of our measures of reading fluency showed that unspaced text with letter transpositions was disproportionately difficult to read. These findings provide further support for the claim that reading text without between-word spacing relies principally on efficient bottom-up processing, enabling accurate word identification in the absence of visual cues to identify word boundaries. |
Jelena Mirković; Gerry T. M. Altmann Unfolding meaning in context: The dynamics of conceptual similarity Journal Article In: Cognition, vol. 183, pp. 19–43, 2019. @article{Mirkovic2019, How are relationships between concepts affected by the interplay between short-term contextual constraints and long-term conceptual knowledge? Across two studies we investigate the consequence of changes in visual context for the dynamics of conceptual processing. Participants' eye movements were tracked as they viewed a visual depiction of e.g. a canary in a birdcage (Experiment 1), or a canary and three unrelated objects, each in its own quadrant (Experiment 2). In both studies participants heard either a semantically and contextually similar “robin” (a bird; similar size), an equally semantically similar but not contextually similar “stork” (a bird; bigger than a canary, incompatible with the birdcage), or unrelated “tent”. The changing patterns of fixations across time indicated first, that the visual context strongly influenced the eye movements such that, in the context of a birdcage, early on (by word offset) hearing “robin” engendered more looks to the canary than hearing “stork” or “tent” (which engendered the same number of looks), unlike in the context of unrelated objects (in which case “robin” and “stork” engendered equivalent looks to the canary, and more than did “tent”). Second, within the 500 ms post-word-offset eye movements in both experiments converged onto a common pattern (more looks to the canary after “robin” than after “stork” and for both more than after “tent”). We interpret these findings as indicative of the dynamics of activation within semantic memory accessed via pictures and via words, and reflecting the complex interaction between systems representing context-independent and context-dependent conceptual knowledge driven by predictive processing. |
Holger Mitterer; Sahyang Kim; Taehong Cho The glottal stop between segmental and suprasegmental processing: The case of Maltese Journal Article In: Journal of Memory and Language, vol. 108, pp. 1–20, 2019. @article{Mitterer2019, Many languages mark vowel-initial words with a glottal stop. We show that this occurs in Maltese, even though the glottal stop also occurs as a phoneme in Maltese. As a consequence, words with and without an underlying (phonemic) glottal stop (e.g., a glottal stop-zero minimal pair qal /Ɂɑ:l/ vs. ghal /ɑ:l/ Engl., ‘he said'-‘because') can become homophonous in connected speech. We first tested the extent of this phonetic marking of vowel-initial words in a production experiment and found that even in fluent productions, about half of the vowel-initial words are marked with an epenthetic glottal stop. The epenthetic glottal stop is more likely to occur when the preceding word is longer, showing a kind of preboundary lengthening at a phrase-level prosodic boundary. A subsequent perception study (Experiment 2) using a two-alternative forced-choice task with a minimal pair of a glottal stop-initial and a vowel-initial word indicated that listeners are sensitive to the durationally conditioned prosodic context before the test word, and they are more likely to perceive a vowel-initial word when the preceding word is lengthened. An additional eye-tracking study (Experiment 3) using onset-overlap pairs (e.g., qafla /Ɂɑflɑ/ - afda, /ɑfdɑ/ → [Ɂɑfda], Engl., ‘to trust' - ‘chord') showed no early influence of prosodic cues on segmental processing. But a gating experiment (Experiment 4) replicated the prosodic effect observed in Experiment 2. Taken together, our results indicate an interaction between prosodic processing and segmental processing that comes into effect relatively late in speech processing. |
Jana Annina Müller; Dorothea Wendt; Birger Kollmeier; Stefan Debener; Thomas Brand Effect of speech rate on neural tracking of speech Journal Article In: Frontiers in Psychology, vol. 10, pp. 449, 2019. @article{Mueller2019, Speech comprehension requires effort in demanding listening situations. Selective attention may be required for focusing on a specific talker in a multi-talker environment, may enhance effort by requiring additional cognitive resources, and is known to enhance the neural representation of the attended talker in the listener's neural response. The aim of the study was to investigate the relation of listening effort, as quantified by subjective effort ratings and pupil dilation, and neural speech tracking during sentence recognition. Task demands were varied using sentences with varying levels of linguistic complexity and using two different speech rates in a picture-matching paradigm with 20 normal-hearing listeners. The participants' task was to match the acoustically presented sentence with a picture presented before the acoustic stimulus. Afterwards they rated their perceived effort on a categorical effort scale. During each trial, pupil dilation (as an indicator of listening effort) and electroencephalogram (as an indicator of neural speech tracking) were recorded. Neither measure was significantly affected by linguistic complexity. However, speech rate showed a strong influence on subjectively rated effort, pupil dilation, and neural tracking. The neural tracking analysis revealed a shorter latency for faster sentences, which may reflect a neural adaptation to the rate of the input. No relation was found between neural tracking and listening effort, even though both measures were clearly influenced by speech rate. This is probably due to factors that influence both measures differently. Consequently, the amount of listening effort is not clearly represented in the neural tracking. |
Christian A. Navarro-Torres; Dalia L. Garcia; Vrinda Chidambaram; Judith F. Kroll Cognitive control facilitates attentional disengagement during second language comprehension Journal Article In: Brain Sciences, vol. 9, pp. 1–23, 2019. @article{NavarroTorres2019, Bilinguals learn to resolve conflict between their two languages and that skill has been hypothesized to create long-term adaptive changes in cognitive functioning. Yet, little is known about how bilinguals recruit cognitive control to enable efficient use of one of their languages, especially in the less skilled and more effortful second language (L2). Here we examined how real-time cognitive control engagement influences L2 sentence comprehension (i.e., conflict adaptation). We tested a group of English monolinguals and a group of L2 English speakers using a recently-developed cross-task adaptation paradigm. Stroop sequences were pseudo-randomly interleaved with a visual-world paradigm in which participants were asked to carry out spoken instructions that were either syntactically ambiguous or unambiguous. Consistent with previous research, eye-movement results showed that Stroop-related conflict improved the ability to engage correct-goal interpretations, and disengage incorrect-goal interpretations, during ambiguous instructions. Such cognitive-to-language modulations were similar in both groups, but only in the engagement piece. In the disengagement portion, the modulation emerged earlier in bilinguals than in monolinguals, suggesting group differences in attentional disengagement following cognitive control recruitment. Additionally, incorrect-goal eye-movements were modulated by individual differences in working memory, although differently for each group, suggesting an involvement of both language-specific and domain-general resources. |
Gal Nitsan; Arthur Wingfield; Limor Lavie; Boaz M. Ben-David Differences in working memory capacity affect online spoken word recognition: Evidence from eye movements Journal Article In: Trends in Hearing, vol. 23, 2019. @article{Nitsan2019, Individual differences in working memory capacity have been gaining recognition as playing an important role in speech comprehension, especially in noisy environments. Using the visual world eye-tracking paradigm, a recent study by Hadar and coworkers found that online spoken word recognition was slowed when listeners were required to retain in memory a list of four spoken digits (high load) compared with only one (low load). In the current study, we recognized that the influence of a digit preload might be greater for individuals who have a more limited memory span. We compared participants with higher and lower memory spans on the time course for spoken word recognition by testing eye-fixations on a named object, relative to fixations on an object whose name shared phonology with the named object. Results show that when a low load was imposed, differences in memory span had no effect on the time course of preferential fixations. However, with a high load, listeners with lower span were delayed by $550 ms in discriminating target from sound-sharing competitors, relative to higher span listeners. This follows an assumption that the interference effect of a memory preload is not a fixed value, but rather, its effect is greater for individuals with a smaller memory span. Interestingly, span differences affected the timeline for spoken word recognition in noise, but not offline accuracy. This highlights the significance of using eye-tracking as a measure for online speech processing. Results further emphasize the importance of considering differences in cognitive capacity, even when testing normal hearing young adults. |
Henri Olkoniemi; Eerika Johander; Johanna K. Kaakinen The role of look-backs in the processing of written sarcasm Journal Article In: Memory & Cognition, vol. 47, no. 1, pp. 87–105, 2019. @article{Olkoniemi2019, Previous eye-tracking studies suggest that when resolving the meaning of sarcastic utterances in a text, readers often initiate fixations that return to the sarcastic utterance from subsequent parts of the text. We used a modified trailing mask paradigm to examine both the role of these look-back fixations in sarcasm comprehension and whether there are individual differences in how readers resolve sarcasm. Sixty-two adult participants read short paragraphs containing either a literal or a sarcastic utterance while their eye movements were recorded. The texts were presented using a modified trailing mask paradigm: sentences were initially masked with a string of x's and were revealed to the reader one at a time. In the normal reading condition, sentences remained visible on the screen when the reader moved on to the next sentence; in the masked condition, the sentences were replaced with a mask. Individual differences in working memory capacity (WMC) and the processing of emotional information were also measured. The results showed that readers adjusted their reading behavior when a mask prevented them from re-examining the text content. Interestingly, the readers' compensatory strategies depended on spatial WMC. Moreover, the results showed that the ability to process emotional information was related to less processing effort invested in resolving sarcasm. The present study suggests that look-backs are driven by a need to re-examine the text contents but that they are not necessary for the successful comprehension of sarcasm. The strategies used to resolve sarcasm are mediated by individual differences. |
Henri Olkoniemi; Viivi Strömberg; Johanna K. Kaakinen The ability to recognise emotions predicts the time-course of sarcasm processing: Evidence from eye movements Journal Article In: Quarterly Journal of Experimental Psychology, vol. 72, no. 5, pp. 1212–1223, 2019. @article{Olkoniemi2019a, A core feature of sarcasm is that there is a discrepancy between the literal meaning of the utterance and the context in which it is presented. This means that a sarcastic statement embedded in a story introduces a break in local coherence. Previous studies have shown that sarcastic statements in written stories often elicit longer processing times than their literal counterparts, possibly reflecting the difficulty of integrating the statement into the story's context. In the present study, we examined how sarcastic statements are processed when the location of the local coherence break is manipulated by presenting the sarcastic dialogues either before or after contextual information. In total, 60 participants read short text paragraphs containing sarcastic or literal target statements, while their eye movements were recorded. Individual differences in ability to recognise emotions and working memory capacity were measured. The results suggest that longer reading times with sarcastic statements not only reflect local inconsistency but also attempt to resolve the meaning of the sarcastic statement. The ability to recognise emotions was reflected in eye-movement patterns, suggesting that readers who are poor at recognising emotions are slower at categorising the statement as sarcastic. Thus, they need more processing effort to resolve the sarcastic meaning. |
Akira Omaki; Zoe Ovans; Anthony Yacovone; Brian W. Dillon Rebels without a clause: Processing reflexives in fronted wh-predicates Journal Article In: Journal of Memory and Language, vol. 107, pp. 80–94, 2019. @article{Omaki2019, English reflexives like herself tend to associate with a structurally prominent local antecedent in online processing. However, past work has primarily investigated reflexives in canonical direct object positions. The present study investigates cataphoric reflexives in fronted wh-predicates (e.g., The mechanic that James hired predicted how annoyed with himself the insurance agent would be). Here, the reflexive is encountered in advance of its grammatical antecedent. We ask two questions. First, will readers engage an anaphoric (backwards-looking) or cataphoric (forwards-looking) search for an antecedent? Two, how similar is this process to the retrieval process for direct object reflexives? In two eye-tracking experiments, we found that readers initially interpret a cataphoric reflexive anaphorically, and tend to associate the reflexive with the more recently encountered antecedent. We propose that structural guidance for reflexive resolution occurs only when the necessary configurational syntactic information is available when the reflexive is encountered. |
2018 |
Clarissa Vries; W. Gudrun Reijnierse; Roel M. Willems Eye movements reveal readers' sensitivity to deliberate metaphors during narrative reading Journal Article In: Scientific Study of Literature, vol. 8, no. 1, pp. 135–164, 2018. @article{Vries2018, Metaphors occur frequently in literary texts. Deliberate Metaphor Theory (DMT; e.g., Steen, 2017 ) proposes that metaphors that serve a communicative function as metaphor are radically different from metaphors that do not have this function. We investigated differences in processing between deliberate and non-deliberate metaphors, compared to non-metaphorical words in literary reading. Using the Deliberate Metaphor Identification Procedure ( Reijnierse et al., 2018 ), we identified metaphors in two literary stories. Then, eye-tracking was used to investigate participants' ( N = 72) reading behavior. Deliberate metaphors were read slower than non-deliberate metaphors, and both metaphor types were read slower than non-metaphorical words. Differences were controlled for several psycholinguistic variables. Differences in reading behavior were related to individual differences in reading experience and absorption and appreciation of the story. These results are in line with predictions from DMT and underline the importance of distinguishing between metaphor types in the experimental study of literary reading. |
Jocelyn R. Folk; Michael A. Eskenazi Eye-tracking to distinguish comprehension-based and oculomotor-based regressive eye movements during reading Journal Article In: Journal of Visualized Experiments, no. 140, pp. 1–6, 2018. @article{Folk2018, Regressive eye movements are eye movements that move backwards through the text and comprise approximately 10-25% of eye movements during reading. As such, understanding the causes and mechanisms of regressions plays an important role in understanding eye movement behavior. Inhibition of return (IOR) is an oculomotor effect that results in increased latency to return attention to a previously attended target versus a target that was not previously attended. Thus, IOR may affect regressions. This paper describes how to design materials to distinguish between regressions caused by comprehension-related and oculomotor processes; the latter is subject to IOR. The method allows researchers to identify IOR and control the causes of regressions. While the method requires tightly controlled materials and large numbers of participants and materials, it allows researchers to distinguish and control the types of regressions that occur in their reading studies. |
Hazel I. Blythe; Jonathan H. Dickins; Colin R. Kennedy; Simon P. Liversedge Phonological processing during silent reading in teenagers who are deaf/hard of hearing: An eye movement investigation Journal Article In: Developmental Science, vol. 21, pp. 1–19, 2018. @article{Blythe2018, There has been considerable variability within the literature concerning the extent to which deaf/hard of hearing individuals are able to process phonological codes during reading. Two experiments are reported in which participants' eye movements were recorded as they read sentences containing correctly spelled words (e.g., church), pseudohomophones (e.g., cherch), and spelling controls (e.g., charch). We examined both foveal processing and parafoveal pre‐processing of phonology for three participant groups—teenagers with permanent childhood hearing loss (PCHL), chronological age‐matched controls, and reading age‐matched controls. The teenagers with PCHL showed a pseudohomophone advantage from both directly fixated words and parafoveal preview, similar to their hearing peers. These data provide strong evidence for phonological recoding during silent reading in teenagers with PCHL. |
Ricardo Kienitz; Joscha T. Schmiedt; Katharine A. Shapcott; Kleopatra Kouroupaki; Richard C. Saunders; Michael C. Schmid Theta rhythmic neuronal activity and reaction times arising from cortical receptive field interactions during distributed attention Journal Article In: Current Biology, vol. 28, no. 15, pp. 2377–2387, 2018. @article{Kienitz2018, Growing evidence suggests that distributed spatial attention may invoke theta (3–9 Hz) rhythmic sampling processes. The neuronal basis of such attentional sampling is, however, not fully understood. Here we show using array recordings in visual cortical area V4 of two awake macaques that presenting separate visual stimuli to the excitatory center and suppressive surround of neuronal receptive fields (RFs) elicits rhythmic multi-unit activity (MUA)at 3–6 Hz. This neuronal rhythm did not depend on small fixational eye movements. In the context of a distributed spatial attention task, during which the monkeys detected a spatially and temporally uncertain target, reaction times (RTs) exhibited similar rhythmic fluctuations. RTs were fast or slow depend-ing on the target occurrence during high or low MUA, resulting in rhythmic MUA-RT cross-correlations at theta frequencies. These findings show that theta rhythmic neuronal activity can arise from competitiveRF interactions and that this rhythm may result in rhythmic RTs potentially subserving attentional sampling. |
Tania S. Zamuner; Stephanie Strahm; Elizabeth Morin-Lessard; Michael P. A. Page Reverse production effect: Children recognize novel words better when they are heard rather than produced Journal Article In: Developmental Science, vol. 21, no. 4, pp. 1–13, 2018. @article{Zamuner2018, This research investigates the effect of production on 4.5‐ to 6‐year‐old children's recognition of newly learned words. In Experiment 1, children were taught four novel words in a produced or heard training condition during a brief training phase. In Experiment 2, children were taught eight novel words, and this time training condition was in a blocked design. Immediately after training, children were tested on their recognition of the trained novel words using a preferential looking paradigm. In both experiments, children recognized novel words that were produced and heard during training, but demonstrated better recognition for items that were heard. These findings are opposite to previous results reported in the literature with adults and children. Our results show that benefits of speech production for word learning are dependent on factors such as task complexity and the developmental stage of the learner. |
Signy Wegener; Hua-Chen Wang; Peter Lissa; Serje Robidoux; Kate Nation; Anne Castles Children reading spoken words: Interactions between vocabulary and orthographic expectancy Journal Article In: Developmental Science, vol. 21, no. 3, pp. 1–9, 2018. @article{Wegener2018, There is an established association between children's oral vocabulary and their word reading but its basis is not well understood. Here, we present evidence from eye movements for a novel mechanism underlying this association. Two groups of 18 Grade 4 children received oral vocabulary training on one set of 16 novel words (e.g., ‘nesh', ‘coib'), but no training on another set. The words were assigned spellings that were either predictable from phonology (e.g., nesh) or unpredictable (e.g., koyb). These were subsequently shown in print, embedded in sentences. Reading times were shorter for orally familiar than unfamiliar items, and for words with predictable than unpredictable spellings but, importantly, there was an interaction between the two: children demonstrated a larger benefit of oral familiarity for predictable than for unpredictable items. These findings indicate that children form initial orthographic expectations about spoken words before first seeing them in print. A video abstract of this article can be viewed at: https://youtu.be/jvpJwpKMM3E. |
Joshua D. Cosman; Kaleb A. Lowe; Wolf Zinke; Geoffrey F. Woodman; Jeffrey D. Schall Prefrontal control of visual distraction Journal Article In: Current Biology, vol. 28, no. 3, pp. 414–420, 2018. @article{Cosman2018, Avoiding distraction by conspicuous but irrelevant stimuli is critical to accomplishing daily tasks. Regions of prefrontal cortex control attention by enhancing the representation of task-relevant information in sensory cortex, which can be measured in modulation of both single neurons and event-related electrical potentials (ERPs) on the cranial surface [1, 2]. When irrelevant information is particularly conspicuous, it can distract attention and interfere with the selection of behaviorally relevant information. Such distraction can be minimized via top-down control [3–5], but the cognitive and neural mechanisms giving rise to this control over distraction remain uncertain and debated [6–9]. Bridging neurophysiology to electrophysiology, we simultaneously recorded neurons in prefrontal cortex and ERPs over extrastriate visual cortex to track the processing of salient distractors during a visual search task. Critically, when the salient distractor was successfully ignored, but not otherwise, we observed robust suppression of salient distractor representations. Like target selection, the distractor suppression was observed in prefrontal cortex before it appeared over extrastriate cortical areas. Furthermore, all prefrontal neurons that showed suppression of the task-irrelevant distractor also contributed to selecting the target. This suggests a common prefrontal mechanism is responsible for both selecting task-relevant and suppressing task-irrelevant information in sensory cortex. Taken together, our results resolve a long-standing debate over the mechanisms that prevent distraction, and provide the first evidence directly linking suppressed neural firing in prefrontal cortex with surface ERP measures of distractor suppression. |
Giacomo Benvenuti; Yuzhi Chen; Charu Ramakrishnan; Karl Deisseroth; Wilson S. Geisler; Eyal Seidemann Scale-invariant visual capabilities explained by topographic representations of luminance and texture in primate V1 Journal Article In: Neuron, vol. 100, no. 6, pp. 1504–1512.e4, 2018. @article{Benvenuti2018, Benvenuti et al. describe a novel retinotopic representation of low-spatial-frequency luminance stimuli in V1 of behaving macaques. This distributed representation could solve the “aperture problem” for computation of orientation of low-spatial-frequency stimuli by single V1 neurons. |
Anil Bollimunta; Amarender R. Bogadhi; Richard J. Krauzlis Comparing frontal eye field and superior colliculus contributions to covert spatial attention Journal Article In: Nature Communications, vol. 9, pp. 3553, 2018. @article{Bollimunta2018, The causal roles of the frontal eye fields (FEF) and superior colliculus (SC) in spatial selective attention have not been directly compared. Reversible inactivation is an established method for testing causality but comparing results between FEF and SC is complicated by differences in size and morphology of the two brain regions. Here we exploited the fact that inactivation of FEF and SC also changes the metrics of saccadic eye movements, providing an independent benchmark for the strength of the causal manipulation. Using monkeys trained to covertly perform a visual motion-change detection task, we found that inactivation of either FEF or SC could cause deficits in attention task performance. However, SC-induced attention deficits were found with saccade changes half the size needed to get FEF-induced attention deficits. Thus, performance in visual attention tasks is vulnerable to loss of signals from either structure, but suppression of SC activity has a more devastating effect. |
Yehudit Botschko; Merav Yarkoni; Mati Joshua Smooth pursuit eye movement of monkeys naive to laboratory setups with pictures and artificial stimuli Journal Article In: Frontiers in Systems Neuroscience, vol. 12, pp. 15, 2018. @article{Botschko2018, When animal behavior is studied in a laboratory environment, the animals are often extensively trained to shape their behavior. A crucial question is whether the behavior observed after training is part of the natural repertoire of the animal or represents an outlier in the animal's natural capabilities. This can be investigated by assessing the extent to which the target behavior is manifested during the initial stages of training and the time course of learning. We explored this issue by examining smooth pursuit eye movements in monkeys naïve to smooth pursuit tasks. We recorded the eye movements of monkeys from the first days of training on a step-ramp paradigm. We used bright spots, monkey pictures and scrambled versions of the pictures as moving targets. We found that during the initial stages of training, the pursuit initiation was largest for the monkey pictures and in some direction conditions close to target velocity. When the pursuit initiation was large, the monkeys mostly continued to track the target with smooth pursuit movements while correcting for displacement errors with small saccades. Two weeks of training increased the pursuit eye velocity in all stimulus conditions, whereas further extensive training enhanced pursuit slightly more. The training decreased the coefficient of variation of the eye velocity. Anisotropies that grade pursuit across directions were observed from the first day of training and mostly persisted across training. Thus, smooth pursuit in the step-ramp paradigm appears to be part of the natural repertoire of monkeys' behavior and training adjusts monkeys' natural predisposed behavior. |
Irene Caprara; Peter Janssen; Maria C. Romero Investigating object representations in the macaque dorsal visual stream using single-unit recordings Journal Article In: Journal of Visualized Experiments, no. 138, pp. 1–10, 2018. @article{Caprara2018a, Previous studies have shown that neurons in parieto-frontal areas of the macaque brain can be highly selective for real-world objects, disparity-defined curved surfaces, and images of real-world objects (with and without disparity) in a similar manner as described in the ventral visual stream. In addition, parieto-frontal areas are believed to convert visual object information into appropriate motor outputs, such as the pre-shaping of the hand during grasping. To better characterize object selectivity in the cortical network involved in visuomotor transformations, we provide a battery of tests intended to analyze the visual object selectivity of neurons in parieto-frontal regions. |
Irene Caprara; Elsie Premereur; Maria C. Romero; Pedro Faria; Peter Janssen Shape responses in a macaque frontal area connected to posterior parietal cortex Journal Article In: NeuroImage, vol. 179, pp. 298–312, 2018. @article{Caprara2018, The primate dorsal visual stream processes object shape to guide actions involving an object, but the transmission of shape information beyond posterior parietal cortex remains largely unknown. To clarify the information flow between parietal and frontal cortex, we applied electrical microstimulation during functional Magnetic Resonance Imaging (fMRI) in a shape-selective patch in the posterior part of the Anterior Intraparietal area (pAIP) to chart its connectivity. Subsequently, we recorded single-unit responses to images of objects in the fMRI activation in prefrontal cortex, corresponding to area 45B, elicited by pAIP microstimulation. Neurons in area 45B had properties similar to neurons in pAIP, responding selectively to shape contours and to very small shape fragments measuring less than one deg at exceedingly short latencies. However, contrary to the prevailing view on the hierarchical organization of cortical areas, neurons in area 45B preferred even smaller shape fragments and had smaller receptive fields than neurons in pAIP. These findings provide the first evidence for ultra-fast shape processing in prefrontal cortex, and suggest that the pathway from pAIP to area 45B may not be important for object grasping. |
Chih-Yang Chen; Lukas Sonnenberg; Simone Weller; Thede Witschel; Ziad M. Hafed Spatial frequency sensitivity in macaque midbrain Journal Article In: Nature Communications, vol. 9, pp. 2852, 2018. @article{Chen2018c, Visual brain areas exhibit tuning characteristics well suited for image statistics present in our natural environment. However, visual sensation is an active process, and if there are any brain areas that ought to be particularly in tune with natural scene statistics, it would be sensory-motor areas critical for guiding behavior. Here we found that the rhesus macaque superior colliculus, a structure instrumental for rapid visual exploration with saccades, detects low spatial frequencies, which are the most prevalent in natural scenes, much more rapidly than high spatial frequencies. Importantly, this accelerated detection happens independently of whether a neuron is more or less sensitive to low spatial frequencies to begin with. At the population level, the superior colliculus additionally over-represents low spatial frequencies in neural response sensitivity, even at near-foveal eccentricities. Thus, the superior colliculus possesses both temporal and response gain mechanisms for efficient gaze realignment in low-spatial-frequency-dominated natural environments. |
Hoseok Choi; Seho Lee; Jeyeon Lee; Kyeongran Min; Seokbeen Lim; Jinsick Park; Kyoung-ha Ahn; In Young Kim; Kyoung-Min Lee; Dong Pyo Jang Long-term evaluation and feasibility study of the insulated screw electrode for ECoG recording Journal Article In: Journal of Neuroscience Methods, vol. 308, pp. 261–268, 2018. @article{Choi2018, Background: A screw-shaped electrode can offer a compromise between signal quality and invasiveness. However, the standard screw electrode can be vulnerable to electrical noise while directly contact with the skull or skin, and the feasibility and stability for chronic implantation in primate have not been fully evaluated. New Method: We designed a novel screw electrocorticogram (ECoG) electrode composed of three parts: recording electrode, insulator, and nut. The recording electrode was made of titanium with high biocompatibility and high electrical conductivity. Zirconia is used for insulator and nut to prevent electrical noise. Result: In computer simulations, the screw ECoG with insulator showed a significantly higher performance in signal acquisition compared to the condition without insulator. In a non-human primate, using screw ECoG, clear visual-evoked potential (VEP) waveforms were obtained, VEP components were reliably maintained, and the electrode's impedance was stable during the whole evaluation period. Moreover, it showed higher SNR and wider frequency band compared to the electroencephalogram (EEG). We also observed the screw ECoG has a higher sensitivity that captures different responses on various stimuli than the EEG. Comparison: The screw ECoG showed reliable electrical characteristic and biocompatibility for three months, that shows great promise for chronic implants. These results contrasted with previous reports that general screw electrode was only applicable for acute applications. Conclusion: The suggested electrode can offer whole-brain monitoring with high signal quality and minimal invasiveness. The screw ECoG can be used to provide more in-depth understanding, not only relationship between functional networks and cognitive behavior, but also pathomechanisms in brain diseases. |
Jan Churan; Doris I. Braun; Karl R. Gegenfurtner; Frank Bremmer Comparison of the precision of smooth pursuit in humans and head unrestrained monkeys Journal Article In: Journal of Eye Movement Research, vol. 11, no. 4, pp. 1–15, 2018. @article{Churan2018, Direct comparison of results of humans and monkeys is often complicated by differences in experimental conditions. We replicated in head unrestrained macaques experiments of a recent study comparing human directional precision during smooth pursuit eye movements (SPEM) and saccades to moving targets (Braun & Gegenfurtner, 2016). Directional precision of human SPEM follows an exponential decay function reaching optimal values of 1.5°-3° within 300 ms after target motion onset, whereas precision of initial saccades to moving targets is slightly better. As in humans, we found general agreement in the development of directional precision of SPEM over time and in the differences between directional precision of initial saccades and SPEM initiation. However, monkeys showed overall lower precision in SPEM compared to humans. This was most likely due to differences in experimental conditions, such as in the stabilization of the head, which was by a chin and a head rest in human subjects and unrestrained in monkeys. |
Suryadeep Dash; Tyler R. Peel; Stephen G. Lomber; Brian D. Corneil In: eNeuro, vol. 5, no. 2, pp. 1–16, 2018. @article{Dash2018, A neural correlate for saccadic reaction times (SRTs) in the gap saccade task is the level of low-frequency activity in the intermediate layers of the superior colliculus (iSC) just before visual target onset: greater levels of such preparatory iSC low-frequency activity precede shorter SRTs. The frontal eye fields (FEFs) are one likely source of iSC preparatory activity, since FEF preparatory activity is also inversely related to SRT. To better understand the FEF's role in saccade preparation, and the way in which such preparation relates to SRT, in two male rhesus monkeys, we compared iSC preparatory activity across unilateral reversible cryogenic inactivation of the FEF. FEF inactivation increased contralesional SRTs, and lowered ipsilesional iSC preparatory activity. FEF inactivation also reduced rostral iSC activity during the gap period. Importantly, the distributions of SRTs generated with or without FEF inactivation overlapped, enabling us to conduct a novel population-level analyses examining iSC preparatory activity just before generation of SRT-matched saccades. When matched for SRTs, we observed no change during FEF inactivation in the relationship between iSC preparatory activity and SRT-matched saccades across a range of SRTs, even for the occasional express saccade. Thus, while our results emphasize that the FEF has an overall excitatory influence on preparatory activity in the iSC, the communication between the iSC and downstream oculomotor brainstem is unaltered for SRT-matched saccades. |
Mohammad-Reza A. Dehaqani; Abdol-Hossein Vahabie; Mohammadbagher Parsa; Behrad Noudoost; Alireza Soltani Selective changes in noise correlations contribute to an enhanced representation of saccadic targets in prefrontal neuronal ensembles Journal Article In: Cerebral Cortex, vol. 28, no. 8, pp. 3046–3063, 2018. @article{Dehaqani2018, An ensemble of neurons can provide a dynamic representation of external stimuli, ongoing processes, or upcoming actions. This dynamic representation could be achieved by changes in the activity of individual neurons and/or their interactions. To investigate these possibilities, we simultaneously recorded from ensembles of prefrontal neurons in non-human primates during a memory-guided saccade task. Using both decoding and encoding methods, we examined changes in the information content of individual neurons and that of ensembles between visual encoding and saccadic target selection. We found that individual neurons maintained their limited spatial sensitivity between these cognitive states, whereas the ensemble selectively improved its encoding of spatial locations far from the neurons' preferred locations. This population- level “encoding expansion” was not due to the ceiling effect at the preferred locations and was accompanied by selective changes in noise correlations for non-preferred locations. Moreover, the encoding expansion was observed for ensembles of different types of neurons and could not be explained by shifts in the preferred location of individual neurons. Our results demonstrate that the representation of space by neuronal ensembles is dynamically enhanced prior to saccades, and this enhancement occurs alongside changes in noise correlations more than changes in the activity of individual neurons. |
R. Becket Ebitz; Eddy Albarran; Tirin Moore Exploration disrupts choice-predictive signals and alters dynamics in prefrontal cortex Journal Article In: Neuron, vol. 97, no. 2, pp. 450–461.e9, 2018. @article{Ebitz2018, In uncertain environments, decision-makers must balance two goals: they must “exploit” rewarding options but also “explore” in order to discover rewarding alternatives. Exploring and exploiting necessarily change how the brain responds to identical stimuli, but little is known about how these states, and transitions between them, change how the brain transforms sensory information into action. To address this question, we recorded neural activity in a prefrontal sensorimotor area while monkeys naturally switched between exploring and exploiting rewarding options. We found that exploration profoundly reduced spatially selective, choice-predictive activity in single neurons and delayed choice-predictive population dynamics. At the same time, reward learning was increased in brain and behavior. These results indicate that exploration is related to sudden disruptions in prefrontal sensorimotor control and rapid, reward-dependent reorganization of control dynamics. This may facilitate discovery through trial and error. Exploratory choices permit the discovery of new rewarding options. Ebitz et al. report that spatially selective, choice-predictive neurons in the prefrontal cortex do not predict choice before exploratory decisions. Reduced prefrontal control may underlie flexible decision-making and trial-and-error discovery. |
Shiva Farashahi; Habiba Azab; Benjamin Y. Hayden; Alireza Soltani On the flexibility of basic risk attitudes in monkeys Journal Article In: Journal of Neuroscience, vol. 38, no. 18, pp. 4383–4398, 2018. @article{Farashahi2018, Monkeys and other animals appear to share with humans two risk attitudes predicted by prospect theory: an inverse-S-shaped probability weighting function and a steeper utility curve for losses than for gains. These findings suggest that such preferences are stable traits with common neural substrates. We hypothesized instead that animals tailor their preferences to subtle changes in task contexts, making risk attitudes flexible. Previous studies used a limited number of outcomes, trial types, and contexts. To gain a broader perspective, we examined two large datasets of male macaques' risky choices: one from a task with real (juice) gains and another from a token task with gains and losses. In contrast to previous findings, monkeys were risk-seeking for both gains and losses (i.e. lacked a reflection effect) and showed steeper gain than loss curves (loss-seeking). Utility curves for gains were substantially different in the two tasks. Monkeys showed nearly linear probability weightings in one task and S-shaped ones in the other; neither task produced a consistent inverse-S-shaped curve. To account for these observations, we developed and tested various computational models of the processes involved in the construction of reward value. We found that adaptive differential weighting of prospective gamble outcomes could partially account for the observed differences in the utility functions across the two experiments and thus, provide a plausible mechanism underlying flexible risk attitudes. Together, our results support the idea that risky choices are constructed flexibly at the time of elicitation and place important constraints on neural models of economic choice. |
Jose A. Fernandez-Leon; Bryan J. Hansen; Valentin Dragoi Representation of rapid image sequences in V4 Networks Journal Article In: Cerebral Cortex, vol. 28, no. 8, pp. 2675–2684, 2018. @article{FernandezLeon2018, Natural viewing often consists of sequences of brief fixations to image patches of different structure. Whether and how briefly presented sequential stimuli are encoded in a temporal-position manner is poorly understood. Here, we performed multiple-electrode recordings in the visual cortex (area V4) of nonhuman primates (Macaca mulatta) viewing a sequence of 7 briefly flashed natural images, and measured correlations between the cue-triggered population response in the presence and absence of the stimulus. Surprisingly, we found significant correlations for images occurring at the beginning and the end of a sequence, but not for those in the middle. The correlation strength increased with stimulus exposure and favored the image position in the sequence rather than image identity. These results challenge the commonly held view that images are represented in visual cortex exclusively based on their informational content, and indicate that, in the absence of sensory information, neuronal populations exhibit reactivation of stimulus-evoked responses in a way that reflects temporal position within a stimulus sequence. |
Ian C. Fiebelkorn; Mark A. Pinsk; Sabine Kastner A dynamic interplay within the frontoparietal network underlies rhythmic spatial attention Journal Article In: Neuron, vol. 99, no. 4, pp. 842–853.e8, 2018. @article{Fiebelkorn2018, Classic studies of spatial attention assumed that its neural and behavioral effects were continuous over time. Recent behavioral studies have instead revealed that spatial attention leads to alternating periods of heightened or diminished perceptual sensitivity. Yet, the neural basis of these rhythmic fluctuations has remained largely unknown. We show that a dynamic interplay within the macaque frontoparietal network accounts for the rhythmic properties of spatial attention. Neural oscillations characterize functional interactions between the frontal eye fields (FEF) and the lateral intraparietal area (LIP), with theta phase (3–8 Hz) coordinating two rhythmically alternating states. The first is defined by FEF-dominated beta-band activity, associated with suppressed attentional shifts, and LIP-dominated gamma-band activity, associated with enhanced visual processing and better behavioral performance. The second is defined by LIP-specific alpha-band activity, associated with attenuated visual processing and worse behavioral performance. Our findings reveal how network-level interactions organize environmental sampling into rhythmic cycles. Fiebelkorn et al. use simultaneous recordings in two hubs of the macaque frontoparietal network to demonstrate a neural basis of rhythmic sampling during spatial attention. Theta-organized, alternating attentional states, characterized by different spatiotemporal dynamics, shape environmental sampling. |
Whitney S. Griggs; Hidetoshi Amita; Atul Gopal; Okihide Hikosaka Visual neurons in the superior colliculus discriminate many objects by their historical values Journal Article In: Frontiers in Neuroscience, vol. 12, pp. 396, 2018. @article{Griggs2018, The superior colliculus (SC) is an important structure in the mammalian brain that orients the animal towards distinct visual events. Visually-responsive neurons in SC are modulated by visual object features, including size, motion, and color. However, it remains unclear whether SC activity is modulated by non-visual object features, such as the reward value associated with the object. To address this question, three monkeys were trained (>10 days) to saccade to multiple fractal objects, half of which were consistently associated with large reward while other half were associated with small reward. This created historically high-valued (‘good') and low-valued (‘bad') objects. During the neuronal recordings from the SC, the monkeys maintained fixation at the center while the objects were flashed in the receptive field of the neuron without any reward. We found that approximately half of the visual neurons responded more strongly to the good than bad objects. In some neurons, this value-coding remained intact for a long time (>1 year) after the last object-reward association learning. Notably, the neuronal discrimination of reward values started about 100 ms after the appearance of visual objects and lasted for more than 100 ms. These results provide evidence that SC neurons can discriminate objects by their historical (long-term) values. This object value information may be provided by the basal ganglia, especially the circuit originating from the tail of the caudate nucleus. The information may be used by the neural circuits inside SC for motor (saccade) output or may be sent to the circuits outside SC for future behavior. |
Marcel Jan Haan; Thomas Brochier; Sonja Grün; Alexa Riehle; Frédéric V. Barthélemy Real-time visuomotor behavior and electrophysiology recording setup for use with humans and monkeys Journal Article In: Journal of Neurophysiology, vol. 120, no. 2, pp. 539–552, 2018. @article{Haan2018a, Large-scale network dynamics in multiple visuomotor areas is of great interest in the study of eye-hand coordination in both human and monkey. To explore this, it is essential to develop a setup that allows for precise tracking of eye and hand movements. It is desirable that it is able to generate mechanical or visual perturbations of hand trajec- tories so that eye-hand coordination can be studied in a variety of conditions. There are simple solutions that satisfy these requirements for hand movements performed in the horizontal plane while visual stimuli and hand feedback are presented in the vertical plane. How- ever, this spatial dissociation requires cognitive rules for eye-hand coordination different from eye-hand movements performed in the same space, as is the case in most natural conditions. Here we present an innovative solution for the precise tracking of eye and hand movements in a single reference frame. Importantly, our solution allows behavioral explorations under normal and perturbed conditions in both humans and monkeys. It is based on the integration of two noninvasive commercially available systems to achieve online control and synchronous recording of eye (EyeLink) and hand (KINARM) positions during interactive visuomotor tasks. We also present an eye calibration method compatible with different eye trackers that com- pensates for nonlinearities caused by the system's geometry. Our setup monitors the two effectors in real time with high spatial and temporal resolution and simultaneously outputs behavioral and neu- ronal data to an external data acquisition system using a common data format. |
Christopher K. Hauser; Dantong Zhu; Terrence R. Stanford; Emilio Salinas Motor selection dynamics in FEF explain the reaction time variance of saccades to single targets Journal Article In: eLife, vol. 7, pp. 1–32, 2018. @article{Hauser2018, In studies of voluntary movement, a most elemental quantity is the reaction time (RT) between the onset of a visual stimulus and a saccade toward it. However, this RT demonstrates extremely high variability which, in spite of extensive research, remains unexplained. It is well established that, when a visual target appears, oculomotor activity gradually builds up until a critical level is reached, at which point a saccade is triggered. Here, based on computational work and single-neuron recordings from monkey frontal eye field (FEF), we show that this rise-to-threshold process starts from a dynamic initial state that already contains other incipient, internally driven motor plans, which compete with the target-driven activity to varying degrees. The ensuing conflict resolution process, which manifests in subtle covariations between baseline activity, build-up rate, and threshold, consists of fundamentally deterministic interactions, and explains the observed RT distributions while invoking only a small amount of intrinsic randomness.As we examine the space around us our eyes move in short steps, looking toward a new location about four times a second. Neurons in a region of the brain called the frontal eye field help initiate these eye movements, which are known as saccades. Each neuron contributes to a saccade with a specific direction and size. Before a saccade, the relevant neurons in the frontal eye field steadily increase their activity. When this activity reaches a critical threshold, the visual system issues a command to move the eyes in the appropriate direction. So a saccade that moves the eyes to the right requires a specific group of neurons to be strongly activated – but, at the same time, the neurons responsible for movement to the left need to be less active.Imagine that you have to move your eyes as quickly as possible to look at a spot of light that appears on a screen. Some of the time your eyes will start to move about 100 milliseconds after the light appears. But on other attempts, your eyes will not start moving until 300 milliseconds after the light came on. What causes this variability?To find out, Hauser et al. recorded from neurons in monkeys trained to perform such a task. When the spot of light appeared many different neurons were active, suggesting there is conflict between the plan that would move the eyes toward the target and plans to look at other locations. That is, when the target appears, the monkey is already thinking of looking somewhere. The time required to resolve this conflict depends on how far apart the target and the competing locations are from one another, and on how much the competing neurons have increased their activity before the target appears.Similar mechanisms are likely to operate when we sit at the dinner table and look for the salt shaker, for example, and so the results presented by Hauser et al. will help us to understand how we direct our attention to different points in space. Understanding how these processes work in more detail will help us to discern what happens when they go wrong, as occurs in attention deficit disorders like ADHD. |
Masato Inoue; Shigeru Kitazawa Motor error in parietal area 5 and target error in area 7 drive distinctive adaptation in reaching Journal Article In: Current Biology, vol. 28, pp. 2250–2262, 2018. @article{Inoue2018, Errors in reaching drive trial-by-trial adaptation to compensate for the error. Parietal association areas are implicated in error coding, but whether the parietal error signals directly drive adaptation remains unknown. We first examined the activity of neurons in areas 5 and 7 while two monkeys performed rapid target reaching to clarify whether and how the parietal error signals drive adaptation in reaching. We introduced random errors using a motor-driven prism device to augment random motor errors in reaching. Neurons in both regions encoded information on the target position prior to reaching and information on the motor error after reaching. However, post-movement microstimulation caused trial-by-trial adaptation to cancel the motor error only when it was delivered to area 5. By contrast, stimulation to area 7 caused trial-by-trial adaptation so that the reaching endpoint was adjusted toward the target position. We further hypothesized that area 7 would encode target error that is caused by a target jump during the reach, and our results support this hypothesis. Area 7 neurons encoded target error information, but area 5 neurons did not encode this information. These results suggest that area 5 provides signals for adapting to motor errors and that area 7 provides signals to adapt to target errors. |
Kevin D. Johnston; Kevin Barker; David J. Schaeffer; Lauren Schaeffer; Stefan Everling Methods for chair restraint and training of the common marmoset on oculomotor tasks Journal Article In: Journal of Neurophysiology, vol. 119, no. 5, pp. 1636–1646, 2018. @article{Johnston2018, The oculomotor system is the most thoroughly understood sensorimotor system in the brain, due in large part to electrophysiological studies carried out in macaque monkeys trained to perform oculomotor tasks. A disadvantage of the macaque model is that many cortical oculomotor areas of interest lie within sulci, making high-density array and laminar recordings impractical. Many techniques of molecular biology developed in rodents, such as optogenetic manipulation of neuronal subtypes, are also limited in this species. The common marmoset (Callithrix jacchus) possesses a smooth cortex, allowing easy access to frontoparietal oculomotor areas, and may bridge the gap between systems neuroscience in macaques and molecular techniques. Techniques for restraint, training, and neural recording in these animals have been well developed in auditory neuroscience. Those for oculomotor neuroscience, however, remain at a relatively early stage. In this article we provide details of a custom-designed restraint chair for marmosets, a combination head restraint/recording chamber allowing access to cortical oculomotor areas and providing stability suitable for eye movement and neural recordings, as well as a training protocol for oculomotor tasks. We additionally report the results of a psychophysical study in marmosets trained to perform a saccade task using these methods, showing that, as in rhesus and humans, marmosets exhibit a “gap effect,” a decrease in reaction time when the fixation stimulus is removed before the onset of a visual saccade target. These results are the first evidence of this effect in marmosets and support the common marmoset model for neurophysiological investigations of oculomotor control. |
Peter Kaposvari; Susheel Kumar; Rufin Vogels Statistical learning signals in macaque inferior temporal cortex Journal Article In: Cerebral Cortex, vol. 28, no. 1, pp. 250–266, 2018. @article{Kaposvari2018, Humans are sensitive to statistical regularities in their visual environment, but the nature of the underlying neural statistical learning signals still remains to be clarified. As in human behavioral and neuroimaging studies of statistical learning, we exposed rhesus monkeys to a continuous stream of images, presented without interstimulus interval or reward association. The stimulus set consisted of 3 groups of 5 images each (quintets). The stimulus order within each quintet was fixed, but the quintets were presented repeatedly in a random order without interruption. Thus, only transitional probabilities defined quintets of images. Postexposure recordings in inferior temporal (IT) cortex showed an enhanced response to stimuli that violated the exposed sequence. This enhancement was found only for stimuli that were not predicted by the just preceding stimulus, reflecting a temporally adjacent stimulus relationship, and was sensitive to stimulus order. By comparing IT responses with sequences with and without statistical regularities, we observed a short latency, transient response suppression for stimuli of the sequence with regularities, in addition to a later sustained response enhancement to stimuli that violated the sequence with regularities. These findings constrain models of mechanisms underlying neural responses in predictable temporal sequences, such as predictive coding. |
Katsuhisa Kawaguchi; Stephane Clery; Paria Pourriahi; Lenka Seillier; Ralf M. Haefner; Hendrikje Nienborg Differentiating between models of perceptual decision making using pupil size inferred confidence Journal Article In: Journal of Neuroscience, vol. 38, no. 41, pp. 8874–8888, 2018. @article{Kawaguchi2018, During perceptual decisions, subjects often rely more strongly on early, rather than late, sensory evidence, even in tasks when both are equally informative about the correct decision. This early psychophysical weighting has been explained by an integration-to-bound decision process, in which the stimulus is ignored after the accumulated evidence reaches a certain bound, or confidence level. Here, we derive predictions about how the average temporal weighting of the evidence depends on a subject's decision confidence in this model. To test these predictions empirically, we devised a method to infer decision confidence from pupil size in 2 male monkeys performing a disparity discrimination task. Our animals' data confirmed the integration-to-bound predictions, with different internal decision bounds and different levels of correlation between pupil size and decision confidence accounting for differences between animals. However, the data were less compatible with two alternative accounts for early psychophysical weighting: attractor dynamics either within the decision area or due to feedback to sensory areas, or a feedforward account due to neuronal response adaptation. This approach also opens the door to using confidence more broadly when studying the neural basis of decision making. |
Jonas Knöll; Jonathan W. Pillow; Alexander C. Huk Lawful tracking of visual motion in humans, macaques, and marmosets in a naturalistic, continuous, and untrained behavioral context Journal Article In: Proceedings of the National Academy of Sciences, vol. 115, no. 44, pp. E10486–E10494, 2018. @article{Knoell2018, Much study of the visual system has focused on how humans and monkeys integrate moving stimuli over space and time. Such assessments of spatiotemporal integration provide fundamental grounding for the interpretation of neurophysiological data, as well as how the resulting neural signals support perceptual deci- sions and behavior. However, the insights supported by classical characterizations of integration performed in humans and rhesus monkeys are potentially limited with respect to both generality and detail: Standard tasks require extensive amounts of training, involve abstract stimulus–response mappings, and depend on combining data across many trials and/or sessions. It is thus of concern that the integration observed in classical tasks involves the recruitment of brain circuits that might not normally subsume natural behaviors, and that quantitative analyses have limited power for characterizing single-trial or single-session processes. Here we bridge these gaps by showing that three primate species (humans, macaques, and marmosets) track the focus of expansion of an optic flow field continuously and without substantial training. This flow-tracking behavior was volitional and reflected substantial temporal integration. Most strikingly, gaze patterns exhibited lawful and nuanced dependencies on random perturbations in the stimulus, such that repetitions of identical flow movies elicited remarkably similar eye movements over long and continuous time periods. These results demonstrate the generality of spatiotemporal integration in natural vision, and offer a means for studying integration outside of artificial tasks while maintaining lawful and highly reliable behavior. |
Seng Bum Michael Yoo; Brianna J. Sleezer; Benjamin Y. Hayden Robust encoding of spatial information in orbitofrontal cortex and striatum Journal Article In: Journal of Cognitive Neuroscience, vol. 30, no. 6, pp. 898–913, 2018. @article{Yoo2018, Knowing whether core reward regions carry information about the positions of relevant objects is crucial for adjudicating between choice models. One limitation of previous studies, including our own, is that spatial positions can be consistently differentially associated with rewards, and thus position can be confounded with attention, motor plans, or target identity. We circumvented these problems by using a task in which value— and thus choices—was determined solely by a frequently changing rule, which was randomized relative to spatial position on each trial. We presented offers asynchronously, which allowed us to control for reward expectation, spatial attention, and motor plans in our analyses. We find robust encoding of the spatial position of both offers and choices in two core reward regions, orbitofrontal Area 13 and ventral striatum, as well as in dorsal striatum of macaques. The trial-by-trial correlation in noise in encoding of position was associated with variation in choice, an effect known as choice probability correlation, suggesting that the spatial encoding is associated with choice and is not incidental to it. Spatial information and reward information are not carried by separate sets of neurons, although the two forms of information are temporally dissociable. These results highlight the ubiquity of multiplexed information in association cortex and argue against the idea that these ostensible reward regions serve as part of a pure value domain. |
Tao Yao; Stefan Treue; B. Suresh Krishna Saccade-synchronized rapid attention shifts in macaque visual cortical area MT Journal Article In: Nature Communications, vol. 9, pp. 958, 2018. @article{Yao2018, While making saccadic eye-movements to scan a visual scene, humans and monkeys are able to keep track of relevant visual stimuli by maintaining spatial attention on them. This ability requires a shift of attentional modulation from the neuronal population representing the relevant stimulus pre-saccadically to the one representing it post-saccadically. For optimal performance, this trans-saccadic attention shift should be rapid and saccade-synchronized. Whether this is so is not known. We trained two rhesus monkeys to make saccades while maintaining covert attention at a fixed spatial location. We show that the trans-saccadic attention shift in cortical visual medial temporal (MT) area is well synchronized to saccades. Attentional modulation crosses over from the pre-saccadic to the post-saccadic neuronal representation by about 50 ms after a saccade. Taking response latency into account, the trans-saccadic attention shift is well timed to maintain spatial attention on relevant stimuli, so that they can be optimally tracked and processed across saccades. |
Sheng-Tao Yang; Min Wang; Constantinos D. Paspalas; Johanna L. Crimins; Marcus T. Altman; James A. Mazer; Amy F. T. Arnsten Core differences in synaptic signaling between primary visual and dorsolateral prefrontal cortex Journal Article In: Cerebral Cortex, vol. 28, no. 4, pp. 1458–1471, 2018. @article{Yang2018, Neurons in primary visual cortex (V1) are more resilient than those in dorsolateral prefrontal cortex (dlPFC) in aging, schizophrenia and Alzheimer's disease. The current study compared glutamate and neuromodulatory actions in macaque V1 to those in dlPFC, and found striking regional differences. V1 neuronal firing to visual stimuli depended on AMPA receptors, with subtle NMDA receptor contributions, while dlPFC depends primarily on NMDA receptors. Neuromodulatory actions also differed between regions. In V1, cAMP signaling increased neuronal firing, and the phosphodiesterase PDE4A was positioned to regulate cAMP effects on glutamate release from axons. HCN channels in V1 were classically located on distal dendrites, and enhanced cell firing. These data contrast with dlPFC, where PDE4A and HCN channels are concentrated in thin spines, and cAMP-HCN signaling gates inputs and weakens firing. These regional differences may explain why V1 neurons are more resilient than dlPFC neurons to the challenges of age and disease. |
Yang Xie; Chechang Nie; Tianming Yang Covert shift of attention modulates the value encoding in the orbitofrontal cortex Journal Article In: eLife, vol. 7, pp. 1–21, 2018. @article{Xie2018, During value-based decision making, we often evaluate the value of each option sequentially by shifting our attention, even when the options are presented simultaneously. The orbitofrontal cortex (OFC) has been suggested to encode value during value-based decision making. Yet it is not known how its activity is modulated by attention shifts. We investigated this question by employing a passive viewing task that allowed us to disentangle effects of attention, value, choice and eye movement. We found that the attention modulated OFC activity through a winner-take-all mechanism. When we attracted the monkeys' attention covertly, the OFC neuronal activity reflected the reward value of the newly attended cue. The shift of attention could be explained by a normalization model. Our results strongly argue for the hypothesis that the OFC neuronal activity represents the value of the attended item. They provide important insights toward understanding the OFC's role in value-based decision making. |
Hannah Weinberg-Wolf; Nicholas A. Fagan; George M. Anderson; Marios Tringides; Olga Dal Monte; Steve W. C. Chang The effects of 5-hydroxytryptophan on attention and central serotonin neurochemistry in the rhesus macaque Journal Article In: Neuropsychopharmacology, vol. 43, no. 7, pp. 1589–1594, 2018. @article{WeinbergWolf2018, Psychiatric disorders, particularly depression and anxiety, are often associated with impaired serotonergic function. However, serotonergic interventions yield inconsistent effects on behavioral impairments. To better understand serotonin's role in these pathologies, we investigated the role of serotonin in a behavior frequently impaired in depression and anxiety, attention. In this study, we used a quantitative, repeated, within-subject, design to test how L-5-hydroxytryptophan (5-HTP), the immediate serotonin precursor, modulates central serotoninergic function and attention in macaques. We observed that intramuscular 5-HTP administration increased cisternal cerebrospinal fluid (CSF) 5-HTP and serotonin. In addition, individuals' baseline looking duration, during saline sessions, predicted the direction and magnitude in which 5-HTP modulated attention. We found that 5-HTP decreased looking duration in animals with high baseline attention, but increased looking duration in low baseline attention animals. Furthermore, individual differences in 5-HTP's effects were also reflected in how engaged individuals were in the task and how they allocated attention to salient facial features - the eyes and mouth - of stimulus animals. However, 5-HTP constricted pupil size in all animals, suggesting that the bi-directional effects of 5-HTP cannot be explained by serotonin-mediated changes in autonomic arousal. Critically, high and low baseline attention animals exhibited different baseline CSF concentrations of 5-HTP and serotonin, an index of extracellular functionally active serotonin. Thus, our results suggest that baseline central serotonergic functioning may underlie and predict variation in serotonin's effects on cognitive operation. Our findings may help inform serotonin's role in psychopathology and help clinicians predict how serotonergic interventions will influence pathologies. |
Jing Wang; Devika Narain; Eghbal A. Hosseini; Mehrdad Jazayeri Flexible timing by temporal scaling of cortical responses Journal Article In: Nature Neuroscience, vol. 21, no. 1, pp. 102–112, 2018. @article{Wang2018, Musicians can perform at different tempos, speakers can control the cadence of their speech, and children can flexibly vary their temporal expectations of events. To understand the neural basis of such flexibility, we recorded from the medial frontal cortex of nonhuman primates trained to produce different time intervals with different effectors. Neural responses were heterogeneous, nonlinear, and complex, and they exhibited a remarkable form of temporal invariance: firing rate profiles were temporally scaled to match the produced intervals. Recording from downstream neurons in the caudate and from thalamic neurons projecting to the medial frontal cortex indicated that this phenomenon originates within cortical networks. Recurrent neural network models trained to perform the task revealed that temporal scaling emerges from nonlinearities in the network and that the degree of scaling is controlled by the strength of external input. These findings demonstrate a simple and general mechanism for conferring temporal flexibility upon sensorimotor and cognitive functions. |
Yin Yan; Li Zhaoping; Wu Li Bottom-up saliency and top-down learning in the primary visual cortex of monkeys Journal Article In: Proceedings of the National Academy of Sciences, vol. 115, no. 41, pp. 10499–10504, 2018. @article{Yan2018a, Early sensory cortex is better known for representing sensory inputs but less for the effect of its responses on behavior. Here we explore the behavioral correlates of neuronal responses in primary visual cortex (V1) in a task to detect a uniquely oriented bar-the orientation singleton-in a background of uniformly oriented bars. This singleton is salient or inconspicuous when the orientation contrast between the singleton and background bars is sufficiently large or small, respectively. Using implanted microelectrodes, we measured V1 activities while monkeys were trained to quickly saccade to the singleton. A neuron's responses to the singleton within its receptive field had an early and a late component, both increased with the orientation contrast. The early component started from the outset of neuronal responses; it remained unchanged before and after training on the singleton detection. The late component started ∼40 ms after the early one; it emerged and evolved with practicing the detection task. Training increased the behavioral accuracy and speed of singleton detection and increased the amount of information in the late response component about a singleton's presence or absence. Furthermore, for a given singleton, faster detection performance was associated with higher V1 responses; training increased this be-havioral-neural correlate in the early V1 responses but decreased it in the late V1 responses. Therefore, V1's early responses are directly linked with behavior and represent the bottom-up saliency signals. Learning strengthens this link, likely serving as the basis for making the detection task more reflexive and less top-down driven. |
Andreas Wutz; Roman Loonis; Jefferson E. Roy; Jacob A. Donoghue; Earl K. Miller Different levels of category abstraction by different dynamics in different prefrontal areas Journal Article In: Neuron, vol. 97, no. 3, pp. 716–726.e8, 2018. @article{Wutz2018, Categories can be grouped by shared sensory attributes (i.e., cats) or a more abstract rule (i.e., animals). We explored the neural basis of abstraction by recording from multi-electrode arrays in prefrontal cortex (PFC) while monkeys performed a dot-pattern categorization task. Category abstraction was varied by the degree of exemplar distortion from the prototype pattern. Different dynamics in different PFC regions processed different levels of category abstraction. Bottom-up dynamics (stimulus-locked gamma power and spiking) in the ventral PFC processed more low-level abstractions, whereas top-down dynamics (beta power and beta spike-LFP coherence) in the dorsal PFC processed more high-level abstractions. Our results suggest a two-stage, rhythm-based model for abstracting categories. Wutz et al. show that different levels of category abstraction engage different oscillatory dynamics in different prefrontal cortex (PFC) areas. This suggests a functional specialization within PFC for low-level, stimulus-based categories (e.g., cats) and high-level, rule-based categories (e.g., animals). |
Adrian Staub; Francesca Foppolo; Caterina Donati; Carlo Cecchetto Relative clause avoidance: Evidence for a structural parsing principle Journal Article In: Journal of Memory and Language, vol. 98, pp. 26–44, 2018. @article{Staub2018, Three eye movement experiments investigated the processing of the syntactic ambiguity in strings such as the information that the health department provided, where the that-clause can be either a relative clause (RC) or the start of a nominal complement clause (CC; the information that the health department provided a cure). The experiments tested the prediction that comprehenders should avoid the RC analysis because it involves an unforced filler-gap dependency. Readers showed difficulty upon disambiguation toward the RC analysis, and showed facilitated processing of the ambiguous material itself when the CC analysis was available; both patterns suggest rapid initial adoption of the CC analysis in preference to the RC analysis. The strength of the bias of a specific head noun (e.g., information) to appear with a CC did not modulate these effects, nor were these effects reliably modulated by the tendency of an ambiguous string to be completed off-line as a CC or an RC. These results add to the evidence that structural principles guide the processing of filler-gap dependencies. |
Andrew J. Stewart; Elizabeth Le-Luan; Jeffrey S. Wood; Bo Yao; Matthew Haigh Comprehension of indirect requests is influenced by their degree of imposition Journal Article In: Discourse Processes, vol. 55, no. 2, pp. 187–196, 2018. @article{Stewart2018a, In everyday conversation much communication is achieved using indirect language. This is particularly true when we utter requests. The decision to use indirect language is influenced by a number of factors, including deniability, politeness, and the degree of imposition on the receiver of a request. In this article we report the results of an eye-tracking experiment examining the influence on reading of the degree of imposition of a request. We manipulate whether context describes a situation in which the level of imposition on the receiver of the request is high (which thus motivates the use of indirect language) with one in which the level of imposition is low (and thus does not motivate the use of indirect language). We compare the comprehension of statements that are phrased indirectly with the comprehension of statements that are phrased more directly. We find that statements phrased indirectly are read more quickly in contexts where the level of imposition on the receiver is high versus when the level of imposition is low. In contrast, we find the processing of statements phrased directly does not vary as a function of level of imposition. This indicates that readers use pragmatic knowledge to guide interpretation of indirect requests. Our data provide an insight into the interface between pragmatic and semantic processing. |
Andrew J. Stewart; Jeffrey S. Wood; Elizabeth Le-Luan; Bo Yao; Matthew Haigh 'It's hard to write a good article': The online comprehension of excuses as indirect replies Journal Article In: Quarterly Journal of Experimental Psychology, vol. 71, no. 6, pp. 1265–1269, 2018. @article{Stewart2018, In an eye-tracking experiment, we examined how readers comprehend indirect replies when they are uttered in reply to a direct question. Participants read vignettes that described two characters engaged in dialogue. Each dialogue contained a direct question (e.g., How are you doing in Chemistry?) answered with an excuse (e.g., The exams are not fair). In response to direct questions, such indirect replies are typically used to avoid a face-threatening disclosure (e.g., doing badly on the Chemistry course). Our goal was to determine whether readers are sensitive during reading to the indirect meaning communicated by such replies. Of the three contexts we examined, the first described a negative, face-threatening situation and the second a positive, non-face threatening situation, while the third was neutral. Analysis of reading times to the replies provides strong evidence that readers are sensitive online to the face-saving function of indirect replies. |
Ekaterina Stupina; Andriy Myachykov; Yury Y. Shtyrov Automatic lexical access in visual modality: Eye-tracking evidence Journal Article In: Frontiers in Psychology, vol. 9, pp. 1847, 2018. @article{Stupina2018, Language processing has been suggested to be partially automatic, with some studies suggesting full automaticity and attention-independence of at least early neural stages of language comprehension, in particular, lexical access. Existing neurophysiological evidence has demonstrated early lexically-specific brain responses (enhanced activation for real words) to orthographic stimuli presented parafoveally even under the condition of withdrawn attention. These studies, however, did not control participants' eye movements leaving a possibility that they may have foveated the stimuli, leading to overt processing. To address this caveat, we recorded eye movements to words, pseudowords, and non-words presented parafoveally for a short duration while participants performed a dual non-linguistic feature detection task (color combination) foveally, in the focus of their visual attention. Our results revealed very few saccades to the orthographic stimuli or even to their previous locations. However, analysis of post-experimental recall and recognition performance showed above-chance memory performance for the linguistic stimuli. These results suggest that partial lexical access may indeed take place in the presence of an unrelated demanding task and in the absence of overt attention to the linguistic stimuli. As such, our data further inform automatic and largely attention-independent theories of lexical access. |
Patrick Sturt; Nayoung Kwon Processing information during regressions: An application of the reverse boundary-change paradigm Journal Article In: Frontiers in Psychology, vol. 9, pp. 1630, 2018. @article{Sturt2018, Although 10-15% of eye-movements during reading are regressions, we still know little about the information that is processed during regressive episodes. Here, we report an eye-movement study that uses what we call the reverse boundary change technique to examine the processing of lexical-semantic information during regressions, and to establish the role of this information during recovery from processing difficulty. In the critical condition of the experiment, an initially implausible sentence (e.g., There was an old house that John had ridden when he was a boy) was rendered plausible by changing a context word (house) to a lexical neighbor (horse) using a gaze-contingent display change, at the point where the reader's gaze crossed an invisible boundary further on in the sentence. Due to the initial implausibility of the sentence, readers often launched regressions from the later part of the sentence. However, despite this initial processing difficulty, reading was facilitated, relative to a condition where the display change did not occur (i.e., the word house remained on screen throughout the trial). This result implies that the relevant lexical semantic information was processed during the regression, and was used to aid recovery from the initial processing difficulty. |
Katja Suckow; Roger P. G. Gompel Number attraction affects reanalysis in sentence processing Journal Article In: Language, Cognition and Neuroscience, vol. 33, no. 1, pp. 1–11, 2018. @article{Suckow2018, Many studies have shown evidence for number attraction effects in production. Recent cross-linguistic findings suggest that number attraction can also affect comprehension of ungrammatical sentences. We present an eye-tracking experiment that investigates number attraction during recovery from garden-path sentences. The sentences contrasted locally ambiguous with unambiguous structures containing a plural or a singular attractor noun before a singular verb. Reading time data from the experiment suggest that number attraction effects occur when the processor has difficulty finding a grammatical analysis: Sentences with a local ambiguity had longer regression-path times when there was a plural number attractor than when there was a singular number attractor. The attractor number did not affect the processing of the unambiguous sentences. |
Keren Taub; Shlomit Yuval-Greenberg The perception of text triggers reflexive oculomotor orienting Journal Article In: Cortex, vol. 106, pp. 114–119, 2018. @article{Taub2018, As you read this text, your brain is busy integrating numerous different processes - perceptual, cognitive and motor. While you acquire the semantic and linguistic contents of this abstract, your eyes traverse its lines with speed and coordination. The oculomotor response to text is so rapid and precise that it is hypothesized it to be partially based on reflexive orienting mechanisms. In this study we examined the hypothesis that the presentation of written text triggers reflexive orienting toward the direction of reading, similarly to the effect of peripheral stimulation or that of symbolic directional cues (arrows or gazing eyes). In three experiments, participants (N = 120) were presented with task-irrelevant text, shortly followed by a left/right pro-saccade task. The first experiment confirmed the hypothesis by showing that saccades which are congruent with the direction of reading are faster than those which are incongruent. This was observed both in right-to-left (Hebrew) and in left-to-right (English) reading-systems and similarly in native-Hebrew and native-English readers. A second experiment showed that this directional bias is found not only for readable text but also for meaningless strings of letters. This confirmed that the bias is driven pre-reading non-lexical processes. The third experiment examined the time-course of this effect. We conclude that text-perception actives early reflexive eye-movements programs and suggest that this link is an essential building-block of fast and effortless reading. |
Malathi Thothathiri; Christine T. Asaro; Nina S. Hsu; Jared M. Novick Who did what? A causal role for cognitive control in thematic role assignment during sentence comprehension Journal Article In: Cognition, vol. 178, pp. 162–177, 2018. @article{Thothathiri2018, Thematic role assignment – generally, figuring out who did what to whom – is a critical component of sentence comprehension, which is influenced by both syntactic and semantic cues. Conflict between these cues can result in temporary consideration of multiple incompatible interpretations during real-time sentence processing. We tested whether the resolution of syntax-semantics conflict can be expedited by the online engagement of cognitive control processes that are routinely used to regulate behavior across domains. In this study, cognitive control deployment from a previous Stroop trial influenced eye movements during subsequent sentence comprehension. Specifically, when syntactic and semantic cues competed for influence on interpretation, dynamic cognitive control engagement led to (a) fewer overall looks to a picture illustrating the competing but incorrect interpretation (Experiment 1), or (b) steeper growth in looks to a picture illustrating the correct interpretation (Experiment 2). Thus, prior cognitive control engagement facilitated the resolution of syntax-semantics conflict by biasing processing towards the intended analysis. This conflict adaptation effect demonstrates a causal connection between cognitive control and real-time thematic role assignment. Broader patterns demonstrated that prior cognitive control engagement also modulated sentence processing irrespective of the presence of conflict, reflecting increased integration of newly arriving cues with prior sentential content. Together, the results suggest that cognitive control helps listeners determine correct event roles during real-time comprehension. |
Simon P. Tiffin-Richards; Sascha Schroeder The development of wrap-up processes in text reading: A study of children's eye movements Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 44, no. 7, pp. 1051–1063, 2018. @article{TiffinRichards2018, Reading comprehension is the product of constructing a coherent mental model of a text. Although some of the processes that are necessary to construct such a mental model are executed incrementally, others are deferred to the end of the clause or sentence, where integration processing is wrapped up before the reader progresses further in the text. In this longitudinal study of 65 German-speaking children across Grades 2, 3, and 4, we investigated the development of wrap-up processes at clause and sentence boundaries by tracking the children's eye movements while they read age-appropriate texts. Our central finding was that children in Grade 2 showed strong wrap-up effects that then slowly decreased across school grades. Children in Grades 3 and 4 also increasingly used clause and sentence boundaries to initiate regressions and rereading. Finally, children in Grade 2 were shown to be significantly disrupted in their reading at line breaks, which are inherent in continuous text. This disruption decreased as the children progressed to Grades 3 and 4. Overall, our results show that children exhibit an adultlike pattern of wrap-up effects by the time they reach Grade 4. We discuss this developmental trajectory in relation to models of text processing and mechanisms of eye-movement control. |
David J. Townsend Stage salience and situational likelihood in the formation of situation models during sentence comprehension Journal Article In: Lingua, vol. 206, pp. 1–20, 2018. @article{Townsend2018, Two experiments examined the relation between event structure, situational likelihood and eye fixation time while reading predicate modifiers in isolated sentences. Experiment 1 used activity predicates and preparatory process predicates (climbed a mountain), which make salient the process that leads to a culmination. Preparatory process predicates increased first pass time on durative modifiers (for several years) and decreased total time on frequency modifiers (e.g., every year). Situational likelihood was associated with fixation times on frame modifiers (last year) but not with fixation times on durative or frequency modifiers. Experiment 2 used activity predicates and result state predicates (halted a class), which make salient the result that follows from a culmination. Result state predicates had no effect on fixation times on durative modifiers and decreased total time on frequency modifiers. Situational likelihood was associated only with total time on durative modifiers. These results demonstrate that readers use the meanings of predicates and modifiers to form an initial model of a sentence and that the likelihood of the reported situation is related to reading time relatively late. The results are discussed in terms of type coercion theory and situation models in sentences and narratives. |
Annie Tremblay; Mirjam Broersma; Caitlin E. Coughlin The functional weight of a prosodic cue in the native language predicts the learning of speech segmentation in a second language Journal Article In: Bilingualism: Language and Cognition, vol. 21, no. 3, pp. 640–652, 2018. @article{Tremblay2018a, This study newly investigates whether the functional weight of a prosodic cue in the native language predicts listeners' learning and use of that cue in second-language speech segmentation. It compares English and Dutch listeners' use of fundamental-frequency (F0) rise as a cue to word-final boundaries in French. F0 rise signals word-initial boundaries in English and Dutch, but has a weaker functional weight in English than Dutch because it is more strongly correlated with vowel quality in English than Dutch. English- and Dutch-speaking learners of French matched in French proficiency and experience, and native French listeners completed a visual-world eye-tracking experiment in French where they monitored words ending with/out an F0 rise (replication of Tremblay, Broersma, Coughlin & Choi, 2016). Dutch listeners made earlier/greater use of the F0 rise than English listeners, and in one condition they made greater use of F0 rise than French listeners, extending the cue-weighting theory to speech segmentation. |
Annie Tremblay; Elsa Spinelli; Caitlin E. Coughlin; Jui Namjoshi Syntactic cues take precedence over distributional cues in native and non-native speech segmentation Journal Article In: Language and Speech, vol. 61, no. 4, pp. 615–631, 2018. @article{Tremblay2018, This study investigates whether syntactic cues take precedence over distributional cues in native and non-native speech segmentation by examining native and non-native speech segmentation in potential French-liaison contexts. Native French listeners and English-speaking second-language learners of French completed a visual-world eye-tracking experiment. Half the stimuli contained the pivotal consonant /t/, a frequent word onset but infrequent liaison consonant, and half contained /z/, a frequent liaison consonant but rare word onset. In the adjective–noun condition (permitting liaison), participants heard a consonant-initial target (e.g., le petit tatoué; le fameux zélé) that was temporarily ambiguous at the segmental level with a vowel-initial competitor (e.g., le petit [t]athée; le fameux [z]élu); in the noun–adjective condition (not permitting liaison), they heard a consonant-initial target (e.g., le client tatoué; le Français zélé) that was not temporarily ambiguous with a vowel-initial competitor (e.g., le client [*t]athée; le Français [*z]élu). Growth- curve analyses revealed that syntactic context modulated both groups' fixations (noun–adjective > adjective–noun), and pivotal consonant modulated both groups' fixations (/t/ > /z/) only in the adjective–noun condition, with the effect of the consonant decreasing in more proficient French learners. These results suggest that syntactic cues override distributional cues in the segmentation of French words in potential liaison contexts. |
Jorge R. Valdés Kroff; Rosa E. Guzzardo Tamargo; Paola E. Dussias Experimental contributions of eye-tracking to the understanding of comprehension processes while hearing and reading code-switches Journal Article In: Linguistic Approaches to Bilingualism, vol. 8, no. 1, pp. 98–133, 2018. @article{ValdesKroff2018, Researchers who study code-switching using lab-based approaches face a series of methodological challenges; these include, but are not limited to, using adequate techniques and tasks that allow for processing that reflects real-language usage and selecting stimuli that reflect the participants' code-switching community norms. We present two illustrative eye-tracking studies that consider these challenges. Study 1 tests whether experience with code-switching leads to differential processing of Spanish determiner-English noun code-switches (e.g., una cookie ‘a cookie'). Study 2 examines auxiliary-verb code-switches involving the progressive structure (e.g., están cooking ‘are cooking') and perfect structure (e.g., han cooked ‘have cooked') while participants read either for comprehension or provide grammaticality judgments. The results of both studies highlight the advantages that eye-tracking provides when its use is accompanied by an appropriate bilingual sample, by stimuli that reflect actual bilingual language use, and by secondary tasks that do not invoke metalinguistic processes. |
Geertje Bergen; Hans Rutger Bosker Linguistic expectation management in online discourse processing: An investigation of Dutch inderdaad ‘indeed' and eigenlijk ‘actually' Journal Article In: Journal of Memory and Language, vol. 103, pp. 191–209, 2018. @article{Bergen2018, Interpersonal discourse particles (DPs), such as Dutch inderdaad (≈‘indeed') and eigenlijk (≈‘actually') are highly frequent in everyday conversational interaction. Despite extensive theoretical descriptions of their polyfunctionality, little is known about how they are used by language comprehenders. In two visual world eye-tracking experiments involving an online dialogue completion task, we asked to what extent inderdaad, confirming an inferred expectation, and eigenlijk, contrasting with an inferred expectation, influence real-time understanding of dialogues. Answers in the dialogues contained a DP or a control adverb, and a critical discourse referent was replaced by a beep; participants chose the most likely dialogue completion by clicking on one of four referents in a display. Results show that listeners make rapid and fine-grained situation-specific inferences about the use of DPs, modulating their expectations about how the dialogue will unfold. Findings further specify and constrain theories about the conversation-managing function and polyfunctionality of DPs. |
Emiel Hoven; Evelyn C. Ferstl The roles of implicit causality and discourse context in pronoun resolution Journal Article In: Frontiers in Communication, vol. 3, pp. 53, 2018. @article{Hoven2018, Some interpersonal verbs show a bias in the proportion of times their subject and object arguments are rementioned in a sample of explanations for the eventuality the verb describes. This bias is known as the implicit causality bias. Several studies have shown that readers and listeners rapidly use the implicit causality bias during pronoun resolution. Whether listeners also rapidly incorporate relevant contextual information during pronoun resolution, is an open question. In the current paper, we report two visual world eye-tracking studies intended to answer this question. Participants listened to stories that included implicit causality verbs followed by a “because” clause with an ambiguous pronoun in its subject position. During the story, the participants looked at a screen on which potential referents of the ambiguous pronoun were displayed. In Experiment 1, a simple main effect of implicit causality bias on looks toward the character that was congruent with the bias was found among items in one of the two discourse conditions. Discourse context, however, only affected looks for a subset of verbs and in the opposite direction of what was hypothesized. In Experiment 2, no main effects of IC Bias or discourse context were found, but there was a marginally significant interaction which was not hypothesized. In both experiments, discourse context influenced looks only for a subset of verbs and never in the predicted direction. The results favor an account in which the influence of lexical semantics is, at least initially, stronger than the influence of world knowledge, and discourse context. Additional exploratory analyses suggested that eye movements already reveal remention biases at an early point in the sentence, whereas the causal potency of the subject argument is predicted by looks starting from the onset of the causal connective. |
André Vandierendonck; Maaike Loncke; Robert J. Hartsuiker; Timothy Desmet The role of executive control in resolving grammatical number conflict in sentence comprehension Journal Article In: Quarterly Journal of Experimental Psychology, vol. 71, no. 3, pp. 759–778, 2018. @article{Vandierendonck2018, In sentences with a complex subject noun phrase, like “The key to the cabinets is lost”, the grammatical number of the head noun (key) may be the same or different from that of the modifier noun phrase (cabinets). When the number is the same, comprehension is usually easier than when it is different. Grammatical number computation may occur while processing the modifier noun (integration phase) or while processing the verb (checking phase). We investigated at which phase number conflict and plausibility of the modifier noun as subject for the verb affect processing, and we imposed a gaze-contingent tone discrimination task in either phase to test whether number computation involves executive control. At both phases, gaze durations were longer when a concurrent tone task was present. Additionally, at the integration phase, gaze durations were longer under number conflict, and this effect was enhanced by the presence of a tone task, whereas no effects of plausibility of the modifier were observed. The finding that the effect of number match was larger under load shows that computation of the grammatical number of the complex noun phrase requires executive control in the integration phase, but not in the checking phase. |
Douglas A. Ruff; David H. Brainard; Marlene R. Cohen Neuronal population mechanisms of lightness perception Journal Article In: Journal of Neurophysiology, vol. 120, no. 5, pp. 2296–2310, 2018. @article{Ruff2018, The way that humans and animals perceive the lightness of an object depends on its physical luminance as well as its surrounding context. While neuronal responses throughout the visual pathway are modulated by context, the relationship between neuronal responses and lightness perception is poorly understood. We searched for a neuronal mechanism of lightness by recording responses of neuronal populations in monkey primary visual cortex (V1) and area V4 to stimuli that produce a lightness illusion in humans, in which the lightness of a disk depends on the context in which it is embedded. We found that the way individual units encode the luminance (or equivalently for our stimuli, contrast) of the disk and its context is extremely heterogeneous. This motivated us to ask whether the population representation in either V1 or V4 satisfies three criteria: 1) disk luminance is represented with high fidelity, 2) the context surrounding the disk is also represented, and 3) the representations of disk luminance and context interact to create a representation of lightness that depends on these factors in a manner consistent with human psychophysical judgments of disk lightness. We found that populations of units in both V1 and V4 fulfill the first two criteria, but that we cannot conclude that the two types of information in either area interact in a manner that clearly predicts human psychophysical measurements: the interpretation of our population measurements depends on how subsequent areas read out lightness from the population responses. |
Jason M. Samonds; Wilson S. Geisler; Nicholas J. Priebe Natural image and receptive field statistics predict saccade sizes Journal Article In: Nature Neuroscience, vol. 21, no. 11, pp. 1591–1599, 2018. @article{Samonds2018, Humans and other primates sample the visual environment using saccadic eye movements that shift a high-resolution fovea toward regions of interest to create a clear perception of a scene across fixations. Many mammals, however, like mice, lack a fovea, which raises the question of why they make saccades. Here we describe and test the hypothesis that saccades are matched to natural scene statistics and to the receptive field sizes and adaptive properties of neural populations. Specifically, we determined the minimum amplitude of saccades in natural scenes necessary to provide uncorrelated inputs to model neural populations. This analysis predicts the distributions of observed saccade sizes during passive viewing for nonhuman primates, cats, and mice. Furthermore, disrupting the development of receptive field properties by monocular deprivation changed saccade sizes consistent with this hypothesis. Therefore, natural-scene statistics and the neural representation of natural images appear to be critical factors guiding saccadic eye movements. |
Joshua A. Seideman; Terrence R. Stanford; Emilio Salinas Saccade metrics reflect decision-making dynamics during urgent choices Journal Article In: Nature Communications, vol. 9, pp. 2907, 2018. @article{Seideman2018, A perceptual judgment is typically characterized by constructing psychometric and chronometric functions, i.e., by mapping the accuracies and reaction times of motor choices as functions of a sensory stimulus feature dimension. Here, we show that various saccade metrics (e.g., peak velocity) are similarly modulated as functions of sensory cue viewing time during performance of an urgent-decision task. Each of the newly discovered functions reveals the dynamics of the perceptual evaluation process inherent to the underlying judgment. Remarkably, saccade peak velocity correlates with statistical decision confidence, suggesting that saccade kinematics reflect the degree of certainty with which an urgent perceptual decision is made. The data were explained by a race-to-threshold model that also replicates standard performance measures and cortical oculomotor neuronal activity in the task. The results indicate that, although largely stereotyped, saccade metrics carry subtle but reliable traces of the underlying cognitive processes that give rise to each oculomotor choice. |
S. Shushruth; Mark Mazurek; Michael N. Shadlen Comparison of decision-related signals in sensory and motor preparatory responses of neurons in area LIP Journal Article In: Journal of Neuroscience, vol. 38, no. 28, pp. 6350–6365, 2018. @article{Shushruth2018, Neurons in the lateral intraparietal (LIP) area of Macaques exhibit both sensory and oculomotor preparatory responses. During perceptual decision making, the preparatory responses have been shown to track the state of the evolving evidence leading to the decision. The sensory responses are known to reflect categorical properties of visual stimuli, but it is not known whether these responses also track evolving evidence. We recorded neural responses from lateral intraparietal area of 2 female rhesus monkeys during a direction discrimination task. We compared sensory and oculomotor-preparatory responses in the same neurons when either the discriminandum (random dot motion) or an eye movement choice-target was in the neuron's response field. The neural responses in both configurations reflected the strength and direction of motion and were correlated with the animal's choice, albeit more prominently when the choice-target was in the response field. However, the variance and autocorrelation pattern of only the motor preparatory responses reflected the process of evidence accumulation. Simulations suggest that the task related activity of sensory responses could be inherited through lateral interactions with neurons that are carrying evidence accumulation signals in their motor-preparatory responses. The results are consistent with the proposal that evolving decision processes are supported by persistent neural activity in the service of actions or intentions, as opposed to high-order representations of stimulus properties. |
Adam C. Snyder; Deepa Issar; Matthew A. Smith What does scalp electroencephalogram coherence tell us about long-range cortical networks? Journal Article In: European Journal of Neuroscience, pp. 1–16, 2018. @article{Snyder2018, Long-range interactions between cortical areas are undoubtedly a key to the computational power of the brain. For healthy human subjects, the premier method for measuring brain activity on fast timescales is electroencephalography (EEG), and coherence between EEG signals is often used to assay functional connectivity between different brain regions. However, the nature of the underlying brain activity that is reflected in EEG coherence is currently the realm of speculation, because seldom have EEG signals been recorded simultaneously with intracranial recordings near cell bodies in multiple brain areas. Here, we take the early steps towards narrowing this gap in our understanding of EEG coherence by measuring local field potentials with microelectrode arrays in two brain areas (extrastriate visual area V4 and dorsolateral prefrontal cortex) simultaneously with EEG at the nearby scalp in rhesus macaque monkeys. Although we found inter-area coherence at both scales of measurement, we did not find that scalp-level coherence was reliably related to coherence between brain areas measured intracranially on a trial-to-trial basis, despite that scalp-level EEG was related to other important features of neural oscillations, such as trial-to-trial variability in overall amplitudes. This suggests that caution must be exercised when interpreting EEG coherence effects, and new theories devised about what aspects of neural activity long-range coherence in the EEG reflects. |
Adam C. Snyder; Byron M. Yu; Matthew A. Smith Distinct population codes for attention in the absence and presence of visual stimulation Journal Article In: Nature Communications, vol. 9, pp. 4382, 2018. @article{Snyder2018a, Visual neurons respond more vigorously to an attended stimulus than an unattended one. How the brain prepares for response gain in anticipation of that stimulus is not well understood. One prominent proposal is that anticipation is characterized by gain-like modulations of spontaneous activity similar to gains in stimulus responses. Here we test an alternative idea: anticipation is characterized by a mixture of both increases and decreases of spontaneous firing rates. Such a strategy would be adaptive as it supports a simple linear scheme for disentangling internal, modulatory signals from external, sensory inputs. We recorded populations of V4 neurons in monkeys performing an attention task, and found that attention states are signaled by different mixtures of neurons across the population in the presence or absence of a stimulus. Our findings support a move from a stimulation-invariant account of anticipation towards a richer view of attentional modulation in a diverse neuronal population. |
Jessica Taubert; Goedele Van Belle; Rufin Vogels; Bruno Rossion The impact of stimulus size and orientation on individual face coding in monkey face-selective cortex Journal Article In: Scientific Reports, vol. 8, pp. 10339, 2018. @article{Taubert2018, Face-selective neurons in the monkey temporal cortex discharge at different rates in response to pictures of different individual faces. Here we tested whether this pattern of response across single neurons in the face-selective area ML (located in the middle Superior Temporal Sulcus) tolerates two affine transformations; picture-plane inversion, known to decrease the average response of face- selective neurons and the other, stimulus size. We recorded the response of 57 ML neurons in two awake and fixating monkeys. Face stimuli were presented at two sizes (10 and 5 degrees of visual angle) and two orientations (upright and inverted). Different faces elicited distinct patterns of activity across ML neurons that were reliable (i.e., predictable with a classifier) within a specific size and orientation condition. Despite observing a reduction in the average response magnitude of face-selective neurons to inverted faces, compared to upright faces, classifier performance was above chance for both upright and inverted faces. While decoding was largely preserved across changes in stimulus size, a classifier trained with one orientation condition and tested on the other did not lead to performance above chance level. We conclude that different individual faces can be decoded from patterns of responses in the monkey area ML regardless of orientation or size, but with qualitatively different patterns of responses for upright and inverted faces. |
Kasper Vinken; Hans P. Op de Beeck; Rufin Vogels Face repetition probability does not affect repetition suppression in macaque inferotemporal cortex Journal Article In: Journal of Neuroscience, vol. 38, no. 34, pp. 7492–7504, 2018. @article{Vinken2018, Repetition suppression, which refers to reduced neural activity for repeated stimuli, is typically explained by bottom-up or local adaptation mechanisms. However, recent theories have emphasized the role of top-down processes, suggesting that this response reduction reflects the fulfillment of perceptual expectations. To support this, an influential human functional magnetic resonance imaging (fMRI) study showed that the magnitude of suppression is modulated by the probability of a repetition. No such repetition probability effect was found in macaque inferior temporal (IT) cortex for spiking activity, despite the presence of repetition suppression. Contrary to the human fMRI studies that showed an effect of repetition probability, the macaque single unit study employed a large variety of unfamiliar stimuli and the monkeys were not required to attend the stimuli. Here, as in the human fMRI studies, we employed faces as stimuli and made the monkeys attend to the stimulus content. We simultaneously recorded spiking activity and local field potentials (LFPs) in the middle lateral face patch (ML) of one monkey (male), and a face-responsive region of another (female). While we observed significant repetition suppression of spiking activity and high gamma band LFPs in both animals, there were no effects of repetition probability, even when repetitions were task-relevant and repetition probability affected behavioral decisions. In conclusion, despite the use of face stimuli and a stimulus-related task, no neural signature of repetition probability was present for faces in a face responsive patch of macaque IT. This further challenges a general perceptual expectation account of repetition suppression. |
Matthew L. Leavitt; Florian Pieper; Adam J. Sachs; Julio C. Martinez-Trujillo A quadrantic bias in prefrontal representation of visual-mnemonic space Journal Article In: Cerebral Cortex, vol. 28, no. 7, pp. 2405–2421, 2018. @article{Leavitt2018, Single neurons in primate dorsolateral prefrontal cortex (dLPFC) are known to encode working memory (WM) representations of visual space. Psychophysical studies have shown that the horizontal and vertical meridians of the visual field can bias spatial information maintained in WM. However, most studies and models have tacitly assumed that dLPFC neurons represent mnemonic space homogenously. The anatomical organization of these representations has also eluded clear parametric description. We investigated these issues by recording from neuronal ensembles in macaque dLPFC with microelectrode arrays while subjects performed an oculomotor delayed-response task. We found that spatial WM representations in macaque dLPFC are biased by the vertical and horizontal meridians of the visual field, dividing mnemonic space into quadrants. This bias is reflected in single neuron firing rates, neuronal ensemble representations, the spike count correlation structure, and eye movement patterns. We also found that dLPFC representations of mnemonic space cluster anatomically in a nonretinotopic manner that partially reflects the organization of visual space. These results provide an explanation for known WM biases, and reveal novel principles of WM representation in prefrontal neuronal ensembles and across the cortical surface, as well as the need to reconceptualize models of WM to accommodate the observed representational biases. |
Aaron J. Levi; Jacob L. Yates; Alexander C. Huk; Leor N. Katz Strategic and dynamic temporal weighting for perceptual decisions in humans and macaques Journal Article In: eNeuro, vol. 5, no. 5, pp. 1–15, 2018. @article{Levi2018, Perceptual decision-making is often modeled as the accumulation of sensory evidence over time. Recent studies using psychophysical reverse correlation have shown that even though the sensory evidence is stationary over time, subjects may exhibit a time-varying weighting strategy, weighting some stimulus epochs more heavily than others. While previous work has explained time-varying weighting as a consequence of static decision mechanisms (e.g., decision bound or leak), here we show that time-varying weighting can reflect strategic adaptation to stimulus statistics, and thus can readily take a number of forms. We characterized the temporal weighting strategies of humans and macaques performing a motion discrimination task in which the amount of information carried by the motion stimulus was manipulated over time. Both species could adapt their temporal weighting strategy to match the time-varying statistics of the sensory stimulus. When early stimulus epochs had higher mean motion strength than late, subjects adopted a pronounced early weighting strategy, where early information was weighted more heavily in guiding perceptual decisions. When the mean motion strength was greater in later stimulus epochs, in contrast, subjects shifted to a marked late weighting strategy. These results demonstrate that perceptual decisions involve a temporally flexible weighting process in both humans and monkeys, and introduce a paradigm with which to manipulate sensory weighting in decision-making tasks. |
Liu D. Liu; Kenneth D. Miller; Christopher C. Pack A unifying motif for spatial and directional surround suppression Journal Article In: Journal of Neuroscience, vol. 38, no. 4, pp. 989–999, 2018. @article{Liu2018c, In the visual system, the response to a stimulus in a neuron's receptive field can be modulated by stimulus context, and the strength of these contextual influences vary with stimulus intensity. Recent work has shown how a theoretical model, the stabilized supralinear network (SSN), can account for such modulatory influences, using a small set of computational mechanisms. While the predictions of the SSN have been confirmed in primary visual cortex (V1), its computational principles apply with equal validity to any cortical structure. We have therefore tested the generality of the SSN by examining modulatory influences in the middle temporal area (MT) of the macaque visual cortex, using electrophysiological recordings and pharmacological manipulations. We developed a novel stimulus that can be adjusted parametrically to be larger or smaller in the space of all possible motion directions. We found, as predicted by the SSN, that MT neurons integrate across motion directions for low-contrast stimuli, but that they exhibit suppression by the same stimuli when they are high in contrast. These results are analogous to those found in visual cortex when stimulus size is varied in the space domain. We further tested the mechanisms of inhibition using pharmacologically manipulations of inhibitory efficacy. As predicted by the SSN, local manipulation of inhibitory strength altered firing rates, but did not change the strength of surround suppression. These results are consistent with the idea that the SSN can account for modulatory influences along different stimulus dimensions and in different cortical areas. |
Kaleb A. Lowe; Jeffrey D. Schall Functional categories of visuomotor neurons in macaque frontal eye field Journal Article In: eNeuro, vol. 5, no. 5, pp. 1–21, 2018. @article{Lowe2018, Frontal eye field (FEF) in macaque monkeys contributes to visual attention, visual-motor transformations and production of eye movements. Traditionally, neurons in FEF have been classified by the magnitude of increased discharge rates following visual stimulus presentation, during a waiting period, and associated with eye movement production. However, considerable heterogeneity remains within the traditional visual, visuomovement and movement categories. Cluster analysis is a data-driven method of identifying self-segregating groups within a dataset. Because many cluster analysis techniques exist and outcomes vary with analysis assumptions, consensus clustering aggregates over multiple analyses, identifying robust groups. To describe more comprehensively the neuronal composition of FEF, we applied a consensus clustering technique for unsupervised categorization of patterns of spike rate modulation measured during a memory-guided saccade task. We report ten functional categories, expanding on the traditional three. Categories were distinguished by latency, magnitude, and sign of visual response, presence of sustained activity, and dynamics, magnitude and sign of saccade-related modulation. Consensus clustering can include other metrics and can be applied to datasets from other brain regions to provide better information guiding microcircuit models of cortical function. |
Eric Lowet; Bruno Gomes; Karthik Srinivasan; Huihui Zhou; Robert John Schafer; Robert Desimone Enhanced neural processing by covert attention only during microsaccades directed toward the attended stimulus Journal Article In: Neuron, vol. 99, no. 1, pp. 207–214.e3, 2018. @article{Lowet2018, Attention can be “covertly” directed without eye movements; yet, even during fixation, there are continuous microsaccades (MSs). In areas V4 and IT of macaques, we found that firing rates and stimulus representations were enhanced by attention but only following a MS toward the attended stimulus. The onset of neural attentional modulations was tightly coupled to the MS onset. The results reveal a major link between the effects of covert attention on cortical visual processing and the overt movement of the eyes. |
Yiliang Lu; Jiapeng Yin; Zheyuan Chen; Hongliang Gong; Ye Liu; Liling Qian; Xiaohong Li; Rui Liu; Ian Max Andolina; Wei Wang Revealing detail along the visual hierarchy: Neural clustering preserves acuity from V1 to V4 Journal Article In: Neuron, vol. 98, no. 2, pp. 417–428.e3, 2018. @article{Lu2018a, How primates perceive objects along with their detailed features remains a mystery. This ability to make fine visual discriminations depends upon a high-acuity analysis of spatial frequency (SF) along the visual hierarchy from V1 to inferotemporal cortex. By studying the transformation of SF across macaque parafoveal V1, V2, and V4, we discovered SF-selective functional domains in V4 encoding higher SFs up to 12 cycles/°. These intermittent higher-SF-selective domains, surrounded by domains encoding lower SFs, violate the inverse relationship between SF preference and retinal eccentricity. The neural activities of higher- and lower-SF domains correspond to local and global features, respectively, of the same stimuli. Neural response latencies in high-SF domains are around 10 ms later than in low-SF domains, consistent with the coarse-to-fine nature of perception. Thus, our finding of preserved resolution from V1 into V4, separated both spatially and temporally, may serve as a connecting link for detailed object representation. How do we perceive scenes or objects yet resolve their fine details? Lu et al. found that high spatial detail organizes in spatiotemporally separated neural clusters within primate intermediate area V4, preserving visual acuity from early toward higher cortical areas. |
Thomas Zhihao Luo; John H. R. Maunsell Attentional changes in either criterion or sensitivity are associated with robust modulations in lateral prefrontal cortex Journal Article In: Neuron, vol. 97, no. 6, pp. 1382–1393.e7, 2018. @article{Luo2018a, Visual attention is associated with neuronal changes across the brain, and these widespread signals are generally assumed to underlie a unitary mechanism of attention. However, using signal detection theory, attention-related effects on performance can be partitioned into changes in either the subject's criterion or sensitivity. Neuronal modulations associated with only sensitivity changes were previously observed in visual cortex, raising questions about which structures mediate attention-related changes in criterion and whether individual neurons are involved in multiple components of attention. Here, we recorded from monkey lateral prefrontal cortex (LPFC) and found that, in contrast to visual cortex, neurons in LPFC changed their firing rates, pairwise correlation, and Fano factor when subjects changed either their criterion or their sensitivity. These results indicate that attention-related neuronal modulations in separate brain regions are not a monolithic signal and instead can be linked to distinct behavioral changes. Luo and Maunsell show that the modulations in prefrontal cortex correspond to multiple components of attention and differ from modulations in visual cortex, indicating that different brain structures underlie distinct attentional mechanisms and that attention is not a unitary process. |
Liya Ma; Kevin J. Skoblenick; Kevin D. Johnston; Stefan Everling Ketamine alters lateral prefrontal oscillations in a rule-based working memory gask Journal Article In: Journal of Neuroscience, vol. 38, no. 10, pp. 2482–2494, 2018. @article{Ma2018a, Acute administration of N-methyl-D-aspartate receptor (NMDAR) antagonists in healthy humans and animals produces working memory deficits similar to those observed in schizophrenia. However, it is unclear whether they also lead to altered low-frequency (<=60Hz) neural oscillatory activities similar to those associated with schizophrenia during working memory processes. Here we recorded local field potentials (LFPs) and single unit activity from the lateral prefrontal cortex (LPFC) of three male rhesus macaque monkeys while they performed a rule-based prosaccade and antisaccade working memory task, both before and after systemic injections of a subanesthetic dose (<=0.7mg/kg) of ketamine. Accompanying working-memory impairment, ketamine enhanced the low gamma band (30-60Hz) and dampened the beta band (13-30Hz) oscillatory activities in the LPFC during both delay periods and inter-trial intervals. It also increased task-related alpha-band activities, likely reflecting compromised attention. Beta-band oscillations may be especially relevant to working memory processes, as stronger beta power weakly but significantly predicted shorter saccadic reaction time. Also in beta band, ketamine reduced the performance-related oscillation as well as the rule information encoded in the spectral power. Ketamine also reduced rule information in the spike-field phase consistency in almost all frequencies up to 60Hz. Our findings support NMDAR antagonists in non-human primates as a meaningful model for altered neural oscillations and synchrony, which reflect a disorganized network underlying the working memory deficits in schizophrenia. |
Kazutaka Maeda; Jun Kunimatsu; Okihide Hikosaka Amygdala activity for the modulation of goal-directed behavior in emotional contexts Journal Article In: PLoS Biology, vol. 16, no. 6, pp. e2005339, 2018. @article{Maeda2018, Choosing valuable objects and rewarding actions is critical for survival. While such choices must be made in a way that suits the animal's circumstances, the neural mechanisms underlying such context-appropriate behavior are unclear. To address this question, we devised a context-dependent reward-seeking task for macaque monkeys. Each trial started with the appearance of one of many visual scenes containing two or more objects, and the monkey had to choose the good object by saccade to get a reward. These scenes were categorized into two dimensions of emotional context: dangerous versus safe and rich versus poor. We found that many amygdala neurons were more strongly activated by dangerous scenes, by rich scenes, or by both. Furthermore, saccades to target objects occurred more quickly in dangerous than in safe scenes and were also quicker in rich than in poor scenes. Thus, amygdala neuronal activity and saccadic reaction times were negatively correlated in each monkey. These results suggest that amygdala neurons facilitate targeting saccades predictably based on aspects of emotional context, as is necessary for goal-directed and social behavior. |
Alex J. Major; Susheel Vijayraghavan; Stefan Everling Cholinergic overstimulation attenuates rule selectivity in macaque prefrontal cortex Journal Article In: Journal of Neuroscience, vol. 38, no. 5, pp. 1137–1150, 2018. @article{Major2018, Acetylcholine is released in the prefrontal cortex (PFC) and is a key modulator of cognitive performance in primates. Cholinergic stimulation has been shown to have beneficial effects on performance of cognitive tasks, and cholinergic receptors are being actively explored as promising targets for ameliorating cognitive deficits in Alzheimer's disease.Wehypothesized that cholinergic stimulation of PFC during performance of a cognitive task would augment neuronal activity and neuronal coding of task attributes. We iontophoretically applied the general cholinergic receptor agonist carbachol onto neurons in dorsolateral PFC (DLPFC) of male rhesus macaques performing rule-guided prosaccades and antisaccades, a well established oculomotor task for testing cognitive control. Carbachol application had heterogeneous effects on neuronal excitability, with both excitation and suppression observed in significant proportions. Contrary to our prediction, neurons with rule-selective activity exhibited a reduction in selectivity during carbachol application. Cholinergic stimulation disrupted rule selectivity regardless of whether it had suppressive or excitatory effects on these neurons. In addition, cholinergic stimulation excited putative pyramidal neurons, whereas the activity of putative interneurons remained unchanged. Moreover, cholinergic stimulation attenuated saccade direction selectivity in putative pyramidal neurons due to nonspecific increases in activity. Our results suggest excessive cholinergic stimulation has detrimental effects on DLPFC representations of task attributes. These findings delineate the complexity and heterogeneity of neuromodulation of cerebral cortex by cholinergic stimulation, an area of active exploration with respect to the development of cognitive enhancers. |
Alexandria C. Marino; James A. Mazer Saccades trigger predictive updating of attentional topography in area V4 Journal Article In: Neuron, vol. 98, no. 2, pp. 429–438.e4, 2018. @article{Marino2018, During natural behavior, saccades and attention act together to allocate limited neural resources. Attention is generally mediated by retinotopic visual neurons; therefore, specific neurons representing attended features change with each saccade. We investigated the neural mechanisms that allow attentional targeting in the face of saccades. Specifically, we looked for predictive changes in attentional modulation state or receptive field position that could stabilize attentional representations across saccades in area V4, known to be necessary for attention-dependent behavior. We recorded from neurons in monkeys performing a novel spatiotopic attention task, in which performance depended on accurate saccade compensation. Measurements of attentional modulation revealed a predictive attentional “hand-off” corresponding to a presaccadic transfer of attentional state from neurons inside the attentional focus before the saccade to those that will be inside the focus after the saccade. The predictive nature of the hand-off ensures that attentional brain maps are properly configured immediately after each saccade. Using a novel behavioral task, Marino and Mazer report that the attentional modulation state of neurons in extrastriate area V4 is updated before saccade onset. This attentional hand-off is independent of changes in receptive field position and represents a new type of perisaccadic updating. |
Adam Pallus; Mark M. G. Walton; Michael J. Mustari Activity of near-response cells during disconjugate saccades in strabismic monkeys Journal Article In: Journal of Neurophysiology, vol. 120, no. 5, pp. 2282–2295, 2018. @article{Pallus2018, Infantile strabismus is a common disorder characterized by a chronic misalignment of the eyes, impairment of binocular vision, and oculomotor abnormalities. Nonhuman primates with strabismus, induced in infancy, show a pattern of abnormalities similar to those of strabismic children. This allows strabismic nonhuman primates to serve as an ideal animal model to examine neural mechanisms associated with aberrant oculomotor behavior. Here, we test the hypothesis that impairment of disparity vergence and horizontal saccade disconjugacy in exotropia and esotropia are associated with disrupted tuning of near-and far-response neurons in the supraoculomotor area (SOA). In normal animals, these neurons carry signals related to vergence position and/or velocity. We hypothesized that, in strabismus, these neurons modulate inappropriately in association with saccades between equidistant targets. We recorded from 62 SOA neurons from 4 strabismic animals (2 esotropes and 2 exotropes) during visually guided saccades to a target that stepped to different locations on a tangent screen. Under these same conditions, SOA neurons in normal animals show no detectable modulation. In our strabismic subjects, we found that a subset of SOA neurons carry weak vergence velocity signals during saccades. In addition, a subset of SOA neurons showed clear modulation associated with slow fluctuations of horizontal strabismus angle in the absence of a saccade. We suggest that abnormal SOA activity contributes to fixation instability but plays only a minor role in the horizontal disconjugacy of saccades that do not switch fixation from one eye to the other. NEW & NOTEWORTHY The present study is the first to investigate the activity of neurons in the supraoculomotor area (SOA) during horizontally disconjugate saccades in a nonhuman primate model of infantile strabismus. We report that fluctuations of horizontal strabismus angle, during fixation of static targets on a tangent screen, are associated with contextually inappropriate modulation of SOA activity. However, firing rate modulation during saccades is too weak to make a major contribution to horizontal disconjugacy. |
Angelo Pirrone; Habiba Azab; Benjamin Y. Hayden; Tom Stafford; James A. R. Marshall Evidence for the speed–value trade-Off: Human and monkey decision making Is magnitude sensitive Journal Article In: Decision, vol. 5, no. 2, pp. 129–142, 2018. @article{Pirrone2018, Complex natural systems from brains to bee swarms have evolved to make adaptive multifactorial decisions. Recent theoretical and empirical work suggests that many evolved systems may take advantage of common motifs across multiple domains. We are particularly interested in value sensitivity (i.e., sensitivity to the magnitude or intensity of the stimuli or reward under consideration) as a mechanism to resolve deadlocks adaptively. This mechanism favors long-term reward maximization over accuracy in a simple manner, because it avoids costly delays associated with ambivalence between similar options; speed–value trade-offs have been proposed to be evolutionarily advantageous for many kinds of decision. A key prediction of the value-sensitivity hypothesis is that choices between equally valued options will proceed faster when the options have a high value than when they have a low value. However, value sensitivity is not part of idealized choice models such as diffusion to bound. Here, we examine 2 different choice behaviors in 2 different species, perceptual decisions in humans and economic choices in rhesus monkeys, to test this hypothesis. We observe the same value sensitivity in both human perceptual decisions and monkey value-based decisions. These results endorse the idea that neural decision systems make use of the same basic principle of value sensitivity in order to resolve costly deadlocks and thus improve long-term reward intake. |
Evan D. Remington; Devika Narain; Eghbal A. Hosseini; Mehrdad Jazayeri Flexible sensorimotor computations through rapid reconfiguration of cortical dynamics Journal Article In: Neuron, vol. 98, no. 5, pp. 1005–1019.e5, 2018. @article{Remington2018a, Neural mechanisms that support flexible sensorimotor computations are not well understood. In a dynamical system whose state is determined by interactions among neurons, computations can be rapidly reconfigured by controlling the system's inputs and initial conditions. To investigate whether the brain employs such control mechanisms, we recorded from the dorsomedial frontal cortex of monkeys trained to measure and produce time intervals in two sensorimotor contexts. The geometry of neural trajectories during the production epoch was consistent with a mechanism wherein the measured interval and sensorimotor context exerted control over cortical dynamics by adjusting the system's initial condition and input, respectively. These adjustments, in turn, set the speed at which activity evolved in the production epoch, allowing the animal to flexibly produce different time intervals. These results provide evidence that the language of dynamical systems can be used to parsimoniously link brain activity to sensorimotor computations. Remington et al. employ a dynamical systems perspective to understand how the brain flexibly controls timed movements. Results suggest that neurons in the frontal cortex form a recurrent network whose behavior is flexibly controlled by inputs and initial conditions. |
Thomas R. Reppert; Mathieu Servant; Richard P. Heitz; Jeffrey D. Schall In: Journal of Neurophysiology, vol. 120, no. 1, pp. 372–384, 2018. @article{Reppert2018, Balancing the speed-accuracy tradeoff (SAT) is necessary for successful behavior. Using a visual search task with interleaved cues emphasizing speed or accuracy, we recently reported diverse contributions of frontal eye field (FEF) neurons instantiating salience evidence and response preparation. Here, we report replication of visual search SAT performance in two macaque monkeys, new information about variation of saccade dynamics with SAT, extension of the neurophysiological investigation to describe processes in the superior colliculus (SC), and a description of the origin of search errors in this task. Saccade vigor varied idiosyncratically across SAT conditions and monkeys but tended to decrease with response time. As observed in the FEF, speed-accuracy tradeoff was accomplished through several distinct adjustments in the superior colliculus. In “Accurate” relative to “Fast” trials, visually responsive neurons in SC as in FEF had lower baseline firing rates and later target selection. The magnitude of these adjustments in SC was indistinguishable from that in FEF. Search errors occurred when visual salience neurons in the FEF and the SC treated distractors as targets, even in the Accurate condition. Unlike FEF, the magnitude of visual responses in the SC did not vary across SAT conditions. Also unlike FEF, the activity of SC movement neurons when saccades were initiated was equivalent in Fast and Accurate trials. Saccade-related neural activity in SC, but not FEF, varied with saccade peak velocity. These results extend our understanding of the cortical and subcortical contributions to SAT. |
Martin R. Vasilev; Timothy J. Slattery; Julie A. Kirkby; Bernhard Angele What are the costs of degraded parafoveal previews during silent reading? Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 44, no. 3, pp. 371–386, 2018. @article{Vasilev2018, It has been suggested that the preview benefit effect is actually a combination of preview benefit and preview costs. Marx et al. (2015) proposed that visually degrading the parafoveal preview reduces the costs associated with traditional parafoveal letter masks used in the boundary paradigm (Rayner, 1975), thus leading to a more neutral baseline. We report 2 experiments of skilled adults reading silently. In Experiment 1, we found no compelling evidence that degraded previews reduced processing costs associated with traditional letter masks. Moreover, participants were highly sensitive to detecting degraded display changes. Experiment 2 used the boundary detection paradigm (Slattery, Angele, & Rayner, 2011) to explore whether participants were capable of detecting actual letter changes or if they were responding purely to changes in degradation. Half of the participants were instructed to respond to any noticed display changes; the other half were instructed to respond only to changes in letter identities. Participants were highly sensitive to degraded changes. In fact, these changes were so apparent that they reduced the sensitivity to letter masks. In the context of the model proposed by Angele, Slattery, and Rayner (2016), we suggest that degraded previews interfere with the attentional stage, as evidenced by the general lack of foveal load effects. In summary, we found that increasingly degrading parafoveal letter masks does not reduce their processing costs in adults, but that both degraded valid and invalid previews introduce additional costs in terms of greater display change awareness. |
Shravan Vasishth; Daniela Mertzen; Lena A. Jäger; Andrew Gelman The statistical significance filter leads to overoptimistic expectations of replicability Journal Article In: Journal of Memory and Language, vol. 103, pp. 151–175, 2018. @article{Vasishth2018, It is well-known in statistics (e.g., Gelman & Carlin, 2014) that treating a result as publishable just because the p-value is less than 0.05 leads to overoptimistic expectations of replicability. These effects get published, leading to an overconfident belief in replicability. We demonstrate the adverse consequences of this statistical significance filter by conducting seven direct replication attempts (268 participants in total) of a recent paper (Levy & Keller, 2013). We show that the published claims are so noisy that even non-significant results are fully compatible with them. We also demonstrate the contrast between such small-sample studies and a larger-sample study; the latter generally yields a less noisy estimate but also a smaller effect magnitude, which looks less compelling but is more realistic. We reiterate several suggestions from the methodology literature for improving current practices. |
Outi Veivo; Vincent Porretta; Jukka Hyona; Juhani Jarvikivi Spoken second language words activate native language orthographic information in late second language learners Journal Article In: Applied Psycholinguistics, vol. 39, no. 05, pp. 1011–1032, 2018. @article{Veivo2018, This study investigated the time course of activation of orthographic information in spoken word recognition with two visual world eye-tracking experiments in a task where second language (L2) spoken word forms had to be matched with their printed referents. Participants ( n = 64) were native Finnish learners of L2 French ranging from beginners to highly proficient. In Experiment 1, L2 targets (e.g., <cidre> /sidʀ/) were presented with either orthographically overlapping onset competitors (e.g., <cintre> /sɛ̃tʀ/) or phonologically overlapping onset competitors ( <cycle> /sikl/). In Experiment 2, L2 targets (e.g., <paume> /pom/) were associated with competitors in Finnish, L1 of the participants, in conditions symmetric to Experiment 1 ( <pauhu> /pauhu/ vs. <pommi> /pom:i/). In the within-language experiment (Experiment 1), the difference in target identification between the experimental conditions was not significant. In the between-language experiment (Experiment 2), orthographic information impacted the mapping more in lower proficiency learners, and this effect was observed 600 ms after the target word onset. The influence of proficiency on the matching was nonlinear: proficiency impacted the mapping significantly more in the lower half of the proficiency scale in both experiments. These results are discussed in terms of coactivation of orthographic and phonological information in L2 spoken word recognition. |
Aaron Veldre; Sally Andrews How does foveal processing difficulty affect parafoveal processing during reading? Journal Article In: Journal of Memory and Language, vol. 103, pp. 74–90, 2018. @article{Veldre2018, Models of eye movement control during reading assume that the difficulty of processing word n in a sentence modulates the depth of processing of the upcoming word/s (word n + 1) in the parafovea. This foveal load hypothesis is widely accepted in the literature despite surprisingly few clear replications of the basic effect. We sought to establish whether observing a foveal load effect depends on the type of parafoveal preview used in the boundary paradigm. Participants' eye movements were recorded in two experiments as they read sentences in which a low- or high-frequency word n—a typical manipulation of foveal load—preceded a critical target word. Prior to the reader making a saccade to word n + 1, the parafoveal preview was either identical to word n + 1; an orthographically similar word or nonword; or an unrelated word or nonword. The results revealed that the critical evidence for a foveal load effect—an interaction between word n frequency and word n + 1 preview—was limited to conditions in which the invalid preview baseline was an orthographically illegal nonword. The remaining conditions produced completely additive effects of the two factors. These findings raise questions about the mechanisms underlying the spillover of foveal processing difficulty to parafoveal words. The implications for theories of reading are discussed. |
Aaron Veldre; Sally Andrews Beyond cloze probability: Parafoveal processing of semantic and syntactic information during reading Journal Article In: Journal of Memory and Language, vol. 100, pp. 1–17, 2018. @article{Veldre2018a, Theories of eye movement control in reading assume that early oculomotor decisions are determined by a word's frequency and cloze probability. This assumption is challenged by evidence that readers are sensitive to the contextual plausibility of an upcoming word: First-pass fixation probability and duration are reduced when the parafoveal preview is a plausible, but unpredictable, word relative to an implausible word. The present study sought to establish whether the source of this effect is sensitivity to violations of syntactic acceptability. In two experiments, the gaze-contingent boundary paradigm was used to compare contextually plausible previews to semantically acceptable and anomalous previews that either matched or violated syntactic rules. Results showed that readers benefited from the convergence of semantic and syntactic acceptability early enough in the timecourse of reading to affect skipping. In addition, both semantic and syntactic plausibility yielded preview effects on target fixation duration measures, providing direct evidence of parafoveal syntactic processing in reading. These results highlight the limitations of relying solely on cloze probability to index contextual influences on early lexical processing. The implications of the data for models of eye movement control and language comprehension are discussed. |