All EyeLink Publications
All 12,000+ peer-reviewed EyeLink research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications library using keywords such as Visual Search, Smooth Pursuit, Parkinson’s, etc. You can also search for individual author names. Eye-tracking studies grouped by research area can be found on the solutions pages. If we missed any EyeLink eye-tracking papers, please email us!
2015 |
Julia Boggia; Jelena Ristic Social event segmentation Journal Article In: Quarterly Journal of Experimental Psychology, vol. 68, no. 4, pp. 731–744, 2015. @article{Boggia2015, Humans are experts in understanding social environments. What perceptual and cognitive processes enable such competent evaluation of social information? Here we show that environmental content is grouped into units of "social perception", which are formed automatically based on the attentional priority given to social information conveyed by eyes and faces. When asked to segment a clip showing a typical daily scenario, participants were remarkably consistent in identifying the boundaries of social events. Moreover, at those social event boundaries, participants' eye movements were reliably directed to actors' eyes and faces. Participants' indices of attention measured during the initial passive viewing, reflecting natural social behaviour, also showed a remarkable correspondence with overt social segmentation behaviour, reflecting the underlying perceptual organization. Together, these data show that dynamic information is automatically organized into meaningful social events on an ongoing basis, strongly suggesting that the natural comprehension of social content in daily life might fundamentally depend on this underlying grouping process. |
Jens Bölte; Andrea Böhl; Christian Dobel; Pienie Zwitserlood In: Frontiers in Psychology, vol. 6, pp. 1540, 2015. @article{Boelte2015, In three experiments, participants named target pictures by means of German compound words (e.g., Gartenstuhl-garden chair), each accompanied by two different distractor pictures (e.g., lawn mower and swimming pool). Targets and distractor pictures were semantically related either associatively (garden chair and lawn mower) or by a shared semantic category (garden chair and wardrobe). Within each type of semantic relation, target and distractor pictures either shared morpho-phonological (word-form) information (Gartenstuhl with Gartenzwerg, garden gnome, and Gartenschlauch, garden hose) or not. A condition with two completely unrelated pictures served as baseline. Target naming was facilitated when distractor and target pictures were morpho-phonologically related. This is clear evidence for the activation of word-form information of distractor pictures. Effects were larger for associatively than for categorically related distractors and targets, which constitute evidence for lexical competition. Mere categorical relatedness, in the absence of morpho-phonological overlap, resulted in null effects (Experiments 1 and 2), and only speeded target naming when effects reflect only conceptual, but not lexical processing (Experiment 3). Given that distractor pictures activate their word forms, the data cannot be easily reconciled with discrete serial models. The re sults fit well with models that allow information to cascade forward from conceptual to word-form levels. |
Yoram Bonneh; Yael Adini; Uri Polat Contrast sensitivity revealed by microsaccades Journal Article In: Journal of vision, vol. 15, no. 9, pp. 1–12, 2015. @article{Bonneh2015, Microsaccades are small rapid and involuntary eye movements that occur during fixation in an apparently stochastic manner. They are known to be inhibited in response to sensory transients, with a time course that depends on the stimulus parameters and attention. However, the temporal precision of their onsets and the degree to which they can be used to assess the response of the visual system to basic stimulus parameters is currently unknown. Here we studied microsaccade response properties as a function of the contrast and spatial frequency of visual onsets. Observers (n¼ 18) viewed and silently counted 2-min sequences of Gabor patches presented briefly (100 ms) at 1 Hz. Contrast and spatial frequency were randomized in different experiments. We found that the microsaccade response time, as measured by the latency of the first microsaccade relative to stimulus onset following its release from inhibition, was sensitive to the contrast and spatial frequency of the stimulus and could be used to extract a contrast response function without the observers' response. We also found that contrast detection thresholds, measured behaviorally for different spatial frequencies, were highly and positively correlated (R = 0.87) with the microsaccade response time measured at high contrast (.4 times the threshold). These results show that different measures of microsaccade inhibition, especially the microsaccade response time, can provide accurate and involuntary measures of low-level visual properties such as contrast response and sensitivity. |
Ali Borji; Andreas Lennartz; Marc Pomplun What do eyes reveal about the mind? Algorithmic inference of search targets from fixations Journal Article In: Neurocomputing, vol. 149, pp. 788–799, 2015. @article{Borji2015, We address the question of inferring the search target from fixation behavior in visual search. Such inference is possible since during search, our attention and gaze are guided toward visual features similar to those in the search target. We strive to answer two fundamental questions: what are the most powerful algorithmic principles for this task, and how does their performance depend on the amount of available eye movement data and the complexity of the target objects? In the first two experiments, we choose a random-dot search paradigm to eliminate contextual influences on search. We present an algorithm that correctly infers the target pattern up to 50 times as often as a previously employed method and promises sufficient power and robustness for interface control. Moreover, the current data suggest a principal limitation of target inference that is crucial for interface design: if the target pattern exceeds a certain spatial complexity level, only a subpattern tends to guide the observers' eye movements, which drastically impairs target inference. In the third experiment, we show that it is possible to predict search targets in natural scenes using pattern classifiers and classic computer vision features significantly above chance. The availability of compelling inferential algorithms could initiate a new generation of smart, gaze-controlled interfaces and wearable visual technologies that deduce from their users' eye movements the visual information for which they are looking. In a broader perspective, our study shows directions for efficient intent decoding from eye movements. |
Tobias Bormann; Sascha A. Wolfer; Wibke Hachmann; Claudia Neubauer; Lars Konieczny Fast word reading in pure alexia: “Fast, yet serial” Journal Article In: Neurocase, vol. 21, no. 2, pp. 251–267, 2015. @article{Bormann2015, Pure alexia is a severe impairment of word reading in which individuals process letters serially with a pronounced length effect. Yet, there is considerable variation in the performance of alexic readers with generally very slow, but also occasionally fast responses, an observation addressed rarely in previous reports. It has been suggested that "fast" responses in pure alexia reflect residual parallel letter processing or that they may even be subserved by an independent reading system. Four experiments assessed fast and slow reading in a participant (DN) with pure alexia. Two behavioral experiments investigated frequency, neighborhood, and length effects in forced fast reading. Two further experiments measured eye movements when DN was forced to read quickly, or could respond faster because words were easier to process. Taken together, there was little support for the proposal that "qualitatively different" mechanisms or reading strategies underlie both types of responses in DN. Instead, fast responses are argued to be generated by the same serial-reading strategy. |
Maria Matziridi; Eli Brenner; Jeroen B. J. Smeets The role of temporal information in perisaccadic mislocalization Journal Article In: PLoS ONE, vol. 10, no. 9, pp. e0134081, 2015. @article{Matziridi2015, In dynamic environments, it is crucial to accurately consider the timing of information. For instance, during saccades the eyes rotate so fast that even small temporal errors in relating retinal stimulation by flashed stimuli to extra-retinal information about the eyes' orientations will give rise to substantial errors in where the stimuli are judged to be. If spatial localization involves judging the eyes' orientations at the estimated time of the flash, we should be able to manipulate the pattern of mislocalization by altering the estimated time of the flash. We reasoned that if we presented a relevant flash within a short rapid sequence of irrelevant flashes, participants' estimates of when the relevant flash was presented might be shifted towards the centre of the sequence. In a first experiment, we presented five bars at different positions around the time of a saccade. Four of the bars were black. Either the second or the fourth bar in the sequence was red. The task was to localize the red bar. We found that when the red bar was presented second in the sequence, it was judged to be further in the direction of the saccade than when it was presented fourth in the sequence. Could this be because the red bar was processed faster when more black bars preceded it? In a second experiment, a red bar was either presented alone or followed by two black bars. When two black bars followed it, it was judged to be further in the direction of the saccade. We conclude that the spatial localization of flashed stimuli involves judging the eye orientation at the estimated time of the flash. |
Gerrit W. Maus; Elena Potapchuk; Scott N. J. Watamaniuk; Stephen J. Heinen Different time scales of motion integration for anticipatory smooth pursuit and perceptual adaptation Journal Article In: Journal of Vision, vol. 15, no. 2, pp. 16–16, 2015. @article{Maus2015, When repeatedly exposed to moving stimuli, the oculomotor system elicits anticipatory smooth pursuit (ASP) eye movements, even before the stimulus moves. ASP is affected oppositely to perceptual speed judgments of repetitive moving stimuli: After a sequence of fast stimuli, ASP velocity increases, whereas perceived speed decreases. These two effects-perceptual adaptation and oculomotor priming-could result from adapting a single common internal speed representation that is used for perceptual comparisons and for generating ASP. Here we test this hypothesis by assessing the temporal dependence of both effects on stimulus history. Observers performed speed discriminations on moving random dot stimuli, either while pursuing the movement or maintaining steady fixation. In both cases, responses showed perceptual adaptation: Stimuli preceded by fast speeds were perceived as slower, and vice versa. To evaluate oculomotor priming, we analyzed ASP velocity as a function of average stimulus speed in preceding trials and found strong positive dependencies. Interestingly, maximal priming occurred over short stimulus histories (~two trials), whereas adaptation was maximal over longer histories (~15 trials). The temporal dissociation of adaptation and priming suggests different underlying mechanisms. It may be that perceptual adaptation integrates over a relatively long period to robustly calibrate the operating range of the motion system, thereby avoiding interference from transient changes in stimulus speed. On the other hand, the oculomotor system may rapidly prime anticipatory velocity to efficiently match it to that of the pursuit target. |
Bastian Mayerhofer; Annekathrin Schacht From incoherence to mirth: Neuro-cognitive processing of garden-path jokes Journal Article In: Frontiers in Psychology, vol. 6, pp. 550, 2015. @article{Mayerhofer2015, In so-called garden-path jokes, an initial semantic representation is violated, and semantic revision reestablishes a coherent representation. 48 jokes were manipulated in three conditions: (i) a coherent ending, (ii) a joke ending, and (iii) a discourse-incoherent ending. A reading times study (N =24) and three studies with recordings of ERP and pupil changes (N = 21, 24, and 24, respectively) supported the hypothesized cognitive processes. Jokes showed increased reading times of the final word compared to coherent endings. ERP data mainly indicated semantic integration difficulties (N400). Larger pupil diameters to joke endings presumably reflect emotional responses. ERP evidence for increased discourse processing efforts and emotional responses, as assumed to be reflected in late left anterior negativity and LLAN modulations and an enhanced late frontal positivity (fP600), respectively, remains however incomplete. Processing of incoherent endings was also accompanied by increased reading times, a stronger and sustained N400, and context-sensitive P600 effects. Together, these findings provide evidence for a sequential, non-monotonic, and incremental discourse comprehension of garden-path jokes. |
J. Patrick Mayo; Amie R. DiTomasso; Marc A. Sommer; Matthew A. Smith Dynamics of visual receptive fields in the macaque frontal eye field Journal Article In: Journal of Neurophysiology, vol. 114, no. 6, pp. 3201–3210, 2015. @article{Mayo2015, Neuronal receptive fields (RFs) provide the foundation for understanding systems-level sensory processing. In early visual areas, investigators have mapped RFs in detail using stochastic stimuli and sophisticated analytical approaches. Much less is known about RFs in prefrontal cortex. Visual stimuli used for mapping RFs in prefrontal cortex tend to cover a small range of spatial and temporal parameters, making it difficult to understand their role in visual processing. To address these shortcomings, we implemented a generalized linear model to measure the RFs of neurons in the macaque frontal eye field (FEF) in response to sparse, full-field stimuli. Our high-resolution, probabilistic approach tracked the evolution of RFs during passive fixation, and we validated our results against conventional measures. We found that FEF neurons exhibited a surprising level of sensitivity to stimuli presented as briefly as 10 ms or to multiple dots presented simultaneously, suggesting that FEF visual responses are more precise than previously appreciated. FEF RF spatial structures were largely maintained over time and between stimulus conditions. Our results demonstrate that the application of probabilistic RF mapping to FEF and similar association areas is an important tool for clarifying the neuronal mechanisms of cognition. |
Michael B. McCamy; Jorge Otero-Millan; R. John Leigh; Susan A. King; Rosalyn M. Schneider; Stephen L. Macknik; Susana Martinez-Conde Simultaneous recordings of human microsaccades and drifts with a contemporary video eye tracker and the search coil technique Journal Article In: PLoS ONE, vol. 10, no. 6, pp. e0128428, 2015. @article{McCamy2015, Human eyes move continuously, even during visual fixation. These " fixational eye move-ments " (FEMs) include microsaccades, intersaccadic drift and oculomotor tremor. Re-search in human FEMs has grown considerably in the last decade, facilitated by the manufacture of noninvasive, high-resolution/speed video-oculography eye trackers. Due to the small magnitude of FEMs, obtaining reliable data can be challenging, however, and de-pends critically on the sensitivity and precision of the eye tracking system. Yet, no study has conducted an in-depth comparison of human FEM recordings obtained with the search coil (considered the gold standard for measuring microsaccades and drift) and with contempo-rary, state-of-the art video trackers. Here we measured human microsaccades and drift si-multaneously with the search coil and a popular state-of-the-art video tracker. We found that 95% of microsaccades detected with the search coil were also detected with the video tracker, and 95% of microsaccades detected with video tracking were also detected with the search coil, indicating substantial agreement between the two systems. Peak/mean ve-locities and main sequence slopes of microsaccades detected with video tracking were sig-nificantly higher than those of the same microsaccades detected with the search coil, however. Ocular drift was significantly correlated between the two systems, but drift speeds were higher with video tracking than with the search coil. Overall, our combined results suggest that contemporary video tracking now approaches the search coil for measuring FEMs. |
Carol McDonald Connor; Ralph Radach; Christian Vorstius; Stephanie L. Day; Leigh McLean; Frederick J. Morrison Individual differences in fifth graders' literacy and academic language predict comprehension monitoring development: An eye-movement study Journal Article In: Scientific Studies of Reading, vol. 19, no. 2, pp. 114–134, 2015. @article{McDonaldConnor2015, In this study, we investigated fifth graders' (n = 52) fall literacy, academic language, and motivation and how these skills predicted fall and spring comprehension monitoring on an eye movement task. Comprehension monitoring was defined as the identification and repair of misunderstandings when reading text. In the eye movement task, children read two sentences; the second included either a plausible or implausible word in the context of the first sentence. Stronger readers had shorter reading times overall suggesting faster processing of text. Generally fifth graders reacted to the implausible word (i.e., longer gaze duration on the implausible vs. the plausible word, which reflects lexical access). Students with stronger academic language, compared to those with weaker academic language, generally spent more time rereading the implausible target compared to the plausible target. This difference increased from fall to spring. Results support the centrality of academic language for meaning integration, setting standards of coherence, and utilizing comprehension repair strategies. |
Gerald P. McDonnell; Mark Mills; Leslie McCuller; Michael D. Dodd How does implicit learning of search regularities alter the manner in which you search? Journal Article In: Psychological Research, vol. 79, no. 2, pp. 183–193, 2015. @article{McDonnell2015, Individuals are highly sensitive to statistical regularities in their visual environment, even when these patterns do not reach conscious awareness. Here, we examine whether oculomotor behavior is systematically altered when distractor/target configurations rarely repeat, but target location on an initial trial predicts the location of a target on the subsequent trial. The purpose of the current study was to explore whether this temporal-spatial contextual cueing in a conjunction search task influences both reaction time to the target and participant's search strategy. Participants searched for a target through a gaze-contingent window in a display consisting of a large number of distractors, providing a target-present/absent response. Participants were faster to respond to the target on the predicted trial relative to the predictor trial in an implicit contextual cueing task but were no more likely to fixate first to the target quadrant on the predicted trial (Experiment 1). Furthermore, implicit learning was interrupted when instructing participants to vary their searching strategy across trials to eliminate visual scan similarity (Experiment 2). In Experiment 3, when participants were explicitly informed that a pattern was present at the start of the experiment, explicit learning was observed in both reaction time and eye movements. The present experiments provide evidence that implicit learning of sequential regularities regarding target locations is not based on learning more efficient scan paths, but is due to some other mechanism. |
Victoria A. McGowan; Sarah J. White; Kevin B. Paterson The effects of interword spacing on the eye movements of young and older readers Journal Article In: Journal of Cognitive Psychology, vol. 27, no. 5, pp. 609–621, 2015. @article{McGowan2015, Recent evidence indicates that older adults (aged 65+) are more disrupted by removing interword spaces than young adults (aged 18–30). However, it is not known whether older readers also show greater sensitivity to the more subtle changes to this spacing that frequently occur during normal reading. In the present study the eye movements of young and older adults were examined when reading texts for which interword spacing was normal, condensed to half its normal size or expanded to 1.5 times its normal size. Although these changes in interword spacing affected eye movement behaviour, this influence did not differ between young and older adults. Furthermore, a word frequency manipulation showed that these changes did not affect word identification for either group. The results indicate that older adults can adapt their eye moment behaviour to accommodate subtle changes in the spatial layout of text equally effectively as young adults. |
David B. T. McMahon; Brian E. Russ; Heba D. Elnaiem; Anastasia I. Kurnikova; David A. Leopold Single-unit activity during natural vision: Diversity, consistency, and spatial sensitivity among AF face patch neurons Journal Article In: Journal of Neuroscience, vol. 35, no. 14, pp. 5537–5548, 2015. @article{McMahon2015, Several visual areas within the STS of the macaque brain respond strongly to faces and other biological stimuli. Determining the principles that govern neural responses in this region has proven challenging, due in part to the inherently complex stimulus domain of dynamic biological stimuli that are not captured by an easily parameterized stimulus set. Here we investigated neural responses in one fMRI-defined face patch in the anterior fundus (AF) of the STS while macaques freely view complex videos rich with natural social content. Longitudinal single-unit recordings allowed for the accumulation of each neuron's responses to repeated video presentations across sessions. We found that individual neurons, while diverse in their response patterns, were consistently and deterministically driven by the video content. We used principal component analysis to compute a family of eigenneurons, which summarized 24% of the shared population activity in the first two components. We found that the most prominent component of AF activity reflected an interaction between visible body region and scene layout. Close-up shots of faces elicited the strongest neural responses, whereas far away shots of faces or close-up shots of hindquarters elicited weak or inhibitory responses. Sensitivity to the apparent proximity of faces was also observed in gamma band local field potential. This category-selective sensitivity to spatial scale, together with the known exchange of anatomical projections of this area with regions involved in visuospatial analysis, suggests that the AF face patch may be specialized in aspects of face perception that pertain to the layout of a social scene. |
Xiaofan Peng; Maoyang Zhang; Dajun Zhang; Deguang Xie; Yusheng Guan From anger to attribution: Could attention be a bridge? Journal Article In: Social Behavior and Personality, vol. 43, no. 3, pp. 505–518, 2015. @article{Peng2015, We explored whether or not anger increases attribution bias toward salient information by narrowing attention scope. In Experiment 1, participants made attributions about 6 daily events while experiencing anger or in a neutral state. The anger group was more biased toward the salient factor compared to the neutral group. Using eye-tracking methodology, in Experiment 2 we further demonstrated that attention scope that is narrowed due to anger is related to a polarized distribution of attention resources, particularly decreased eye fixation on the phrase containing nonsalient factors. Finally, in Experiment 3 we separated attention process from information salience and further confirmed that narrowing attention scope (polarizing attention resource) could bias the attribution. In sum, our results indicate that attention scope is the bridge by which anger increases attribution bias. |
Manuel Perea; María Jiménez; Miguel Martín-Suesta; Pablo Gómez Letter position coding across modalities: Braille and sighted reading of sentences with jumbled words Journal Article In: Psychonomic Bulletin & Review, vol. 22, no. 2, pp. 531–536, 2015. @article{Perea2015, This article explores how letter position coding is attained during braille reading and its implications for models of word recognition. When text is presented visually, the reading process easily adjusts to the jumbling of some letters (jugde-judge), with a small cost in reading speed. Two explanations have been proposed: One relies on a general mechanism of perceptual uncertainty at the visual level, and the other focuses on the activation of an abstract level of representation (i.e., bigrams) that is shared by all orthographic codes. Thus, these explanations make differential predictions about reading in a tactile modality. In the present study, congenitally blind readers read sentences presented on a braille display that tracked the finger position. The sentences either were intact or involved letter transpositions. A parallel experiment was conducted in the visual modality. Results revealed a substantially greater reading cost for the sentences with transposed-letter words in braille readers. In contrast with the findings with sighted readers, in which there is a cost of transpositions in the external (initial and final) letters, the reading cost in braille readers occurs serially, with a large cost for initial letter transpositions. Thus, these data suggest that the letter-position-related effects in visual word recognition are due to the characteristics of the visual stream. |
Manuel Perea; Pilar Tejero; Heather Winskel Can colours be used to segment words when reading? Journal Article In: Acta Psychologica, vol. 159, pp. 8–13, 2015. @article{Perea2015a, Rayner, Fischer, and Pollatsek (1998, Vision Research) demonstrated that reading unspaced text in Indo-European languages produces a substantial reading cost in word identification (as deduced from an increased word-frequency effect on target words embedded in the unspaced vs. spaced sentences) and in eye movement guidance (as deduced from landing sites closer to the beginning of the words in unspaced sentences). However, the addition of spaces between words comes with a cost: nearby words may fall outside high-acuity central vision, thus reducing the potential benefits of parafoveal processing. In the present experiment, we introduced a salient visual cue intended to facilitate the process of word segmentation without compromising visual acuity: each alternating word was printed in a different colour (i.e., ). Results only revealed a small reading cost of unspaced alternating colour sentences relative to the spaced sentences. Thus, present data are a demonstration that colour can be useful to segment words for readers of spaced orthographies. |
Laura Pérez Zapata; Maria Solé Puig; Jose Antonio Aznar-Casanova; Hans Supèr Evidence for a role of corrective eye movements during gaze fixation in saccade planning Journal Article In: European Journal of Neuroscience, vol. 41, no. 2, pp. 227–233, 2015. @article{PerezZapata2015, In a three-dimensional (3D) world most saccades are made towards visual targets that are located at different distances. We previously demonstrated that gaze shifts within 3D space consist of two stages: a target saccade followed by a corrective saccade during gaze fixation that directs the eyes to the physical target location. We proposed that, by accurately positioning the eyes on the visual object, the visual system maintains an orderly representation of the visual world. In this study we used a double saccade experiment to assess the function of corrective saccades in humans. We found that, when a corrective eye movement occurred during fixation on the first target point, the direction of the second saccade towards the next target point was accurate. When a corrective saccade was absent, a directional error of the second target saccade was observed. This finding, which cannot be explained by current models of eye movement control, supports the idea of a two-step model in saccade programming. We suggest that the motor system sends a corollary discharge when programming a corrective saccade for maintaining an orderly representation of the visual world. In conclusion, our results indicate that corrective saccades have a role in programming target saccades within 3D space. |
Jairo Perez-Osorio; Hermann J. Müller; Eva Wiese; Agnieszka Wykowska Gaze following is modulated by expectations regarding others' action goals Journal Article In: PLoS ONE, vol. 10, no. 11, pp. e0143614, 2015. @article{PerezOsorio2015, Humans attend to social cues in order to understand and predict others' behavior. Facial expressions and gaze direction provide valuable information to infer others' mental states and intentions. The present study examined the mechanism of gaze following in the context of participants' expectations about successive action steps of an observed actor. We embedded a gaze-cueing manipulation within an action scenario consisting of a sequence of naturalistic photographs. Gaze-induced orienting of attention (gaze following) was analyzed with respect to whether the gaze behavior of the observed actor was in line or not with the action-related expectations of participants (i.e., whether the actor gazed at an object that was congruent or incongruent with an overarching action goal). In Experiment 1, participants followed the gaze of the observed agent, though the gaze-cueing effect was larger when the actor looked at an action-congruent object relative to an incongruent object. Experiment 2 examined whether the pattern of effects observed in Experiment 1 was due to covert, rather than overt, attentional orienting, by requiring participants to maintain eye fixation throughout the sequence of critical photographs (corroborated bymonitoring eye movements). The essential pattern of results of Experiment 1 was replicated, with the gaze- cueing effect being completely eliminated when the observed agent gazed at an action-incongruent object. Thus, our findings show that covert gaze following can be modulated by expectations that humans hold regarding successive steps of the action performed by an observed agent. |
Benjamin Peters; Jochen Kaiser; Benjamin Rahm; Christoph Bledowski Activity in human visual and parietal cortex reveals object-based attention in working memory Journal Article In: Journal of Neuroscience, vol. 35, no. 8, pp. 3360–3369, 2015. @article{Peters2015, Visual attention enables observers to select behaviorally relevant information based on spatial locations, features, or objects. Attentional selection is not limited to physically present visual information, but can also operate on internal representations maintained in working memory (WM) in service of higher-order cognition. However, only little is known about whether attention to WM contents follows the same principles as attention to sensory stimuli. To address this question, we investigated in humans whether the typically observed effects of object-based attention in perception are also evident for object-based attentional selection of internal object representations in WM. In full accordance with effects in visual perception, the key behavioral and neuronal characteristics of object-based attention were observed in WM. Specifically, we found that reaction times were shorter when shifting attention to memory positions located on the currently attended object compared with equidistant positions on a different object. Furthermore, functional magnetic resonance imaging and multivariate pattern analysis of visuotopic activity in visual (areas V1-V4) and parietal cortex revealed that directing attention to one position of an object held in WM also enhanced brain activation for other positions on the same object, suggesting that attentional selection in WM activates the entire object. This study demonstrated that all characteristic features of object-based attention are present in WM and thus follows the same principles as in perception. |
Andrea M. Philipp; Lynn Huestegge Language switching between sentences in reading: Exogenous and endogenous effects on eye movements and comprehension Journal Article In: Bilingualism: Language and Cognition, vol. 18, no. 4, pp. 614–625, 2015. @article{Philipp2015, The present study explored the influence of language switching on both comprehension (utilizing a picture-sentence matching procedure) and word-level processing (utilizing eye movement registration) in reading simple German and English sentences. Language sequence was unpredictable and contained language switches (subsequent sentence in a different language) and language repetitions (subsequent sentence in the same language). The results revealed a substantial decrease of comprehension following language switches (with greater switch costs in L1 than in L2), likely indicating relatively long-lasting, endogenous inhibition processes affecting higher-level text integration. In contrast, there were comparatively minor and transient effects on eye movements (in terms of altered skipping probabilities and gaze durations) that were restricted to the initial words within a sentence, presumably representing short-lasting exogenous (stimulus-driven) activation effects after language switches (with greater switch costs in L2 than in L1). Overall, the results are in line with predictions from recent interactive-activation frameworks of bilingual language processing. |
Andrea Phillipou; Larry Allen Abel; David J. Castle; Matthew E. Hughes; Caroline T. Gurvich; Richard G. Nibbs; Susan Lee Rossell Self perception and facial emotion perception of others in anorexia nervosa Journal Article In: Frontiers in Psychology, vol. 6, pp. 1181, 2015. @article{Phillipou2015, BACKGROUND: Whether individuals with anorexia nervosa (AN) are able to accurately perceive emotions from faces of others is unclear. Furthermore, whether individuals with AN process images of their own face differently to healthy individuals has thus far not been investigated. Therefore, the aim of this study was to investigate facial affect processing and the processing of one's own face through measures of emotion identification, functional magnetic resonance imaging (fMRI) and eyetracking. METHODS: Twenty-four females with AN and 25 matched healthy control participants were presented with an implicit emotion processing task during fMRI and eyetracking, followed by an explicit emotion identification task. RESULTS: The AN group were found to 'hyperscan' stimuli and avoided visually attending to salient features of their own face images. RESULTS of the fMRI revealed increased activity to own face stimuli in AN in the right inferior and middle temporal gyri, and right lingual gyrus. AN participants were not found to display emotion identification deficits to the standard emotional face stimuli. DISCUSSION: The findings are discussed in terms of increased anxiety to disorder-relevant stimuli in AN. Potential clinical implications are discussed in relation to the use of eyetracking techniques to improve the perception of self in AN. |
Muriel T. N. Panouillères; R. Chris Miall; Ned Jenkinson The role of the posterior cerebellum in saccadic adaptation: A transcranial direct current stimulation study Journal Article In: Journal of Neuroscience, vol. 35, no. 14, pp. 5471–5479, 2015. @article{Panouilleres2015, The posterior vermis of the cerebellum is considered to be critically involved in saccadic adaptation. However, recent evidence suggests that the adaptive decrease (backward adaptation) and the adaptive increase (forward adaptation) of saccade amplitude rely on partially separate neural substrates. We investigated whether the posterior cerebellum could be differentially involved in backward and forward adaptation by using transcranial direct current stimulation (TDCS). To do so, participants' saccades were adapted backward or forward while they received anodal, cathodal, or sham TDCS. In two extra groups, subjects underwent a nonadaptation session while receiving anodal or cathodal TDCS to control for the direct effects of TDCS on saccadic execution. Surprisingly, cathodal stimulation tended to increase the extent of both forward and backward adaptations, while anodal TDCS strongly impaired forward adaptation and, to a smaller extent, backward adaptation. Forward adaptation was accompanied by a greater increase in velocity with cathodal stimulation, and reduced duration of change for anodal stimulation. In contrast, the expected velocity decrease in backward adaptation was noticeably weaker with anodal stimulation. Stimulation applied during nonadaptation sessions did not affect saccadic gain, velocity, or duration, demonstrating that the reported effects are not due to direct effects of the stimulation on the generation of eye movements. Our results demonstrate that cerebellar excitability is critical for saccadic adaptation. Based on our results and the growing evidence from studies of vestibulo-ocular reflex and saccadic adaptation, we conclude that the plasticity at the level of the oculomotor vermis is more fundamentally important for forward adaptation than for backward adaptation. |
Davide Paoletti; Matthew David Weaver; Christoph Braun; Wieske Zoest Trading off stimulus salience for identity: A cueing approach to disentangle visual selection strategies Journal Article In: Vision Research, vol. 113, pp. 116–124, 2015. @article{Paoletti2015, Recent studies show that time plays a primary role in determining whether visual selection is influenced by stimulus salience or guided by observers' intentions. Accordingly, when a response is made seems critically important in defining the outcome of selection. The present study investigates whether observers are able to control the timing of selection and regulate the trade-off between stimulus- and goal-driven influences. One experiment was conducted in which participants were asked to make a saccade to the target, a tilted bar embedded in a matrix of vertical lines. An additional distractor, more or less salient than the target, was presented concurrently with the search display. To manipulate when in time the response was given we cued participants before each trial to be either fast or accurate. Participants received periodic feedback regarding performance speed and accuracy. The results showed participants were able to control the timing of selection: the distribution of responses was relatively fast or slow depending on the cue. Performance in the fast-cue condition appeared to be primarily driven by stimulus salience, while in the accurate-cue condition saccades were guided by the search template. Examining the distribution of responses that temporally overlapped between the two cue conditions revealed a main effect of cue. This suggests the cue had an additional benefit to performance independent of the effect of salience. These findings show that although early selection may be constrained by stimulus salience, observers are flexible in guiding the 'when' signal and consequently establishing a trade-off between saliency and identity. |
Angelina Paolozza; Rebecca Munn; Douglas P. Munoz; James N. Reynolds Eye movements reveal sexually dimorphic deficits in children with fetal alcohol spectrum disorder Journal Article In: Frontiers in Neuroscience, vol. 9, pp. 76, 2015. @article{Paolozza2015, BACKGROUND: We examined the accuracy and characteristics of saccadic eye movements in children with fetal alcohol spectrum disorder (FASD) compared with typically developing control children. Previous studies have found that children with FASD produce saccades that are quantifiably different from controls. Additionally, animal studies have found sex-based differences for behavioral effects after prenatal alcohol exposure. Therefore, we hypothesized that eye movement measures will show sexually dimorphic results. METHODS: Children (aged 5-18 years) with FASD (n = 71) and typically developing controls (n = 113) performed a visually-guided saccade task. Saccade metrics and behavior were analyzed for sex and group differences. RESULTS: Female control participants had greater amplitude saccades than control males or females with FASD. Accuracy was significantly poorer in the FASD group, especially in males, which introduced significantly greater variability in the data. Therefore, we conducted additional analyses including only those trials in which the first saccade successfully reached the target within a ± 1° window. In this restricted amplitude dataset, the females with FASD made saccades with significantly lower velocity and longer duration, whereas the males with FASD did not differ from the control group. Additionally, the mean and peak deceleration were selectively decreased in the females with FASD. CONCLUSIONS: These data support the hypothesis that children with FASD exhibit specific deficits in eye movement control and sensory-motor integration associated with cerebellar and/or brain stem circuits. Moreover, prenatal alcohol exposure may have a sexually dimorphic impact on eye movement metrics, with males and females exhibiting differential patterns of deficit. |
David Pascucci; Tommaso Mastropasqua; Massimo Turatto Monetary reward modulates task-irrelevant perceptual learning for invisible stimuli Journal Article In: PLoS ONE, vol. 10, no. 5, pp. e0124009, 2015. @article{Pascucci2015a, Task Irrelevant Perceptual Learning (TIPL) shows that the brain's discriminative capacity can improve also for invisible and unattended visual stimuli. It has been hypothesized that this form of “unconscious” neural plasticity is mediated by an endogenous reward mechanism triggered by the correct task performance. Although this result has challenged the mandatory role of attention in perceptual learning, no direct evidence exists of the hypothesized link between target recognition, reward and TIPL. Here, we manipulated the reward value associated with a target to demonstrate the involvement of reinforcement mechanisms in sensory plasticity for invisible inputs. Participants were trained in a central task associated with either high or low monetary incentives, provided only at the end of the experiment, while subliminal stimuli were presented peripherally. Our results showed that high incentive-value targets induced a greater degree of perceptual improvement for the subliminal stimuli, supporting the role of reinforcement mechanisms in TIPL. |
David Pascucci; Massimo Turatto The distracting impact of repeated visible and invisible onsets on focused attention Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 41, no. 3, pp. 879–892, 2015. @article{Pascucci2015, A sudden peripheral onset is a powerful attentional attractor. However, in real life potentially distracting events do not always occur as a single event, but rather they can occur in a repetitive fashion. Hence, one of the aims of the present study was to investigate how the attentional system reacts to multiple consecutive onsets within the same trial. The results, quite surprisingly, showed that repeated peripheral onsets do not have a negative impact on visual performance, while they confirmed that a single peripheral onset captures focused attention. We hypothesize the existence of a short-term habituation mechanism that prevents visual attention from being continuously distracted by the same task-irrelevant event when this is rapidly repeated. A further aim of the study was to test the proposal according to which subliminal visual transients can bypass the conscious inhibitory control, thus resulting more distracting than supraliminal transients. We did not find in any of the 8 experiments that we conducted that subliminal onsets, either single or repeated, can grab attention when fully focused at fixation. Hence, in the case of sudden onsets, the general claim that task-irrelevant invisible stimuli can be more disturbing than visible ones does not seem to be fully justified. |
Kevin B. Paterson; Abubaker A. A. Almabruk; Victoria A. McGowan; Sarah J. White; Timothy R. Jordan Effects of word length on eye movement control: The evidence from Arabic Journal Article In: Psychonomic Bulletin & Review, vol. 22, no. 5, pp. 1443–1450, 2015. @article{Paterson2015, The finding that word length plays a fundamental role in determining where and for how long readers fixate within a line of text has been central to the development of sophisticated models of eye movement control. However, research in this area is dominated by the use of Latinate languages (e.g., English, French, German), and little is known about eye movement control for alphabetic languages with very different visual characteristics. To address this issue, the present experiment undertook a novel investigation of the influence of word length on eye movement behavior when reading Arabic. Arabic is an alphabetic language that not only is read from right to left but has visual characteristics fundamentally different from Latinate languages, and so is ideally suited to testing the generality of mechanisms of eye movement control. The findings reveal that readers were more likely to fixate and refixate longer words, and also that longer words tended to be fixated for longer. In addition, word length influenced the landing positions of initial fixations on words, with the effect that readers fixated the center of short words and fixated closer to the beginning letters for longer words, and the location of landing positions affected both the duration of the first fixation and probability of refixating the word. The indication now, therefore, is that effects of word length are a widespread and fundamental component of reading and play a central role in guiding eye-movement behavior across a range of very different alphabetic systems. |
Vivian C. Paulun; Alexander C. Schütz; Melchi M. Michel; Wilson S. Geisler; Karl R. Gegenfurtner Visual search under scotopic lighting conditions Journal Article In: Vision Research, vol. 113, pp. 155–168, 2015. @article{Paulun2015, When we search for visual targets in a cluttered background we systematically move our eyes around to bring different regions of the scene into foveal view. We explored how visual search behavior changes when the fovea is not functional, as is the case in scotopic vision. Scotopic contrast sensitivity is significantly lower overall, with a functional scotoma in the fovea. We found that in scotopic search, for a medium- and a low-spatial-frequency target, individuals made longer lasting fixations that were not broadly distributed across the entire search display but tended to peak in the upper center, especially for the medium-frequency target. The distributions of fixation locations are qualitatively similar to those of an ideal searcher that has human scotopic detectability across the visual field, and interestingly, these predicted distributions are different from those predicted by an ideal searcher with human photopic detectability. We conclude that although there are some qualitative differences between human and ideal search behavior, humans make principled adjustments in their search behavior as ambient light level decreases. |
Frieder M. Paulus; Sören Krach; Marius Blanke; Christine Roth; Marcus Belke; Jens Sommer; Laura Müller-Pinzler; Katja Menzler; Andreas Jansen; Felix Rosenow; Frank Bremmer; Wolfgang Einhäuser; Susanne Knake Fronto-insula network activity explains emotional dysfunctions in juvenile myoclonic epilepsy: Combined evidence from pupillometry and fMRI Journal Article In: Cortex, vol. 65, pp. 219–231, 2015. @article{Paulus2015, Emotional instability, difficulties in social adjustment, and disinhibited behavior are the most common symptoms of the psychiatric comorbidities in juvenile myoclonic epilepsy (JME). This psychopathology has been associated with dysfunctions of mesial-frontal brain circuits. The present work is a first direct test of this link and adapted a paradigm for probing frontal circuits during empathy for pain. Neural and psychophysiological parameters of pain empathy were assessed by combining functional magnetic resonance imaging (fMRI) with simultaneous pupillometry in 15 JME patients and 15 matched healthy controls. In JME patients, we observed reduced neural activation of the anterior cingulate cortex (ACC), the anterior insula (AI), and the ventrolateral prefrontal cortex (VLPFC). This modulation was paralleled by reduced pupil dilation during empathy for pain in patients. At the same time, pupil dilation was positively related to neural activity of the ACC, AI, and VLPFC. In JME patients, the ACC additionally showed reduced functional connectivity with the primary and secondary somatosensory cortex, areas fundamentally implicated in processing the somatic cause of another's pain. Our results provide first evidence that alterations of mesial-frontal circuits directly affect psychosocial functioning in JME patients and draw a link of pupil dynamics with brain activity during emotional processing. The findings of reduced pain empathy related activation of the ACC and AI and aberrant functional integration of the ACC with somatosensory cortex areas provide further evidence for this network's role in social behavior and helps explaining the JME psychopathology and patients' difficulties in social adjustment. |
Guojie Ma; Xingshan Li; Alexander Pollatsek There is no relationship between preferred viewing location and word segmentation in Chinese reading Journal Article In: Visual Cognition, vol. 23, no. 3, pp. 399–414, 2015. @article{Ma2015b, In Chinese, as there are no spaces between words to mark word boundaries, readers usually do not target their eyes to the centre of the word as readers of English do. Previous studies showed that the distribution of the initial landing positions on a word (the PVL curve) peaked at the beginning of a word when there was more than one fixation; but peaked at the centre of a word if there was only one fixation on the word. Based on this phenomenon, it was argued that Chinese readers move their eyes to the beginning of a word if they cannot correctly segment words in the parafovea, but move to the centre of a word if they can. In the present study, we implemented a natural sentence reading task in Experiment 1 and a shuffled-character reading task in Experiment 2 to test whether the above PVL phenomenon was in fact caused by word segmentation. In both experiments, we found that the different PVL patterns in multiple- and single-fixation cases occurred not only for a 3-character word region but also for a 3-character nonword region. These results suggest that the different PVL curves in multiple- and single-fixation cases are likely to be due to a statistical artefact instead of parafoveal word segmentation. |
Guojie Ma; Xingshan Li; Keith Rayner Readers extract character frequency information from nonfixated-target word at long pretarget fixations during Chinese reading Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 41, no. 5, pp. 1409–1419, 2015. @article{Ma2015c, We performed 2 eye movement studies to explore whether readers can extract character or word frequency information from nonfixated-target words in Chinese reading. In Experiments 1A and 1B, we manipulated the character frequency of the first character in a 2-character target word and the word frequency of a 2-character target word, respectively. We found that fixation durations on the pretarget words were shorter when the first character of a 2-character target word was presented with high frequency. Such effects were not observed for word frequency manipulations of a 2-character target word. In particular, further analysis revealed that such effects only occurred for long pretarget fixations. These results for character and word frequency manipulations were replicated in a within-subjects design in Experiment 2. These findings are generally consistent with the notion that characters are processed in parallel during Chinese reading. However, we did not find evidence that words are processed in parallel during Chinese reading. |
Min-Yuan Ma; Hsien-Chih Chuang How form and structure of Chinese characters affect eye movement control Min-Yuan Journal Article In: Journal of Eye Movement Research, vol. 8, no. 3, pp. 1–12, 2015. @article{Ma2015, This study investigated the correlations between the form features and legibility of Chinese characters by employing the eye tracking method in two experiments: Experiment 1 examined factors affecting Chinese character legibility with character modules and identified the correlations between character form and legibility of crossing strokes; and Experiment 2 examined the effect of crossing strokes on subjective complicacy perception in both Chinese characters and English letters. This study determined that enclosed Chinese characters affect subjective complicacy perception and reduce saccadic amplitude. In addition, greater number of stroke crossings produced higher subjective complicacy perceived for both Chinese characters and English letters. The results of this study serve as a reference for predicting Chinese character legibility and assessing type design superiority. |
Min-Yuan Ma; Hsien-Chih Chuang A legibility study of Chinese character complicacy and eye movement data Journal Article In: Perceptual and Motor Skills, vol. 120, no. 1, pp. 232–246, 2015. @article{Ma2015a, This study investigated the correlations between the complicacy and legibility of Chinese characters by using eye tracking analyzed with structural equation modeling. 13 university students, 6 men and 7 women, with a mean age of 21 yr. (SD = 1.7) participated. The results indicated that block types affected legibility and that saccade amplitude, number of fixations, and complicacy differed due to diverse character structures. Structural Equation Modeling showed that the number of strokes, number of nodes, and image density in stroke complicacy affected the number of fixations and saccade amplitude in eye movement data. Constructing a character complicacy and eye tracking information model to investigate the correlations between Chinese character features and human viewing behavior can provide guidance for Chinese character recognizability and type design. |
W. Joseph MacInnes; Hannah M. Krüger; Amelia R. Hunt Just passing through? Inhibition of return in saccadic sequences Journal Article In: Quarterly Journal of Experimental Psychology, vol. 68, no. 2, pp. 402–416, 2015. @article{MacInnes2015, Responses tend to be slower to previously fixated spatial locations, an effect known as "inhibition of return" (IOR). Saccades cannot be assumed to be independent, however, and saccade sequences programmed in parallel differ from independent eye movements. We measured the speed of both saccadic and manual responses to probes appearing in previously fixated locations when those locations were fixated as part of either parallel or independent saccade sequences. Saccadic IOR was observed in independent but not parallel saccade sequences, while manual IOR was present in both parallel and independent sequence types. Saccadic IOR was also short-lived, and dissipated with delays of more than ∼1500 ms between the intermediate fixation and the probe onset. The results confirm that the characteristics of IOR depend critically on the response modality used for measuring it, with saccadic and manual responses giving rise to motor and attentional forms of IOR, respectively. Saccadic IOR is relatively short-lived and is not observed at intermediate locations of parallel saccade sequences, while attentional IOR is long-lasting and consistent for all sequence types. |
Andrew K. Mackenzie; Julie M. Harris Eye movements and hazard perception in active and passive driving Journal Article In: Visual Cognition, vol. 23, no. 6, pp. 736–757, 2015. @article{Mackenzie2015, Differences in eye movement patterns are often found when comparing passive viewing paradigms to actively engaging in everyday tasks. Arguably, investigations into visuomotor control should therefore be most useful when conducted in settings that incorporate the intrinsic link between vision and action. We present a study that compares oculomotor behaviour and hazard reaction times across a simulated driving task and a comparable, but passive, video-based hazard perception task. We found that participants scanned the road less during the active driving task and fixated closer to the front of the vehicle. Participants were also slower to detect the hazards in the driving task. Our results suggest that the interactivity of simulated driving places increased demand upon the visual and attention systems than simply viewing driving movies. We offer insights into why these differences occur and explore the possible implications of such findings within the wider context of driver training and assessment. |
Diane E. MacKenzie; David A. Westwood Investigating visual attention during scene perception of safe and unsafe occupational performance Journal Article In: Canadian Journal of Occupational Therapy, vol. 82, no. 4, pp. 224–234, 2015. @article{MacKenzie2015b, Background. Occupational therapists routinely use observation for evaluation, intervention planning, and prediction of a client's occupational performance and/or safety within the environment. Perception of safety contributes to the decision-making process for discharge or placement recommendations. Purpose. The purpose of this study was to determine if differences exist in safety ratings and eye movements between occupational therapists and nontrained matched individuals while viewing domain-specific versus non-domain-specific images. Method. Ten licensed occupational therapists and 10 age-, gender-, and education level–matched participants completed this eye-tracking study. Findings. For all image exposure durations, occupational therapists had more polarized safety ratings for stroke-related image content but little evidence of differences in eye movements between groups. Eye movement group differences did not emerge in the regions of interest identified by an independent expert panel. Implications. The results point to a complex relationship between decision making and observational behaviour in occupational assessment and highlight the need to look beyond image features. |
Gregory H. MacLean; Raymond M. Klein; Matthew D. Hilchey Does oculomotor readiness mediate exogenous capture of visual attention? Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 41, no. 5, pp. 1260–1270, 2015. @article{MacLean2015, The oculomotor readiness hypothesis makes 2 predictions: Shifts in covert attention are accompanied by preparedness to move one's eyes to the attended region, and preparedness to move one's eyes to a region in space is accompanied by a shift in covert attention to the prepared location. Both predictions have been disconfirmed using an endogenous attention task. In the 2 experiments presented here, the same 2 predictions were tested using an exogenous attention task. It was found that participants experienced covert capture without accompanying oculomotor activation and experienced oculomotor activation without accompanying covert capture. While under everyday conditions the overt and covert orienting systems may be strongly linked, apparently they can nonetheless operate with a high degree of independence from one another. |
Mary H. Maclean; Barry Giesbrecht Neural evidence reveals the rapid effects of reward history on selective attention Journal Article In: Brain Research, vol. 1606, pp. 86–94, 2015. @article{Maclean2015b, Selective attention is often framed as being primarily driven by two factors: task-relevance and physical salience. However, factors like selection and reward history, which are neither currently task-relevant nor physically salient, can reliably and persistently influence visual selective attention. The current study investigated the nature of the persistent effects of irrelevant, physically non-salient, reward-associated features. These features affected one of the earliest reliable neural indicators of visual selective attention in humans, the P1 event-related potential, measured one week after the reward associations were learned. However, the effects of reward history were moderated by current task demands. The modulation of visually evoked activity supports the hypothesis that reward history influences the innate salience of reward associated features, such that even when no longer relevant, nor physically salient, these features have a rapid, persistent, and robust effect on early visual selective attention. |
Najib J. Majaj; Ha Hong; Ethan A. Solomon; James J. DiCarlo Simple learned weighted sums of inferior temporal neuronal firing rates accurately predict human core object recognition performance Journal Article In: Journal of Neuroscience, vol. 35, no. 39, pp. 13402–13418, 2015. @article{Majaj2015, To go beyond qualitative models of the biological substrate of object recognition, we ask: can a single ventral stream neuronal linking hypothesis quantitatively account for core object recognition performance over a broad range of tasks? We measured human performance in 64 object recognition tests using thousands ofchallenging images that explore shape similarity and identity preserving object variation. We then used multielectrode arrays to measure neuronal population responses to those same images in visual areas V4 and inferior temporal (IT) cortex ofmonkeys and simulated V1 population responses. We tested leading candidate linking hypotheses and control hypotheses, each postulating how ventral stream neuronal responses underlie object recognition behavior. Specifically, for each hypothesis, we computed the predicted performance on the 64 tests and compared it with the measured pattern ofhuman performance. All tested hypotheses based on low- and mid-level visually evoked activity (pixels, V1, and V4) were very poor predictors ofthe human behavioral pattern. However, simple learned weighted sums of distributed average IT firing rates exactly predicted the behavioral pattern. More elaborate linking hypotheses relying on IT trial-by-trial correlational structure, finer IT temporal codes, or ones that strictly respect the known spatial substructures ofIT (“face patches”) did not improve predictive power. Although these results do not reject those more elaborate hypotheses, they suggest a simple, sufficient quantitative model: each object recognition task is learned from the spatially distributed mean firing rates (100 ms) of ~60,000 IT neurons and is executed as a simple weighted sum ofthose firing rates. |
Alex J. Major; Susheel Vijayraghavan; Stefan Everling Muscarinic attenuation of mnemonic rule representation in macaque dorsolateral prefrontal cortex during a pro-and anti-saccade task Journal Article In: Journal of Neuroscience, vol. 35, no. 49, pp. 16064–16076, 2015. @article{Major2015, Maintenance of context is necessary for execution of appropriate responses to diverse environmental stimuli. The dorsolateral prefrontal cortex (DLPFC) plays a pivotal role in executive function, including working memory and representation ofabstract rules. DLPFC activity is modulated by the ascending cholinergic system through nicotinic and muscarinic receptors. Although muscarinic receptors have been implicated in executive performance and gating ofsynaptic signals, their effect on local primate DLPFC neuronal activity in vivo during cognitive tasks remains poorly understood. Here, we examined the effects of muscarinic receptor blockade on rule-related activity in the macaque prefrontal cortex by combining iontophoretic application of the general muscarinic receptor antagonist scopolamine with single-cell recordings while monkeys performed a mnemonic rule-guided saccade task. We found that scopolamine reduced overall neuronal firing rate and impaired rule discriminability of task-selective cells. Saccade and visual direction selectivity measures were also reduced by muscarinic antagonism. These results demonstrate that blockade of muscarinic receptors in DLPFC creates deficits in working memory representation of rules in primates. |
Elena Makovac; Antimo Buonocore; Robert D. McIntosh Audio-visual integration and saccadic inhibition Journal Article In: Quarterly Journal of Experimental Psychology, vol. 68, no. 7, pp. 1295–1305, 2015. @article{Makovac2015, Saccades operate a continuous selection between competing targets at different locations. This competition has been mostly investigated in the visual context, and it is well known that a visual distractor can interfere with a saccade toward a visual target. Here, we investigated whether multimodal, audio-visual targets confer stronger resilience against visual distraction. Saccades to audio-visual targets had shorter latencies than saccades to unisensory stimuli. This facilitation exceeded the level that could be explained by simple probability summation, indicating that multisensory integration had occurred. The magnitude of inhibition induced by a visual distractor was comparable for saccades to unisensory and multisensory targets, but the duration of the inhibition was shorter for multimodal targets. We conclude that multisensory integration can allow a saccade plan to be reestablished more rapidly following saccadic inhibition. |
Raphaëlle Malassis; Antoine Del Cul; Thérèse Collins Corollary discharge failure in an oculomotor task is related to delusional ideation in healthy Individuals Journal Article In: PLoS ONE, vol. 10, no. 8, pp. e0134483, 2015. @article{Malassis2015, Predicting the sensory consequences of saccadic eye movements likely plays a crucial role in planning sequences of saccades and in maintaining visual stability despite saccade- caused retinal displacements. Deficits in predictive activity, such as that afforded by a corol- lary discharge signal, have been reported in patients with schizophrenia, and may lead to the emergence of positive symptoms, in particular delusions of control and auditory halluci- nations. We examined whether a measure of delusional thinking in the general, non-clinical population correlated with measures of predictive activity in two oculomotor tasks. The double-step task measured predictive activity in motor control, and the in-flight displace- ment task measured predictive activity in trans-saccadic visual perception. Forty-one healthy adults performed both tasks and completed a questionnaire to assess delusional thinking. The quantitative measure of predictive activity we obtained correlated with the ten- dency towards delusional ideation, but only for the motor task, and not the perceptual task: Individuals with higher levels of delusional thinking showed less self-movement information use in the motor task. Variation of the degree of self-generated movement knowledge as a function of the prevalence of delusional ideation in the normal population strongly supports the idea that corollary discharge deficits measured in schizophrenic patients in previous researches are not due to neuroleptic medication. We also propose that this difference in results between the perceptual and the motor tasks may point to a dissociation between cor- ollary discharge for perception and corollary discharge for action. |
George L. Malcolm; Sarah Shomstein Object-based attention in real-world scenes. Journal Article In: Journal of Experimental Psychology: General, vol. 144, no. 2, pp. 257–263, 2015. @article{Malcolm2015, We are continually confronted with more visual information than we can process in a given moment. In order to interact effectively with our environment, attentional mechanisms are used to select subsets of environmental properties for enhanced processing. Previous research demonstrated that spatial regions can be selected based on either their low-level feature or high-level semantic properties. However, the efficiency with which we interact with the world suggests that there must be an additional, midlevel, factor constraining effective attentional space. The present study investigates whether object-based attentional selection is one such midlevel factor that constrains visual attention in complex, real-world scenes. Participants viewed scene images while their eye movements were recorded. During viewing, a cue appeared on an object which participants were instructed to fixate. A target then appeared either on the same object as the cue, on a different object, or floating. Participants initiated saccades faster and had shorter response times to targets presented on the same object as the fixated cue. The results strongly suggest that when attending to a location on an object, the entire object benefits perceptually. This object-based effect on the distribution of spatial attention forms a critical link between low- and high-level factors that direct attention efficiently in complex real-world scenes. |
Pankhuri Malik; Joost C. Dessing; J. Douglas Crawford Role of early visual cortex in trans-saccadic memory of object features Journal Article In: Journal of Vision, vol. 15, no. 7, pp. 1–17, 2015. @article{Malik2015, Early visual cortex (EVC) participates in visual feature memory and the updating of remembered locations across saccades, but its role in the trans-saccadic integration of object features is unknown. We hypothesized that if EVC is involved in updating object features relative to gaze, feature memory should be disrupted when saccades remap an object representation into a simultaneously perturbed EVC site. To test this, we applied transcranial magnetic stimulation (TMS) over functional magnetic resonance imaging–localized EVC clusters corresponding to the bottom left/right visual quadrants (VQs). During experiments, these VQs were probed psychophysically by briefly presenting a central object (Gabor patch) while subjects fixated gaze to the right or left (and above). After a short memory interval, participants were required to detect the relative change in orientation of a re-presented test object at the same spatial location. Participants either sustained fixation during the memory interval (fixation task)ormade a horizontal saccade that either maintained or reversed the VQ of the object (saccade task). Three TMS pulses (coinciding with the pre-, peri-, and postsaccade intervals) were applied to the left or right EVC. This had no effect when (a) fixation was maintained, (b) saccades kept the object in the same VQ, or (c) the EVC quadrant corresponding to the first object was stimulated. However, as predicted, TMS reduced performance when saccades (especially larger saccades) crossed the remembered object location and brought it into the VQ corresponding to the TMS site. This suppression effect was statistically significant for leftward saccades and followed a weaker trend for rightward saccades. These causal results are consistent with the idea that EVC is involved in the gaze-centered updating of object features for trans-saccadic memory and perception. |
Radha Nila Meghanathan; Cees Leeuwen; Andrey R. Nikolaev Fixation duration surpasses pupil size as a measure of memory load in free viewing Journal Article In: Frontiers in Human Neuroscience, vol. 8, pp. 1063, 2015. @article{Meghanathan2015, Oculomotor behavior reveals, not only the acquisition of visual information at fixation, but also the accumulation of information in memory across subsequent fixations. Two candidate measures were considered as indicators of such dynamic visual memory load: fixation duration and pupil size. While recording these measures, we displayed an arrangement of 3, 4 or 5 targets among distractors. Both occurred in various orientations. Participants searched for targets and reported whether in a subsequent display one of them had changed orientation. We determined to what extent fixation duration and pupil size indicate dynamic memory load, as a function of the number of targets fixated during the search. We found that fixation duration reflects the number of targets, both when this number is within and above the limit of working memory capacity. Pupil size reflects the number of targets only when it exceeds the capacity limit. Moreover, the duration of fixations on successive targets but not on distractors increases whereas pupil size does not. The increase in fixation duration with number of targets both within and above working memory capacity suggests that in free viewing fixation duration is sensitive to actual memory load as well as to processing load, whereas pupil size is indicative of processing load only. Two alternative models relating visual attention and working memory are considered relevant to these results. We discuss the results as supportive of a model which involves a temporary buffer in the interaction of attention and working memory. |
Gonçalo Padrão; Borja Rodriguez-Herreros; Laura Pérez Zapata; Antoni Rodriguez-Fornells Exogenous capture of medial-frontal oscillatory mechanisms by unattended conflicting information Journal Article In: Neuropsychologia, vol. 75, pp. 458–468, 2015. @article{Padrao2015, A long-standing debate in psychology and cognitive neuroscience concerns the way in which unattended information is processed and influences goal-directed behavior. Although selective attention allows us to filter out task-irrelevant information, there is a substantial number of unattended, yet relevant, events that must be evaluated in a flexible manner so that appropriate behaviors can succeed. Here we inspected the extent to which unattended conflicting visual information, which cannot be consciously identified, influences behavior and activates medial prefrontal cortex (mPFC) mechanisms of action-monitoring and regulation, traditionally associated with conscious control processes.To that end, we performed two experiments using a novel variant of the Eriksen flanker task in which spatial attention was manipulated, preventing the conscious identification of unattended visual events. The first behavioral experiment was conducted to validate the efficacy of the novel paradigm. In the second experiment, we evaluated electrophysiological correlates of mPFC activity (a frontocentral negative ERP component and medial-frontal theta oscillations) in response to attended and unattended conflicting events. The results of both experiments demonstrated that attended and unattended conflicting stimuli altered subjects' behavior in a similar fashion, i.e. slowing down their reaction times and increasing their error rates. Importantly, the results of the EEG experiment showed that unattended conflicting stimuli, similarly to attended conflicting stimuli, led to an increase in theta-related frontocentral ERP activity and medial-frontal theta power, irrespective of the degree of conscious representation of the sources of conflict. This study provides evidence that medial-frontal theta oscillations represent a neural mechanism through which the mPFC may suppress and regulate potentially inappropriate actions that are automatically triggered by conflicting environmental stimuli to which we are oblivious. |
David R. Painter; Paul E. Dux; Jason B. Mattingley Causal involvement of visual area MT in global feature-based enhancement but not contingent attentional capture Journal Article In: NeuroImage, vol. 118, pp. 90–102, 2015. @article{Painter2015, When visual attention is set for a particular target feature, such as color or shape, neural responses to that feature are enhanced across the visual field. This global feature-based enhancement is hypothesized to underlie the contingent attentional capture effect, in which task-irrelevant items with the target feature capture spatial attention. In humans, however, different cortical regions have been implicated in global feature-based enhancement and contingent capture. Here, we applied intermittent theta-burst stimulation (iTBS) to assess the causal roles of two regions of extrastriate cortex - right area MT and the right temporoparietal junction (TPJ) - in both global feature-based enhancement and contingent capture. We recorded cortical activity using EEG while participants monitored centrally for targets defined by color and ignored peripheral checkerboards that matched the distractor or target color. In central vision, targets were preceded by colored cues designed to capture attention. Stimuli flickered at unique frequencies, evoking distinct cortical oscillations. Analyses of these oscillations and behavioral performance revealed contingent capture in central vision and global feature-based enhancement in the periphery. Stimulation of right area MT selectively increased global feature-based enhancement, but did not influence contingent attentional capture. By contrast, stimulation of the right TPJ left both processes unaffected. Our results reveal a causal role for the right area MT in feature-based attention, and suggest that global feature-based enhancement does not underlie the contingent capture effect. |
Adam Palanica; Roxane J. Itier Eye gaze and head orientation modulate the inhibition of return for faces Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 8, pp. 2589–2600, 2015. @article{Palanica2015, The present study used an inhibition of return (IOR) spatial cueing paradigm to examine how gaze direction and head orientation modulate attention capture for human faces. Target response time (RT) was measured after the presentation of a peripheral cue, which was either a face (with front-facing or averted gaze, in either frontal head view or averted head view) or a house (control). Participants fixated on a centered cross at all times and responded via button press to a peripheral target after a variable stimulus onset asynchrony (SOA) from the stimulus cue. At the shortest SOA (150 ms), RTs were shorter for faces than houses, independent of an IOR response, suggesting a cue-based RT advantage elicited by faces. At the longest SOA (2,400 ms), a larger IOR magnitude was found for faces compared to houses. Both the cue-based RT advantage and later IOR responses were modulated by gaze-head congruency; these effects were strongest for frontal gaze faces in frontal head view, and for averted gaze faces in averted head view. Importantly, participants were not given any specific information regarding the stimuli, nor were they told the true purpose of the study. These findings indicate that the congruent combination of head and gaze direction influence the exogenous attention capture of faces during inhibition of return. |
Jinger Pan; Hua Shu; Yuling Wang; Ming Yan Parafoveal activation of sign translation previews among deaf readers during the reading of Chinese sentences Journal Article In: Memory & Cognition, vol. 43, no. 6, pp. 964–972, 2015. @article{Pan2015, In the present study, we manipulated the different types of information available in the parafovea during the reading of Chinese sentences and examined whether deaf readers could activate sign translations of Chinese words during reading. The main finding was that, as compared to unrelated previews, the deaf readers had longer fixation durations on the target words when sign-phonologically related preview words were presented; this preview cost effect due to sign-phonological relatedness was absent for reading-level-matched hearing individuals. These results indicate that Chinese deaf readers activate sign language translations of parafoveal words during reading. We discuss the implications for notions of parafoveal processing in reading. |
Marianne E. F. Piano; Peter J. Bex; Anita J. Simmers Perceptual visual distortions in adult amblyopia and their relationship to clinical features Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 9, pp. 5533–5542, 2015. @article{Piano2015, PURPOSE: Develop a paradigm to map binocular perceptual visual distortions in adult amblyopes and visually normal controls, measure their stability over time, and determine the relationship between strength of binocular single vision and distortion magnitude. METHODS: Perceptual visual distortions were measured in 24 strabismic, anisometropic, or microtropic amblyopes (interocular acuity difference ≥ 0.200 logMAR or history of amblyopia treatment) and 10 controls (mean age 27.13 ± 10.20 years). The task was mouse-based target alignment on a stereoscopic liquid crystal display monitor, measured binocularly five times during viewing dichoptically through active shutter glasses, amblyopic eye viewing cross-hairs, fellow eye viewing single target dots (16 locations within central 5°), and five times nondichoptically, with all stimuli visible to either eye. Measurements were repeated over time (1 week, 1 month) in eight amblyopic subjects, evaluating test-retest reliability. Measurements were also correlated against logMAR visual acuity, horizontal prism motor fusion range, Frisby/Preschool Randot stereoacuity, and heterophoria/heterotropia prism cover test measurement. RESULTS: Sixty-seven percent (16/24) of amblyopes had significant perceptual visual distortions under dichoptic viewing conditions compared to nondichoptic viewing conditions and dichoptic control group performance. Distortions correlated with the strength of motor fusion (r = -0.417 |
Jordan E. Pierce; J. Brett McCardel; Jennifer E. McDowell Trial-type probability and task-switching effects on behavioral response characteristics in a mixed saccade task Journal Article In: Experimental Brain Research, vol. 233, no. 3, pp. 959–969, 2015. @article{Pierce2015, Eye movement circuitry involved in saccade production offers a model for studying cognitive control: visually guided prosaccades are stimulus-directed responses, while goal-driven antisaccades rely upon more complex control processes to inhibit the prepotent tendency to look toward a cue, transform its spatial location, and generate a volitional saccade in the opposite direction. By manipulating the relative probability of these saccade types, we measured participants' behavioral responses to different levels of implicit trial-type probability and task-switching demands in conditions with relatively long inter-trial fixation and trial-type cue lengths. Results indicated that when prosaccades were less probable in a run, more prosaccade errors were generated; however, for antisaccades, trial-type probability had no effect on the percent of correct responses. For reaction times, specifically in runs with a larger probability of antisaccade trials, latencies increased for both anti- and pro-saccades. Furthermore, task switching resulted in a lower percentage of correct responses on switched trials, but a prior antisaccade trial led to slower reaction times for both trial types (i.e., a task switch cost for prosaccades and switch benefit for antisaccades). These findings indicate that cognitive control demands and residual inhibition from antisaccades alter performance relative to trial-type probability and task switching within a run, with the prosaccade task showing greater susceptibility to the influence of a large probability of cognitively complex antisaccades. |
Anastasia Pilat; Daniel Sibley; Rebecca J. McLean; Frank A. Proudlock; Irene Gottlob High-resolution imaging of the optic nerve and retina in optic nerve hypoplasia Journal Article In: Ophthalmology, vol. 122, no. 7, pp. 1330–1339, 2015. @article{Pilat2015, Purpose To investigate the optic nerve and macular morphology in patients with optic nerve hypoplasia (ONH) using spectral-domain optical coherence tomography (SD OCT). Design Prospective, cross-sectional, observational study. Subjects A total of 16 participants with ONH (10 female and 6 male; mean age, 17.2 years; 6 bilateral involvement) and 32 gender-, age-, ethnicity-, and refraction-matched healthy controls. Methods High-resolution SD OCT (Copernicus [Optopol Technology S.A., Zawiercie, Poland], 3 μm resolution) and handheld SD OCT (Bioptigen Inc [Research Triangle Park, NC], 2.6 μm resolution) devices were used to acquire horizontal scans through the center of the optic disc and macula. Main Outcome Measures Horizontal optic disc/cup and rim diameters, cup depth, peripapillary retinal nerve fiber layer (RNFL), and thickness of individual retinal layers in participants with ONH and in controls. Results Patients with ONH had significantly smaller discs (P < 0.03 and P < 0.001 compared with unaffected eye and healthy controls, respectively), horizontal cup diameter (P < 0.02 for both), and cup depth (P < 0.02 and P < 0.01, respectively). In the macula, significantly thinner RNFL (nasally), ganglion cell layer (GCL) (nasally and temporally), inner plexiform layer (IPL) (nasally), outer nuclear layer (ONL) (nasally), and inner segment (centrally and temporally) were found in patients with ONH compared with the control group (P < 0.05 for all comparisons). Continuation of significantly thicker GCL, IPL, and outer plexiform layer in the central retinal area (i.e., foveal hypoplasia) was found in more than 80% of patients with ONH. Clinically unaffected fellow eyes of patients with ONH showed mild features of underdevelopment. Visual acuity and presence of septo-optic dysplasia were associated with changes in GCL and IPL. Sensitivity and specificity for the detection of ONH based on disc and retinal optical coherence tomography (OCT) parameters were >80%. Conclusions Our study provides evidence of retinal changes in ONH. In addition to thinning of retina layers mainly involving the RNFL and GCL, signs reminiscent of foveal hypoplasia were observed in patients with ONH. Optic nerve and foveal parameters measured using OCT showed high sensitivity and specificity for detecting ONH, demonstrating their useful for clinical diagnosis. |
Alessandro Piras; Milena Raffi; Ivan M. Lanzoni; Michela Persiani; Salvatore Squatrito Microsaccades and prediction of a motor act outcome in a dynamic sport situation Journal Article In: Investigative Ophthalmology & Visual Science, vol. 56, no. 8, pp. 4520–4530, 2015. @article{Piras2015, PURPOSE Microsaccades could indicate the place where our mind is unconsciously focusing, although our gaze is directed elsewhere. Many studies report the importance of microsaccades in visual scene perception, but none of them has addressed their relationship with the perception of a dynamic action and the prediction of its outcome. METHODS Expert and novice table tennis players were asked to fixate their gaze on a precise spot while viewing the launch of a ball whose final landing had to be predicted. Four separate epochs of the action were considered for their information content. The correctness of the prediction and microsaccade statistics were measured in order to estimate the relationship between covert attention and predictions. RESULTS Microsaccades rate showed a time course modulated by the different epochs, with a significant enhancement during the post-bounce. In this epoch, novices showed a significantly higher rate than experts when the responses were correct. Duration and amplitude were highest in the pre- and post-bounce periods and lowest in the other two. Mean microsaccades direction was toward the stimuli that most probably attracted the visual attention (ball or racket), whereas there was no relationship with the predicted side of the final bounce. CONCLUSIONS Distribution of microsaccades can be influenced by attentional cues in a task-specific situation, revealing links between visuomotor performance and covert attention shifts in fast visuomotor perception. Microsaccade orientation is conditioned by objects that attract visual attention and not by the direction in which action is expected to be performed. |
Bertalan Polner; Désirée S. Aichert; Christine Macare; Anna Costa; Ulrich Ettinger Gently restless: Association of ADHD-like traits with response inhibition and interference control Journal Article In: European Archives of Psychiatry and Clinical Neuroscience, vol. 265, no. 8, pp. 689–699, 2015. @article{Polner2015, Impairment of inhibition-related functions is one of the most pronounced cognitive deficits found in attention-deficit/hyperactivity disorder (ADHD). Compelling evidence from studies of unaffected relatives of patients with ADHD and of ADHD-like traits in healthy subjects suggest the continuous distribution of ADHD symptoms in the population. A more subtle inhibitory deficit can also be found in healthy relatives of patients and in subjects with high ADHD-like traits. Here, we examined the relationship between inhibitory performance and ADHD-like traits, for the first time, in a large sample of healthy adults by applying multiple, widely used tests of inhibition-related functions. ADHD-like traits, in general, were independently predicted by Stroop interference score and, at trend level, by go/no-go commission error rate while controlling for socio-demographic factors, verbal intelligence and neuroticism. Additionally, higher inattentive traits were related to worse Stroop performance at trend level, and higher hyperactive/impulsive traits were significantly associated with more go/no-go commission errors. ADHD-like traits were strongly related to neuroticism. The study shows that individual differences in ADHD-like traits are related to variance in fundamental inhibition-related functions over and above effects of negative affect regulation, but the relationships tend to be small. The results suggest the quasi-dimensionality of ADHD and raise further questions about the relationship between genetic factors and the deficit of inhibition-related functions in the ADHD spectrum. |
Luca Polonio; D. S. Guida; Giorgio Coricelli; Sibilla Di Guida; Giorgio Coricelli Strategic sophistication and attention in games: An eye-tracking study Journal Article In: Games and Economic Behavior, vol. 94, pp. 80–96, 2015. @article{Polonio2015, We used eye-tracking to measure the dynamic patterns of visual information acquisition in two-player normal-form games. Participants played one-shot games in which either, neither, or only one of the players had a dominant strategy. First, we performed a mixture models cluster analysis to group participants into types according to the pattern of visual information acquisition observed in a single class of games. Then, we predicted agents' choices in different classes of games and observed that patterns of visual information acquisition were game invariant. Our method allowed us to predict whether the decision process would lead to equilibrium choices or not, and to attribute out-of-equilibrium responses to limited cognitive capacities or social motives. Our results suggest the existence of individually heterogeneous-but-stable patterns of visual information acquisition based on subjective levels of strategic sophistication and social preferences. |
Kaewmart Pongakkasira; Markus Bindemann The shape of the face template: Geometric distortions of faces and their detection in natural scenes Journal Article In: Vision Research, vol. 109, pp. 99–106, 2015. @article{Pongakkasira2015, Human face detection might be driven by skin-coloured face-shaped templates. To explore this idea, this study compared the detection of faces for which the natural height-to-width ratios were preserved with distorted faces that were stretched vertically or horizontally. The impact of stretching on detection performance was not obvious when faces were equated to their unstretched counterparts in terms of their height or width dimension (Experiment 1). However, stretching impaired detection when the original and distorted faces were matched for their surface area (Experiment 2), and this was found with both vertically and horizontally stretched faces (Experiment 3). This effect was evident in accuracy, response times, and also observers' eye movements to faces. These findings demonstrate that height-to-width ratios are an important component of the cognitive template for face detection. The results also highlight important differences between face detection and face recognition. |
Avery Popien; Mallory Frayn; Kristin M. Ranson; Christopher R. Sears Eye gaze tracking reveals heightened attention to food in adults with binge eating when viewing images of real-world scenes Journal Article In: Appetite, vol. 91, pp. 233–240, 2015. @article{Popien2015, Individuals with eating disorders often exhibit food-related biases in attention tasks. To assess the engagement and maintenance of attention to food in adults with binge eating, in the present study, eye gaze tracking was used to compare fixations to food among non-clinical adults with versus without binge eating while they viewed images of real-world scenes. Fifty-seven participants' eye fixations were tracked and recorded throughout 8-second presentations of scenes containing high-calorie and/or low-caloriefood items in various settings (restaurants, social gatherings, etc.). Participants with binge eating fixated on both high-calorie and low-calorie food items significantly more than controls, and this was the case when the high- and low-calorie food items were presented in the same image and in different images. Participants with binge eating also fixated on food items significantly earlier in the presentations. A time course analysis that divided each 8-second presentation into 2-second intervals revealed that participants with binge eating attended to food items more than control participants throughout the 8-second presentation. These results have implications for theory regarding the initiation and maintenance of binge eating. |
Ivo D. Popivanov; Jan Jastorff; Wim Vanduffel; Rufin Vogels Tolerance of macaque middle STS body patch neurons to shape-preserving stimulus transformations Journal Article In: Journal of Cognitive Neuroscience, vol. 27, no. 5, pp. 1001–1016, 2015. @article{Popivanov2015, Functional imaging studies in human and nonhuman primates have demonstrated regions in the brain that show category selectivity for faces or (headless) bodies. Recent fMRI-guided single unit studies of the macaque face category-selective regions have increased our understanding of the response properties of single neurons in these face patches. However, much less is known about the response properties of neurons in the fMRI- defined body category-selective regions (“body patches”). Recently, we reported that the majority of single neurons in one fMRI-defined body patch, the mid-STS body patch, responded more strongly to bodies compared with other objects. Here we assessed the tolerance of these neurons' responses and stimulus preference for shape-preserving image transformations. After mapping the receptive field of the single neurons, we found that their stimulus preference showed a high degree of tolerance for changes in the position and size of the stimulus. However, their response strongly depended on the in-plane orientation of a body. The selectivity ofmost neurons was, to a large degree, preserved when silhouettes were presented instead of the original textured and shaded images, suggesting that mainly shape-based features are driving these neurons. In a human psychophysical study, we showed that the information present in silhouettes is largely sufficient for body versus nonbody categorization. These data suggest that mid-STS body patch neurons respond predominantly to oriented shape features that are prevalent in images of bodies. Their responses can inform position- and retinal size-invariant body categorization and discrimination based on shape. |
Lyuba Mancheva; Erik D. Reichle; Benoît Lemaire; Sylviane Valdois; Jean Ecalle; Anne Guérin-Dugué An analysis of reading skill development using E-Z Reader Journal Article In: Journal of Cognitive Psychology, vol. 27, no. 5, pp. 657–676, 2015. @article{Mancheva2015, Previously reported simulations using the E-Z Reader model of eye-movement control suggest that the patterns of eye movements observed with children versus adult readers reflect differences in lexical processing proficiency. However, these simulations fail to specify precisely what aspect(s) of lexical processing (e.g., orthographic processing) account for the concurrent changes in eye movements and reading skill. To examine this issue, the E-Z Reader model was first used to simulate the aggregate eye-movement data from 15 adults and 75 children to replicate the finding that gross differences in reading skill can be accounted for by differences in lexical processing proficiency. The model was then used to simulate the eye-movement data of individual children so that the best-fitting lexical processing parameters could be correlated to measures of orthographic knowledge, phonological processing skill, sentence comprehension, and general intelligence. These analyses suggest that orthographic knowledge accounts for variance in the eye-movement measures that is observed with between-individual differences in reading skill. The theoretical implications of this conclusion will be discussed in relation to computational models of reading and our understanding of reading skill development. |
Anne Mandel; Siiri Helokunnas; Elina Pihko; Riitta Hari Brain responds to another person's eye blinks in a natural setting-the more empathetic the viewer the stronger the responses Journal Article In: European Journal of Neuroscience, vol. 42, no. 8, pp. 2508–2514, 2015. @article{Mandel2015, An observer's brain is known to respond to another person's small nonverbal signals, such as gaze shifts and eye blinks. Here we aimed to find out how an observer's brain reacts to a speaker's eye blinks in the presence of other audiovisual information. Magnetoencephalographic brain responses along with eye gaze were recorded from 13 adults who watched a video of a person telling a story. The video was presented first without sound (visual), then with sound (audiovisual), and finally the audio story was presented with a still-frame picture on the screen (audio control). The viewers mainly gazed at the eye region of the speaker. Their saccades were suppressed at about 180 ms after the start of the speaker's blinks, a subsequent increase of saccade occurence to the base level, or higher, at around 340 ms. The suppression occurred in visual and audiovisual conditions but not during the control audio presentation. Prominent brain responses to blinks peaked in the viewer's occipital cortex at about 250 ms, with no differences in mean peak amplitudes or latencies between visual and audiovisual conditions. During the audiovisual, but not visual-only, presentation, the responses were the stronger the more empathetic the subject was according to the Empathic Concern score of the Interpersonal Reactivity Index questionnaire (Spearman's rank correlation, 0.73). The other person's eye blinks, nonverbal signs that often go unnoticed, thus elicited clear brain responses even in the presence of attention-attracting audiovisual information from the narrative, with stronger responses in people with higher empathy scores. |
Ran Manor; Amir B. Geva Convolutional neural network for multi-category rapid serial visual presentation BCI Journal Article In: Frontiers in Computational Neuroscience, vol. 9, pp. 146, 2015. @article{Manor2015, Brain computer interfaces rely on machine learning (ML) algorithms to decode the brain's electrical activity into decisions. For example, in rapid serial visual presentation (RSVP) tasks, the subject is presented with a continuous stream of images containing rare target images among standard images, while the algorithm has to detect brain activity associated with target images. Here, we continue our previous work, presenting a deep neural network model for the use of single trial EEG classification in RSVP tasks. Deep neural networks have shown state of the art performance in computer vision and speech recognition and thus have great promise for other learning tasks, like classification of EEG samples. In our model, we introduce a novel spatio-temporal regularization for EEG data to reduce overfitting. We show improved classification performance compared to our earlier work on a five categories RSVP experiment. In addition, we compare performance on data from different sessions and validate the model on a public benchmark data set of a P300 speller task. Finally, we discuss the advantages of using neural network models compared to manually designing feature extraction algorithms. |
Barbara F. M. Marino; Giovanni Mirabella; Rossana Actis-Grosso; Emanuela Bricolo; Paola Ricciardelli Can we resist another person's gaze? Journal Article In: Frontiers in Behavioral Neuroscience, vol. 9, pp. 258, 2015. @article{Marino2015, Adaptive adjustments of strategies are needed to optimize behavior in a dynamic and uncertain world. A key function in implementing flexible behavior and exerting self- control is represented by the ability to stop the execution of an action when it is no longer appropriate for the environmental requests. Importantly, stimuli in our environment are not equally relevant and some are more valuable than others. One example is the gaze of other people, which is known to convey important social information about their direction of attention and their emotional and mental states. Indeed, gaze direction has a significant impact on the execution of voluntary saccades of an observer since it is capable of inducing in the observer an automatic gaze-following behavior: a phenomenon named social or joint attention. Nevertheless, people can exert volitional inhibitory control on saccadic eye movements during their planning. Little is known about the interaction between gaze direction signals and volitional inhibition of saccades. To fill this gap, we administered a countermanding task to 15 healthy participants in which they were asked to observe the eye region of a face with the eyes shut appearing at central fixation. In one condition, participants were required to suppress a saccade, that was previously instructed by a gaze shift toward one of two peripheral targets, when the eyes were suddenly shut down (social condition, SC). In a second condition, participants were asked to inhibit a saccade, that was previously instructed by a change in color of one of the two same targets, when a change of color of a central picture occurred (non- social condition, N-SC). We found that inhibitory control was more impaired in the SC, suggesting that actions initiated and stopped by social cues conveyed by the eyes are more difficult to withhold. This is probably due to the social value intrinsically linked to these cues and the many uses we make of them. |
Julie Markant; Michael S. Worden; Dima Amso Not all attention orienting is created equal: Recognition memory is enhanced when attention orienting involves distractor suppression Journal Article In: Neurobiology of Learning and Memory, vol. 120, pp. 28–40, 2015. @article{Markant2015, Learning through visual exploration often requires orienting of attention to meaningful information in a cluttered world. Previous work has shown that attention modulates visual cortex activity, with enhanced activity for attended targets and suppressed activity for competing inputs, thus enhancing the visual experience. Here we examined the idea that learning may be engaged differentially with variations in attention orienting mechanisms that drive eye movements during visual search and exploration. We hypothesized that attention orienting mechanisms that engaged suppression of a previously attended location would boost memory encoding of the currently attended target objects to a greater extent than those that involve target enhancement alone. To test this hypothesis we capitalized on the classic spatial cueing task and the inhibition of return (IOR) mechanism (. Posner, 1980; Posner, Rafal, & Choate, 1985) to demonstrate that object images encoded in the context of concurrent suppression at a previously attended location were encoded more effectively and remembered better than those encoded without concurrent suppression. Furthermore, fMRI analyses revealed that this memory benefit was driven by attention modulation of visual cortex activity, as increased suppression of the previously attended location in visual cortex during target object encoding predicted better subsequent recognition memory performance. These results suggest that not all attention orienting impacts learning and memory equally. |
Linda Marschner; Sebastian Pannasch; Johannes Schulz; Sven-Thomas Graupner Social communication with virtual agents: The effects of body and gaze direction on attention and emotional responding in human observers Journal Article In: International Journal of Psychophysiology, vol. 97, no. 2, pp. 85–92, 2015. @article{Marschner2015, In social communication, the gaze direction of other persons provides important information to perceive and interpret their emotional response. Previous research investigated the influence of gaze by manipulating mutual eye contact. Therefore, gaze and body direction have been changed as a whole, resulting in only congruent gaze and body directions (averted or directed) of another person. Here, we aimed to disentangle these effects by using short animated sequences of virtual agents posing with either direct or averted body or gaze. Attention allocation by means of eye movements, facial muscle response, and emotional experience to agents of different gender and facial expressions were investigated. Eye movement data revealed longer fixation durations, i.e., a stronger allocation of attention, when gaze and body direction were not congruent with each other or when both were directed towards the observer. This suggests that direct interaction as well as incongruous signals increase the demands of attentional resources in the observer. For the facial muscle response, only the reaction of muscle zygomaticus major revealed an effect of body direction, expressed by stronger activity in response to happy expressions for direct compared to averted gaze when the virtual character's body was directed towards the observer. Finally, body direction also influenced the emotional experience ratings towards happy expressions. While earlier findings suggested that mutual eye contact is the main source for increased emotional responding and attentional allocation, the present results indicate that direction of the virtual agent's body and head also plays a minor but significant role. |
Tom R. Marshall; Til Ole Bergmann; Ole Jensen Frontoparietal structural connectivity mediates the top-down control of neuronal synchronization associated with selective attention Journal Article In: PLoS Biology, vol. 13, no. 10, pp. e1002272, 2015. @article{Marshall2015, Neuronal synchronization reflected by oscillatory brain activity has been strongly implicated in the mechanisms supporting selective gating. We here aimed at identifying the anatomical pathways in humans supporting the top-down control of neuronal synchronization. We first collected diffusion imaging data using magnetic resonance imaging to identify the medial branch of the superior longitudinal fasciculus (SLF), a white-matter tract connecting frontal control areas to parietal regions. We then quantified the modulations in oscillatory activity using magnetoencephalography in the same subjects performing a spatial attention task. We found that subjects with a stronger SLF volume in the right compared to the left hemi- sphere (or vice versa) also were the subjects who had a better ability to modulate right com- pared to left hemisphere alpha and gamma band synchronization, with the latter also predicting biases in reaction time. Our findings implicate the medial branch of the SLF in mediating top-down control of neuronal synchronization in sensory regions that support selective attention. |
Sébastien Marti; Laurie Bayet; Stanislas Dehaene Subjective report of eye fixations during serial search Journal Article In: Consciousness and Cognition, vol. 33, pp. 1–15, 2015. @article{Marti2015, Humans readily introspect upon their thoughts and their behavior, but how reliable are these subjective reports? In the present study, we explored the consistencies of and differences between the observer's subjective report and actual behavior within a single trial. On each trial of a serial search task, we recorded eye movements and the participants' beliefs of where their eyes moved. The comparison of reported versus real eye movements revealed that subjects successfully reported a subset of their eye movements. Limits in subjective reports stemmed from both the number and the type of eye movements. Furthermore, subjects sometimes reported eye movements they actually never made. A detailed examination of these reports suggests that they could reflect covert shifts of attention during overt serial search. Our data provide quantitative and qualitative measures of observers' subjective reports and reveal experimental effects of visual search that would otherwise be inaccessible. |
Christina Marx; Stefan Hawelka; Sarah Schuster; Florian Hutzler An incremental boundary study on parafoveal preprocessing in children reading aloud: Parafoveal masks overestimate the preview benefit Journal Article In: Journal of Cognitive Psychology, vol. 27, no. 5, pp. 549–561, 2015. @article{Marx2015a, Parafoveal preprocessing is an important factor for efficient reading and, in eye-movement studies, is typically investigated by means of parafoveal masking: Valid previews are compared to instances in which masks prevent preprocessing. A long-held assumption was that parafoveal preprocessing, as assessed by this technique, only reflects facilitation (i.e., a preview benefit). Recent studies, however, suggested that the benefit estimate is inflated due to interference of the parafoveal masks, i.e., the masks inflict processing costs. With children from Grades 4 and 6, we administered the novel incremental priming technique. The technique manipulates the salience of the previews by systematically varying its perceptibility (i.e., by visually degrading the previews). This technique does not require a baseline condition, but makes it possible to determine whether a preview induces facilitation or interference. Our salience manipulation of valid previews revealed a preview benefit in the children of both Grades. For two commonly used parafoveal masks, we observed interference corroborating the notion that masks are not a proper baseline. With the novel incremental boundary technique, in contrast, one can achieve an accurate estimate of the preview benefit. |
Svenja Marx; Wolfgang Einhäuser Reward modulates perception in binocular rivalry Journal Article In: Journal of Vision, vol. 15, no. 1, pp. 1–13, 2015. @article{Marx2015, Our perception does not provide us with an exact imprint of the outside world, but is continuously adapted to our internal expectations, task sets, and behavioral goals. Although effects of reward—or value in general—on perception therefore seem likely, how valuation modulates perception and how such modulation relates to attention is largely unknown. We probed effects of reward on perception by using a binocular-rivalry paradigm. Distinct gratings drifting in opposite directions were presented to each observer's eyes. To objectify their subjective perceptual experience, the optokinetic nystagmus was used as measure of current perceptual dominance. In a first experiment, one of the percepts was either rewarded or attended. We found that reward and attention similarly biased perception. In a second experiment, observers performed an attentionally demanding task either on the rewarded stimulus, the other stimulus, or both. We found that—on top of an attentional effect on perception—at each level of attentional load, reward still modulated perception by increasing the dominance of the rewarded percept. Similarly, penalizing one percept increased dominance of the other at each level of attentional load. In turn, rewarding—and similarly nonpunishing—a percept yielded performance benefits that are typically associated with selective attention. In conclusion, our data show that value modulates perception in a similar way as the volitional deployment of attention, even though the relative effect of value is largely unaffected by an attention task. |
Svenja Marx; Gina Gruenhage; Daniel Walper; Ueli Rutishauser; Wolfgang Einhäuser Competition with and without priority control: Linking rivalry to attention through winner-take-all networks with memory Journal Article In: Annals of the New York Academy of Sciences, vol. 1339, no. 1, pp. 138–153, 2015. @article{Marx2015b, Competition is ubiquitous in perception. For example, items in the visual field compete for processing resources, and attention controls their priority (biased competition). The inevitable ambiguity in the interpretation of sensory signals yields another form of competition: distinct perceptual interpretations compete for access to awareness. Rivalry, where two equally likely percepts compete for dominance, explicates the latter form of competition. Building upon the similarity between attention and rivalry, we propose to model rivalry by a generic competitive circuit that is widely used in the attention literature-a winner-take-all (WTA) network. Specifically, we show that a network of two coupled WTA circuits replicates three common hallmarks of rivalry: the distribution of dominance durations, their dependence on input strength ("Levelt's propositions"), and the effects of stimulus removal (blanking). This model introduces a form of memory by forming discrete states and explains experimental data better than competitive models of rivalry without memory. This result supports the crucial role of memory in rivalry specifically and in competitive processes in general. Our approach unifies the seemingly distinct phenomena of rivalry, memory, and attention in a single model with competition as the common underlying principle. |
Tommaso Mastropasqua; Jessica Galliussi; David Pascucci; Massimo Turatto Location transfer of perceptual learning: Passive stimulation and double training Journal Article In: Vision Research, vol. 108, pp. 93–102, 2015. @article{Mastropasqua2015, Specificity has always been considered one of the hallmarks of perceptual learning, suggesting that performance improvement would reflect changes at early stages of visual analyses (e.g., V1). More recently, however, this view has been challenged by studies documenting complete transfer of learning among different spatial locations or stimulus orientations when a double-training procedure is adopted. Here, we further investigate the conditions under which transfer of visual perceptual learning takes place, confirming that the passive stimulation at the transfer location seems to be insufficient to overcome learning specificity. By contrast, learning transfer is complete when performing a secondary task at the transfer location. Interestingly, (i) transfer emerges when the primary and secondary tasks are intermingled on a trial-by-trial basis, and (ii) the effects of learning generalization appear to be reciprocal, namely the primary task also serves to enable transfer of the secondary task. However, if the secondary task is not performed for a sufficient number of trials, then transfer is not enabled. Overall, the results lend support to the recent view that task-relevant perceptual learning may involve high-level stages of visual analyses. |
Tommaso Mastropasqua; Peter U. Tse; Massimo Turatto Learning of monocular information facilitates breakthrough to awareness during interocular suppression Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 3, pp. 790–803, 2015. @article{Mastropasqua2015a, Continuous flash suppression (CFS) is a potent method of inducing binocular rivalry, wherein a rapid succession of high-contrast images presented to one eye effectively blocks from awareness a low-contrast image presented to the other eye. Here we addressed whether the contents of the suppressed image can break through to awareness with extended CFS exposure. On 2/3 of the trials, we presented a faint bar (the target) to the nondominant eye while a high-contrast flickering Mondrian (the mask) was displayed to the dominant eye. Participants were first asked to report whether the target had broken through the CFS mask. Furthermore, on target-present trials, the participants were then asked to guess whether the target had appeared above or below the fixation point. In Experiment 1, the target was presented with a fixed orientation for four blocks of trials, whereas in the fifth block, the target could also have the orthogonal orientation. In Experiment 2, the target was always presented with a fixed orientation, but in the fifth block, unbeknownst to participants, the target and the mask were swapped across the eyes. We found that awareness of the target rapidly improved with training in both experiments. However, whereas Experiment 1 revealed that the improvement largely generalized across stimulus orientations, Experiment 2 showed that the effect of practice was eye-specific. The results suggest that increased breakthrough with training was due to a monocular form of learning. Finally, a control experiment was conducted to exclude the possibility that the monocular learning we reported could have been due to sensory adaptation caused by the masks. |
Sebastiaan Mathôt; Jean-Baptiste Melmi; Eric Castet Intrasaccadic perception triggers pupillary constriction Journal Article In: PeerJ, vol. 3, pp. 1–16, 2015. @article{Mathot2015, It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye's pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward motion for vertical gratings; upward and downward motion for horizontal gratings. When participants made a saccade perpendicular to the gratings' orientation (e.g., a leftward saccade for a vertical grating), the eye's peak velocity matched the gratings' motion. As a result, the retinal image was approximately stable for a brief moment during the saccade, and this gave rise to an intrasaccadic percept: A normally invisible stimulus became visible when eye velocity was maximal. Our results confirm and extend previous studies by demonstrating intrasaccadic perception using a reflexive measure (pupillometry) that does not rely on subjective report. Our results further show that intrasaccadic perception affects all stages of visual processing, from the pupillary response to visual awareness. |
Sebastiaan Mathôt; Alisha Siebold; Mieke Donk; Françoise Vitu Large pupils predict goal-driven eye movements Journal Article In: Journal of Experimental Psychology: General, vol. 144, no. 3, pp. 513–521, 2015. @article{Mathot2015a, Here we report that large pupils predict fixations of the eye on low-salient, inconspicuous parts of a visual scene. We interpret this as showing that mental effort, reflected by a dilation of the pupil, is required to guide gaze toward objects that are relevant to current goals, but that may not be very salient. When mental effort is low, reflected by a constriction of the pupil, the eyes tend to be captured by high-salient parts of the image, irrespective of top-down goals. The relationship between pupil size and visual saliency was not driven by luminance or a range of other factors that we considered. Crucially, the relationship was strongest when mental effort was invested exclusively in eye-movement control (i.e., reduced in a dual-task setting), which suggests that it is not due to general effort or arousal. Our finding illustrates that goal-driven control during scene viewing requires mental effort, and that pupil size can be used as an online measure to track the goal-drivenness of behavior. |
Sebastiaan Mathôt; Lotje Linden; Jonathan Grainger; Françoise Vitu The pupillary light response reflects eye-movement preparation Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 41, no. 1, pp. 28–35, 2015. @article{Mathot2015b, When the eyes are exposed to an increased influx of light, the pupils constrict. The pupillary light response (PLR) is traditionally believed to be purely reflexive and not susceptible to cognitive influences. In contrast to this traditional view, we report that preparation of a PLR occurs in parallel with preparation of a saccadic eye movement toward a bright (or dark) stimulus, even before the eyes set in motion. Participants fixated a central gray area and made a saccade toward a peripheral target. Using gaze-contingent display changes, we manipulated whether or not the brightness of the target background was the same during and after saccade preparation. More specifically, on some trials we changed the brightness of the target background during the saccade, thus dissociating the preparatory PLR (i.e., to the brightness of the target background before the saccade) from the regular PLR (i.e., to the brightness after the saccade). We show that preparation triggers a pupillary response to the brightness of a to-be-fixated target background already before the eyes have landed on it. We link our findings to the presaccadic shift of attention: The pupil prepares to adjust its size to the brightness of a to-be-fixated stimulus as soon as attention covertly shifts toward that stimulus. Our findings illustrate that the PLR is a dynamic movement that is tightly linked to visual attention and eye-movement preparation. |
Shunichi Matsuda; Hideyuki Matsumoto; Toshiaki Furubayashi; Hideki Fukuda; Ritsuko Hanajima; Shoji Tsuji; Yoshikazu Ugawa; Yasuo Terao Visual scanning area is abnormally enlarged in hereditary pure Cerebellar ataxia Journal Article In: Cerebellum, vol. 14, no. 2, pp. 63–71, 2015. @article{Matsuda2015, The aim of paper was to investigate abnormalities in visual scanning using an eye-tracking device with patients with spinocerebellar ataxia type 6 (SCA6) and SCA31, pure cerebellar types of spinocerebellar degeneration. Nineteen SCA patients (12 patients with SCA6 and 7 patients with SCA31) and 19 normal subjects in total participated in the study. While the subjects viewed images of varying complexity for later recall, we compared the visual scanning parameters between SCA patients and normal subjects. SCA patients had lower image recall scores. The scanned area in SCA patients was consistently larger than that in normal subjects. The amplitude of saccades was slightly larger in SCA patients than that in normal subjects, although it did not statistically differ between the two groups and correlated significantly with the scanned area in most images in SCA patients. The instability ratio of fixation, reflecting gaze-evoked nystagmus and downbeat nystagmus, was higher in SCA patients than that in normal subjects. Since SCA patients showed low scores despite wide visual scanning, the scanned area is considered to be abnormally enlarged. The larger scanned area in SCA patients was supposed mainly to result from the slightly larger saccade amplitude. Additionally, SCA patients showed prominent fixation disturbances probably due to gaze-evoked nystagmus and downbeat nystagmus. Consequently, SCA patients suffer from recognizing various objects in daily life, probably due to the impaired saccade control and impaired fixation. |
Taylor R. Hayes; Alexander A. Petrov; Per B. Sederberg Do we really become smarter when our fluid-intelligence test scores improve? Journal Article In: Intelligence, vol. 48, pp. 1–14, 2015. @article{Hayes2015, Recent reports of training-induced gains on fluid intelligence tests have fueled an explosion of interest in cognitive training-now a billion-dollar industry. The interpretation of these results is questionable because score gains can be dominated by factors that play marginal roles in the scores themselves, and because intelligence gain is not the only possible explanation for the observed control-adjusted far transfer across tasks. Here we present novel evidence that the test score gains used to measure the efficacy of cognitive training may reflect strategy refinement instead of intelligence gains. A novel scanpath analysis of eye movement data from 35 participants solving Raven's Advanced Progressive Matrices on two separate sessions indicated that one-third of the variance of score gains could be attributed to test-taking strategy alone, as revealed by characteristic changes in eye-fixation patterns. When the strategic contaminant was partialled out, the residual score gains were no longer significant. These results are compatible with established theories of skill acquisition suggesting that procedural knowledge tacitly acquired during training can later be utilized at posttest. Our novel method and result both underline a reason to be wary of purported intelligence gains, but also provide a way forward for testing for them in the future. |
Tao He; Yun Ding; Zhiguo Wang Environment- and eye-centered inhibitory cueing effects are both observed after a methodological confound is eliminated Journal Article In: Scientific Reports, vol. 5, pp. 16586, 2015. @article{He2015, Inhibition of return (IOR), typically explored in cueing paradigms, is a performance cost associated with previously attended locations and has been suggested as a crucial attentional mechanism that biases orientation towards novelty. In their seminal IOR paper, Posner and Cohen (1984) showed that IOR is coded in spatiotopic or environment-centered coordinates. Recent studies, however, have consistently reported IOR effects in both spatiotopic and retinotopic (eye-centered) coordinates. One overlooked methodological confound of all previous studies is that the spatial gradient of IOR is not considered when selecting the baseline for estimating IOR effects. This methodological issue makes it difficult to tell if the IOR effects reported in previous studies were coded in retinotopic or spatiotopic coordinates, or in both. The present study addresses this issue with the incorporation of no-cue trials to a modified cueing paradigm in which the cue and target are always intervened by a gaze-shift. The results revealed that a) IOR is indeed coded in both spatiotopic and retinotopic coordinates, and b) the methodology of previous work may have underestimated spatiotopic and retinotopic IOR effects. |
Wei He; Jon Brock; Blake W. Johnson Face processing in the brains of pre-school aged children measured with MEG Journal Article In: NeuroImage, vol. 106, pp. 317–327, 2015. @article{He2015a, There are two competing theories concerning the development of face perception: a late maturation account and an early maturation account. Magnetoencephalography (MEG) neuroimaging holds promise for adjudicating between the two opposing accounts by providing objective neurophysiological measures of face processing, with sufficient temporal resolution to isolate face-specific brain responses from those associated with other sensory, cognitive and motor processes. The current study used a customized child MEG system to measure M100 and M170 brain responses in 15 children aged three to six years while they viewed faces, cars and their phase-scrambled counterparts. Compared to adults tested using the same stimuli in a conventional MEG system, children showed significantly larger and later M100 responses. Children's M170 responses, derived by subtracting the responses to phase-scrambled images from the corresponding images (faces or cars) were delayed in latency but otherwise resembled the adult M170. This component has not been obtained in previous studies of young children tested using conventional adult MEG systems. However children did show a markedly reduced M170 response to cars in comparison to adults. This may reflect children's lack of expertise with cars relative to faces. Taken together, these data are in accord with recent behavioural and neuroimaging data that support early maturation of the basic face processing functions. |
Wei He; Marta I. Garrido; Paul F. Sowman; Jon Brock; Blake W. Johnson Development of effective connectivity in the core network for face perception Journal Article In: Human Brain Mapping, vol. 36, no. 6, pp. 2161–2173, 2015. @article{He2015b, This study measured effective connectivity within the core face network in young children using a paediatric magnetoencephalograph (MEG). Dynamic casual modeling (DCM) of brain responses was performed in a group of adults (N = 14) and a group of young children aged from 3 to 6 years (N = 15). Three candidate DCM models were tested, and the fits of the MEG data to the three models were compared at both individual and group levels. The results show that the connectivity structure of the core face network differs significantly between adults and children. Further, the relative strengths of face network connections were differentially modulated by experimental conditions in the two groups. These results support the interpretation that the core face network undergoes significant structural configuration and functional specialization between four years of age and adulthood. |
Alison W. Heard; Michael E. J. Masson; Daniel N. Bub Time course of action representations evoked during sentence comprehension Journal Article In: Acta Psychologica, vol. 156, pp. 98–103, 2015. @article{Heard2015, The nature of hand-action representations evoked during language comprehension was investigated using a variant of the visual-world paradigm in which eye fixations were monitored while subjects viewed a screen displaying four hand postures and listened to sentences describing an actor using or lifting a manipulable object. Displayed postures were related to either a functional (using) or volumetric (lifting) interaction with an object that matched or did not match the object mentioned in the sentence. Subjects were instructed to select the hand posture that matched the action described in the sentence. Even before the manipulable object was mentioned in the sentence, some sentence contexts allowed subjects to infer the object's identity and the type of action performed with it and eye fixations immediately favored the corresponding hand posture. This effect was assumed to be the result of ongoing motor or perceptual imagery in which the action described in the sentence was mentally simulated. In addition, the hand posture related to the manipulable object mentioned in a sentence, but not related to the described action (e.g., a writing posture in the context of a sentence that describes lifting, but not using, a pencil), was favored over other hand postures not related to the object. This effect was attributed to motor resonance arising from conceptual processing of the manipulable object, without regard to the remainder of the sentence context. |
Hanna Heikkinen; Fariba Sharifian; Ricardo Vigario; Simo Vanni Feedback to distal dendrites links fMRI signals to neural receptive fields in a spiking network model of the visual cortex Journal Article In: Journal of Neurophysiology, vol. 114, no. 1, pp. 57–69, 2015. @article{Heikkinen2015, The blood oxygenation level-dependent (BOLD) response has been strongly associated with neuronal activity in the brain. However, some neuronal tuning properties are consistently different from the BOLD response. We studied the spatial extent of neural and hemodynamic responses in the primary visual cortex, where the BOLD responses spread and interact over much longer distances than the small receptive fields of individual neurons would predict. Our model shows that a feedforward-feedback loop between V1 and a higher visual area can account for the observed spread of the BOLD response. In particular, anisotropic landing of inputs to compartmental neurons were necessary to account for the BOLD signal spread, while retaining realistic spiking responses. Our work shows that simple dendrites can separate tuning at the synapses and at the action potential output, thus bridging the BOLD signal to the neural receptive fields with high fidelity. |
Benedetta Heimler; Wieske Zoest; Francesca Baruffaldi; Mieke Donk; Pasquale Rinaldi; Maria Cristina Caselli; Francesco Pavani Finding the balance between capture and control: Oculomotor selection in early deaf adults Journal Article In: Brain and Cognition, vol. 96, pp. 12–27, 2015. @article{Heimler2015, Previous work investigating the consequence of bilateral deafness on attentional selection suggests that experience-dependent changes in this population may result in increased automatic processing of stimulus-driven visual information (e.g., saliency). However, adaptive behavior also requires observers to prioritize goal-driven information relevant to the task at hand. In order to investigate whether auditory deprivation alters the balance between these two components of attentional selection, we assessed the time-course of overt visual selection in deaf adults. Twenty early-deaf adults and twenty hearing controls performed an oculomotor additional singleton paradigm. Participants made a speeded eye-movement to a unique orientation target, embedded among homogenous non-targets and one additional unique orientation distractor that was more, equally or less salient than the target. Saliency was manipulated through color. For deaf participants proficiency in sign language was assessed. Overall, results showed that fast initiated saccades were saliency-driven, whereas later initiated saccades were goal-driven. However, deaf participants were overall slower than hearing controls at initiating saccades and also less captured by task-irrelevant salient distractors. The delayed oculomotor behavior of deaf adults was not explained by any of the linguistic measures acquired. Importantly, a multinomial model applied to the data revealed a comparable evolution over time of the underlying saliency- and goal-driven processes between the two groups, confirming the crucial role of saccadic latencies in determining the outcome of visual selection performance. The present findings indicate that prioritization of saliency-driven information is not an unavoidable phenomenon in deafness. Possible neural correlates of the documented behavioral effect are also discussed. |
Daphna Heller; Jennifer E. Arnold; Natalie M. Klein; Michael K. Tanenhaus Inferring difficulty: Flexibility in the real-time processing of disfluency Journal Article In: Language and Speech, vol. 58, no. 2, pp. 190–203, 2015. @article{Heller2015, Upon hearing a disfluent referring expression, listeners expect the speaker to refer to an object that is previously unmentioned, an object that does not have a straightforward label, or an object that requires a longer description. Two visual-world eye-tracking experiments examined whether listeners directly associate disfluency with these properties of objects, or whether disfluency attribution is more flexible and involves situation-specific inferences. Since in natural situations reference to objects that do not have a straightforward label or that require a longer description is correlated with both production difficulty and with disfluency, we used a mini-artificial lexicon to dissociate difficulty from these properties, building on the fact that recently learned names take longer to produce than existing words in one's mental lexicon. The results demonstrate that disfluency attribution involves situation-specific inferences; we propose that in new situations listeners spontaneously infer what may cause production difficulty. However, the results show that these situation-specific inferences are limited in scope: listeners assessed difficulty relative to their own experience with the artificial names, and did not adapt to the assumed knowledge of the speaker. |
Christoph Helmchen; Evripides Livitzis; Andreas Sprenger; Peter Trillenberg Cerebellar ataxia with unilateral high frequency vestibulopathy and caloric disinhibition Journal Article In: Journal of the Neurological Sciences, vol. 358, no. 1-2, pp. 527–529, 2015. @article{Helmchen2015, Quantitative analysis of the head impulse test (qHIT), known as the Halmagyi–Curthoys test, has recently more commonly been used in standard diagnostic work up of patients with dizziness, due to modern videooculography systems. qHIT examines the high frequency, high acceleration components of the vestibulo-ocular reflex (VOR), in contrast to caloric irrigation which tests its low frequency components. Here we present a patient with a unilateral vestibulopathy during qHIT suspected to suffer from peripheral unilateral vestibulopathy who showed profoundly increased caloric responses on the lesion side. We provide some evidence that this probably indicates cerebellar disease. |
John M. Henderson; Wonil Choi Neural correlates of fixation duration during real-world scene viewing: Evidence from fixation-related (FIRE) fMRI Journal Article In: Journal of Cognitive Neuroscience, vol. 27, no. 6, pp. 1137–1145, 2015. @article{Henderson2015, During active scene perception, our eyes move from one location to another via saccadic eye movements, with the eyes fixating objects and scene elements for varying amounts of time. Much of the variability in fixation duration is accounted for by attentional, perceptual, and cognitive processes associated with scene analysis and comprehension. For this reason, current theories of active scene viewing attempt to account for the influence of attention and cognition on fixation duration. Yet almost nothing is known about the neurocognitive systems associated with variation in fixation duration during scene viewing. We addressed this topic using fixation-related fMRI, which involves coregistering high-resolution eye tracking and magnetic resonance scanning to conduct event-related fMRI analysis based on characteristics of eye movements. We observed that activation in visual and prefrontal executive control areas was positively correlated with fixation duration, whereas activation in ventral areas associated with scene en- coding and medial superior frontal and paracentral regions associated with changing action plans was negatively correlated with fixation duration. The results suggest that fixation duration in scene viewing is controlled by cognitive processes associated with real-time scene analysis interacting with motor planning, consistent with current computational models of active vision for scene perception. |
John M. Henderson; Wonil Choi; Steven G. Luke; Rutvik H. Desai Neural correlates of fixation duration in natural reading: Evidence from fixation-related fMRI Journal Article In: NeuroImage, vol. 119, pp. 390–397, 2015. @article{Henderson2015a, A key assumption of current theories of natural reading is that fixation duration reflects underlying attentional, language, and cognitive processes associated with text comprehension. The neurocognitive correlates of this relationship are currently unknown. To investigate this relationship, we compared neural activation associated with fixation duration in passage reading and a pseudo-reading control condition. The results showed that fixation duration was associated with activation in oculomotor and language areas during text reading. Fixation duration during pseudo-reading, on the other hand, showed greater involvement of frontal control regions, suggesting flexibility and task dependency of the eye movement network. Consistent with current models, these results provide support for the hypothesis that fixation duration in reading reflects attentional engagement and language processing. The results also demonstrate that fixation-related fMRI provides a method for investigating the neurocognitive bases of natural reading. |
Ehab W. Hermena; Denis Drieghe; Sam Hellmuth; Simon P. Liversedge Processing of Arabic diacritical marks: Phonological-syntactic disambiguation of homographic verbs and visual crowding effects Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 41, no. 2, pp. 494–507, 2015. @article{Hermena2015, Diacritics convey vowel sounds in Arabic, allowing accurate word pronunciation. Mostly, modern Arabic is printed nondiacritized. Otherwise, diacritics appear either only on homographic words when not disambiguated by surrounding text or on all words as in religious or educational texts. In an eye-tracking experiment, we examined sentence processing in the absence of diacritics and when diacritics were presented in either modes. Heterophonic homographic target verbs that have different pronunciations in active and passive were embedded in temporarily ambiguous sentences in which in the absence of diacritics, readers cannot be certain whether the verb was active or passive. Passive sentences were disambiguated by an extra word. Our results show that readers benefitted from the disambiguating diacritics when present only on the homographic verb. When disambiguating diacritics were absent, Arabic readers followed their parsing preference for active verb analysis, and garden path effects were observed. When reading fully diacritized sentences, readers incurred only a small cost, likely due to increased visual crowding, but did not extensively process the (mostly superfluous) diacritics, thus resulting in a lack of benefit from the disambiguating diacritics on the passive verb. |
Demet Gurler; Nathan Doyle; Edgar Walker; John Magnotti; Michael S. Beauchamp A link between individual differences in multisensory speech perception and eye movements Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 4, pp. 1333–1341, 2015. @article{Gurler2015, The McGurk effect is an illusion in which visual speech information dramatically alters the perception of auditory speech. However, there is a high degree of individual variability in how frequently the illusion is perceived: some individuals almost always perceive the McGurk effect, while others rarely do. Another axis of individual variability is the pattern of eye movements make while viewing a talking face: some individuals often fixate the mouth of the talker, while others rarely do. Since the talker's mouth carries the visual speech necessary information to induce the McGurk effect, we hypothesized that individuals who frequently perceive the McGurk effect should spend more time fixating the talker's mouth. We used infrared eye tracking to study eye movements as 40 participants viewed audiovisual speech. Frequent perceivers of the McGurk effect were more likely to fixate the mouth of the talker, and there was a significant correlation between McGurk frequency and mouth looking time. The noisy encoding of disparity model of McGurk perception showed that individuals who frequently fixated the mouth had lower sensory noise and higher disparity thresholds than those who rarely fixated the mouth. Differences in eye movements when viewing the talker's face may be an important contributor to interindividual differences in multisensory speech perception. |
Tjerk P. Gutteling; Luc P. J. Selen; W. Pieter Medendorp Parallax-sensitive remapping of visual space in occipito-parietal alpha-band activity during whole-body motion Journal Article In: Journal of Neurophysiology, vol. 113, pp. 1574–1584, 2015. @article{Gutteling2015, Despite the constantly changing retinal image due to eye, head, and body movements, we are able to maintain a stable representation of the visual environment. Various studies on retinal image shifts caused by saccades have suggested that occipital and parietal areas correct for these perturbations by a gaze-centered remapping of the neural image. However, such a uniform, rotational, remapping mechanism cannot work during translations when objects shift on the retina in a more complex, depth-dependent fashion due to motion parallax. Here we tested whether the brain's activity patterns show parallax-sensitive remapping of remembered visual space during whole-body motion. Under continuous recording of electroencephalography (EEG), we passively translated human subjects while they had to remember the location of a world-fixed visual target, briefly presented in front of or behind the eyes' fixation point prior to the motion. Using a psychometric approach we assessed the quality of the memory update, which had to be made based on vestibular feedback and other extraretinal motion cues. All subjects showed a variable amount of parallax-sensitive updating errors, i.e., the direction of the errors depended on the depth of the target relative to fixation. The EEG recordings show a neural correlate of this parallax-sensitive remapping in the alpha-band power at occipito-parietal electrodes. At parietal electrodes, the strength of these alpha-band modulations correlated significantly with updating performance. These results suggest that alpha-band oscillatory activity reflects the time-varying updating of gaze-centered spatial information during parallax-sensitive remapping during whole-body motion. |
Ouazna Habchi; Elodie Rey; Romain Mathieu; Christian Urquizar; Alessandro Farnè; Denis Pélisson Deployment of spatial attention without moving the eyes is boosted by oculomotor adaptation Journal Article In: Frontiers in Human Neuroscience, vol. 9, pp. 426, 2015. @article{Habchi2015, Vertebrates developed sophisticated solutions to select environmental visual information, being capable of moving attention without moving the eyes. A large body of behavioral and neuroimaging studies indicate a tight coupling between eye movements and spatial attention. The nature of this link, however, remains highly debated. Here, we demonstrate that deployment of human covert attention, measured in stationary eye conditions, can be boosted across space by changing the size of ocular saccades to a single position via a specific adaptation paradigm. These findings indicate that spatial attention is more widely affected by oculomotor plasticity than previously thought. |
Jason Haberman; Timothy F. Brady; George A. Alvarez Individual differences in ensemble perception reveal multiple, independent levels of ensemble representation Journal Article In: Journal of Experimental Psychology: General, vol. 144, no. 2, pp. 432–446, 2015. @article{Haberman2015, Ensemble perception, including the ability to “see the average” from a group of items, operates in numerous feature domains (size, orientation, speed, facial expression, etc.). Although the ubiquity of ensemble representations is well established, the large-scale cognitive architecture of this process remains poorly defined. We address this using an individual differences approach. In a series of experiments, observers saw groups of objects and reported either a single item from the group or the average of the entire group. High-level ensemble representations (e.g., average facial expression) showed complete independence from low-level ensemble representations (e.g., average orientation). In contrast, low-level ensemble representations (e.g., orientation and color) were correlated with each other, but not with high-level ensemble representations (e.g., facial expression and person identity). These results suggest that there is not a single domain-general ensemble mechanism, and that the relationship among various ensemble representations depends on how proximal they are in representational space. |
Matthew Haigh; Jean François Bonnefon Conditional sentences create a blind spot in theory of mind during narrative comprehension Journal Article In: Acta Psychologica, vol. 160, pp. 194–201, 2015. @article{Haigh2015a, We identify a blind spot in the early Theory of Mind processing of conditional sentences that describe a protagonist's potential action, and its predictable consequences. We propose that such sentences create expectations through two independent channels. A decision theoretic channel creates an expectation that the action will be taken (viz., not taken) if it has desirable (viz., undesirable) consequences, but a structural channel acts in parallel to create an expectation that the action will be taken, irrespective of desirability. Accordingly, reading should be disrupted when a protagonist avoids an action with desirable consequences, but reading should not be disrupted when a protagonist takes an action with undesirable consequences. This prediction was supported by the eye movements of participants reading systematically varied vignettes. Reading was always disrupted when the protagonist avoided an action with desirable consequences, but disruptions were either delayed (Experiment 1) or recovered from faster (Experiment 2) when the protagonist took an action with undesirable consequences. |
Matthew Haigh; Jean François Bonnefon Eye movements reveal how readers infer intentions from the beliefs and desires of others Journal Article In: Experimental Psychology, vol. 62, no. 3, pp. 206–213, 2015. @article{Haigh2015, We examine how the beliefs and desires of a protagonist are used by readers to predict their intentions as a narrative vignette unfolds. Eye movement measures revealed that readers rapidly inferred an intention when the protagonist desired an outcome, even when this inference was not licensed by the protagonist's belief state. Reading was immediately disrupted when participants encountered a described action that contradicted this inference. During intermediate processing, desire inferences were moderated by the protagonist's belief state. Effects that emerged later in the text were again driven solely by the protagonist's desires. These data suggest that desire-based inferences are initially drawn irrespective of belief state, but are then quickly inhibited if not licensed by relevant beliefs. This inhibition of desire-based inferences may be an effortful process as it was not systematically sustained in later steps of processing. |
Tuomo Häikiö; Jukka Hyönä; Raymond Bertram The role of syllables in word recognition among beginning Finnish readers: Evidence from eye movements during reading Journal Article In: Journal of Cognitive Psychology, vol. 27, no. 5, pp. 562–577, 2015. @article{Haeikioe2015, The eye movements of Finnish first and second graders were monitored as they read sentences where polysyllabic words were either hyphenated at syllable boundaries, alternatingly coloured (every second syllable black, every second red) or had no explicit syllable boundary cues (e.g., ta-lo vs. talo vs. talo = “house”). The results showed that hyphenation at syllable boundaries slows down reading of first and second graders even though syllabification by hyphens is very common in Finnish reading instruction, as all first-grade textbooks include hyphens at syllable boundaries. When hyphens were positioned within a syllable (t-alo vs. ta-lo), beginning readers were even more disrupted. Alternate colouring did not affect reading speed, no matter whether colours signalled syllable structure or not. The results show that beginning Finnish readers prefer to process polysyllabic words via syllables rather than letter by letter. At the same time they imply that hyphenation encourages sequential syllable processing, which slows down the reading of children, who are already capable of parallel syllable processing or recognising words directly via the whole-word route. |
Harry H. Haladjian; Ella Wufong; Tamara L. Watson Spatial compression: Dissociable effects at the time of saccades and blinks Journal Article In: Journal of Vision, vol. 15, no. 9, pp. 1–19, 2015. @article{Haladjian2015, Various studies have identified systematic errors, such as spatial compression, when observers report the locations of objects displayed around the time of saccades. Localization errors also occur when holding spatial representations in visual working memory. Such errors, however, have not been examined in the context of eye blinks. In this study, we examined the effects of blinks and saccades when observers reproduced the locations of a set of briefly presented, randomly placed discs. Performance was compared with a fixation-only condition in which observers simply held these representations in working memory for the same duration; this allowed us to elucidate the relationship between the perceptual phenomena related to blinks, saccades, and visual working memory. Our results indicate that the same amount of spatial compression is experienced prior to a blink as is experienced in the control fixation-only condition, suggesting that blinks do not increase compression above that occurring from holding a spatial representation in visual memory. Saccades, however, tend to increase these compression effects and produce translational shifts both toward and away from saccade targets (depending on the time of the saccade onset in relation to the stimulus offset). A higher numerosity recall capacity was also observed when stimuli were presented prior to a blink in comparison with the other conditions. These findings reflect key differences underlying blinks and saccades in terms of spatial compression and translational shifts. Such results suggest that separate mechanisms maintain perceptual stability across these visual events. |
Shahrbanoo Hamel; Dominique Houzet; Denis Pellerin; Nathalie Guyader Does color influence eye movements while exploring videos? Journal Article In: Journal of Eye Movement Research, vol. 8, no. 1, pp. 1–10, 2015. @article{Hamel2015, Although visual attention studies consider color as one of the most important features in guiding visual attention, few studies have investigated how color influences eye movements while viewing natural scenes without any particular task. To better understand the visual features that drive attention, the aim of this paper was to quantify the influence of color on eye movements when viewing dynamic natural scenes. The influence of color was investigated by comparing the eye positions of several observers eye-tracked while viewing video stimuli in two conditions: color and grayscale. The comparison was made using the dispersion between the eye positions of observers, the number of attractive regions measured with a clustering method applied to the eye positions, and by comparing eye positions to the predictions of a saliency model. The mean amplitude of saccades and the mean duration of fixations were compared as well. Globally, a slight influence of color on eye movements was measured; only the number of attractive regions for color stimuli was slightly higher than for grayscale stimuli. However, a luminance-based saliency model predicts the eye positions for color stimuli as efficiently as for grayscale stimuli. |
Anja Gampe; Anne Keitel; Moritz M. Daum Intra-individual variability and continuity of action and perception measures in infants Journal Article In: Frontiers in Psychology, vol. 6, pp. 327, 2015. @article{Gampe2015, The development of action and perception, and their relation in infancy is a central research area in socio-cognitive sciences. In this Perspective Article, we focus on the developmental variability and continuity of action and perception. At group level, these skills have been shown to consistently improve with age. We would like to raise awareness for the issue that, at individual level, development might be subject to more variable changes. We present data from a longitudinal study on the perception and production of contralateral reaching skills of infants aged 7, 8, 9, and 12 months. Our findings suggest that individual development does not increase linearly for action or for perception, but instead changes dynamically. These non-continuous changes substantially affect the relation between action and perception at each measuring point and the respective direction of causality. This suggests that research on the development of action and perception and their interrelations needs to take into account individual variability and continuity more progressively. |
Elad Ganmor; Michael S. Landy; Eero P. Simoncelli Near-optimal integration of orientation information across saccades Journal Article In: Journal of Vision, vol. 15, no. 16, pp. 1–12, 2015. @article{Ganmor2015, We perceive a stable environment despite the fact that visual information is essentially acquired in a sequence of snapshots separated by saccadic eye movements. The resolution of these snapshots varies-high in the fovea and lower in the periphery-and thus the formation of a stable percept presumably relies on the fusion of information acquired at different resolutions. To test if, and to what extent, foveal and peripheral information are integrated, we examined human orientation-discrimination performance across saccadic eye movements. We found that humans perform best when an oriented target is visible both before (peripherally) and after a saccade (foveally), suggesting that humans integrate the two views. Integration relied on eye movements, as we found no evidence of integration when the target was artificially moved during stationary viewing. Perturbation analysis revealed that humans combine the two views using a weighted sum, with weights assigned based on the relative precision of foveal and peripheral representations, as predicted by ideal observer models. However, our subjects displayed a systematic overweighting of the fovea, relative to the ideal observer, indicating that human integration across saccades is slightly suboptimal. |
Xin Gao; Hongmei Yan; Hong-jin Sun Modulation of microsaccade rate by task difficulty revealed through between- and within-trial comparisons Journal Article In: Journal of Vision, vol. 15, no. 3, pp. 1–15, 2015. @article{Gao2015, Microsaccades (MSs) are small eye movements that occur during attempted visual fixation. While most studies concerning MSs focus on their roles in visual processing, some also suggest that the MS rate can be modulated by the amount of mental exertion involved in nonvisual processing. The current study focused on the effects of task difficulty on MS rate in a nonvisual mental arithmetic task. Experiment 1 revealed a general inverse relationship between MS rate and subjective task difficulty. During Experiment 2, three task phases with different requirements were identified: during calculation (between stimulus presentation and response), postcalculation (after reporting an answer), and a control condition (undergoing a matching sequence of events without the need to make a calculation). MS rate was observed to approximately double from the during-calculation phase to the postcalculation phase, and was significantly higher in the control condition compared to postcalculation. Only during calculation was the MS rate generally decreased with greater task difficulty. Our results suggest that the nonvisual cognitive processing can suppress MS rate, and that the extent of such suppression is related to the task difficulty. |