EyeLink Cognitive Publications
All EyeLink cognitive and perception research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Visual Search, Scene Perception, Face Processing, etc. You can also search for individual author names. If we missed any EyeLink cognitive or perception articles, please email us!
2016 |
Nicola Binetti; Charlotte Harrison; Alan Johnston; Isabelle Mareschal Pupil dilation as an index of preferred mutual gaze duration Journal Article In: Royal Society Open Science, vol. 3, no. 16008, pp. 1–11, 2016. @article{Binetti2016, Most animals look at each other to signal threat or interest. In humans, this social interaction is usually punctuated with brief periods of mutual eye contact. Deviations from this pattern of gazing behaviour generally make us feel uncomfortable and are a defining characteristic of clinical conditions such as autism or schizophrenia, yet it is unclear what constitutes normal eye contact.Here, we measured, across a wide range of ages, cultures and personality types, the period of direct gaze that feels comfortable and examined whether autonomic factors linked to arousal were indicative of people's preferred amount of eye contact. Surprisingly, we find that preferred period of gaze duration is not dependent on fundamental characteristics such as gender, personality traits or attractiveness. However, we do find that subtle pupillary changes, indicative of physiological arousal, correlate with the amount of eye contact people find comfortable. Specifically, people preferring longer durations of eye contact display faster increases in pupil size when viewing another person than those preferring shorter durations. These results reveal that a person's preferred duration of eye contact is signalled by physiological indices (pupil dilation) beyond volitional control that may play a modulatory role in gaze behaviour. |
Tessel Blom; Sebastiaan Mathôt; Christian N. L. Olivers; Stefan Van der Stigchel The pupillary light response reflects encoding, but not maintenance, in visual working memory Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 42, no. 11, pp. 1716–1723, 2016. @article{Blom2016, The pupillary light response has been shown not to be a purely reflexive mechanism but to be sensitive to higher order perceptual processes, such as covert visual attention. In the present study we examined whether the pupillary light response is modulated by stimuli that are not physically present but are maintained in visual working memory. In all conditions, displays contained both bright and dark stimuli. Participants were instructed to covertly attend and encode either the bright or the dark stimuli, which then had to be maintained in visual working memory for a subsequent change-detection task. The pupil was smaller in response to encoding bright stimuli compared to dark stimuli. However, this effect did not sustain during the maintenance phase. This was the case even when brightness was directly relevant for the working memory task. These results reveal that the encoding of task-relevant and physically present information in visual working memory is reflected in the pupil. In contrast, the pupil is not sensitive to the maintenance of task-relevant but no longer visible stimuli. One interpretation of our results is that the pupil optimizes its size for perception of stimuli during encoding; however, once stimuli are no longer visible (during maintenance), an “optimal” pupil size no longer serves a purpose, and the pupil may therefore cease to reflect the brightness of the memorized stimuli. |
Jonathan F. G. Boisvert; Neil D. B. Bruce Predicting task from eye movements: On the importance of spatial distribution, dynamics, and image features Journal Article In: Neurocomputing, vol. 207, pp. 653–668, 2016. @article{Boisvert2016, Yarbus׳ pioneering work in eye tracking has been influential to methodology and in demonstrating the apparent importance of task in eliciting different fixation patterns. There has been renewed interest in Yarbus׳ assertions on the importance of task in recent years, driven in part by a greater capability to apply quantitative methods to fixation data analysis. A number of recent research efforts have examined the extent to which an observer׳s task may be predicted from recorded fixation data. This body of recent work has raised a number of interesting questions, with some investigations calling for closer examination of the validity of Yarbus׳ claims, and subsequent efforts revealing some of the nuances involved in carrying out this type of analysis including both methodological, and data related considerations. In this paper, we present an overview of prior efforts in task prediction, and assess different types of statistics drawn from fixation data, or images in their ability to predict task from gaze. We also examine the extent to which relatively general task definitions (free-viewing, object-search, saliency-viewing, explicit saliency) may be predicted by spatial positioning of fixations, features co-located with fixation points, fixation dynamics and scene structure. This is accomplished in considering the data of Koehler et al. (2014) [30] affording a larger scale, and qualitatively different corpus of data for task prediction relative to existing efforts. Based on this analysis, we demonstrate that both spatial position, as well as local features are of value in distinguishing general task categories. The methods proposed provide a general framework for highlighting features that distinguish behavioural differences observed across visual tasks, and we relate new task prediction results in this paper to the body of prior work in this domain. Finally, we also comment on the value of task prediction and classification models in general in understanding facets of gaze behaviour. |
Jantina Bolhuis; Thorsten Kolling; Monika Knopf Looking in the eyes to discriminate: Linking infants' habituation speed to looking behaviour using faces Journal Article In: International Journal of Behavioral Development, vol. 40, no. 3, pp. 243–252, 2016. @article{Bolhuis2016, Studies showed that individual differences in encoding speed as well as looking behaviour during the encoding of facial stimuli can relate to differences in subsequent face discrimination. Nevertheless, a direct linkage between encoding speed and looking behaviour during the encoding of facial stimuli and the role of these encoding characteristics for subsequent discrimination has not been investigated yet. In the present habituation study, an eye-tracker was used to investigate how individual differences in encoding speed (number of habituation trials) relate to individual differences in looking behaviour on faces and the internal facial features (eyes, nose, and mouth) during encoding as well as discrimination. Forty infants habituated to a photograph of a female face. In a subsequent dishabituation phase, a new face was followed by the familiar one. As expected, the results showed that most of the infants were able to habituate to the face and that they managed to discriminate between the new and the familiar face. Furthermore, correlations and analyses of variance showed that individual differences in encoding during habituation related to differences in looking behaviour during habituation as well as dishabituation. Slower-habituating infants could better discriminate between the new and the familiar face and showed a higher interest in the eyes during habi-tuation as well as dishabituation than faster-habituating infants. These data underline that individual differences in encoding speed relate to individual differences in looking behaviour and that increased looking behaviour to important social cues might help subsequent discrimination. |
Sabrina Boll; Marie Bartholomaeus; Ulrike Peter; Ulrike Lupke; Matthias Gamer Attentional mechanisms of social perception are biased in social phobia Journal Article In: Journal of Anxiety Disorders, vol. 40, pp. 83–93, 2016. @article{Boll2016a, Previous studies of social phobia have reported an increased vigilance to social threat cues but also an avoidance of socially relevant stimuli such as eye gaze. The primary aim of this study was to examine attentional mechanisms relevant for perceiving social cues by means of abnormalities in scanning of facial features in patients with social phobia. In two novel experimental paradigms, patients with social phobia and healthy controls matched on age, gender and education were compared regarding their gazing behavior towards facial cues. The first experiment was an emotion classification paradigm which allowed for differentiating reflexive attentional shifts from sustained attention towards diagnostically relevant facial features. In the second experiment, attentional orienting by gaze direction was assessed in a gaze-cueing paradigm in which non-predictive gaze cues shifted attention towards or away from subsequently presented targets. We found that patients as compared to controls reflexively oriented their attention more frequently towards the eyes of emotional faces in the emotion classification paradigm. This initial hypervigilance for the eye region was observed at very early attentional stages when faces were presented for 150 ms, and persisted when facial stimuli were shown for 3 s. Moreover, a delayed attentional orienting into the direction of eye gaze was observed in individuals with social phobia suggesting a differential time course of eye gaze processing in patients and controls. Our findings suggest that basic mechanisms of early attentional exploration of social cues are biased in social phobia and might contribute to the development and maintenance of the disorder. |
Sabrina Boll; Matthias Gamer Psychopathic traits affect the visual exploration of facial expressions Journal Article In: Biological Psychology, vol. 117, pp. 194–201, 2016. @article{Boll2016, Deficits in emotional reactivity and recognition have been reported in psychopathy. Impaired attention to the eyes along with amygdala malfunctions may underlie these problems. Here, we investigated how different facets of psychopathy modulate the visual exploration of facial expressions by assessing personality traits in a sample of healthy young adults using an eye-tracking based face perception task. Fearless Dominance (the interpersonal-emotional facet of psychopathy) and Coldheartedness scores predicted reduced face exploration consistent with findings on lowered emotional reactivity in psychopathy. Moreover, participants high on the social deviance facet of psychopathy ('Self-Centered Impulsivity') showed a reduced bias to shift attention towards the eyes. Our data suggest that facets of psychopathy modulate face processing in healthy individuals and reveal possible attentional mechanisms which might be responsible for the severe impairments of social perception and behavior observed in psychopathy. |
Paul J. Boon; Artem V. Belopolsky; Jan Theeuwes The role of the oculomotor system in updating visual-spatial working memory across saccades Journal Article In: PLoS ONE, vol. 11, no. 9, pp. e0161829, 2016. @article{Boon2016, Visual-spatial workingmemory (VSWM) helps us to maintain and manipulate visual infor- mation in the absence of sensory input. It has been proposed thatVSWMis an emergent property of the oculomotor system. In the present study we investigated the role of the ocu- lomotor system in updating of spatial working memory representations across saccades. Participants had to maintain a location in memory while making a saccade to a different location. During the saccade the target was displaced, which went unnoticed by the partici- pants. After executing the saccade, participants had to indicate the memorized location. If memory updating fully relies on cancellation driven by extraretinal oculomotor signals, the displacement should have no effect on the perceived location of thememorized stimulus. However, if postsaccadic retinal information about the location of the saccade target is used, the perceived location will be shifted according to the target displacement. As it has been suggested thatmaintenance of accurate spatial representations across saccades is especially important for action control, we used different ways of reporting the location held in memory; amatch-to-sample task, a mouse click or by making another saccade. The results showed a small systematic target displacement bias in all response modalities. Parametric manipulation of the distance between the to-be-memorized stimulus and sac- cade target revealed that target displacement bias increased over time and changed its spa- tial profile from being initially centered on locations around the saccade target to becoming spatially global. Taken together results suggest that we neither rely exclusively on extraret- inal nor on retinal information in updating working memory representations across sac- cades. The relative contribution of retinal signals is not fixed but depends on both the time available to integrate these signals as well as the distance between the saccade target and the remembered location. |
Ali Borji; James Tanner Reconciling saliency and object center-bias hypotheses in explaining free-viewing fixations Journal Article In: IEEE Transactions on Neural Networks and Learning Systems, vol. 27, no. 6, pp. 1214–1226, 2016. @article{Borji2016, Predicting where people look in natural scenes has attracted a lot of interest in computer vision and computational neuroscience over the past two decades. Two seemingly contrasting categories of cues have been proposed to influence where people look: $backslash$textitlow-level image saliency and $backslash$textithigh-level semantic information. Our first contribution is to take a detailed look at these cues to confirm the hypothesis proposed by Henderson~$backslash$citehenderson1993eye and Nuthmann $backslash$& Henderson~$backslash$citenuthmann2010object that observers tend to look at the center of objects. We analyzed fixation data for scene free-viewing over 17 observers on 60 fully annotated images with various types of objects. Images contained different types of scenes, such as natural scenes, line drawings, and 3D rendered scenes. Our second contribution is to propose a simple combined model of low-level saliency and object center-bias that outperforms each individual component significantly over our data, as well as on the OSIE dataset by Xu et al.~$backslash$citexu2014predicting. The results reconcile saliency with object center-bias hypotheses and highlight that both types of cues are important in guiding fixations. Our work opens new directions to understand strategies that humans use in observing scenes and objects, and demonstrates the construction of combined models of low-level saliency and high-level object-based information. |
Lei Yuan; David Uttal; Steven L. Franconeri Are categorical spatial relations encoded by shifting visual attention between objects? Journal Article In: PLoS ONE, vol. 11, no. 10, pp. e0163141, 2016. @article{Yuan2016, We argue that people compare values in graphs with a visual routine – attending to data values in an ordered pattern over time. Do these visual routines exist to manage capacity limitations in how many values can be encoded at once, or do they actually affect the relations that are extracted? We measured eye movements while people judged configurations of a two-bar graph based on size only (“[short tall] or [tall short]?”) and contrast only (“[light dark] or [dark light]?”). Participants exhibited visual routines in which they systematically attended to a specific feature (or “anchor point”) in the graph; in the size task, most participants inspected the taller bar first, and in the contrast task, most participants attended to the darker bar first. Participants then judged configurations that varied in both size and contrast (e.g., [short-light tall-dark]); however, only one dimension was task-relevant (varied between subjects). During this orthogonal task, participants overwhelmingly relied on the same anchor point used in the single-dimension version, but only for the task-relevant dimension (e.g., taller bar for the size-relevant task). These results suggest that visual routines are associated with specific graph interpretations. Responses were also faster when task-relevant and task-irrelevant anchor points appeared on the same object (congruent) than on different objects (incongruent). This interference from the task-irrelevant dimension suggests that top-down control may be necessary to extract relevant relations from graphs. The effect of visual routines on graph comprehension has implications for both science, technology, engineering, and mathematics pedagogy and graph design. |
Hassan Zanganeh Momtaz; Mohammad Reza Daliri Predicting the eye fixation locations in the gray scale images in the visual scenes with different semantic contents Journal Article In: Cognitive Neurodynamics, vol. 10, no. 1, pp. 31–47, 2016. @article{ZanganehMomtaz2016, In recent years, there has been considerable interest in visual attention models (saliency map of visual attention). These models can be used to predict eye fixation locations, and thus will have many applications in various fields which leads to obtain better performance in machine vision systems. Most of these models need to be improved because they are based on bottom-up computation that does not consider top-down image semantic contents and often does not match actual eye fixation locations. In this study, we recorded the eye movements (i.e., fixations) of fourteen individuals who viewed images which consist natural (e.g., landscape, animal) and man-made (e.g., building, vehicles) scenes. We extracted the fixation locations of eye movements in two image categories. After extraction of the fixation areas (a patch around each fixation location), characteristics of these areas were evaluated as compared to non-fixation areas. The extracted features in each patch included the orientation and spatial frequency. After feature extraction phase, different statistical classifiers were trained for prediction of eye fixation locations by these features. This study connects eye-tracking results to automatic prediction of saliency regions of the images. The results showed that it is possible to predict the eye fixation locations by using of the image patches around subjects' fixation points. |
Alexandre Zenon; Sophie Devesse; Etienne Olivier Dopamine manipulation affects response vigor independently of opportunity cost Journal Article In: Journal of Neuroscience, vol. 36, no. 37, pp. 9516–9525, 2016. @article{Zenon2016, Dopamine is known to be involved in regulating effort investment in relation to reward, and the disruption of this mechanism is thought to be central in some pathological situations such as Parkinson's disease, addiction, and depression. According to an influential model, dopamine plays this role by encoding the opportunity cost, i.e., the average value of forfeited actions, which is an important parameter to take into account when making decisions about which action to undertake and how fast to execute it. We tested this hypothesis by asking healthy human participants to perform two effort-based decision-making tasks, following either placebo or levodopa intake in a double blind within-subject protocol. In the effort-constrained task, there was a trade-off between the amount of force exerted and the time spent in executing the task, such that investing more effort decreased the opportunity cost. In the time-constrained task, the effort duration was constant, but exerting more force allowed the subject to earn more substantial reward instead of saving time. Contrary to the model predictions, we found that levodopa caused an increase in the force exerted only in the time-constrained task, in which there was no trade-off between effort and opportunity cost. In addition, a computational model showed that dopamine manipulation left the opportunity cost factor unaffected but altered the ratio between the effort cost and reinforcement value. These findings suggest that dopamine does not represent the opportunity cost but rather modulates how much effort a given reward is worth. |
Yan Zhang; Xiaochuan Pan; Rubin Wang; Masamichi Sakagami Functional connectivity between prefrontal cortex and striatum estimated by phase locking value Journal Article In: Cognitive Neurodynamics, vol. 10, no. 3, pp. 245–254, 2016. @article{Zhang2016, The interplay between the prefrontal cortex (PFC) and striatum has an important role in cognitive processes. To investigate interactive functions between the two areas in reward processing, we recorded local field potentials (LFPs) simultaneously from the two areas of two monkeys performing a reward prediction task (large reward vs small reward). The power of the LFPs was calculated in three frequency bands: the beta band (15–29 Hz), the low gamma band (30–49 Hz), and the high gamma band (50–100 Hz). We found that both the PFC and striatum encoded the reward information in the beta band. The reward information was also found in the high gamma band in the PFC, not in the striatum. We further calculated the phase-locking value (PLV) between two LFP signals to measure the phase synchrony between the PFC and striatum. It was found that significant differences occurred between PLVs in different task periods and in different frequency bands. The PLVs in small reward condition were significant higher than that in large reward condition in the beta band. In contrast, the PLVs in the high gamma band were stronger in large reward trials than in small trials. These results suggested that the functional connectivity between the PFC and striatum depended on the task periods and reward conditions. The beta synchrony between the PFC and striatum may regulate behavioral outputs of the monkeys in the small reward condition. |
Huihui Zhou; Robert John Schafer; Robert Desimone Pulvinar-cortex interactions in vision and attention Journal Article In: Neuron, vol. 89, no. 1, pp. 209–220, 2016. @article{Zhou2016c, The ventro-lateral pulvinar is reciprocally connected with the visual areas of the ventral stream that are important for object recognition. To understand the mechanisms of attentive stimulus processing in this pulvinar-cortex loop, we investigated the interactions between the pulvinar, area V4, and IT cortex in a spatial-attention task. Sensory processing and the influence of attention in the pulvinar appeared to reflect its cortical inputs. However, pulvinar deactivation led to a reduction of attentional effects on firing rates and gamma synchrony in V4, a reduction of sensory-evoked responses and overall gamma coherence within V4, and severe behavioral deficits in the affected portion of the visual field. Conversely, pulvinar deactivation caused an increase in low-frequency cortical oscillations, often associated with inattention or sleep. Thus, cortical interactions with the ventro-lateral pulvinar are necessary for normal attention and sensory processing and for maintaining the cortex in an active state. The pulvinar is often proposed to modulate cortical processing with attention. Zhou et al. find that beyond any role in attention, the pulvinar input to cortex seems necessary to maintain the cortex in an active state. |
Lei Zhou; Yang-Yang Zhang; Zuo-Jun Wang; Li-Lin Rao; Wei Wang; Shu Li; Xingshan Li; Zhu-Yuan Liang A scanpath analysis of the risky decision-making process Journal Article In: Journal of Behavioral Decision Making, vol. 29, no. 2-3, pp. 169–182, 2016. @article{Zhou2016, In the field of eye tracking, scanpath analysis can reflect the sequential and temporal properties of the cognitive process. However, the advantages of scanpath analysis have not yet been utilized in the study of risky decision making. We explored the methodological applicability of scanpath analysis to test models of risky decision making by analyzing published data from the eye-tracking studies of Su et al. (2013); Wang and Li (2012), and Sun, Rao, Zhou, and Li (2014). These studies used a proportion task, an outcome-matched presentation condition, and a multiple-play condition as the baseline for comparison with information search and processing in the risky decision-making condition. We found that (i) the similarity scores of the intra-conditions were significantly higher than those of the inter-condition; (ii) the scanpaths of the two conditions were separable; and (iii) based on an inspection of typical trials, the patterns of the scanpaths differed between the two conditions. These findings suggest that scanpath analysis is reliable and valid for examining the process of risky decision making. In line with the findings of the three original studies, our results indicate that risky decision making is unlikely to be based on a weighting and summing process, as hypothesized by the family of expectation models. The findings highlight a new methodological direction for research on decision making. |
Matteo Toscani; Sunčica Zdravković; Karl R. Gegenfurtner Lightness perception for surfaces moving through different illumination levels Journal Article In: Journal of Vision, vol. 16, no. 15, pp. 1–18, 2016. @article{Toscani2016, Lightness perception has mainly been studied with static scenes so far. This study presents four experiments investigating lightness perception under dynamic illumination conditions. We asked participants for lightness matches of a virtual three-dimensional target moving through a light field while their eye movements were recorded. We found that the target appeared differently, depending on the direction of motion in the light field and its precise position in the light field. Lightness was also strongly affected by the choice of fixation positions with the spatiotemporal image sequence. Overall, lightness constancy was improved when observers could freely view the object, over when they were forced to fixate certain regions. Our results show that dynamic scenes and nonuniform light fields are particularly challenging for our visual system. Eye movements in such scenarios are chosen to improve lightness constancy. |
Annie Tran; James E. Hoffman Visual attention is required for multiple object tracking Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 42, no. 12, pp. 2103–2114, 2016. @article{Tran2016, In the multiple object tracking task, participants attempt to keep track of a moving set of target objects embedded in an identical set of moving distractors. Depending on several display parameters, observers are usually only able to accurately track 3 to 4 objects. Various proposals attribute this limit to a fixed number of discrete indexes (Pylyshyn, 1989), limits in visual attention (Cavanagh & Alvarez, 2005), or “architectural limits” in visual cortical areas (Franconeri, 2013). The present set of experiments examined the specific role of visual attention in tracking using a dual-task methodology in which participants tracked objects while identifying letter probes appearing on the tracked objects and distractors. As predicted by the visual attention model, probe identification was faster and/or more accurate when probes appeared on tracked objects. This was the case even when probes were more than twice as likely to appear on distractors suggesting that some minimum amount of attention is required to maintain accurate tracking performance. When the need to protect tracking accuracy was relaxed, participants were able to allocate more attention to distractors when probes were likely to appear there but only at the expense of large reductions in tracking accuracy. A final experiment showed that people attend to tracked objects even when letters appearing on them are task-irrelevant, suggesting that allocation of attention to tracked objects is an obligatory process. These results support the claim that visual attention is required for tracking objects. |
Wendy Troop-Gordon; Robert D. Gordon; Laura Vogel-Ciernia; Elizabeth Ewing Lee; Kari J. Visconti Visual attention to dynamic scenes of ambiguous provocation and children's aggressive behavior Journal Article In: Journal of Clinical Child and Adolescent Psychology, pp. 1–16, 2016. @article{TroopGordon2016, Research on biases in attention related to children's aggression has yielded mixed results. Some research suggests that inattention to social cues and reliance on maladaptive social schemas underlie aggression. Other research suggests that maladaptive social schemas lead aggressive individuals to attend to nonhostile cues. The primary objective of this study was to test the proposition that aggression is related to delayed attention to cues followed by selective attention to nonhostile cues after the provocation has occurred. A second objective was to test whether these biases are associated with aggression only when children hold negative social schemas. The eye fixations of70 children (34 boys, 36 girls; Mage = 11.71 years) were monitored with an eye tracker as they watched video clips of child actors portraying scenes of ambiguous provocation. Aggression was measured using peer-, teacher-, and parent-reports, and children completed a measure ofantisocial and prosocial peer beliefs. Aggressive behavior was associated with greater time until fixation on the provocateur among youth who held antisocial peer beliefs. Aggression was also associated with greater time until fixation on an actor displaying empathy for the victim among children reporting low levels of prosocial peer beliefs. After the provocation, aggression was associated with suppressed attention to an amused peer among children who held negative peer beliefs. Increasing attention to cues in a scene ofambiguous provocation, in conjunction with fostering more positive beliefs about peers, may be effective in reducing hostile responding among aggressive youth. |
Massimo Turatto; David Pascucci Short-term and long-term plasticity in the visual-attention system: Evidence from habituation of attentional capture Journal Article In: Neurobiology of learning and memory, vol. 130, pp. 159–169, 2016. @article{Turatto2016, Attention is known to be crucial for learning and to regulate activity-dependent brain plasticity. Here we report the opposite scenario, with plasticity affecting the onset-driven automatic deployment of spatial attention. Specifically, we showed that attentional capture is subject to habituation, a fundamental form of plasticity consisting in a response decrement to repeated stimulations. Participants performed a visual discrimination task with focused attention, while being occasionally exposed to a distractor consisting of a high-luminance peripheral onset. With practice, short-term and long-term habituation of attentional capture emerged, making the visual-attention system fully immune to distraction. Furthermore, spontaneous recovery of attentional capture was found when the distractor was temporarily removed. Capture, however, once habituated was surprisingly resistant to spontaneous recovery, taking from several minutes to days to recover. The results suggest that the mechanisms subserving exogenous attentional orienting are subject to profound and enduring plastic changes based on previous experience, and that habituation can impact high-order cognitive functions. |
Yoshiyuki Ueda; Atsuko Tominaga; Shogo Kajimura; Michio Nomura Spontaneous eye blinks during creative task correlate with divergent processing Journal Article In: Psychological Research, vol. 80, no. 4, pp. 652–659, 2016. @article{Ueda2016, Creativity consists of divergent and convergent thinking, with both related to individual eye blinks at rest. To assess underlying mechanisms between eye blinks and traditional creativity tasks, we investigated the relationship between creativity performance and eye blinks at rest and during tasks. Participants performed an alternative uses and remote association task while eye blinks were recorded. Results showed that the relationship between eye blinks at rest and creativity performance was compatible with those of previous research. Interestingly, we found that the generation of ideas increased as a function of eye blink number during the alternative uses task. On the other hand, during the remote association task, accuracy was independent of eye blink number during the task, but response time increased with it. Moreover, eye blink changes in participants who responded quickly during the remote association task were different depending on their resting state eye blinks; that is, participants with many eye blinks during rest showed little increasing eye blinks and achieved solutions quickly. Positive correlations between eye blinks during creative tasks and yielding ideas on the alternative uses task and response time on the remote association task suggest that eye blinks during creativity tasks relate to divergent thinking processes such as conceptual reorganization. |
Sandra Utz; Claus-Christian Carbon Is the Thatcher illusion modulated by face familiarity? Evidence from an eye tracking study Journal Article In: PLoS ONE, vol. 11, no. 10, pp. e0163933, 2016. @article{Utz2016, Thompson (1980) first detected and described the Thatcher Illusion, where participants instantly perceive an upright face with inverted eyes and mouth as grotesque, but fail to do so when the same face is inverted. One prominent but controversial explanation is that the processing of configural information is disrupted in inverted faces. Studies investigating the Thatcher Illusion either used famous faces or non-famous faces. Highly familiar faces were often thought to be processed in a pronounced configural mode, so they seem ideal candi-dates to be tested in one Thatcher study against unfamiliar faces–but this has never been addressed so far. In our study, participants evaluated 16 famous and 16 non-famous faces for their grotesqueness. We tested whether familiarity (famous/non-famous faces) modu-lates reaction times, correctness of grotesqueness assessments (accuracy), and eye movement patterns for the factors orientation (upright/inverted) and Thatcherisation (Thatcherised/non-Thatcherised). On a behavioural level, familiarity effects were only observable via face inversion (higher accuracy and sensitivity for famous compared to non-famous faces) but not via Thatcherisation. Regarding eye movements, however, Thatcheri-sation influenced the scanning of famous and non-famous faces, for instance, in scanning the mouth region of the presented faces (higher number, duration and dwell time of fixa-tions for famous compared to non-famous faces if Thatcherised). Altogether, famous faces seem to be processed in a more elaborate, more expertise-based way than non-famous faces, whereas non-famous, inverted faces seem to cause difficulties in accurate and sen-sitive processing. Results are further discussed in the face of existing studies of familiar vs. unfamiliar face processing. |
Marieke E. Nieuwenhuijzen; Eva W. P. Borne; Ole Jensen; Marcel A. J. Gerven Spatiotemporal dynamics of cortical representations during and after stimulus presentation Journal Article In: Frontiers in Systems Neuroscience, vol. 10, pp. 42, 2016. @article{Nieuwenhuijzen2016, Visual perception is a spatiotemporally complex process. In this study, we investigated cortical dynamics during and after stimulus presentation. We observed that visual category information related to the difference between faces and objects became apparent in the occipital lobe after 63 ms. Within the next 110 ms, activation spread out to include the temporal lobe before returning to residing mainly in the occipital lobe again. After stimulus offset, a peak in information was observed, comparable to the peak after stimulus onset. Moreover, similar processes, albeit not identical, seemed to underlie both peaks. Information about the categorical identity of the stimulus remained present until 677 ms after stimulus offset, during which period the stimulus had to be retained in working memory. Activation patterns initially resembled those observed during stimulus presentation. After about 200 ms, however, this representation changed and class-specific activity became more equally distributed over the four lobes. These results show that, although there are common processes underlying stimulus representation both during and after stimulus presentation, these representations change depending on the specific stage of perception and maintenance. |
Ronald Berg; Ariel Zylberberg; Roozbeh Kiani; Michael N. Shadlen; Daniel M. Wolpert Confidence is the bridge between multi-stage decisions Journal Article In: Current Biology, vol. 26, no. 23, pp. 3157–3168, 2016. @article{Berg2016, Demanding tasks often require a series of decisions to reach a goal. Recent progress in perceptual decision-making has served to unite decision accuracy, speed, and confidence in a common framework of bounded evidence accumulation, furnishing a platform for the study of such multi-stage decisions. In many instances, the strategy applied to each decision, such as the speed-accuracy trade-off, ought to depend on the accuracy of the previous decisions. However, as the accuracy of each decision is often unknown to the decision maker, we hypothesized that subjects may carry forward a level of confidence in previous decisions to affect subsequent decisions. Subjects made two perceptual decisions sequentially and were rewarded only if they made both correctly. The speed and accuracy of individual decisions were explained by noisy evidence accumulation to a terminating bound. We found that subjects adjusted their speed-accuracy setting by elevating the termination bound on the second decision in proportion to their confidence in the first. The findings reveal a novel role for confidence and a degree of flexibility, hitherto unknown, in the brain's ability to rapidly and precisely modify the mechanisms that control the termination of a decision. |
Ruud L. Van Den Brink; Peter R. Murphy; Sander Nieuwenhuis Pupil diameter tracks lapses of attention Journal Article In: PLoS ONE, vol. 11, no. 10, pp. e0165274, 2016. @article{VanDenBrink2016, Our ability to sustain attention for prolonged periods of time is limited. Studies on the relationship between lapses of attention and psychophysiological markers of attentional state, such as pupil diameter, have yielded contradicting results. Here, we investigated the relationship between tonic fluctuations in pupil diameter and performance on a demanding sustained attention task. We found robust linear relationships between baseline pupil diameter and several measures of task performance, suggesting that attentional lapses tended to occur when pupil diameter was small. However, these observations were primarily driven by the joint effects of time-on-task on baseline pupil diameter and task performance. The linear relationships disappeared when we statistically controlled for time-on-task effects and were replaced by consistent inverted U-shaped relationships between baseline pupil diameter and each of the task performance measures, such that most false alarms and the longest and most variable response times occurred when pupil diameter was both relatively small and large. Finally, we observed strong linear relationships between the temporal derivative of pupil diameter and task performance measures, which were largely independent of time-on-task. Our results help to reconcile contradicting findings in the literature on pupil-linked changes in attentional state, and are consistent with the adaptive gain theory of locus coeruleus-norepinephrine function. Moreover, they suggest that the derivative of baseline pupil diameter is a potentially useful psychophysiological marker that could be used in the on-line prediction and prevention of attentional lapses. |
Thomas D. W. Wilcockson; N. E. M. Sanal Heavy cannabis use and attentional avoidance of anxiety-related stimuli Journal Article In: Addictive Behaviors Reports, vol. 3, pp. 38–42, 2016. @article{Wilcockson2016, Objectives: Cannabis is now the most widely used illicit substance in the world. Previous research demonstrates that cannabis use is associated with dysfunctional affect regulation and anxiety. Anxiety is characterised by attentional biases in the presence of emotional information. This novel study therefore examined the attentional bias of cannabis users when presented with anxiety-related stimuli. The aim was to establish whether cannabis users respond to anxiety-related stimuli differently to control participants. Methods: A dot-probe paradigm was utilised using undergraduate students. Trials contained anxiety-related stimuli and neutral control stimuli. Eye-tracking was used to measure attention for the stimuli. Results: Results indicated that cannabis users demonstrated attentional-avoidance behaviour when presented with anxiety-related stimuli. Conclusions: The findings suggest a difference in processing of emotional information in relation to neutral information between groups. It would appear that cannabis users avoid anxiety provoking stimuli. Such behaviour could potentially have motivational properties that could lead to exacerbating anxiety disorder-type behaviour. |
Theresa Wildegger; Glyn W. Humphreys; Anna C. Nobre Retrospective attention interacts with stimulus strength to shape working memory performance Journal Article In: PLoS ONE, vol. 11, no. 10, pp. e0164174, 2016. @article{Wildegger2016, Orienting attention retrospectively to selective contents in working$backslash$nmemory (WM) influences performance. A separate line of research has$backslash$nshown that stimulus strength shapes perceptual representations. There is$backslash$nlittle research on how stimulus strength during encoding shapes WM$backslash$nperformance, and how effects of retrospective orienting might vary with$backslash$nchanges in stimulus strength. We explore these questions in three$backslash$nexperiments using a continuous-recall WM task. In Experiment 1 we show$backslash$nthat benefits of cueing spatial attention retrospectively during WM$backslash$nmaintenance (retrocueing) varies according to stimulus contrast during$backslash$nencoding. Retrocueing effects emerge for supraliminal but not$backslash$nsub-threshold stimuli. However, once stimuli are supraliminal,$backslash$nperformance is no longer influenced by stimulus contrast. In Experiments$backslash$n2 and 3 we used a mixture-model approach to examine how different$backslash$nsources of error in WM are affected by contrast and retrocueing. For$backslash$nhigh-contrast stimuli (Experiment 2), retrocues increased the precision$backslash$nof successfully remembered items. For low-contrast stimuli (Experiment$backslash$n3), retrocues decreased the probability of mistaking a target with$backslash$ndistracters. These results suggest that the processes by which$backslash$nretrospective attentional orienting shape WM performance are dependent$backslash$non the quality of WM representations, which in turn depends on stimulus$backslash$nstrength during encoding. |
Louise R. Williams; Madeleine A. Grealy; Steve W. Kelly; Iona Henderson; Stephen H. Butler Perceptual bias, more than age, impacts on eye movements during face processing Journal Article In: Acta Psychologica, vol. 164, pp. 127–135, 2016. @article{Williams2016, Consistent with the right hemispheric dominance for face processing, a left perceptual bias (LPB) is typically demonstrated by younger adults viewing faces and a left eye movement bias has also been revealed. Hemispheric asymmetry is predicted to reduce with age and older adults have demonstrated a weaker LPB, particularly when viewing time is restricted. What is currently unclear is whether age also weakens the left eye movement bias. Additionally, a right perceptual bias (RPB) for facial judgments has less frequently been demonstrated, but whether this is accompanied by a right eye movement bias has not been investigated. To address these issues older and younger adults' eye movements and gender judgments of chimeric faces were recorded in two time conditions. Age did not significantly weaken the LPB or eye movement bias; both groups looked initially to the left side of the face and made more fixations when the gender judgment was based on the left side. A positive association was found between LPB and initial saccades in the freeview condition and with all eye movements (initial saccades, number and duration of fixations) when time was restricted. The accompanying eye movement bias revealed by LPB participants contrasted with RPB participants who demonstrated no eye movement bias in either time condition. Consequently, increased age is not clearly associated with weakened perceptual and eye movement biases. Instead an eye movement bias accompanies an LPB (particularly under restricted viewing time conditions) but not an RPB. |
Richard J. Wiseman; Tamami Nakano Blink and you'll miss it: the role of blinking in the perception of magic tricks Journal Article In: PeerJ, vol. 4, pp. 1–9, 2016. @article{Wiseman2016, <p>Magicians use several techniques to deceive their audiences, including, for example, the misdirection of attention and verbal suggestion. We explored another potential stratagem, namely the relaxation of attention. Participants watched a video of a highly skilled magician whilst having their eye-blinks recorded. The timing of spontaneous eye-blinks was highly synchronized across participants. In addition, the synchronized blinks frequency occurred immediately after a seemingly impossible feat, and often coincided with actions that the magician wanted to conceal from the audience. Given that blinking is associated with the relaxation of attention, these findings suggest that blinking plays an important role in the perception of magic, and that magicians may utilize blinking and the relaxation of attention to hide certain secret actions.</p> |
Jeremy M. Wolfe; Mia K. Markey; Gezheng Wen; Trafton Drew; Avigael Aizenman; Tamara Miner Haygood Computational assessment of visual search strategies in volumetric medical images Journal Article In: Journal of Medical Imaging, vol. 3, no. 1, pp. 1–12, 2016. @article{Wolfe2016, When searching through volumetric images [e.g., computed tomography (CT)], radiologists appear to use two different search strategies: “drilling” (restrict eye movements to a small region of the image while quickly scrolling through slices), or “scanning” (search over large areas at a given depth before moving on to the next slice). To computationally identify the type of image information that is used in these two strategies, 23 naïve observers were instructed with either “drilling” or “scanning” when searching for target T's in 20 volumes of faux lung CTs. We computed saliency maps using both classical two-dimensional (2-D) saliency, and a three-dimen- sional (3-D) dynamic saliency that captures the characteristics of scrolling through slices. Comparing observers' gaze distributions with the saliency maps showed that search strategy alters the type of saliency that attracts fixations. Drillers' fixations aligned better with dynamic saliency and scanners with 2-D saliency. The computed saliency was greater for detected targets than for missed targets. Similar results were observed in data from 19 radiologists who searched five stacks of clinical chest CTs for lung nodules. Dynamic saliency may be superior to the 2-D saliency for detecting targets embedded in volumetric images, and thus “drilling” may be more efficient than “scanning.” |
Daw-An Wu; Patrick Cavanagh Where are you looking? Pseudogaze in afterimages Journal Article In: Journal of Vision, vol. 16, no. 5, pp. 1–10, 2016. @article{Wu2016, How do we know where we are looking? A frequent assumption is that the subjective experience of our direction of gaze is assigned to the location in the world that falls on our fovea. However, we find that observers can shift their subjective direction of gaze among different nonfoveal points in an afterimage. Observers were asked to look directly at different corners of a diamond-shaped afterimage. When the requested corner was 3.5° in the periphery, the observer often reported that the image moved away in the direction of the attempted gaze shift. However, when the corner was at 1.75° eccentricity, most reported successfully fixating at the point. Eye-tracking data revealed systematic drift during the subjective fixations on peripheral locations. For example, when observers reported looking directly at a point above the fovea, their eyes were often drifting steadily upwards. We then asked observers to make a saccade from a subjectively fixated, nonfoveal point to another point in the afterimage, 7° directly below their fovea. The observers consistently reported making appropriately diagonal saccades, but the eye movement traces only occasionally followed the perceived oblique direction. These results suggest that the perceived direction of gaze can be assigned flexibly to an attended point near the fovea. This may be how the visual world acquires its stability during fixation of an object, despite the drifts and microsaccades that are normal characteristics of visual fixation. |
Yingying Wu; Xiaohong Yang; Yufang Yang Eye movement evidence for hierarchy effects on memory representation of discourses Journal Article In: PLoS ONE, vol. 11, no. 1, pp. e0147313, 2016. @article{Wu2016b, In this study, we applied the text-change paradigm to investigate whether and how discourse hierarchy affected the memory representation of a discourse. Three kinds of three-sentence discourses were constructed. In the hierarchy-high condition and the hierarchy-low condition, the three sentences of the discourses were hierarchically organized and the last sentence of each discourse was located at the high level and the low level of the discourse hierarchy, respectively. In the linear condition, the three sentences of the discourses were linearly organized. Critical words were always located at the last sentence of the discourses. These discourses were successively presented twice and the critical words were changed to semantically related words in the second presentation. The results showed that during the early processing stage, the critical words were read for longer times when they were changed in the hierarchy-high and the linear conditions, but not in the hierarchy-low condition. During the late processing stage, the changed-critical words were again found to induce longer reading times only when they were in the hierarchy-high condition. These results suggest that words in a discourse have better memory representation when they are located at the higher rather than at the lower level of the discourse hierarchy. Global discourse hierarchy is established as an important factor in constructing the mental representation of a discourse. |
Andreas Wutz; Jan Drewes; David Melcher Nonretinotopic perception of orientation: Temporal integration of basic features operates in object-based coordinates Journal Article In: Journal of Vision, vol. 16, no. 10, pp. 1–15, 2016. @article{Wutz2016, Early, feed-forward visual processing is organized in a retinotopic reference frame. In contrast, visual feature integration on longer time scales can involve objectbased or spatiotopic coordinates. For example, in the Ternus-Pikler (T-P) apparent motion display, object identity is mapped across the object motion path. Here, we report evidence from three experiments supporting nonretinotopic feature integration even for the most paradigmatic example of retinotopically-defined features: orientation. We presented observers with a repeated series of T-P displays in which the perceived rotation of Gabor gratings indicates processing in either retinotopic or object-based coordinates. In Experiment 1, the frequency of perceived retinotopic rotations decreased exponentially for longer interstimulus intervals (ISIs) between T-P display frames, with objectbased percepts dominating after about 150-250 ms. In a second experiment, we show that motion and rotation judgments depend on the perception of a moving object during the T-P display ISIs rather than only on temporal factors. In Experiment 3, we cued the observers' attenti onal state either toward a retinotopic or object motion-based reference frame and then tracked both the observers' eye position and the time course of the perceptual bias while viewing identical T-P display sequences. Overall, we report novel evidence for spatiotemporal integration of even basic visual features such as orientation in nonretinotopic coordinates, in order to support perceptual constancy across self- and object motion. |
Lotje Linden; Françoise Vitu On the optimal viewing position for object processing Journal Article In: Attention, Perception, and Psychophysics, vol. 78, no. 2, pp. 602–617, 2016. @article{Linden2016, Numerous studies have shown that a visually pre- sented word is processed most easily when participants initial- ly fixate just to the left of the word's center. Fixating on this optimal viewing position (OVP) results in shorter response times and a lower probability of making additional within- word refixations (OVP effects), but also longer initial- fixation durations (an inverted-OVP or I-OVP effect), as com- pared to initially fixating at the beginning or the end of the word. Thus, typical curves are u-shaped (or inverted-u- shaped), with a leftward bias. Most researchers explain the u-shape in terms of visual constraints, and the leftward bias in terms of language constraints. Previous studies have dem- onstrated that (I)-OVP effects are not specific to words, but generalize to object viewing. We further investigated this by comparing the strength and (a)symmetry of (I-)OVP effects for words and objects. To this purpose, we gave participants an object- versus word-naming task in which we manipulated the position at which they initially fixated the stimulus (i.e., a line drawing or the written name of an object). Our results showed that object viewing, just as word viewing, resulted in u-shaped (I-)OVP curves. However, the effect was weaker than for words. Furthermore, for words, the curves were bi- ased to the left, whereas they were symmetrical for objects. This might indicate that part ofthe (I-)OVP effect for words is language specific, and that (I-)OVP effects for objects are a purer measure of the effect of visual constraints. |
Rosanne M. Diepen; Lee M. Miller; Ali Mazaheri; Joy J. Geng The role of alpha activity in spatial and feature-based attention. Journal Article In: eNeuro, vol. 3, no. 5, pp. 1–11, 2016. @article{Diepen2016, Modulations in alpha oscillations (?10 Hz) are typically studied in the context of anticipating upcoming stimuli. Alpha power decreases in sensory regions processing upcoming targets compared to regions processing distracting input, thereby likely facilitating processing of relevant information while suppressing irrelevant. In this electroencephalography study using healthy human volunteers, we examined whether modulations in alpha power also occur after the onset of a bilaterally presented target and distractor. Spatial attentionwasmanipulated through spatial cues and feature-based attention through adjusting the color-similarity of distractors to the target. Consistent with previous studies, we found that informative spatial cues induced a relative decrease of pretarget alpha power at occipital electrodes contralateral to the expected target location. Interestingly, this pattern reemerged relatively late (300–750 ms) after stimulus onset, suggesting that lateralized alpha reflects not only preparatory attention, but also ongoing attentive stimulus processing. Uninformative cues (i.e., conveying no information about the spatial location of the target) resulted in an interaction between spatial attention and feature-based attention in post-target alpha lateralization. When the target was paired with a low-similarity distractor, post-target alpha was lateralized (500–900 ms). Crucially, the lateralization was absent when target selection was ambig- uous because the distractor was highly similar to the target. Instead, during this condition, midfrontal theta was increased, indicative of reactive conflict resolution. Behaviorally, the degree of alpha lateralization was negatively correlated with the reaction time distraction cost induced by target–distractor similarity. These results suggest a pivotal role for poststimulus alpha lateralization in protecting sensory processing of target information. |
Jelle A. Dijk; Benjamin Haas; Christina Moutsiana; D. Samuel Schwarzkopf Intersession reliability of population receptive field estimates Journal Article In: NeuroImage, vol. 143, pp. 293–303, 2016. @article{Dijk2016, Population receptive field (pRF) analysis is a popular method to infer spatial selectivity of voxels in visual cortex. However, it remains largely untested how stable pRF estimates are over time. Here we measured the intersession reliability of pRF parameter estimates for the central visual field and near periphery, using a combined wedge and ring stimulus containing natural images. Sixteen healthy human participants completed two scanning sessions separated by 10–114 days. Individual participants showed very similar visual field maps for V1-V4 on both sessions. Intersession reliability for eccentricity and polar angle estimates was close to ceiling for most visual field maps (r>.8 for V1-3). PRF size and cortical magnification (CMF) estimates showed strong but lower overall intersession reliability (r≈.4–.6). Group level results for pRF size and CMF were highly similar between sessions. Additional control experiments confirmed that reliability does not depend on the carrier stimulus used and that reliability for pRF size and CMF is high for sessions acquired on the same day (r>.6). Our results demonstrate that pRF mapping is highly reliable across sessions. |
Nathalie Van Humbeeck; Tom Putzeys; Johan Wagemans Apparent motion suppresses responses in early visual cortex: A population code model Journal Article In: PLoS Computational Biology, vol. 12, no. 10, pp. e1005155, 2016. @article{VanHumbeeck2016, Two stimuli alternately presented at different locations can evoke a percept of a stimulus continuously moving between the two locations. The neural mechanism underlying this apparent motion (AM) is thought to be increased activation of primary visual cortex (V1) neurons tuned to locations along the AM path, although evidence remains inconclusive. AM masking, which refers to the reduced detectability of stimuli along the AM path, has been taken as evidence for AM-related V1 activation. AM-induced neural responses are thought to interfere with responses to physical stimuli along the path and as such impair the perception of these stimuli. However, AM masking can also be explained by predictive coding models, predicting that responses to stimuli presented on the AM path are suppressed when they match the spatio-temporal prediction of a stimulus moving along the path. In the present study, we find that AM has a distinct effect on the detection of target gratings, limiting the maximum performance at high contrast levels. This masking is strongest when the target orientation is identical to the orientation of the inducers. We developed a V1-like population code model of early visual processing, based on a standard contrast normalization model. We find that AM-related activation in early visual cortex is too small to either cause masking or to be perceived as motion. Our model instead predicts strong suppression of early sensory responses during AM, consistent with the theoretical framework of predictive coding. |
Anouk Mariette Loon; Johannes J. Fahrenfort; Bauke Velde; Philipp B. Lirk; Nienke C. C. Vulink; Markus W. Hollmann; H. Steven Scholte; Victor A. F. Lamme NMDA receptor antagonist ketamine distorts object recognition by reducing feedback to early visual cortex Journal Article In: Cerebral Cortex, vol. 26, no. 5, pp. 1986–1996, 2016. @article{Loon2016, It is a well-established fact that top-down processes influence neural representations in lower-level visual areas. Electrophysiological recordings in monkeys as well as theoretical models suggest that these top-down processes depend on NMDA receptor functioning. However, this underlying neural mechanism has not been tested in humans. We used fMRI multivoxel pattern analysis to compare the neural representations of ambiguous Mooney images before and after they were recognized with their unambiguous grayscale version. Additionally, we administered ketamine, an NMDA receptor antagonist, to interfere with this process. Our results demonstrate that after recognition, the pattern of brain activation elicited by a Mooney image is more similar to that of its easily recognizable grayscale version than to the pattern evoked by the identical Mooney image before recognition. Moreover, recognition of Mooney images decreased mean response; however, neural representations of separate images became more dissimilar. So from the neural perspective, unrecognizable Mooney images all “look the same”, whereas recognized Mooneys look different. We observed these effects in posterior fusiform part of lateral occipital cortex and in early visual cortex. Ketamine distorted these effects of recognition, but in early visual cortex only. This suggests that top-down processes from higher- to lower-level visual areas might operate via an NMDA pathway. |
Leendert Maanen; Laura Fontanesi; Guy E. Hawkins; Birte U. Forstmann Striatal activation reflects urgency in perceptual decision making Journal Article In: NeuroImage, vol. 139, pp. 294–303, 2016. @article{Maanen2016, Deciding between multiple courses of action often entails an increasing need to do something as time passes - a sense of urgency. This notion of urgency is not incorporated in standard theories of speeded decision making that assume information is accumulated until a critical fixed threshold is reached. Yet, it is hypothesized in novel theoretical models of decision making. In two experiments, we investigated the behavioral and neural evidence for an “urgency signal” in human perceptual decision making. Experiment 1 found that as the duration of the decision making process increased, participants made a choice based on less evidence for the selected option. Experiment 2 replicated this finding, and additionally found that variability in this effect across participants covaried with activation in the striatum. We conclude that individual differences in susceptibility to urgency are reflected by striatal activation. By dynamically updating a response threshold, the striatum is involved in signaling urgency in humans. |
Daan R. Renswoude; S. P. Johnson; Maartje E. J. Raijmakers; Ingmar Visser Do infants have the horizontal bias? Journal Article In: Infant Behavior and Development, vol. 44, pp. 38–48, 2016. @article{Renswoude2016, A robust set of studies show that adults make more horizontal than vertical and oblique saccades, while scanning real-world scenes. In this paper we study the horizontal bias in infants. The directions of eye movements were calculated for 41 infants (M = 8.40 months |
Annelinde R. E. Vandenbroucke; Johannes J. Fahrenfort; Julia D. I. Meuwese; H. Steven Scholte; Victor A. F. Lamme Prior knowledge about objects determines neural color representation in human visual cortex Journal Article In: Cerebral Cortex, vol. 26, no. 4, pp. 1401–1408, 2016. @article{Vandenbroucke2016, To create subjective experience, our brain must translate physical stimulus input by incorporating prior knowledge and expectations. For example, we perceive color and not wavelength information, and this in part depends on our past experience with colored objects ( Hansen et al. 2006; Mitterer and de Ruiter 2008). Here, we investigated the influence of object knowledge on the neural substrates underlying subjective color vision. In a functional magnetic resonance imaging experiment, human subjects viewed a color that lay midway between red and green (ambiguous with respect to its distance from red and green) presented on either typical red (e.g., tomato), typical green (e.g., clover), or semantically meaningless (nonsense) objects. Using decoding techniques, we could predict whether subjects viewed the ambiguous color on typical red or typical green objects based on the neural response of veridical red and green. This shift of neural response for the ambiguous color did not occur for nonsense objects. The modulation of neural responses was observed in visual areas (V3, V4, VO1, lateral occipital complex) involved in color and object processing, as well as frontal areas. This demonstrates that object memory influences wavelength information relatively early in the human visual system to produce subjective color vision. |
Preeti Verghese; Terence L. Tyson; Saeideh Ghahghaei; Donald C. Fletcher Depth perception and grasp in central field loss Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 3, pp. 1476–1487, 2016. @article{Verghese2016, PURPOSE: We set out to determine whether individuals with central field loss benefit from using two eyes to perform a grasping task. Specifically, we tested the hypothesis that this advantage is correlated with coarse stereopsis, in addition to binocular summation indices of visual acuity, contrast sensitivity, and binocular visual field. METHODS: Sixteen participants with macular degeneration and nine age-matched controls placed pegs on a pegboard, while their eye and hand movements were recorded. Importantly, the pegboard was placed near eye height, to minimize the contribution of monocular cues to peg position. All participants performed this task binocularly and monocularly. Before the experiment, we performed microperimetry to determine the profile of field loss in each eye and the locations of eccentric fixation (if applicable). In addition, we measured both acuity and contrast sensitivity monocularly and binocularly, and stereopsis by using both a RanDot test and a custom stereo test. RESULTS: Peg-placement time was significantly shorter and participants made significantly fewer errors with binocular than with monocular viewing in both the patient and control groups. Among participants with measurable stereopsis, binocular advantage in peg-placement time was significantly correlated with stereoacuity (ρ = -0.78; P = 0.003). In patients without measurable stereopsis, the binocular advantage was related significantly to the overlap in the scotoma between the two eyes (ρ = -0.81; P = 0.032). CONCLUSIONS: The high correlation between grasp performance and stereoacuity indicates that coarse stereopsis may benefit tasks of daily living for individuals with central field loss. |
Bram-Ernst Verhoef; John H. R. Maunsell Attention operates uniformly throughout the classical receptive field and the surround Journal Article In: eLife, vol. 5, no. AUGUST, pp. 1–16, 2016. @article{Verhoef2016, Shifting attention among visual stimuli at different locations modulates neuronal responses in heterogeneous ways, depending on where those stimuli lie within the receptive fields of neurons. Yet how attention interacts with the receptive-field structure of cortical neurons remains unclear. We measured neuronal responses in area V4 while monkeys shifted their attention among stimuli placed in different locations within and around neuronal receptive fields. We found that attention interacts uniformly with the spatially-varying excitation and suppression associated with the receptive field. This interaction explained the large variability in attention modulation across neurons, and a non-additive relationship among stimulus selectivity, stimulus-induced suppression and attention modulation that has not been previously described. A spatially-tuned normalization model precisely accounted for all observed attention modulations and for the spatial summation properties of neurons. These results provide a unified account of spatial summation and attention-related modulation across both the classical receptive field and the surround. |
Rui Wang; Jie Wang; Jun-Yun Zhang; Xin-Yu Xie; Yu-Xiang Yang; Shu-Han Luo; Cong Yu; Wu Li Perceptual learning at a conceptual level Journal Article In: Journal of Neuroscience, vol. 36, no. 7, pp. 2238–2246, 2016. @article{Wang2016a, Humans can learn to abstract and conceptualize the shared visual features defining an object category in object learning. Therefore, learning is generalizable to transformations of familiar objects and even to new objects that differ in other physical properties. In contrast, visual perceptual learning (VPL), improvement in discriminating fine differences of a basic visual feature through training, is commonly regarded as specific and low-level learning because the improvement often disappears when the trained stimulus is simply relocated or rotated in the visual field. Such location and orientation specificity is taken as evidence for neural plasticity in primary visual cortex (V1) or improved readout of V1 signals. However, new training methods have shown complete VPL transfer across stimulus locations and orientations, suggesting the involvement of high-level cognitive processes. Here we report that VPL bears similar properties of object learning. Specifically, we found that orientation discrimination learning is completely transferrable between luminance gratings initially encoded in V1 and bilaterally symmetric dot patterns encoded in higher visual cortex. Similarly, motion direction discrimination learning is transferable between first-and second-order motion signals. These results suggest that VPL can take place at a conceptual level and generalize to stimuli with different physical properties. Our findings thus reconcile perceptual and object learning into a unified framework. |
Wuyi Wang; Shivakumar Viswanathan; Taraz Lee; Scott T. Grafton In: PLoS ONE, vol. 11, no. 7, pp. e0158465, 2016. @article{Wang2016g, Cortical theta band oscillations (4-8 Hz) in EEG signals have been shown to be important for a variety of different cognitive control operations in visual attention paradigms. However the synchronization source of these signals as defined by fMRI BOLD activity and the extent to which theta oscillations play a role in multimodal attention remains unknown. Here we investigated the extent to which cross-modal visual and auditory attention impacts theta oscillations. Using a simultaneous EEG-fMRI paradigm, healthy human participants performed an attentional vigilance task with six cross-modal conditions using naturalistic stimuli. To assess supramodal mechanisms, modulation of theta oscillation amplitude for attention to either visual or auditory stimuli was correlated with BOLD activity by conjunction analysis. Negative correlation was localized to cortical regions associated with the default mode network and positively with ventral premotor areas. Modality-associated attention to visual stimuli was marked by a positive correlation of theta and BOLD activity in fronto-parietal area that was not observed in the auditory condition. A positive correlation of theta and BOLD activity was observed in auditory cortex, while a negative correlation of theta and BOLD activity was observed in visual cortex during auditory attention. The data support a supramodal interaction of theta activity with of DMN function, and modality-associated processes within fronto-parietal networks related to top-down theta related cognitive control in cross-modal visual attention. On the other hand, in sensory cortices there are opposing effects of theta activity during cross-modal auditory attention. |
Zheng Zhiwei Wang; Kristina Zeljic; Qinying Jiang; Yong Gu; Wei Wang; Zheng Wang Dynamic network communication in the human functional connectome predicts perceptual variability in visual illusion Journal Article In: Cerebral Cortex, vol. 28, no. 1, pp. 1–15, 2016. @article{Wang2016h, The eukaryotic RNA exosome is an essential, multi-subunit complex that catalyzes RNA turnover, maturation, and quality control processes. Its non-catalytic donut-shaped core includes 9 subunits that associate with the 3' to 5' exoribonucleases Rrp6, and Rrp44/Dis3, a subunit that also catalyzes endoribonuclease activity. Although recent structures and biochemical studies of RNA bound exosomes from S. cerevisiae revealed that the Exo9 central channel guides RNA to either Rrp6 or Rrp44 using partially overlapping and mutually exclusive paths, several issues related to RNA recruitment remain. Here, we identify activities for the highly basic Rrp6 C-terminal tail that we term the 'lasso' because it binds RNA and stimulates ribonuclease activities associated with Rrp44 and Rrp6 within the 11-subunit nuclear exosome. Stimulation is dependent on the Exo9 central channel, and the lasso contributes to degradation and processing activities of exosome substrates in vitro and in vivo. Finally, we present evidence that the Rrp6 lasso may be a conserved feature of the eukaryotic RNA exosome. |
Christopher M. Warren; Eran Eldar; Ruud L. Brink; Klodiana-Daphne Tona; Nic J. Wee; Eric J. Giltay; Martijn S. Noorden; Jos A. Bosch; Robert C. Wilson; Jonathan D. Cohen; Sander Nieuwenhuis Catecholamine-mediated increases in gain enhance the precision of cortical representations Journal Article In: Journal of Neuroscience, vol. 36, no. 21, pp. 5699–5708, 2016. @article{Warren2016, Neurophysiological evidence suggests that neuromodulators, such as norepinephrine and dopamine, increase neural gain in target brain areas. Computational models and prominent theoretical frameworks indicate that this should enhance the precision of neural represen- tations, but direct empirical evidence for this hypothesis is lacking. In two functional MRI studies, we examine the effect of baseline catecholamine levels (as indexed by pupil diameter and manipulated pharmacologically) on the precision of object representations in the human ventral temporal cortex using angular dispersion, a powerful, multivariate metric of representational similarity (precision). We first report the results of computational model simulations indicating that increasing catecholaminergic gain should reduce the angular dispersion, and thus increase the precision, of object representations from the same category, as well as reduce the angular dispersion of object representations from distinct categories when distinct-category representations overlap. In Study 1 (N?24), we showthat angular dispersion covaries with pupil diameter, an index of baseline catecholamine levels. In Study 2 (N?24), we manipulate catecholamine levels and neural gain using the norepinephrine transporter blocker atomoxetine and demonstrate consistent, causal effects on angular dispersion and brain-wide functional connectivity. Despite the use of very different methods of examining the effect of baseline catecholamine levels, our results show a striking convergence and demonstrate that catecholamines increase the precision of neural representations. |
David E. Warren; Daniel Tranel; Melissa C. Duff Impaired acquisition of new words after left temporal lobectomy despite normal fast-mapping behavior Journal Article In: Neuropsychologia, vol. 80, pp. 165–175, 2016. @article{Warren2016a, Word learning has been proposed to rely on unique brain regions including the temporal lobes, and the left temporal lobe appears to be especially important. In order to investigate the role of the left temporal lobe in word learning under different conditions, we tested whether patients with left temporal lobectomies (N=6) could learn novel words using two distinct formats. Previous research has shown that word learning in contrastive fast mapping conditions may rely on different neural substrates than explicit encoding conditions (Sharon et al., 2011). In the current investigation, we used a previously reported word learning task that implemented two distinct study formats (Warren and Duff, 2014): a contrastive fast mapping condition in which a picture of a novel item was displayed beside a picture of a familiar item while the novel item's name was presented aurally ("Click on the numbat."); and an explicit encoding (i.e., control) condition in which a picture of a novel item was displayed while its name was presented aurally ("This is a numbat."). After a delay, learning of the novel words was evaluated with memory tests including three-alternative forced-choice recognition, free recall, cued recall, and familiarity ratings. During the fast-mapping study condition both the left temporal lobectomy and healthy comparison groups performed well, but at test only the comparison group showed evidence of novel word learning. Our findings indicate that unilateral resection of the left temporal lobe including the hippocampus and temporal pole can severely impair word learning, and that fast-mapping study conditions do not promote subsequent word learning in temporal lobectomy populations. |
Nicolas Wattiez; Tymothée Poitou; Sophie Rivaud-Péchoux; Pierre Pouget Evidence for spatial tuning of movement inhibition Journal Article In: Experimental Brain Research, vol. 234, no. 7, pp. 1957–1966, 2016. @article{Wattiez2016, The time to initiate a movement can, even implicitly, be influenced by the environment. All primates, including humans, respond faster and with greater accuracy to stimuli that are brighter, louder or associated with larger reward, than to neutral stimuli. Whether this environment also modulates the executive functions which allow ongoing actions to be suppressed remains an issue of debate. In this study, we investigated the implicit learning of spatial selectivity of movement inhibition in humans and macaque monkeys performing a saccade-countermanding task. The occurrence of stop trials, in which subjects were visually instructed to cancel a prepared movement, was manipulated according to the target location. One visual target was associated with higher probability of stop signal appearance (e.g., 80 %), while the second target was associated with low fraction of stop (e.g., 20 %). The absolute occurrence of stop trials across the two targets (50 %) remains constant. The results show that human and macaque monkeys can selectively adapt their behaviors according to the implicit probability of stopping. Behavioral adjustments were larger when targets were in different hemifields and for larger distances between targets. Reduced selective inhibitory behaviors were observed when 15 degrees of visual angle separated the targets, and this effect vanished when targets were separated by only 2 degrees . Overall, our study shows that both response and inhibition times can be modulated by the relative spatial occurrence of stop signals. We speculate that beyond the particular effect we observed in the context of the saccade paradigm, selective motor execution may imply a disinhibitory mechanism that modulates the motor pathways associated with the fronto-median cortex and basal ganglia circuits. |
Michael W. Weiss; Sandra E. Trehub; E. Glenn Schellenberg; Peter Habashi Pupils dilate for vocal or familiar music Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 42, no. 8, pp. 1061–1065, 2016. @article{Weiss2016, Previous research reveals that vocal melodies are remembered better than instrumental renditions. Here we explored the possibility that the voice, as a highly salient stimulus, elicits greater arousal than nonvocal stimuli, resulting in greater pupil dilation for vocal than for instrumental melodies. We also explored the possibility that pupil dilation indexes memory for melodies. We tracked pupil dilation during a single exposure to 24 unfamiliar folk melodies (half sung to la la, half piano) and during a subsequent recognition test in which the previously heard melodies were intermixed with 24 novel melodies (half sung, half piano) from the same corpus. Pupil dilation was greater for vocal melodies than for piano melodies in the exposure phase and in the test phase. It was also greater for previously heard melodies than for novel melodies. Our findings provide the first evidence that pupillometry can be used to measure recognition of stimuli that unfold over several seconds. They also provide the first evidence of enhanced arousal to vocal melodies during encoding and retrieval, thereby supporting the more general notion of the voice as a privileged signal. |
Nilly Weiss; Elite Mardo; Galia Avidan Visual expertise for horses in a case of congenital prosopagnosia Journal Article In: Neuropsychologia, vol. 83, pp. 63–75, 2016. @article{Weiss2016a, A major question in the domain of face perception is whether faces comprise a distinct visual category that is processed by specialized mechanisms, or whether face processing merely represents an extreme case of visual expertise. Here, we examined O.H, a 22 years old woman with congenital prosopagnosia (CP), who despite her severe deficits in face processing, acquired superior recognition skills for horses. To compare the nature of face and horse processing, we utilised the inversion manipulation, known to disproportionally affect faces compared to other objects, with both faces and horses. O.H's performance was compared to data obtained from two control groups that were either horse experts, or non-experts. As expected, both control groups exhibited the face inversion effect, while O.H did not show the effect, but importantly, none of the participants showed an inversion effect for horses. Finally, gaze behaviour toward upright and inverted faces and horses was indicative of visual skill but in a distinct fashion for each category. Particularly, both control groups showed different gaze patterns for upright compared to inverted faces, while O.H presented a similar gaze pattern for the two orientations that differed from that of the two control groups. In contrast, O.H and the horse experts exhibited a similar gaze pattern for upright and inverted horses, while non-experts showed different gaze patterns for different orientations. Taken together, these results suggest that visual expertise can be acquired independently from the mechanisms mediating face recognition. |
Kimberly B. Weldon; Anina N. Rich; Alexandra Woolgar; Mark A. Williams Disruption of foveal space impairs discrimination of peripheral objects Journal Article In: Frontiers in Psychology, vol. 7, pp. 699, 2016. @article{Weldon2016, Visual space is retinotopically mapped such that peripheral objects are processed in a cortical region outside the region that represents central vision. Despite this well-known fact, neuroimaging studies have found information about peripheral objects in the foveal confluence, the cortical region representing the fovea. Further, this information is behaviorally relevant: disrupting the foveal confluence using transcranial magnetic stimulation impairs discrimination of peripheral objects at time-points consistent with a disruption of feedback. If the foveal confluence receives feedback of information about peripheral objects to boost vision, there should be behavioral consequences of this phenomenon. Here, we tested the effect of foveal distractors at different stimulus onset asynchronies (SOAs) on discrimination of peripheral targets. Participants performed a discrimination task on target objects presented in the periphery while fixating centrally. A visual distractor presented at the fovea ~100ms after presentation of the targets disrupted performance more than a central distractor presented at other SOAs. This was specific to a central distractor; a peripheral distractor at the same time point did not have the same effect. These results are consistent with the claim that foveal retinotopic cortex is recruited for extra-foveal perception. This study describes a new paradigm for investigating the nature of the foveal feedback phenomenon and demonstrates the importance of this feedback in peripheral vision. |
Laura Jean Wells; Steven M. Gillespie; Pia Rotshtein Identification of emotional facial expressions: Effects of expression, intensity, and sex on eye gaze Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0168307, 2016. @article{Wells2016, The identification of emotional expressions is vital for social interaction, and can be affected by various factors, including the expressed emotion, the intensity of the expression, the sex of the face, and the gender of the observer. This study investigates how these factors affect the speed and accuracy of expression recognition, as well as dwell time on the two most significant areas of the face: the eyes and the mouth. Participants were asked to identify expressions from female and male faces displaying six expressions (anger, disgust, fear, happiness, sadness, and surprise), each with three levels of intensity (low, moderate, and normal). Overall, responses were fastest and most accurate for happy expressions, but slowest and least accurate for fearful expressions. More intense expressions were also classified most accurately. Reaction time showed a different pattern, with slowest response times recorded for expressions of moderate intensity. Overall, responses were slowest, but also most accurate, for female faces. Relative to male observers, women showed greater accuracy and speed when recognizing female expressions. Dwell time analyses revealed that attention to the eyes was about three times greater than on the mouth, with fearful eyes in particular attracting longer dwell times. The mouth region was attended to the most for fearful, angry, and disgusted expressions and least for surprise. These results extend upon previous findings to show important effects of expression, emotion intensity, and sex on expression recognition and gaze behaviour, and may have implications for understanding the ways in which emotion recognition abilities break down. |
Dorothea Wendt; Torsten Dau; Jens Hjortkjær Impact of background noise and sentence complexity on processing demands during sentence comprehension Journal Article In: Frontiers in Psychology, vol. 7, pp. 345, 2016. @article{Wendt2016, Speech comprehension in adverse listening conditions can be effortful even when speech is fully intelligible. Acoustical distortions typically make speech comprehension more effortful, but effort also depends on linguistic aspects of the speech signal, such as its syntactic complexity. In the present study, pupil dilations, and subjective effort ratings were recorded in 20 normal-hearing participants while performing a sentence comprehension task. The sentences were either syntactically simple (subject-first sentence structure) or complex (object-first sentence structure) and were presented in two levels of background noise both corresponding to high intelligibility. A digit span and a reading span test were used to assess individual differences in the participants' working memory capacity (WMC). The results showed that the subjectively rated effort was mostly affected by the noise level and less by syntactic complexity. Conversely, pupil dilations increased with syntactic complexity but only showed a small effect of the noise level. Participants with higher WMC showed increased pupil responses in the higher-level noise condition but rated sentence comprehension as being less effortful compared to participants with lower WMC. Overall, the results demonstrate that pupil dilations and subjectively rated effort represent different aspects of effort. Furthermore, the results indicate that effort can vary in situations with high speech intelligibility. |
Jessica Werthmann; Anita Jansen; Anne Roefs Make up your mind about food: A healthy mindset attenuates attention for high-calorie food in restrained eaters Journal Article In: Appetite, vol. 105, pp. 53–59, 2016. @article{Werthmann2016, Attention bias for food could be a cognitive pathway to overeating in obesity and restrained eating. Yet, empirical evidence for individual differences (e.g., in restrained eating and body mass index) in attention bias for food is mixed. We tested experimentally if temporarily induced health versus palatability mindsets influenced attention bias for food, and whether restrained eating moderated this relation. After manipulating mindset (health vs. palatability) experimentally, food-related attention bias was measured by eye-movements (EM) and response latencies (RL) during a visual probe task depicting high-calorie food and non-food. Restrained eating was assessed afterwards. A significant interaction of mindset and restrained eating on RL bias emerged, β = 0.36, t(58) = 2.05 |
Gregory L. West; Sarah Lippé The development of inhibitory saccadic trajectory deviations correlates with measures of antisaccadic inhibition Journal Article In: NeuroReport, vol. 27, pp. 1196–1201, 2016. @article{West2016, Chronological age is related positively to a participant's ability to inhibit distracting information. Inhibition can be measured using the trajectory deviation of a saccade. Saccadic curvature away from distracting visual information is controlled through top–down inhibition mediated by the frontal eye fields. In the present study, we aimed to further test the saccadic trajectory deviation paradigm's sensitivity to the development of frontal inhibitory procuresses by comparing its measure of saccadic inhibition with that of a widely used paradigm, namely, the antisaccade task. We show that the later ‘inhibition' phase of the trajectory deviation function correlated strongly with the measure of antisaccadic inhibition obtained in the same individuals. As expected, the earlier ‘capture' phase of the trajectory deviation function, which does not represent the involvement of frontal structures, did not correlate with antisaccadic inhibition. Further, both measures of frontal inhibition increased with chronological age. |
Nicole Wetzel; David Buttelmann; Andy Schieler; Andreas Widmann Infant and adult pupil dilation in response to unexpected sounds Journal Article In: Developmental Psychobiology, vol. 58, no. 3, pp. 382–392, 2016. @article{Wetzel2016, Surprisingly occurring sounds outside the focus of attention can involuntarily capture attention. This study focuses on the impact of deviant sounds on the pupil size as a marker of auditory involuntary attention in infants. We presented an oddball paradigm including four types of deviant sounds within a sequence of repeated standard sounds to 14-month-old infants and to adults. Environmental and noise deviant sounds elicited a strong pupil dilation response (PDR) in both age groups. In contrast, moderate frequency deviants elicited a significant PDR in adults only. Moreover, a principal component analysis revealed two components underlying the PDR. Component scores differ, depending on deviant types, between age groups. Results indicate age effects of parasympathetic inhibition and sympathetic activation of the pupil size caused by deviant sounds with a high arousing potential. Results demonstrate that the PDR is a sensitive tool for the investigation of involuntary attention to sounds in preverbal children. |
Alex L. White; Martin Rolfs Oculomotor inhibition covaries with conscious detection Journal Article In: Journal of Neurophysiology, vol. 116, pp. 1507–1521, 2016. @article{White2016, Saccadic eye movements occur frequently even during attempted fixation, but they halt momentarily when a new stimulus appears. Here, we demonstrate that this rapid, involuntary “oculomotor freezing” reflex is yoked to fluctuations in explicit visual perception. Human observers reported the presence or absence of a brief visual stimulus while we recorded microsaccades, small spontaneous eye movements. We found that microsaccades were reflexively inhibited if and only if the observer reported seeing the stimulus, even when none was present. By apply- ing a novel Bayesian classification technique to patterns of microsac- cades on individual trials, we were able to decode the reported state of perception more accurately than the state of the stimulus (present vs. absent). Moreover, explicit perceptual sensitivity and the oculomotor reflex were both susceptible to orientation-specific adaptation. The adaptation effects suggest that the freezing reflex is mediated by signals processed in the visual cortex before reaching oculomotor control centers rather than relying on a direct subcortical route, as some previous research has suggested. We conclude that the reflexive inhibition of microsaccades immediately and inadvertently reveals when the observer becomes aware of a change in the environment. By providing an objective measure of conscious perceptual detection that does not require explicit reports, this finding opens doors to clinical applications and further investigations of perceptual awareness. |
J. Kael White; Ilya E. Monosov Neurons in the primate dorsal striatum signal the uncertainty of object-reward associations Journal Article In: Nature Communications, vol. 7, pp. 12735, 2016. @article{White2016b, To learn, obtain reward and survive, humans and other animals must monitor, approach and act on objects that are associated with variable or unknown rewards. However, the neuronal mechanisms that mediate behaviours aimed at uncertain objects are poorly understood. Here we demonstrate that a set of neurons in an internal-capsule bordering regions of the primate dorsal striatum, within the putamen and caudate nucleus, signal the uncertainty of object– reward associations. Their uncertainty responses depend on the presence of objects asso- ciated with reward uncertainty and evolve rapidly as monkeys learn novel object–reward associations. Therefore, beyond its established role in mediating actions aimed at known or certain rewards, the dorsal striatum also participates in behaviours aimed at reward-uncertain objects. |
Farahnaz A. Wick; Tyler W. Garaas; Marc Pomplun Saccadic adaptation alters the attentional field Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 568, 2016. @article{Wick2016, It is currently unknown whether changes to the oculomotor system can induce changes to the distribution of spatial attention around a fixated target. Previous studies have used perceptual performance tasks to show that adaptation of saccadic eye movements affects dynamic properties of visual attention, in particular, attentional shifts to a cued location. In this study, we examined the effects of saccadic adaptation on the static distribution of visual attention around fixation (attentional field). We used the classic double step adaptation procedure and a flanker task to test for differences in the attentional field after forward and backward adaptation. RT measures revealed that the shape of the attentional field changed significantly after backward adaptation as shown through altered interference from distracters at different eccentricities but not after forward adaptation. This finding reveals that modification of saccadic amplitudes can affect metrics of not only dynamic properties of attention but also its static properties. A major implication is that the neural mechanisms underlying fundamental selection mechanisms and the oculomotor system can reweight each other. |
Renée M. Visser; Michelle I. C. Haan; Tinka Beemsterboer; Pia Haver; Merel Kindt; H. Steven Scholte Quantifying learning-dependent changes in the brain: Single-trial multivoxel pattern analysis requires slow event-related fMRI Journal Article In: Psychophysiology, vol. 53, no. 8, pp. 1117–1127, 2016. @article{Visser2016, Single-trial analysis is particularly useful for assessing cognitive processes that are intrinsically dynamic, such as learning. Studying these processes with fMRI is problematic, as the low signal-to-noise ratio of fMRI requires the averaging over multiple trials, obscuring trial-by-trial changes in neural activation. The superior sensitivity of multivoxel pattern analysis over univariate analyses has opened up new possibilities for single-trial analysis, but this may require different fMRI designs. Here, we measured fMRI and pupil dilation responses during discriminant aversive conditioning, to assess associative learning in a trial-by-trial manner. The impact of design choices was examined by varying trial spacing and trial order in a series of five experiments (total n = 66), while keeping stimulus duration constant (4.5 s). Our outcome measure was the change in similarity between neural response patterns related to two consecutive presentations of the same stimulus (within-stimulus) and between patterns related to pairs of different stimuli (between-stimulus) that shared a specific outcome (electric stimulation vs. no consequence). This trial-by-trial similarity analysis revealed clear single-trial learning curves in conditions with intermediate (8.1-12.6 s) and long (16.5-18.4 s) intervals, with effects being strongest in designs with long intervals and counterbalanced stimulus presentation. No learning curves were observed in designs with shorter intervals (1.6-6.1 s), indicating that rapid event-related designs-at present, the most common designs in fMRI research-are not suited for single-trial pattern analysis. These findings emphasize the importance of deciding on the type of analysis prior to data collection. |
Andrej Vlasenko; Tadas Limba; Mindaugas Kiškis; Gintarė Gulevičiūtė Research on human emotion while playing a computer game using pupil recognition technology. Journal Article In: TEM Journal, vol. 5, no. 4, pp. 417–423, 2016. @article{Vlasenko2016, The article presents the results of an experiment during which the participants were playing an online game (poker), and while playing the game, a special video cam was recording the diameters of the player's eye pupils. Diameter data and calculations were based on these records with the aid of a computer program; then, diagrams of the diameter changes in the players' pupils were created (built) depending on the game situation. The study was conducted in a real life situation, when the players were playing online poker. The results of the study point out the connection between the changes in the psycho-emotional state of the players and the changes in their pupil diameters, where the emotional state is a critical factor affecting the operation of such systems. |
Melissa L. -H. Võ; Avigael M. Aizenman; Jeremy M. Wolfe You think you know where you looked? You better look again Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 42, no. 10, pp. 1477–1481, 2016. @article{Vo2016, People are surprisingly bad at knowing where they have looked in a scene. We tested participants' ability to recall their own eye movements in 2 experiments using natural or artificial scenes. In each experiment, participants performed a change-detection (Exp.1) or search (Exp.2) task. On 25% of trials, after 3 seconds of viewing the scene, participants were asked to indicate where they thought they had just fixated. They responded by making mouse clicks on 12 locations in the unchanged scene. After 135 trials, observers saw 10 new scenes and were asked to put 12 clicks where they thought someone else would have looked. Although observers located their own fixations more successfully than a random model, their performance was no better than when they were guessing someone else's fixations. Performance with artificial scenes was worse, though judging one's own fixations was slightly superior. Even after repeating the fixation-location task on 30 scenes immediately after scene viewing, performance was far from the prediction of an ideal observer. Memory for our own fixation locations appears to add next to nothing beyond what common sense tells us about the likely fixations of others. These results have important implications for socially important visual search tasks. For example, a radiologist might think he has looked at "everything" in an image, but eye tracking data suggest that this is not so. Such shortcomings might be avoided by providing observers with better insights of where they have looked. (PsycINFO Database Record |
Dimitris Voudouris; Alexander Goettker; Stefanie Mueller; Katja Fiehler Kinesthetic information facilitates saccades towards proprioceptive-tactile targets Journal Article In: Vision Research, vol. 122, pp. 73–80, 2016. @article{Voudouris2016, Saccades to somatosensory targets have longer latencies and are less accurate and precise than saccades to visual targets. Here we examined how different somatosensory information influences the planning and control of saccadic eye movements. Participants fixated a central cross and initiated a saccade as fast as possible in response to a tactile stimulus that was presented to either the index or the middle fingertip of their unseen left hand. In a static condition, the hand remained at a target location for the entire block of trials and the stimulus was presented at a fixed time after an auditory tone. Therefore, the target location was derived only from proprioceptive and tactile information. In a moving condition, the hand was first actively moved to the same target location and the stimulus was then presented immediately. Thus, in the moving condition additional kinesthetic information about the target location was available. We found shorter saccade latencies in the moving compared to the static condition, but no differences in accuracy or precision of saccadic endpoints. In a second experiment, we introduced variable delays after the auditory tone (static condition) or after the end of the hand movement (moving condition) in order to reduce the predictability of the moment of the stimulation and to allow more time to process the kinesthetic information. Again, we found shorter latencies in the moving compared to the static condition but no improvement in saccade accuracy or precision. In a third experiment, we showed that the shorter saccade latencies in the moving condition cannot be explained by the temporal proximity between the relevant event (auditory tone or end of hand movement) and the moment of the stimulation. Our findings suggest that kinesthetic information facilitates planning, but not control, of saccadic eye movements to proprioceptive-tactile targets. |
Dimitris Voudouris; Jeroen B. J. Smeets; Eli Brenner Fixation biases towards the index finger in almost-natural grasping Journal Article In: PLoS ONE, vol. 11, no. 1, pp. e0146864, 2016. @article{Voudouris2016a, We use visual information to guide our grasping movements. When grasping an object with a precision grip, the two digits need to reach two different positions more or less simulta- neously, but the eyes can only be directed to one position at a time. Several studies that have examined eye movements in grasping have found that people tend to direct their gaze near where their index finger will contact the object. Here we aimed at better understanding why people do so by asking participants to lift an object off a horizontal surface. They were to grasp the object with a precision grip while movements of their hand, eye and head were recorded. We confirmed that people tend to look closer to positions that a digit needs to reach more accurately. Moreover, we show that where they look as they reach for the object depends on where they were looking before, presumably because they try to minimize the time during which the eyes are moving so fast that no new visual information is acquired. Most importantly, we confirmed that people have a bias to direct gaze towards the index fin- ger's contact point rather than towards that of the thumb. In our study, this cannot be explained by the index finger contacting the object before the thumb. Instead, it appears to be because the index finger moves to a position that is hidden behind the object that is grasped, probably making this the place at which one is most likely to encounter unex- pected problems that would benefit from visual guidance. However, this cannot explain the bias that was found in previous studies, where neither contact point was hidden, so it cannot be the only explanation for the bias. |
Basil Wahn; Daniel P. Ferris; W. David Hairston; Peter König Pupil sizes scale with attentional load and task experience in a multiple object tracking task Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0168087, 2016. @article{Wahn2016a, Previous studies have related changes in attentional load to pupil size modulations. How-ever, studies relating changes in attentional load and task experience on a finer scale to pupil size modulations are scarce. Here, we investigated how these changes affect pupil sizes. To manipulate attentional load, participants covertly tracked between zero and five objects among several randomly moving objects on a computer screen. To investigate effects of task experience, the experiment was conducted on three consecutive days. We found that pupil sizes increased with each increment in attentional load. Across days, we found systematic pupil size reductions. We compared the model fit for predicting pupil size modulations using attentional load, task experience, and task performance as predictors. We found that a model which included attentional load and task experience as predictors had the best model fit while adding performance as a predictor to this model reduced the overall model fit. Overall, results suggest that pupillometry provides a viable metric for pre-cisely assessing attentional load and task experience in visuospatial tasks. |
Basil Wahn; Peter König In: Frontiers in Integrative Neuroscience, vol. 10, pp. 13, 2016. @article{Wahn2016, Humans constantly process and integrate sensory input from multiple sensory modalities. However, the amount of input that can be processed is constrained by limited attentional resources. A matter of ongoing debate is whether attentional resources are shared across sensory modalities, and whether multisensory integration is dependent on attentional resources. Previous research suggested that the distribution of attentional resources across sensory modalities depends on the the type of tasks. Here, we tested a novel task combination in a dual task paradigm: Participants performed a self-terminated visual search task and a localization task in either separate sensory modalities (i.e., haptics and vision) or both within the visual modality. Tasks considerably interfered. However, participants performed the visual search task faster when the localization task was performed in the tactile modality in comparison to performing both tasks within the visual modality. This finding indicates that tasks performed in separate sensory modalities rely in part on distinct attentional resources. Nevertheless, participants integrated visuotactile information optimally in the localization task even when attentional resources were diverted to the visual search task. Overall, our findings suggest that visual search and tactile localization partly rely on distinct attentional resources, and that optimal visuotactile integration is not dependent on attentional resources. |
Stephen C. Walenchok; Michael C. Hout; Stephen D. Goldinger Implicit object naming in visual search: Evidence from phonological competition Journal Article In: Attention, Perception, and Psychophysics, vol. 78, no. 8, pp. 2633–2654, 2016. @article{Walenchok2016, During visual search, people are distracted by ob- jects that visually resemble search targets; search is impaired when targets and distractors share overlapping features. In this study, we examined whether a nonvisual form of similarity, overlapping object names, can also affect search performance. In three experiments, people searched for images of real-world objects (e.g., a beetle) among items whose names either all shared the same phonological onset (/bi/), or were phonolog- ically varied. Participants either searched for 1 or 3 potential targets per trial, with search targets designated either visually or verbally.We examined standard visual search (Experiments 1 and 3) and a self-paced serial search task wherein partici- pants manually rejected each distractor (Experiment 2). We hypothesized that people would maintain visual templates when searching for single targets, but would rely more on object names when searching for multiple items and when targets were verbally cued. This reliance on target names would make performance susceptible to interference from similar-sounding distractors. Experiments 1 and 2 showed the predicted interference effect in conditions with high mem- ory load and verbal cues. In Experiment 3, eye-movement results showed that phonological interference resulted from small increases in dwell time to all distractors. The results suggest that distractor names are implicitly activated during search, slowing attention disengagement when targets and distractors share similar names. |
Thomas S. A. Wallis; M. Bethge; Felix A. Wichmann Testing models of peripheral encoding using metamerism in an oddity paradigm Journal Article In: Journal of Vision, vol. 16, no. 2, pp. 1–30, 2016. @article{Wallis2016, Most of the visual field is peripheral, and the periphery encodes visual input with less fidelity compared to the fovea. What information is encoded, and what is lost in the visual periphery? A systematic way to answer this question is to determine how sensitive the visual system is to different kinds of lossy image changes compared to the unmodified natural scene. If modified images are indiscriminable from the original scene, then the information discarded by the modification is not important for perception under the experimental conditions used. We measured the detectability of modifications of natural image structure using a temporal three-alternative oddity task, in which observers compared modified images to original natural scenes.We consider two lossy image transformations, Gaussian blur and Portilla and Simoncelli texture synthesis. Although our paradigm demonstrates metamerism (physically different images that appear the same) under some conditions, in general we find that humans can be capable of impressive sensitivity to deviations from natural appearance. The representations we examine here do not preserve all the information necessary to match the appearance of natural scenes in the periphery. |
Helena X. Wang; Shlomit Yuval-Greenberg; David J. Heeger Suppressive interactions underlying visually evoked fixational saccades Journal Article In: Vision Research, vol. 118, no. 9, pp. 70–82, 2016. @article{Wang2016d, Small saccades occur frequently during fixation, and are coupled to changes in visual stimulation and cognitive state. Neurophysiologically, fixational saccades reflect neural activity near the foveal region of a continuous visuomotor map. It is well known that competitive interactions between neurons within visuomotor maps contribute to target selection for large saccades. Here we asked how such interactions in visuomotor maps shape the rate and direction of small fixational saccades. We measured fixational saccades during periods of prolonged fixation while presenting pairs of visual stimuli (parafoveal: 0.8° eccentricity; peripheral: 5° eccentricity) of various contrasts. Fixational saccade direction was biased toward locations of parafoveal stimuli but not peripheral stimuli, ~100-250 ms following stimulus onset. The rate of fixational saccades toward parafoveal stimuli (congruent saccades) increased systematically with parafoveal stimulus contrast, and was suppressed by the simultaneous presentation of a peripheral stimulus. The suppression was best characterized as a combination of two processes: a subtractive suppression of the overall fixational saccade rate and a divisive suppression of the direction bias. These results reveal the nature of suppressive interactions within visuomotor maps and constrain models of the population code for fixational saccades. |
Lijing Wang; Xueli He; Yingchun Chen Quantitative relationship model between workload and time pressure under different flight operation tasks Journal Article In: International Journal of Industrial Ergonomics, vol. 54, pp. 93–102, 2016. @article{Wang2016f, The goal of this study was to establish a quantitative relationship model between workload and task demand under different tasks, when time pressure was set as the main influential factor to the task demand, with three workload measurement parameters. The workload "redline" was also analyzed and determined with the relationship models between the workload measurement parameters and time pressure. The experiment was designed with three different tasks under different time pressures. Three workload measurement parameters (subjective evaluation workload, accuracy and pupil diameter) and the subjective feeling threshold of time pressure were measured experimentally and then used in a comprehensive analysis for the relationship model. The data analysis result showed significant differences in workload under different time pressures, but workload was not affected by the task type. With a time pressure of 0.8, participants felt a sense of time urgency and the accuracy decreased by approximately 85%. The results demonstrate that the subjective evaluation workload, accuracy and pupil diameter can be used as the measurement parameters for the workload under different time pressures and for different tasks. Thus, for a time pressure of 0.8, an accuracy of 80%-85% was determined as the workload "redline". Linear relationships were found between subjective evaluation workload, and pupil diameter and time pressure, and a quadratic curve relationship was found between accuracy and time pressure. Workload prediction can thus be performed using these relationship models between workload and time pressure. |
Yi Xia; Yusuke Morimoto; Yasuki Noguchi Retrospective triggering of conscious perception by an interstimulus interaction Journal Article In: Journal of Vision, vol. 16, pp. 1–8, 2016. @article{Xia2016, Attention facilitates conscious perception of a visual stimulus at an attended location. Interestingly, a recent study (using the Posner spatial-cueing task) reported that attention facilitated conscious perception even when it was cued after a stimulus was gone (postcued- attention or retroperception effect). Here, we show that this effect can be induced without any contribution of attention. Contrary to previous situations, we fixed a position of a target (Gabor patch) and cue (luminance change of a circle encompassing the target) across trials so that subjects always could allocate their full attention to the target position. The cue (luminance change) improved objective and subjective visibility of the nearby target even when it was given ;200 ms after the target's offset. This retrospective improvement was diminished when a shape of the cue was changed from a circle to a dot pattern, suggesting that the improvement emerged from a visual interaction (combinations of shapes) between the circular cue and target. Those results indicated that a local visual interaction between the target and cue is sufficient to trigger consciousness of the target, revealing a new type of retroperception effect mediated by sensory (nonattentional) mechanisms. |
Jue Xie; Camillo Padoa-Schioppa Neuronal remapping and circuit persistence in economic decisions Journal Article In: Nature Neuroscience, vol. 19, no. 6, pp. 855–861, 2016. @article{Xie2016, The orbitofrontal cortex plays a central role in good-based economic decisions. When subjects make choices, neurons in this region represent the identities and values of offered and chosen goods. Notably, choices in different behavioral contexts may involve a potentially infinite variety of goods. Thus a fundamental question concerns the stability versus flexibility of the decision circuit. Here we show in rhesus monkeys that neurons encoding the identity or the subjective value of particular goods in a given context 'remap' and become associated with different goods when the context changes. At the same time, the overall organization of the decision circuit and the function of individual cells remain stable across contexts. In particular, two neurons supporting the same decision in one context also support the same decision in different contexts. These results demonstrate how the same neural circuit can underlie economic decisions involving a large variety of goods. |
Ying-Zi Xiong; Xin-Yu Xie; Cong Yu Location and direction specificity in motion direction learning associated with a single-level method of constant stimuli Journal Article In: Vision Research, vol. 119, pp. 9–15, 2016. @article{Xiong2016, Recent studies reported significantly less location specificity in motion direction learning than in previous classical studies. The latter performed training with the method of constant stimuli containing a single level of direction difference. In contrast the former used staircase methods that varied the direction difference trial by trial. We suspect that extensive practice with a single direction difference could allow an observer to use some subtle local cues for direction discrimination. Such local cues may be unavailable at a new stimulus location, leading to higher location specificity. To test this hypothesis, we jittered slightly the directions of a stimulus pair by the same amount while keeping the direction difference constant, so as to disturb the potential local cues. We observed significantly more transfer of learning to untrained locations. The local cue effects may also explain the recent controversies regarding the finding that foveal motion direction learning becomes significantly more transferrable to a new direction with TPE (training-plus-exposure) training. One specific study by Zili Liu and collaborators that challenges this finding also used a single-level direction difference for training. We first replicated their results. But we found that if the directions of the stimulus pair were again jittered while the direction difference was kept constant, motion direction learning transferred significantly more to an orthogonal direction with TPE training. Our results thus demonstrate the importance of using appropriate psychophysical methods in training to reduce local-cue related specificity in perceptual learning. |
Scott Cheng Hsin Yang; Máté Lengyel; Daniel M. Wolpert Active sensing in the categorization of visual patterns Journal Article In: eLife, vol. 5, no. FEBRUARY2016, pp. 1–22, 2016. @article{Yang2016, Interpreting visual scenes typically requires us to accumulate information from multiple locations in a scene. Using a novel gaze-contingent paradigm in a visual categorization task, we show that participants' scan paths follow an active sensing strategy that incorporates information already acquired about the scene and knowledge of the statistical structure of patterns. Intriguingly, categorization performance was markedly improved when locations were revealed to participants by an optimal Bayesian active sensor algorithm. By using a combination of a Bayesian ideal observer and the active sensor algorithm, we estimate that a major portion of this apparent suboptimality of fixation locations arises from prior biases, perceptual noise and inaccuracies in eye movements, and the central process of selecting fixation locations is around 70% efficient in our task. Our results suggest that participants select eye movements with the goal of maximizing information about abstract categories that require the integration of information from multiple locations. |
Tao Yao; Stefan Treue; B. Suresh Krishna An attention-sensitive memory trace in macaque MT following saccadic eye movements Journal Article In: PLoS Biology, vol. 14, no. 2, pp. e1002390, 2016. @article{Yao2016, We experience a visually stable world despite frequent retinal image displacements induced by eye, head, and body movements. The neural mechanisms underlying this remain unclear. One mechanism that may contribute is transsaccadic remapping, in which the responses of some neurons in various attentional, oculomotor, and visual brain areas appear to anticipate the consequences of saccades. The functional role of transsaccadic remapping is actively debated, and many of its key properties remain unknown. Here, recording from two monkeys trained to make a saccade while directing attention to one of two spatial locations, we show that neurons in the middle temporal area (MT), a key locus in the motion-processing pathway of humans and macaques, show a form of transsaccadic remapping called a memory trace. The memory trace in MT neurons is enhanced by the allocation of top-down spatial attention. Our data provide the first demonstration, to our knowledge, of the influence of top-down attention on the memory trace anywhere in the brain. We find evidence only for a small and transient effect of motion direction on the memory trace (and in only one of two monkeys), arguing against a role for MT in the theoretically critical yet empirically contentious phenomenon of spatiotopic feature-comparison and adaptation transfer across saccades. Our data support the hypothesis that transsaccadic remapping represents the shift of attentional pointers in a retinotopic map, so that relevant locations can be tracked and rapidly processed across saccades. Our results resolve important issues concerning the perisaccadic representation of visual stimuli in the dorsal stream and demonstrate a significant role for top-down attention in modulating this representation. |
Sang-Hoon Yeo; David W. Franklin; Daniel M. Wolpert When optimal feedback control is not enough: Feedforward strategies are required for optimal control with active sensing Journal Article In: PLoS Computational Biology, vol. 12, no. 12, pp. e1005190, 2016. @article{Yeo2016, Movement planning is thought to be primarily determined by motor costs such as inaccuracy and effort. Solving for the optimal plan that minimizes these costs typically leads to specifying a time-varying feedback controller which both generates the movement and can optimally correct for errors that arise within a movement. However, the quality of the sensory feedback during a movement can depend substantially on the generated movement. We show that by incorporating such state-dependent sensory feedback, the optimal solution incorporates active sensing and is no longer a pure feedback process but includes a significant feedforward component. To examine whether people take into account such state-dependency in sensory feedback we asked people to make movements in which we controlled the reliability of sensory feedback. We made the visibility of the hand state-dependent, such that the visibility was proportional to the component of hand velocity in a particular direction. Subjects gradually adapted to such a sensory perturbation by making curved hand movements. In particular, they appeared to control the late visibility of the movement matching predictions of the optimal controller with state-dependent sensory noise. Our results show that trajectory planning is not only sensitive to motor costs but takes sensory costs into account and argues for optimal control of movement in which feedforward commands can play a significant role. |
Chen-Ping Yu; Justin T. Maxfield; Gregory J. Zelinsky Searching for category-consistent features: A computational approach to understanding visual category representation Journal Article In: Psychological Science, vol. 27, no. 6, pp. 870–884, 2016. @article{Yu2016a, This article introduces a generative model of category representation that uses computer vision methods to extract category-consistent features (CCFs) directly from images of category exemplars. The model was trained on 4,800 images of common objects, and CCFs were obtained for 68 categories spanning subordinate, basic, and superordinate levels in a category hierarchy. When participants searched for these same categories, targets cued at the subordinate level were preferentially fixated, but fixated targets were verified faster when they followed a basic-level cue. The subordinate- level advantage in guidance is explained by the number of target-category CCFs, a measure of category specificity that decreases with movement up the category hierarchy. The basic-level advantage in verification is explained by multiplying the number of CCFs by sibling distance, a measure of category distinctiveness. With this model, the visual representations of real-world object categories, each learned from the vast numbers of image exemplars accumulated throughout everyday experience, can finally be studied. |
Gongchen Yu; Baijie Xu; Yuchen Zhao; Beizhen Zhang; Mingpo Yang; Janis Y. Y. Kan; David M. Milstein; Dhushan Thevarajah; Michael C. Dorris Microsaccade direction reflects the economic value of potential saccade goals and predicts saccade choice Journal Article In: Journal of Neurophysiology, vol. 115, no. 2, pp. 741–751, 2016. @article{Yu2016b, Microsaccades are small-amplitude (typically <1°), ballistic eye movements that occur when attempting to fixate gaze. Initially thought to be generated randomly, it has recently been established that microsaccades are influenced by sensory stimuli, attentional processes, and certain cognitive states. Whether decision processes influence microsaccades, however, is unknown. Here, we adapted two classic economic tasks to examine whether microsaccades reflect evolving saccade decisions. Volitional saccade choices of monkey and human subjects provided a measure of the subjective value of targets. Importantly, analyses occurred during a period of complete darkness to minimize the known influence of sensory and attentional processes on microsaccades. As the time of saccadic choice approached, microsaccade direction became the following: 1) biased toward targets as a function of their subjective value and 2) predictive of upcoming, voluntary choice. Our results indicate that microsaccade direction is influenced by and is a reliable tell of evolving saccade decisions. Our results are consistent with dynamic decision processes within the midbrain superior colliculus; that is, microsaccade direction is influenced by the transition of activity toward caudal saccade regions associated with high saccade value and/or future saccade choice. |
Ulrike Zimmer; M H"ofler; Karl Koschutnig; Anja Ischebeck; Margit Höfler; Karl Koschutnig; Anja Ischebeck Neuronal interactions in areas of spatial attention reflect avoidance of disgust, but orienting to danger Journal Article In: NeuroImage, vol. 134, pp. 94–104, 2016. @article{Zimmer2016, For survival, it is necessary to attend quickly towards dangerous objects, but to turn away from something that is disgusting. We tested whether fear and disgust sounds direct spatial attention differently. Using fMRI, a sound cue (disgust, fear or neutral) was presented to the left or right ear. The cue was followed by a visual target (a small arrow) which was located on the same (valid) or opposite (invalid) side as the cue. Participants were required to decide whether the arrow pointed up- or downwards while ignoring the sound cue. Behaviorally, responses were faster for invalid compared to valid targets when cued by disgust, whereas the opposite pattern was observed for targets after fearful and neutral sound cues. During target presentation, activity in the visual cortex and IPL increased for targets invalidly cued with disgust, but for targets validly cued with fear which indicated a general modulation of activation due to attention. For the TPJ, an interaction in the opposite direction was observed, consistent with its role in detecting targets at unattended positions and in relocating attention. As a whole our results indicate that a disgusting sound directs spatial attention away from its location, in contrast to fearful and neutral sounds. |
2015 |
Craig Hedge; Klaus Oberauer; Ute Leonards Selection in spatial working memory is independent of perceptual selective attention, but they interact in a shared spatial priority map Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 8, pp. 2653–2668, 2015. @article{Hedge2015, We examined the relationship between the attentional selection of perceptual information and of information in working memory (WM) through four experiments, using a spatial WM-updating task. Participants remembered the locations of two objects in a matrix and worked through a sequence of updating operations, each mentally shifting one dot to a new location according to an arrow cue. Repeatedly updating the same object in two successive steps is typically faster than switching to the other object; this object switch cost reflects the shifting of attention in WM. In Experiment 1,the arrows were presented in random peripheral locations, drawing perceptual attention away from the selected object in WM. This manipulation did not eliminate the object switch cost, indicating that the mechanisms of perceptual selection do not underlie selection in WM. Experiments 2a and 2b corroborated the independence of selection observed in Experiment 1, but showed a benefit to reaction times when the placement of the arrow cue was aligned with the locations of relevant objects in WM. Experiment 2c showed that the same benefit also occurs when participants are not able to mark an updating location through eye fixations. Together, these data can be accounted for by a framework in which perceptual selection and selection in WM are separate mechanisms that interact through a shared spatial priority map. |
Giles M. Anderson; Glyn W. Humphreys Top-down expectancy versus bottom-up guidance in search for known color-form conjunctions Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 8, pp. 2622–2639, 2015. @article{Anderson2015, We assessed the effects of pairing a target object with its familiar color on eye movements in visual search, under conditions where the familiar color could or could not be predicted. In Experiment 1 participants searched for a yellow- or purple-colored corn target amongst aubergine distractors, half of which were yellow and half purple. Search was more efficient when the color of the target was familiar and early eye movements more likely to be directed to targets carrying a familiar color than an unfamiliar color. Ex- periment 2 introduced cues which predicted the target color at 80 % validity. Cue validity did not affect whether early fixations were to the target. Invalid cues, however, disrupted search efficiency for targets in an unfamiliar color whilst there was little cost to search efficiency for targets in their familiar color. These re- sults generalized across items with different colors (Experiment 3). The data are consistent with early pro- cesses in selection being automatically modulated in a bottom-up manner to targets in their familiar color, even when expectancies are set for other colors. |
Joanna E. Lewis; Mark B. Neider Fixation not required: Characterizing oculomotor attention capture for looming stimuli Journal Article In: Attention, Perception, and Psychophysics, vol. 77, no. 7, pp. 2247–2259, 2015. @article{Lewis2015, A stimulus moving toward us, such as a ball being thrown in our direction or a vehicle braking suddenly in front of ours, often represents a stimulus that requires a rapid response. Using a visual search task in which target and distractor items were systematically associated with a looming object, we explored whether this sort of looming motion captures attention, the nature of such capture using eye movement measures (overt/covert), and the extent to which such capture effects are more closely tied to motion onset or the motion itself. We replicated previous findings indicating that looming motion induces response time benefits and costs during visual search Lin, Franconeri, & Enns(Psychological Science 19(7): 686-693, 2008). These differences in response times were independent of fixation, indicating that these capture effects did not necessitate overt attentional shifts to a looming object for search benefits or costs to occur. Interestingly, we found no differences in capture benefits and costs associated with differences in looming motion type. Combined, our results suggest that capture effects associated with looming motion are more likely subserved by covert attentional mechanisms rather than overt mechanisms, and attention capture for looming motion is likely related to motion itself rather than the onset of motion. |
Charles C. -F. Or; Matthew F. Peterson; Miguel P. Eckstein Initial eye movements during face identification are optimal and similar across cultures Journal Article In: Journal of Vision, vol. 15, no. 13, pp. 1–25, 2015. @article{Or2015, Culture influences not only human high-level cognitive processes but also low-level perceptual operations. Some perceptual operations, such as initial eye movements to faces, are critical for extraction of information supporting evolutionarily important tasks such as face identification. The extent of cultural effects on these crucial perceptual processes is unknown. Here, we report that the first gaze location for face identification was similar across East Asian and Western Caucasian cultural groups: Both fixated a featureless point between the eyes and the nose, with smaller between-group than within-group differences and with a small horizontal difference across cultures (8% of the interocular distance). We also show that individuals of both cultural groups initially fixated at a slightly higher point on Asian faces than on Caucasian faces. The initial fixations were found to be both fundamental in acquiring the majority of information for face identification and optimal, as accuracy deteriorated when observers held their gaze away from their preferred fixations. An ideal observer that integrated facial information with the human visual system's varying spatial resolution across the visual field showed a similar information distribution across faces of both races and predicted initial human fixations. The model consistently replicated the small vertical difference between human fixations to Asian and Caucasian faces but did not predict the small horizontal leftward bias of Caucasian observers. Together, the results suggest that initial eye movements during face identification may be driven by brain mechanisms aimed at maximizing accuracy, and less influenced by culture. The findings increase our understanding of the interplay between the brain's aims to optimally accomplish basic perceptual functions and to respond to sociocultural influences. |
Bram-Ernst Verhoef; Rufin Vogels; Peter Janssen; Leonardo Chelazzi Effects of microstimulation in the anterior intraparietal area during three-dimensional shape categorization Journal Article In: PLoS ONE, vol. 10, no. 8, pp. e0136543, 2015. @article{Verhoef2015, The anterior intraparietal area (AIP) of rhesus monkeys is part of the dorsal visual stream and contains neurons whose visual response properties are commensurate with a role in three-dimensional (3D) shape perception. Neuronal responses in AIP signal the depth structure of disparity-defined 3D shapes, reflect the choices of monkeys while they categorize 3D shapes, and mirror the behavioral variability across different stimulus conditions during 3D-shape categorization. However, direct evidence for a role of AIP in 3D-shape perception has been lacking. We trained rhesus monkeys to categorize disparity-defined 3D shapes and examined AIP's contribution to 3D-shape categorization by microstimulating in clusters of 3D-shape selective AIP neurons during task performance. We find that microstimulation effects on choices (monkey M1) and reaction times (monkey M1 and M2) depend on the 3D-shape preference of the stimulated site. Moreover, electrical stimulation of the same cells, during either the 3D-shape-categorization task or a saccade task, could affect behavior differently. Interestingly, in one monkey we observed a strong correlation between the strength of choice-related AIP activity (choice probabilities) and the influence of microstimulation on 3D-shape-categorization behavior (choices and reaction time). These findings propose AIP as part of the network responsible for 3D-shape perception. The results also show that the anterior intraparietal cortex contains cells with different tuning properties, i.e. 3D-shape- or saccade-related, that can be dynamically read out depending on the requirements of the task at hand. |
Zvi N. Roth; Ehud Zohary Position and identity information available in fMRI patterns of activity in human visual cortex Journal Article In: Journal of Neuroscience, vol. 35, no. 33, pp. 11559–11571, 2015. @article{Roth2015, Parietal cortex is often implicated in visual processing of actions. Action understanding is essentially abstract, specific to the type or goal of action, but greatly independent of variations in the perceived position of the action. If certain parietal regions are involved in action understanding, then we expect them to show these generalization and selectivity properties. However, additional functions of parietal cortex, such as self-action control, may impose other demands by requiring an accurate representation of the location of graspable objects. Therefore, the dimensions along which responses are modulated may indicate the functional role of specific parietal regions. Here, we studied the degree of position invariance and hand/object specificity during viewing of tool-grasping actions. To that end, we characterize the information available about location, hand, and tool identity in the patterns of fMRI activation in various cortical areas: early visual cortex, posterior intraparietal sulcus, anterior superior parietal lobule, and the ventral object-specific lateral occipital complex. Our results suggest a gradient within the human dorsal stream: along the posterior-anterior axis, position information is gradually lost, whereas hand and tool identity information is enhanced. This may reflect a gradual transformation of visual input from an initial retinotopic representation in early visual areas to an abstract, position-invariant representation of viewed action in anterior parietal cortex. |
Barbara Nordhjem; Constanza I. Kurman Petrozzelli; Nicolás Gravel; Remco J. Renken; Frans W. Cornelissen Eyes on emergence: Fast detection yet slow recognition of emerging images Journal Article In: Journal of Vision, vol. 15, no. 9, pp. 1–16, 2015. @article{Nordhjem2015, Visual object recognition occurs at the intersection of visual perception and visual cognition. It typically occurs very fast and it has therefore been difficult to disentangle its constituent processes. Recognition time can be extended when using images with emergent properties, suggesting they may help examining how visual recognition unfolds over time. Until now, their use has been constrained by limited availability. We used a set of stimuli with emergent properties—akin to the famous Gestalt image of a Dalmatian—in combination with eye tracking to examine the processes underlying object recognition. To test whether cognitive processes influenced eye movement behavior during recognition, an unprimed and three primed groups were included. Recognition times were relatively long (median ; 5s for the unprimed group), confirming the object's emergent properties. Surprisingly, within the first 500 ms, the majority of fixations were already aimed at the object. Computational models of saliency could not explain these initial fixations. This suggests that observers relied on image statistics not captured by saliency models. For the primed groups, recognition times were reduced. However, threshold-free cluster enhancement-based analysis of the time courses indicated that viewing behavior did not differ between the groups, neither during the initial viewing nor around the moment of recognition. This implies that eye movements are mainly driven by perceptual processes and not affected by cognition. It further suggests that priming mainly boosts the observer's confidence in the decision reached. We conclude that emerging images can be a useful tool to dissociate the perceptual and cognitive contributions to visual object recognition. |
Hayley Crawford; Joanna Moss; Giles M. Anderson; Chris Oliver; Joseph P. McCleery Implicit discrimination of basic facial expressions of positive/negative emotion in Fragile X syndrome and autism spectrum disorder Journal Article In: American Journal on Intellectual and Developmental Disabilities, vol. 120, no. 4, pp. 328–345, 2015. @article{Crawford2015, Fragile X syndrome (FXS) and autism spectrum disorders (ASD) are characterized by impaired social functioning. We examined the spontaneous discrimination of happy and disgusted facial expressions, from neutral faces, in individuals with FXS (n = 13 |
Ana Radonjić; Nicolas P. Cottaris; David H. Brainard Color constancy supports cross-illumination color selection Journal Article In: Journal of Vision, vol. 15, no. 6, pp. 1–19, 2015. @article{Radonjic2015, We rely on color to select objects as the targets of our actions (e.g., the freshest fish, the ripest fruit). To be useful for selection, color must provide accurate guidance about object identity across changes in illumination. Although the visual system partially stabilizes object color appearance across illumination changes, how such color constancy supports object selection is not understood. To study how constancy operates in real-life tasks, we developed a novel paradigm in which subjects selected which of two test objects presented under a test illumination appeared closer in color to a target object presented under a standard illumination. From subjects' choices, we inferred a selection-based match for the target via a variant of maximum likelihood difference scaling, and used it to quantify constancy. Selection-based constancy was good when measured using naturalistic stimuli, but was dramatically reduced when the stimuli were simplified, indicating that a naturalistic stimulus context is critical for good constancy. Overall, our results suggest that color supports accurate object selection across illumination changes when both stimuli and task match how color is used in real life. We compared our selection-based constancy results with data obtained using a classic asymmetric matching task and found that the adjustment-based matches predicted selection well for our stimuli and instructions, indicating that the appearance literature provides useful guidance for the emerging study of constancy in natural tasks. |
Paul Dassonville; Scott A. Reed The Two-Wrongs model explains perception-action dissociations for illusions driven by distortions of the egocentric reference frame Journal Article In: Frontiers in Human Neuroscience, vol. 9, pp. 140, 2015. @article{Dassonville2015, Several studies have demonstrated a dissociation of the effects of illusion on perception and action, with perception generally reported to be susceptible to illusions, while actions are seemingly immune. These findings have been interpreted to support Milner and Goodale's Two Visual Systems model, which proposes the existence of separate visual processing streams for perception and action. However, an alternative interpretation suggests that this type of behavioral dissociation will occur for any illusion that is caused by a distortion of the observer's egocentric reference frame, without requiring the existence of separate perception and action systems that are differently affected by the illusion. In this scenario, movements aimed at illusory targets will be accurate if they are guided within the same distorted reference frame used for target encoding, since the error of motor guidance will cancel with the error of encoding (hence, for actions, two wrongs do make a right). We further test this Two-Wrongs model by examining two illusions for which the hypothesis makes very different predictions: the rod-and-frame illusion (which affects perception but not actions) and the simultaneous-tilt illusion (which affects perception and actions equally). We demonstrate that the rod-and-frame illusion is caused by a distortion of the observer's egocentric reference frame suitable for the cancellation of errors predicted by the Two-Wrongs model. In contrast, the simultaneous-tilt illusion is caused by local interactions between stimulus elements within an undistorted reference frame, precluding the cancellation of errors associated with the Two-Wrongs model such that the illusion is reflected in both perception and actions. These results provide evidence for a class of illusions that lead to dissociations of perception and action through distortions of the observer's spatial reference frame, rather than through the actions of functionally separate visual processing streams. |
Eileen T. Crehan; Robert R. Althoff Measuring the stare-in-the-crowd effect: a new paradigm to study social perception Journal Article In: Behavior Research Methods, vol. 47, no. 4, pp. 994–1003, 2015. @article{Crehan2015, Social perceptual ability plays a key role in successful social functioning. Social interactions demand a number of simultaneous skills, one of which is the detection of self-directed gaze. This study demonstrates how the ability to accurately detect self-directed gaze, called the stare-in-the-crowd effect, can be studied using a new eye-tracking paradigm. A set of images was developed to test this effect using a group of healthy undergraduate students. Eye movements and pupil size were tracked while they viewed these images. Participants also completed behavioral measures about themselves. Results show that self-directed gaze results in significantly more looking by participants. Behavioral predictors of gaze behaviors were not identified, likely given the health of the sample. However, correlations with variables are reported to explore in future research. |
Mario Dalmaso; Giovanni Galfano; Luigi Castelli The impact of same- and other-race gaze distractors on the control of saccadic eye movements Journal Article In: Perception, vol. 44, no. 8-9, pp. 1020–1028, 2015. @article{Dalmaso2015, Two experiments were aimed at investigating whether the implementation of voluntary saccades in White participants could be modulated more strongly by gaze distractors embedded in White versus Black faces. Participants were instructed to make a rightward or leftward saccade, depending on a central directional cue. Saccade direction could be either congruent or incongruent with gaze direction of the distractor face. In Experiment 1, White faces produced greater interference on saccadic accuracy than Black faces when the averted-gaze face and cue onset were simultaneous rather than separated by a 900-ms asynchrony. In Experiment 2, two temporal intervals (50 ms vs. 1,000 ms) occurred between the initial presentation of the face with direct-gaze and the averted-gaze face onset, whereas the averted-gaze face and cue onset were synchronous. A greater interference emerged for White versus Black faces irrespective of the temporal interval. Overall, these findings suggest that saccadic generation system is sensitive to features of face stimuli conveying eye gaze. |
Ravi K. Das; Chandni Hindocha; Tom P. Freeman; Antonio I. Lazzarino; H. Valerie Curran; Sunjeev K. Kamboj Assessing the translational feasibility of pharmacological drug memory reconsolidation blockade with memantine in quitting smokers Journal Article In: Psychopharmacology, vol. 232, no. 18, pp. 3363–3374, 2015. @article{Das2015, RATIONALE: Preclinical reconsolidation research offers the first realistic opportunity to pharmacologically weaken the maladaptive memory structures that support relapse in drug addicts. N-methyl D-aspartate receptor (NMDAR) antagonism is a highly effective means of blocking drug memory reconsolidation. However, no research using this approach exists in human addicts. OBJECTIVES: The objective of this study was to assess the potential and clinical outcomes of blocking the reconsolidation of cue-smoking memories with memantine in quitting smokers. METHODS: Fifty-nine dependent and motivated to quit smokers were randomised to one of three groups receiving the following: (1) memantine with or (2) without reactivation of associative cue-smoking memories or (3) reactivation with placebo on their target quit day in a double-blind manner. Participants aimed to abstain from smoking for as long as possible. Levels of smoking and FTND score were assessed prior to intervention and up to a year later. Primary outcome was latency to relapse. Subjective craving measures and attentional bias to smoking cues were assessed in-lab. RESULTS: All study groups successfully reduced their smoking up to 3 months. Memantine in combination with smoking memory reactivation did not affect any measure of smoking outcome, reactivity or attention capture to smoking cues. CONCLUSIONS: Brief exposure to smoking cues with memantine did not appear to weaken these memory traces. These findings could be due to insufficient reconsolidation blockade by memantine or failure of exposure to smoking stimuli to destabilise smoking memories. Research assessing the treatment potential of reconsolidation blockade in human addicts should focus on identification of tolerable drugs that reliably block reward memory reconsolidation and retrieval procedures that reliably destabilise strongly trained memories. |
Anouk J. Brouwer; Jeroen B. J. Smeets; Tjerk P. Gutteling; I. Toni; W. Pieter Medendorp The Müller-Lyer illusion affects visuomotor updating in the dorsal visual stream Journal Article In: Neuropsychologia, vol. 77, pp. 119–127, 2015. @article{Brouwer2015, To guide our actions, the brain has developed mechanisms to code target locations in egocentric coordinates (i.e., with respect to the observer), and to update these when the observer moves. The latter mechanism, called visuomotor updating, is implemented in the dorsal visual stream of the brain. In contrast, the ventral visual stream is assumed to transform target locations into an allocentric reference frame that is highly sensitive to visual contextual illusions. Here, we tested the effect of the Müller-Lyer illusion on visuomotor updating in a double-step saccade task. Using the same paradigm in a 3T fMRI scanner, we investigated the effect of the illusion on the neural correlate of the updating process. Participants briefly viewed the Brentano version of the Müller-Lyer illusion with a target at its middle vertex, while fixating at one of the two endpoints of the illusion. Shortly after the disappearance of the stimulus, the eyes' fixation point moved to a position outside the illusion. After a delay, participants made a saccade to the remembered position of the target. The landing position of this saccade was systematically displaced in a manner congruent with the perceptual illusion, showing that visuomotor updating is affected by the illusion. fMRI results showed that the BOLD response in the occipito-parietal cortex (area V7) and the intraparietal sulcus related to planning of the saccade to the updated target was also modulated by the configuration of the illusion. This suggests that the dorsal visual stream represents perceived rather than physical locations of remembered saccade targets. |
Victor Lafuente; Mehrdad Jazayeri; Michael N. Shadlen Representation of accumulating evidence for a decision in two parietal areas Journal Article In: Journal of Neuroscience, vol. 35, no. 10, pp. 4306–4318, 2015. @article{Lafuente2015, Decisions are often made by accumulating evidence for and against the alternatives. The momentary evidence represented by sensory neurons is accumulated by downstream structures to form a decision variable, linking the evolving decision to the formation of a motor plan. When decisions are communicated by eye movements, neurons in the lateral intraparietal area (LIP) represent the accumulation of evidence bearing on the potential targets for saccades. We now show that reach-related neurons from the medial intraparietal area (MIP) exhibit a gradual modulation of their firing rates consistent with the representation of an evolving decision variable. When decisions were communicated by saccades instead of reaches, decision-related activity was attenuated in MIP, whereas LIP neurons were active while monkeys communicated decisions by saccades or reaches. Thus, for decisions communicated by a hand movement, a parallel flow of sensory information is directed to parietal areas MIP and LIP during decision formation. |
Alasdair D. F. Clarke; Micha Elsner; Hannah Rohde Giving good directions: Order of mention reflects visual salience Journal Article In: Frontiers in Psychology, vol. 6, pp. 1793, 2015. @article{Clarke2015, In complex stimuli, there are many different possible ways to refer to a specified target. Previous studies have shown that when people are faced with such a task, the content of their referring expression reflects visual properties such as size, salience and clutter. Here, we extend these findings and present evidence that (i) the influence of visual perception on sentence construction goes beyond content selection and in part determines the order in which different objects are mentioned and (ii) order of mention influences comprehension. Study 1 (a corpus study of reference productions) shows that when a speaker uses a relational description to mention a salient object, that object is treated as being in the common ground and is more likely to be mentioned first. Study 2 (a visual search study) asks participants to listen to referring expressions and find the specified target; in keeping with the above result, we find that search for easy-to-find targets is faster when the target is mentioned first, while search for harder-to-find targets is facilitated by mentioning the target later, after a landmark in a relational description. Our findings show that seemingly low-level and disparate mental “modules” like perception and sentence planning interact at a high level and in task-dependent ways. |
Justine Cléry; Olivier Guipponi; Soline Odouard; Claire Wardak; Suliann Ben Hamed Impact prediction by looming visual stimuli enhances tactile detection Journal Article In: Journal of Neuroscience, vol. 35, no. 10, pp. 4179–4189, 2015. @article{Clery2015, From an ecological point of view, approaching objects are potentially more harmful than receding objects. A predator, a dominant conspecific, or a mere branch coming up at high speed can all be dangerous if one does not detect them and produce the appropriate escape behavior fast enough. And indeed, looming stimuli trigger stereotyped defensive responses in both monkeys and human infants. However, while the heteromodal somatosensory consequences of visual looming stimuli can be fully predicted by their spatiotemporal dynamics, few studies if any have explored whether visual stimuli looming toward the face predictively enhance heteromodal tactile sensitivity around the expected time of impact and at its expected location on the body. In the present study, we report that, in addition to triggering a defensive motor repertoire, looming stimuli toward the face provide the nervous system with predictive cues that enhance tactile sensitivity on the face. Specifically, we describe an enhancement of tactile processes at the expected time and location of impact of the stimulus on the face. We additionally show that a looming stimulus that brushes past the face also enhances tactile sensitivity on the nearby cheek, suggesting that the space close to the face is incorporated into the subjects' body schema. We propose that this cross-modal predictive facilitation involves multisensory convergence areas subserving the representation of a peripersonal space and a safety boundary of self. |
Moreno I. Coco; Frank Keller Integrating mechanisms of visual guidance in naturalistic language production Journal Article In: Cognitive Processing, vol. 16, no. 2, pp. 131–150, 2015. @article{Coco2015a, Situated language production requires the integration of visual attention and linguistic processing. Previous work has not conclusively disentangled the role of perceptual scene information and structural sentence information in guiding visual attention. In this paper, we present an eye-tracking study that demonstrates that three types of guidance, perceptual, conceptual, and structural, interact to control visual attention. In a cued language production experiment, we manipulate perceptual (scene clutter) and conceptual guidance (cue animacy) and measure structural guidance (syntactic complexity of the utterance). Analysis of the time course of language production, before and during speech, reveals that all three forms of guidance affect the complexity of visual responses, quantified in terms of the entropy of attentional landscapes and the turbulence of scan patterns, especially during speech. We find that perceptual and conceptual guidance mediate the distribution of attention in the scene, whereas structural guidance closely relates to scan pattern complexity. Furthermore, the eye-voice span of the cued object and its perceptual competitor are similar; its latency mediated by both perceptual and structural guidance. These results rule out a strict interpretation of structural guidance as the single dominant form of visual guidance in situated language production. Rather, the phase of the task and the associated demands of cross-modal cognitive processing determine the mechanisms that guide attention. |
Russell Cohen Hoffing; Aaron R. Seitz Pupillometry as a glimpse into the neurochemical basis of human memory encoding Journal Article In: Journal of Cognitive Neuroscience, vol. 27, no. 4, pp. 765–774, 2015. @article{CohenHoffing2015, Neurochemical systems are well studied in animal learning; however, ethical issues limit methodologies to explore these systems in humans. Pupillometry provides a glimpse into the brain ʼs neurochemical systems, where pupil dynamics in monkeys have been linked with locus coeruleus activity, which releases norepinephrine (NE) throughout the brain. Here, we use pupil dynamics as a surrogate measure of neurochemical activity to explore the hypothesis that NE is involved in modulating memory encoding. We examine this using a task-irrelevant learning paradigm in which learning is boosted for stimuli temporally paired with task targets. We show that participants better recognize images that are paired with task targets than distractors and, in correspondence, that pupil size changes more for target-paired than distractor-paired images. To further investigate the hypothesis that NE nonspecifically guides learning for stimuli that are present with its release, a second procedure was used that employed an unexpected sound to activate the LC –NE system and induce pupil-size changes; results indicated a corresponding increase in memorization of images paired with the unexpected sounds. Together, these results suggest a relationship between the LC–NE system, pupil-size changes, and human memory encoding |
Noga Cohen; Natali Moyal; Avishai Henik Executive control suppresses pupillary responses to aversive stimuli Journal Article In: Biological Psychology, vol. 112, pp. 1–11, 2015. @article{Cohen2015a, Adaptive behavior depends on the ability to effectively regulate emotional responses. Continuous failure in the regulation of emotions can lead to heightened physiological reactions and to various psychopathologies. Recently, several behavioral and neuroimaging studies showed that exertion of executive control modulates emotion. Executive control is a high-order operation involved in goal-directed behavior, especially in the face of distractors or temptations. However, the role of executive control in regulating emotion-related physiological reactions is unknown. Here we show that exercise of executive control modulates reactivity of both the sympathetic and the parasympathetic components of the autonomic nervous system. Specifically, we demonstrate that both pupillary light reflex and pupil dilation for aversive stimuli are attenuated following recruitment of executive control. These findings offer new insights into the very basic mechanisms of emotion processing and regulation, and can lead to novel interventions for people suffering from emotion dysregulation psychopathologies. |
Joshua Correll; Bernd Wittenbrink; Matthew T. Crawford; Melody S. Sadler Stereotypic vision: How stereotypes disambiguate visual stimuli Journal Article In: Journal of Personality and Social Psychology, vol. 108, no. 2, pp. 219–233, 2015. @article{Correll2015, Three studies examined how participants use race to disambiguate visual stimuli. Participants performed a first-person-shooter task in which Black and White targets appeared holding either a gun or an innocuous object (e.g., a wallet). In Study 1, diffusion analysis (Ratcliff, 1978) showed that participants rapidly acquired information about a gun when it appeared in the hands of a Black target, and about an innocuous object in the hands of a White target. For counterstereotypic pairings (armed Whites, unarmed Blacks), participants acquired information more slowly. In Study 2, eye tracking showed that participants relied on more ambiguous information (measured by visual angle from fovea) when responding to stereotypic targets; for counterstereotypic targets, they achieved greater clarity before responding. In Study 3, participants were briefly exposed to targets (limiting access to visual information) but had unlimited time to respond. In spite of their slow, deliberative responses, they showed racial bias. This pattern is inconsistent with control failure and suggests that stereotypes influenced identification of the object. All 3 studies show that race affects visual processing by supplementing objective information. |
Patrick H. Cox; Maximilian Riesenhuber There is a "U" in clutter: Evidence for robust sparse codes underlying clutter tolerance in human vision Journal Article In: Journal of Neuroscience, vol. 35, no. 42, pp. 14148–14159, 2015. @article{Cox2015, The ability to recognize objects in clutter is crucial for human vision, yet the underlying neural computations remain poorly understood. Previous single-unit electrophysiology recordings in inferotemporal cortex in monkeys and fMRI studies of object-selective cortex in humans have shown that the responses to pairs of objects can sometimes be well described as a weighted average of the responses to the constituent objects. Yet, from a computational standpoint, it is not clear how the challenge of object recognition in clutter can be solved if downstream areas must disentangle the identity of an unknown number of individual objects from the confounded average neuronal responses. An alternative idea is that recognition is based on a subpopulation of neurons that are robust to clutter, i.e., that do not show response averaging, but rather robust object-selective responses in the presence of clutter. Here we show that simulations using the HMAX model of object recognition in cortex can fit the aforementioned single-unit and fMRI data, showing that the averaging-like responses can be understood as the result of responses of object-selective neurons to suboptimal stimuli. Moreover, the model shows how object recognition can be achieved by a sparse readout of neurons whose selectivity is robust to clutter. Finally, the model provides a novel prediction about human object recognition performance, namely, that target recognition ability should show a U-shaped dependency on the similarity of simultaneously presented clutter objects. This prediction is confirmed experimentally, supporting a simple, unifying model of how the brain performs object recognition in clutter.$backslash$n$backslash$nSIGNIFICANCE STATEMENT: The neural mechanisms underlying object recognition in cluttered scenes (i.e., containing more than one object) remain poorly understood. Studies have suggested that neural responses to multiple objects correspond to an average of the responses to the constituent objects. Yet, it is unclear how the identities of an unknown number of objects could be disentangled from a confounded average response. Here, we use a popular computational biological vision model to show that averaging-like responses can result from responses of clutter-tolerant neurons to suboptimal stimuli. The model also provides a novel prediction, that human detection ability should show a U-shaped dependency on target-clutter similarity, which is confirmed experimentally, supporting a simple, unifying account of how the brain performs object recognition in clutter. |