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2017 |
Stephan Geuter; Sabrina Boll; Falk Eippert; Christian Büchel Functional dissociation of stimulus intensity encoding and predictive coding of pain in the insula Journal Article In: eLife, vol. 6, pp. 1–22, 2017. @article{Geuter2017, <p>The computational principles by which the brain creates a painful experience from nociception are still unknown. Classic theories suggest that cortical regions either reflect stimulus intensity or additive effects of intensity and expectations, respectively. By contrast, predictive coding theories provide a unified framework explaining how perception is shaped by the integration of beliefs about the world with mismatches resulting from the comparison of these believes against sensory input. Using functional magnetic resonance imaging during a probabilistic heat pain paradigm, we investigated which computations underlie pain perception. Skin conductance, pupil dilation, and anterior insula responses to cued pain stimuli strictly followed the response patterns hypothesized by the predictive coding model, whereas posterior insula encoded stimulus intensity. This novel functional dissociation of pain processing within the insula together with previously observed alterations in chronic pain offer a novel interpretation of aberrant pain processing as disturbed weighting of predictions and prediction errors.</p> |
Anna C. Geuzebroek; Albert V. Berg Impaired visual competition in patients with homonymous visual field defects Journal Article In: Neuropsychologia, vol. 97, pp. 152–162, 2017. @article{Geuzebroek2017, Intense visual training can lead to partial recovery of visual field defects caused by lesions of the primary visual cortex. However, the standard visual detection and discrimination tasks, used to assess this recovery process tend to ignore the complexity of the natural visual environment, where multiple stimuli continuously interact. Visual competition is an essential component for natural search tasks and detecting unexpected events. Our study focused on visual decision-making and to what extent the recovered visual field can compete for attention with the ‘intact' visual field. Nine patients with visual field defects who had previously received visual discrimination training, were compared to healthy age-matched controls using a saccade target-selection paradigm, in which participants actively make a saccade towards the brighter of two flashed targets. To further investigate the nature of competition (feed-forward or feedback inhibition), we presented two flashes that reversed their intensity difference during the flash. Both competition between recovered visual field and intact visual field, as well as competition within the intact visual field, were assessed. Healthy controls showed the expected primacy effect; they preferred the initially brighter target. Surprisingly, choice behaviour, even in the patients' supposedly ‘intact' visual field, was significantly different from the control group for all but one. In the latter patient, competition was comparable to the controls. All other patients showed a significantly reduced preference to the brighter target, but still showed a small hint of primacy in the reversal conditions. The present results indicate that patients and controls have similar decision-making mechanisms but patients' choices are affected by a strong tendency to guess, even in the intact visual field. This tendency likely reveals slower integration of information, paired with a lower threshold. Current rehabilitation should therefore also include training focused on improving visual decision-making of the defective and the intact visual field. |
Saeideh Ghahghaei; Preeti Verghese Texture segmentation influences the spatial profile of presaccadic attention Journal Article In: Journal of Vision, vol. 17, no. 2, pp. 1–16, 2017. @article{Ghahghaei2017, Attention is important for selecting targets for action. Several studies have shown that attentional selection precedes eye movements to a target, and results in an enhanced sensitivity at the saccade goal. Typically these studies have used isolated targets on blank backgrounds, which are rare in real-world situations. Here, we examine the spatial profile of sensitivity around a saccade target on a textured background and how the influence of the surrounding context develops over time. We used two textured backgrounds: a uniform texture, and a concentric arrangement of an inner and an outer texture with orthogonal orientations. For comparison, we also measured sensitivity around the target on a blank background. The spatial profile of sensitivity was measured with a brief, dim, probe flashed around the saccade target. When the target was on a blank or a uniformly textured background, spatial sensitivity peaked near the target location around 350 ms after cue onset and declined with distance from the target. However, when the background was made up of an inner and outer texture, sensitivity to the inner texture was uniformly high, peaking at about 350 ms after cue onset, suggesting that the entire inner texture was selected along with the target. The enhancement of sensitivity on the inner texture was much smaller when observers attended the target covertly and performed the probe-detection task. Thus, our results suggest that the surface representation around the target is taken into account when an observer actively plans to interact with the target. |
Hildward Vandormael; Santiago Herce Castañón; Jan Balaguer; Vickie Li; Christopher Summerfield Robust sampling of decision information during perceptual choice Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 10, pp. 2771–2776, 2017. @article{Vandormael2017, Humans move their eyes to gather information about the visual world. However, saccadic sampling has largely been explored in paradigms that involve searching for a lone target in a cluttered array or natural scene. Here, we investigated the policy that humans use to overtly sample information in a perceptual decision task that required information from across multiple spatial locations to be combined. Participants viewed a spatial array of numbers and judged whether the average was greater or smaller than a reference value. Participants preferentially sampled items that were less diagnostic of the correct answer ("inlying" elements; that is, elements closer to the reference value). This preference to sample inlying items was linked to decisions, enhancing the tendency to give more weight to inlying elements in the final choice ("robust averaging"). These findings contrast with a large body of evidence indicating that gaze is directed preferentially to deviant information during natural scene viewing and visual search, and suggest that humans may sample information "robustly" with their eyes during perceptual decision-making. |
Gilles Vannuscorps; Alfonso Caramazza Typical predictive eye movements during action observation without effector-specific motor simulation Journal Article In: Psychonomic Bulletin & Review, vol. 24, no. 4, pp. 1152–1157, 2017. @article{Vannuscorps2017, When watching someone reaching to grasp an object, we typically gaze at the object before the agent's hand reaches it-that is, we make a ``predictive eye movement'' to the object. The received explanation is that predictive eye movements rely on a direct matching process, by which the observed action is mapped onto the motor representation of the same body movements in the observer's brain. In this article, we report evidence that calls for a reexamination of this account. We recorded the eye movements of an individual born without arms (D.C.) while he watched an actor reaching for one of two different-sized objects with a power grasp, a precision grasp, or a closed fist. D.C. showed typical predictive eye movements modulated by the actor's hand shape. This finding constitutes proof of concept that predictive eye movements during action observation can rely on visual and inferential processes, unaided by effector-specific motor simulation. |
Alejandra Vasquez-Rosati; Enzo P. Brunetti; Carmen Cordero; Pedro E. Maldonado Pupillary response to negative emotional stimuli is differentially affected in meditation practitioners Journal Article In: Frontiers in Human Neuroscience, vol. 11, pp. 209, 2017. @article{VasquezRosati2017, Clinically, meditative practices have become increasingly relevant, decreasing anxiety in patients and increasing antibody production. However, few studies have examined the physiological correlates, or effects of the incorporation of meditative practices. Because pupillary reactivity is a marker for autonomic changes and emotional processing, we hypothesized that the pupillary responses of mindfulness meditation practitioners (MP) and subjects without such practices (NM differ, reflecting different emotional processing. In a group of 11 MP and 9 NM, we recorded the pupil diameter using video-oculography while subjects explored images with emotional contents. Although both groups showed a similar pupillary response for positive and neutral images, negative images evoked a greater pupillary contraction and a weaker dilation in the MP group. Also, this group had faster physiological recovery to baseline levels. These results suggest that mindfulness meditation practices modulate the response of the autonomic nervous system, reflected in the pupillary response to negative images and faster physiological recovery to baseline levels, suggesting that pupillometry could be used to assess the potential health benefits of these practices in patients. |
Maryam Vaziri-Pashkam; Yaoda Xu Goal-directed visual processing differentially impacts human ventral and dorsal visual representations Journal Article In: Journal of Neuroscience, vol. 37, no. 36, pp. 8767–8782, 2017. @article{VaziriPashkam2017, Recent studies have challenged the ventral/“what” and dorsal/“where” two-visual-processing-pathway view by showing the existence of “what”and“where”information in both pathways. Is thetwo-pathwaydistinction still valid? Here,weexaminedhowgoal-directed visual information processing may differentially impact visual representations in these two pathways. Using fMRI and multivariate pattern analysis, in three experiments onhumanparticipants (57% females), by manipulating whether color or shape was task-relevant andhow they were conjoined, we examined shape-based object category decoding in occipitotemporal and parietal regions.Wefound that object category representations in all the regions examined were influenced by whether or not object shape was task-relevant. This task effect, however,tendedto decrease as task-relevantandirrelevant featuresweremoreintegrated, reflecting thewell-knownobject-based feature encoding. Interestingly, task relevance played a relatively minor role in driving the representational structures of early visual and ventral object regions. They were driven predominantly by variations in object shapes. In contrast, the effect of task was much greater in dorsal than ventral regions, with object category and task relevance both contributing significantly to the representational structures of the dorsal regions. These results showed that, whereas visual representations in the ventral pathway are more invariant and reflect “what an object is,” those in the dorsal pathway are more adaptive and reflect “what we do with it.” Thus, despite the existence of “what” and “where” information in both visual processing pathways, the two pathways may still differ fundamentally in their roles in visual infor- mation representation. |
Aaron Veldre; Denis Drieghe; Sally Andrews Spelling ability selectively predicts the magnitude of disruption in unspaced text reading Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 43, no. 9, pp. 1612–1628, 2017. @article{Veldre2017, We examined the effect of individual differences in written language proficiency on unspaced text reading in a large sample of skilled adult readers who were assessed on reading comprehension and spelling ability. Participants' eye movements were recorded as they read sentences containing a low or high frequency target word, presented with standard interword spacing, or in one of three unsegmented text conditions that either preserved or eliminated word boundary information. The average data replicated previous studies: unspaced text reading was associated with increased fixation durations, a higher number of fixations, more regressions, reduced saccade length, and an inflation of the word frequency effect. The individual differences results provided insight into the mechanisms contributing to these effects. Higher reading ability was associated with greater overall reading speed and fluency in all conditions. In contrast, spelling ability selectively modulated the effect of interword spacing with poorer spelling ability predicting greater difficulty across the majority of sentence- and word-level measures. These results suggest that high quality lexical representations allowed better spellers to extract lexical units from unfamiliar text forms, inoculating them against the disruptive effects of being deprived of spacing information. |
Bram-Ernst Verhoef; John H. R. Maunsell Attention-related changes in correlated neuronal activity arise from normalization mechanisms Journal Article In: Nature Neuroscience, vol. 20, no. 7, pp. 969–977, 2017. @article{Verhoef2017, Attention is believed to enhance perception by altering the activity-level correlations between pairs of neurons. How attention changes neuronal activity correlations is unknown. Using multielectrodes in monkey visual cortex, we measured spike-count correlations when single or multiple stimuli were presented and when stimuli were attended or unattended. When stimuli were unattended, adding a suppressive, nonpreferred stimulus beside a preferred stimulus increased spike-count correlations between pairs of similarly tuned neurons but decreased spike-count correlations between pairs of oppositely tuned neurons. A stochastic normalization model containing populations of oppositely tuned, mutually suppressive neurons explains these changes and also explains why attention decreased or increased correlations: as an indirect consequence of attention-related changes in the inputs to normalization mechanisms. Our findings link normalization mechanisms to correlated neuronal activity and attention, showing that normalization mechanisms shape response correlations and that these correlations change when attention biases normalization mechanisms. |
Laura Vilkaitė; Norbert Schmitt Reading collocations in an L2: Do collocation processing benefits extend to non-adjacent collocations? Journal Article In: Applied Linguistics, no. 2013, pp. 1–27, 2017. @article{Vilkaite2017, Various studies have consistently shown that collocations are processed faster than matched control phrases, both in L1 and in L2. Most of these studies focused on adjacent collocations (e.g. provide information). However, research in corpus linguistics normally uses a span to identify collocations (e.g. plus or minus four words), and these non-adjacent collocations (e.g. provide some of the information) occur very frequently in language. Nevertheless, how they are processed is less established. A recent study on reading non-adjacent collocations seems to suggest similar processing advantages as for adjacent collocations (Vilkaite 2016), but this study was limited to the performance of native speakers (NSs). The present study addresses the question of whether advanced non-native speakers (NNSs) also show processing advantages for non-adjacent collocations as NSs do. Forty advanced NNSs of English read collocations in either adjacent or non-adjacent conditions, and their eye movements were recorded. Mixed-effects analysis of their eye movements was carried out. The results suggest that NNSs read adjacent collocations faster than non-formulaic controls, but this facilitation almost disappears for non-adjacent collocations. |
Margarita Vinnikov; Robert S. Allison; Suzette Fernandes Gaze-contingent auditory displays for improved spatial attention in virtual reality Journal Article In: ACM Transactions on Computer-Human Interaction, vol. 24, no. 3, pp. 1–38, 2017. @article{Vinnikov2017, Virtual reality simulations of group social interactions are important for many applications, including the virtual treatment of social phobias, crowd and group simulation, collaborative virtual environments (VEs), and entertainment. In such scenarios, when compared to the real world, audio cues are often impoverished. As a result, users cannot rely on subtle spatial audio-visual cues that guide attention and enable effective social interactions in real-world situations. We explored whether gaze-contingent audio enhancement techniques driven by inferring audio-visual attention in virtual displays could be used to enable effective communication in cluttered audio VEs. In all of our experiments, we hypothesized that visual attention could be used as a tool to modulate the quality and intensity of sounds from multiple sources to efficiently and naturally select spatial sound sources. For this purpose, we built a gaze-contingent display (GCD) that allowed tracking of a user's gaze in real-time and modifying the volume of the speakers' voices contingent on the current region of overt attention. We compared six different techniques for sound modulation with a base condition providing no attentional modulation of sound. The techniques were compared in terms of source recognition and preference in a set of user studies. Overall, we observed that users liked the ability to control the sounds with their eyes. They felt that a rapid change in attenuation with attention but not the elimination of competing sounds (partial rather than absolute selection) was most natural. In conclusion, audio GCDs offer potential for simulating rich, natural social, and other interactions in VEs. They should be considered for improving both performance and fidelity in applications related to social behaviour scenarios or when the user needs to work with multiple audio sources of information. |
Olga Vintonyak; Martin Gorges; Hans Peter Müller; Elmar H. Pinkhardt; Albert C. Ludolph; Hans Jürgen Huppertz; Jan Kassubek Patterns of eye movement impairment correlate with regional brain atrophy in neurodegenerative Parkinsonism Journal Article In: Neurodegenerative Diseases, vol. 17, no. 4-5, pp. 117–126, 2017. @article{Vintonyak2017, Background: One common feature of neurodegenerative parkinsonism including Parkinson's disease (PD), multisys- tem atrophy (MSA), and progressive supranuclear palsy (PSP) is altered eye movement control. Characteristic regional structural atrophy patterns in MRI can be observed in PD, MSA, and PSP. Objective: To investigate the association be- tween eye movement disturbances and regional brain atro- phy in patients with PD, MSA, and PSP. Methods: High-reso lution 3-dimensional T1-weighted MRI images and video- oculographic recordings (EyeLink ® ) were obtained from 39 PD, 32 PSP, and 18 MSA patients and 24 matched healthy control subjects. Automatic regional volumetric assessment was performed using atlas-based volumetry (ABV). Results: The prevalence of saccadic intrusions as a measure of inhib- itory control was significantly increased in PD patients com- pared to controls ( p < 0.001) and negatively correlated with whole brain volume, cerebral brain volume, and occipital lobe volume ( p = 0.0057 |
Dong Wang; Fiona B. Mulvey; Jeff B. Pelz; Kenneth Holmqvist A study of artificial eyes for the measurement of precision in eye-trackers Journal Article In: Behavior Research Methods, vol. 49, no. 3, pp. 947–959, 2017. @article{Wang2017, The precision of an eye-tracker is critical to the correct identification of eye movements and their properties. To measure a system's precision, artificial eyes (AEs) are of- ten used, to exclude eye movements influencing the measure- ments. A possible issue, however, is that it is virtually impos- sible to construct AEs with sufficient complexity to fully rep- resent the human eye. To examine the consequences of this limitation, we tested currently used AEs from three manufac- turers of eye-trackers and compared them to a more complex model, using 12 commercial eye-trackers. Because precision can be measured in various ways, we compared different met- rics in the spatial domain and analyzed the power-spectral densities in the frequency domain. To assess how precision measurements compare in artificial and human eyes, we also measured precision using human recordings on the same eye- trackers. Our results show that the modified eye model pre- sented can cope with all eye-trackers tested and acts as a promising candidate for further development of a set ofAEs with varying pupil size and pupil–iris contrast. The spectral analysis ofboth the AE and human data revealed that human eye data have different frequencies that likely reflect the phys- iological characteristics of human eye movements. We also report the effects of sample selection methods for precision calculations. This study is part of the EMRA/COGAIN Eye Data Quality Standardization Project. |
Jiahui Wang; Pavlo D. Antonenko Instructor presence in instructional video: Effects on visual attention, recall, and perceived learning Journal Article In: Computers in Human Behavior, vol. 71, pp. 79–89, 2017. @article{Wang2017c, In an effort to enhance instruction and reach more students, educators design engaging online learning experiences, often in the form of online videos. While many instructional videos feature a picture-inpicture view of instructor, it is not clear how instructor presence influences learners' visual attention and what it contributes to learning and affect. Given this knowledge gap, this study explored the impact of instructor presence on learning, visual attention, and perceived learning in mathematics instructional videos of varying content difficulty. Thirty-six participants each viewed two 10-min-long mathematics videos (easy and difficult topics), with instructor either present or absent. Findings suggest that instructor attracted considerable visual attention, particularly when learners viewed the video on an easy topic. Although no significant difference in learning transfer was found for either topic, participants' recall of information from the video was better for easy topic when instructor was present. Finally, instructor presence positively influenced participants' perceived learning and satisfaction for both topics and led to a lower level of self-reported mental effort for difficult topic. |
Jianglan Wang; Jiao Zhao; Shoujing Wang; Rui Gong; Zhong Zheng; Longqian Liu Cognitive processing of orientation discrimination in anisometropic amblyopia Journal Article In: PLoS ONE, vol. 12, no. 10, pp. e0186221, 2017. @article{Wang2017f, Cognition is very important in our daily life. However, amblyopia has abnormal visual cogni- tion. Physiological changes of the brain during processes of cognition could be reflected with ERPs. So the purpose of this study was to investigate the speed and the capacity of resource allocation in visual cognitive processing in orientation discrimination task during monocular and binocular viewing conditions of amblyopia and normal control as well as the corresponding eyes of the two groups with ERPs. We also sought to investigate whether the speed and the capacity of resource allocation in visual cognitive processing vary with target stimuli at different spatial frequencies (3, 6 and 9 cpd) in amblyopia and normal control as well as between the corresponding eyes of the two groups. Fifteen mild to moderate aniso- metropic amblyopes and ten normal controls were recruited. Three-stimulus oddball para- digms of three different spatial frequency orientation discrimination tasks were used in monocular and binocular conditions in amblyopes and normal controls to elicit event-related potentials (ERPs). Accuracy (ACC), reaction time (RT), the latency of novelty P300 and P3b, and the amplitude of novelty P300 and P3b were measured. Results showed that RT was longer in the amblyopic eye than in both eyes of amblyopia and non-dominant eye in control. Novelty P300 amplitude was largest in the amblyopic eye, followed by the fellow eye, and smallest in both eyes of amblyopia. Novelty P300 amplitude was larger in the amblyopic eye than non-dominant eye and was larger in fellow eye than dominant eye. P3b latency was longer in the amblyopic eye than in the fellow eye, both eyes of amblyopia and non-dominant eye of control. P3b latency was not associated with RT in amblyopia. Neural responses of the amblyopic eye are abnormal at the middle and late stages of cognitive pro- cessing, indicating that the amblyopic eye needs to spend more time or integrate more resources to process the same visual task. Fellow eye and both eyes in amblyopia are slightly different from the dominant eye and both eyes in normal control at the middle and late stages of cognitive processing. Meanwhile, abnormal extents of amblyopic eye do not vary with three different spatial frequencies used in our study. |
Maya Zhe Wang; Benjamin Y. Hayden Reactivation of associative structure specific outcome responses during prospective evaluation in reward-based choices Journal Article In: Nature communications, vol. 8, pp. 15821, 2017. @article{Wang2017e, Before making a reward-based choice, we must evaluate each option. Some theories propose that prospective evaluation involves a reactivation of the neural response to the outcome. Others propose that it calls upon a response pattern that is specific to each underlying associative structure. We hypothesize that these views are reconcilable: during prospective evaluation, offers reactivate neural responses to outcomes that are unique to each associative structure; when the outcome occurs, this pattern is activated, simultaneously, with a general response to the reward. We recorded single-units from macaque orbitofrontal cortex (Area 13) in a riskless choice task with interleaved described and experienced offer trials. Here we report that neural activations to offers and their outcomes overlap, as do neural activations to the outcomes on the two trial types. Neural activations to experienced and described offers are unrelated even though they predict the same outcomes. Our reactivation theory parsimoniously explains these results. |
Shuhang Wang; Russell L. Woods; Francisco M. Costela; Gang Luo Dynamic gaze-position prediction of saccadic eye movements using a Taylor series Journal Article In: Journal of Vision, vol. 17, no. 14, pp. 3, 2017. @article{Wang2017d, Gaze-contingent displays have been widely used in vision research and virtual reality applications. Due to data transmission, image processing, and display preparation, the time delay between the eye tracker and the monitor update may lead to a misalignment between the eye position and the image manipulation during eye movements. We propose a method to reduce the misalignment using a Taylor series to predict the saccadic eye movement. The proposed method was evaluated using two large datasets including 219,335 human saccades (collected with an EyeLink 1000 system, 95% range from 1° to 32°) and 21,844 monkey saccades (collected with a scleral search coil, 95% range from 1° to 9°). When assuming a 10-ms time delay, the prediction of saccade movements using the proposed method could reduce the misalignment greater than the state-of-theart methods. The average error was about 0.93° for human saccades and 0.26° for monkey saccades. Our results suggest that this proposed saccade prediction method will create more accurate gaze-contingent displays. |
Xin Wang; Juan Wang; Jeffrey G. Malins In: Cognition, vol. 169, pp. 15–24, 2017. @article{Wang2017b, Although lexical tone is a highly prevalent phonetic cue in human languages, its role in bilingual spoken word recognition is not well understood. The present study investigates whether and how adult bilinguals, who use pitch contours to disambiguate lexical items in one language but not the other, access a tonal L1 when exclusively processing a non-tonal L2. Using the visual world paradigm, we show that Mandarin-English listeners automatically activated Mandarin translation equivalents of English target words such as ‘rain' (Mandarin ‘yu3'), and consequently were distracted by competitors whose segments and tones overlapped with the translations of English target words (‘feather', also ‘yu3' in Mandarin). Importantly, listeners were not distracted by competitors that overlapped with the translations of target words in all segments but not tone (‘fish'; Mandarin ‘yu2'), nor were they distracted by competitors that overlapped with the translations of target words in rime and tone (‘wheat', Mandarin ‘gu3'). These novel results demonstrate implicit access to L1 lexical representations through automatic/unconscious translation, as a result of cross-language top-down and/or lateral influence, and highlight the critical role of lexical tone activation in bilingual lexical access. |
Scott N. J. Watamaniuk; Japjot Bal; Stephen J. Heinen A subconscious interaction between fixation and anticipatory pursuit Journal Article In: Journal of Neuroscience, vol. 37, no. 47, pp. 2186–17, 2017. @article{Watamaniuk2017, Ocular smooth pursuit and fixation are typically viewed as separate systems, yet there is evidence that the brainstem fixation system inhibits pursuit. Here we present behavioral evidence that the fixation system modulates pursuit behavior outside of conscious awareness. Human observers (male and female) either pursued a small spot that translated across a screen, or fixated it as it remained stationary. As shown previously, pursuit trials potentiated the oculomotor system, producing anticipatory eye velocity on the next trial before the target moved that mimicked the stimulus-driven velocity. Randomly interleaving fixation trials reduced anticipatory pursuit, suggesting that a potentiated fixation system interacted with pursuit to suppress eye velocity in upcoming pursuit trials. The reduction was not due to passive decay of the potentiated pursuit signal because interleaving "blank" trials in which no target appeared did not reduce anticipatory pursuit. Interspersed short fixation trials reduced anticipation on long pursuit trials, suggesting that fixation potentiation was stronger than pursuit potentiation. Furthermore, adding more pursuit trials to a block did not restore anticipatory pursuit, suggesting that fixation potentiation was not overridden by certainty of an imminent pursuit trial but rather was immune to conscious intervention. To directly test whether cognition can override fixation suppression, we alternated pursuit and fixation trials to perfectly specify trial identity. Still, anticipatory pursuit did not rise above that observed with an equal number of random fixation trials. The results suggest that potentiated fixation circuitry interacts with pursuit circuitry at a subconscious level to inhibit pursuit.SIGNIFICANCE STATEMENT When an object moves, we view it with smooth pursuit eye movements. When an object is stationary, we view it with fixational eye movements. Pursuit and fixation are historically regarded as controlled by different neural circuitry, and alternating between invoking them is thought to be guided by a conscious decision. However, our results show that pursuit is actively suppressed by prior fixation of a stationary object. This suppression is involuntary, and cannot be avoided even if observers are certain that the object will move. The results suggest that the neural fixation circuitry is potentiated by engaging stationary objects, and interacts with pursuit outside of conscious awareness. |
Nicolas Wattiez; Charlotte Constans; Thomas Deffieux; Pierre M. Daye; Mickael Tanter; Jean-François Aubry; Pierre Pouget Transcranial ultrasonic stimulation modulates single-neuron discharge in macaques performing an antisaccade task Journal Article In: Brain Stimulation, vol. 10, no. 6, pp. 1024–1031, 2017. @article{Wattiez2017, Background Low intensity transcranial ultrasonic stimulation (TUS) has been demonstrated to non-invasively and transiently stimulate the nervous system. Although US neuromodulation has appeared robust in rodent studies, the effects of US in large mammals and humans have been modest at best. In addition, there is a lack of direct recordings from the stimulated neurons in response to US. Our study investigates the magnitude of the US effects on neuronal discharge in awake behaving monkeys and thus fills the void on both fronts. Objective/Hypothesis In this study, we demonstrate the feasibility of recording action potentials in the supplementary eye field (SEF) as TUS is applied simultaneously to the frontal eye field (FEF) in macaques performing an antisaccade task. Results We show that compared to a control stimulation in the visual cortex, SEF activity is significantly modulated shortly after TUS onset. Among all cell types 40% of neurons significantly changed their activity after TUS. Half of the neurons showed a transient increase of activity induced by TUS. Conclusion Our study demonstrates that the neuromodulatory effects of non-invasive focused ultrasound can be assessed in real time in awake behaving monkeys by recording discharge activity from a brain region reciprocally connected with the stimulated region. The study opens the door for further parametric studies for fine-tuning the ultrasonic parameters. The ultrasonic effect could indeed be quantified based on the direct measurement of the intensity of the modulation induced on a single neuron in a freely performing animal. The technique should be readily reproducible in other primate laboratories studying brain function, both for exploratory and therapeutic purposes and to facilitate the development of future clinical TUS devices. |
Tuesday M. Watts; Luke Holmes; Ritch C. Savin-Williams; Gerulf Rieger Pupil dilation to explicit and non-explicit sexual stimuli Journal Article In: Archives of Sexual Behavior, vol. 46, no. 1, pp. 155–165, 2017. @article{Watts2017, In the visual processing of sexual content, pupil dilation is an indicator of arousal that has been linked to observers' sexual orientation. This study investigated whether this measure can be extended to determine age-specific sexual interest. In two experiments, the pupillary responses of heterosexual adults to images of males and females of different ages were related to self-reported sexual interest, sexual appeal to the stimuli, and a child molestation proclivity scale. In both experiments, the pupils of male observers dilated to photographs of women but not men, children, or neutral stimuli. These pupillary responses corresponded with observer's self-reported sexual interests and their sexual appeal ratings of the stimuli. Female observers showed pupil dilation to photographs of men and women but not children. In women, pupillary responses also correlated poorly with sexual appeal ratings of the stimuli. These experiments provide initial evidence that eye-tracking could be used as a measure of sex-specific interest in male observers, and as an age-specific index in male and female observers |
Matthew David Weaver; Clayton Hickey; Wieske Zoest The impact of salience and visual working memory on the monitoring and control of saccadic behavior: An eye-tracking and EEG study Journal Article In: Psychophysiology, vol. 54, no. 4, pp. 544–554, 2017. @article{Weaver2017, In a concurrent eye-tracking and EEG study, we investigated the impact of salience on the monitoring and control of eye movement behavior and the role of visual working memory (VWM) capacity in mediating this effect. Participants made eye movements to a unique line-segment target embedded in a search display also containing a unique distractor. Target and distractor salience was manipulated by varying degree of orientation offset from a homogenous background. VWM capacity was measured using a change-detection task. Results showed greater likelihood of incorrect saccades when the distractor was relatively more salient than when the target was salient. Misdirected saccades to salient distractors were strongly represented in the error-monitoring system by rapid and robust errorrelated negativity (ERN), which predicted a significant adjustment of oculomotor behavior. Misdirected saccades to less-salient distractors, while arguably representing larger errors, were not as well detected or utilized by the error/ performance-monitoring system. This system was instead better engaged in tasks requiring greater cognitive control and by individuals with higher VWM capacity. Our findings show that relative salience of task-relevant and taskirrelevant stimuli can define situations where an increase in cognitive control is necessary, with individual differences in VWM capacity explaining significant variance in the degree of monitoring and control of goal-directed eye movement behavior. The present study supports a conflict-monitoring interpretation of the ERN, whereby the level of competition between different responses, and the stimuli that define these responses, was more important in the generation of an enhanced ERN than the error commission itself. |
Matthew David Weaver; Wieske Zoest; Clayton Hickey A temporal dependency account of attentional inhibition in oculomotor control Journal Article In: NeuroImage, vol. 147, pp. 880–894, 2017. @article{Weaver2017a, We used concurrent electroencephalogram (EEG) and eye tracking to investigate the role of covert attentional mechanisms in the control of oculomotor behavior. Human participants made speeded saccades to targets that were presented alongside salient distractors. By subsequently sorting trials based on whether the distractor was strongly represented or suppressed by the visual system – as evident in the accuracy (Exp. 1) or quality of the saccade (Exp. 2) – we could characterize and contrast pre-saccadic neural activity as a function of whether oculomotor control was established. Results show that saccadic behavior is strongly linked to the operation of attentional mechanisms in visual cortex. In Experiment 1, accurate saccades were preceded by attentional selection of the target – indexed by a target-elicited N2pc component – and by attentional suppression of the distractor – indexed by early and late distractor-elicited distractor positivity (Pd) components. In Experiment 2, the strength of distractor suppression predicted the degree to which the path of slower saccades would deviate away from the distractor en route to the target. However, results also demonstrated clear dissociations of covert and overt selective control, with saccadic latency in particular showing no relationship to the latency of covert selective mechanisms. Eye movements could thus be initiated prior to the onset of attentional ERP components, resulting in stimulus-driven behaviour. Taken together, the results indicate that attentional mechanisms play a role in determining saccadic behavior, but that saccade timing is not contingent on the deployment of attention. This creates a temporal dependency, whereby attention fosters oculomotor control only when attentional mechanisms are given sufficient opportunity to impact stimuli representations before an eye movement is executed. |
Thomas Welton; Sarim Ather; Frank A. Proudlock; Irene Gottlob; Robert A. Dineen Altered whole-brain connectivity in albinism Journal Article In: Human Brain Mapping, vol. 38, no. 2, pp. 740–752, 2017. @article{Welton2017, Albinism is a group of congenital disorders of the melanin synthesis pathway. Multiple ocular, white matter and cortical abnormalities occur in albinism, including a greater decussation of nerve fibres at the optic chiasm, foveal hypoplasia and nystagmus. Despite this, visual perception is largely preserved. It was proposed that this may be attributable to reorganisation among cerebral networks, including an increased interhemispheric connectivity of the primary visual areas. A graph-theoretic model was applied to explore brain connectivity networks derived from resting-state functional and diffusion-tensor magnetic resonance imaging data in 23 people with albinism and 20 controls. They tested for group differences in connectivity between primary visual areas and in summary network organisation descriptors. Main findings were supplemented with analyses of control regions, brain volumes and white matter microstructure. Significant functional interhemispheric hyperconnectivity of the primary visual areas in the albinism group were found (P = 0.012). Tests of interhemispheric connectivity based on the diffusion-tensor data showed no significant group difference (P = 0.713). Second, it was found that a range of functional whole-brain network metrics were abnormal in people with albinism, including the clustering coefficient (P = 0.005), although this may have been driven partly by overall differences in connectivity, rather than reorganisation. Based on the results, it was suggested that changes occur in albinism at the whole-brain level, and not just within the visual processing pathways. It was proposed that their findings may reflect compensatory adaptations to increased chiasmic decussation, foveal hypoplasia and nystagmus. |
Alex L. White; Erik Runeson; John Palmer; Zachary R. Ernst; Geoffrey M. Boynton Evidence for unlimited capacity processing of simple features in visual cortex Journal Article In: Journal of Vision, vol. 17, no. 6, pp. 19, 2017. @article{White2017a, Performance in many visual tasks is impaired when observers attempt to divide spatial attention across multiple visual field locations. Correspondingly, neuronal response magnitudes in visual cortex are often reduced during divided compared with focused spatial attention. This suggests that early visual cortex is the site of capacity limits, where finite processing resources must be divided among attended stimuli. However, behavioral research demonstrates that not all visual tasks suffer such capacity limits: The costs of divided attention are minimal when the task and stimulus are simple, such as when searching for a target defined by orientation or contrast. To date, however, every neuroimaging study of divided attention has used more complex tasks and found large reductions in response magnitude. We bridged that gap by using functional magnetic resonance imaging to measure responses in the human visual cortex during simple feature detection. The first experiment used a visual search task: Observers detected a low-contrast Gabor patch within one or four potentially relevant locations. The second experiment used a dual-task design, in which observers made independent judgments of Gabor presence in patches of dynamic noise at two locations. In both experiments, blood-oxygen level-dependent (BOLD) signals in the retinotopic cortex were significantly lower for ignored than attended stimuli. However, when observers divided attention between multiple stimuli, BOLD signals were not reliably reduced and behavioral performance was unimpaired. These results suggest that processing of simple features in early visual cortex has unlimited capacity. |
Brian J. White; David J. Berg; Janis Y. Y. Kan; Robert A. Marino; Laurent Itti; Douglas P. Munoz Superior colliculus neurons encode a visual saliency map during free viewing of natural dynamic video Journal Article In: Nature Communications, vol. 8, pp. 14263, 2017. @article{White2017b, Models of visual attention postulate the existence of a saliency map whose function is to guide attention and gaze to the most conspicuous regions in a visual scene. Although cortical representations of saliency have been reported, there is mounting evidence for a subcortical saliency mechanism, which pre-dates the evolution of neocortex. Here, we conduct a strong test of the saliency hypothesis by comparing the output of a well-established computational saliency model with the activation of neurons in the primate superior colliculus (SC), a midbrain structure associated with attention and gaze, while monkeys watched video of natural scenes. We find that the activity of SC superficial visual-layer neurons (SCs), specifically, is well-predicted by the model. This saliency representation is unlikely to be inherited from fronto-parietal cortices, which do not project to SCs, but may be computed in SCs and relayed to other areas via tectothalamic pathways. |
Brian J. White; Janis Y. Y. Kan; Ron Levy; Laurent Itti; Douglas P. Munoz Superior colliculus encodes visual saliency before the primary visual cortex Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 35, pp. 9451–9456, 2017. @article{White2017c, Models of visual attention postulate the existence of a bottom-up saliency map that is formed early in the visual processing stream. Although studies have reported evidence of a saliency map in various cortical brain areas, determining the contribution of phylogenetically older pathways is crucial to understanding its origin. Here, we compared saliency coding from neurons in two early gateways into the visual system: the primary visual cortex (V1) and the evolutionarily older superior colliculus (SC). We found that, while the response latency to visual stimulus onset was earlier for V1 neurons than superior colliculus superficial visual-layer neurons (SCs), the saliency representation emerged earlier in SCs than in V1. Because the dominant input to the SCs arises from V1, these relative timings are consistent with the hypothesis that SCs neurons pool the inputs from multiple V1 neurons to form a feature-agnostic saliency map, which may then be relayed to other brain areas. |
Sarah J. White; Laura M. T. Lantz; Kevin B. Paterson Spontaneous rereading within sentences: Eye movement control and visual sampling Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 43, no. 2, pp. 395–413, 2017. @article{White2017, Three experiments examine the role of previously read text in sentence comprehension and the control of eye movements during spontaneous rereading. Spontaneous rereading begins with a regressive saccade and involves reinspection of previously read text. All 3 experiments employed the gaze-contingent change technique to modulate the availability of previously read text. In Experiment 1, previously read text was permanently masked either immediately to the left of the fixated word (beyond wordn) or more than 1 word to the left (beyond wordn-1). The results of Experiment 1 indicate that the availability of the word immediately to the left (wordn-1) is important for comprehension. Experiments 2 and 3 further explored the role of previously read text beyond wordn-1. In these studies, text beyond wordn-1 was replaced, retaining only word length information, or word length and shape information. Following a regression back within a sentence, meaningful text either reappeared or remained unavailable during rereading. The experiments show that the visual format of text beyond wordn-1 (the parafoveal postview) is important for triggering regressions. The results also indicate that, as least for more complex sentences, the availability of meaningful text is important in driving eye movement control during rereading. |
Joel L. Voss; Neal J. Cohen Hippocampal-cortical contributions to strategic exploration during perceptual discrimination Journal Article In: Hippocampus, vol. 27, no. 6, pp. 642–652, 2017. @article{Voss2017, The hippocampus is crucial for long-term memory; its involvement in short-term or immediate expressions of memory is more controversial. Rodent hippocampus has been implicated in an expression of memory that occurs on-line during exploration termed “vicarious trial-and-error” (VTE) behavior. VTE occurs when rodents iteratively explore options during perceptual discrimination or at choice points. It is strategic in that it accelerates learning and improves later memory. VTE has been associated with activity of rodent hippocampal neurons, and lesions of hippocampus disrupt VTE and associated learning and memory advantages. Analogous findings of VTE in humans would support the role of hippocampus in active use of short-term memory to guide strategic behavior. We therefore measured VTE using eye-movement tracking during perceptual discrimination and identified relevant neural correlates with fMRI. A difficult perceptual-discrimination task was used that required visual information to be maintained during a several-second trial, but with no long-term memory component. VTE accelerated discrimination. Neural correlates of VTE included robust activity of hippocampus and activity of a network of medial prefrontal and lateral parietal regions involved in memory-guided behavior. This VTE-related activity was distinct from activity associated with simply viewing visual stimuli and making eye movements during the discrimination task, which occurred in regions frequently associated with visual processing and eye-movement control. Subjects were mostly unaware of performing VTE, thus further distancing VTE from explicit long-term memory processing. These findings bridge the rodent and human literatures on neural substrates of memory-guided behavior, and provide further support for the role of hippocampus and a hippocampal-centered network of cortical regions in the immediate use of memory in on-line processing and the guidance of behavior. |
Cécile Vullings; Laurent Madelain Control of saccadic latency in a dynamic environment: Allocation of saccades in time follows the matching law Journal Article In: Journal of Neurophysiology, no. 2016, pp. jn.00634.2017, 2017. @article{Vullings2017, Saccades may be regarded as an information-foraging behavior mostly concerned with the spatial localization of objects, yet our world is dynamic and environmental temporal regularities should also affect saccade decisions. We present behavioral data from a choice task establishing that humans can learn to choose their saccadic latencies depending on the reinforcement contingencies. This suggests a cost-benefit-based policy that takes into account the learned temporal properties of the environmental contingencies for controlling saccade triggering. |
Basil Wahn; Supriya Murali; Scott Sinnett; Peter König Auditory stimulus detection partially depends on visuospatial attentional resources Journal Article In: i-Perception, vol. 8, no. 1, 2017. @article{Wahn2017, Humans' ability to detect relevant sensory information while being engaged in a demanding task is crucial in daily life. Yet, limited attentional resources restrict information processing. To date, it is still debated whether there are distinct pools of attentional resources for each sensory modality and to what extent the process of multisensory integration is dependent on attentional resources. We addressed these two questions using a dual task paradigm. Specifically, participants performed a multiple object tracking task and a detection task either separately or simultaneously. In the detection task, participants were required to detect visual, auditory, or audiovisual stimuli at varying stimulus intensities that were adjusted using a staircase procedure. We found that tasks significantly interfered. However, the interference was about 50% lower when tasks were performed in separate sensory modalities than in the same sensory modality, suggesting that attentional resources are partly shared. Moreover, we found that perceptual sensitivities were significantly improved for audiovisual stimuli relative to unisensory stimuli regardless of whether attentional resources were diverted to the multiple object tracking task or not. Overall, the present study supports the view that attentional resource allocation in multisensory processing is task-dependent and suggests that multisensory benefits are not dependent on attentional resources. |
Gabriel Wainstein; D. Rojas-Líbano; N. A. Crossley; X. Carrasco; F. Aboitiz; Tomás Ossandón Pupil size tracks attentional performance in attention-deficit/hyperactivity disorder Journal Article In: Scientific Reports, vol. 7, pp. 8228, 2017. @article{Wainstein2017, Attention-deficit/hyperactivity disorder (ADHD) diagnosis is based on reported symptoms, which carries the potential risk of over- or under-diagnosis. A biological marker that helps to objectively define the disorder, providing information about its pathophysiology, is needed. A promising marker of cognitive states in humans is pupil size, which reflects the activity of an ‘arousal' network, related to the norepinephrine system. We monitored pupil size from ADHD and control subjects, during a visuo-spatial working memory task. A sub group of ADHD children performed the task twice, with and without methylphenidate, a norepinephrine–dopamine reuptake inhibitor. Off-medication patients showed a decreased pupil diameter during the task. This difference was no longer present when patients were on-medication. Pupil size correlated with the subjects' performance and reaction time variability, two vastly studied indicators of attention. Furthermore, this effect was modulated by medication. Through pupil size, we provide evidence of an involvement of the noradrenergic system during an attentional task. Our results suggest that pupil size could serve as a biomarker in ADHD. |
Sonja Walcher; Christof Körner; Mathias Benedek Looking for ideas: Eye behavior during goal-directed internally focused cognition Journal Article In: Consciousness and Cognition, vol. 53, no. March, pp. 165–175, 2017. @article{Walcher2017, Humans have a highly developed visual system, yet we spend a high proportion of our time awake ignoring the visual world and attending to our own thoughts. The present study examined eye movement characteristics of goal-directed internally focused cognition. Deliberate internally focused cognition was induced by an idea generation task. A letter-by-letter reading task served as external task. Idea generation (vs. reading) was associated with more and longer blinks and fewer microsaccades indicating an attenuation of visual input. Idea generation was further associated with more and shorter fixations, more saccades and saccades with higher amplitudes as well as heightened stimulus-independent variation of eye vergence. The latter results suggest a coupling of eye behavior to internally generated information and associated cognitive processes, i.e. searching for ideas. Our results support eye behavior patterns as indicators of goal-directed internally focused cognition through mechanisms of attenuation of visual input and coupling of eye behavior to internally generated information. |
Sonja Walcher; Christof Körner; Mathias Benedek Data on eye behavior during idea generation and letter-by-letter reading Journal Article In: Data in Brief, vol. 15, pp. 18–24, 2017. @article{Walcher2017a, This article includes the description of data information from an idea generation task (alternate uses task, (Guilford, 1967) [1]) and a letter-by-letter reading task under two background brightness conditions with healthy adults as well as a baseline measurement and questionnaire data (SIPI (Huba et al., 1981) [2]; DDFS (Singer and Antrobus, 1972) [3], 1963; RIBS (Runco et al., 2001) [4]). Data are hosted at the Open Science Framework (OSF): https://osf.io/fh66g/ (Walcher et al., 2017) [5]. There you will find eye tracking data, task performance data, questionnaires data, analyses scripts (in R, R Core Team, 2017 [6]), eye tracking paradigms (in the Experiment Builder (SR Research Ltd., [7]) and graphs on pupil and angle of eye vergence dynamics. Data are interpreted and discussed in the article ‘Looking for ideas: Eye behavior during goal-directed internally focused cognition' (Walcher et al., 2017) [8]. |
Julian M. Wallace; Susana T. L. Chung; Bosco S. Tjan Object crowding in age-related macular degeneration Journal Article In: Journal of Vision, vol. 17, no. 1, pp. 33, 2017. @article{Wallace2017, Crowding, the phenomenon of impeded object identification due to clutter, is believed to be a key limiting factor of form vision in the peripheral visual field. The present study provides a characterization of object crowding in age-related macular degeneration (AMD) measured at the participants' respective preferred retinal loci with binocular viewing. Crowding was also measured in young and age-matched controls at the same retinal locations, using a fixation-contingent display paradigm to allow unlimited stimulus duration. With objects, the critical spacing of crowding for AMD participants was not substantially different from controls. However, baseline contrast energy thresholds in the noncrowded condition were four times that of the controls. Crowding further exacerbated deficits in contrast sensitivity to three times the normal crowding-induced contrast energy threshold elevation. These findings indicate that contrast-sensitivity deficit is a major limiting factor of object recognition for individuals with AMD, in addition to crowding. Focusing on this more tractable deficit of AMD may lead to more effective remediation and technological assistance. |
Chin-An Wang; Gunnar Blohm; Jeff Huang; Susan E. Boehnke; Douglas P. Munoz Multisensory integration in orienting behavior: Pupil size, microsaccades, and saccades Journal Article In: Biological Psychology, vol. 129, no. December 2016, pp. 36–44, 2017. @article{Wang2017a, Signals from different sensory modalities are integrated in the brain to optimize behavior. Although multisensory integration has been demonstrated in saccadic eye movements, its influence on other orienting responses, including pupil size and microsaccades, is still poorly understood. We examined human gaze orienting responses following presentation of visual, auditory, or combined audiovisual stimuli. Transient pupil dilation and microsaccade inhibition were evoked shortly after the appearance of a salient stimulus. Audiovisual stimuli evoked larger pupil dilation, greater microsaccade inhibition, and faster saccade reaction times compared to unimodal conditions. Trials with faster saccadic reaction times were accompanied with greater pupil dilation responses. Similar modulation of pre-stimulus pupil-size-change rate was observed between stimulus-evoked saccadic and pupillary responses. Thus, multisensory integration impacts multiple components of orienting, with coordination between saccade and pupil responses, implicating the superior colliculus in coordinating these responses because of its central role in both orienting behavior and multisensory integration. |
Yuliy Tsank; Miguel P. Eckstein Domain specificity of oculomotor learning after changes in sensory processing Journal Article In: Journal of Neuroscience, vol. 37, no. 47, pp. 11469 –11484, 2017. @article{Tsank2017, Humans visually process the world with varying spatial resolution and can program their eye movements optimally to maximize information acquisition for a variety of everyday tasks. Diseases such as macular degeneration can change visual sensory processing, introducing central vision loss (a scotoma). However, humans can learn to direct a new preferred retinal location to regions of interest for simple visual tasks. Whether such learned compensatory saccades are optimal and generalize to more complex tasks, which require integrating information across a large area of the visual field, is not well-understood. Here, we explore the possible effects of central vision loss on the optimal saccades during a face identification task, using a gaze-contingent simulated scotoma. We show that a new foveated ideal observer with a central scotoma correctly predicts that the human optimal point of fixation to identify faces shifts from just below the eyes to one that is at the tip of the nose and another at the top of the forehead. However, even after 5,000 trials, humans of both sexes surprisingly do not change their initial fixations to adapt to the new optimal fixation points to faces. In contrast, saccades do change for tasks such as object-following and to a lesser extent during search. Our findings argue against a central brain motor-compensatory mechanism that generalizes across tasks. They instead suggest task-specificity in the learning of oculomotor plans in response to changes in front-end sensory processing and the possibility of separate domain-specific representations of learned oculomotor plans in the brain. |
Luke Tudge; Eugene McSorley; Stephan A. Brandt; Torsten Schubert Setting things straight: A comparison of measures of saccade trajectory deviation Journal Article In: Behavior Research Methods, vol. 49, no. 6, pp. 2127–2145, 2017. @article{Tudge2017, In eye movements, saccade trajectory deviation has often been used as a physiological operationalization of visual attention, distraction, or the visual system's prioritization of different sources of information. However, there are many ways to measure saccade trajectories and to quantify their deviation. This may lead to noncomparable results and poses the problem of choosing a method that will maximize statistical power. Using data from existing studies and from our own experiments, we used principal components analysis to carry out a systematic quantification of the relationships among eight different measures of saccade trajectory deviation and their power to detect the effects of experimental manipulations, as measured by standardized effect size. We concluded that (1) the saccade deviation measure is a good default measure of saccade trajectory deviation, because it is somewhat correlated with all other measures and shows relatively high effect sizes for two well-known experimental effects; (2) more generally, measures made relative to the position of the saccade target are more powerful; and (3) measures of deviation based on the early part of the saccade are made more stable when they are based on data from an eyetracker with a high sampling rate. Our recommendations may be of use to future eye movement researchers seeking to optimize the designs of their studies. |
Philip R. K. Turnbull; Nouzar Irani; Nicky Lim; John R. Phillips Origins of pupillary hippus in the autonomic nervous system Journal Article In: Investigative Ophthalmology & Visual Science, vol. 58, no. 1, pp. 197–203, 2017. @article{Turnbull2017, PURPOSE. The purpose of this study was to determine the relative roles of the sympathetic (SNS) and parasympathetic nervous system (PNS) in pupillary hippus. METHODS. We used a paired-eye control study design with three cohorts receiving either 1.0% tropicamide (PNS antagonist) in light (TL), 1.0% tropicamide in dark (TD), or 10% phenylephrine (SNS) in light (PL) |
Philip R. K. Turnbull; John R. Phillips Ocular effects of virtual reality headset wear in young adults Journal Article In: Scientific Reports, vol. 7, pp. 16172, 2017. @article{Turnbull2017a, Virtual Reality (VR) headsets create immersion by displaying images on screens placed very close to the eyes, which are viewed through high powered lenses. Here we investigate whether this viewing arrangement alters the binocular status of the eyes, and whether it is likely to provide a stimulus for myopia development. We compared binocular status after 40-minute trials in indoor and outdoor environments, in both real and virtual worlds. We also measured the change in thickness of the ocular choroid, to assess the likely presence of signals for ocular growth and myopia development. We found that changes in binocular posture at distance and near, gaze stability, amplitude of accommodation and stereopsis were not different after exposure to each of the 4 environments. Thus, we found no evidence that the VR optical arrangement had an adverse effect on the binocular status of the eyes in the short term. Choroidal thickness did not change after either real world trial, but there was a significant thickening (≈10 microns) after each VR trial (p < 0.001). The choroidal thickening which we observed suggest that a VR headset may not be a myopiagenic stimulus, despite the very close viewing distances involved. |
Travis H. Turner; Jenna B. Renfroe; Amy Duppstadt-Delambo; Vanessa K. Hinson Validation of a behavioral approach for measuring saccades in Parkinson's disease Journal Article In: Journal of Motor Behavior, vol. 49, no. 6, pp. 657–667, 2017. @article{Turner2017, Speed and control of saccades are related to disease progression and cognitive functioning in Parkinson's disease (PD). Traditional eye-tracking complexities encumber application for individual evaluations and clinical trials. The authors examined psychometric properties of standalone tasks for reflexive prosaccade latency, volitional saccade initiation, and saccade inhibition (antisaccade) in a heterogeneous sample of 65 PD patients. Demographics had minimal impact on task performance. Thirty-day test-retest reliability estimates for behavioral tasks were acceptable and similar to traditional eye tracking. Behavioral tasks demonstrated concurrent validity with traditional eye-tracking measures; discriminant validity was less clear. Saccade initiation and inhibition discriminated PD patients with cognitive impairment. The present findings support further development and use of the behavioral tasks for assessing latency and control of saccades in PD. |
Courtney Turrin; Nicholas A. Fagan; Olga Dal Monte; Steve W. C. Chang Social resource foraging is guided by the principles of the Marginal Value Theorem Journal Article In: Scientific Reports, vol. 7, pp. 11274, 2017. @article{Turrin2017, Optimality principles guide how animals adapt to changing environments. During foraging for nonsocial resources such as food and water, species across taxa obey a strategy that maximizes resource harvest rate. However, it remains unknown whether foraging for social resources also obeys such a strategic principle. We investigated how primates forage for social information conveyed by conspecific facial expressions using the framework of optimal foraging theory. We found that the canonical principle of Marginal Value Theorem (MVT) also applies to social resources. Consistent with MVT, rhesus macaques (Macaca mulatta) spent more time foraging for social information when alternative sources of information were farther away compared to when they were closer by. A comparison of four models of patch-leaving behavior confirmed that the MVT framework provided the best fit to the observed foraging behavior. This analysis further demonstrated that patch-leaving decisions were not driven simply by the declining value of the images in the patch, but instead were dependent upon both the instantaneous social value intake rate and current time in the patch. |
Damon Tutunjian; Fredrik Heinat; Eva Klingvall; Anna-Lena Wiklund Processing relative clause extractions in Swedish Journal Article In: Frontiers in Psychology, vol. 8, pp. 2118, 2017. @article{Tutunjian2017, Relative clauses are considered strong islands for extraction across languages. Swedish comprises a well-known exception, allegedly allowing extraction from relative clauses (RCE), raising the possibility that island constraints may be subject to "deep variation" between languages. One alternative is that such exceptions are only illusory and represent "surface variation" attributable to independently motivated syntactic properties. Yet, to date, no surface account has proven tenable for Swedish RCEs. The present study uses eyetracking while reading to test whether the apparent acceptability of Swedish RCEs has any processing correlates at the point of filler integration compared to uncontroversial strong island violations. Experiment 1 tests RCE against licit that-clause extraction (TCE), illicit extraction from a non-restrictive RC island (NRCE), and an intransitive control. For this, RCE was found to pattern similarly to TCE at the point of integration in early measures, but between TCE and NRCE in total durations. Experiment 2 uses RCE and extraction from a subject NP island (SRCE) to test the hypothesis that only non-islands will show effects of implausible filler-verb dependencies. RCE showed sensitivity to the plausibility manipulation across measures at the first potential point of filler integration, whereas such effects were limited to late measures for SRCE. In addition, structural facilitation was seen across measures for RCE relative to SRCE. We propose that our results are compatible with RCEs being licit weak island extractions in Swedish, and that the overall picture speaks in favor of a surface rather than a deep variation approach to the lack of island effects in Swedish RCEs. |
Yoshiyuki Ueda; Yusuke Kamakura; Jun Saiki Eye movements converge on vanishing points during visual search Journal Article In: Japanese Psychological Research, vol. 59, no. 2, pp. 109–121, 2017. @article{Ueda2017, The vanishing point seems to be a useful cue for understanding scenes at a glance. The closer the objects are, the smaller their sizes become. Because the resolution of central vision is higher than that of peripheral vision, seeing a vanishing point enables individuals to perceive the whole scene. Here, we examined whether vanishing points attract eye movements during visual search. In Experiment 1, we conducted a free‐viewing task to examine whether vanishing points play a significant role. In Experiment 2, the participants searched for a Gabor patch that was embedded in manmade or natural scenes. In Experiment 3, to investigate the robustness of the vanishing point effect, visual search was conducted using simpler geometric backgrounds. We observed that eye movements converged around vanishing points, and that the first fixations are also located around them. These results suggest that vanishing points as well as salient locations can capture eye movements, and eye movements are guided by such environmental structures. |
Anne E. Urai; Anke Braun; Tobias H. Donner Pupil-linked arousal is driven by decision uncertainty and alters serial choice bias Journal Article In: Nature Communications, vol. 8, pp. 14637, 2017. @article{Urai2017, While judging their sensory environments, decision-makers seem to use the uncertainty about their choices to guide adjustments of their subsequent behaviour. One possible source of these behavioural adjustments is arousal: decision uncertainty might drive the brain's arousal systems, which control global brain state and might thereby shape subsequent decision-making. Here, we measure pupil diameter, a proxy for central arousal state, in human observers performing a perceptual choice task of varying difficulty. Pupil dilation, after choice but before external feedback, reflects three hallmark signatures of decision uncertainty derived from a computational model. This increase in pupil-linked arousal boosts observers' tendency to alternate their choice on the subsequent trial. We conclude that decision uncertainty drives rapid changes in pupil-linked arousal state, which shape the serial correlation structure of ongoing choice behaviour. |
Israel Vaca-Palomares; Brian C. Coe; Donald C. Brien; Douglas P. Munoz; Juan Fernandez-Ruiz Voluntary saccade inhibition deficits correlate with extended white-matter cortico-basal atrophy in Huntington's disease Journal Article In: NeuroImage: Clinical, vol. 15, pp. 502–512, 2017. @article{VacaPalomares2017, The ability to inhibit automatic versus voluntary saccade commands in demanding situations can be impaired in neurodegenerative diseases such as Huntington's disease (HD). These deficits could result from disruptions in the interaction between basal ganglia and the saccade control system. To investigate voluntary oculomotor control deficits related to the cortico-basal circuitry, we evaluated early HD patients using an interleaved pro- and anti-saccade task that requires flexible executive control to generate either an automatic response (look at a peripheral visual stimulus) or a voluntary response (look away from the stimulus in the opposite direction). The impairments of HD patients in this task are mainly attributed to degeneration in the striatal medium spiny neurons leading to an over-activation of the indirect-pathway thorough the basal ganglia. However, some studies have proposed that damage outside the indirect-pathway also contribute to executive and saccade deficits. We used the interleaved pro- and anti-saccade task to study voluntary saccade inhibition deficits, Voxel-based morphometry and Tract-based spatial statistic to map cortico-basal ganglia circuitry atrophy in HD. HD patients had voluntary saccade inhibition control deficits, including increased regular-latency anti-saccade errors and increased anticipatory saccades. These deficits correlated with white-matter atrophy in the inferior fronto-occipital fasciculus, anterior thalamic radiation, anterior corona radiata and superior longitudinal fasciculus. These findings suggest that cortico-basal ganglia white-matter atrophy in HD, disrupts the normal connectivity in a network controlling voluntary saccade inhibitory behavior beyond the indirect-pathway. This suggests that in vivo measures of white-matter atrophy can be a reliable marker of the progression of cognitive deficits in HD. |
Jorge R. Valdés Kroff; Paola E. Dussias; Chip Gerfen; Lauren Perrotti; María Teresa Bajo Experience with code-switching modulates the use of grammatical gender during sentence processing Journal Article In: Linguistic Approaches to Bilingualism, vol. 7, no. 2, pp. 163–198, 2017. @article{ValdesKroff2017, Using code-switching as a tool to illustrate how language experience modulates comprehension, the visual world paradigm was employed to examine the extent to which gender-marked Spanish determiners facilitate upcoming target nouns in a group of Spanish-English bilingual code-switchers. The first experiment tested target Spanish nouns embedded in a carrier phrase (Experiment 1b) and included a control Spanish monolingual group (Experiment 1a). The second set of experiments included critical trials in which participants heard code-switches from Spanish determiners into English nouns (e.g., la house) either in a fixed carrier phrase (Experiment 2a) or in variable and complex sentences (Experiment 2b). Across the experiments, bilinguals revealed an asymmetric gender effect in processing, showing facilitation only for feminine target items. These results reflect the asymmetric use of gender in the production of code-switched speech. The extension of the asymmetric effect into Spanish (Experiment 1b) underscores the permeability between language modes in bilingual code-switchers. |
Christian Valuch; Peter König; Ulrich Ansorge Memory-guided attention during active viewing of edited dynamic scenes Journal Article In: Journal of Vision, vol. 17, no. 1, pp. 12, 2017. @article{Valuch2017, TV shows, and other edited dynamic scenes contain many cuts, which are abrupt transitions from one video shot to the next. Cuts occur within or between scenes, and often join together visually and semantically related shots. Here, we tested to which degree memory for the visual features of the precut shot facilitates shifting attention to the postcut shot. We manipulated visual similarity across cuts, and measured how this affected covert attention (Experiment 1) and overt attention (Experiments 2 and 3). In Experiments 1 and 2, participants actively viewed a target movie that randomly switched locations with a second, distractor movie at the time of the cuts. In Experiments 1 and 2, participants were able to deploy attention more rapidly and accurately to the target movie's continuation when visual similarity was high than when it was low. Experiment 3 tested whether this could be explained by stimulus-driven (bottom-up) priming by feature similarity, using one clip at screen center that was followed by two alternative continuations to the left and right. Here, even the highest similarity across cuts did not capture attention. We conclude that following cuts of high visual similarity, memory-guided attention facilitates the deployment of attention, but this effect is (top-down) dependent on the viewer's active matching of scene content across cuts. |
Marjolein Waal; Jason Farquhar; Luciano Fasotti; Peter Desain Preserved and attenuated electrophysiological correlates of visual spatial attention in elderly subjects Journal Article In: Behavioural Brain Research, vol. 317, pp. 415–423, 2017. @article{Waal2017, Healthy aging is associated with changes in many neurocognitive functions. While on the behavioral level, visual spatial attention capacities are relatively stable with increasing age, the underlying neural processes change. In this study, we investigated attention-related modulations of the stimulus-locked event-related potential (ERP) and occipital oscillations in the alpha band (8–14 Hz) in young and elderly participants. Both groups performed a visual attention task equally well and the ERP showed comparable attention-related modulations in both age groups. However, in elderly subjects, oscillations in the alpha band were massively reduced both during the task and in the resting state and the typical task-related lateralized pattern of alpha activity was not observed. These differences between young and elderly participants were observed on the group level as well as on the single trial level. The results indicate that younger and older adults use different neural strategies to reach the same performance in a covert visual spatial attention task. |
Freek Ede; Marcel Niklaus; Anna C. Nobre Temporal expectations guide dynamic prioritization in visual working memory through attenuated α oscillations Journal Article In: Journal of Neuroscience, vol. 37, no. 2, pp. 437–445, 2017. @article{Ede2017, Although working memory is generally considered a highly dynamic mnemonic store, popular laboratory tasks used to understand its psychological and neural mechanisms (such as change detection and continuous reproduction) often remain relatively " static, " involving the retention of a set number of items throughout a shared delay interval. In the current study, we investigated visual working memory in a more dynamic setting, and assessed the following: (1) whether internally guided temporal expectations can dynamically and reversibly prioritize individual mnemonic items at specific times at which they are deemed most relevant; and (2) the neural substrates that support such dynamic prioritization. Participants encoded two differently colored oriented bars into visual working memory to retrieve the orientation of one bar with a precision judgment when subsequently probed. To test for the flexible temporal control to access and retrieve remembered items, we manipulated the probability for each of the two bars to be probed over time, and recorded EEG in healthy human volunteers. Temporal expectations had a profound influence on working memory performance, leading to faster access times as well as more accurate orientation reproductions for items that were probed at expected times. Furthermore, this dynamic prioritization was associated with the temporally specific attenuation of contralateral ␣ (8 –14 Hz) oscillations that, moreover, predicted working memory access times on a trial-by-trial basis. We conclude that attentional prioritization in working memory can be dynamically steered by internally guided temporal expectations, and is supported by the attenuation of ␣ oscillations in task-relevant sensory brain areas. |
Anouk Mariette Loon; Katya Olmos-Solis; Christian N. L. Olivers Subtle eye movement metrics reveal task-relevant representations prior to visual search Journal Article In: Journal of Vision, vol. 17, no. 6, pp. 13, 2017. @article{Loon2017, Visual search is thought to be guided by an active visual working memory (VWM) representation of the task-relevant features, referred to as the search template. In three experiments using a probe technique, we investigated which eye movement metrics reveal which search template is activated prior to the search, and distinguish it from future relevant or no longer relevant VWM content. Participants memorized a target color for a subsequent search task, while being instructed to keep central fixation. Before the search display appeared, we briefly presented two task-irrelevant colored probe stimuli to the left and right from fixation, one of which could match the current target template. In all three experiments, participants made both more and larger eye movements towards the probe matching the target color. The bias was predominantly expressed in microsaccades, 100-250 ms after probe onset. Experiment 2 used a retro-cue technique to show that these metrics distinguish between relevant and dropped representations. Finally, Experiment 3 used a sequential task paradigm, and showed that the same metrics also distinguish between current and prospective search templates. Taken together, we show how subtle eye movements track task-relevant representations for selective attention prior to visual search. |
Joanne C. Van Slooten; Sara Jahfari; Tomas Knapen; Jan Theeuwes Individual differences in eye blink rate predict both transient and tonic pupil responses during reversal learning Journal Article In: PLoS ONE, vol. 12, no. 9, pp. e0185665, 2017. @article{VanSlooten2017, The pupil response under constant illumination can be used as a marker of cognitive processes. In the past, pupillary responses have been studied in the context of arousal and decision-making. However, recent work involving Parkinson's patients suggested that pupillary responses are additionally affected by reward sensitivity. Here, we build on these findings by examining how pupil responses are modulated by reward and loss while participants (N = 30) performed a Pavlovian reversal learning task. In fast (transient) pupil responses, we observed arousal-based influences on pupil size both during the expectation of upcoming value and the evaluation of unexpected monetary outcomes. Importantly, after incorporating eye blink rate (EBR), a behavioral correlate of striatal dopamine levels, we observed that participants with lower EBR showed stronger pupil dilation during the expectation of upcoming reward. Subsequently, when reward expectations were violated, participants with lower EBR showed stronger pupil responses after experiencing unexpected loss. Across trials, the detection of a reward contingency reversal was reflected in a slow (tonic) dilatory pupil response observed already several trials prior to the behavioral report. Interestingly, EBR correlated positively with this tonic detection response, suggesting that variability in the arousal-based detection response may reflect individual differences in striatal dopaminergic tone. Our results provide evidence that a behavioral marker of baseline striatal dopamine level (EBR) can potentially be used to describe the differential effects of value-based learning in the arousal-based pupil response. |
Wieske Zoest; Benedetta Heimler; Francesco Pavani The oculomotor salience of flicker, apparent motion and continuous motion in saccade trajectories Journal Article In: Experimental Brain Research, vol. 235, pp. 181–191, 2017. @article{Zoest2017, The aim of the present study was to investigate the impact of dynamic distractors on the time-course of oculomotor selection using saccade trajectory deviations. Participants were instructed to make a speeded eye move- ment (pro-saccade) to a target presented above or below the fixation point while an irrelevant distractor was presented. Four types of distractors were varied within participants: (1) static, (2) flicker, (3) rotating apparent motion and (4) continuous motion. The eccentricity of the distractor was varied between participants. The results showed that sac- cadic trajectories curved towards distractors presented near the vertical midline; no reliable deviation was found for distractors presented further away from the vertical mid- line. Differences between the flickering and rotating dis- tractor were found when distractor eccentricity was small and these specific effects developed over time such that there was a clear differentiation between saccadic deviation based on apparent motion for long-latency saccades, but not short-latency saccades. The present results suggest that the influence on performance of apparent motion stimuli is relatively delayed and acts in a more sustained manner compared to the influence of salient static, flickering and continuous moving stimuli. |
Veronica Whitford; Debra Titone The effects of word frequency and word predictability during first- and second-language paragraph reading in bilingual older and younger adults Journal Article In: Psychology and Aging, vol. 32, no. 2, pp. 158–177, 2017. @article{Whitford2017, We used eye movement measures of paragraph reading; varying in amount of current L2 experience. Our ke; across both early- and late-stage reading; word frequency effects were generally larger in ol; whereas word predictability effects were generally; across both age groups and both reading stages; word frequency effects were larger in the L2 than ; whereas word predictability effects were language-; graded differences in current L2 experience modula; but had no impact in older adults. Specifically; greater current L2 experience facilitated L2 word ; but impeded L1 word processing among younger adult; we draw 2 main conclusions. First; bilingual older adults experience changes in word-; potentially because lexical accessibility decrease; bilingual older adults experience changes in word-; potentially because lexical representations reach a functional ceiling over time. |
Theresa Wildegger; Freek Ede; Mark W. Woolrich; Céline R. Gillebert; Anna C. Nobre Preparatory α-band oscillations reflect spatial gating independently of predictions regarding target identity Journal Article In: Journal of Neurophysiology, vol. 117, no. 3, pp. 1385–1394, 2017. @article{Wildegger2017, Preparatory modulations of cortical alpha-band oscillations are a reliable index of the voluntary allocation of covert spatial attention. It is currently unclear whether attentional cues containing information about a target's identity (such as its visual orientation), in addition to its location, might additionally shape preparatory alpha modulations. Here, we explore this question by directly comparing spatial and feature-based attention in the same visual detection task while recording brain activity using magneto-encephalography (MEG). At the behavioural level, preparatory feature-based and spatial attention cues both improved performance, and did so independently of each other. Using MEG, we replicated robust alpha lateralisation following spatial cues: in preparation for a visual target, alpha power decreased contralaterally, and increased ipsilaterally to the attended location. Critically, however, preparatory alpha lateralisation was not significantly modulated by predictions regarding target identity, as carried via the behaviourally effective feature-based attention cues. Furthermore, non-lateralised alpha power during the cue-target interval did not differentiate between uninformative cues and cues carrying feature-based predictions either. Based on these results we propose that preparatory alpha modulations play a role in the gating of information between spatially segregated cortical regions, and are therefore particularly well suited for spatial gating of information. |
Lauren H. Williams; Trafton Drew Distraction in diagnostic radiology: How is search through volumetric medical images affected by interruptions? Journal Article In: Cognitive Research: Principles and Implications, vol. 2, no. 1, pp. 12, 2017. @article{Williams2017, Observational studies have shown that interruptions are a frequent occurrence in diagnostic radiology. The present study used an experimental design in order to quantify the cost of these interruptions during search through volumetric medical images. Participants searched through chest CT scans for nodules that are indicative of lung cancer. In half of the cases, search was interrupted by a series of true or false math equations. The primary cost of these interruptions was an increase in search time with no corresponding increase in accuracy or lung coverage. This time cost was not modulated by the difficulty of the interruption task or an individual's working memory capacity. Eye-tracking suggests that this time cost was driven by impaired memory for which regions of the lung were searched prior to the interruption. Potential interventions will be discussed in the context of these results. |
Niklas Wilming; Tim C. Kietzmann; Megan Jutras; Cheng Xue; Stefan Treue; Elizabeth A. Buffalo; Peter König Differential contribution of low- and high-level image content to eye movements in monkeys and humans Journal Article In: Cerebral Cortex, vol. 27, no. 1, pp. 279–293, 2017. @article{Wilming2017, Oculomotor selection exerts a fundamental impact on our experience of the environment. To better understand the underlying principles, researchers typically rely on behavioral data from humans, and electrophysiological recordings in macaque monkeys. This approach rests on the assumption that the same selection processes are at play in both species. To test this assumption, we compared the viewing behavior of 106 humans and 11 macaques in an unconstrained free-viewing task. Our data-driven clustering analyses revealed distinct human and macaque clusters, indicating species-specific selection strategies. Yet, cross-species predictions were found to be above chance, indicating some level of shared behavior. Analyses relying on computational models of visual saliency indicate that such cross-species commonalities in free viewing are largely due to similar low-level selection mechanisms, with only a small contribution by shared higher level selection mechanisms and with consistent viewing behavior of monkeys being a subset of the consistent viewing behavior of humans. |
Niklas Wilming; Selim Onat; José P. Ossandón; Alper Açik; Tim C. Kietzmann Data descriptor : An extensive dataset of eye movements during viewing of complex images Journal Article In: Scientific Data, vol. 4, pp. 160126, 2017. @article{Wilming2017a, We present a dataset of free-viewing eye-movement recordings that contains more than 2.7 million fixation locations from 949 observers on more than 1000 images from different categories. This dataset aggregates and harmonizes data from 23 different studies conducted at the Institute of Cognitive Science at Osnabrück University and the University Medical Center in Hamburg-Eppendorf. Trained personnel recorded all studies under standard conditions with homogeneous equipment and parameter settings. All studies allowed for free eye-movements, and differed in the age range of participants (~7–80 years), stimulus sizes, stimulus modifications (phase scrambled, spatial filtering, mirrored), and stimuli categories (natural and urban scenes, web sites, fractal, pink-noise, and ambiguous artistic figures). The size and variability of viewing behavior within this dataset presents a strong opportunity for evaluating and comparing computational models of overt attention, and furthermore, for thoroughly quantifying strategies of viewing behavior. This also makes the dataset a good starting point for investigating whether viewing strategies change in patient groups. |
Christian Wolf; Anna Heuer; Anna Schubö; Alexander C. Schütz The necessity to choose causes the effects of reward on saccade preparation Journal Article In: Scientific Reports, vol. 7, pp. 16966, 2017. @article{Wolf2017a, When humans have to choose between different options, they can maximize their payoff by choosing the option that yields the highest reward. Information about reward is not only used to optimize decisions but also for movement preparation to minimize reaction times to rewarded targets. Here, we show that this is especially true in contexts in which participants additionally have to choose between different options. We probed eye movement preparation by measuring saccade latencies to differently rewarded single targets (single-trial) appearing left or right from fixation. In choice-trials, both targets were displayed and participants were free to decide for one target to receive the corresponding reward. In blocks without choice-trials, single-trial latencies were not or only weakly affected by reward. With choice-trials present, the influence of reward increased with the proportion and difficulty of choices and decreased when a cue indicated that no choice will be necessary. Choices caused a delay in subsequent single-trial responses to the non-chosen option. Taken together, our results suggest that reward affects saccade preparation mainly when the outcome is uncertain and depends on the participants' behavior, for instance when they have to choose between targets differing in reward. |
Christian Wolf; Alexander C. Schütz Earlier saccades to task-relevant targets irrespective of relative gain between peripheral and foveal information Journal Article In: Journal of Vision, vol. 17, no. 6, pp. 21, 2017. @article{Wolf2017, © 2017 The Authors. Saccades bring objects of interest onto the fovea for high-acuity processing. Saccades to rewarded targets show shorter latencies that correlate negatively with expected motivational value. Shorter latencies are also observed when the saccade target is relevant for a perceptual discrimination task. Here we tested whether saccade preparation is equally influenced by informational value as it is by motivational value. We defined informational value as the probability that information is task-relevant times the ratio between postsaccadic foveal and presaccadic peripheral discriminability. Using a gaze-contingent display, we independently manipulated peripheral and foveal discriminability of the saccade target. Latencies of saccades with perceptual task were reduced by 36 ms in general, but they were not modulated by the information saccades provide (Experiments 1 and 2). However, latencies showed a clear negative linear correlation with the probability that the target is taskrelevant (Experiment 3). We replicated that the facilitation by a perceptual task is spatially specific and not due to generally heightened arousal (Experiment 4). Finally, the facilitation only emerged when the perceptual task is in the visual but not in the auditory modality (Experiment 5). Taken together, these results suggest that saccade latencies are not equally modulated by informational value as by motivational value. The facilitation by a perceptual task only arises when taskrelevant visual information is foveated, irrespective of whether the foveation is useful or not. |
Michael A. Eskenazi; Jocelyn R. Folk Regressions during reading: The cost depends on the cause Journal Article In: Psychonomic Bulletin & Review, vol. 24, no. 4, pp. 1211–1216, 2017. @article{Eskenazi2017, The direction and duration of eye movements during reading is predominantly determined by cognitive and linguistic processing, but some low-level oculomotor effects also influence the duration and direction of eye movements. One such effect is inhibition of return (IOR), which results in an increased latency to return attention to a target that has been previously attended (Posner & Cohen, Attention and Performance X: Control of Language Processes, 32, 531– 556, 1984). Although this is a low level effect, it has also been found in the complex task of reading (Henderson & Luke, Psychonomic Bulletin & Review, 19(6), 1101–1107, 2012; Rayner, Juhasz, Ashby, & Clifton, Vision Research, 43(9), 1027–1034, 2003). The purpose of the current study was to isolate the potentially different causes ofregressive eye movements: to adjust for oculomotor error and to assist with comprehension difficulties. We found that readers demonstrated an IOR effect when regressions were caused by oculomotor error, but not when regressions were caused by comprehension difficulties. The results suggest that IOR is primarily associated with low-level oculomotor control of eye movements, and that regressive eye movements that are controlled by comprehension processes are not subject to IOR effects. The results have implications for understanding the relationship between oculomotor and cognitive control ofeye movements and for models ofeye movement control. |
Alejandro J. Estudillo; Markus Bindemann Can gaze-contingent mirror-feedback from unfamiliar faces alter self-recognition? Journal Article In: Quarterly Journal of Experimental Psychology, vol. 70, no. 5, pp. 944–958, 2017. @article{Estudillo2017, This study focuses on learning of the self, by examining how human observers update internal representations of their own face. For this purpose, we present a novel gaze-contingent paradigm, in which an onscreen face either mimics observers' own eye-gaze behaviour (in the congruent condition), moves its eyes in different directions to that of the observers (incongruent condition), or remains static and unresponsive (neutral condition). Across three experiments, the mimicry of the onscreen face did not affect observers' perceptual self-representations. However, this paradigm influenced observers' reports of their own face. This effect was such that observers felt the onscreen face to be their own and that, if the onscreen gaze had moved on its own accord, observers expected their own eyes to move too. The theoretical implications of these findings are discussed. |
Ulrich Ettinger; Eliana Faiola; Anna-Maria Kasparbauer; Nadine Petrovsky; Raymond C. K. Chan; Roman Liepelt; Veena Kumari Effects of nicotine on response inhibition and interference control Journal Article In: Psychopharmacology, vol. 234, no. 7, pp. 1093–1111, 2017. @article{Ettinger2017, Nicotine is a cholinergic agonist with known pro-cognitive effects in the domains of alerting and orienting attention. However, its effects on attentional top-down functions such as response inhibition and interference control are less well characterised. Here, we investigated the effects of 7 mg transdermal nicotine on performance on a battery of response inhibition and interference control tasks. A sample of N = 44 healthy adult non-smokers performed antisaccade, stop signal, Stroop, go/no-go, flanker, shape matching and Simon tasks, as well as the attentional network test (ANT) and a continuous performance task (CPT). Nicotine was administered in a within-subjects, double-blind, placebo-controlled design, with order of drug administration counterbalanced. Relative to placebo, nicotine led to significantly shorter reaction times on a prosaccade task and on CPT hits but did not significantly improve inhibitory or interference control performance on any task. Instead, nicotine had a negative influence in increasing the interference effect on the Simon task. Nicotine did not alter inter-individual associations between reaction times on congruent trials and error rates on incongruent trials on any task. Finally, there were effects involving order of drug administration, suggesting practice effects but also beneficial nicotine effects when the compound was administered first. Overall, our findings support previous studies showing positive effects of nicotine on basic attentional functions but do not provide direct evidence for an improvement of top-down cognitive control through acute administration of nicotine at this dose in healthy non-smokers. |
Jonas Everaert; Ivan Grahek; Wouter Duyck; Jana Buelens; Nathan Van den Bergh; Ernst H. W. Koster Mapping the interplay among cognitive biases, emotion regulation, and depressive symptoms Journal Article In: Cognition and Emotion, vol. 31, no. 4, pp. 726–735, 2017. @article{Everaert2017a, Cognitive biases and emotion regulation (ER) difficulties have been instrumental in understanding hallmark features of depression. However, little is known about the interplay among these important risk factors to depression. This cross-sectional study investigated how multiple cognitive biases modulate the habitual use of ER processes and how ER habits subsequently regulate depressive symptoms. All participants first executed a computerised version of the scrambled sentences test (interpretation bias measure) while their eye movements were registered (attention bias measure) and then completed questionnaires assessing positive reappraisal, brooding, and depressive symptoms. Path and bootstrapping analyses supported both direct effects of cognitive biases on depressive symptoms and indirect effects via the use of brooding and via the use of reappraisal that was in turn related to the use of brooding. These findings help to formulate a better understanding of how cognitive biases and ER habits interact to maintain depressive symptoms. |
Jonas Everaert; Ivan Grahek; Ernst H. W. Koster Individual differences in cognitive control over emotional material modulate cognitive biases linked to depressive symptoms Journal Article In: Cognition and Emotion, vol. 31, no. 4, pp. 736–746, 2017. @article{Everaert2017, Deficient cognitive control over emotional material and cognitive biases are important mechanisms underlying depression, but the interplay between these emotionally distorted cognitive processes in relation to depressive symptoms is not well understood. This study investigated the relations among deficient cognitive control of emotional information (i.e. inhibition, shifting, and updating difficulties), cognitive biases (i.e. negative attention and interpretation biases), and depressive symptoms. Theory-driven indirect effect models were constructed, hypothesising that deficient cognitive control over emotional material predicts depressive symptoms through negative attention and interpretation biases. Bootstrapping analyses demonstrated that deficient inhibitory control over negative material was related to negative attention bias which in turn predicted a congruent bias in interpretation and subsequently depressive symptoms. Both shifting and updating impairments in response to negative material had an indirect effect on depression severity through negative interpretation bias. No evidence was found for direct effects of deficient cognitive control over emotional material on depressive symptoms. These findings may help to formulate an integrated understanding of the cognitive foundations of depressive symptoms. |
Marzieh Salehi Fadardi; Arne C. Bathke; Solomon W. Harrar; Larry Allen Abel Task-induced changes in idiopathic infantile nystagmus vary with gaze Journal Article In: Optometry and Vision Science, vol. 94, no. 5, pp. 606–615, 2017. @article{Fadardi2017, PURPOSE: Investigations of infantile nystagmus syndrome (INS) at center or at the null position have reported that INS worsens when visual demand is combined with internal states, e.g. stress. Visual function and INS parameters such as foveation time, frequency, amplitude, and intensity can also be influenced by gaze position. We hypothesized that increases from baseline in visual demand and mental load would affect INS parameters at the null position differently than at other gaze positions. METHODS: Eleven participants with idiopathic INS were asked to determine the direction of Tumbling-E targets, whose visual demand was varied through changes in size and contrast, using a staircase procedure. Targets appeared between ±25° in 5° steps. The task was repeated with both mental arithmetic and time restriction to impose higher mental load, confirmed through subjective ratings and concurrent physiological measurements. RESULTS: Within-subject comparisons were limited to the null and 15° away from it. No significant main effects of task on any INS parameters were found. At both locations, high mental load worsened task performance metrics, i.e. lowest contrast (P = .001) and smallest optotype size reached (P = .012). There was a significant interaction between mental load and gaze position for foveation time (P = .02) and for the smallest optotype reached (P = .028). The increase in threshold optotype size from the low to high mental load was greater at the null than away from it. During high visual demand, foveation time significantly decreased from baseline at the null as compared to away from it (mean difference ± SE: 14.19 ± 0.7 msec; P = .010). CONCLUSIONS: Under high visual demand, the effects of increased mental load on foveation time and visual task performance differed at the null as compared to 15° away from it. Assessment of these effects could be valuable when evaluating INS clinically and when considering its impact on patients' daily activities. |
Laura Fademrecht; Isabelle Bülthoff; Stephan Rosa Action recognition is viewpoint-dependent in the visual periphery Journal Article In: Vision Research, vol. 135, pp. 10–15, 2017. @article{Fademrecht2017a, Recognizing actions of others across the whole visual field is required for social interactions. In a previous study, we have shown that recognition is very good even when life-size avatars who were facing the observer carried out actions (e.g. waving) and were presented very far away from the fovea (Fademrecht, Bülthoff, & de la Rosa, 2016). We explored the possibility whether this remarkable performance was owed to life-size avatars facing the observer, which – according to some social cognitive theories (e.g. Schilbach et al., 2013) – could potentially activate different social perceptual processes as profile facing avatars. Participants therefore viewed a life-size stick figure avatar that carried out motion-captured social actions (greeting actions: handshake, hugging, waving; attacking actions: slapping, punching and kicking) in frontal and profile view. Participants' task was to identify the actions as ‘greeting' or as ‘attack' or to assess the emotional valence of the actions. While recognition accuracy for frontal and profile views did not differ, reaction times were significantly faster in general for profile views (i.e. the moving avatar was seen profile on) than for frontal views (i.e. the action was directed toward the observer). Our results suggest that the remarkable well action recognition performance in the visual periphery was not owed to a more socially engaging front facing view. Although action recognition seems to depend on viewpoint, action recognition in general remains remarkable accurate even far into the visual periphery. |
Laura Fademrecht; Judith Nieuwenhuis; Isabelle Bülthoff; Nick Barraclough; Stephan Rosa Action recognition in a crowded environment Journal Article In: i-Perception, pp. 1–19, 2017. @article{Fademrecht2017, So far, action recognition has been mainly examined with small point-light human stimuli presented alone within a narrow central area of the observer's visual field. Yet, we need to recognize the actions of life-size humans viewed alone or surrounded by bystanders, whether they are seen in central or peripheral vision. Here, we examined the mechanisms in central vision and far periphery (40? eccentricity) involved in the recognition of the actions of a life-size actor (target) and their sensitivity to the presence of a crowd surrounding the target. In Experiment 1, we used an action adaptation paradigm to probe whether static or idly moving crowds might interfere with the recognition of a target's action (hug or clap). We found that this type of crowds whose movements were dissimilar to the target action hardly affected action recognition in central and peripheral vision. In Experiment 2, we examined whether crowd actions that were more similar to the target actions affected action recognition. Indeed, the presence of that crowd diminished adaptation aftereffects in central vision as wells as in the periphery. We replicated Experiment 2 using a recognition task instead of an adaptation paradigm. With this task, we found evidence of decreased action recognition accuracy, but this was significant in peripheral vision only. Our results suggest that the presence of a crowd carrying out actions similar to that of the target affects its recognition. We outline how these results can be understood in terms of high-level crowding effects that operate on action-sensitive perceptual channels. |
Hongwei Fan; Xiaochuan Pan; Rubin Wang; Masamichi Sakagami Differences in reward processing between putative cell types in primate prefrontal cortex Journal Article In: PLoS ONE, vol. 12, no. 12, pp. e0189771, 2017. @article{Fan2017a, Single-unit studies in monkeys have demonstrated that neurons in the prefrontal cortex predict the reward type, reward amount or reward availability associated with a stimulus. To examine contributions of pyramidal cells and interneurons in reward processing, single-unit activity was extracellularly recorded in prefrontal cortices of four monkeys performing a reward prediction task. Based on their shapes of spike waveforms, prefrontal neurons were classified into broad-spike and narrow-spike units that represented putative pyramidal cells and interneurons, respectively. We mainly observed that narrow-spike neurons showed higher firing rates but less bursty discharges than did broad-spike neurons. Both narrow-spike and broad-spike cells selectively responded to the stimulus, reward and their interaction, and the proportions of each type of selective neurons were similar between the two cell classes. Moreover, the two types of cells displayed equal reliability of reward or stimulus discrimination. Furthermore, we found that broad-spike and narrow-spike cells showed distinct mechanisms for encoding reward or stimulus information. Broad-spike neurons raised their firing rate relative to the baseline rate to represent the preferred reward or stimulus information, whereas narrow-spike neurons inhibited their firing rate lower than the baseline rate to encode the non-preferred reward or stimulus information. Our results suggest that narrow-spike and broad-spike cells were equally involved in reward and stimulus processing in the prefrontal cortex. They utilized a binary strategy to complementarily represent reward or stimulus information, which was consistent with the task structure in which the monkeys were required to remember two reward conditions and two visual stimuli. |
Mengjiao Fan; Thomson W. L. Wong Visuomotor behaviors in computer-based reaching tasks by young and older adults : Implication for geriatric rehabilitation Journal Article In: Alzheimer's, Dementia & Cognitive Neurology, vol. 1, no. 2, pp. 1–7, 2017. @article{Fan2017, Older adults are more likely to be required to face the problems of deteriorating movement control due to ageing and poor visuomotor adaptation is believed to be one of the important contributors to the problems. Therefore, we assessed motor performance together with gaze behaviors in young and older adults when they were performing computer-based reaching tasks aiming to examine the potential impact of ageing on visuomotor behaviors and adaptation. In this study, visuomotor behaviors in computer-based reaching tasks were quantitatively evaluated under providing online visual feedback or blocking online visual feedback (simulated visual deficiency) conditions. Results revealed that ageing affects motor performance of the reaching tasks significantly in both visual feedback conditions. Older adults performed distinctive gaze behaviors when compared with the young adults. It implies that simulated visual deficiency in the blocking online visual feedback condition may work as a stimulus to cause extra perceptive load during movement execution and, more importantly, ageing induces slower visuomotor adaptation. Therefore, visual deterioration may slow down the process of visuomotor adaptation. Consequently, the results of present study provide us with new insights in how to further improve the Geriatric rehabilitative training methods for older adults in the context of augmenting visuomotor behaviors, for example, by utilizing a welldesigned errorless training methodology to enhance movement automaticity and visuomotor adaption during motor rehabilitation in Geriatric population. |
Sali M. K. Farhan; Robert Bartha; Sandra E. Black; Dale Corbett; Elizabeth Finger; Morris Freedman; Barry Greenberg; David A. Grimes; Robert A. Hegele; Chris Hudson; Peter W. Kleinstiver; Anthony E. Lang; Mario Masellis; William E. McIlroy; Paula M. McLaughlin; Manuel Montero-Odasso; David G. Munoz; Douglas P. Munoz; Stephen Strother; Richard H. Swartz; Sean Symons; Maria Carmela Tartaglia; Lorne Zinman; Michael J. Strong The Ontario Neurodegenerative Disease Research Initiative (ONDRI) Journal Article In: Canadian Journal of Neurological Sciences, vol. 44, no. 2, pp. 196–202, 2017. @article{Farhan2017, Because individuals develop dementia as a manifestation of neurodegenerative or neurovascular disorder, there is a need to develop reliable approaches to their identification. We are undertaking an observational study (Ontario Neurodegenerative Disease Research Initiative [ONDRI]) that includes genomics, neuroimaging, and assessments of cognition as well as language, speech, gait, retinal imaging, and eye tracking. Disorders studied include Alzheimer's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson's disease, and vascular cognitive impairment. Data from ONDRI will be collected into the Brain-CODE database to facilitate correlative analysis. ONDRI will provide a repertoire of endophenotyped individuals that will be a unique, publicly available resource. |
Moritz Feil; Barbara Moser; Mathias Abegg The interaction of pupil response with the vergence system Journal Article In: Graefe's Archive for Clinical and Experimental Ophthalmology, vol. 255, no. 11, pp. 2247–2253, 2017. @article{Feil2017, PURPOSE: A gaze shift from a target at distance to a target at near leads to pupillary constriction. The regulation of this pupillary near response is ill known. We investigated the impact of accommodation, convergence, and proximity on the pupillary diameter. METHODS: We recorded pupil size and vergence eye movements with the use of an infrared eye tracker. We determined the pupillary response in four conditions: (1) after a gaze shift from far to near without accommodation, (2) after a gaze shift from far to near with neither accommodation nor convergence, (3) after accommodation alone, and (4) after accommodation with convergence without a gaze shift to near. These responses were compared to the pupil response of a full near response and to a gaze shift from one far target to another. RESULTS: We found a reliable pupillary near response. The removal of both accommodation and convergence in gaze shift from far to near abolished the pupillary near response. Accommodation alone did not induce pupillary constriction, while convergence and accommodation together induced a pupil response similar to the full near response. CONCLUSIONS: The main trigger for the pupillary response seems to be convergence. Neither accommodation nor proximity alone induce a significant pupillary constriction. This suggests that the miosis of the near triad is closely coupled to the vergence system rather than being independently regulated. |
Claudia Felser; Janna Deborah Drummer Sensitivity to crossover constraints during native and non-native pronoun resolution Journal Article In: Journal of Psycholinguistic Research, vol. 46, no. 3, pp. 771–789, 2017. @article{Felser2017, We report the results from two experiments examining native and non-native Ger-man speakers' sensitivity to crossover constraints on pronoun resolution. Our critical stimuli sentences contained personal pronouns in either strong (SCO) or weak crossover (WCO) configurations. Using eye-movement monitoring during reading and a gender-mismatch par-adigm, Experiment 1 investigated whether a fronted wh-phrase would be considered as a potential antecedent for a pronoun intervening between the wh-phrase and its canonical position. Both native and non-native readers initially attempted coreference in WCO but not in SCO configurations, as evidenced by early gender-mismatch effects in our WCO conditions. Experiment 2 was an offline antecedent judgement task whose results mirrored the SCO/WCO asymmetry observed in our reading-time data. Taken together, our results show that the SCO constraint immediately restricts pronoun interpretation in both native and non-native comprehension, and further suggest that SCO and WCO constraints derive from different sources. |
Jay A. Edelman; Alexa M. Mieses; Kira Konnova; David Shiu The effect of object-centered instructions in Cartesian and polar coordinates on saccade vector. Journal Article In: Journal of Vision, vol. 17, no. 3, pp. 1–12, 2017. @article{Edelman2017, Express saccades (ES) are the most reflexive saccadic eye movements, with very short reaction times of 70–110 ms. It is likely that ES have the shortest saccade reaction times (SRTs) possible given the known physiological and anatomical delays present in sensory and motor systems. Nevertheless, it has been demonstrated that a vector displacement of ES to spatially extended stimuli can be influenced by spatial cognition. Edelman, Kristjansson, and Nakayama (2007) found that when two horizontally separated visual stimuli appear at a random location, the spatial vector, but not the reaction time, of human ES is strongly influenced by an instruction to make a saccade to one side (either left or right) of a visual stimulus array. Presently, we attempt to extend these findings of cognitive effects on saccades in three ways: (a) determining whether ES could be affected by other types of spatial instructions: vertical, polar amplitude, and polar direction; (b) determining whether these spatial effects increased with practice; and (c) determining how these effects depended on SRTs. The results demonstrate that both types of Cartesian as well as polar amplitude instructions strongly affect ES vector, but only modestly affect SRTs. Polar direction instructions had sizable effects only on nonreflexive saccades where the visual stimuli could be viewed for several hundred milliseconds prior to saccade execution. Short- (trial order within a block) and longterm (experience across several sessions) practice had little effect, though the effect of instruction increased with SRT. Such findings suggest a generalized, innate ability of cognition to affect the most reflexive saccadic eye movements. |
Grace Edwards; Céline Paeye; Philippe Marque; Rufin VanRullen; Patrick Cavanagh Predictive position computations mediated by parietal areas: TMS evidence Journal Article In: NeuroImage, vol. 153, pp. 49–57, 2017. @article{Edwards2017, When objects move or the eyes move, the visual system can predict the consequence and generate a percept of the target at its new position. This predictive localization may depend on eye movement control in the frontal eye fields (FEF) and the intraparietal sulcus (IPS) and on motion analysis in the medial temporal area (MT). Across two experiments we examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, right MT, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion, both presented in the contralateral visual field. In trans-saccadic fusion trials, participants saccade toward a stimulus that is replaced with another stimulus during the saccade. Frequently, predictive position mechanisms lead to a fused percept of pre- and post-saccade stimuli (Paeye et al., 2017). We found that rTMS to IPS significantly decreased the frequency of perceiving trans-saccadic fusion within the first 10 min after stimulation. In the flash grab illusion, a target is flashed on a moving background leading to the percept that the target has shifted in the direction of the motion after the flash (Cavanagh and Anstis, 2013). In the first experiment, the reduction in the flash grab illusion after rTMS to IPS and FEF did not reach significance. In the second experiment, using a stronger version of the flash grab, the illusory shift did decrease significantly after rTMS to IPS although not after rTMS to FEF or to MT. These findings suggest that right IPS contributes to predictive position perception during saccades and motion processing in the contralateral visual field. |
John M. Egan; Gerard M. Loughnane; Helen Fletcher; Emma Meade; Edmund C. Lalor A gaze independent hybrid-BCI based on visual spatial attention Journal Article In: Journal of Neural Engineering, vol. 14, no. 4, pp. 1–8, 2017. @article{Egan2017, Objective. Brain-computer interfaces (BCI) use measures of brain activity to convey a user's intent without the need for muscle movement. Hybrid designs, which use multiple measures of brain activity, have been shown to increase the accuracy of BCIs, including those based on EEG signals reflecting covert attention. Our study examined whether incorporating a measure of the P3 response improved the performance of a previously reported attention-based BCI design that incorporates measures of steady-state visual evoked potentials (SSVEP) and alpha band modulations. Approach. Subjects viewed stimuli consisting of two bi-laterally located flashing white boxes on a black background. Streams of letters were presented sequentially within the boxes, in random order. Subjects were cued to attend to one of the boxes without moving their eyes, and they were tasked with counting the number of target-letters that appeared within. P3 components evoked by target appearance, SSVEPs evoked by the flashing boxes, and power in the alpha band are modulated by covert attention, and the modulations can be used to classify trials as left-attended or right-attended. Main Results. We showed that classification accuracy was improved by including a P3 feature along with the SSVEP and alpha features (the inclusion of a P3 feature lead to a 9% increase in accuracy compared to the use of SSVEP and Alpha features alone). We also showed that the design improves the robustness of BCI performance to individual subject differences. Significance. These results demonstrate that incorporating multiple neurophysiological indices of covert attention can improve performance in a gaze-independent BCI. |
Benedikt V. Ehinger; Katja I. Häuser; José P. Ossandón; Peter König Humans treat unreliable filled-in percepts as more real than veridical ones Journal Article In: eLife, vol. 6, pp. 1–17, 2017. @article{Ehinger2017, Humans often evaluate sensory signals according to their reliability for optimal decision-making. However, how do we evaluate percepts generated in the absence of direct input that are, therefore, completely unreliable? Here, we utilize the phenomenon of filling-in occurring at the physiological blind-spots to compare partially inferred and veridical percepts. Subjects chose between stimuli that elicit filling-in, and perceptually equivalent ones presented outside the blind-spots, looking for a Gabor stimulus without a small orthogonal inset. In ambiguous conditions, when the stimuli were physically identical and the inset was absent in both, subjects behaved opposite to optimal, preferring the blind-spot stimulus as the better example of a collinear stimulus, even though no relevant veridical information was available. Thus, a percept that is partially inferred is paradoxically considered more reliable than a percept based on external input. In other words: Humans treat filled-in inferred percepts as more real than veridical ones. |
Wolfgang Einhäuser; Philipp Methfessel; Alexandra Bendixen Newly acquired audio-visual associations bias perception in binocular rivalry Journal Article In: Vision Research, vol. 133, pp. 121–129, 2017. @article{Einhaeuser2017, When distinct stimuli are presented to the two eyes, their mental representations alternate in awareness. Here, such “binocular rivalry” was used to investigate whether audio-visual associations bias visual perception. To induce two arbitrary associations, each between a tone and a grating of a specific color and motion direction, observers were required to respond whenever this combination was presented, but not for other tone-grating combinations. After about 20 min of this induction phase, each of the gratings was presented to one eye to induce rivalry, while either of the two tones or no tone was played. Observers were asked to watch the rivaling stimuli and listen to the tones. The observer's dominant percept was assessed throughout by measuring the optokinetic nystagmus (OKN), whose slow phase follows the direction of the currently dominant grating. We found that perception in rivalry was affected by the concurrently played tone. Results suggest a bias towards the grating that had been associated with the concurrently presented tone and prolonged dominance durations for this grating compared to the other. Numerically, conditions without tone fell in-between for measures of bias and dominance duration. Our data show that a rapidly acquired arbitrary audio-visual association biases visual perception. Unlike previously reported cross-modal interactions in rivalry, this effect can neither be explained by a pure attentional (dual-task) effect, nor does it require a fixed physical or semantic relation between the auditory and visual stimulus. This suggests that audio-visual associations that are quickly formed by associative learning may affect visual representations directly. |
Wolfgang Einhäuser; Sabine Thomassen; Alexandra Bendixen Using binocular rivalry to tag foreground sounds: Towards an objective visual measure for auditory multistability Journal Article In: Journal of Vision, vol. 17, no. 1, pp. 1–19, 2017. @article{Einhaeuser2017a, In binocular rivalry, paradigms have been proposed for unobtrusive moment-by-moment readout of observers' perceptual experience (‘‘no-report paradigms''). Here, we take a first step to extend this concept to auditory multistability. Observers continuously reported which of two concurrent tone sequences they perceived in the foreground: high-pitch (1008 Hz) or low-pitch (400 Hz) tones. Interstimulus intervals were either fixed per sequence (Experiments 1 and 2) or random with tones alternating (Experiment 3). A horizontally drifting grating was presented to each eye; to induce binocular rivalry, gratings had distinct colors and motion directions. To associate each grating with one tone sequence, a pattern on the grating jumped vertically whenever the respective tone occurred. We found that the direction of the optokinetic nystagmus (OKN)—induced by the visually dominant grating—could be used to decode the tone (high/low) that was perceived in the foreground well above chance. This OKN-based readout improved after observers had gained experience with the auditory task (Experiments 1 and 2) and for simpler auditory tasks (Experiment 3). We found no evidence that the visual stimulus affected auditory multistability. Although decoding performance is still far from perfect, our paradigm may eventually provide a continuous estimate of the currently dominant percept in auditory multistability. |
Tomer Elbaum; Michael Wagner; Assaf Botzer Cyclopean , dominant , and non-dominant gaze tracking for smooth pursuit gaze interaction Journal Article In: Journal of Eye Movement Research, vol. 10, no. 1, pp. 1–14, 2017. @article{Elbaum2017, User-centered design questions in gaze interfaces have been explored in multitude empirical investigations. Interestingly, the question of what eye should be the input device has never been studied. We compared tracking accuracy between the "cyclopean" (i.e., mid-point between eyes) dominant and non-dominant eye. In two experiments, participants performed tracking tasks. In Experiment 1, participants did not use a crosshair. Results showed that mean distance from target was smaller with cyclopean than with dominant or non-dominant eyes. In Experiment 2, participants controlled a crosshair with their cyclopean, dominant and non-dominant eye intermittently and had to align the crosshair with the target. Overall tracking accuracy was highest with cyclopean eye, yet similar between cyclopean and dominant eye in the second half of the experiment. From a theoretical viewpoint, our findings correspond with the cyclopean eye theory of egocentric direction and provide indication for eye dominance, in accordance with the hemispheric laterality approach. From a practical viewpoint, we show that what eye to use as input should be a design consideration in gaze interfaces. |
Albert End; Matthias Gamer Preferential processing of social features and their interplay with physical saliency in complex naturalistic scenes Journal Article In: Frontiers in Psychology, vol. 8, pp. 418, 2017. @article{End2017, According to so-called saliency-based attention models, attention during free viewing of visual scenes is particularly allocated to physically salient image regions. In the present study, we assumed that social features in complex naturalistic scenes would be processed preferentially irrespective of their physical saliency. Therefore, we expected worse prediction of gazing behavior by saliency-based attention models when social information is present in the visual field. To test this hypothesis, participants freely viewed color photographs of complex naturalistic social (e.g., including heads, bodies) and non-social (e.g., including landscapes, objects) scenes while their eye movements were recorded. In agreement with our hypothesis, we found that social features (especially heads) were heavily prioritized during visual exploration. Correspondingly, the presence of social information weakened the influence of low-level saliency on gazing behavior. Importantly, this pattern was most pronounced for the earliest fixations indicating automatic attentional processes. These findings were further corroborated by a linear mixed model approach showing that social features (especially heads) add substantially to the prediction of fixations beyond physical saliency. Taken together, the current study indicates gazing behavior for naturalistic scenes to be better predicted by the interplay of social and physically salient features than by low-level saliency alone. These findings strongly challenge the generalizability of saliency-based attention models and demonstrate the importance of considering social influences when investigating the driving factors of human visual attention. |
Vivian Eng; Alfred Lim; Simon Kwon; Su Ren Gan; S. Azrin Jamaluddin; Steve M. J. Janssen; Jason Satel Stimulus-response incompatibility eliminates inhibitory cueing effects with saccadic but not manual responses Journal Article In: Attention, Perception, and Psychophysics, vol. 79, no. 4, pp. 1097–1106, 2017. @article{Eng2017, There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomotor system is activated or suppressed. When saccades are allowed, output-based IOR is generated, whereas input-based IOR arises when saccades are prohibited. In a series of 4 experiments, we mixed or blocked compatible and incompatible trials with saccadic or manual responses to investigate whether cueing effects would follow the same pattern as those observed with more traditional peripheral onsets and central arrows. In all experiments, an uninformative cue was displayed, followed by a cue-back stimulus that was either red or green, indicating whether a compatible or incompatible response was required. The results showed that IOR was indeed observed for compatible responses in all tasks, whereas IOR was eliminated for incompatible trials-but only with saccadic responses. These findings indicate that the dissociation between input- and output-based forms of IOR depends on more than just oculomotor activation, providing further support for the existence of an inhibitory cueing effect that is distinct to the manual response modality. |
Ian M. Erkelens; William R. Bobier Asymmetries between convergence and divergence reveal tonic vergence is dependent upon phasic vergence function Journal Article In: Journal of Vision, vol. 17, no. 5, pp. 1–16, 2017. @article{Erkelens2017, Horizontal vergence eye movements are controlled by two processes, phasic and slow-tonic. Slow-tonic responses are hypothesized to be stimulated by the faster, pulse-step neural output of the phasic system. This suggests that the general behavior of each system should be similar; however, this relationship has yet to be investigated directly. We characterize the relationship between phasic and tonic vergence by quantifying directional asymmetries in the response properties of each mechanism to the same disparity amplitudes. Four subjects viewed symmetric steps in disparity dichoptically at 40 cm while eye movements were recorded with infrared oculography. First- and secondorder phasic and slow-tonic convergence response properties increased linearly with disparity demand (p < 0.01), whereas divergence responses did not (p > 0.05). Phasic divergence responses were slower than convergence (p = 0.012) and were associated with a higher frequency of saccades (p < 0.001). The average rate of slow-tonic change was correlated to the average peak velocity of phasic vergence at the same vergence demand in both directions |
Yulia Esaulova; Chiara Reali; Lisa Stockhausen Prominence of gender cues in the assignment of thematic roles in German Journal Article In: Applied Psycholinguistics, vol. 38, no. 5, pp. 1133–1172, 2017. @article{Esaulova2017, Two eye-tracking experiments examined influences of grammatical and stereotypical gender cues on the assignment of thematic roles in German. Participants (N 1 = 32, N 2 = 40) read sentences with subject- and object-extracted relative clauses, where thematic agents and patients remained ambiguous until the end of the relative clause. The results reveal a linguistic gender bias: agent roles are assigned more easily to grammatically masculine than feminine role nouns and stereotypically neutral than female ones. The opposite pattern is observed in the assignment of patient roles for stereotypical but not grammatical gender. The findings are discussed within the framework of situation model theories as well as in constraint-based and similarity-based interference accounts, while gender is viewed as a dimension of prominence. |
Joshua J. Foster; Emma M. Bsales; Russell J. Jaffe; Edward Awh Alpha-band activity reveals spontaneous representations of spatial position in visual working memory Journal Article In: Current Biology, vol. 27, no. 20, pp. 3216–3223, 2017. @article{Foster2017, An emerging view suggests that spatial position is an integral component of working memory (WM), such that non-spatial features are bound to locations regardless of whether space is relevant [1, 2]. For instance, past work has shown that stimulus position is spontaneously remembered when non-spatial fea- tures are stored. Item recognition is enhanced when memoranda appear at the same location where they were encoded [3–5], and accessing non-spatial infor- mation elicits shifts of spatial attention to the original position of the stimulus [6, 7]. However, these find- ings do not establish that a persistent, active repre- sentation of stimulus position is maintained in WM because similar effects have also been documented following storage in long-termmemory [8, 9]. Here we show that the spatial position of the memorandum is actively coded by persistent neural activity during a non-spatial WM task. We used a spatial encoding model in conjunction with electroencephalogram (EEG) measurements of oscillatory alpha-band (8– 12 Hz) activity to track active representations of spatial position. The position of the stimulus varied trial to trial but was wholly irrelevant to the tasks. We nevertheless observed active neural representa- tions of the original stimulus position that persisted throughout the retention interval. Further experi- ments established that these spatial representations are dependent on the volitional storage of non- spatial features rather than being a lingering effect of sensory energy or initial encoding demands. These findings provide strong evidence that online spatial representations are spontaneously main- tained in WM—regardless of task relevance—during the storage of non-spatial features. |
Tom Foulsham; Alan Kingstone Are fixations in static natural scenes a useful predictor of attention in the real world? Journal Article In: Canadian Journal of Experimental Psychology, vol. 71, no. 2, pp. 172–181, 2017. @article{Foulsham2017, Research investigating scene perception normally involves laboratory experiments using static images. Much has been learned about how observers look at pictures of the real world and the attentional mechanisms underlying this behaviour. However, the use of static, isolated pictures as a proxy for studying everyday attention in real environments has led to the criticism that such experiments are artificial. We report a new study that tests the extent to which the real world can be reduced to simpler laboratory stimuli. We recorded the gaze of participants walking on a university campus with a mobile eye tracker, and then showed static frames from this walk to new participants, in either a random or sequential order. The aim was to compare the gaze of participants walking in the real environment with fixations on pictures of the same scene. The data show that picture order affects interobserver fixation consistency and changes looking patterns. Critically, while fixations on the static images overlapped significantly with the actual real-world eye movements, they did so no more than a model that assumed a general bias to the centre. Remarkably, a model that simply takes into account where the eyes are normally positioned in the head—independent of what is actually in the scene—does far better than any other model. These data reveal that viewing patterns to static scenes are a relatively poor proxy for predicting real world eye movement behaviour, while raising intriguing possibilities for how to best measure attention in everyday life. |
Edward G. Freedman; Sophie Molholm; Michael J. Gray; Daniel Belyusar; John J. Foxe Saccade adaptation deficits in developmental dyslexia suggest disruption of cerebellar-dependent learning Journal Article In: Journal of Neurodevelopmental Disorders, vol. 9, no. 1, pp. 1–8, 2017. @article{Freedman2017, Background: Estimates of the prevalence of developmental dyslexia in the general population range from 5% to as many as 10%. Symptoms include reading, writing, and language deficits, but the severity and mix of symptoms can vary widely across individuals. In at least some people with dyslexia, the structure and function of the cerebellum may be disordered. Saccadic adaptation requires proper function of the cerebellum and brainstem circuitry and might provide a simple, noninvasive assay for early identification and sub-phenotyping in populations of children who may have dyslexia. Methods: Children between the ages of 7 and 15 served as participants in this experiment. Fifteen had been diagnosed with developmental dyslexia and an additional 15 were typically developing children. Five of the participants diagnosed with dyslexia were also diagnosed with an attention deficit hyperactivity disroder and were excluded from further analyses. Participants performed in a saccadic adaptation task in which visual errors were introduced at the end of saccadic eye movements. The amplitudes of primary saccades were measured and plotted as a function of the order in which they occurred. Lines of best fit were calculated. Significant changes in the amplitude of primary saccades were identified. |
Lee Friedman; Mark S. Nixon; Oleg V. Komogortsev Method to assess the temporal persistence of potential biometric features: Application to oculomotor, gait, face and brain structure databases Journal Article In: PLoS ONE, vol. 12, no. 6, pp. e0178501, 2017. @article{Friedman2017, We introduce the intraclass correlation coefficient (ICC) to the biometric community as an index of the temporal persistence, or stability, of a single biometric feature. It requires, as input, a feature on an interval or ratio scale, and which is reasonably normally distributed, and it can only be calculated if each subject is tested on 2 or more occasions. For a biometric system, with multiple features available for selection, the ICC can be used to measure the relative stability of each feature. We show, for 14 distinct data sets (1 synthetic, 8 eye-movementrelated, 2 gait-related, and 2 face-recognition-related, and one brain-structure-related), that selecting the most stable features, based on the ICC, resulted in the best biometric performance generally. Analyses based on using only the most stable features produced superior Rank-1-Identification Rate (Rank-1-IR) performance in 12 of 14 databases (p = 0.0065, onetailed), when compared to other sets of features, including the set of all features. For Equal Error Rate (EER), using a subset of only high-ICC features also produced superior performance in 12 of 14 databases (p = 0. 0065, one-tailed). In general, then, for our databases, prescreening potential biometric features, and choosing only highly reliable features yields better performance than choosing lower ICC features or than choosing all features combined. We also determined that, as the ICC of a group of features increases, the median of the genuine similarity score distribution increases and the spread of this distribution decreases. There was no statistically significant similar relationships for the impostor distributions. We believe that the ICC will find many uses in biometric research. In case of the eye movement-driven biometrics, the use of reliable features, as measured by ICC, allowed to us achieve the authentication performance with EER = 2.01%, which was not possible before. |
Steven Frisson; David R. Harvey; Adrian Staub No prediction error cost in reading: Evidence from eye movements Journal Article In: Journal of Memory and Language, vol. 95, pp. 200–214, 2017. @article{Frisson2017, Two eye movement while reading experiments address the issue of how reading of an unpredictable word is influenced by the presence of a more predictable alternative. The experiments replicate the robust effects of predictability on the probability of skipping and on early and late reading time measures. However, in both experiments, an unpredictable but plausible word was read no more slowly when another word was highly predictable (i.e., in a constraining context) than when no word was highly predictable (i.e., in a neutral context). In fact, an unpredictable word that was semantically related to the predictable alternative demonstrated facilitation in the constraining context, in relatively late eye movement measures. These results, which are consistent with Luke and Christianson's (2016) corpus study, provide the first evidence from a controlled experimental design for the absence of a prediction error cost, and for facilitation of an unpredictable but semantically related word, during normal reading. The findings support a model of lexical predictability effects in which there is broad pre-activation of potential continuations, rather than discrete predictions of specific lexical items. Importantly, pre-activation of likely continuations does not result in processing difficulty when some other word is actually encountered. |
Kumiko Fukumura; Roger P. G. Gompel How do violations of Gricean maxims affect reading? Journal Article In: Journal of Memory and Language, vol. 95, pp. 1–18, 2017. @article{Fukumura2017, Four eye-tracking experiments examined how violations of the Gricean maxim of quantity affect reading. Experiments 1 and 2 showed that first-pass reading times for size-modified definite nouns (the small towel) were longer when the modifier was redundant, as the context contained one rather than two possible referents, whereas first-pass times for bare nouns (the towel) were unaffected by whether the context contained multiple referents that resulted in ambiguity. Experiment 3 showed that unlike redundant size modifiers, redundant color modifiers did not increase first-pass times. Experiment 4 confirmed this finding, demonstrating that the effect of redundancy was dependent on the meaning of the modifier. We propose that initial referential processing is led by the lexico-semantic representation of the referring expression rather than Gricean expectations about optimal informativeness: Redundancy of a size-modifier immediately disrupts comprehension because the processor fails to activate the referential contrast implied by the meaning of the modifier, whereas referential ambiguity has no immediate effect, as it allows the activation of at least one semantically-compatible referent. |
Amber M. Fyall; Yasmine El-Shamayleh; Hannah Choi; Eric Shea-Brown; Anitha Pasupathy Dynamic representation of partially occluded objects in primate prefrontal and visual cortex Journal Article In: eLife, vol. 6, pp. 1–25, 2017. @article{Fyall2017, Successful recognition of partially occluded objects is presumed to involve dynamic interactions between brain areas responsible for vision and cognition, but neurophysiological evidence for the involvement of feedback signals is lacking. Here, we demonstrate that neurons in the ventrolateral prefrontal cortex (vlPFC) of monkeys performing a shape discrimination task respond more strongly to occluded than unoccluded stimuli. In contrast, neurons in visual area V4 respond more strongly to unoccluded stimuli. Analyses of V4 response dynamics reveal that many neurons exhibit two transient response peaks, the second of which emerges after vlPFC response onset and displays stronger selectivity for occluded shapes. We replicate these findings using a model of V4/vlPFC interactions in which occlusion-sensitive vlPFC neurons feed back to shape- selective V4 neurons, thereby enhancing V4 responses and selectivity to occluded shapes. These results reveal how signals from frontal and visual cortex could interact to facilitate object recognition under occlusion. |
Kacie Dougherty; Michele A. Cox; Taihei Ninomiya; David A. Leopold; Alexander Maier Ongoing alpha activity in V1 regulates visually driven spiking responses Journal Article In: Cerebral Cortex, vol. 27, no. 2, pp. 1113–1124, 2017. @article{Dougherty2017, The interlaminar connections in the primate primary visual cortex (V1) are well described, as is the presence of ongoing alpha-range (7-14 Hz) fluctuations in this area. Less well understood is how these interlaminar connections and ongoing fluctuations contribute to the regulation of visual spiking responses. Here, we investigate the relationship between alpha fluctuations and spiking responses to visual stimuli across cortical layers. Using laminar probes in macaque V1, we show that neural firing couples with the phase of alpha fluctuations, and that magnitude of this coupling is particularly pronounced during visual stimulation. The strongest modulation of spiking activity was observed in layers 2/3. Alpha-spike coupling and current source density analysis pointed to an infragranular origin of the alpha fluctuations. Taken together, these results indicate that ongoing infragranular alpha-range fluctuations in V1 play a role in regulating columnar visual activity. |
Trafton Drew; Sage E. P. Boettcher; Jeremy M. Wolfe One visual search, many memory searches: An eye-tracking investigation of hybrid search Journal Article In: Journal of Vision, vol. 17, no. 11, pp. 1–10, 2017. @article{Drew2017a, Suppose you go to the supermarket with a shopping list of 10 items held in memory. Your shopping expedition can be seen as a combination of visual search and memory search. This is known as "hybrid search." There is a growing interest in understanding how hybrid search tasks are accomplished. We used eye tracking to examine how manipulating the number of possible targets (the memory set size [MSS]) changes how observers (Os) search. We found that dwell time on each distractor increased with MSS, suggesting a memory search was being executed each time a new distractor was fixated. Meanwhile, although the rate of refixation increased with MSS, it was not nearly enough to suggest a strategy that involves repeatedly searching visual space for subgroups of the target set. These data provide a clear demonstration that hybrid search tasks are carried out via a "one visual search, many memory searches" heuristic in which Os examine items in the visual array once with a very low rate of refixations. For each item selected, Os activate a memory search that produces logarithmic response time increases with increased MSS. Furthermore, the percentage of distractors fixated was strongly modulated by the MSS: More items in the MSS led to a higher percentage of fixated distractors. Searching for more potential targets appears to significantly alter how Os approach the task, ultimately resulting in more eye movements and longer response times. |
Trafton Drew; Lauren H. Williams Simple eye-movement feedback during visual search is not helpful Journal Article In: Cognitive Research: Principles and Implications, vol. 2, no. 44, pp. 1–8, 2017. @article{Drew2017, Searching for targets in the visual world, or visual search, is something we all do every day. We frequently make 'false-negative' errors, wherein we erroneously conclude a target was absent when one was, in fact, present. These sorts of errors can have tremendous costs, as when signs of cancers are missed in diagnostic radiology. Prior research has characterized the cause of many of these errors as being due to failure to completely search the area where targets may be present; indeed, roughly one-third of chest nodules missed in lung cancer screening are never fixated (Drew, Võ, Olwal, Jacobson, Seltzer and Wolfe, Journal of Vision 13:3, 2013). This suggests that observers do not have a good representation of what areas have and have not been searched prior to declaring an area target free. Therefore, in six experiments, we sought to examine the utility of reducing the uncertainty with respect to what areas had been examined via online eye-tracking feedback. We hypothesized that providing information about what areas had or had not been examined would lead to lower rates of false negatives or more efficient search, namely faster response times with no cost on target detection accuracy. Neither of these predictions held true. Over six experiments, online eye-tracking feedback did not yield any reliable performance benefits. |
Denis Drieghe; Lei Cui; Guoli Yan; Bai Xuejun; Chi Hui; Simon P. Liversedge The morphosyntactic structure of compound words influences parafoveal processing in Chinese reading Journal Article In: Quarterly Journal of Experimental Psychology, vol. 71, no. 1, pp. 190–197, 2017. @article{Drieghe2017a, In an eye movement experiment employing the boundary paradigm, we compared parafoveal preview benefit during the reading of Chinese sentences. The target word was a two-character compound that had either a noun–noun or an adjective–noun structure each sharing an identical noun as the second character. The boundary was located between the two characters of the compound word. Prior to the eyes crossing the boundary, the preview of the second character was presented either normally or was replaced by a pseudocharacter. Previously, Juhasz, Inhoff, and Rayner observed that inserting a space into a normally unspaced compound in English significantly disrupted processing and that this disruption was larger for adjective–noun compounds than for noun–noun compounds. This finding supports the hypothesis that, at least in English, for adjective–noun compounds, the noun is more important for lexical identification than the adjective, while for noun–noun compounds, both constituents are similar in importance for lexical identification. Our results indicate a similar division of the importance of compounds in reading in Chinese as the pseudocharacter preview was more disruptive for the adjective–noun compounds than for the noun–noun compounds. These findings also indicate that parafoveal processing can be influenced by the morphosyntactic structure of the currently fixated character. |
Denis Drieghe; Gemma Fitzsimmons; Simon P. Liversedge Parafoveal preview effects in reading unspaced text Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 43, no. 10, pp. 1701–1716, 2017. @article{Drieghe2017, In English reading, eye guidance relies heavily on the spaces between words for demarcating word boundaries. In an eye tracking experiment, we examined the impact of removing spaces on parafoveal processing. Using the gaze-contingent boundary paradigm (Rayner, 1975), a high or low frequency preboundary word was followed by a postboundary preview presented either normally (i.e., identical to the postboundary word), or with letters replaced creating an orthographically illegal preview. The spaces between words were either retained or removed. Results replicate previous findings of increased reading times during unspaced reading (Rayner, Fischer, & Pollatsek, 1998) and indicate rather limited evidence for more distributed processing: Observations of processing of the previous word (spill-over effects) or processing of the next word (parafoveal-on-foveal effects) influencing fixation durations on the currently fixated word were limited. Spill-over effects were only observed in the unspaced layout when the postboundary preview was correct, presumably because the orthographically illegal, incorrect preview was visually salient enough to allow for relatively easy word segmentation and therefore more focused processing of the preboundary word. As such, results points toward a system that prefers narrowly focused processing of a single word, at least when means for easy word segmentation are available. |
João Valente Duarte; Gabriel Nascimento Costa; Ricardo Martins; Miguel Castelo-Branco Pivotal role of hMT+ in long-range disambiguation of interhemispheric bistable surface motion Journal Article In: Human Brain Mapping, vol. 38, no. 10, pp. 4882–4897, 2017. @article{Duarte2017, It remains an open question whether long-range disambiguation of ambiguous surface motion can be achieved in early visual cortex or instead in higher level regions, which concerns object/surface segmentation/integration mechanisms. We used a bistable moving stimulus that can be perceived as a pattern comprehending both visual hemi-fields moving coherently downward or as two widely segregated nonoverlapping component objects (in each visual hemi-field) moving separately inward. This paradigm requires long-range integration across the vertical meridian leading to interhemispheric binding. Our fMRI study (n = 30) revealed a close relation between activity in hMT+ and perceptual switches involving interhemispheric segregation/integration of motion signals, crucially under nonlocal conditions where components do not overlap and belong to distinct hemispheres. Higher signal changes were found in hMT+ in response to spatially segregated component (incoherent) percepts than to pattern (coherent) percepts. This did not occur in early visual cortex, unlike apparent motion, which does not entail surface segmentation. We also identified a role for top–down mechanisms in state transitions. Deconvolution analysis of switch-related changes revealed prefrontal, insula, and cingulate areas, with the right superior parietal lobule (SPL) being particularly involved. We observed that directed influences could emerge either from left or right hMT+ during bistable motion integration/segregation. SPL also exhibited significant directed functional connectivity with hMT+, during perceptual state maintenance (Granger causality analysis). Our results suggest that long-range interhemispheric binding of ambiguous motion representations mainly reflect bottom–up processes from hMT+ during perceptual state maintenance. In contrast, state transitions maybe influenced by high-level regions such as the SPL. |
Andrew T. Duchowski; Nina A. Gehrer; Michael Schönenberg An inverse-linear logistic model of the main sequence Journal Article In: Journal of Eye Movement Research, vol. 10, no. 3, pp. 1–19, 2017. @article{Duchowski2017, A model of the main sequence is proposed based on the logistic function. The model's fit to the peak velocity-amplitude relation resembles an S curve, simultaneously allowing control of the curve's asymptotes at very small and very large amplitudes, as well as its slope over the mid-amplitude range. The proposed inverse-linear logistic model is also able to express the linear relation of duration and amplitude. We demonstrate the utility and robustness of the model when fit to aggregate data at the small- and mid-amplitude ranges, namely when fitting microsaccades, saccades, and superposition of both. We are confident the model will suitably extend to the large- amplitude range of eye movements. |
Felix Duecker; Teresa Schuhmann; Nina Bien; Christianne Jacobs; Alexander T. Sack In: Journal of Cognitive Neuroscience, vol. 29, no. 7, pp. 1267–1278, 2017. @article{Duecker2017, The concept of interhemispheric competition has been very influential in attention research, and the occurrence of biased attention due to an imbalance in posterior parietal cortex (PPC) is well documented. In this context, the vast majority of studies have assessed attentional performance with tasks that did not include an explicit experimental manipulation of attention, and, as a consequence, it remains largely unknown how these findings relate to core attentional constructs such as endogenous and exogenous control and spatial orienting and reorient- ing. We here addressed this open question by creating an imbalance between left and right PPC with transcranial direct current stimulation, resulting in right-hemispheric dominance, and assessed performance on three experimental paradigms that isolate distinct attentional processes. The comparison between active and sham transcranial direct current stimulations revealed a highly informative pattern of results with differential effects across tasks. Our results demonstrate the functional necessity of PPC for endogenous and exogenous attentional control and, importantly, link the concept of interhemispheric competition to core attentional processes, thus moving beyond the notion of biased attention after noninvasive brain stimulation over PPC. |
Laura Dugué; Alice M. Xue; Marisa Carrasco Distinct perceptual rhythms for feature and conjunction searches Journal Article In: Journal of Vision, vol. 17, no. 3, pp. 1–15, 2017. @article{Dugue2017, Feature and conjunction searches are widely used to study attentional deployment. However, the spatiotemporal behavior of attention integration in these tasks remains under debate. Are multiple search stimuli processed in parallel or sequentially? Does sampling of visual information and attentional deployment differ between these two types of search? If so, how? We used an innovative methodology to estimate the distribution of attention on a single-trial basis for feature and conjunction searches. Observers performed feature- and conjunction-search tasks. They had to detect and discriminate a tilted low-spatial-frequency grating among three low-spatial-frequency vertical gratings (feature search) or low-spatial-frequency vertical gratings and high-spatial-frequency tilted gratings (conjunction search). After a variable delay, two probes were flashed at random locations. Performance in reporting the probes was used to infer attentional deployment to those locations. By solving a second-degree equation, we determined the probability of probe report at the most (P1) and least (P2) attended locations on a given trial. Were P1 and P2 equal, we would conclude that attention had been uniformly distributed across all four locations. Otherwise, we would conclude that visual information sampling and attentional deployment had been nonuniformly distributed. Our results show that processing was nonuniformly distributed across the four locations in both searches, and was modulated periodically over time at ;5 Hz for the conjunction search and ;12 Hz for the feature search. We argue that the former corresponds to the periodicity of attentional deployment during the search, whereas the latter corresponds to ongoing sampling of visual information. Because different locations were not simultaneously processed, this study rules out a strict parallel model for both search types. |