N Zaretskaya

Disrupting Parietal Function Prolongs Dominance Durations in Binocular Rivalry

Human brain imaging studies of bistable perceptual phenomena revealed that frontal and parietal areas are activated during perceptual switches between the two conflicting percepts. However, these studies do not provide information about causality, i.e., whether activity reports a consequence or a cause of the perceptual change. Here we used functional magnetic resonance imaging to individually localize four parietal regions involved in perceptual switches during binocular rivalry in 15 subjects and subsequently disturbed their neural processing and that of a control site using 2 Hz repetitive transcranial magnetic stimulation (TMS) during binocular rivalry. We found that TMS over one of the sites, the right intraparietal sulcus (IPS), prolonged the periods of stable percepts. Additionally, the more lateralized the blood oxygen level-dependent signal was in IPS, the more lateralized the TMS effects were. Lateralization varied considerably across subjects, with a right-hemispheric bias. Control replay experiments rule out nonspecific effects of TMS on task performance, reaction times, or eye blinks. Our results thus demonstrate a causal, destabilizing, and individually lateralized effect of normal IPS function on perceptual continuity in rivalry. This is in accord with a role of IPS in perceptual selection, relating its role in rivalrous perception to that in attention.

Parietal Cortex Mediates Conscious Perception of Illusory Gestalt

Grouping local elements into a holistic percept, also known as spatial binding, is crucial for meaningful perception. Previous studies have shown that neurons in early visual areas V1 and V2 can signal complex grouping-related information, such as illusory contours or object-border ownerships. However, relatively little is known about higher-level processes contributing to these signals and mediating global Gestalt perception. We used a novel bistable motion illusion that induced alternating and mutually exclusive vivid conscious experiences of either dynamic illusory contours forming a global Gestalt or moving ungrouped local elements while the visual stimulation remained the same. fMRI in healthy human volunteers revealed that activity fluctuations in two sites of the parietal cortex, the superior parietal lobe and the anterior intraparietal sulcus (aIPS), correlated specifically with the perception of the grouped illusory Gestalt as opposed to perception of ungrouped local elements. We then disturbed activity at these two sites in the same participants using transcranial magnetic stimulation (TMS). TMS over aIPS led to a selective shortening of the duration of the global Gestalt percept, with no effect on that of local elements. The results suggest that aIPS activity is directly involved in the process of spatial binding during effortless viewing in the healthy brain. Conscious perception of global Gestalt is therefore associated with aIPS function, similar to attention and perceptual selection.

Gestalt perception is associated with reduced parietal beta oscillations.

The ability to perceive composite objects as a whole is fundamental for visual perception in a complex and cluttered natural environment. This ability may be mediated by increased communication between neural representations of distinct object elements, and has been linked to increased synchronization of oscillatory brain activity in the gamma band. Previous studies of perceptual grouping either guided attention between local and global aspects of a given stimulus or manipulated its physical properties to achieve grouped and ungrouped perceptual conditions. In contrast to those studies, we fully matched the physical properties underlying global and local percepts using a bistable stimulus that causes the viewer to perceive either local motion of multiple elements or global motion of two illusory shapes without any external change. To test the synchronization hypothesis we recorded brain activity with EEG, while human participants viewed the stimulus and reported changes in their perception. In contrast to previous findings we show that power of the beta-band was lower during perception of global Gestalt than during that of local elements. Source localization places these differences in the posterior parietal cortex, overlapping with a site previously associated with both attention and Gestalt perception. These findings reveal a role of parietal beta-band activity in internally, rather than externally or attention-driven processes of Gestalt perception. They also add to the growing evidence for shared neural substrates of attention and Gestalt perception, both being linked to parietal cortex.

Analysis strategies for high-resolution UHF-fMRI data

ABSTRACT Functional MRI (fMRI) benefits from both increased sensitivity and specificity with increasing magnetic field strength, making it a key application for Ultra‐High Field (UHF) MRI scanners. Most UHF‐fMRI studies utilize the dramatic increases in sensitivity and specificity to acquire high‐resolution data reaching sub‐millimeter scales, which enable new classes of experiments to probe the functional organization of the human brain. This review article surveys advanced data analysis strategies developed for high‐resolution fMRI at UHF. These include strategies designed to mitigate distortion and artifacts associated with higher fields in ways that attempt to preserve spatial resolution of the fMRI data, as well as recently introduced analysis techniques that are enabled by these extremely high‐resolution data. Particular focus is placed on anatomically‐informed analyses, including cortical surface‐based analysis, which are powerful techniques that can guide each step of the analysis from preprocessing to statistical analysis to interpretation and visualization. New intracortical analysis techniques for laminar and columnar fMRI are also reviewed and discussed. Prospects for single‐subject individualized analyses are also presented and discussed. Altogether, there are both specific challenges and opportunities presented by UHF‐fMRI, and the use of proper analysis strategies can help these valuable data reach their full potential. HIGHLIGHTSUltra‐high field strengths provide increased sensitivity and specificity for fMRI.High‐resolution fMRI data enables new analysis strategies and challenges.Advanced preprocessing strategies can help preserve fMRI resolution.Small‐voxels enabled intracortical analyses for laminar and columnar fMRI.

Advantages of cortical surface reconstruction using submillimeter 7 T MEMPRAGE

ABSTRACT Recent advances in MR technology have enabled increased spatial resolution for routine functional and anatomical imaging, which has created demand for software tools that are able to process these data. The availability of high‐resolution data also raises the question of whether higher resolution leads to substantial gains in accuracy of quantitative morphometric neuroimaging procedures, in particular the cortical surface reconstruction and cortical thickness estimation. In this study we adapted the FreeSurfer cortical surface reconstruction pipeline to process structural data at native submillimeter resolution. We then quantified the differences in surface placement between meshes generated from (0.75 mm)3 isotropic resolution data acquired in 39 volunteers and the same data downsampled to the conventional 1 mm3 voxel size. We find that when processed at native resolution, cortex is estimated to be thinner in most areas, but thicker around the Cingulate and the Calcarine sulci as well as in the posterior bank of the Central sulcus. Thickness differences are driven by two kinds of effects. First, the gray–white surface is found closer to the white matter, especially in cortical areas with high myelin content, and thus low contrast, such as the Calcarine and the Central sulci, causing local increases in thickness estimates. Second, the gray–CSF surface is placed more interiorly, especially in the deep sulci, contributing to local decreases in thickness estimates. We suggest that both effects are due to reduced partial volume effects at higher spatial resolution. Submillimeter voxel sizes can therefore provide improved accuracy for measuring cortical thickness. HighlightsWe compared cortical surface reconstruction at 1 mm3 and submillimeter resolution.Reconstruction differences were assessed at every vertex on the surface.Differences in thickness estimates varied depending on the brain area.High resolution gray–white surfaces were pushed inwards in low contrast areas.High resolution gray–CSF surfaces were pushed further inward in the narrow sulci.

Perceptual effects of stimulating V5/hMT+ during binocular rivalry are state specific

Binocular rivalry occurs when two distinct visual stimuli are presented separately to each eye, causing perceptual ambiguity. The conscious state of the observer then alternates between the perceptual dominance of one of the stimuli while the other is suppressed, and vice versa. These vivid changes in perception during constant visual stimulation allow the study of brain processes involved in conscious visual experience. There is abundant electrophysiological as well as fMRI evidence that neural activity in stimulus-selective areas of the temporal lobe correlates with perceptual changes during rivalry [1–3]. Yet, almost nothing is known about the causal contribution of these areas to dominance and suppression of their preferred stimulus. We induced binocular rivalry in human observers using moving dots presented to one eye and a static face to the other eye, and applied transcranial magnetic stimulation (TMS) over the motion area V5/hMT+. We show that disrupting activity in V5/hMT+ during rivalry extends periods of motion suppression, with no effect on periods of motion dominance, revealing a state-specific contribution of V5/hMT+ to the competition for awareness in rivalry.

Scene segmentation in early visual cortex during suppression of ventral stream regions

Abstract A growing body of literature suggests that feedback modulation of early visual processing is ubiquitous and central to cortical computation. In particular stimuli with high‐level content that invariably activate ventral object responsive regions have been shown to suppress early visual cortex. This suppression was typically interpreted in the framework of predictive coding and feedback from ventral regions. Here we examined early visual modulation during perception of a bistable Gestalt illusion that has previously been shown to be mediated by dorsal parietal cortex rather than by ventral regions that were not activated. The bistable dynamic stimulus consisted of moving dots that could either be perceived as corners of a large moving cube (global Gestalt) or as distributed sets of locally moving elements. We found that perceptual binding of local moving elements into an illusory Gestalt led to spatially segregated differential modulations in both, V1 and V2: representations of illusory lines and foreground were enhanced, while inducers and background were suppressed. Furthermore, correlation analyses suggest that distinct mechanisms govern fore‐ and background modulation. Our results demonstrate that motion‐induced Gestalt perception differentially modulates early visual cortex in the absence of ventral stream activation. HighlightsWe used a bistable Gestalt illusion to examine feedback modulations in V1 and V2.The Gestalt perception has been shown to be mediated by dorsal cortex.Representations of inducers, fore‐ and back‐ground were differentially modulated.Correlation analyses suggest distinct sub‐processes underlying the modulations.Our results are in line with predictive coding accounts of visual processing.

A generic mechanism for perceptual organization in the parietal cortex.

Our visual systems ability to group visual elements into meaningful entities and to separate them from others is referred to as scene segmentation. Visual motion often provides a powerful cue for this process as parallax or coherence can inform the visual system about scene or object structure. Here we tested the hypothesis that scene segmentation by motion cues relies on a common neural substrate in the parietal cortex. We used fMRI and a set of three entirely distinct motion stimuli to examine scene segmentation in the human brain. The stimuli covered a wide range of high-level processes, including perceptual grouping, transparent motion, and depth perception. All stimuli were perceptually bistable such that percepts alternated every few seconds while the physical stimulation remained constant. The perceptual states were asymmetric, in that one reflected the default (nonsegmented) interpretation, and the other the non-default (segmented) interpretation. We confirmed behaviorally that upon stimulus presentation, the default percept was always perceived first, before perceptual alternations ensued. Imaging results showed that across all stimulus classes perceptual scene-segmentation was associated with an increase of activity in the posterior parietal cortex together with a decrease of neural signal in the early visual cortex. This pattern of activation is compatible with predictive coding models of visual perception, and suggests that parietal cortex hosts a generic mechanism for scene segmentation. SIGNIFICANCE STATEMENT Making sense of cluttered visual scenes is crucial for everyday perception. An important cue to scene segmentation is visual motion: slight movements of scene elements give away which elements belong to the foreground or background or to the same object. We used three distinct stimuli that engage visual scene segmentation mechanisms based on motion. They involved perceptual grouping, transparent motion, and depth perception. Brain activity associated with all three mechanisms converged in the same parietal region with concurrent deactivation of early visual areas. The results suggest that posterior parietal cortex is a hub involved in structuring visual scenes based on different motion cues, and that feedback modulates early cortical processing in accord with predictive coding theory.

Differential modulation of foreground and background in early visual cortex by feedback during bistable Gestalt perception

Gender differences are well established in cognition and somato-sensation, but there are almost no studies on gender differences in visual perception. One reason is that sample size is often small because effect sizes are large. Small samples are not well suited to test for gender differences. Here, we tested 887 participants from 14 to 90 years old. We tested participants in visual and vernier acuity, visual backward masking and the Wisconsin Card Sorting Test (WCST). We found no gender differences in any of the four tests for younger participants (n = 358; 14–30 years old). Even in a subgroup of schizophrenia patients (n = 260), we did not find gender differences, but large performance deficits in patients compared to controls. For middle-aged participants (n = 170; 31–59 years old), men performed significantly better than women in all perceptual tests, even when we controlled for age. We also found better performance of men compared to women in vernier duration in older participants (n = 99; 60–90 years old) and trends in the same direction for the other tests. Hence, it may be that women’s performance deteriorates with age more strongly than men’s performance. We did not find any difference in WCST, indicating no gender differences for executive functions.Although visual integration is often thought to be retinotopic, visual features can be integrated across retinotopic locations. For example, when a Vernier is followed by a sequence of flanking lines on either side, a percept of two diverging motion streams is elicited. Even though the central Vernier is invisible due to metacontrast masking, its offset is visible in the following elements. If an offset is introduced to one of the flanking lines, the two offsets combine (Otto et al., 2006). Here, by varying the number of flanking lines and the position of the flank offset, we show that this integration lasts up to 450 ms. Furthermore, this process is mandatory, i.e, observers are not able to consciously access the individual lines and change their decision. These results suggest that the contents of consciousness can be modulated by an unconscious memory-process wherein information is integrated for up to 450 ms.The ability of people with Parkinson’s (PwP) to discriminate upright and inverted facial expressions is evaluated using a temporal two-interval forced-choice paradigm. Stimuli are black and white images of neutral, happy, angry, disgusted, fearful, sad and surprised expressions. Inverted stimuli are the two expressions that participants are most and least sensitive to. A range of intensities of expressions (0–100%) are created by morphing between neutral and expressive images. The neutral image (0%) is presented in one interval and the expressive image (varies –100%) in the other. Observers indicate the interval that contained the image that was most expressive. For all upright expressions and all participants, performance increases from chance to 100% correct as intensity of expression increases. Fitted functions describing performance of happy and disgust are shifted to the left of others. This suggests that PwP are most sensitive to expressions of happiness and disgust. PwP and control participants show a small reduction in sensitivity for the expression they are most sensitive to when it is inverted (Face Inversion Effect). For PwP there is a considerable Face Inversion Effect for the expression they are least sensitive to. This suggests that configural face processing is disrupted in Parkinson’s disease.Unlike in cognition, audition and somatosensation, performance between various visual tasks does not correlate. Surprisingly, even tasks that appear similar, like visual acuity and line bisection task do not share much common variance. Similar results were found for visual illusions. For example, the Ebbinghaus and the Muller-Lyer illusions correlate very weakly. The high intra- and inter-observer variability in visual perception is possibly due to perceptual learning, i.e., individual experience shaping perception throughout one’s life time. Here, we studied the relationship between illusion strength and high-level factors such as personality traits (O-Life) and the vividness of mental imagery (VVIQ). In line with previous findings, we found only few correlations between the magnitudes of the visual illusions, despite having high test-retest reliability. More interestingly, we found a high, positive correlation between the magnitude of the Ponzo illusion and vividness of mental imagery. Moreover, the magnitude of the Ponzo illusion was negatively correlated with cognitive disorganization personality trait. These results were specific to the Ponzo-type illusions. Principal component analysis revealed one factor, with high weights mainly on the Ponzo-type illusions, cognitive disorganization and the vividness of mental imagery.Visual backward masking (VBM) is a very sensitive endophenotype of schizophrenia. Masking deficits are highly correlated with reduced EEG amplitudes. In VBM, a target stimulus is followed by a mask, which decreases performance on the target. Here, we investigated the neural correlates of VBM in relatives of schizophrenia patients. We had three conditions: target only and two VBM conditions, with long and short inter-stimulus intervals (ISI). Patients’ performance was impaired, while the relatives performed at the same level as the controls. Interestingly, EEG N1 amplitudes were higher in relatives compared to controls, while they were lower in patients relative to controls as previously reported. For relatives, N1 amplitudes were at the same level in all conditions. For controls and patients, N1 amplitudes increased with task difficult, e.g., amplitudes in the long ISI condition were lower than in short ISI condition. Our results suggest that relatives use a compensation mechanism tuning the brain to maximum performance in all conditions. Since relatives are already at the peak of their activations, increasing the task difficulty does not change brain processing.In crowding, the perception of an object deteriorates in the presence of nearby elements. Obviously, crowding is a ubiquitous phenomenon, since elements are rarely seen in isolation. Despite this ubiquity, there exists no consensus on how to model crowding. In previous experiments, it was shown that the global configuration of the entire stimulus needs to be taken into account. These findings rule out simple pooling models and favor models sensitive to global spatial aspects. In order to further investigate how to incorporate these aspects into models, we tested different types of texture segmentation models such as the Texture Tiling Model, a variation of the LAMINART neural model, a model based on Epitomes, a model based on filtering in the Fourier domain, and several classic neural network models. Across all models, simply capturing regularities in the stimulus does not suffice, as illustrated by a failure of the Fourier analysis model to explain our results. Importantly, we find that models with a grouping mechanism (such as the LAMINART model) work best. However, this grouping may be implemented in different ways, as we will show.Genetic variations of the alpha7 subunit of the nicotinergic acetylcholine receptor gene (CHRNA7) are linked to cognitive deficits in aging and schizophrenia. However, little is known about associations of the CHRNA7 gene with aged-related decline in visual perception. In the present study, we tested whether variations in the alpha7 subunit of the nicotinergic acetylcholine receptor gene (CHRNA7) interact with the perception of coherent motion in healthy aging. We assessed motion coherence for twenty-five older participants (60-73 years) and twenty-six younger participants (20–27 years) for a left/right motion direction discrimination task. A single nucleotide polymorphism (SNP) [rs2337980] of the CHRNA7 was genotyped. Overall, 25 participants were classified as T/C allele carriers (11 older), and 22 participants were classified as C/C (11 older). Only 3 participants were T/T and therefore, this group was excluded from further analysis. Overall, older adults had higher motion coherence thresholds than younger adults.We did not find any age-related associations of motion direction discrimination with the CHRNA7. However, regardless of age group, participants carrying the T/C genotype performed the task significantly better than C/C carriers. Our results therefore, indicate a strong relationship between the nicotinic system and motion perception.Reinforcement learning is a type of supervised learning, where reward is sparse and delayed. For example in chess, a series of moves is made until a sparse reward (win, loss) is issued, which makes it impossible to evaluate the value of a single move. Still, there are powerful algorithms, which can learn from delayed and sparse feedback. In order to investigate how visual reinforcement learning is determined by the structure of the RL-problem, we designed a new paradigm, in which we presented an image and asked human observers to choose an action (pushing one out of a number of buttons). The chosen action leads to the next image until observers achieve a goal image. Different learning situations are determined by the image-action matrix, which creates a so-called environment. We first tested whether humans can utilize information learned from a simple environment to solve more complex ones. Results showed no evidence supporting this hypothesis. We then tested our paradigm on several environments with different graph theoretical features, such as regular vs. irregular environments. We found that humans performed better in environments which contain less image-action pairs to the goal. We tested various RL-algorithms and found them to perform inferior to humans.The first psychotic episode is an important period for prevention of cognitive and social deterioration in schizophrenia. Cognitive deficits are of particular interest since they are evident even before a proper diagnosis can be made. Interestingly, there is a relation between cognitive deficits and social functioning. Here, we investigated the changes in cognitive and social functioning during one year and determined also the association of social functioning with cognitive impairments and psychopathological symptoms in first episode patients. 32 patients with a first psychotic episode and 32 healthy controls were investigated. Cognitive functions such as visual perception, executive functions, sustained attention, were tested with visual backward masking (VBM), the Wisconsin Card Sorting Test (WCST), and the Continuous Performance Test (CPT). Follow up tests were carried out after 6 and 12 months. Social functioning of the patients was evaluated by Health and Outcome Scale (HoNOS). Cognitive functions of patients were impaired compared to the healthy controls in all 3 tests. Performance in the cognitive tests did not change significantly during the year. Treatment compliance, however, improved social and symptom indicators.Even in the absence of neurodegenerative disease, aging strongly affects vision. Whereas optical deficits are well documented, much less is known perceptual deficits. In most perceptual studies, one paradigm is tested and it is usually found that older participants perform worse than younger participants. Implicitly, these results are taken as evidence that all visual functions of an individual decline determined by one factor, with some individuals aging more severly than others. However, this is not true. We tested 131 older participants (mean age 70 years old) and 108 younger participants (mean age 22 years old) in 14 perceptual tests (including motion perception, contrast and orientation sensitivity, biological motion perception) and in 3 cognitive tasks (WCST, verbal fluency and digit span). Young participants performed better than older participants in almost all of the tests. However, within the group of older participants, age did not predict performance, i.e., a participant could have good results in biological motion perception but poor results in orientation discrimination. It seems that there is not a single ‘‘aging’’ factor but many.39th European Conference on Visual Perception (ECVP) 2016 Barcelona LEGEND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Monday August 29th Poster presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Monday August 29th Symposia presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Monday August 29th Oral presentations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Tuesday August 30th Poster presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Tuesday August 30th Symposia presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Tuesday August 30th Oral presentations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Wednesday August 31th Poster presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Wednesday August 31th Symposia presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Wednesday August 31th Oral presentations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 Thursday September 1st Poster presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 Thursday September 1st Symposia presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 Thursday September 1st Oral presentations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 Author Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 Perception 2016, Vol. 45(S2) 1–383 ! The Author(s) 2016 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0301006616671273 pec.sagepub.comYoung adults typically display a processing advantage for the left side of space (‘‘pseudoneglect’’), whereas older adults display no strongly lateralised bias, or indeed a preference towards the right (Benwell et al., 2014; Schmitz & Peigneux, 2011). For young adults, we have recently reported that 5 commonly-used spatial attention tasks (line bisection, landmark, greyscales, gratingscales and lateralised visual detection) all provide stable intra-task measures of bias over time, however no strong inter-task correlations were found (Learmonth et al., 2015). At present there is no systematic evidence for intra- and inter-task consistency in older adults. To investigate this, we tested 22 older adults (mean age ¼ 70.44) on these five tasks, on two different days. Preliminary results show that three of the five tasks (line bisection, landmark and grayscales) seem to provide stable measures over testing sessions, indicating that they measure a consistent property of the spatial attention network. However, as per our previous finding in young adults, there seem to be no significant between-task correlations. Moreover, in contrast to the leftward biases reported in young adults, this elderly age group showed no significant lateral biases on any of the tasks.Estimates if the visual speed of human movements such as hand gestures, facial expressions and locomotion are important during social interactions because they can be used to infer mood and intention. However it is not clear how observers use retinal signals to estimate real-world movement speed. We conducted a series of experiments to investigate adaptation-induced changes in apparent human locomotion speed, to test whether the changes show repulsion of similar speeds or global re-normalisation of all apparent speeds. Participants adapted to videos of walking or running figures at various playback speeds, and then judged the apparent movement speed of subsequently presented test clips. Their task was to report whether each test clip appeared to be faster or slower than a ‘natural’ speed. After adaptation to a slow-motion or fast-forward video, psychometric functions showed that the apparent speed of all test clips changed, becoming faster or slower respectively, consistent with global re-normalisation rather than with repulsion of test speeds close to the adapting speed. The adaptation effect depended on the retinal speed of the adapting stimulus but did not require recognizably human movements.Awareness, focused attention, and task-relevance were thought to be necessary for perceptual learning (PL): a Feature of the Stimulus (FoS) on which participants perform a task is learned, while a task-irrelevant FoS is not learned. This view has been challenged by the discovery of taskirrelevant PL, occurring for subthreshold task-irrelevant stimuli presented at an unattended, peripheral location. Here, we proof further evidence for task-irrelevant PL by showing that it can occur for subthreshold task-irrelevant FoS presented in the fovea (hence spatially attended). Our experiment was divided into 3 stages: pre-test, training, and post-test. During pre- and posttests, participants performed a 3-dot Vernier task and a 3-dot bisection task. During training, participants performed an unrelated task (luminance discrimination) on the same stimulus. The task-irrelevant FoS, manipulated during training, was the position of the middle dot: either a subthreshold left/right offset (Experimental Group) or in perfect alignment with the outer dots (Control Group). The Experimental Group showed performance improvements in the Vernier task but not in the bisection task; while the Control Group showed no effect on performance in either task. We suggest that PL can occur as an effect of mere exposure to a subthreshold taskirrelevant FoS, which is spatially attended.Feature fusion reflects temporal integration. Previous studies mostly employed foveal presentations with no attention manipulation. In this study we examined the effects of sustained spatial attention on temporal integration using feature-fusion with peripheral presentation. We used a typical feature fusion display. A vernier and anti-vernier stimuli (vernier with offset in the opposite direction than the first vernier) were presented in rapid succession in one of 2 possible locations, at 2° of eccentricity. The attended condition involved endogenous attention manipulation achieved through holding the location of the stimuli constant for the whole block (i.e., the stimuli were always presented to the right of the fixation). Thus, in this condition there was no spatial uncertainty. In the unattended condition, the stimuli could appear either to the right or left of the fixation with equal probability, generating spatial uncertainty. We found considerable feature fusion in the attended condition, suggesting that feature fusion can also occur with peripheral presentation. However, no feature fusion was found without attention (i.e., when there was uncertainty regarding the stimuli location), suggesting that spatial attention improves temporal integration. We are currently conducting similar experiments using different attentional cues to manipulate transient attention.Crowding refers to the detrimental effect of nearby elements on target perception. Recently, Harrison and Bex (Curr Biol, 2015) modeled performance in a novel orientation crowding paradigm where observers reported the orientation of a Landolt C presented alone or surrounded by a flanking C. They found that crowding decreased as flanker radius increased, and their model fit these results well. A key prediction of their model is that flankers with each radius, if presented simultaneously, will additively deteriorate performance. However, evidence from other paradigms suggests that presenting several flankers can actually improve performance, if configured to group separately from the target (e.g., Manassi et al., J Vis 2012). Here, we show a similar grouping effect in the orientation crowding paradigm. We tested observers in three conditions: no flanker, one flanker, or five aligned flankers. All of our observers experienced less crowding with five aligned flankers than one flanker, and our reproduction of Harrison and Bex’s model indeed produced the opposite result. Although Harrison and Bex’s model provides a powerful framework to explain some crowding phenomena, a truly unifying model must also account for such grouping effects, as they are likely ubiquitous in everyday environments.