Gemma Learmonth

No Neglect-Specific Deficits in Reaching Tasks

It is well established that patients with hemispatial neglect present with severe visuospatial impairments, but studies that have directly investigated visuomotor control have revealed diverging results, with some studies showing that neglect patients perform relatively better on such tasks. The present study compared the visuomotor performance of patients with and without neglect after right-hemisphere stroke with those of age-matched controls. Participants were asked to point either directly towards targets or halfway between two stimuli, both with and without visual feedback during movement. Although we did not find any neglect-specific impairment, both patient groups showed increased reaction times to leftward stimuli as well as decreased accuracies for open loop leftward reaches. We argue that these findings agree with the view that neglect patients code spatial parameters for action veridically. Moreover, we suggest that lesions in the right hemisphere may cause motor deficits irrespective of the presence of neglect and we performed an initial voxel-lesion symptom analysis to assess this. Lesion-symptom analysis revealed that the reported deficits did not result from damage to neglect-associated areas alone, but were further associated with lesions to crucial nodes in the visuomotor control network (the basal ganglia as well as occipito-parietal and frontal areas).

Age-related reduction of hemispheric lateralisation for spatial attention: An EEG study

Abstract A group‐level visuospatial attention bias towards the left side of space (pseudoneglect) is consistently observed in young adults, which is likely to be a consequence of right parieto‐occipital dominance for spatial attention. Conversely, healthy older adults demonstrate a rightward shift of this behavioural bias, hinting that an age‐related reduction of lateralised neural activity may occur within visuospatial attention networks. We compared young (aged 18–25) and older (aged 60–80) adults on a computerised line bisection (landmark) task whilst recording event‐related potentials (ERPs). Full‐scalp cluster mass permutation tests identified a larger right parieto‐occipital response for long lines compared to short in young adults (confirming Benwell et al., 2014a) which was not present in the older group. To specifically investigate age‐related differences in hemispheric lateralisation, cluster mass permutation tests were then performed on a lateralised EEG dataset (RH‐LH electrodes). A period of right lateralisation was identified in response to long lines in young adults, which was not present for short lines. No lateralised clusters were present for either long or short lines in older adults. Additionally, a reduced P300 component amplitude was observed for older adults relative to young. We therefore report here, for the first time, an age‐related and stimulus‐driven reduction of right hemispheric control of spatial attention in older adults. Future studies will need to determine whether this is representative of the normal aging process or an early indicator of neurodegeneration. HighlightsNeural correlates of the landmark task compared in young vs older adults using EEG.Small leftward behavioral bias (pseudoneglect) at baseline for long lines in young.Right‐lateralised cluster of early EEG activity identified for long lines in young.No lateralised activity for either line length in older adults.Age‐related reduction of P300 component amplitude.

Long Term Improvements in Activities of Daily Living in Patients with Hemispatial Neglect

Monika Harvey, Keith Muir, Ian Reeves, George Duncan, Philip Birschel, Margaret Roberts, Katrina Livingstone, Hazel Jackson, Caroline Hogg , Pauline Castle , Gemma Learmonth and Stephanie Rossit School of Psychology, University of Glasgow, Glasgow, UK Institute of Neurological Sciences, Southern General Hospital, Glasgow, UK Department of Medicine for the Elderly, Southern General Hospital, Glasgow, UK Stroke Discharge and Rehabilitation Team, Southern General Hospital, Glasgow, UK Stroke Unit, Southern General Hospital, Glasgow, UK Mansion House Unit, Glasgow, UK Victoria Infirmary, Glasgow, UK Department of Psychology, University of Western Ontario, London, Canada

Efficacy of home-based visuomotor feedback training in stroke patients with chronic hemispatial neglect

ABSTRACT Hemispatial neglect is a severe cognitive condition frequently observed after a stroke, associated with unawareness of one side of space, disability and poor long-term outcome. Visuomotor feedback training (VFT) is a neglect rehabilitation technique that involves a simple, inexpensive and feasible training of grasping-to-lift rods at the centre. We compared the immediate and long-term effects of VFT vs. a control training when delivered in a home-based setting. Twenty participants were randomly allocated to an intervention (who received VFT) or a control group (n = 10 each). Training was delivered for two sessions by an experimenter and then patients self-administered it for 10 sessions over two weeks. Outcome measures included the Behavioural Inattention Test (BIT), line bisection, Balloons Test, Landmark task, room description task, subjective straight-ahead pointing task and the Stroke Impact Scale. The measures were obtained before, immediately after the training sessions and after four-months post-training. Significantly greater short and long-term improvements were obtained after VFT when compared to control training in line bisection, BIT and spatial bias in cancellation. VFT also produced improvements on activities of daily living. We conclude that VFT is a feasible, effective, home-based rehabilitation method for neglect patients that warrants further investigation with well-designed randomised controlled trials on a large sample of patients.

Correction: Intra- and Inter-Task Reliability of Spatial Attention Measures in Pseudoneglect

[This corrects the article DOI: 10.1371/journal.pone.0138379.].

Right-Lateralised Lane Keeping in Young and Older British Drivers

Young adults demonstrate a small, but consistent, asymmetry of spatial attention favouring the left side of space (“pseudoneglect”) in laboratory-based tests of perception. Conversely, in more naturalistic environments, behavioural errors towards the right side of space are often observed. In the older population, spatial attention asymmetries are generally diminished, or even reversed to favour the right side of space, but much of this evidence has been gained from lab-based and/or psychophysical testing. In this study we assessed whether spatial biases can be elicited during a simulated driving task, and secondly whether these biases also shift with age, in line with standard lab-based measures. Data from 77 right-handed adults with full UK driving licences (i.e. prior experience of left-lane driving) were analysed: 38 young (mean age = 21.53) and 39 older adults (mean age = 70.38). Each participant undertook 3 tests of visuospatial attention: the landmark task, line bisection task, and a simulated lane-keeping task. We found leftward biases in young adults for the landmark and line bisection tasks, indicative of pseudoneglect, and a mean lane position towards the right of centre. In young adults the leftward landmark task biases were negatively correlated with rightward lane-keeping biases, hinting that a common property of the spatial attention networks may have influenced both tasks. As predicted, older adults showed no group-level spatial asymmetry on the landmark nor the line bisection task, but they maintained a mean rightward lane position, similar to young adults. The 3 tasks were not inter-correlated in the older group. These results suggest that spatial biases in older adults may be elicited more effectively in experiments involving complex behaviour rather than abstract, lab-based measures. More broadly, these results confirm that lateral biases of spatial attention are linked to driving behaviour, and this could prove informative in the development of future vehicle safety and driving technology.

No interaction between tDCS current strength and baseline performance: a conceptual replication

Several recent studies have reported non-linear effects of transcranial direct current stimulation (tDCS), which has been attributed to an interaction between the stimulation parameters (e.g., current strength, duration) and the neural state of the cortex being stimulated (e.g., indexed by baseline performance ability, age) (see Fertonani and Miniussi, 2016). We have recently described one such non-linear interaction between current strength and baseline performance on a visuospatial attention (landmark) task (Benwell et al., 2015). In this previous study, we induced a small overall rightward shift of spatial attention across 38 participants using bi-hemispheric tDCS applied for 20 min (concurrent left posterior parietal (P5) anode and right posterior parietal (P6) cathode) relative to a sham protocol. Importantly, this shift in bias was driven by a state-dependent interaction between current intensity and the discrimination sensitivity of the participant at baseline (pre-stimulation) for the landmark task. Individuals with high discrimination sensitivity (HDS) shifted rightward in response to low- (1 mA) but not high-intensity (2 mA) tDCS, whereas individuals with low discrimination sensitivity (LDS) shifted rightward with high- but not low-intensity stimulation. However, in Benwell et al. (2015) current strength was applied as a between-groups factor, where half of the participants received 1 mA and half received 2 mA tDCS, thus we were unable to compare high and low-intensity tDCS directly within each individual. Here we aimed to replicate these findings using a within-group design. Thirty young adults received 15 min of 1 and 2 mA tDCS, and a sham protocol, each on different days, to test the concept of an interaction between baseline performance and current strength. We found no overall rightward shift of spatial attention with either current strength, and no interaction between performance and current strength. These results provide further evidence of low replicability of non-invasive brain stimulation protocols, and the need for further attempts to replicate the key experimental findings within this field.

Spatial Attention Measures in Healthy Aging

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.

The EEG correlates of stimulus-induced spatial attention shifts in healthy aging

Adaptation to videos of human locomotion (videos recorded from the London Marathon) affects observers’ subsequent perception of human locomotion speed: normal speed test stimuli are perceived as being played in slow-motion after adaptation to fast-forward stimuli and conversely, are perceived as being played in fast-forward after adaptation to slow-motion stimuli. In this study we investigated whether the presence of recognisable human motion in the adapting stimulus is necessary for the effect. The adapting stimuli were spatially scrambled: horizontal pixel rows were randomly shuffled. The same shuffled order was used for all frames preserving horizontal motion information, but ensuring no human form could be recognised. Results showed that the after-effect persisted despite spatially scrambling the adapting stimuli; human motion is not a necessary requirement for the locomotion after-effect. The after-effect seems to be driven by adaptation in relatively low-level visual channels rather than the high-level processes that encode human motion.Perception is usually non-retinotopic. For example, a reflector on the wheel of a bicycle is perceived to rotate on a circular orbit, while its retinotopic motion is cycloidal. To investigate non-retinotopic motion perception, we used the Ternus-Pikler display. Two disks are repeatedly flashed on a computer screen. A dot moves linearly up-down in the left disk and left-right in the right disk (retinotopic percept). If a third disk is added alternatingly to the left and right, the three disks form a group moving predictably back and forth horizontally. The dot in the central disk now appears to move on a circular orbit (non-retinotopic percept), because the brain subtracts the horizontal group motion from the up-down and left-right motion. Here, we show that predictability is not necessary to compute non-retinotopic motion. In experiment 1, the three disks moved randomly in any direction. In experiment 2, we additionally varied the shape and contrast polarity of the stimuli from frame to frame. In both cases, strong non-retinotopic rotation was perceived. Hence, the visual system can flexibly solve the non-retinotopic motion correspondence problem, even when the retinotopic reference motion is unpredictable and no efference copy-like signals can be used.In Object Substitution Masking (OSM) a mask surrounding, simultaneously onsetting with, and trailing a target leads to a reduction in target perceptibility (Di Lollo et al., 2000). It has been questioned whether this process is due to target substitution or the addition of noise to the percept (Podor, 2012). Two experiments examined this issue using an adjustment task in which a test Landolt C is presented and participants rotate it to match the target Landolt C shown during the trial (typical OSM paradigms use 2-4 alternative forced choice); the dependent measure was the angle of error. In Experiment 1 the effect of a trailing OSM mask (80ms-320ms) is compared against that of adding stimulus noise of varying densities (25%-75%) to the target location. Both manipulations (OSM, stimulus noise) produced a similar change in the distribution of errors compared against a baseline (0ms trailing mask, 0%-noise). The pattern is consistent with both mask manipulations reducing the fidelity of the target percept. In Experiment 2 the OSM and stimulus noise manipulations were varied factorially. Here the two manipulations had combinatorial effects on the error distribution. Implications are discussed regarding the mechanisms of OSM and the consequences of OSM for target perceptionDistributed representations (DR) of cortical channels are pervasive in models of spatio-temporal vision. A central idea that underpins current innovations of DR stems from the extension of 1-D phase into 2-D images. Neurophysiological evidence, however, provides tenuous support for a quadrature representation in the visual cortex, since even phase visual units are associated with broader orientation tuning than odd phase visual units (J.Neurophys.,88,455–463, 2002). We demonstrate that the application of the steering theorems to a 2-D definition of phase afforded by the Riesz Transform (IEEE Trans. Sig. Proc., 49, 3136–3144), to include a Scale Transform, allows one to smoothly interpolate across 2-D phase and pass from circularly symmetric to orientation tuned visual units, and from more narrowly tuned odd symmetric units to even ones. Steering across 2-D phase and scale can be orthogonalized via a linearizing transformation. Using the tiltafter effect as an example, we argue that effects of visual adaptation can be better explained by via an orthogonal rather than channel specific representation of visual units. This is because of the ability to explicitly account for isotropic and cross-orientation adaptation effect from the orthogonal representation from which both direct and indirect tilt after-effects can be explained.claims surround the effects of colour on performance. Elliot, Maier, Moller, Friedman and Meinhardt (2007) proposed that in an achievement context (e.g. maths test) the perception of red impedes performance by inducing avoidance motivation. However, replications of the effect are scant, especially in the UK and some suffer from a lack of stimulus colour control. We report five experiments that attempt to replicate the red-effect in an achievement context across a range of settings: online; in school classrooms; and in the laboratory. In each experiment, stimuli were carefully specified and calibrated to ensure that they varied in hue but not luminance or saturation. Only one experiment replicated the red effect – participants who were primed with a red stimulus (relative to white) for 5 s scored worse on a subsequent verbal task. However, replication and extension of this experiment failed to reproduce the effect. Explanations for the findings are discussed including: the effect is not present in a UK population; the effect requires very specific methodology; the effect does not generalise to applied settings; and/or the original body of work overestimates the prevalence of these effects. PhD research funded by studentship provided by the University of Surrey Psychology Faculty.This poster was presented at 38th European Conference on Visual Perception (ECVP) 2015 Liverpool, abstract published in Perception on 21 August 2015Dynamic stimuli capture attention, even if not in the focus of endogenous attention. Such a stimulus is apparent motion, given that it benefits perception of targets in the motion path. These benefits have been attributed to motion-induced ‘entrainment’ of attention to expected locations (spatial extrapolation) and/or expected time-points (temporal entrainment). Here, we studied the automatic nature of spatial extrapolation versus temporal entrainment with apparent motion stimuli, when motion was task-irrelevant. Participants performed an endogenously cued target detection task, in which symbolic cues prompted attention shifts to lateralized target positons (75% validity). Simultaneously, apparent motion cues flickered either rhythmically or arhythmically across the screen, such that targets appeared either in or out of motion trajectory. Although the motion cue can be considered a distractor (non-informative as to target location), motion direction influenced target detection, which is in line with automatic extrapolation of spatial positions during apparent motion. An effect that was independent and additive to the endogenous cueing benefit. Importantly, temporal cueing in the motion stream also influenced target detection. However, this effect was independent of reflexive motion-cueing to spatial positions. We conclude that spatial extrapolation and temporal entrainment of attention by apparent motion are governed by partially independent reflexive mechanisms.How do interpersonal behavioural dynamics predict individual and joint decisions? Recent interactionist views on social cognition suggest that the most under-studied and important aspect of social cognition may be interaction dynamics. However, it has hitherto proven extremely difficult to devise a controlled setup in which social cues, such as eye gaze, are subject to unconstrained interaction. To address these issues, we use a dual interactive eye-tracking paradigm. Participants are presented with the face of an anthropomorphic avatar, the eye movements of which are linked in real-time to another participant’s eye-gaze. This allows for control of interaction aspects that are not related to the experience of gaze contingency. Participants have to choose which one out of two spheres on either side of the avatar face is the largest. These spheres can have a medium, small, and no difference. Specifically in the latter condition, gaze dynamics guide choices. Using cross-recurrence quantification, we analyse the time course of the gaze interactions and look at how this predicts individual and joint decisions about sphere size, which participant will follow the other, and assess collaboration in a subsequent “stag hunt” game, a variation on the prisoner’s dilemma game.We report a new after-effect of visual motion in which the apparent speed of human locomotion is affected by prior exposure to speeded-up or slowed-down motion. In each trial participants were shown short video clips of running human figures (recorded from the London Marathon) and asked to report whether the speed of movement was ‘slower than natural’ or ‘faster than natural’, by pressing one of two response buttons. The clips were displayed at different playback speeds ranging from slow-motion (0.48x natural speed) to fast-forward (1.44x natural speed). Adaptation to stimuli played at normal speed resulted in the P50 of the psychometric function falling close to normal-speed playback. However after adaptation to 1.44x playback, normal-speed playback appeared too slow, so the P50 shifted significantly towards a higher playback speed; after adaptation to 0.48xplayback, normal-speed playback appeared too fast, so the P50 shifted significantly towards a lower playback speed. The shifts in apparent speed were obtained using both same- and opposite-direction adaptation-test stimulus pairs, indicating that the effect is a speed adaptation effect rather than a directional velocity after-effect. These findings are consistent with norm-based coding of the speed of movement.Young adults typically display a processing advantage for the left side of space (‘‘pseudoneglect’’) but older adults display either no strongly lateralised bias or a preference towards the right (Benwell et al., 2014; Schmitz & Peigneux, 2011). We have previously reported an additive rightward shift in the spatial attention vector with decreasing landmark task line length and increasing age (Benwell et al., 2014). However there is very little neuroimaging evidence to show how this change is represented at a neural level. We tested 20 young (18–25) and 20 older (60–80) adults on long vs short landmark lines whilst recording activity using EEG. The peak ‘‘line length effect’’ (long vs short lines) was localised to the right parieto-occipital cortex (PO4) 137 ms post-stimulus. Importantly, older adults showed additional involvement of left frontal regions (AF3: 386 ms & F7: 387 ms) for short lines only, which may represent the neural correlate of this rightward shift. These behavioural results align with the HAROLD model of aging (Cabeza, 2002) where brain activity becomes distributed across both hemispheres in older adults to support successful performance.We studied the effect of age on visual perceptual decisions of bi-stable stimuli. We used two different stimuli: bi-stable rotating spheres and a binocular rivalry stimulus. At onset, both stimuli can evoke two different percepts: for the sphere clockwise or anti-clockwise rotation and for the binocular rivalry stimulus a percept that switches between the stimuli in the two eyes. The stimuli were presented intermittently for 1 second with a range of inter-stimulus intervals (0.1 – 2 seconds). Subjects ranged between 18 and 73 years old and were instructed to indicate which of the two percepts dominate at each onset of the bi-stable stimulus. Our results show that perceptual choices are more stable for older subjects for the binocular rivalry stimulus and not for the bi-stable rotating spheres. The results will be discussed in the context of current models for bi-stable visual perception.The visual system combines spatial signals from the two eyes to achieve single vision. But if binocular disparity is too large, this perceptual fusion gives way to diplopia. We studied and modelled the processes underlying fusion and the transition to diplopia. The likely basis for fusion is linear summation of inputs onto binocular cortical cells. Previous studies of perceived position, contrast matching and contrast discrimination imply the computation of a dynamicallyweighted sum, where the weights vary with relative contrast. For gratings, perceived contrast was almost constant across all disparities, and this can be modelled by allowing the ocular weights to increase with disparity (Zhou, Georgeson & Hess, 2014). However, when a single Gaussian-blurred edge was shown to each eye perceived blur was invariant with disparity (Georgeson & Wallis, ECVP 2012) – not consistent with linear summation (which predicts that perceived blur increases with disparity). This blur constancy is consistent with a multiplicative form of combination (the contrast-weighted geometric mean) but that is hard to reconcile with the evidence favouring linear combination. We describe a 2-stage spatial filtering model with linear binocular combination and suggest that nonlinear output transduction (eg. ‘half-squaring’) at each stage may account for the blur constancy.

P267: The effects of bilateral transcranial direct current stimulation over posterior parietal cortices on visuospatial attention bias

P265 – Figure 2. Cortical excitability modulation induced by customized electrode in dependence on current intensity. P266 Investigating the effect of current flow on cortical excitability using bipolar tDCS V. Rawji1, M. Ciocca1,2, A. Zacharia1,3, J. Rothwell1 1UCL Institute of Neurology, Sobell Department of Motor Neuroscience and Movement Disorders, London, United Kingdom; 2University of Milan, Centro di Neurostimolazione e Disordini del Movimento UOD Neurofisiopatologia, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milano, Italy; 3Hôpitaux universitaire de Genève, Neucli, Geneva, United Kingdom Question: High-Definition transcranial Direct Current Stimulation (HDtDCS) has been proposed as a new non-invasive neuromodulatory technique that uses small electrodes placed in a 4×1 configuration to localise the electrical field to a targeted area [1,2]. Neurophysiological effects are thought to depend on the intensity and polarity used, as with classic tDCS [3]. No clear studies have been published on the possible contribution of current flow direction to the final effect. In 11 subjects, we explore whether the orientation of the current flow, parallel or perpendicular to the FDI hotspot, has differential effects on motor cortex (M1) excitability. Methods: TMS intensity was adjusted to produce MEPs of approximately 1mV peak-to-peak amplitude. Twenty MEPs from the FDI were collected at each time point (Baseline, 0, 10, 20, 30, 40 minutes after stimulation), with the TMS coil oriented perpendicular to the central sulcus. HD-tDCS (Neuroelectrics, Spain; 1mA, 10min) was delivered via circular sponge electrodes (area 3.14cm2), each placed 3.5cm from the FDI hotspot. Two were positioned parallel to the TMS coil to induce posterior-anterior current across the hotspot (PA). Two were perpendicular to the coil (PP stimulation) to induce a mediolateral current. The protocol involved 3 different sessions: (1) stimulation with AP tDCS, (2) stimulation with PP tDCS, (3) sham stimulation. Results: PA tDCS significantly reduced the M1 excitability compared to PP and sham stimulation. PP stimulation showed no significant change in motor cortex excitability compared to sham. Conclusions: These results suggest that a current flow oriented parallel, but not perpendicular to TMS over M1 hand is able to change corticospinal excitability. Further investigations are needed to elucidate the physiological mechanisms of HD-tDCS. References: [1] Dmochowski, P. Et al. (2011). Optimized multi-electrode stimulation increases focality and intensity at target, J. Neural Eng., 8. [2] Kuo, H.I. Et al. (2012). Comparing cortical plasticity induced by conventional and high-definition 4×1 ring tDCS: a neurophysiological study. Brain Stimulation. [3] Nitsche, M.A. Et al. (2008) Transcranial direct current stimulation stimulation: State of the art 2008. Brain Stimulation. P267 The effects of bilateral transcranial direct current stimulation over posterior parietal cortices on visuospatial attention bias C. Benwell, G. Learmonth, M. Harvey, G. Thut University of Glasgow, Institute of Neuroscience & Psychology, Glasgow,