Adaptation and serial choice bias for low-level visual features are unaltered in autistic adolescents.

Autism spectrum disorder (ASD), or autism, is characterized by social and non-social symptoms, including sensory hyper- and hyposensitivities. A suggestion has been put forward that some of these symptoms could be explained by differences in how sensory information is integrated with its context, including a lower tendency to leverage the past in the processing of new perceptual input. At least two history-dependent effects of opposite directions have been described in the visual perception literature: a repulsive adaptation effect, where perception of a stimulus is biased away from an adaptor stimulus, and an attractive serial choice bias, where perceptual choices are biased toward the previous choice. In this study, we investigated whether autistic participants differed in either bias from typically developing controls (TDs). Sixty-four adolescent participants (31 with ASD, 33 TDs) were asked to categorize oriented line stimuli in two tasks that were designed so that we would induce either adaptation or serial choice bias. Although our tasks successfully induced both biases, in comparing the two groups we found no differences in the magnitude of adaptation nor in the modulation of perceptual choices by the previous choice. In conclusion, we find no evidence of a decreased integration of the past in visual perception of low-level stimulus features in autistic adolescents.

No evidence for altered up- and downregulation of brain activity in visual cortex during illusory shape perception in autism.

Autism spectrum disorder (ASD) may be marked by an altered balance between sensory input and prior expectations. Because many illusions rely on integrating sensory input with prior information such as spatial context, individuals with ASD may therefore be less susceptible to visual illusions than typically developing (TD) individuals. Yet empirical evidence on the matter is rather divergent, varying depending on the type of illusion, study procedure, and population. Visual illusions lead to neural activity alterations in the visual system. In the so-called Kanizsa illusion, these are likely caused by top-down feedback to V1. Here we tested the hypothesis that a reduced susceptibility to illusions in ASD would manifest as diminished modulation of V1 activity by illusions, using functional magnetic resonance imaging (fMRI). We presented 22 adolescents with ASD and 22 age-, gender-, and intelligence-matched TD controls with displays that consisted of three circular inducers. These either formed an illusory triangle (Kanizsa illusion) or not. We identified regions in primary visual cortex (V1) that corresponded to (the visual field locations of) the illusory triangle and its inducers, and recorded their visual response. Previous research in healthy volunteers has shown a specific pattern of up- and down-regulation in regions of V1 that process the shape and inducers, respectively. Here, we replicated this pattern of up- and downregulation in V1, in both the TD and ASD groups, with no differences between groups. This suggests that illusory shape processing in primary visual cortex is equally present in ASD, suggesting unimpaired processing of spatial context.

Adolescents with autism show typical fMRI repetition suppression, but atypical surprise response.

Recent theoretical frameworks have hypothesized that autism spectrum disorder (ASD) may be marked by an altered balance between sensory inputs and prior knowledge-the so-called hypoprior hypothesis. Yet evidence regarding such an altered balance is mixed. Here, we aimed to test this hypothesis within the domain of visual perception, by examining how neural activity in the visual system was modulated by stimulus repetition and stimulus expectation in healthy and ASD participants. We presented 22 adolescents with ASD and 22 typically developing (TD) adolescents with pairs of object stimuli, while measuring brain activity using functional magnetic resonance imaging (fMRI). Stimulus pairs could be stimulus repetitions or not and could be expected or not. We examined neural activity in early (V1) and object-selective (LOC) visual cortex. Both ASD and TD individuals showed robust and equal repetition suppression in LOC. By contrast, ASD and TD groups showed a different response to expected versus unexpected stimuli, specifically in V1. Thereby, our results suggest that while the more automatic modulation of activity by repetition is unaffected in ASD, there is some evidence that the balance between sensory evidence and prior knowledge may indeed be altered in early visual cortex of ASD.

Repetition suppression to objects is modulated by stimulus-specific expectations.

Repeated exposure to the same stimulus results in an attenuated brain response in cortical regions that are activated during the processing of that stimulus. This phenomenon, called repetition suppression (RS), has been shown to be modulated by expectation. Typically, this is achieved by varying the probability of stimulus repetitions (Prep) between blocks of an experiment, generating an abstract expectation that 'things will repeat'. Here, we examined whether stimulus-specific expectations also modulate RS. We designed a task where expectation and repetition are manipulated independently, using stimulus-specific expectations. We investigated to which extent such stimulus-specific expectations modulated the visual evoked response to objects in lateral occipital cortex (LOC) and primary visual cortex (V1), using functional magnetic resonance imaging (fMRI). In LOC, we found that RS interacted with expectation, such that repetition suppression was more pronounced for unexpected relative to expected stimuli. Additionally, we found that the response of stimulus-preferring voxels in V1 was generally decreased when stimuli were expected. These results suggest that stimulus-specific expectations about objects modulate LOC and propagate back to the earliest cortical station processing visual input.

Shaping Science for Increasing Interdependence and Specialization.

Like art, science affords an individualistic career. However, increasingly, complexity necessitates increased interdependency and specialization. Despite this change, many institutions, funding agencies, and publishers insist on an exclusively individualistic model of science. This hinders scientific progress by imposing a range of inefficiencies in the planning and execution of research plans.

Expectation Suppression in Early Visual Cortex Depends on Task Set.

Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response. However, it is unclear whether this expectation suppression is an automatic phenomenon or is instead dependent on the type of task a subject is engaged in. To investigate this, human subjects were presented with visual grating stimuli in the periphery that were either predictable or non-predictable while they performed three tasks that differently engaged cognitive resources. In two of the tasks, the predictable stimulus was task-irrelevant and spatial attention was engaged at fixation, with a high load on either perceptual or working memory resources. In the third task, the predictable stimulus was task-relevant, and therefore spatially attended. We observed that expectation suppression is dependent on the cognitive resources engaged by a subjects' current task. When the grating was task-irrelevant, expectation suppression for predictable items was visible in retinotopically specific areas of early visual cortex (V1-V3) during the perceptual task, but it was abolished when working memory was loaded. When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex. These results suggest that expectation suppression is not an automatic phenomenon, but dependent on attentional state and type of available cognitive resources.

Lateralized power spectra of the EEG as an index of visuospatial attention.

The electroencephalogram (EEG) was measured in an endogenous orienting paradigm where symbolic cues indicated the likely side of to-be-discriminated targets. Combined results of event-related lateralizations (ERLs) and a newly derived measure from wavelet analyses that we applied on the raw EEG and individual event-related potentials (ERPs), the lateralized power spectra (LPS) and the LPS-ERP, respectively, confirmed the common view that endogenous orienting operates by anterior processes, probably originating from the frontal eye fields, modulating processing in parietal and occipital areas. The LPS data indicated that modulation takes place by increased inhibition of the irrelevant visual field and/or disinhibition of the relevant to-be-attended visual field. Combined use of ERLs, the LPS, and the LPS-ERP indicated that most of the involved processes can be characterized as externally evoked, either or not with clear individual differences as some evoked effects were only visible in the LPS-ERERP, whereas few processes seemed to have an internally induced nature. Use of the LPS and the LPS-ERP may be advantageous as it enables to determine the involvement of internally generated lateralized processes that are not strictly bound to an event like stimulus onset.