Intact perceptual bias in autism contradicts the decreased normalization model

Temporal dynamics of normalization reweighting

For decades, neural suppression in early visual cortex has been thought to be fixed. But recent work has challenged this assumption by showing that suppression can be reweighted based on recent history; when pairs of stimuli are repeatedly presented together, suppression between them strengthens. Here we investigate the temporal dynamics of this process using a steady-state visual evoked potential (SSVEP) paradigm that provides a time-resolved, direct index of suppression between pairs of stimuli flickering at different frequencies (5 and 7 Hz). Our initial analysis of an existing electroencephalography (EEG) dataset (N = 100) indicated that suppression increases substantially during the first 2-5 seconds of stimulus presentation (with some variation across stimulation frequency). We then collected new EEG data (N = 100) replicating this finding for both monocular and dichoptic mask arrangements in a preregistered study designed to measure reweighting. A third experiment (N = 20) used source-localized magnetoencephalography and found that these effects are apparent in primary visual cortex (V1), consistent with results from neurophysiological work. Because long-standing theories propose inhibition/excitation differences in autism, we also compared reweighting between individuals with high versus low autistic traits, and with and without an autism diagnosis, across our three datasets (total N = 220). We find no compelling differences in reweighting that are associated with autism. Our results support the normalization reweighting model and indicate that for prolonged stimulation, increases in suppression occur on the order of 2-5 seconds after stimulus onset.

A theory of autism bridging across levels of description

Autism impacts a wide range of behaviors and neural functions. As such, theories of autism spectrum disorder (ASD) are numerous and span different levels of description, from neurocognitive to molecular. We propose how existent behavioral, computational, algorithmic, and neural accounts of ASD may relate to one another. Specifically, we argue that ASD may be cast as a disorder of causal inference (computational level). This computation relies on marginalization, which is thought to be subserved by divisive normalization (algorithmic level). In turn, divisive normalization may be impaired by excitatory-to-inhibitory imbalances (neural implementation level). We also discuss ASD within similar frameworks, those of predictive coding and circular inference. Together, we hope to motivate work unifying the different accounts of ASD.

Neural correlates of hierarchical predictive processes in autistic adults

Bayesian theories of autism spectrum disorders (ASD) suggest that atypical predictive mechanisms could underlie the autistic symptomatology, but little is known about their neural correlates. Twenty-six neurotypical (NT) and 26 autistic adults participated in an fMRI study where they performed an associative learning task in a volatile environment. By inverting a model of perceptual inference, we characterized the neural correlates of hierarchically structured predictions and prediction errors in ASD. Behaviorally, the predictive abilities of autistic adults were intact. Neurally, predictions were encoded hierarchically in both NT and ASD participants and biased their percepts. High-level predictions were following activity levels in a set of regions more closely in ASD than NT. Prediction errors yielded activation in shared regions in NT and ASD, but group differences were found in the anterior cingulate cortex and putamen. This study sheds light on the neural specificities of ASD that might underlie atypical predictive processing.

Enhanced rationality in autism spectrum disorder

Challenges in social cognition and communication are core characteristics of autism spectrum disorder (ASD), but in some domains, individuals with ASD may display typical abilities and even outperform their neurotypical counterparts. These enhanced abilities are notable in the domains of reasoning, judgment and decision-making, in which individuals with ASD often show 'enhanced rationality' by exhibiting more rational and bias-free decision-making than do neurotypical individuals. We review evidence for enhanced rationality in ASD, how it relates to theoretical frameworks of information processing in ASD, its implications for basic research about human irrationality, and what it may mean for the ASD community.

Prior information use and response caution in perceptual decision-making: No evidence for a relationship with autistic-like traits

Interpreting the world around us requires integrating incoming sensory signals with prior information. Autistic individuals have been proposed to rely less on prior information and make more cautious responses than non-autistic individuals. Here, we investigated whether these purported features of autistic perception vary as a function of autistic-like traits in the general population. We used a diffusion model framework, whereby decisions are modelled as noisy evidence accumulation processes towards one of two bounds. Within this framework, prior information can bias the starting point of the evidence accumulation process. Our pre-registered hypotheses were that higher autistic-like traits would relate to reduced starting point bias caused by prior information and increased response caution (wider boundary separation). 222 participants discriminated the direction of coherent motion stimuli as quickly and accurately as possible. Stimuli were preceded with a neutral cue (square) or a directional cue (arrow). 80% of the directional cues validly predicted the upcoming motion direction. We modelled accuracy and response time data using a hierarchical Bayesian model in which starting point varied with cue condition. We found no evidence for our hypotheses, with starting point bias and response caution seemingly unrelated to Adult Autism Spectrum Quotient (AQ) scores. Alongside future research applying this paradigm to autistic individuals, our findings will help refine theories regarding the role of prior information and altered decision-making strategies in autistic perception. Our study also has implications for models of bias in perceptual decision-making, as the most plausible model was one that incorporated bias in both decision-making and sensory processing.

Structural and contextual priors affect visual search in children with and without autism

Bayesian predictive coding theories of autism spectrum disorder propose that impaired acquisition or a broader shape of prior probability distributions lies at the core of the condition. However, we still know very little about how probability distributions are learned and encoded by children, let alone children with autism. Here, we take advantage of a recently developed distribution learning paradigm to characterize how children with and without autism acquire information about probability distributions. Twenty-four autistic and 25-matched neurotypical children searched for an odd-one-out target among a set of distractor lines with orientations sampled from a Gaussian distribution repeated across multiple trials to allow for learning of the parameters (mean and variance) of the distribution. We could measure the width (variance) of the participant's encoded distribution by introducing a target-distractor role-reversal while varying the similarity between target and previous distractor mean. Both groups performed similarly on the visual search task and learned the distractor distribution to a similar extent. However, the variance learned was much broader than the one presented, consistent with less informative priors in children irrespective of autism diagnosis. These findings have important implications for Bayesian accounts of perception throughout development, and Bayesian accounts of autism specifically. LAY SUMMARY: Recent theories about the underlying cognitive mechanisms of autism propose that the way autistic individuals estimate variability or uncertainty in their perceptual environment may differ from how typical individuals do so. Children had to search an oddly tilted line in a set of lines pointing in different directions, and based on their response times we examined how they learned about the variability in a set of objects. We found that autistic children learn variability as well as typical children, but both groups learn with less precision than typical adults do on the same task.

Prediction in Autism Spectrum Disorder: A Systematic Review of Empirical Evidence

According to a recent influential proposal, several phenotypic features of autism spectrum disorder (ASD) may be accounted for by differences in predictive skills between individuals with ASD and neurotypical individuals. In this systematic review, we describe results from 47 studies that have empirically tested this hypothesis. We assess the results based on two observable aspects of prediction: learning a pairing between an antecedent and a consequence and responding to an antecedent in a predictive manner. Taken together, these studies suggest distinct differences in both predictive learning and predictive response. Studies documenting differences in learning predictive pairings indicate challenges in detecting such relationships especially when predictive features of an antecedent have low salience or consistency, and studies showing differences in habituation and perceptual adaptation suggest low-level predictive processing differences in ASD. These challenges may account for the observed differences in the influence of predictive priors, in spontaneous predictive movement or gaze, and in social prediction. An important goal for future research will be to better define and constrain the broad domain-general hypothesis by testing multiple types of prediction within the same individuals. Additional promising avenues include studying prediction within naturalistic contexts and assessing the effect of prediction-based intervention on supporting functional outcomes for individuals with ASD. LAY SUMMARY: Researchers have suggested that many features of autism spectrum disorder (ASD) may be explained by differences in the prediction skills of people with ASD. We review results from 47 studies. These studies suggest that ASD may be associated with differences in the learning of predictive pairings (e.g., learning cause and effect) and in low-level predictive processing in the brain (e.g., processing repeated sounds). These findings lay the groundwork for research that can improve our understanding of ASD and inform interventions. Autism Res 2021, 14: 604-630. © 2021 International Society for Autism Research and Wiley Periodicals LLC.

Perceptual category learning in autism spectrum disorder: Truth and consequences

The ability to categorize is fundamental to cognitive development. Some categories emerge effortlessly and rapidly while others can take years of experience to acquire. Children with autism spectrum disorder (ASD) are often able to name and sort objects, suggesting that their categorization abilities are largely intact. However, recent experimental work shows that the categories formed by individuals with ASD may diverge substantially from those that most people learn. This review considers how atypical perceptual category learning can affect cognitive development in children with ASD and how atypical categorization may contribute to many of the socially problematic symptoms associated with this disorder. Theoretical approaches to understanding perceptual processing and category learning at both the behavioral and neural levels are assessed in relation to known alterations in perceptual category learning associated with ASD. Mismatches between the ways in which children learn to organize perceived events relative to their peers and adults can accumulate over time, leading to difficulties in communication, social interactions, academic performance, and behavioral flexibility.

Collinear facilitation and contour integration in autistic adults: Examining lateral and feedback connectivity

Alongside difficulties with communication and social interaction, autism is often accompanied by unusual sensory and perceptual experiences including enhanced visual performance on tasks that involve separating local parts from global context. This superiority may be the result of atypical integrative processing, involving feedback and lateral connections between visual neurons. The current study investigated the integrity of these connections in autistic adults by examining two psychophysics tasks that rely on these processes - collinear facilitation and contour integration. The relative contribution of feedback and lateral connectivity was studied by altering the timing of the target relative to the flankers in the collinear facilitation task, in 16 autistic and 16 non-autistic adults. There were no significant differences in facilitation between the autistic and non-autistic groups, indicating that for this task and participant sample, lateral and feedback connectivity appear relatively intact in autistic individuals. Contour integration was examined in a different group of 20 autistic and 18 non-autistic individuals, for open and closed contours to assess the closure effect (improved detection of closed compared to open contours). Autistic individuals showed a reduced closure effect at both short (150 ms) and longer (500 ms) stimulus presentation durations that was driven by better performance of the autistic group for the open contours. These results suggest that reduced closure in a simple contour detection paradigm is unlikely to be due to slower global processing. Reduced closure has implications for understanding sensory overload by contributing to reduced figure-ground segregation of salient visual features.

Sensitivity and specificity of a Bayesian single trial analysis for time varying neural signals

We recently reported the existence of fluctuations in neural signals that may permit neurons to code multiple simultaneous stimuli sequentially across time [1]. This required deploying a novel statistical approach to permit investigation of neural activity at the scale of individual trials. Here we present tests using synthetic data to assess the sensitivity and specificity of this analysis. We fabricated datasets to match each of several potential response patterns derived from single-stimulus response distributions. In particular, we simulated dual stimulus trial spike counts that reflected fluctuating mixtures of the single stimulus spike counts, stable intermediate averages, single stimulus winner-take-all, or response distributions that were outside the range defined by the single stimulus responses (such as summation or suppression). We then assessed how well the analysis recovered the correct response pattern as a function of the number of simulated trials and the difference between the simulated responses to each "stimulus" alone. We found excellent recovery of the mixture, intermediate, and outside categories (>97% correct), and good recovery of the single/winner-take-all category (>90% correct) when the number of trials was >20 and the single-stimulus response rates were 50Hz and 20Hz respectively. Both larger numbers of trials and greater separation between the single stimulus firing rates improved categorization accuracy. These results provide a benchmark, and guidelines for data collection, for use of this method to investigate coding of multiple items at the individual-trial time scale.

Preserved low-level visual gain control in autistic adults

Background: No sensory stimulus is an island entire of itself, the processing of visual inputs is highly influenced by surrounding spatial context. Some accounts of Autism Spectrum Disorder have suggested that the sensory difficulties reported in the condition could arise from differences in contextual modulation of sensory stimuli, specifically problems with gain control mechanisms that regulate incoming sensory information as a function of sensory context. Methods: Here we examined the spatial modulation of visual processing in autistic and neurotypical adults by assessing surround suppression for two low-level visual features: orientation and luminance. We used an established psychophysical task with known neurocomputational correlates and interrogated group differences in suppression magnitude.   Results: We found that the magnitude of surround suppression for both visual features was equivalent in autistic adults and matched neurotypical controls. Additionally, there was no relationship between suppression magnitude and autism symptom severity. Conclusion: These results suggest that for low level visual features, the spatial gain control mechanisms regulating sensory input are preserved. These findings have important theoretical implications for establishing the types of gain control mechanisms that are compromised in autism, and the extent to which there are differences in contextual processing.

Typical perceptual organization in autism: Perceptual grouping and spatial distortion

The extensive literature on global-local processing in people with autism spectrum disorder (ASD) has recently shifted from arguing for a processing impairment among those with ASD to positing an attenuated preference for global processing. One suggestion is that the fast extraction of the global gist is less efficient in ASD, in contrast to the superior attention-driven processing of local elements. To examine this claim of attenuated global processing, the present study tested how perceptual grouping affected the global organization of visual scenes, specifically testing the claim of less mandatory, more optional global processing in ASD. Participants judged the distance between grouped and ungrouped elements in displays in which illusory distortions were inherent in configurations exemplifying the Gestalt principles of organization. Results from six experiments manipulating different Gestalt cues showed a consistent pattern, indicating that for individuals with ASD, as for typically developed (TD) individuals, grouping processes are organizational in nature, incorporating the grouping of related elements while parsing these from other unrelated elements. This parsing is accompanied by distortions in the spatial relationships perceived in the visual scene. ASD participants exhibited an overall larger tendency to overestimate the distances, but they also demonstrated typical perceptual organization processes that were robust and mandatory and, as in neurotypicals, affected the perception of the whole scene. Autism Res 2019. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: It is known that individuals with autism spectrum disorder (ASD) perceive the world in a different way than their typically developed (TD) peers. While TD individuals exhibit strong bias toward processing the global structure of visual scenes, individuals with ASD exhibit enhanced perception of the local elements. We showed that when the local and global levels are not competing, individuals with autism demonstrate robust global organization that operates even when not directly instructed.