Larger Receptive Field Size as a Mechanism Underlying Atypical Motion Perception in Autism Spectrum Disorder

Abstract

Atypical visual motion perception has been widely observed in individuals with autism spectrum disorder (ASD). The pattern of results, however, has been inconsistent. Emerging mechanistic hypotheses seek to explain these variable patterns of atypical motion sensitivity, each uniquely predicting specific patterns of performance across varying stimulus conditions. Here, we investigated the integrity of two such fundamental mechanisms—response gain control and receptive field size. Twenty children and adolescents with ASD and 20 typically developing (TD) age- and IQ-matched controls performed a motion discrimination task. To adequately model group differences in both mechanisms of interest, we tested a range of 23 stimulus conditions varying in size and contrast. Results revealed a motion perception impairment in ASD that was specific to the smallest sized stimuli (1°), irrespective of stimulus contrast. Model analyses provided evidence for larger receptive field size in ASD as the mechanism that explains this size-specific reduction of motion sensitivity.

Weaker neural suppression in autism

“…To predict duration thresholds from model responses, we assumed an inverse relationship between response magnitude and duration thresholds, such that: where T is the predicted model threshold (in arbitrary units), C is the criterion response value needed to reach a perceptual judgment (i.e., left-vs. rightward motion direction) 88 , and Rpeak is the peak region of the predicted model response from Equation 1. This inverse relationship between threshold and response is consistent with previous models of motion duration thresholds 4,46,89 , and with electrophysiological data from nonhuman primates recorded in area MT during a comparable motion discrimination task 32 .…”

“…Weaker normalization in ASD would be expected to yield superior motion discrimination performance (i.e., lower duration thresholds), as previously reported 3 . Another computational model has been presented by Schauder and colleagues 4 , who suggested that larger excitatory spatial filters could account for their observation of higher motion duration thresholds among young people with ASD vs. NTs. We have recently used a divisive normalization model to describe spatial suppression across a series of experiments in NT participants 1 .…”

“…We have recently used a divisive normalization model to describe spatial suppression across a series of experiments in NT participants 1 . Here, we considered three different versions of this model, including variants based on the two models noted above 2,4 , in an attempt to describe our current observations of weaker spatial suppression in ASD within a normalization model framework.…”

“…Orange: Weaker vs. stronger normalization was modeled by lower vs. higher values for the suppressive gain term (Sg), as in previous work 2 . Magenta: Large vs. small excitatory spatial filters (SFs) were modeled using wider vs. narrower spatial Gaussians in the excitatory drive term (E), as in previous work 4 . Cyan: Narrow vs. broad top-down modulation was modeled using narrower vs. broader spatial Gaussians in the top-down modulation term (M).…”

“…These three model variants were compared for a qualitative match to the pattern of motion duration thresholds we observed in people with ASD vs. NTs (Figure 2A-C). Although other model variants have been successfully used to describe motion duration threshold data (e.g., divisive models with different contrast sensitivity for excitation and suppression 4,46 ), normalization models such as the one applied here have also proven effective 1,2 . We chose to use a normalization model here in order to directly test hypotheses presented in earlier theoretical work (e.g., the idea that ASD is associated with weaker normalization 2 ) against our current experimental data.…”