A Substantial and Unexpected Enhancement of Motion Perception in Autism

Abstract

Atypical perceptual processing in autism spectrum disorders (ASD) is well documented. Additionally, growing evidence supports the hypothesis that an excitatory/inhibitory neurochemical imbalance might underlie ASD. Here, we investigated putative behavioral consequences of the excitatory/inhibitory imbalance in the context of visual motion perception. As stimulus size increases, typical observers exhibit marked impairments in perceiving motion of high-contrast stimuli. This result, termed spatial suppression, is believed to reflect inhibitory motion processing mechanisms. Motion processing is also affected by gain control—an inhibitory mechanism that underlies saturation of neural responses at high contrast. Motivated by these behavioral correlates of inhibitory function, we investigated motion perception in human children with ASD (N=20) and typical development (N=26). At high contrast, both groups exhibited similar impairments in motion perception with increasing stimulus size, revealing no apparent differences in spatial suppression. However, there was a substantial enhancement of motion perception in ASD: children with ASD exhibited a consistent two-fold improvement in perceiving motion. Hypothesizing this enhancement might indicate abnormal weakening of response gain control, we repeated our measurements at low contrast, where the effects of gain control should be negligible. At low contrast, we indeed found no group differences in motion discrimination thresholds. These low-contrast results, however, revealed weaker spatial suppression in ASD, suggesting the possibility that gain control abnormalities in ASD might have masked spatial suppression differences at high contrast. Overall, we report a pattern of motion perception abnormalities in ASD that includes substantial enhancements at high contrast and is consistent with an underlying excitatory/inhibitory imbalance.

Measuring neural excitation and inhibition in autism: Different approaches, different findings and different interpretations

“…In contrast to the conclusion made by Foss-Feig et al (2013), evidence from perceptual discrimination may suggest increased inhibition in ASD. For example, as described below, superior orientation discrimination and superior pitch discrimination have been reported in ASD, both of which are associated with increased inhibitory neurotransmission.…”

“…The phenomenon relies on centre surround suppression, meaning that decreased inhibition would lead to weaker spatial suppression, and a reduced effect of increasing stimulus size on perception (Golomb et al, 2009). Foss-Feig et al (2013 investigated spatial suppression in individuals with and without ASD using a motion discrimination paradigm in which participants were asked to indicate the direction of drifting gratings that varied in size and contrast.…”

Attentional and sensory contributions to postural sway in children with autism spectrum disorder

“…This finding is consistent with earlier studies [8,23], and suggests that individuals with ASD have greater reliance on visual input for the regulation of balance, making it more difficult to maintain balance with the eyes closed. A recent study [28] revealed unexpected and substantial superiority in visual motion perception in children with ASD, compared to controls. Relatedly, a review [29] found that individuals with ASD consistently outperform controls on visual search tasks; possibly mediated by 'over-focused attention'.…”

A computational perspective on autism

“…3D), may be altered in autism (40,41). In one study, Foss-Feig et al (40) presented drifting gratings that varied in size and contrast, and had subjects indicate the direction of motion (left vs. right).…”