Behavioral/Cognitive A Substantial and Unexpected Enhancement of Motion Perception in Autism

Atypical perceptual processing in autism spectrum disorder (ASD) is well documented. In addition, growing evidence supports the hypothesis that an excitatory/inhibitory neurochemical imbalancemight underlie ASD. Here we investigated putative behavioral conse-quences 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 saturationof neural responses at high contrast.Motivatedby 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 ofmotion perception in ASD: children with ASD exhibited a consistent twofold improve-ment in perceiving motion. Hypothesizing that 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 groupdifferences inmotiondiscrimination thresholds. These low-contrast results, however, revealedweaker spatial suppression inASD, 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