Electrophysiological Assessment of Visual Function in Autism Spectrum Disorders

The human visual system is characterized by a set of parallel, hierarchical multistage systems that are specialized to process different types of visual stimuli. There are two major parallel streams: the parvocellular (or ventral) and magnocellular (or dorsal) pathways. The former projects to the inferior temporal cortex for object and color vision, whereas the latter connects to the parietal cortex for motion and spatial vision. Individuals with autism spectrum disorder (ASD) often show inferior global motion perception but superior performance in detailed form (local structure) perception. These unique behaviors suggest the possibility of an impairment of the parallel visual pathways in ASD. Visual evoked potentials (VEPs) and event-related potentials (ERPs) are non-invasive electrophysiological methods that provide objective information about the function of the visual system. We have recently developed VEPs and ERPs with visual stimuli designed to preferentially stimulate the different levels of each visual pathway. In this review, we introduce the application of VEP and ERP techniques for the assessment of visual perception in ASD. Current data indicate that the atypical visual perception observed in ASD may be caused by the dysfunction of complicated brain networks within the parallel visual pathways, and may contribute to the impaired social communication involved in ASD. Therefore, we conclude that electrophysiological techniques are useful for understanding the pathophysiology of ASD.