Successful integration of auditory and visual inputs is crucial for both basic perceptual functions and for higher-order processes related to social cognition. Autism spectrum disorders (ASD) are characterized by impairments in social cognition and are associated with abnormalities in sensory and perceptual processes. Several groups have reported that individuals with ASD are impaired in their ability to integrate socially relevant audiovisual (AV) information, and it has been suggested that this contributes to the higher-order social and cognitive deficits observed in ASD. However, successful integration of auditory and visual inputs also influences detection and perception of nonsocial stimuli, and integration deficits may impair earlier stages of information processing, with cascading downstream effects. To assess the integrity of basic AV integration, we recorded high-density electrophysiology from a cohort of high-functioning children with ASD (7–16 years) while they performed a simple AV reaction time task. Children with ASD showed considerably less behavioral facilitation to multisensory inputs, deficits that were paralleled by less effective neural integration. Evidence for processing differences relative to typically developing children was seen as early as 100 ms poststimulation, and topographic analysis suggested that children with ASD relied on different cortical networks during this early multisensory processing stage.
Findings from the current study provide evidence that children with ASD integrate even very basic, nonsocial AV stimuli differently and less effectively than children with TD. Neural indices of MSI indicate that children with ASD rely on different cortical regions at a relatively early stage of information processing, as shown by topographical analysis (Fig. 6d). These findings strongly point to a general deficit in AV integration that is independent of social or high-order cognitive deficits. While it is unlikely that impairments in basic MSI, such as those demonstrated here, can account for the entire constellation of symptoms observed in ASD, both could result from common underlying differences in connectivity and it is not difficult to see how disruptions in fundamental integration of basic sensory information might contribute to social and communicative deficits characteristic of individuals with ASD. For example, suboptimal integration of AV inputs may make it more difficult for young children to benefit from the redundant visual-articulatory information that supports language learning independent of any biases compromising the processing of “social” stimuli. Atypical connections between sensory cortices and more anterior and integrative brain areas may disrupt the formation of meaningful relationships between congruent auditory and visual inputs. That said, it is possible that more ecologically valid stimuli and/or a more challenging task than the one employed here might bring out “work-around” strategies in the children with autism that allow them to compensate for these early impairments in automatic multisensory processing. Though highly speculative, it may be that for important functions such as speech recognition, compensatory processes involving frontal lobe development (e.g., improvements in executive function) contribute to the “catching up” observed in some behavioral studies of AV integration in ASD over childhood