Psychophysiological Indicators of Multisensory Processing in Autism Spectrum Disorder and Typical Development: A Pupillometry Study
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Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social communication and interactions (APA, 2013). Pupillary responses are a reliable indicator of cognitive operations including preference, mental load, and emotional arousal. The current study utilized pupillary responses to dynamic, audio-visual stimuli to infer cognitive processes involved in perception of social and non-social stimuli, as well as to temporally manipulated (i.e., asynchronous auditory and visual presentations) stimuli. The current study had four main research objectives: 1) to characterize pupillary responses to social and non-social information in ASD and typical development (TD), 2) to characterize responses to asynchronous and synchronous audio-visual stimuli in ASD and TD, 3) to determine whether pupillary responses can accurately predict membership to the ASD or TD group, and 4) to understand the relationship between pupillary responses and measures of ASD symptoms and social factors. Chronological and mental age-matched participants included 39 children with ASD and 32 typically developing children. Pupillary responses to social (Social-Linguistic, Social Non-Linguistic, and Social-Emotional) and non-social (Non-Social, Non-Linguistic) conditions were captured and recorded using an eye-tracker. Results yielded several key findings indicating differences between groups: 1) individuals with ASD demonstrated an attenuated pupillary response to social information, but not to non-social information, 2) in ASD, a reduction in pupillary response to social information was associated with greater impairments in social abilities and sensory processing as rated by caregivers, and 3) pupillary responses to social information was used to reliably predict group membership for children with ASD. Finally, this study did not observe between group differences in temporal processing, rather, both groups showed greater pupillary response to audio-leading asynchronous conditions, except for social-emotional conditions in which there was a significantly greater response to synchronous presentations. Results are discussed within the context of the engagement/arousal hypothesis of pupil dilation and the social motivation theory of ASD. Results are interpreted as evidence that reduced orienting to and under-engagement with social stimuli are implicated in the social impairments observed in ASD. This study demonstrates the usefulness and feasibility of pupillary response as a possible identification tool of the atypical social processing observed in ASD.