Evaluation of Atypical Human Action Sound Processing As an Early Biomarker for Autism

Background: Previous behavioural and neuroimaging studies have revealed reduced attention to social orienting cues, such as eye-gaze and pointing gestures, as well as atypical visual perceptual processing of biological motion and human actions in children with autism spectrum disorders.

Objectives:   Examine human versus non-human action sound processing as a putative biomarker for autism in young children diagnosed with autism without intellectual disability, high-risk toddler siblings of children with autism, and toddlers diagnosed with autism with intellectual disability.

Methods: Human and non-human action sounds were presented using a Rapid Auditory Mismatch event-related potentials (ERPs) procedure.  The autism without intellectual disability group and high-risk toddler group were each matched with a group of typically developing children/toddlers who were matched for gender, chronological age, and verbal ability.  The autism with intellectual disability group was matched with a typically developing toddler control group matched for gender and chronological age.

Results: Children with autism without intellectual disability exhibited atypical processing of non-human action sounds at an early cognitive stage of processing, as well as reduced habituation to human action sounds at a later stage of processing, both over posterior parietal cortex.  High-risk toddlers also exhibited atypical processing of non-human action sounds at an early cognitive stage over posterior parietal cortex.  However, toddlers with autism with intellectual disability exhibited reduced right frontal activity specifically in response to human action sounds, with no apparent atypicalities in either human or non-human action sound processing over posterior parietal cortex.

Conclusions: The current findings indicate that atypicalities in human action sound processing are present in individuals with autism both with and without intellectual disability.  However, these atypicalities were differentially expressed as reduced habituation over parietal cortex in individuals without intellectual disability versus reduced activation over right frontal cortex in the individuals with intellectual disability.  These findings suggest that the nature of neurobiological markers for core impairments in social processing may differ across levels of intellectual disability in this population.