Purpose of the study: Successful integration of signals from the various sensory systems is crucial for normal sensory-perceptual functioning, allowing for perception of coherent objects rather than a disconnected cluster of fragmented features. Several prominent theories of autism suggest that automatic integration is impaired in this population, but there have been very few empirical tests of this thesis.
Method: A well-characterized electrophysiological metric of multisensory integration was used to test the integrity of auditory-somatosensory integration in children with autism (N=13, aged 6 to 14), compared to age and IQ matched typically developing children. High-density electrophysiology was recorded while participants were randomly presented with either auditory or somatosensory stimuli alone (i.e. unisensory presentations), or as a combined auditory-somatosensory stimulus. Participants watched a silent movie during testing, ignoring the concurrent stimulation. Significant differences between neural responses to the multisensory auditory-somatosensory stimulus and the unisensory stimuli (the sum of the responses to the auditory and somatosensory stimuli when presented alone) served as the dependent measure of multisensory integration.
Results: These data indicate group differences in the integration of auditory and somatosensory information that appear relatively early in sensory processing, and are characterized by the presence of MSI for the TD but not the ASD children. Specifically, MSI was seen starting at about 100 ms in the control group, but only emerged starting at about 250 ms in the ASD group. In contrast, there were no group differences in the early sensory processing of the auditory and somatosensory stimuli when presented alone, demonstrating typical processing of the unisensory stimuli.
Discussion: These findings are discussed within the framework of current knowledge of multisensory integration in typical development as well as in relation to theories of ASD.