Examining the Neurological Underpinnings of Atypical Multisensory Perception in Autism Spectrum Disorders
Lavoie, Stephanie Lindsey-Marie
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Individuals with Autism Spectrum Disorders (ASD) have been found to have difficulties with multisensory perception, which would have a significant impact on their cognitive, sensory, language, and social development. The current collection of studies sought to understand the neurological mechanisms underlying this difficulty with multisensory perception across temporal synchrony variations using functional Magnetic Resonance Imaging (fMRI). The nature of these multisensory processing deficits were further explored by delineating social and linguistic processing. The overall goal was accomplished by examining multisensory processing in three studies. The first study evaluated and compared various methods of identifying brain regions responsible for multisensory integration in 17 young adults without ASD. This first study found that a newly proposed temporal synchrony method, which compares neural responses to temporally synchronous and asynchronous audiovisual stimuli, was more theoretically valid and more empirically tenable than other previously used methods. In the second study, the temporal synchrony method was used to compare responses to multisensory stimuli across social-linguistic, social-nonlinguistic, and nonsocial-nonlinguistic conditions in individuals with (n = 15) and without (n = 17) ASD using fMRI. The third study explored whole-brain patterns of activity involved in multisensory integration, using a multivariate fMRI analysis approach (partial least squares: PLS) with the same participant groups as study two. Taken together the results of studies two and three reveal that young adults with ASD do not process multisensory stimuli in the same way as young adults without ASD. When using targeted contrasts in study two, individuals with ASD displayed either a lack of multisensory integration or an opposite pattern of response to synchrony variants of multisensory information relative to the group without ASD. Further, the results of study three suggested that when examining synchronous and asynchronous multisensory stimuli, individuals with ASD do not engage the same social- and language-specific networks that were present in individuals without ASD. Based on the results of these studies, a novel hypothesis was proposed to explain the differential response profiles for individuals with and without ASD: the multisensory catalyst nodes hypothesis.