Dissertations, Theses, and Capstone Projects

Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Psychology

Advisor

Sophie Molholm

Advisor

John J. Foxe

Subject Categories

Clinical Psychology | Developmental Psychology | Neuroscience and Neurobiology

Keywords

auditory, autism, electrophysiology, multisensory, visual

Abstract

This thesis presents three studies that together explore the neurophysiological basis for the sensory processing and integration abnormalities that have been observed in autism spectrum disorder (ASD) since the disorder was first described over half a century ago. In designing these studies we seek to fill a hole that currently exists in the research community‟s knowledge of the neurodevelopment of basic multisensory integration -- both in children with autism and as well as in those with typical development. The first study applied event related potentials (ERPs) and behavioral measures of multisensory integration to a large group of healthy participants ranging in age from 7 to 29 years, with the goal of detailing the developmental trajectory of basic audiovisual integration in the brain. Our behavioral results revealed a gradual fine-tuning of multisensory facilitation of reaction time which reached mature levels by about 14 years of age. A similarly protracted period of maturation was seen in the brain processes thought to underlie to multisensory integration. Using the results of this cross-sectional study as a guide, the second study employed a between groups design to assess differences in the neural activity and behavioral facilitation associated with integrating basic audiovisual stimuli in groups of children and adolescents with ASD and typical development (aged 7-16 years). Deficits in basic audiovisual integration were seen at the earliest stages of cortical sensory processing in the ASD groups. In the concluding study we assessed whether neurophysiological measures of sensory processing and integration predict autistic symptom severity and parent-reported visual/auditory sensitivities. The data revealed that a combination of neural indices of auditory and visual processing and integration were predictive of severity of autistic symptoms in a group of children and adolescents with ASD. A particularly robust relationship was observed between severity of autism and the integrity of basic auditory processing and audiovisual integration. In contrast, our physiological indices did not predict visual/auditory sensitivities as assessed by parent responses on a questionnaire.

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