All ETDs from UAB

Advisory Committee Chair

Rajesh K Kana

Advisory Committee Members

Sylvie Mrug

Sarah O'Kelley

Lawrence Ver Hoef

Kristina Visscher

Document Type

Dissertation

Date of Award

2020

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and restricted and repetitive behaviors and interests. One of the most consistent findings in ASD is reduced attention to and atypical processing of faces. However, the brain basis of aberrant face processing in ASD remains opaque. A novel neuroanatomical feature, the mid-fusiform sulcus (MFS), is strongly associated with face-selective regions of the fusiform gyrus (FG) as well as other large-scale functional and structural divisions in the ventral temporal cortex (Weiner et al., 2014). However, this feature is unexplored in ASD. The overarching goal of this dissertation is to characterize the structure of the MFS and determine its relationship to face-selective visual processing regions and social functioning in ASD. We used structural magnetic resonance imaging and surface-based morphometry to explore MFS surface-based patterns, gray matter volume, surface area, and cortical thickness in two large samples of children and adults with ASD. Additionally, we used Activation Likelihood Estimation (ALE) meta-analysis to determine the location of significant activation and activation differences during face processing in ASD. We found that the MFS is reliably identifiable in ASD and presents with similar macroanatomical surface patterns as in typical development (TD). However, MFS morphometry is altered. Specifically, individuals with ASD have significantly less MFS gray matter volume compared to their TD counterparts. MFS gray matter reductions appear driven by reduced surface area, but not reduced cortical thickness, specific to the left hemisphere in ASD. While TD individuals displayed a leftward expansion of MFS surface area, this pattern was absent in ASD. Reductions in MFS gray matter volume correlated with more severe ASD symptoms and poorer real-world social functioning across groups. Quantitative meta-analysis revealed face-processing regions located laterally to the MFS in ASD and TD; however, only a single region in the left FG was activated consistently in response to faces in ASD while TD activated a wider network of core and extended face-processing regions. This work represents the first study of the MFS in ASD and provides a foundation for future investigation of structure-function relationships in this important social brain region.

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