All ETDs from UAB

Advisory Committee Chair

Kristina M Visscher

Advisory Committee Members

Lawrence C Sincich

Miyoung Kwon

Geoffrey K Aguirre

Mark S Bolding

Document Type

Dissertation

Date of Award

2021

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

To facilitate learning throughout life, the adult brain must be capable of change, known as neuroplasticity. While evidence for adult structural plasticity in primary visual cortex (V1) exists, the relationship between plasticity and amount of use of a cortical region is not fully understood. Here, I use macular degeneration (MD) to model adult cortical plasticity. Macular degeneration causes loss of central vision, and patients learn to use a portion of peripheral vision called the preferred retinal locus (PRL) as a replacement for the fovea. The PRL is used more often than other usable areas of peripheral vision for daily tasks. How this disparity in use affects structure at the cortical representation of the PRL (cPRL) compared to comparable visual regions is not fully understood and is a focus of this thesis. How age of onset of central vision loss affects manifestation of structural plasticity at the cPRL is also of interest. To investigate potential effects of use-dependent plasticity on cortical structure, I measured differences in cortical thickness as well as neurite orientation dispersion and density between early- and late-onset MD participants and their controls at the cPRL and a control region. To reduce across-participant variance in cortical thickness and increase power to detect subtle effects, I developed a machine learning model to remove effects of 3-D geometric structure and topographical features from measurements of cortical thickness. I also developed a novel method for accurate transfer of the PRL from retinal space to cortical space to improve region of interest localization. After applying these methods, I found no significant difference in structure between the cPRL and control regions. However, I found significant decreases in neurite density and cortical thickness and a significant increase in neurite orientation dispersion in MD participants compared to controls across V1. These differences are largest in early-onset MD participants. Together, these results indicate that increased use of peripheral vision does not significantly impact cortical structure compared to other usable areas of vision, but loss of vision results in large-scale changes to structure and may have a more drastic impact on participants who lose vision earlier in life.

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