All ETDs from UAB

Advisory Committee Chair

David C Knight

Advisory Committee Members

Merida Grant

Rajesh Kana

Miyoung Kwon

Cynthia Owsley

Kristina Visscher

Document Type

Dissertation

Date of Award

2021

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

The human brain is shaped by a dynamic interplay between innate factors and life experiences. Neuroscience has long grappled with understanding this relationship, particularly with regard to how changes in experience impact the brain during adulthood. This question is especially important in the context of macular degeneration, a disease that causes significant visual impairment and drastically alters day-to-day visual experiences for individuals afflicted by the disease. Specifically, people with macular degeneration lose the ability to use vision in the center of the visual field, the region of the retina with the highest spatial resolution. Subsequently, these individuals must rely on the much lower resolution of peripheral vision for everyday visual tasks. Understanding how the brain adapts to this change in visual experience is of crucial importance for helping restore the function of vision in individuals with macular degeneration. As a result, numerous studies have explored how visual processing in the brain changes after central vision loss in macular degeneration. One particularly prominent question is how the loss of central vision alters the connectivity of visual cortex to meet these new demands. While some studies have explored this question, they have been limited by a lack individual specificity when identifying regions in the brain that may be the targets for plasticityiii related changes in macular degeneration. Additionally, these studies have only examined functional connectivity stemming from single regions of visual cortex and have failed to account for connectivity at the network-level in visual cortex. Furthermore, these studies have not examined how functional connectivity is modulated across different types of conditions. The following dissertation seeks to resolve these issues by performing a characterization of functional connectivity in macular degeneration patients that considers individualized regional connections, network level connections, and the modulation of these connections across conditions. For regional connections, we find that macular degeneration patients have stronger functional connectivity between peripheral representations in early visual cortex and regions involved in motion processing. For network-level connections, we find that overall patterns of functional connectivity appear to be very similar between macular degeneration patients and healthy controls. Finally, for connectivity across conditions, we find that while functional connectivity changes between conditions, these changes seem to be the same in individuals with macular degeneration and people with healthy vision. These findings demonstrate that while some connections in visual cortex appear to be plastic following the loss of central vision, many patterns appear to remain unchanged. These results suggest that there are much more nuanced patterns of altered functional connectivity in macular degeneration and not necessarily broad sweeping changes across all visual cortex. On the whole, these results point to the sophisticated organization of visual cortex and serves as yet another example of experience-dependent plasticity in the human visual system.

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