Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Theses & dissertations (Interdisciplinary)

First Advisor

Eric Cooper

Second Advisor

Elizabeth Stegemöller

Abstract

The goal of this study was to examine how dopamine (DA) and dopaminergic medications affect the performance of high-level visual tasks in individuals with Parkinson’s disease (PD). Various studies have reported that PD is associated with impairments on visual tasks known to depend on processing in the ventral visual pathway of the brain. Because most behavioral symptoms in PD arise from chronic dopamine deficiency, the author sought to investigate the role that DA played in cognitive vision. Accordingly, five complex visual tasks were chosen that were known to recruit processing from different constellations of brain areas, either in the ventral pathway or to which the ventral pathway was known to send projections. The tasks included discrimination of abstract objects and three-dimensional face stimuli, visual working memory for these same stimuli, and mental rotation of three-dimensional wire-frame objects. An additional task, in which participants were required to discriminate between pairs of lines with varying orientations, was included as a control. Individuals with PD, as well as healthy age- and sex-matched control participants, completed all five of these tasks twice, and individuals with PD, in particular, were asked to complete them once on and once off of their prescribed dopaminergic medications.

The PD group performed significantly worse than the group of healthy control participants across all five tasks. Strikingly, the performance of individuals in the PD group did not differ significantly depending on their medication state. This finding indicates either that dopamine deficiency is not responsible for cognitive visual impairments in PD, or that the dopaminergic circuitry responsible for these impairments is incapable of responding to the administration of dopaminergic medication. Further, since all tasks, including the line orientation discrimination task, showed an effect of group, the results of this study are insufficient to rule out the possibility that impairments that have been reported elsewhere as cognitive visual deficits in PD are simply the result of deficits in more basic visual processing. Finally, the results of this study provide preliminary evidence that impairments of mental rotation in PD are the result of impaired processing in brain regions traditionally associated with motor functioning.

Copyright Owner

StephenJonAnderson

Language

en

File Format

application/pdf

File Size

126 pages

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