Graduation Date

Fall 12-18-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Medical Sciences Interdepartmental Area

First Advisor

Max J. Kurz

Second Advisor

Tony W. Wilson

Third Advisor

David E. Warren

Fourth Advisor

Anastasia Kyvelidou

Abstract

Cerebral palsy (CP) is a permanent, non-progressive neuromuscular disorder diagnosed early in childhood. Frequently the lesion that causes the motor impairments in individuals with CP concurrently disrupts the visual networks, placing them at a high risk of cerebral visual dysfunctions. Cerebral visual impairment (CVI) often remains unrecognized or misdiagnosed in people with CP. Despite the crucial role of visual function in the development of movement and cognition, the neurophysiological basis of the cerebral visual dysfunctions is almost entirely unknown. This investigation aimed to examine the neurophysiological mechanisms underlying cerebral visual dysfunction in children with CP. Specifically, this research used magnetoencephalographic brain imaging techniques to evaluate the cortical processing of visual motion, spatial contrast, and spatial attention. The first study identified aberrant oscillatory activity in the motion-sensitive MT/V5 cortex, while participants viewed horizontal movement. These visual processing deficits were linked with delayed motor responses and errors in perceptual judgments. The outcomes of this study suggest that the uncharacteristic neural oscillations in the visual MT/V5 cortical area may partially account for the abnormal perceptions and motor decisions seen in children with CP. The second study targeted the processing of basic perception, independent of visual motion, by using a high-contrast spatial-grating known to elicit gamma oscillations and associated with visual acuity. This study found that children with CP have deficits in the frequency-specific occipital oscillations involved in the processing of contrast. The third study probed the cortical oscillations serving visuospatial attention, arguably the most prevalent cerebral visual dysfunction reported in children with CP. The outcomes from this study showed blunted neural responses serving visual-spatial processing and related the visual dysfunction to performance errors during a visual-spatial discrimination task.

These studies collectively provide neurophysiological evidence for the prominent cerebral visual processing deficiencies in children with CP. Linking these aberrations with perceptual-motor impairments transforms our perception of how small differences in visual processing affect the motor functions of children with CP. Identifying these specific deficiencies in the neurophysiological mechanisms underlying CVI in children with CP should prompt clinicians in new directions for targeted therapeutic interventions.

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