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Advisory Committee Chair

Edward Taub

Advisory Committee Members

Gitendra Uswatte

Rosalyn Weller

Victor W Mark

Rajesh Kana

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Changes in afferent input have been associated with structural and functional changes to brain tissue. Increased use through an intense neurorehabilitation treatment such as CI therapy has been shown to result in increased grey matter in sensorimotor cortex, more anterior motor areas, and hippocampus. In contrast, decreased use of an arm after stroke results in a contraction of the cortical representation zone involved in its movement. The chronic effects of ischemia and subsequent prolonged nonuse of an extremity on the structure of stroke-affected brains was unknown prior to this investigation, however. This study employed voxel-based morphometry, an MRI analysis technique, to gauge grey matter volume following a period of prolonged nonuse of the impaired arm in chronic stroke patients. Interhemispheric differences in remaining, healthy grey matter tissue was examined in 80 chronic stroke patients with mild/moderate motor deficit. The more affected hemisphere and contralesional anterior lobe of the cerebellum had significantly less grey matter than the healthier hemisphere and ipsilesional cerebellum. Some of this difference may be accounted for by physiological changes in the affected hemisphere produced by the initial ischemic event. However, there was a correlation between measures of severity of motor deficit and relative amount of grey matter in the ipsilateral cerebellum and contralateral hand-knob area of M1, raising the possibility that nonuse of the impaired arm may contribute to relative atrophy of some brain structures in the more affected hemisphere. Furthermore, greater interhemispheric grey matter volume difference of the hand knob area of M1 and hippocampus were associated with less improvement in amount and quality of arm use from CI therapy, indicating that recovery of function is influenced by the condition of apparently healthy tissue at a distance from the lesion locus. This finding begins to explain a central enigma in our understanding of how stroke produces its motor symptomatology.

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