Date of Award
Doctor of Philosophy (PhD)
Strokes can affect very different behavioral domains causing deficits in language, memory, visual attention and movement. This range of deficits is caused by stroke lesions that occur in different locations, and it reflects both the local structural damage as well as remote and widespread neurophysiological abnormalities of structurally normal regions of the brain. The recovery of behavioral deficits depends both on psychosocial factors like age and education, whose brain substrates are presently poorly defined, structural variables such as lesion size and location, and neurobiological repair mechanisms both locally near the lesion and network-wide.
In the current work we hypothesized that behavioral recovery can be divided in two classes: ‘domain-general’ that influence recovery of deficits across multiple domains of function; and, ‘domain-specific’ that differ in different functions. At the neurobiological level, we test the hypothesis that domain-specific normalization of abnormal patterns of synchronization occurring across multiple networks at the acute stage represents one of the major neurophysiological correlates of behavioral recovery. Specifically, I will focus on the recovery of attention deficits post-stroke, as seen in the syndrome of hemispatial neglect.
Recovery of neurological deficits reaches a maximum by 3 months post-stroke, and then plateaus in a similar manner across domains without reaching normal performance. The best predictor of chronic performance in each domain of function is the severity of initial deficit that relates proportionally to the amount of recovery (domain-general). However, specific variables such as education level and lesion location differentially improve the prediction of recovery in specific domains (domain-specific). Domain general components likely reflect mechanisms of spontaneous recovery that are activated after a stroke, whereas the domain-specific factors may include those related to compensatory strategies.
Independent of initial severity, the improvement of acutely depressed inter-hemispheric functional connectivity or synchrony across attention, sensory, and motor networks, and a restoration of the normally negative (anti-) correlation between dorsal attention/motor regions and default-mode/frontoparietal regions, robustly predicts recovery of attention deficits post-stroke. These findings are consistent with a normalization of neurophysiological patterns in relationship to behavioral recovery, and a tendency of damaged brain networks to return to normal levels of integration/segregation, which are optimal for information processing.
Chair and Committee
Bradley L. Schlaggar, Joshua S. Shimony, Jin-Moo Lee, Catherine E. Lang
Ramsey, Lenny Eveline, "Behavioral and Neurophysiological Mechanisms of Recovery Post-Stroke" (2016). Arts & Sciences Electronic Theses and Dissertations. 886.