Date of Award
Spring 2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biomedical Engineering
First Advisor
Schmit, Brian D.
Second Advisor
Hyngstrom, Allison S.
Third Advisor
Beardsley, Scott A.
Abstract
This dissertation aimed to use electroencephalography (EEG) to identify the effects of fatigue and remote ischemic conditioning on brain activity. Lesions due to stroke directly or indirectly affect regions of the brain and the descending corticospinal pathways. Cortical reorganization and alternate descending neural pathways are used during recovery from stroke as compensation mechanisms for motor deficits. These mechanisms exacerbate the deficits by worsening the ability to terminate muscle activity, individuate muscles for fine motor control and minimize abnormal muscle synergy and coactivation patterns to conserve resources during movement. Even though imaging and muscle activation studies have documented the existence and impact of cortical reorganization and the use of alternate descending pathways, temporal changes in cortical activation during long motor tasks are not well understood. We expect that potential changes in cerebrovascular function and physiology of brain metabolism after stroke might impact the ability of the brain to produce extended activity. We used EEG for its high temporal resolution compared to other imaging modalities to document temporal changes in brain activity when people with stroke performed various motor tasks. We first documented the changes in activation during and at the end of a simple cued finger tap task between people with stroke and controls. We then pushed the neuromuscular system to its limits using a fatiguing contraction of the wrist to visualize changes in brain activation patterns after extended muscle contraction. Lastly, we tested a neurorehabilitation therapy protocol, remote ischemic conditioning (RIC), that has shown functional improvements in people with stroke to determine if cortical activation is changed during a complex, multijoint visuomotor task. The results show that cortical activation in people with stroke is divergent from controls. People with stroke continue brain activation at the end of a simple task but cannot increase activation at the end of a fatiguing task. RIC, however, increases activation during a multijoint elbow/shoulder task. This research has improved our understanding of brain activation during a simple task and in response to fatigue in people with stroke. The knowledge of cortical changes due to RIC demonstrates the therapy’s ability to “prime” the brain for neurorehabilitation, which might lead to better therapeutic outcomes post-rehabilitation in people with stroke.