Balasubramanian Dissertation Abstract

EEG During Motor Task in Stroke: The Effects of Ischemic Conditioning and Fatigue on Brain Activity 

Dissertation Date:  December 22, 2021

The purpose of this dissertation was to use electroencephalography (EEG) to identify the
effects of fatigue and 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 due to 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 fingertap task between the 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. Ischemic conditioning, 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.



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