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Abstract

As our aging population grows and the prevalence of stroke continues to rise, the number of individuals who experience chronic functional deficits of the upper limb will increase. Current methods of tracking impairment are subjective, and lack of accessibility and cost leaves a gap in who can benefit. Non-invasive neural biomarkers have been proposed as a means of quantitatively assessing motor function, with the ultimate goal of incorporating objective, measures of brain health into clinical care. Electroencephalography (EEG) is ideally suited to address these challenges. Yet there remains a gap in our knowledge of how these measures change during movements of different effectors. The purpose of this dissertation was to explore EEG-based biomarkers of upper limb movement, in healthy individuals and individuals with chronic stroke. Three experiments were designed to investigate alpha and beta task-related power during continuous movements of proximal and distal upper limb effectors: Experiment 1 focused on uncovering the spatial pattern and the time-course of power during continuous movements in young, healthy individuals. Two complimentary analyses of event-related and task-related power revealed similar results, namely a reduction of contralateral dominance in proximal versus distal movements. These findings support previous evidence suggesting an enhanced role of ipsilateral descending pathways in proximal movement. In Experiment 2, I explored whether this relationship was impacted by age. Overall, I saw the same ipsilateral involvement in proximal movements, but this was accompanied by more parietal involvement in older adults, possibly indicative of greater proprioceptive demands. Finally, in Experiment 3, I aimed to determine whether the above findings would be observed in individuals with chronic stroke, and whether this was associated with motor behaviour. Here, I discovered altered patterns of alpha activity were most prominent during proximal movements and importantly, task-related power was correlated with behavioural measures of motor impairment and dexterity. Taken together, these results highlight the importance of widespread regions outside of the primary motor areas in aging and after stroke, as well as the role of the ipsilateral cortex in the execution of proximal, versus distal movements. These results add novel insights to further inform biomarker development in these populations.