UBC Theses and Dissertations
The neurophysiology of sensorimotor integration in healthy aging and chronic stroke Brown, Katlyn Elizabeth
Background: General decline in motor performance is often cited in healthy aging, and motor deficits persist into the chronic phase of stroke recovery. Abnormalities in sensorimotor integration may underlie these motor deficits; however, the effect of aging and chronic stroke on sensorimotor integration neurophysiology is not well understood. Further, investigation into the plasticity of sensorimotor integration is important to establish in populations experiencing sensorimotor decline. Methods: The overall objective of this thesis was to comprehensively understand the neurophysiology of sensorimotor integration, including the influence of aging and chronic stroke on sensorimotor integration and the reliability of common neurophysiological measures. The first research chapter (Chapter 2) explores age and stroke-related differences in measures of indirect sensorimotor integration. Chapters 3 and 4 investigate baseline differences in measures of direct sensorimotor integration induced by aging and chronic stroke, respectively. Further, they use an intervention to index plasticity of sensorimotor integration in these populations. The final chapter (Chapter 5) addresses the reliability of a variety of neurophysiological methods used to examine somatosensory and motor cortical excitability, as well as sensorimotor integration. Summary of Findings: In Chapter 2, older individuals and individuals with chronic stroke had reduced short-latency afferent inhibition, compared to younger individuals suggesting the difference is largely driven by age-related factors. Greater disinhibition post-stroke related to worse motor function and impairment. Chapter 3 showed that measures of direct sensorimotor integration are less susceptible to age-related changes than measures of indirect sensorimotor integration. Sensory training altered direct but not indirect sensorimotor integration, suggesting independent modulation of separate anatomical pathways of sensorimotor integration. Chapter 4 highlighted differences in direct sensorimotor integration between individuals with chronic stroke and older individuals such that vibration had less of an impact on baseline motor cortex excitability in individuals post-stroke and the intracortical response to sensory training was reduced. Chapter 5 showed high reliability in transcranial magnetic stimulation thresholds, the amplitudes of evoked potentials elicited at high stimulation intensities, and latency-based measures. Conclusions: This dissertation contributes new knowledge to the impact of aging and chronic stroke on sensorimotor integration and the reliability of the measures used to quantify sensorimotor integration.
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