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Title: Investigating the role of inhibition in healthy human motor system plasticity
Author: Johnstone, Ainslie
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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Across our lifespan we encounter novel physical problems that must be overcome by learning to produce new movements, or to adapt the movements we already know. Learning or adaptation of these skills is the result of plastic changes occurring across a network of motor areas within the brain. The factors influencing these changes across the brain, and how they link to behaviour are not currently well understood. This multimodal thesis primarily focuses on elucidating the link between motor system inhibition, plasticity, and motor learning. It does so by using magnetic resonance spectroscopy (MRS) and transcranial magnetic stimulation (TMS) to measure inhibition, and using a variety of tasks to assess motor learning. Firstly, the neurochemical changes induced by the 'plasticity enhancing' intervention, transcranial direct current stimulation (tDCS), were investigated. We found that tDCS caused changes in inhibition across the motor network, and that these changes were related to individuals' white matter microstructure. Next the effect of primary motor cortex (M1) tDCS on skill learning with the ipsilateral hand was probed. Here we found that anodal tDCS caused impairment of learning, but this may be offset, in part by decreases in inhibition occurring in the contralateral M1. Finally, we explored the effect of directly modulating inhibitory signalling on healthy human motor learning. We found that using a single, clinically-relevant, dose of baclofen to increase inhibitory signalling caused impairments in performance on an adaptation task. Behaviour changes in this task were related to the degree of inhibition change within the contralateral M1. Taken together this work strengthens support for the theory that reducing inhibition within M1 is vitally important for allowing the normal plastic processes underpinning motor learning to occur. However, these results also highlight the importance of inhibition changes across the motor network. Investigating these changes, and how they affect network interactions is crucial if we are to understand how healthy motor learning occurs, and leverage this understanding to enhance learning in health and disease.
Supervisor: Stagg, Charlotte ; Johansen-Berg, Heidi Sponsor: Nuffield Department of Clinical Neuroscience ; Medical Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available