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Decline in motor control in aging and Parkinson’s disease: The role of cortico-cortical connectivity measured using dual-site TMS

Rurak, Brittany K. (2021) Decline in motor control in aging and Parkinson’s disease: The role of cortico-cortical connectivity measured using dual-site TMS. PhD thesis, Murdoch University.

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Abstract

Parkinson’s disease (PD) is a chronic, progressive, and disabling neurological condition characterised by motor- and non-motor symptoms. A debilitating motor symptom of PD is resting tremor, which is the involuntary shaking of one or multiple body parts that substantially affects activities of daily living and functional independence. As PD resting tremor is not associated with the typical progressive degeneration of dopaminergic neurons in the basal ganglia, other brain regions likely play a role in tremor production. The overarching aim of this thesis was to use dual-site transcranial magnetic stimulation (TMS) to examine connectivity between brain regions thought to be implicated in PD tremor, including between the cerebellum and the primary motor cortex (M1) and between the supplementary motor area (SMA) and M1. The first aim was to establish test re-test reliability of dual-site TMS measures of cerebellum-M1 and SMA-M1 connectivity (Chapters 2-3). In younger adults, moderate reliability was found for cerebellum-M1 and SMA-M1 connectivity; for older adults, moderate reliability was found for SMA-M1 connectivity, and poor reliability was found for cerebellum-M1 connectivity. The second aim was to determine whether cerebellum-M1 and SMA-M1 connectivity plays a role in motor control in older adults (Chapters 2 and 4). Cerebellum-M1 and SMA-M1 connectivity were greater in younger than older adults, and weak connectivity was associated with poor motor control in older adults. The third aim was to determine whether SMA-M1 connectivity was associated with resting tremor severity in PD (Chapter 5). SMA-M1 connectivity was stronger ON than OFF levodopa medication, and weak connectivity was associated with greater tremor severity. Together, SMA-M1 connectivity was affected by age and PD and plays a role in declining motor control. These results provide a neurophysiological basis for developing interventions to improve motor control in aging and PD.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Psychology, Counselling, Exercise Science and Chiropractic
Supervisor(s): Vallence, Anne-Marie, Drummond, Peter, Power, B. and Rodrigues, J.
URI: http://researchrepository.murdoch.edu.au/id/eprint/64831
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