Chahal, Amanpreet2024-05-302024-05-302022https://hdl.handle.net/2440/141047This item is only available electronically.Parkinson's disease (PD) is the second most common progressive neurodegenerative disease, with patients typically losing 60-80% of dopamine by the time they are diagnosed. However, subtle symptoms appear years before a diagnosis, and this prodromal phase would be a favourable window for early therapeutic interventions. In this study, we sought to identify individuals in the general population who might be in the prodromal phase and determine whether they show Parkinsonian-like symptoms. REM sleep behaviour disorder (RBD) is the most reliable predictor of PD within that prodromal window. The RBD is also strongly associated with reduced cognitive function, and we tested whether that association could be replicated. However, previous studies have not explored the relationship between RBD and more specific cognitive impairments associated with PD, namely, dysfunction of the basal ganglia, which leads to impaired reward learning and enhanced punishment learning. Hence, the second aim of this study was to determine whether this prodromal feature correlates with Parkinson's-specific cognitive decline in the general population. Participants completed the RBD Screening Questionnaire (RBDSQ) to indicate their probable RBD symptoms. General cognition and learning rate imbalance were assessed using a battery of automated tests and probabilistic reinforcement learning tasks, respectively. We found that probable RBD was a significant predictor of cognitive decline; however, this effect interacted with age. No significant results emerged for Parkinson's-specific cognitive decline. It is possible that RBD might be associated with several other neurodegenerative disorders, not necessarily PD, but determining their precise relationship remains a critical area of future study. Keywords: Parkinson's Disease, REM sleep behaviour disorder, RBD disorder, basal ganglia dysfunction, learning rate imbalanceHonours; PsychologyThesis