Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Monique Timmer (Donders series 374)

16 April 2019

Promotors: prof. dr. R. Cools, prof. dr. B. Bloem
Co-promotors: dr. R. Esselink

Out of Balance: Neurocognitive mechanisms underlying depression in Parkinson’s disease

Depression is a common symptom in Parkinson’s disease and has a tremendous impact on the quality of life. Why Parkinson’s disease patients so often suffer from depression is still largely  unknown. The research presented in this thesis focuses on dopamine in relation to negative biases – weighing the negative more strongly than the positive. In short, the research shows that Parkinson’s disease patients with a depression (history) are impaired at learning from reward versus punishment. This is accompanied by altered striatal reward versus punishment signalling. By contrast, reward motivation is contradictory enhanced in Parkinson’s disease and not different between Parkinson’s disease patients with and without a depression (history). Moreover, we showed that, in nondepressed patient, dopaminergic medication increases the tendency to gamble irrespective of the value of the gamble. By contrast, in depressed patients, dopaminergic medication alters the relative weighing of gains versus losses during risky choice (i.e. decreases loss aversion). Together the research contributes to enhanced understanding of the mechanisms underlying depression in Parkinson’s disease.