Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Physiology and Pharmacology


MacDonald, Penny A.

2nd Supervisor

Owen, Adrian M.



The striatum, the input region of the basal ganglia, has been shown to mediate many cognitive functions. The striatum itself can be functionally segregated into dorsal (DS) and ventral striatum (VS). For more than 60 years, DS has been reported to mediate stimulus-response learning, though evidence has been accruing pointing to a role in decision making. These literatures have been growing independently and an aim of this thesis was to bridge these two bodies of knowledge. We directly investigated the role of DS in stimulus-response learning versus decision making using functional magnetic resonance imaging (fMRI) in patients with Parkinson’s disease (Chapter 2) and obsessive compulsive disorder (Chapter 3). In Chapter 4, the role of DS in stimulus-response habit learning was tested in healthy individuals using fMRI. In three separate experiments (Chapters 2-4), all of the results strongly support the notion that DS mediates decision making and not learning. DS is implicated in many disorders ranging from Parkinson’s disease, obsessive compulsive disorder and addiction, and clarifying the role of DS in cognitive function is paramount for understanding substrates of disease and developing treatments.