| Abnormal reward-related functioning is a central clinical feature of bipolar disorder (BD). Recent findings suggest that heightened reward sensitivity may represent a trait vulnerability factor for, and a persistent feature of the disorder. Investigations into the neurobiological substrates of these clinical observations have the potential to improve our understanding of the disorder and spur the development of improved treatments. However, research in this area has been stymied by a paucity of studies delineating the nature of dysfunctions in brain reward processing at the network level, and relating these directly to clinical features of the disorder. The current dissertation aimed to characterize brain reward processing in a sample of euthymic BD and healthy comparison participants and relate these findings to BD symptoms and functioning over time. To this end, a novel social incentive delay task was employed alongside a monetary incentive delay task during neuroimaging of adults with remitted BD type I (N=24) and a healthy non-psychiatric control group (HC; N=25) using fMRI. A follow-up assessment of symptoms and functioning over the year following the scan was conducted in a subset of the BD sample (N=20). Results revealed elevated striatal reactivity across monetary and social reward receipt, and reduced fronto-striatal connectivity during processing of no-win outcomes in the BD group. Associations with self-reported affect and behavior indicated that these neural patterns may underlie persistent reward pursuit in BD. Prospective analyses broadly indicated that neither striatal reactivity to rewards nor frontostriatal connectivity after no-win outcomes were predictive of BD symptom course. Taken together, the current dissertation describes the first comprehensive investigation into the neural, behavioral, and affective patterns of reward-related dysfunctions in BD, and provides a new methodological framework for examining the nature of reward processing dysfunctions in psychopathology. |
