Investigating psychobiological mechanisms underlying dysregulated goal-pursuit across psychiatric disorders

This thesis examines the psychobiological mechanisms contributing to dysregulated reward processing differences in two parts: across psychiatric disorders (Part one), and in bipolar disorder (Part two). Part one comprises a systematic review and meta-analysis examining the extent to which four aspects of reward processing, namely the anticipation and evaluation of rewards and losses, exist transdiagnostically at the psychobiological level. 26 functional magnetic resonance imaging (fMRI) studies that examined whole-brain-based activation during a reward task (monetary incentive delay) and compared between patients and matched controls were included. Results showed that compared to controls, clinical groups exhibit shared increases and decreases in dorsal striatal activity during the evaluation of rewarding outcomes and anticipation of negative outcomes respectively. Part two presents an empirical study, which sought to combine computational modelling and fMRI data to investigate whether momentary changes in mood bias the perception of rewards more strongly in individuals with bipolar disorder than matched controls. Region-of-interest analyses in the ventral striatum, anterior insula and ventromedial prefrontal cortex and exploratory whole-brain analyses were conducted. Although results broadly confirmed previous findings that mood-biased influences on reward learning signals are represented in the reward system, preliminary evidence suggests that individuals with bipolar disorder represent them more strongly than controls in visual processing areas. Part three comprises a critical appraisal of the research process. This includes a discussion of the author’s influences on the research, the relevance of understanding mechanisms in psychological research and treatment and potential challenges of fMRI research, concluding with a summary of recommendations