Approach Motivation, Goal Pursuit, and Reward-Related Neural Responses: A Combined Experience-Sampling and fMRI Approach.

Abstract

This thesis examines potential associations between trait approach motivation and related measures, the everyday experience of affect and goal pursuit, and reward-related neural responses. The Behavioural Activation System (BAS) is a core motivational system, subserved by the neural reward circuitry, eliciting approach-type behaviour and positive emotion when activated by appetitive stimuli. Deficits in BAS sensitivity are thought to underlie the lack of motivation and positive affect (PA) that characterise anhedonia, whilst hyperactivation of the BAS has been linked to the increased goal-directed behaviour and positive affectivity associated with hypomania. In order to explore relationships between BAS sensitivity, goal pursuit, and reward processing, young participants, recruited from the student population (N = 65), and older participants, from the community (N = 63), underwent a 7-day period of experience sampling (ESM) to provide a naturalistic measure of momentary affect and goal-focused motivation. Functional Magnetic Resonance Imaging (fMRI; in a subset of n = 28 and n = 31 respectively) was then used to investigate individual differences in sensitivity of brain reward-related systems to various social and non-social rewards. Limited support was found for the relationship between BAS traits and the more motivational aspects of goal pursuit and reward processing, whilst anhedonia seemed to pertain more to reward consumption, with few links to everyday goal pursuit. This would indicate that anhedonia might not be as closely related to BAS sensitivity as was initially anticipated. Finally, in order to examine real-world correlates of neural activation, the data from the naturalistic measure were correlated with reward-related activation. Everyday PA correlated with striatal activation when viewing pleasant images, but no other associations emerged. This would suggest that the basic measures of brain function in relation to the particular reward-related stimuli used might be of limited relevance to everyday affective experience and goal pursuit.