Dissociating Components of Anhedonia: A Pilot fMRI Study

Study Summary

Anhedonia, decreased motivation for and sensitivity to rewarding experiences, is present in at least 1/3 of community dwelling older adults and is a feature of various psychiatric and neurological disorders, including late-life depression and Parkinson's disease. Anhedonia is associated with cognitive deficits, as well as poor clinical outcomes and increased mortality. Recent research suggests that anhedonia comprises motivational (reward "wanting") and consummatory (reward "liking") aspects. However, previous research on anhedonia has failed to dissociate these components, which may explain the contradictory findings in the literature. Recently, the Effort-Expenditure for Rewards Task (EEfRT) was developed in an effort to dissociate reward components in anhedonia. The EEfRT is an effort-based decision-making task that measures reward "wanting", in contrast to commonly used anhedonia questionnaires, which focus on reward "liking." This novel task may provide a useful measure of components of anhedonia in older adults and in different patient populations. Thus far no data is available on this task in elderly individuals, and the cognitive and neural correlates of components of the task have not been investigated. Given the paucity of research on the neurobiology of anhedonia, cognitive neuroscience studies using this task could fill a gap in the literature. The investigators are developing a line of cognitive neuroscience studies examining anhedonia in community-dwelling older adults and in late-life depression and Parkinson's disease. This study will involve gathering pilot behavioral and functional magnetic resonance imaging (fMRI) data in young and older adults performing the EEfRT task. Understanding the brain mechanisms underlying anhedonia in older adults and in different patient populations will have a translational impact by elucidating biological targets for treatment.

Primary Outcome

To quantify brain activity associated with reward "wanting," the investigators will contrast fMRI activation while participants view information about reward probability and choose to perform the easy or hard task with activity during fixation. The investigators will contrast activation during performance feedback and presentation of reward magnitude with activation during fixation to capture brain activity associated with reward "liking." Parameter estimates (ß) will be generated, which indicat

Interventions

• OTHER Functional Magnetic Resonance Imaging
• OTHER Effort-Expenditure for Rewards Task