Dissociating Components of Anhedonia: A Pilot fMRI Study

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.

Twenty young adults (aged 18-38) and 20 older adults (aged 60-80) will perform the EEfRT while fMRI data are acquired. To quantify brain activity associated with reward "wanting," the fMRI activation will be measured while participants view information about reward probability and choose to perform the easy or hard task, with greater reward associated with the hard task. The investigators will measure activation during presentation of reward magnitude to capture brain activity associated with reward "liking." Participants will also complete a brief cognitive battery and anhedonia questionnaires.

Eligibility Criteria:
Inclusion Criteria:

* Age 18-38 or 60-80 years
* Able to provide verbal and written consent
* Right-handed
* Native English speaker
* At least 12 years of formal education

Exclusion Criteria:

* Significant cognitive disturbance
* Self-report of current or past history of psychiatric disturbance other than major depression (e.g., bipolar disorder, schizophrenia, alcohol and/or substance abuse)
* Self-report of neurological disturbance (stroke, dementia, traumatic brain injury), chronic medical illness (HIV, metastatic cancer), or unstable medical conditions (cardiac or pulmonary disease)
* Physical impairments, language comprehension deficits, or significant hearing disturbances that would limit ability to perform tasks
* Current anticholinergic, psychotropic (stimulants or dopamine agonists), or anti-epileptic use
* Visual acuity difficulties that would interfere with task performance
* Motor deficits that may interfere with the use of the dominant hand for performance of button press associated with the EEfRT task
* MRI contraindications (e.g., ferrous metal in the body, claustrophobia, pregnancy)