Evaluating Motivation and Reward Mechanisms and Brain Substrates in Adults With Obesity

Evaluating Motivation and Reward Mechanisms and Brain Substrates in Adults With Obesity: Further Evidence That Obesity Affects Physical and Mental Health

Anhedonia and abnormalities in reward behavior are core features of overweight/obesity (OW), a highly prevalent condition within MDD populations, and is independently associated with reward disturbances. The investigators therefore aim to investigate the brain substrates subserving reward and motivation in adults with overweight/obesity.

The primary aim of this pilot study is to determine whether associations exist between obesity and decreased performance on the respective motivation/reward paradigms.

Herein, the investigators are primarily interested in three overlapping, yet distinct aspects, of anhedonia. The investigators are primarily interested in motivation, reward valuation, and reward learning towards addressing the measurement of each of these respective subdomains, eligible participants will complete validated gold standard measures (i.e. the Effort Expenditure for Rewards Task (EEfRT) (reward valuation), Probabilistic Reward Task (PRT) (reward learning), and the Monetary Incentive Delay (MID) task (reward anticipation)).

Twenty adults with overweight/obesity will complete all tasks at a single visit with two of the tasks being completed prior to MRI and one of the tasks (i.e. EEfRT) will be completed during MRI acquisition.

The primary aim of this pilot study is to determine whether associations exist between obesity and decreased performance on the respective motivation/reward paradigms. In addition, associations between performance on reward tasks and functional connectivity, as measured by MRI and DTI, a secondary objective is to ascertain whether associations exist between performance on the motivation reward tasks and gold standard measures of food intake (i.e. food diary) and energy expenditure (i.e. calorimetry).

Inclusion Criteria:

• 18-65 years of age
• Meeting DSM-V criteria for: (i) Major depressive disorder (symptomatic or asymptomatic in any phase of the illness) or (ii) bipolar disorder I/II (symptomatic or asymptomatic in any phase of the illness)
• Ability to provide written and informed consent
• Obesity 30 kg/m2
• Weight under 440lbs
• Shoulder-to-shoulder width under 60 cm

Exclusion Criteria:

• Age below 18 or above 65
• Use of benzodiazepines or consumption of alcohol within 12 hours of assessments
• Abuse of marijuana
• Physical, cognitive, or language impairments sufficient to adversely affect data derived from assessments
• Diagnosed reading disability or dyslexia
• Clinically significant learning disorder by history
• History of moderate or severe traumatic brain injury
• Other neurological disorders, or unstable systemic medical diseases
• Pregnancy and post-partum period
• Presence of any contra-indications for MRI
• Weight above 440lbs
• Shoulder-to-shoulder width greater than 60 cm.

All subjects will be consented prior to initiating the study; >45 BMI; suicidality as determined by clinical discretion