Title: Mental Health in the Aging Population: An Investigation of the Interplay Between Depression Symptoms, Reward Processing, and Physical Activity in Older Adults

Program: Kinesiology MS

Committee Chair: Mariane Bacelar

Committee: Mariane Bacelar, CJ Brush, Lynda Ransdell

Abstract: Though depression is a common and debilitating mental health disorder, little is known about its underlying neural mechanisms. The few existing studies in this area have found a negative association between depression’s core symptom, anhedonia, and reward processing, which is often assessed via the electroencephalography (EEG)-derived measure Reward Positivity (RewP). Importantly, most of these studies were done in younger populations, which is problematic as age-related cognitive changes may cause depression to manifest differently among older adults. Regarding treatment options, physical activity (PA) has been proposed as an antidepressant, but its benefits at the brain level remain poorly understood. Thus, in the present study, we used the Geriatric Depression Scale (GDS) and 7-day accelerometry to assess depression and PA, respectively, in 30 older adults, and correlated these measures with participants’ RewP amplitude. We predicted that a smaller RewP would be associated with greater GDS scores but that this relationship would be weaker for participants engaging in more lifestyle PA (i.e., unstructured, activities of daily living). We focused specifically on lifestyle PA as it might be less daunting than structured exercise for those experiencing depressive symptoms (e.g., low motivation, fatigue). Results showed that RewP amplitude did not statistically predict GDS scores among older adults (p = .823). Further, no moderation effect of physical activity on RewP amplitude was observed (p = .601). Despite the null results, the design and innovative approaches (use of EEG and accelerometry in older adults) still render this study informative and highlight the need for more investigations targeting the mechanisms underlying depression in older adults.