Depression is a common and potentially serious complication of Parkinson's disease (PD). Studies show that approximately 40 percent of PD patients are depressed. There is evidence that these patients have deficits in neuropsychological function relative to non-depressed PD patients. Despite the widespread toll on emotional health posed by PD, few studies have undertaken a comprehensive examination of the neural underpinnings of Parkinsonian depression. In this project, we will compare depressed versus non-depressed Parkinson patients to a sample of demographically-matched healthy controls using neuropsychological assessment and magnetic resonance imaging (MRI). To investigate possible effects of anti-Parkinsonian medication on mood, cognitive function, and neural response, PD patients will be tested both off and on Parkinsonian medications.