ON/OFF Stimulation and Impulsivity in Patients With Deep Brain Stimulators

The investigators propose a test of causality by examining a cohort of patients undergoing deep brain stimulation (DBS) within the ventral striatum. The investigators will examine behavior on and off stimulation across a range of tasks that index different forms of impulsivity. Patients will be studied in both the ON and OFF state - that is, they will be tested during active deep brain stimulation and 30 min to 1 hour after stimulation has been stopped (order of state will be counterbalanced across subjects). The investigators specific aim is to test the hypothesis that enhancing ventral striatal signaling (i.e. ON-state DBS) will cause more impulsive patterns of behavior across several impulsivity tasks. The investigators predict that ventral striatal DBS will increase stop-signal reaction time on the stop-signal task and commission errors on the Go/NoGo task, and increase delay aversion in a delay discounting paradigm.