The study will enroll 62 participants—10 control subjects (individuals with PD who have not had DBS), and 52 individuals with PD who are scheduled for DBS; the site of the implant (STN or GPi) will be randomly assigned. Participants will perform motor, mood, and cognitive tests (following 6 months of stimulation) over a 2-day period. Duration of the trial for participants is 6 months and includes a 2-night hospital stay.