Screening evaluation: The Investigators will ask questions to see if the participant qualifies to be in the study. The screening visit will occur up to 4 months before the first study visit, and can be scheduled to occur on the same day as the first study visit. This evaluation will include a review of medical history and clinical findings related to Parkinson's Disease (if applicable). There may be a neurological exam (physical exam). Women of child bearing potential will take a urine pregnancy test. If applicable, the medications currently used to treat Parkinson's Disease symptoms will be reviewed and subjects will be asked to discontinue them for some hours on the days of the study visits. The investigators do not expect concerns or unwanted consequences arising either from discontinuing the Parkinson's Disease medications or turning off the DBS stimulator for the duration of time proposed in the study.