The purpose of the proposed study is to demonstrate that the functional outcomes of the "asleep" technique are not inferior to those reported for traditional "awake" DBS technique. The primary data points for this study will include six month functional outcomes using accepted metrics for Parkinson's disease, including both motor function (Unified Parkinson's Disease Rating Scale [UPDRS] obtained in the medication "on" and medication "off" states) and quality of life (Parkinson's Disease Questionnaire-39). The null hypothesis is that asleep DBS results in inferior UPDRS-III scores at 6-months after surgery. Our secondary aim will be to evaluate any cognitive changes associated with DBS surgery selection (awake vs. asleep) in PD patients. Current standard of care for patient selection in DBS focuses primarily on the evaluation of motor symptoms and currently there is no guidance for how a patients' DBS surgery selection (awake vs. asleep) would impact on subsequent neurocognitive function.