Movement State-dependent Adaptive DBS for PD

Inclusion Criteria: * Ability to give informed consent for the study * Subjects implanted with Summit RC+S investigational DBS system. * Absence of significant cognitive impairment (score of 21 or greater on the Montreal Cognitive Assessment (MoCA) * Signed informed consent * Age 21-75 * Diagnosis of idiopathic PD with duration of motor symptoms for 3 years or greater * Patient has undergone appropriate therapy with oral medications with inadequate relief as determined by a movement disorders neurologist. * UPDRS-III score off medication between 20 and 80 and an improvement of at least 30% in the baseline UPDRS-III on medication score, compared to the baseline off-medication score, and motor fluctuations with at least 2 hours per day of on time without dyskinesia or with non-bothersome dyskinesia. OR Patients with tremor-dominant PD (a tremor score of at least 2 on a UPDRS-III sub-score for tremor), treatment resistant, with significant functional disability despite maximal medical management * Patients with gait impairments: slowed gait, shuffling steps, postural instability, or freezing of gait off medication. Exclusion Criteria: * Inability to comply with study procedures * Patients who cannot walk (wheelchair bound)