The goals of this study are to evaluate local field potentials (LFP) and associated beta, gamma and other band oscillations and their correlation with disease pathophysiology and clinical status of the patients, and to potentially determine a more objective biomarker of response to deep brain stimulation (DBS) treatment. This study aims to find evidence that changes in the power and coherence of the beta and gamma bands can be consistently linked to DBS adjustment and associated clinical effects. This approach can be of significant potential benefit to provide a foundation for closed loop DBS therapy in patients with continuous DBS adjustments.