Experimental: chronic brain recording This is a one-arm, single-center study of the neurophysiology of human movement disorders with two goals: 1) Assess the feasibility of chronic brain recording using a novel fully implantable pulse generator (Medtronic Activa PC+S), which has the capability of sensing and storing local field potentials (LFPs) recorded from implanted electrodes, in addition to providing therapeutic deep brain stimulation (DBS). 2) Study acute and chronic effects of therapeutic DBS on cortical LFPs. 3) Study feasibility of the use of brain signals as feedback either directly to the patient or for DBS stimulation adjustments.