 Standard intraoperative neurophysiological and imaging techniques will be used. In awake patients these techniques are used to identify and confirm that the DBS electrode is implanted in accurate position. These techniques include microelectrode recording where individual neurons are monitored as the electrode is inserted through the brain tissue. Early research reports suggest that sedation may affect the neuronal activity. But our preliminary data indicates that is still reliable under intravenous anesthesia. Macrostimulation using the implanted DBS electrode can suppress tremor, stiffness, and slowness of Parkinsons disease, and assists in confirmation of electrode position. It also causes side effects including tingling, and facial contractions. These methods will also be studied in the asleep patients. The O-arm is an intraoperative CT scanner that visualizes the DBS electrode. O-arm images will be obtained in the standard fashion in both groups. The accuracy of intraoperative imaging will be compared to standard postoperative MRI. The clinical outcome from these two techniques will be compared. The clinical outcome will be measured with standard Parkinsons disease research tools including video taped and independently rated motor exam, as well as the Unified Parkinsons Disease Rating Scale UPDRS. Gait analysis will be collected using the APDM system. These will be tested before and at 3 months after surgery by the neurologist. 