- Major psychiatric disorder on the Structured Clinical Interview (SCID-IV) for the Diagnostic and Statistical Manual Version 4 (DSM-IV). 45 Patients with Major Depression within 3 months of entry into the study will be excluded. High rates of psychiatric co-morbidity can complicate any neurosurgical study. While the cleanest study would exclude patients with psycho-pathology, we do not believe this is realistic or practical, given the majority of patients with advanced movement disorders will suffer from some degree of anxiety or depression. We will screen patients for psychiatric disorders, treat disorders prior to DBS and admit patients who are psychiatrically stable for at least 3 months prior to entry (without active psychiatric diagnosis by SCID criteria).