Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and the globus pallidus interna (GPi) has been shown to relieve the motor symptoms of Parkinson's disease (PD) such as tremor, rigidity, and bradykinesia. However, there is increasing evidence that DBS may be associated with a significant number of mood and cognitive changes. The aims of this study are to characterize and compare the mood and cognitive effects associated with DBS of the STN and GPi, to delineate regions within or around the STN and GPi that are associated with specific mood and cognitive changes when DBS is applied to these areas, and to assess the relative effectiveness of right versus left STN or GPi stimulation on mood and cognition. In the study, researchers will compare motor, mood, and cognitive function in people with PD who have had DBS treatment with control subjects (or individuals with PD who have not had DBS). The scientists will characterize the types and incidence of mood and cognitive changes that occur during DBS in each target (STN and GPi), compare the targets, and examine the role of lead location. The study will enroll 62 participants-10 control subjects (individuals with PD who have not had DBS), and 52 individuals with PD who are scheduled for DBS; the site of the implant (STN or GPi) will be randomly assigned. Participants will perform motor, mood, and cognitive tests (following 6 months of stimulation) over a 2-day period. Duration of the trial for participants is 6 months and includes a 2-night hospital stay. Findings from this study may help researchers better understand how DBS affects non-motor circuitry.
Inclusion Criteria: - Intractable, disabling PD with motor fluctuations, dyskinesias, or freezing episodes - Age between 30-75 years - Unsatisfactory clinical response to maximal medical management (with trials of both higher and lower doses of anti-Parkinsonian drugs) - A stable and optimal medical regimen of anti-Parkinsonian drug therapy for at least three months prior to surgery - Patients must be right-handed to be included in the study since mood and cognition are being analyzed and right hemisphere dominant patients could confound the results. Exclusion Criteria: - Clinically significant medical disease that would increase risk of developing pre- or postoperative complications (e.g., significant cardiac or pulmonary disease, uncontrolled hypertension) - Evidence of secondary or atypical parkinsonism as suggested by the presence of any of the following: 1) history of stroke(s), 2) exposure to toxins or neuroleptics, 3) history of encephalitis, 4) neurological signs of upper motor neuron disease, cerebellar involvement, supranuclear gaze palsy, or significant orthostatic hypotension - MRI scan with significant evidence of brain atrophy or other abnormalities (e.g., lacunar infarcts or iron deposits in the putamen) - The Mattis Dementia Rating Scale will be used to assess the level of intellectual function and patients will be excluded with scores reflecting clinical dementia - A major psychiatric disorder on the Structured Clinical Interview for DSM-IV (SCID-IV).