Relationship of Dopamine to Cognitive Function in Parkinson's Disease

INCLUSION CRITERIA: PD patients must meet the diagnosis of idiopathic Parkinson's disease. Diagnosis will be based upon the presence of at least two of the four cardinal symptoms (tremor, bradykinesia, rigidity and instability) as well as a positive response to dopaminergic agents. Patients will be on stable dopaminergic therapy for approximately two weeks prior to enrollment. Control subjects must be healthy and aged 40 - 85 years and will be age and gender matched to PD patients. EXCLUSION CRITERIA - CONTROLS: Diagnosis of idiopathic Parkinson's disease. Secondary cause of Parkinsonism, e.g. Wilson's disease, neuroleptic use. Psychiatric disease that would, in judgment of the investigator, interfere with the safe conduct of the study. Current psychiatric illness. Severe depressive symptoms with BDI 16+. Substance abuse, severe systemic disease, poor vision or hearing based on history and physical exam. Incidence of Parkinson's disease in two or more first degree relatives. Dementia not due to PD or severe dementia with MMSE less than 15. Neurological disorder other than PD that would effect protocol (e.g. stroke, Alzheimer's disease). Laboratory tests with clinically significant abnormalities. History of an abnormal MRI. Pregnancy or breast feeding. Prior participation in other research protocols or clinical care in the last year such that radiation exposure would exceed the annual NIH RSC limits. Any conditions that increase risk for MRI (pacemaker, metallic foreign body, claustrophobia, etc.). Any medical condition that in the opinion of the investigators would interfere with the safe conduct of the study. Severe hypertension. The subject may be on anti-hypertensive medications. The initial screening must show no more than moderate hypertension - i.e. less than 160/95. In addition, the subject must have normal laboratory values (e.g., BUN, creatinine, urinalysis, and ECG) to document lack of end organ damage. On baseline evaluation on the day of the scan (i.e., before injection of tracer), the subject must be asymptomatic (no headache, dizziness, neurological symptoms, or blurred vision) AND have sustained BP less than 180/100. Inability to provide consent. Smoking within 6 months prior to enrollment in the study. EXCLUSION CRITERIA - PATIENTS: Secondary cause of Parkinsonism, e.g. Wilson's disease, neuroleptic use. Psychiatric disease that would, in judgment of the investigator, interfere with the safe conduct of the study. Current psychiatric illness except for depression. Severe depressive symptoms with BDI 16+. Substance abuse, severe systemic disease, poor vision or hearing based on history and physical exam. Dementia not due to PD or severe dementia with MMSE less than 15. Neurological disorder other than PD that would effect protocol (e.g. stroke, Alzheimer's disease). Laboratory tests with clinically significant abnormalities. History of an abnormal MRI. Pregnancy or breast feeding. Prior participation in other research protocols or clinical care in the last year such that radiation exposure would exceed the annual NIH RSC limits. Any conditions that increase risk for MRI (pacemaker, metallic foreign body, claustrophobia, etc.). Any medical condition that in the opinion of the investigators would interfere with the safe conduct of the study. Severe hypertension. The subject may be on anti-hypertensive medications. The initial screening must show no more than moderate hypertension - i.e. less than 160/95. In addition, the subject must have normal laboratory values (e.g., BUN, creatinine, urinalysis, and ECG) to document lack of end organ damage. On baseline evaluation on the day of the scan (i.e., before injection of tracer), the subject must be asymptomatic (no headache, dizziness, neurological symptoms, or blurred vision) AND have sustained BP less than 180/100. Inability to provide consent. Smoking within 6 months prior to enrollment in the study.