How the Loss of Dopamine and Dopamine-Restoring Medicines Affect Movement Performance

This study has two purposes: 1) to understand the effect of a decline of dopamine in the brain during normal aging and in patients with Parkinson's disease, and 2) to investigate how medicines used to treat Parkinson's disease improve movement performance in patients. Patients with Parkinson's disease have difficulty performing precise finger movements, mainly because of a dramatic decrease of a substance called dopamine in parts of the brain. Medicines such as levodopa, which help restore dopamine levels, can greatly improve function; however, little is known about how these drugs work. In normal aging, dopamine decreases slightly in certain parts of the brain, but the importance of this decline is poorly understood. This study may provide new information about Parkinson's disease and normal aging that might lead to better treatment strategies. Patients with mild to moderate Parkinson's disease and healthy volunteers 21 years of age and older may be eligible for this study. All participants must be right-handed. All candidates will be screened with a medical history and physical and neurological examinations, including memory tests and mood examination. Brain function will be studied using functional magnetic resonance imaging (fMRI) study and positron emission tomography (PET). Participants may be asked to stop using medications that can affect the central nervous system, such as sleeping pills or drugs for depression or anxiety, for 1 week before each study visit. Patients with Parkinson's disease may also be asked to stop using antiparkinsonian medications at least 12 hours before each visit. In addition, all participants will be asked to abstain from alcoholic beverages at least 24 hours before the fMRI and PET scans, and from nicotine and caffeine for at least 12 hours before the scans. Participants will have fMRI, which uses a strong magnetic field and radio waves to create images of the brain. The subject lies on a table in a tunnel-like cylinder (the sc