Patient description: The patient is a 55-year-old man who was recently diagnosed with Parkinson's disease. He is complaining of slowness of movement and tremors. His disease is ranked as mild, Hoehn-Yahr Stage I. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with gardening before his diagnosis. He complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is offered Levodopa and Trihexyphenidyl. He is an alert and cooperative man who does not have any signs of dementia. He does not smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 21.0-999.0,  Parkinson Disease We will only PD patients with a stable clinical response to L-DOPA and DAergic agents. We will only recruit patients with early or mild-to-moderate PD (score on Hoehn & Yahr scale 148 less than 3). To obtain a homogeneous group, the PD cohort will comprise only non-demented, non-depressed, with parkinsonian symptoms and signs primarily akineto-rigid. If resting tremor is present, only patients with mild or moderate tremor (UPDRS tremor ratings 1 or 2 in the right upper limb) will be included in the study. Our group of healthy volunteers will the following age range: 21-30 years, 31-40 years, 41-50 years, 51-60 years, 61-70 years, and 70 years and over. Research subjects may be male or female and they must be right-handed. Pregnant women will not participate in the study. Research subjects will be asked to refrain from caffeine and nicotine for at least 12 hours and to abstain from alcohol at least 24 hours before the fMRI  Subjects belonging to one of the following groups will be excluded from the study: Subjects with a familial history of PD. Patients with a marked resting tremor (score at the UPDRS scale above 3 in the right upper limb). Patients with a score at Hoehn & Yahr scale equal or above 3. Patients with progressive neurological disorders other than PD. Subjects with cognitive impairment (i.e., score on Mattis scale below 123/144). Subjects with significant mood disturbances (i.e., score on BDI scale above 10). Subjects with abnormal MRI findings at visual inspection (prominent normal variants such as mega cisterna or cavum septum pellucidum, signs of severe cortical or subcortical atrophy, brain tumors, vascular diseases, trauma or AVMs). Subjects with a history of significant medical disorders, or requiring chronic treatment with other drugs that cannot be stopped. Subjects with prior exposure to neuroleptic agents or drug use. Subjects with significant past and present history of hypertension, cardiovascular disease and diabetes mellitus. Subjects with severe orthopedic or rheumatologic pathology of the right upper limb. Subjects with past or present neuropsychiatric illness, head trauma with loss of consciousness, epilepsy, cerebro-vascular disease, past and present history of alcohol or substance abuse, including cigarettes, medical conditions that may alter cerebral functioning Subjects with cancer. Subjects who have pacemakers, aneurysm clips (metal clips on the wall of a large artery), metallic prostheses (including heart valves and cochlear implants) or shrapnel fragments. Subjects incapable of giving an informed consent. Subjects with a positive pregnancy test. Subjects with pre-existing eyes condition. Subjects who are unable to tolerate being off of antiparkinsonian medications for 12 hours. Children will be excluded from the study because PD is infrequent before age 30