Eligibility Criteria- INCLUSION CRITERIA:
Normal neurological and physical examination.
Abstinence from alcohol one week before the study.
No medication that can influence the central nervous system for at least one week before the study because those medications may influence DA release.
Within normal range of neuropsychological and mood assessment.
No gender or ethnic preferences.
Patients with thromboembolic or hemorrhagic lesions, without direct involvement of the dorsal striatum or the cerebellum, as documented by CT or MRI.
At least 6 months post-stroke.
Initially had a severe motor paresis (below MRC grade 2), which subsequently recovered to the point that they have a residual motor deficit but can perform the required task (thumb flexion and extension).
NORMAL VOLUNTEERS AND STROKE PATIENTS:
The subjects belonging to one of the following groups will be excluded from the study:
1. Subjects with signs of parkinsonism.
2. Subjects with significant mood disturbances (score on BDI scale above 10).
3. Subjects with abnormal MRI findings on visual inspection (prominent normal variants such as mega cisterna or cavum septum pellucidum, signs of severe cortical or subcortical atrophy, brain tumors, trauma or AVMs). Stroke patients may have an ischemic territorial stroke and mild to moderate signs of vascular disease.
4. Subjects with prior exposure to neuroleptic agents or drug use.
5. Subjects with past or present neuropsychiatric illness, head trauma with loss of consciousness, epilepsy, past and present history of alcohol or substance abuse, including cigarettes, medical conditions that may alter cerebral functioning.
6. Subjects with positive urine toxicology.
7. 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.
8. Subjects with a positive urine pregnancy test or who are breastfeeding.
9. Subjects with an Hb less than 12.7 mg/dl (men) or an Hb less than 11.1 mg/dl (women).
ADDITIONALLY FOR STROKE PATIENTS:
1. Patients with more than one stroke.
2. Patients with bilateral motor impairment.
3. Patients with lesions in the dorsal striatum or cerebellum.
4. Patients or subjects unable to perform the task (thumb flexion and extension).
5. Patients or subjects with unstable cardiac arrhythmia.