Eligibility Criteria- INCLUSION CRITERIA: Healthy Volunteers
- Age between 18-80 years
- Able to perform tasks required by the study
- Willing and able to give consent
- Have a normal physical and neurological examination
- Right Handed as assessed by the Edinburgh inventory scale (Edinburgh, 1971)
EXCLUSION CRITERIA: Healthy Volunteers
- History of alcohol or drug abuse, and psychiatric illness such as severe depression.
- Receiving drugs acting primarily on the central nervous system, which lower the seizure threshold such as antipsychotic drugs (chlorpromazine, clozapine) or tricyclic antidepressants.
INCLUSION AND EXCLUSION CRITERIA FOR STROKE PATIENTS:
Patients must be between the ages of 18 and 80 years of age, inclusive. Included will be those with chronic (more than 3 months) stroke who recovered motor function to the point of being able to perform the ballistic pinch force task. Stroke patients will be recruited through the NIH Clinical Research Volunteer Program. Assessment of severity of initial hemiparesis will be taken either from patient report or medical records.
EXCLUDED FROM THE STUDY WILL BE PATIENTS:
1. with a history of severe alcohol or drug abuse, psychiatric illness like severe depression, severe language disturbances, particularly of receptive nature or with serious cognitive deficits (defined as equivalent to a mini-mental state exam (Folstein, 1976) score of 23 or less)
2. with severe uncontrolled medical problems (e.g., cardiovascular disease, severe rheumatoid arthritis, active joint deformity of arthritic origin, active cancer or renal disease, any kind of end-stage pulmonary or cardiovascular disease, or a deteriorated condition due to age, uncontrolled epilepsy or others)
3. with metal in the body (metal in the cranium, metal fragments from occupational exposure, surgical clips in or near the brain, cardiac or neural pacemakers, intracardiac lines, implanted medication pumps, blood vessel, cochlear or eye implants)
4. with history of loss of consciousness or epilepsy
5. with history of hyperthyroidism or individuals receiving drugs acting primarily on the central nervous system, which lower the seizure threshold such as antipsychotic drugs (chlorpromazine, clozapine) or tricyclic antidepressants.