Observational Learning in Stroke Patients

INCLUSION CRITERIA: We will include PATIENTS: Who are aged 18 to 75, With a single thromboembolic non-hemorrhagic hemispheric lesions, With at least a 3 months period since the stroke, Who initially had a severe motor paresis (below MRC grade 2), Who subsequently recovered to the point that they can perform the motor tasks of this study, With no history of other neurological and psychiatric illness, Who are right-handed (before the stroke history). As a control group, we will include NORMAL VOLUNTEERS, Who are age- and gender matched to stroke PATIENTS, Who can perform the motor tasks of this study, With no history of other neurological and psychiatric illness, Who are right-handed. EXCLUSION CRITERIA: PATIENTS with more than one stroke in the medial cerebral artery territory. PATIENTS with bilateral motor impairment. PATIENTS with cerebellar or brainstem lesions. PATIENTS and NORMAL VOLUNTEERS unable to perform the task. PATIENTS and NORMAL VOLUNTEERS with history of severe alcohol or drug abuse, psychiatric illness like severe depression, poor motivational capacity, or severe language disturbances, particularly of receptive nature or with serious cognitive deficits (defined as equivalent to a mini-mental state exam score of 23 or less). PATIENTS and NORMAL VOLUNTEERS 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). PATIENTS and NORMAL VOLUNTEERS with increased intracranial pressure (as evaluated by clinical examination). PATIENTS and NORMAL VOLUNTEERS with unstable cardiac arrhythmia. PATIENTS and NORMAL VOLUNTEERS with h/o hyperthyroidism or individuals receiving drugs acting primarily on the central nervous system. PATIENTS and NORMAL VOLUNTEERS with more than moderate to severe microangiopathy (as assessed by multiple peri-ventricular T2 hyperintensity on the pre-experimental anatomical MRI), polyneuropathy (as assessed by clinical examination), diabetes mellitus (medical record), or ischemic peripheral disease (as assessed by clinical examination). PATIENTS and NORMAL VOLUNTEERS who are or who have been good skilled piano or string instruments players. PATIENTS and NORMAL VOLUNTEERS who is on medication with the potential to influence nervous system function, who has a history of surgery with metallic implants or a known history of metallic particles in the eye, a cardiac pacemaker, intracardiac lines, neural stimulators, cochlear implants. PATIENTS and NORMAL VOLUNTEERS who are pregnant. PATIENTS and NORMAL VOLUNTEERS with significant visual loss/deficits. PATIENTS and NORMAL VOLUNTEERS with MRI contraindications.