Transfer of Grasp Control Across Hands After Stroke

Inclusion Criteria: 1. Previously right-handed subjects with hemiparesis and complaints of unilateral hand dysfunction during grasping resulting from a single unilateral cerebral infarct in the MCA territory affecting either the right or the left side of the brain at least 3 months prior to data collection 2. Previously right-handed healthy control subjects age-matched to the stroke patients 3. All subjects must have the ability to reach, grasp and lift the test object with both extremities (stroke patients with the impaired extremity as well) and complete the experimental protocol as assessed by the PI. 4. All subjects must score \> 24 on the Folstein's mini-mental exam to screen out significant cognitive dysfunction 5. Subjects must obtain MRI or CT scan images of their brain taken since their stroke, or be willing to have a structural MRI or CT scan taken as part of this research study. Exclusion Criteria: 1. Presence of clinically significant visual deficits, aphasia, neglect, or apraxia as determined by clinical neurologic examination that may interfere with the research protocol 2. Presence of sensory deficits in control subjects and in the non-involved hand of stroke subjects on testing of two-point discrimination 3. History of surgery or other significant injury to the upper extremities 4. Botulinum toxin injections in the upper extremity musculature in the three months prior to enrollment in the study. 5. Current treatment with intrathecal baclofen 6. Previous neurological illness such as head trauma, prior stroke, epilepsy, demyelinating disease 7. Complicating medical problems such as uncontrolled, diabetes with polyneuropathy, severe renal, cardiac or pulmonary disease, or any other severe concurrent medical problem that will interfere with obtaining reliable results.