Stroke is the leading cause of disability in the United States, producing motor impairments that compromise performance of valued activities. Hemiparesis (or weakness in one arm) is particularly disabling, is the primary impairment underlying stroke-related disability, and the most frequent impairment treated by therapists in the United States. This study will test efficacy of a promising technique in reducing arm disability and increasing function, thereby improving outcomes and health, reducing care costs, for community dwelling patients with stroke-induced hemiparesis.

Inclusion Criteria:

• a Fugl-Meyer score > 27, which is indicative of minimal to moderate arm impairment;
• stroke experienced > 6 months prior to study enrollment;
• minimal cognitive impairment, a score > 25 on the Folstein Mini Mental Status Examination (MMSE);
• age > 21 years old and < 80 years old;
• have experienced one clinical stroke as verified by a physician;
• discharged from all forms of physical rehabilitation targeting the affected arm.

Exclusion Criteria:

• < 21 years old;
• excessive pain in the affected hand, arm or shoulder, as measured by a score > 5 on a 10-point visual analog scale;
• excessive spasticity in the affected biceps, triceps, wrist, or fingers, as defined as a score of greater than or equal to 2 on the Modified Ashworth Spasticity Scale;
• currently participating in any experimental rehabilitation or drug studies targeting UE;
• mirrors movements(i.e., involuntary movements by the unaffected hand during attempts at unilateral movement by the stroke-affected hand during attempts at unilateral movement by the stroke-affected hand);
• history of parietal stroke (because some data suggest that ability to estimate manual motor performance through mental imagery is disturbed after parietal lobe damage);
• affected arm joint restriction that in the opinion of the investigator would hinder study participation