Inclusion criteria:  A first ever-stroke≧3 months Baseline Fugl-Meyer assessment of upper extremity scale (FMA-UE) between 18 to 56 (Fugl-Meyer et al. 1975) No excessive muscle spasticity of the affected arm (Modified Ashworth Scale < 3 at any joints of the affected arm) (Bohannon & Smith 1987) Able to follow examiners' commands and study instructions (Mini-Mental State Examination score≧22) (Folstein et al. 1975) No participation in any other experimental rehabilitation or drug studies during period of this project  Exclusion criteria:  Concomitant neurologic, neuromuscular or orthopedic conditions that may interfere with participation of this project Epilepsy within three months