The goal of this research study is to optimize the parameter of Low-Intensity Focused Ultrasound Stimulation (LIFUS) that is most effective in changing cortical excitability and motor learning skills in patients who suffered a stroke. The researchers hope to answer two questions.
* with increasing power, would LIFUS be more effective? * with the same power, what LIFUS timing is the best
For Aim 1, the study will compare 8, 4 W/cm\^2 to a zero(sham) stimulation to see if higher power is the better.
For Aim 2, the study will compare 500 vs 1000 vs 2000 Hz "timing" to see which one is better.
age >=21 years old of any gender or race
First-ever ischemic or hemorrhagic stroke (neuroimaging verified) at least 6 months from the stroke onset of symptoms
Unilateral arm weakness measured by the Fugl-Meyer Upper-Extremity Scale ≤ 62/64
Inducible rest motor threshold and testing motor threshold recorded from the affected abductor pollicis brevis muscle
Bilateral strokes (infarcts and/or hematoma)
Other co-existent neuromuscular disorders affecting upper extremity motor impairment
History of medically uncontrolled depression or other neuropsychiatric disorders despite medications either before or after a stroke that may affect the subject's ability to participate in the study
History of confirmed dementia or taking dementia drugs
6
Treatment groupsSee each treatment group below.