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 resting motor threshold and testing motor threshold recorded from an affected upper extremity 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
Crossover
Low intensity focused ultrasound stimulation
DeviceA low-intensity focused ultrasound stimulation
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Treatment groupsSee each treatment group below.
Motor sequence learning
Motor sequence learning (MSL) involves predictive processing that results in the anticipation of each component of a sequence of actions. MSL will produce response times and the MSL measure will be the number of responders (i.e., those with ≥20% reduction in the response time).
Corticospinal excitability
Corticospinal excitability is measured by the peak to peak amplitude of motor evoked potential.
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