It may be hard to acquire stable sensorimotor rhythm from the affected motor cortex for patient without a response of paretic hand. A few studies suggest two ways to approaching closed-loop therapy: peripherally extracting the residual signals, for example electromyogram (EMG) at proximal muscles (deltoids) and centrally extracting the activity patterns from unaffected hemisphere during attempting to move paretic hand. Therefore, understanding neural signatures of residual upper extremity movement among stroke patients might help in discovering potential therapeutic target and developing tailored brain-computer interface (BCI) therapy. Additionally, 59.4% of stroke patients in acute stage impair at least one somatosensory modality. It remains unclear whether the patient with somatosensory impairment hinder BCI effect.

Investigators will consecutively enroll subacute (1-4 weeks after stroke onset) patients with first-time, unilateral, subcortical stroke and age-matched healthy controls. All participants will carry on 2 sequential experiments. In the first experiment, participants will perform 2 motor tasks using either paretic/nondominant upper extremity or non-paretic/dominant upper extremity, called motor attempt (M) condition or calibration condition. The second experiment contains 3 conditions: cyclic functional electrical stimulation (cFES), cFES during motor attempt (M-cFES), and functional electrical stimulation during brain-computer interface (BCI-FES) in random order. The sensorimotor oscillations from the electroencephalography (EEG), upper extremity sensorimotor function score (Fugl-Meyer test, Action Research Arm test, and Revised Nottingham Sensation Assessment), corticospinal excitability from the transcranial magnetic stimulation (TMS), and resting-state functional and structural neuroimage from magnetic resonance imaging (MRI) will be assessed before and after the final experiment, as well as 3 months after stroke.

Inclusion Criteria:

• first-ever, unilateral infarction or hemorrhage at middle cerebral artery or posterior cerebral artery territory
• early subacute phase of stroke (between 1 and 4 weeks after stroke onset)

Exclusion Criteria:

• electroencephagraphy feature is not usable
• Fugl-Meyer Assessment of Upper Extremity score is over 50
• ataxia
• global aphasia
• concomitant neurological diseases
• psychiatric diseases
• participating in other interventional research during this period
• other conditions might interfere with experiment

Hospitalized participants and healthy controls will be recruited from the Taipei Veterans General Hospital.