Post-stroke sensorimotor recovery largely depends on ipsilesional and interhemispheric motor circuit reorganization. Transcranial direct current stimulation (tDCS) may be used to enhance after-effects of rehabilitation through membrane polarization modulation. In this double-blind, crossover randomized controlled trial, we aim to investigate whether single-session, bihemispheric tDCS to the primary motor cortex (M1) in combination with upper extremity rehabilitation therapy modulates ipsilesional motor circuit excitability using transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) measures.

We will consecutively enroll subacute (2-4 weeks after stroke onset) patients with first-time, unilateral, ischemic subcortical stroke in the middle cerebral artery territory with mild to moderate hand weakness. All subjects will be assessed for baseline upper extremity motor function (Fugl-Meyer test and Action Research Arm test), structural and functional magnetic resonance imaging (fMRI). A single session of bihemispheric tDCS (anodal tDCS to ipsilesional M1 and cathodal tDCS to contralesional M1 with 2 mA stimulation for 20 min) or sham tDCS (same but stimulation for only 2 min) with simultaneous physical/occupational therapy will be tested in each subject with a randomized sequence on different days (at least two days apart from each other). All stroke patients will receive standard medical and rehabilitation treatments during the study period. Changes in corticospinal excitability and transcallosal inhibition from the TMS study, as well as sensorimotor oscillations, MEG source projection, and functional connectivity from the task-related MEG will be assessed immediately before and after intervention.

Inclusion Criteria:

• subacute (2-4 weeks after stroke onset) patients
• first-time, unilateral, ischemic subcortical stroke in the middle cerebral artery territory
• mild to moderate hand weakness (MRC 2-4/5)

Exclusion Criteria:

• cerebral cortex lesions
• containing metal implants (such as implanted electrodes, pacemakers)
• sensitive or fear of electromagnetic waves
• pregnant women
• history of alcohol or drug abuse
• history of seizures or epilepsy EEG recording
• other significant disease or neuropsychiatric disorders
• claustrophobia
• fixed dentures over two or more (enough to interfere with MEG signals)