Non-invasive, non-pharmaceutical technologies that augment routine clinical practice for brain diseases and manage chronic symptoms have advanced rapidly over the past two decades. Among these, non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) promotes neuroplasticity in injured brains, with fewer side effects and risks than invasive, implanted approaches such as deep-brain stimulation. Stimulating the brain can improve its function and help with recovery after a stroke. It has been a challenge to do this non-invasively. This is because the brain is reshaped after a stroke, and thus, it is difficult to find the right places to stimulate from the outside. In previous research, investigators found that optimal type and target of tDCS varied among subjects. The goal of this pilot trial is to test the feasibility of combining individually optimized, targeted high-definition tDCS (THD-tDCS) with rehabilitation therapy. Investigators will include 16 chronic stroke subjects with their optimal stimulation setup, obtained from their previous research. The participants will be computer-randomized into two equal-sized groups to receive either optimal THD-tDCS or sham stimulation, together with rehabilitation therapy (modified constraint-induced movement therapy, mCIMT) for five sessions over two weeks. Outcome measures will be collected at the baseline and right after the final intervention session. The primary outcome measure will be the change in the FM-UE score from baseline to immediately post the final intervention to assess the immediate effect of the intervention on upper extremity motor impairment. The secondary outcome measure will be the Wolf Motor Function Test time score to evaluate the immediate effect on functional motor performance.

Inclusion Criteria:

• Must be 18 years or older
• Must have had a stroke that resulted in paresis confined to one side. The use of a wheelchair or other assisting devices are not exclusionary.
• Must have substantial motor impairment of the paretic upper limb
• Absence of severe wasting or contracture or significant sensory deficits in the paretic upper limb
• Absence of severe concurrent medical problems (e.g. cardiorespiratory impairment)
• Fugl-Meyer Upper Extremity Score of 8-50 based on assessment performed during the baseline visit.
• Must have had either MRI or CT of the brain performed at Carle as part of their stroke care. Imaging may have been performed either during the diagnostic work-up for stroke or as follow-up after diagnosis. The most recent images from either MRI or CT will be collected for this study.
• Capacity to provide informed consent and participate in English (Since this study is a clinical trial and the team is yet to provide the translation service at this stage, the study is restricted to those who can consent and participate in English only).
• Must be willing and able to perform study procedures

Exclusion Criteria:

• Self-reported sensitive skin or adhesive allergy as assessed by the tDCS Safety Screening Questionnaire
• Has a cardiac pacemaker, defibrillator or an implantable cardiac resynchronization therapy device
• Has metal implants in the head and/or brain
• Presence of muscle tone abnormalities and motor or sensory impairment in the non-paretic limb
• Presence of severe muscle wasting or contracture or significant sensory deficits in the paretic upper limb
• Currently pregnant or planning to become pregnant during the study period
• History of epilepsy, febrile convulsion, recurrent fainting spells or unexplained recurring headaches
• Current use of illicit/recreational drugs
• Currently undergoing anti-malarial treatment. (Note: participants can be considered for study participation after ant-malarial treatment has been discontinued)
• Has known adverse reaction to TMS or tDCS

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Please refer to https://professional.heart.org/en/research-programs/awardee-resources/open-science-policy-statements-for-aha-funded-research for detailed information in term of access criteria