High-definition Transcranial Electrical Stimulation for Upper Extremity Rehabilitation

Inclusion Criteria: \- Sub-Project 1 (Healthy) 1. Adults aged 18 and above. 2. Confirmed right-handedness using the Edinburgh Handedness Inventory. Sub-Project 1 (Post-stroke patients) 1. Aged 18 and above. 2. Diagnosed with stroke. 3. Post-stroke for more than 6 months. 4. Unilateral hemiparesis. Sub-Project 2 (Subacute-stroke patients) 1. Aged 18 and above. 2. Diagnosed with stroke. 3. Stroke occurred between 7 days to 6 months ago. 4. Unilateral hemiparesis. 5. Degree of recovery for proximal and distal movements of the affected upper limb is Brunnstrom stage III to V. 6. No severe muscle spasticity in any segments of the affected upper limb (Modified Ashworth Scale ≤ 2). Exclusion Criteria: \- Sub-Project 1 (Healthy) 1. History of neurological disorders (e.g., stroke, brain tumor, epilepsy), psychiatric disorders (e.g., substance abuse, major depression, schizophrenia, bipolar disorder), or musculoskeletal disorders of the upper limb. 2. Contraindications to transcranial electrical stimulation, including history of epilepsy, atrial fibrillation, presence of metal implants, cardiac pacemakers, convexity skull defects, or increased intracranial pressure. 3. Skin allergies, contact dermatitis, abnormal pain, hypersensitivity to pain, wounds, or ulcers on the head. 4. Participation in other invasive or non-invasive brain stimulation research studies. 5. Pregnancy or lactating women. (If female, must be postmenopausal or surgically sterilized. Fertile women must have a negative pregnancy test result. Fertile female patients engaging in heterosexual intercourse, as well as fertile male patients with fertile female partners, must agree to use effective contraception during the trial period and for 4 months after the last dose of the investigational drug, such as oral contraceptives, dual barrier methods, intrauterine devices, or abstain from sexual intercourse during this period; non-fertile women are those who have undergone bilateral oophorectomy or are postmenopausal.) 6. History of alcohol or substance abuse. 7. Damaged skin at the stimulation site, electrode contact, or device wearing site. 8. Long-term use of central nervous system affecting medications (such as antidepressants, sedatives) or other medications that may affect seizure threshold. 9. Other conditions deemed unsuitable for transcranial electrical or magnetic stimulation by a physician. 10. Affiliation with any research institution/execution unit (e.g., students from NTU, Taipei Medical University). Sub-Project 1 (Post-stroke patients) 1. Contraindications to transcranial electrical stimulation include a history of epilepsy, atrial fibrillation, presence of metal implants, cardiac pacemakers, convexity skull defects, or increased intracranial pressure. 2. Skin allergies, contact dermatitis, abnormal pain, hypersensitivity to pain, wounds, or ulcers on the head. 3. Severe neurological or psychiatric disorders other than stroke (such as major depression, schizophrenia, substance abuse, organic brain diseases, Parkinson's disease, brain tumors). 4. Use of medications that may lower the seizure threshold. 5. Undergoing other invasive or non-invasive brain stimulation therapies. 6. Pregnancy or lactating women. (If female, must be postmenopausal or surgically sterilized. Fertile women must have a negative pregnancy test result. Fertile female patients engaging in heterosexual intercourse, as well as fertile male patients with fertile female partners, must agree to use effective contraception during the trial period and for 4 months after the last dose of the investigational drug, such as oral contraceptives, dual barrier methods, intrauterine devices, or abstain from sexual intercourse during this period; non-fertile women are those who have undergone bilateral oophorectomy or are postmenopausal.) 7. History of alcohol or substance abuse. 8. Damaged skin at the stimulation site, electrode contact, or device wearing site. 9. Long-term use of central nervous system affecting medications (such as antidepressants, sedatives) or other medications that may affect seizure threshold. 10. Other conditions deemed unsuitable for transcranial electrical or magnetic stimulation by a physician. Sub-Project 2 (Subacute-stroke patients) 1. Contraindications to transcranial electrical stimulation include a history of epilepsy, atrial fibrillation, presence of metal implants, cardiac pacemakers, convexity skull defects, or increased intracranial pressure. 2. Skin allergies, contact dermatitis, abnormal pain, hypersensitivity to pain, wounds, or ulcers on the head. 3. Severe neurological or psychiatric disorders other than stroke (such as major depression, schizophrenia, substance abuse, organic brain diseases, Parkinson's disease, brain tumors). 4. Use of medications that may lower the seizure threshold. 5. Other muscle and joint problems affecting upper limb function, such as joint contractures, rheumatoid arthritis, myositis ossificans. 6. Severe cognitive impairment or receptive or global aphasia making it difficult to understand instructions. 7. Hemineglect (including visual, auditory, or sensory neglect). 8. Undergoing other invasive or non-invasive brain stimulation therapies. 9. Pregnancy or lactating women. (If female, must be postmenopausal or surgically sterilized. Fertile women must have a negative pregnancy test result. Fertile female patients engaging in heterosexual intercourse, as well as fertile male patients with fertile female partners, must agree to use effective contraception during the trial period and for 4 months after the last dose of the investigational drug, such as oral contraceptives, dual barrier methods, intrauterine devices, or abstain from sexual intercourse during this period; non-fertile women are those who have undergone bilateral oophorectomy or are postmenopausal.) 10. History of alcohol or substance abuse. 11. Damaged skin at the stimulation site, electrode contact, or device wearing site. 12. Long-term use of central nervous system affecting medications (such as antidepressants, sedatives) or other medications that may affect seizure threshold. 13. Other conditions deemed unsuitable for transcranial electrical or magnetic stimulation by a physician.