This study investigates the neurophysiological mechanisms underlying the combined use of transcranial direct current stimulation (tDCS) and action observation therapy (AOT) for hand motor recovery in individuals with stroke. Background: While both tDCS and AOT have shown promise individually for stroke rehabilitation, the neural mechanisms of their combined effects remain unclear. Understanding these mechanisms could optimise rehabilitation protocols and improve functional outcomes. Intervention: Participants will receive 10 sessions of anodal tDCS over the ipsilesional motor cortex combined with AOT over two weeks in a clinical setting, followed by 8 weeks of home-based AOT practice. Control groups will receive tDCS alone or AOT alone. Neurophysiological changes will be assessed using motor evoked potentials (MEPs) to evaluate corticospinal excitability. Clinical hand function will be assessed using standardised outcome measures. Measurements: Assessments will be conducted at baseline, during intervention (week 2), and after the home practice phase (week 10) to evaluate neuroplastic changes. Significance: This study will provide mechanistic insights into how neuromodulation and observational learning interact to promote motor recovery, informing evidence-based rehabilitation strategies for stroke survivors in Malaysia and globally. Study Design: Randomised controlled trial with three parallel arms, recruiting 60 participants with chronic stroke from Sabah, Malaysia.

The participation duration for each participant is 10 weeks, including the assessment period.

Group 1 tDCS + AOT (intervention): tDCS will be administered at the outpatient clinic for 20 minutes per session, for a total of 10 sessions over two consecutive weeks. During the tDCS sessions, each participant will engage in AOT for 30 minutes under the supervision of a therapist. Subsequently, each participant will continue performing AOT at home for 30 minutes per session, once a day, five days per week, for 8 consecutive weeks.

Group 2 tDCS alone (control): tDCS will be administered at the outpatient clinic for 20 minutes per session, for a total of 10 sessions over two consecutive weeks. During the tDCS sessions, each participant will watch a landscape video for 30 minutes. Subsequently, each patient will continue watching the landscape video at home for 30 minutes per session, once a day, five days per week, for 8 consecutive weeks.

Group 3 AOT alone (control): placebo tDCS will be administered at the outpatient clinic for 20 minutes per session, for a total of 10 sessions over 2 consecutive weeks. During the placebo tDCS sessions, each participant will engage in AOT for 30 minutes under the supervision of a therapist. Following the clinic sessions, each patient will continue performing AOT at home for 30 minutes per session, once a day, five days per week, for 8 consecutive weeks.

The principal investigator will visit each research site throughout the duration of the study. All participants will attend the outpatient rehabilitation setting five times a week for 30 minutes per session, for 2 consecutive weeks, and continue intervention at home for five days a week for 8 consecutive weeks. The total intervention duration consists of 10 consecutive weeks. For each session in the hospital, there will be a physiotherapist to monitor participants' compliance with the interventions and to ensure that the training is conducted as per protocol. Level of participation would be measured by Rating of Perceived Exertion Scale of 3-5 (light activity to somewhat hard). If the subject attended the session but refuse to participate in the intervention, the subject would be excluded from the study.

Inclusion Criteria:

• Adults aged 18 to 59 years
• Single episode of unilateral stroke and weakness in hand muscles 6 to 24 months post-stroke
• No excessive spasticity of the upper limb, defined as grade two or less on Modified Ashworth Scale

Exclusion Criteria:

• Patients diagnosed with posterior circulation infarction
• Unable to follow commands due to poor cognitive function
• Unilateral neglect
• Homonymous hemianopia
• Other existing neurological disorders that lead to poor hand function
• Grade four or five hand muscle strength.