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.
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
Patients diagnosed with posterior circulation infarction
Unable to follow commands due to poor cognitive function
Unilateral neglect
Homonymous hemianopia
Parallel
tDCS
Other intervention* Stimulation type: Anodal stimulation * Electrode size: 5x7cm * Stimulation target: C3/C4 primary motor cortex (M1) based on the 10-20 international electroencephalography system * Stimulation intensity: 2 mA * Stimulation current density: 0.029-0.057 mA/cm2 Use tDCS with two saline-soaked surface sponge electrodes (5x7cm) applied to the scalp, secured with a headband. Stimulation intensity is set to 2mA, with 30s ramping up at the start and 30s ramping down at the end of stimulation.
Action Observation Therapy (AOT)
Other interventionParticipants watch selected videos based on muscle grading of triceps, which include functional movement patterns and daily activity tasks of the upper limb. These videos are presented through a computer or mobile screen positioned at an appropriate distance from the participant to allow ample space for performing the required movements.
Motor Evoked Potentials (MEPs)
Peak-to-peak amplitude of motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS) and recorded via surface electromyography (EMG) from hand muscles of the paretic upper limb. Assessment Method: * TMS delivers single pulses over ipsilesional primary motor cortex (M1 hand area) * Surface EMG electrodes record responses from first dorsal interosseous (FDI), abductor pollicis brevis (APB), and extensor carpi radialis (ECR) muscles * Motor hotspot identified (optimal scalp location producing largest MEPs) * Resting motor threshold determined * 15-20 MEPs recorded at 120% of resting motor threshold * Inter-stimulus interval: 5-7 seconds * MEP amplitude measured as peak-to-peak voltage in millivolts (mV)
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