The effect of transcranial direct current stimulation on motor sequence learning and upper limb function after stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Neuromodulation

Background:

• Stroke survivors often experience upper limb impairment, impacting daily function.
• Transcranial direct current stimulation (tDCS) is explored as a tool to enhance motor recovery.
• Understanding optimal electrode configuration is crucial for tDCS efficacy.

Purpose of the Study:

• To evaluate how different tDCS electrode arrangements affect stroke survivors' hand function and motor learning.
• To investigate if changes in transcallosal inhibition (TCI) correlate with functional improvements after tDCS.

Main Methods:

• 24 stroke survivors with upper limb impairment underwent blinded tDCS (anodal, cathodal, bihemispheric, sham) during a motor sequence learning task.
• Hand function was assessed using the Jebsen Taylor hand function test (JTT) pre- and post-stimulation.
• Transcallosal inhibition (TCI) was measured via ipsilateral silent period (iSP) duration using transcranial magnetic stimulation.

Main Results:

• Motor sequence learning occurred irrespective of tDCS condition.
• Jebsen Taylor hand function test (JTT) scores significantly improved after unilateral tDCS (anodal or cathodal) compared to sham.
• Bihemispheric tDCS did not yield significant improvements in JTT performance.
• No significant effect of tDCS on transcallosal inhibition (TCI) was observed.

Conclusions:

• Unilateral tDCS effectively improves hand function (JTT performance) in stroke survivors.
• tDCS did not enhance motor sequence learning in this cohort.
• Findings suggest unilateral electrode placement is more beneficial for functional hand recovery than bihemispheric approaches in stroke.