300 Section - The Effects of γ- Transcranial Alternating Current Stimulation on Upper Limb Motor Recovery in Stroke Patients: A Pilot Randomized Control Trial

Objectives : To evaluate whether γ-transcranial alternating current stimulation (γ-tACS) over the ipsilesional primary motor cortex improves post-stroke upper-limb motor impairment and to explore its electrophysiological correlates using quantitative EEG (QEEG).

Design: Randomized, double-blind, sham-controlled pilot trial. Patients with first-ever unilateral stroke (2 weeks–6 months) and upper-limb hemiparesis were randomized to 70 Hz γ-tACS or sham. Both groups received conventional rehabilitation. Outcomes were assessed pre/post using the Fugl–Meyer Assessment Upper Extremity (FMA-UE) and Modified Barthel Index (MBI). Resting EEG was analyzed for band relative power, slow-to-fast ratios (DAR, DBR, DTABR), and beta-band functional connectivity (wPLI).

Results: Both groups improved, but γ-tACS yielded a larger FMA-UE gain (4.64±4.55 vs 1.67±3.27; P=0.039). Baseline EEG showed pathological lateralization with higher ipsilesional delta power, lower alpha power, and increased DAR/DBR/DTABR (all P< 0.05). After intervention, γ-tACS reduced ipsilesional delta power and decreased DBR and DTABR (all P< 0.05), while sham showed no comparable band-power changes. γ-tACS increased beta-band wPLI between FC3 and C3 (P< 0.05). Delta and DTABR reductions and wPLI increases correlated with FMA-UE improvement (all P< 0.05).

Conclusion: γ-tACS over ipsilesional M1 may enhance upper-limb motor recovery after stroke. QEEG indices and beta-band connectivity changes track behavioral gains, supporting rhythm restoration and network strengthening as candidate mechanisms.