The comparative therapeutic effects and neural mechanisms of dual-site transcranial electrical stimulation combined with cognitive–motor dual-task training (CMDT) in stroke rehabilitation remain insufficiently understood. This study investigated whether dual-target transcranial alternating current stimulation (tACS) or anodal transcranial direct current stimulation (tDCS) applied over the primary motor cortex (M1) and left dorsolateral prefrontal cortex (DLPFC), when combined with CMDT, could improve functional recovery and modulate neural oscillatory networks in stroke survivors. 

In a single-blind, three-arm randomized controlled trial, 72 stroke survivors were randomly assigned to receive 15 sessions of dual-site stimulation (tACS, tDCS, or sham), each combined with CMDT. Behavioral outcomes included cognitive performance (Visual Cognitive Assessment Test, VCAT; Trail Making Test A/B), motor and balance function (Fugl–Meyer Assessment for Lower Extremity, FMA-LE; Berg Balance Scale, BBS), mobility (Timed Up and Go under single and dual-task conditions), and mood (Hamilton Depression Rating Scale, HAMD). Resting-state electroencephalography (EEG) was analyzed to assess theta-band power and phase-locking value (PLV) as indicators of functional network connectivity. Repeated-measures ANOVA with Bonferroni-adjusted post-hoc comparisons was performed, and correlation analyses explored associations between EEG changes and behavioral outcomes. 

 Significant group × time interactions were observed across multiple functional domains. The tDCS + CMDT group demonstrated greater improvements in lower-limb motor function (FMA-LE) compared with both tACS + CMDT and sham groups (p < 0.05), and superior cognitive gains (VCAT) relative to sham (p < 0.05). Both tDCS and tACS groups achieved significantly greater improvements than sham in dual-task mobility (TUG-CMDT) and depressive symptoms (HAMD) (p < 0.001). EEG analysis revealed that tACS induced frequency-specific modulation of theta-band network connectivity, reflected by increased PLV, whereas tDCS produced less frequency-specific changes. Notably, increases in theta PLV were significantly correlated with improvements in balance (BBS), mobility (TUG), and executive function (TMT-B).

Dual-site transcranial electrical stimulation combined with CMDT is a safe and effective strategy for stroke rehabilitation. While anodal tDCS appears to preferentially enhance local motor plasticity and cognitive recovery, tACS modulates large-scale oscillatory network connectivity, with theta-band synchronization emerging as a potential neurophysiological biomarker underlying functional improvements.