Improvement in naming with tDCS and alteration of functional connectivity in post-stroke aphasia: a randomized controlled trial

This study aimed to investigate the effects of anodal transcranial direct current stimulation (A-tDCS) over the left Sylvian parietal temporal region (SPT) on picture naming and auditory comprehension, as well as changes in brain functional connectivity in post-stroke aphasic patients. This is a double-blind, sham-controlled, randomized controlled study. Sixty aphasic patients were randomly assigned to receive either active or sham tDCS over the SPT as well as speech-language therapy for four weeks. Standardized aphasia assessments and electroencephalogram (EEG) examinations were conducted before and after the treatment. The EEG nonlinear index of cross approximate entropy (C-ApEn) was used to assess brain functional connectivity. The tDCS group demonstrated significantly greater improvements than the control group in both picture naming and auditory word-picture identification scores ( p < 0.001). Regression analysis revealed that the group (tDCS/control) was the primary factor associated with improving picture naming. The functional connectivity of F3-P3, F7-P3, T3-T5, T5-P3, T5-C3, T4-T6, T3-T4, and T5-T6 significantly increased following tDCS. Anodal tDCS over the left SPT can improve picture naming and auditory comprehension in subacute post-stroke aphasia. Potential mechanisms include enhanced connectivity within the left-hemisphere dorsal/ventral streams, the executive control network, and between the bilateral temporal lobes. These functional connectivity changes provide neural evidence for the effect of tDCS on naming improvement. Clinical trial registry number ChiCTR-TRC-14005072