Effects of Transcranial Direct Current Stimulation on Graph Naming Function and Brain Connectivity in Postinfarction Aphasia Patients: An fMRI Study

Abstract

Introduction: The study aimed to investigate the mechanisms of impairment and recovery in graph naming functions among patients with aphasia due to cerebral infarction. Specifically, the study compared immediate effects of transcranial direct current stimulation (tDCS) treatment in patients at different stages postinfarction: the acute phase (AP) and the recovery period (RP). Methods: Twenty-eight patients were selected, consisting of 16 in the AP and 12 in the RP, along with 18 healthy controls. Both patient groups underwent 2 weeks of tDCS treatment. Posttreatment changes in functional connectivity (FC) within language-related brain regions, as well as in graph naming abilities, were assessed in both patient groups. Results: Both AP and RP groups exhibited significant improvements in graph naming ability following tDCS treatment. Compared to healthy controls, patients showed decreased FC in multiple brain regions of both hemispheres, particularly in the dominant hemisphere. Posttreatment assessments revealed significant increases in FC within the bilateral frontotemporal lobes for both AP and RP groups, and within the bilateral temporo-occipital regions for the AP group. Moreover, the RP group demonstrated decreased FC in the left temporal lobe posttreatment, which had shown increased FC pre-treatment. Conclusions: This study suggests that tDCS can effectively enhance graph naming functions in patients with postinfarction aphasia. The therapeutic effects appear to be mediated by enhancing FC within bilateral frontotemporal lobes.