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

OBJECTIVE: 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 post-infarction: the acute phase and the recovery period.

METHODS: Twenty-eight patients were selected, consisting of 16 in the acute phase (AP) and 12 in the recovery period (RP), along with 18 healthy controls. Both patient groups underwent two weeks of tDCS treatment. Post-treatment 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 functional connectivity in multiple brain regions of both hemispheres, particularly in the dominant hemisphere. Post-treatment assessments revealed significant increases in functional connectivity 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 functional connectivity in the left temporal lobe post-treatment, which had shown increased functional connectivity pre-treatment.

CONCLUSIONS: This study suggests that tDCS can effectively enhance graph naming functions in patients with post-infarction aphasia. The therapeutic effects appear to be mediated by enhancing functional connectivity within bilateral frontotemporal lobes.