Electroencephalography-guided transcranial direct current stimulation improves picture-naming performance

Transcranial direct current stimulation (tDCS) is a potential method for improving verbal function by stimulating Broca's area. Previous studies have shown the effectiveness of using functional magnetic resonance imaging (fMRI) to optimize the stimulation site, but it is unclear whether similar optimization can be achieved using scalp electroencephalography (EEG). Here, we investigated whether tDCS targeting a brain area identified by EEG can improve verbalization performance during a picture-naming task. In Experiment 1, EEG and fMRI data were acquired during a naming task with 21 participants. Comparison of EEG and fMRI data showed overlap in the highest areas of activation for 80% of the participants. In Experiment 2, tDCS was administered to 15 participants using a crossover design, with stimulation targeting the EEG-guided area, Broca's area, and sham conditions. Our findings indicated that tDCS targeting the EEG-guided area significantly improved lexical retrieval speed compared with stimulation over Broca's area and sham conditions. These results support the validity of EEG-based area identification and its use in optimizing the effects of tDCS on improving language function.