Fig. 1.

Study design for the single and dual transcranial direct current stimulation (tDCS). The single tDCS applied anodal tDCS over the left inferior frontal gyrus (IFG) and reference electrode over the left buccinators muscle. The dual tDCS was conducted with 1) anodal tDCS over the left IFG and cathodal tDCS over the left buccinators muscle and 2) cathodal tDCS over the right IFG and anodal tDCS over the right buccinators muscle. All subjects were assessed with the Korean-Boston Naming Test (K-BNT) and the verbal fluency (VF) test before and immediately after stimulation.