Figure 1.

(A) Illustrates the design of the present study. tDCS was ramped up prior to the start of the resting-state scan during all stimulation conditions. During sham-tDCS the current was ramped down after 30 s (before scanning commenced). During both active stimulation conditions (anodal- and dual-tDCS), it continued until after the end of the word-retrieval task (red square; only data acquired during the word-retrieval task is reported). (B) Surface rendering illustrates the location of the electrodes during the two active stimulation conditions on the scalp: upper row shows anodal-tDCS montage; lower row shows dual-tDCS montage. Please note, the larger size of the reference electrode (cathode) during anodal-tDCS renders the stimulation over the supraorbital cortex functionally ineffective. R = right hemisphere, L = left hemisphere. C = Cathode, A = Anode. (C) Surface rendering of activity patterns elicited by semantic word-retrieval vs. motor speech trials during the three stimulation conditions. Overall, as in previous studies that used the same task, this contrast elicited mainly activity in bilateral lateral frontal and medial frontal and premotor regions. Right column = Left hemisphere, Left column = Right hemisphere. All contrasts were thresholded at p < 0.05, family-wise-error corrected at voxel and cluster levels.