The effects of transcranial direct current stimulation over the dorsolateral prefrontal cortex on cognitive inhibition.

The present study examines the effects of bilateral transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) (anodal over left and cathodal over right DLPFC). This study describes the long-term effects of tDCS on cognitive inhibition, using the Hayling task. Twenty volunteers participated in the study and were assigned to either an active or a sham group. Participants heard sentences with the final word missing. They were asked then to complete the sentence with a word that either is appropriate in the context of the sentence (initiation condition) or is completely unrelated in this specific context (suppression condition). All participants performed a baseline Hayling task followed by six stimulation sessions. Subsequent to completion of these stimulations, we assessed immediately Hayling performance and re-assessed this performance 1 month. The results indicate a significant decrease in the number of errors in the active group, but only in the suppression condition that continued for 1 month after the sixth stimulation. The current findings suggest that tDCS can improve cognitive inhibition for the long-term in healthy adults and that the DLPFC has a special role in selecting the correct response and suppressing irrelevant semantic information.