Short duration transcranial direct current stimulation (tDCS) modulates verbal memory

Transcranial direct current stimulation (tDCS) is a noninvasive method of modulating cortical excitability. The aim of this study was to investigate the effects of short-duration tDCS (1.6 seconds per trial) on memory performance, and whether the effects were affected by stimulation administered early or late in a trial. Participants memorize words under anodal and cathodal tDCS to the left dorsolateral prefrontal cortex (DLPFC) in two separate sessions in no-stimulation, early stimulation, and late stimulation trials. Early stimulation occurred during word presentation, whereas late stimulation occurred after word presentation. Early anodal tDCS led to significantly better accuracy and speed in a subsequent recognition test compared to anodal late or no-stimulation conditions. Early cathodal tDCS, on the other hand, led to significantly worse accuracy and speed in a subsequent recognition test compared with cathodal late or no-stimulation conditions. The results of this study suggest that short-duration tDCS can modulate memory performance and highlight the importance of period of stimulation.