Transcranial electrical stimulation during wakeful rest can support early memory consolidation in arithmetic learning

• Transcranial electrical stimulation targeting frontal slow-wave oscillations during early memory consolidation. • Stimulation over left dorsolateral prefrontal cortex during wakeful rest after arithmetic learning improves performance. • Early memory consolidation after learning could be a promising time window for stimulation to enhance learning. There is increasing evidence that brief periods of quiet wakeful rest immediately after learning facilitate memory consolidation. Similar to consolidation during sleep, this effect has been assumed to derive from neocortical-hippocampal interactions that are accompanied by slow-oscillating cortical activity. This assumption is supported by studies showing that the magnitude of frontal slow-oscillating activity during quiet wakefulness predicts memory performance and that slow-oscillating transcranial direct current stimulation (so-tDCS) during sleep can enhance memory retrieval. We tested whether so-tDCS supports early memory consolidation when applied during quiet wakeful rest immediately after learning. Fifty-eight adults underwent a novel arithmetic training thatwas followed by 15-minutes quiet wakeful rest, in which participants received either anodal so-tDCS (targeting the left dorsolateral prefrontal cortex) or sham stimulation. Following this, participants were tested on their arithmetic performance. We observed a medium-sized stimulation effect for overall accuracy, consisting of better performance in the so-tDCS group. This result provides first evidence that so-tDCS during quiet wakeful rest might be a mean to support early memory consolidation and, hence, memory performance. However, further research appears necessary to confirm this finding and better understand the effects.