Posttraining anodal tDCS improves early consolidation of visual perceptual learning

We aimed to investigate the transcranial direct current stimulation (tDCS)-induced facilitation of early consolidation over a period of extended training sessions and explored the effect of tDCS on visual perceptual learning (VPL) improvement during online learning and offline consolidation.In the current double-blind sham-controlled study, twenty-four healthy participants were trained on coherent motion direction identification for 5 consecutive sessions. Performance was assessed at the pre- and posttests. Anodal or sham tDCS of the left human middle temporal region (hMT+) was applied immediately after the completion of daily training (termed early consolidation).The magnitude of improvement between anodal and sham tDCS was marginally significant, supporting the beneficial effect of anodal tDCS on VPL by stimulating early consolidation. Additionally, anodal tDCS induced a larger improvement between the first two training sessions than sham tDCS. No effect of anodal tDCS was found on the within-session improvement.The above results indicated that anodal tDCS facilitates offline consolidation during the early period of the whole training series, not online learning. The possible neural mechanisms and limitations (sample size and persistent effects) were discussed.Our findings support the use of the combination of tDCS and behavioral training in facilitating visual rehabilitation and contribute to a deeper understanding of learning processes by neuromodulation procedures.