The use of transcranial direct current stimulation to facilitate motor skill reactivations of a choice reaction time task in adults

Motor skill acquisition involves fast and slow learning phases, typically requiring extended practice. This study explored whether brief reactivations of a choice reaction time (CRT) task, combined with anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1), could yield performance improvements comparable to full-length practice. A total of 120 healthy adults were randomized into six groups varying in tDCS use (2 mA for 5 or 20 min) and practice duration (5 or 20 min). Reaction time (RT) and error rate were assessed across sessions. Across all groups, RT significantly improved from 423.5 ± 116.8 ms at pre-test to 357.9 ± 63.4 ms post-test (p < 0.001), of the first session. RTs at session 4 (377.8 ± 66.2 ms) remained significantly faster than baseline (p < 0.001), though slightly slower than immediate post-test in session 1 (p = 0.172). No significant between-group differences emerged in RT or error rate, though the brief reactivation + tDCS group achieved RTs similar to the full-practice group. When separated by sex, women showed slower reaction times initially and less improvement in reaction times with practice. These results suggest that brief, tDCS-enhanced reactivations can preserve behavioral improvements in learning, though their neurophysiological effects remain inconclusive.