The primary motor cortex (M1) area recruitment enlarges while learning a finger tapping sequence. Also M1 excitability increases during procedural consolidation. Our aim was to investigate whether increasing M1 excitability by anodal transcranial DC stimulation (AtDCS) when procedural consolidation occurs was able to induce an early consolidation improvement. Forty-seven right-handed healthy participants were trained in a nine-element serial finger tapping task (SFTT) executed with the left hand. Random series blocks were interspersed with training series blocks. Anodal or sham tDCS was administered over the right M1 after the end of the training session. After stimulation, the motor skills of both trained and a new untrained sequential series blocks were tested again. For each block, performance was estimated as the median execution time of correct series. Early consolidation of the trained series, assessed by the performance difference between the first block after and the last block before stimulation normalized by the random, was enhanced by anodal and not by sham tDCS. Stimulation did not affect random series execution. No stimulation effect was found on the on-line learning of the trained and new untrained series. Our results suggest that AtDCS applied on M1 soon after training improves early consolidation of procedural learning. Our data highlight the importance of neuromodulation procedures for understanding learning processes and support their use in the motor rehabilitation setting, focusing on the timing of the application.
