differential effects of unihemispheric concurrent dual-site and conventional tdcs on motor learning: a randomized, sham-controlled study

Introduction: based on the literature, unihemispheric concurrent dual-site anodal transcranial direct current stimulation (a-tdcsuhcds) of primary motor cortex (m1) and dorsolateral prefrontal cortex (dlpfc) would be more efficient than conventional a-tdcs of m1 to induce larger and longer-lasting m1 corticospinal excitability. the main objective of the present study was to compare the effects of a-tdcsuhcds and conventional m1 a-tdcs on the extent and durability of the motor sequence acquisition in healthy individuals. methods: in this randomized sham-controlled study, healthy volunteers were randomly divided into three groups: experimental (a-tdcsuhcds), control (m1 a-tdcs), and sham stimulation groups. the participants practiced serial response time task over three consecutive days when they simultaneously received a-tdcs. using the skill measure, we assessed motor learning up to 4 weeks after the completion of experimental conditions. results: data analysis revealed that all groups exhibited the improved trend over the training course (p<0.001). there were no significant differences in skill acquisition among groups at post-intervention (p>0.05), while a significant improvement was observed between experimental and sham group at the retention time (p<0.05). moreover, there were no significant differences between the control and two other groups with regard to the retention time (p>0.05). conclusion: these results revealed a significant increase in the skill acquisition by a-tdcsuhcds technique with regard to retention issue, which could be a valuable finding in neuro-rehabilitation field.