Congress of the ECSS edition:17 location:Bruges date:4-7 July 2012
Anodal transcranial Direct Current Stimulation (tDCS) applied to the human primary motor cortex (M1) proves to have beneficial effects on motor skill learning in both: healthy controls [1–2] and patients [3-4]. However, it remains unclear whether tDCS improves motor learning in a general manner or whether there is a task-specific effect. In this study, we tested the effect of tDCS in two different motor tasks: (1) explicit sequence learning and (2) visually guided force control task. Our hypothesis was that anodal tDCS would lead to greater motor learning in both tasks, with these improvements being task-dependent.
Thirty-two healthy subjects participated in this double-blind, sham-controlled cross-over designed study. All subjects were randomly assigned to an anodal-tDCS group or sham-group. We applied tDCS over the primary motor cortex (M1) while subjects performed the motor task. Two different sessions (session interval>1 month) were performed, with the task-order randomized across participants. Motor training of each task consisted of 20 min training for 3 continuous days. Retention tests were performed on the final training day and one week after the training.
Learning scores were calculated and compared using a mixed model ANOVA analysis. The results showed that for both tDCS groups there was an overall improvement of scores across training (**p<0.001). Anodal tDCS showed more improvement compared to sham, in both motor tasks, but not to a significant level. In the explicit sequence task, a significant interaction between the TIME of stimulation (pre, training, post, RT) and TYPE of stimulation (anodal/sham) was found (p=0.01), with the greatest improvement by anodal tDCS being at the 20 min retention test (p=0.01). On the other hand, the visually guided control motor task showed the greatest improvement in the 1 week retention test (p=0.03).
This findings suggest that anodal tDCS does lead to an increase in motor learning most likely by improving consolidation. Further, the exact expression of this effect seems to be dependent on the motor task itself.