Online stimulation of the prefrontal cortex during practice increases motor variability and modulates later cognitive transfer: a randomized, double-blinded and sham-controlled tDCS study

Background: The benefits of learning a motor skill extend to improved task-specific cognitive abilities. The mechanistic underpinnings of this motor-cognition relationship potentially rely on overlapping neural resources involved in both processes, an assumption lacking causal evidence. Objectives: We hypothesize that interfering with prefrontal networks would affect concurrent motor skill performance, long-term learning and associated cognitive functions dependent on similar networks (transfer). Methods: We conducted a randomized, double-blinded, sham-controlled brain stimulation study using transcranial direct current stimulation (tDCS) in young adults spanning over three weeks to assess the role of the prefrontal regions in learning a complex balance task and long-term cognitive performance. Results: Balance training combined with active tDCS led to higher performance variability in the trained task as compared to the sham group, without affecting the learning rate. Furthermore, active tDCS also positively impacted performance in untrained motor and cognitive tasks. Conclusion: The findings of this study help ascertaining the networks directly involved in learning a complex motor task and its implications on cognitive function. Hence, opening up the possibility of harnessing the observed frontal networks involved in resource mobilization in instances of aging, brain lesion/injury or dysfunction. Keywords. Motor learning, prefrontal cortex, Transcranial direct current stimulation, transfer effects, cognition. ### Competing Interest Statement The authors have declared no competing interest.