Prolonged motor skill learning - a combined behavioural training and theta burst TMS study

Purpose: To assess the behavioural effects of prolonged motor practice in healthy volunteers, and the specific impact of inhibiting different motor-related brain regions in the late phase of motor learning using continuous theta burst transcranial magnetic stimulation (cTBS). Methods: Twelve subjects trained their non-dominant arm in eight arm motor tasks (Arm Ability Training, AAT) once a day for three weeks (16 sessions). During the last four days, training was performed before and after applying cTBS to either M1, S1, SMA, or PMC. Results: The AAT induced substantial and robust motor learning for the trained arm with variations across tasks. Considerable motor learning was also observed in the non-trained dominant arm with remarkably similar variations across tasks, suggesting that practise improved common underlying sensorimotor capacities (abilities) in addition to effector-specific effects. When applied after prolonged training, inhibitory cTBS showed no detrimental effects on motor performance/learning; M1 cTBS even improved performance in a labyrinth task. Conclusions: Prolonged training with the non-dominant arm led to profound motor learning across abilities with transfer to the non-trained dominant arm. Unlike during early stages of motor learning, no detrimental effect of cTBS over M1, S1, PMC, or SMA could be substantiated after prolonged motor practice.