Changes in cortical, cerebellar and basal ganglia representation after comprehensive long term unilateral hand motor training.

We were interested in motor performance gain after unilateral hand motor training and associated changes of cerebral and cerebellar movement representation tested with functional magnetic resonance imaging (fMRI) before and after training. Therefore, we trained the left hand of strongly right-handed healthy participants with a comprehensive training (arm ability training, AAT) over two weeks. Motor performance was tested for the trained and non-trained hand before and after the training period. Functional imaging was performed for the trained and the non-trained hand separately and comprised force modulation with the fist, sequential finger movements and a fast writing task. After the training period the performance gain of tapping movements was comparable for both hand sides, whereas the motor performance for writing showed a higher training effect for the trained hand. fMRI showed a reduction of activation in supplementary motor, dorsolateral prefrontal cortex, parietal cortical areas and lateral cerebellar areas during sequential finger movements over time. During left hand writing lateral cerebellar hemisphere also showed reduced activation, while activation of the anterior cerebellar hemisphere was increased. An initially high anterior cerebellar activation magnitude was a predictive value for high training outcome of finger tapping and visual guided movements. During the force modulation task we found increased activation in the striate. Overall, a comprehensive long-term training of the less skillful hand in healthy participants resulted in relevant motor performance improvements, as well as an intermanual learning transfer differently pronounced for the type of movement tested. Whereas cortical motor area activation decreased over time, cerebellar anterior hemisphere and striatum activity seem to represent increasing resources after long-term motor training.