Effects of long-term practice and task complexity in musicians and nonmusicians performing simple and complex motor tasks: implications for cortical motor organization.

Motor practice induces plastic changes within the cortical motor system. Whereas rapidly evolving changes of cortical motor representations were the subject of a number of recent studies, effects of long-term practice on the motor system are so far poorly understood. In the present study pianists and nonmusicians were investigated using functional magnetic resonance imaging. Both groups performed simple and complex movement sequences on a keyboard with the right hand, the tasks requiring different levels of ordinal complexity. The aim of this study was to characterize motor representations related to sequence complexity and to long-term motor practice. In nonmusicians, complex motor sequences showed higher fMRI activations of the presupplementary motor area (pre-SMA) and the rostral part of the dorsal premotor cortex (PMd) compared to simple motor sequences, whereas musicians showed no differential activations. These results may reflect the higher level of visuomotor integration required in the complex task in nonmusicians, whereas in musicians this rostral premotor network was employed during both tasks. Comparison of subject groups revealed increased activation of a more caudal premotor network in nonmusicians comprising the caudal part of the PMd and the supplementary motor area. This supports recent results suggesting a specialization within PMd. Furthermore, we conclude that plasticity due to long-term practice mainly occurs in caudal motor areas directly related to motor execution. The slowly evolving changes in M1 during motor skill learning may extend to adjacent areas, leading to more effective motor representations in pianists.