We have used serial transcranial magnetic stimulation (TMS) mapping of the motor cortical outputs to study the plasticity of the adult human cortex during the acquisition of new motor skills. Learning to perform a five-finger exercise on the piano given strict performance constraints requires several days of practice. Using a MIDI-keyboard and computerized analysis of the subject's performance we have quantified the performance improvement and have correlated it with the changes in cortical output maps demonstrated with daily TMS mapping studies. Acquisition of the new skill is associated with an enlargement of the area of cortical output to the muscles involved in the task and a reduction in the cortical motor threshold for their activation. These changes are significantly greater than those associated with increased use of the involved muscles without associated learning. Continued daily practice after completion of the learning process leads to a return of the size of cortical representation back to baseline over the course of several weeks. In addition, using a different task, the serial reaction time test, which allows to differentiate implicit from explicit learning, we have shown that the change in performance strategy associated with the development of explicit knowledge, correlates with a rapid modulation of motor cortical outputs. These findings suggest that motor learning is associated with plastic changes of motor cortical outputs which do not represent the substrate of skilled performance but rather are primarily related to the learning process itself.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.