Modulation of Muscle Responses Evoked by Transcranial Magnetic Stimulation
During the Acquisition of New Fine Motor Skills.
Pascual-Leone, Alvaro, Nguyet Dang, Leonardo G. Cohen, Joaquim P. Brasil-Neto,
Angel Cammarota, and Mark Hallett.
Human Cortical Physiology Unit, Human Motor Control Section, Medical
Neurology Branch, National Institute of Neurological Disorders and Stroke,
National Institutes of Health, Bethesda, Maryland 20892 (U.S.A.)
APStracts 2:0158N, 1995.
SUMMARY AND CONCLUSIONS
1. We used transcranial magnetic stimulation (TMS) to study the role of
plastic changes of the human motor system in the acquisition of new fine motor
skills. We mapped the cortical motor areas targeting the contralateral long
finger flexor and extensor muscles in subjects learning a one-handed, five-
finger exercise on the piano. In a second experiment, we studied the different
effects of mental and physical practice of the same five-finger exercise on
the modulation of the cortical motor areas targeting muscles involved in the
task. 2. Over the course of 5 days, as subjects learned the one-handed, five-
finger exercise through daily 2-hour manual practice sessions, the cortical
motor areas targeting the long finger flexor and extensor muscles enlarged and
their activation threshold decreased. Such changes were limited to the
cortical representation of the hand used in the exercise. No changes of
cortical motor outputs occurred in control subjects who underwent daily TMS
mapping but did not practice on the piano at all (control group 1). 3. We
studied the effect of increased hand use without specific skill learning in
subjects who played the piano at will for 2 hours each day using only the
right hand but who were not taught the five-finger exercise (control group 2)
and who did not practice any specific task. In these control subjects, the
changes in cortical motor outputs were similar but significantly less
prominent than in those occurring in the test subjects, who learned the new
skill. 4. In the second experiment, subjects were randomly assigned to a
physical practice group, a mental practice group, or a control group. Subjects
in each practice group physically or mentally practiced the five-finger piano
exercise independently for 2 hours daily for 5 days. The control group did not
practice the exercise. All subjects had daily TMS mapping of the cortical
motor areas targeting the long finger flexor and extensor muscles. 5. Over the
course of 5 days, mental practice alone led to significant improvement in the
performance of the five-finger exercise, but the improvement was significantly
less than that produced by physical practice alone. However, mental practice
alone led to the same plastic changes in the motor system as those occurring
with the acquisition of the skill by repeated physical practice. 6. We
conclude that acquisition of the motor skills needed for the correct
performance of a five-finger piano exercise is associated with modulation of
the cortical motor outputs to the muscles involved in the task. This rapid
modulation may occur through an increase of synaptic efficacy in existing
neural circuits (long-term potentiation) or unmasking of existing connections
due to disinhibition. 7. Mental practice alone seems to be sufficient to
promote the modulation of neural circuits involved in the early stages of
motor skill learning. This modulation not only results in marked performance
improvement, but also seems to place the subjects at an advantage for further
skill learning with minimal physical practice.
Received 41 April 1993; accepted in final form 28 April 1995.
APS Manuscript Number J185-3.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.