From The Brain that Changes Itself, a fascinating book about brain plasticity:
He would study the way thoughts change the brain by using TMS to observe changes in the finger maps of people learning to play the piano. One of Pascual-Leone’s heroes, the great Spanish neuroanatamist and Nobel laureate Santiago Ramon y Cajal, who spent his later life looking in vain for brain plasticity, proposed in 1894 that the “organ of thought is, within certain limits, malleable, and perfectible by well-directed mental exercise.” In 1904 he argued that thoughts, repeated in “mental practice”, must strengthen the existing neuronal connections and create new ones. He also had the intuition that this process would be particularly pronounced in neurons that control the fingers in pianists, who do so much mental practice.
Ramon y Cajal, using his imagination, had painted a picture of a plastic brain but lacked the tools to prove it. Pascual-Leone now thought he had a tool in TMS to test whether mental practice and imagination in fact lead to physical changes.
The details of the imagining experiment were simple and picked up Cajal’s idea to use the piano. Pascual-Leone taught two groups of people, who had never studied piano, a sequence of notes, showing them which fingers to move and letting them hear the notes as they were played. Then members of one group, the “mental practice” group, sat in front of an electric piano keyboard, two hours a day, for five days, and imagined both playing the sequence and hearing it played. A second “physical practice” group actually played the music two hours a day for five days. Both groups had their brains mapped before the experiment, each day during it, and afterward. Then both groups were asked to play the sequence, and a computer measured the accuracy of their performances.
Pascual-Leone found that both groups learned to play the sequence, and both showed similar brain map changes. Remarkably, mental practice alone produced the same physical changes in the motor system as actually playing the piece. By the end of the fifth day, the changes in motor signals to the muscles were the same in both groups, and the imagining players were as accurate as the actual players were on the third day.
The level of improvement at five days in the mental practice group, however substantial, was not as great as in those who did physical practice. But when the mental practice group finished its mental training and was given a single two-hour physical practice session, its overall performance improved to the level of the physical practice group’s performance at five days. Clearly mental practice is an effective way to prepare for learning a physical skill with minimal physical practice.
As I said, a really fascinating book and worth checking out.