In their study, Gentner and colleagues demonstrate that brain reorganization due to intensive musical practice leads to different patterns of hand movements. More impressively, the more the patterns of hand movements were biased towards musical practice, the less similar they were to the patterns of hand movements used for daily life activities.
To do so, they performed a principal component analysis on the TMS-evoked movements. In short, PCA identifies the different patterns of movements evoked by TMS, e.g. the thumb and the ring fingers frequently move in synchrony. Appropriate combinations of the extracted patterns can reproduce the TMS-evoked movements quite accurately. How well these patterns can account for the TMS-evoked movements (the quality of reconstruction) is measured by a parameter that describes what percentage of the variability in the TMS evoked movements, can be accounted for by the linear combination of the extracted patterns. Four TMS-evoked movement patterns accounted for more than 90% of the variability of the TMS-evoked movements.
The linear combination of the TMS-evoked movement patterns was also able to account for a substantial amount of the variability of the movements performed during daily life tasks or during musical practice (non-TMS-evoked movements). Reconstruction of finger movements recorded during daily life tasks from TMS-evoked movement patterns did not depend on which group the TMS-evoked movement patterns were taken from, i.e. reconstruction quality of violinist grasping movements from non-musicians or pianists was as good as reconstruction quality of the same movements from violinist TMS-evoked movement patterns. In contrast, the quality of reconstruction of violin playing movements was higher when the TMS-evoked movement patterns were taken from another violinist than from a pianist or a non-musician. All in all, these analyzes show that musicians have instrument specific brain reorganization. At first glance, it appears that brain reorganization did not influence grasping movements, which were deemed too simple. However, further analyzes revealed that brain reorganization impacted daily life grasping movements.
In violinists, reconstruction quality of grasping movements was inversely correlated with reconstruction quality of violin playing movements. In other words, if TMS-evoked movement patterns were very good at reconstructing violin playing movements from one subject, they were poor at reconstructing the grasping movements of the same subject. Thus, the reorganization that facilitates violin playing comes at the cost of efficient representation of grasping movements.
This study provides the first demonstration that brain reorganization elicited by skill learning influences daily life activities in a subtle but real way. It also provides direct evidence for the storage of skills in the primary motor cortex through reorganization.
Gentner, R., Gorges, S., Weise, D., Kampe, K. aufm, Buttmann, M., & Classen, J. (2010). Encoding of Motor Skill in the Corticomuscular System of Musicians. Current Biology, 1-6. doi: 10.1016/j.cub.2010.09.045.
Yarrow, K., Brown, P., & Krakauer, J. W. (2009). Inside the brain of an elite athlete: the neural processes that support high achievement in sports. Nature reviews. Neuroscience, 10(8), 585-96. doi: 10.1038/nrn2672.
Pascual-Leone, A., Nguyet, D., Cohen, L. G., Brasil-Neto, J. P., Cammarota, A., & Hallett, M. (1995). Modulation of muscle responses evoked by transcranial magnetic stimulation during the acquisition of new fine motor skills. Journal of neurophysiology, 74(3), 1037-45
Elbert, T., Pantev, C., Wienbruch, C., Rockstroh, B., & Taub, E. (1995). Increased cortical representation of the fingers of the left hand in string players. Science, 270(5234), 305-7.