Relationship between interhemispheric inhibition and bimanual coordination: absence of instrument specificity on motor performance in professional musicians

Functional reorganization in a musician's brain has long been considered strong evidence of experience-dependent neuroplasticity. Highly coordinated bimanual movements require abundant communication between bilateral hemispheres. Interhemispheric inhibition (IHI) is the communication between bilateral primary motor cortices, and there is beginning evidence to suggest that IHI is modified according to instrument type, possibly due to instrument-dependent motor training. However, it is unknown whether IHI adaptations are associated with non-musical bimanual tasks that resemble specific musical instruments. Therefore, we aimed to investigate the relationship between IHI and bimanual coordination in keyboard players compared with string players. Bimanual coordination was measured by a force tracking task, categorized as symmetric and asymmetric conditions. Ipsilateral silent period (iSP) was obtained using transcranial magnetic stimulation to index IHI in both left (L) and right (R) hemispheres. Canonical correlation analysis was performed to identify linear relationships between the IHI and bimanual coordination outcomes. There was no difference in bimanual coordination outcomes between keyboard and string players. Increased iSP from the L to R hemisphere was found in string players compared to keyboard players. There appeared to be different instrument-dependent relationships between IHI and bimanual coordination, regardless of symmetric or asymmetric task. Laboratory motor assessments resembling specific features of musical instruments (symmetric vs. asymmetric hand use) did not distinctly characterize bimanual motor skills between keyboard and string players. The relationships between IHI and bimanual coordination in these two instrument types were independent of task condition. Instrument-dependent neuroplasticity may be evident only within the context of musical instrument playing.