Increased representation of the non-dominant hand in pianists demonstrated by measurement of 3D morphology of the central sulcus

Background
Post-mortem and magnetic resonance imaging (MRI) studies of the central sulcus, as an indicator of motor cortex, have shown that in the general population there is greater representation of the dominant compared to the non-dominant hand. Studies of musicians, who are highly skilled in performing complex finger movements, have suggested this dominance is affected by musical training, but methods and findings have been mixed.

Objective
In the present study, an automated image analysis pipeline using a 3D mesh approach was applied to measure central sulcus (CS) asymmetry on MR images obtained for a cohort of right-handed pianists and matched controls.

Methods
The depth, length, and surface area (SA) of the CS and thickness of the cortical mantle adjacent to the CS were measured in each cerebral hemisphere by applying the BrainVISA Morphologist 2012 software pipeline to 3D T1-weighted MR images of the brain obtained for 15 right-handed pianists and 14 controls, matched with respect to age, sex, and handedness. Asymmetry indices (AIs) were calculated for each parameter and multivariate analysis of covariance (MANCOVA), and post hoc tests were performed to compare differences between the pianist and control groups.

Results
A one-way MANCOVA across the four AIs, controlling for age and sex, revealed a significant main effect of group (P = 0.04), and post hoc analysis revealed that while SA was significantly greater in the left than the right cerebral hemisphere in controls (P < 0.001), there was no significant difference between left and right SA in the pianists (P = 0.634). Independent samples t-tests revealed that the SA of right CS was significantly larger in pianists compared to controls (P = 0.015), with no between-group differences in left CS.

Conclusions
Application of an image analysis pipeline to 3D MR images has provided robust evidence of significantly increased representation of the non-dominant hand in the brain of pianists compared to age-, sex-, and handedness-matched controls. This finding supports prior research showing structural differences in the central sulcus in musicians and is interpreted to reflect the long-term motor training and high skill level of right-handed pianists in using their left hand.