Brain morphometry shows effects of long-term musical practice in middle-aged keyboard players

Abstract

To what extent does musical practice change the structure of the brain? In order to understand how long-lasting musical training changes brain structure, 20 male right-handed, middle-aged professional musicians and 19 matched controls were investigated. Among the musicians, 13 were pianists or organists with intensive practice regimes. The others were either music teachers at schools or string instrumentalists, who had studied the piano at least as a subsidiary subject, and practiced less intensively. The study was based on T1-weighted MR images, which were analyzed using deformation-based morphometry. Cytoarchitectonic probabilistic maps of cortical areas and subcortical nuclei as well as myeloarchitectonic maps of fiber tracts were used as regions of interest to compare volume differences in the brains of musicians and controls. In addition, maps of voxel-wise volume differences were computed and analyzed. Musicians showed a significantly better symmetric motor performance as well as a greater capability of controlling hand independence than controls. Structural MRI-data revealed significant volumetric differences between the brains of keyboard players, who practiced intensively and controls in right sensorimotor areas and the corticospinal tract as well as in the entorhinal cortex and the left superior parietal lobule. Moreover, they showed also larger volumes in a comparable set of regions than the less intensively practicing musicians. The structural changes in the sensory and motor systems correspond well to the behavioral results, and can be interpreted in terms of plasticity as a result of intensive motor training. Areas of the superior parietal lobule and the entorhinal cortex might be enlarged in musicians due to their special skills in sight-playing and memorizing of scores. In conclusion, intensive and specific musical training seems to have an impact on brain structure, not only during the sensitive period of childhood but throughout life.

Keywords: DBM; MRI; brain plasticity; cerebral cortex; deformation-based morphometry; long-term musical practice; musicians.

Figure 1

Behavioral results. (A) Raw tapping scores right and left hand and 95% confidence intervals. M1 reached higher scores than M2 and C in both hands. No significant difference was found between M2 and C (p > 0.05). (B) Means and 95% confidence intervals of the tapping indices. M1 and M2 showed significantly lower tapping index means than C, indicating a more symmetric motor performance. (C) Boxplot of the CoMo scores. Only two of the musicians showed co-movements at all (one in each of the subgroups; asterisks). Round circle = outlier within the control group. ^*p < 0.05; ^**p < 0.01; ^***p < 0.001.

Figure 2

Distributions of the estimated daily practice times of both musician groups. M1 musicians had a significantly longer practicing time per day (t-test of the means: p = 0.044).

Figure 3

Visualization of the first and second PCA component. Component 1 (A,B) includes the whole corpus callosum and the thalamic nuclei. In (C) it can be seen that the major constituents of component 2 are the sensorimotor cortices and the right corticospinal tract. Color coding: red to yellow, coefficient of the eigenvalue > 0.1. Dark blue to light blue, coefficient of the eigenvalue < −0.1.

Figure 4

Volume change of M1 musicians compared to controls in the corpus callosum^*. (A) Coronal slice (y = −32). (B) Sagittal slice (x = 8). The significant cluster is located in the isthmus and splenium of the corpus callosum, with few voxels reaching the posterior midbody.

Figure 5

Results from voxel-based and ROI-Analysis are overlaid. Volume increase (red) and volume decrease (blue) in M1 musicians compared to controls from the voxel-based analysis are used for visualization of the ROI results in five coronal slices (height threshold t = 2.03, threshold corresponds with p < 0.05, uncorrected for multiple comparisons). As green curves the contours of the regions used in the ROI-analysis are outlined. The scatterplots display the absolute volume (in cm³) within the three groups in the corresponding regions. Horizontal lines = volume means. Contours: (A) area 3a (somatosensory cortex), (B) entorhinal cortex (EC), (C) corticospinal tract (CT), (D) left area 5Ci (superior parietal lobule), (E) area 4p (primary motor cortex). Red, volume increase; blue, volume decrease.

Figure 6

Volume increase in M1 musicians compared to M2 musicians in the right primary motor cortex (red) with the contour of area 4a (green). (A) Shows a volume increase mainly in the foot region, but also the hand region (Geyer et al., ; B).

Figure 7

Brain volume and behavior. (A) A higher tapping score of the left hand is associated with a greater volume in right area 4p (p = 0.045, R² = 0.102). (B) A slight effect can be seen also within the control group without the correlation analysis reaching significance (p = 0.23, R² = 0.084).