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The results in the male subgroup may suggest microstructural adaptations in the human
cerebellum in response to early commencement and continual practice of complicated
bimanual finger sequences, similar to findings in animal experiments.50,20,22The absence of
an observable effect in the cerebellum in the female subgroup may be due to several
reasons. First, females seem to reach adult cerebellar size much earlier than males during
development.^51 Second, the relative cerebellar volume of females is larger than that of
males, possibly indicating that a ceiling effect might have been reached. Third, synaptic
up-and-down regulation during the female menstrual cycle has been described and could
have diminished a group difference.^52 Fourth, there was a trend for a difference in total
brain volume between female musicians and nonmusicians indicating that other brain
regions outside the cerebellum might show structural differences. This could indicate gen-
der related differences in presumed structural plasticity.
Regional differences in gray matter volume
A voxel-by-voxel morphometric technique was used to detect local differences in gray mat-
ter volume and concentration between musicians and nonmusicians across the entire brain
space (SPM99, Functional Imaging Laboratory, Institute of Neurology, London). This
method involves spatial normalization of all images to the same anatomical space, extract-
ing the gray matter from the normalized images, and analysing group differences in local
concentration of gray matter on a voxel-by-voxel basis.^53 Professional musicians showed
higher gray matter concentrations (Figure 24.5) compared to nonmusicians in the peri-
rolandic region, the premotor region, the posterior superior parietal region, the posterior
mesial perisylvian region bilaterally, and the cerebellum.^54
This study replicates and significantly expands upon our previous studies using more
traditional morphometric techniques describing size and volume differences in the motor
Figure 24.5Preliminary findings of a voxel-by-voxel morphometric study comparing a group of 15 male
musicians with 15 male nonmusicians. Three axial slices show significant differences (p0.05 corrected) between
musicians and nonmusicians superimposed on corresponding T1-weighted structural images. Yellow and red
voxels indicate more graymatter concentration in the musicians, blue voxels indicate more gray matter concen-
tration in the nonmusicians. (See Plate 22 in colour section.)