Abstract
There is evidence that the human cerebellum is involved not only in motor control but also in other cognitive functions. Several studies have shown that language-related activation is lateralized toward the right cerebellar hemisphere in most people, in accordance with leftward cerebral cortical lateralization for language and a general contralaterality of cerebral–cerebellar activations. In terms of behavior, hand use elicits asymmetrical activation in the cerebellum, while hand preference is weakly associated with language lateralization. However, it is not known how, or whether, these functional relations are reflected in anatomy. We investigated volumetric gray matter asymmetries of cerebellar lobules in an MRI data set comprising 2226 subjects. We tested these cerebellar asymmetries for associations with handedness, and for correlations with cerebral cortical anatomical asymmetries of regions important for language or hand motor control, as defined by two different automated image analysis methods and brain atlases, and supplemented with extensive visual quality control. No significant associations of cerebellar asymmetries to handedness were found. Some significant associations of cerebellar lobular asymmetries to cerebral cortical asymmetries were found, but none of these correlations were greater than 0.14, and they were mostly method-/atlas-dependent. On the basis of this large and highly powered study, we conclude that there is no overt structural manifestation of cerebellar functional lateralization and connectivity, in respect of hand motor control or language laterality.
Highlights
Left–right asymmetries are an important feature of the brains and behavior of humans (Toga and Thompson 2003)
For each structure and participant, asymmetry was measured by an asymmetry index (AI) using the formula (L - R)/ (L ? R) where L stands for left-side volume and R stands for right-side volume
All AIs were adjusted by linear regression for the potential covariate effects of age, estimated intracranial volume (ICV), sex, field strength, scanner type, and their twoway interactions
Summary
Left–right asymmetries are an important feature of the brains and behavior of humans (Toga and Thompson 2003). Left-hemisphere language dominance is one of the most prominently lateralized functional properties of the average human brain (Bethmann et al 2007), while a strong population-level bias in hand preference (roughly 90 % right-handed) is a prominent behavioral lateralization (Hardyck and Petrinovich 1977). Most structural and functional studies of human brain laterality have focused on the cerebral cortex (Toga and Thompson 2003). Hand preference is linked to functional lateralization for motor control around the precentral gyrus (Willems et al 2014), while left-handedness has been tentatively linked with altered structural lateralization of this same cortical region (Amunts et al 1996; Guadalupe et al 2014). Variations in language lateralization and hand preference are subtly related (Knecht et al 2000; Mazoyer et al 2014)
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