Patterns of Cerebellar-Cortical Structural Covariance Mirror Anatomical Connectivity of Sensorimotor and Cognitive Networks

The cortex and cerebellum are densely connected through reciprocal input/output projections that form segregated loop circuits. Anatomical studies in primates and imaging studies in humans show that anterior lobules of the cerebellum exhibit denser connections to sensorimotor and parietal cortical regions, while lobules Crus I and II are more heavily connected to prefrontal regions. The cerebellum and cortex develop in tandem in childhood, leading to the hypothesis that individual differences in structure should be related, especially for connected regions. To test this hypothesis we examined covariation between the volumes of anterior sensorimotor and lateral cognitive lobules of the cerebellum and measures of cortical thickness (CT) and surface surface area (SA) across the whole brain in a sample of 270 young, healthy adults drawn from the HCP dataset. We found that patterns of cerebellar-cortical covariance differed between sensorimotor and cognitive networks such that anterior motor lobules of the cerebellum showed greater covariance with sensorimotor regions of the cortex, while lobules Crus I and Crus II showed greater covariance with frontal and temporal regions. Interestingly, cerebellar volume showed predominantly negative relationships with CT and predominantly positive relationships with SA. Individual differences in SA are thought to be largely under genetic control while CT is thought to be more malleable by experience. This suggests that cerebellar-cortical covariation for SA may be a more stable feature, whereas covariation for CT may be more affected by development. Additionally, dissimilarity metrics revealed that the pattern of covariance showed a gradual transition between sensorimotor and cognitive lobules, consistent with evidence of functional gradients within the cerebellum. Taken together, these findings are consistent with known patterns of structural and functional connectivity between the cerebellum and cortex. They also shed new light on possibly differing relationships between cerebellar volume and cortical thickness and surface area. Finally, our findings are consistent with the interactive specialization framework which proposes that structurally and functionally connected brain regions develop in concert. ### Competing Interest Statement The authors have declared no competing interest.