Principles of organization of the human cerebellum: macro- and microanatomy

In this chapter, we compare current understanding of the anatomy and functional compartmentation of the human cerebellum with detailed knowledge in nonhuman species. The anatomy of the cerebellum is highly conserved across mammals and comparison of functional data suggests that similar principles of organization also hold true for somatotopy. In particular, there is a dual representation of the limbs in the cerebellar cortex in rat, ferret, cat, monkey, and human. In animals, a key organizing principle of the cerebellum is its division into a series of longitudinally oriented olivocorticonuclear modules that are narrow in the mediolateral axis but extend across multiple cerebellar lobules in the rostrocaudal plane. This contrasts with existing understanding of the human cerebellum that suggests that functional compartmentation is organized mainly at the level of different lobes and lobules. However, advances in spatial resolution of imaging techniques mean we are now able to start to examine whether a longitudinal modular organization is also present within the human cerebellum. This has implications for the diagnosis and future treatment of clinical disorders that involve the cerebellum, since it is possible that variations in symptomatology may relate to this finer grain localization.