Cerebellar vermis is a target of projections from the motor areas in the cerebral cortex

TLDR

The medial cerebellar zone, comprising the vermis and fastigial nucleus, is traditionally linked to whole‑body posture and locomotion and is thought to receive somatic sensory input, whereas the lateral cerebellum is connected to the cerebral cortex. By injecting rabies virus into lobules VB–VIIIB of the vermis and exploiting retrograde trans‑neuronal transport, the authors mapped disynaptic cortical inputs to this region. They discovered dense projections from primary motor cortex and other medial motor areas to the vermis, revealing that lobules VB–VIIIB serve as a cortical‑mediated hub for anticipatory postural control and suggesting that its dysfunction may contribute to dystonia.

Abstract

The cerebellum has a medial, cortico-nuclear zone consisting of the cerebellar vermis and the fastigial nucleus. Functionally, this zone is concerned with whole-body posture and locomotion. The vermis classically is thought to be included within the “spinocerebellum” and to receive somatic sensory input from ascending spinal pathways. In contrast, the lateral zone of the cerebellum is included in the “cerebro-cerebellum” because it is densely interconnected with the cerebral cortex. Here we report the surprising result that a portion of the vermis receives dense input from the cerebral cortex. We injected rabies virus into lobules VB–VIIIB of the vermis and used retrograde transneuronal transport of the virus to define disynaptic inputs to it. We found that large numbers of neurons in the primary motor cortex and in several motor areas on the medial wall of the hemisphere project to the vermis. Thus, our results challenge the classical view of the vermis and indicate that it no longer should be considered as entirely isolated from the cerebral cortex. Instead, lobules VB–VIIIB represent a site where the cortical motor areas can influence descending control systems involved in the regulation of whole-body posture and locomotion. We argue that the projection from the cerebral cortex to the vermis is part of the neural substrate for anticipatory postural adjustments and speculate that dysfunction of this system may underlie some forms of dystonia.