Cerebellum: Anatomy and Function

Abstract

The cerebellum is the largest motor structure in the CNS and, in humans, contains more neurons than the whole of the cerebral cortex. It occupies about one-tenth of the skull cavity, sitting astride the brain stem beneath the occipital cortex (Fig. 1). A great deal is now known about its circuitry and cell physiology. It contains only six main cell types and is one of the most regularly organized structures in the CNS, having a repeated, almost crystalline form. Thus, input signals to each point on the cerebellar cortex that arise from other parts of the CNS are likely to be processed in the same way and are then output from the cerebellum to specific targets. In other words, the cerebellum performs similar processes on different signals. The cerebellum has also been conserved across vertebrate evolution. There must be good reasons for maintaining such a massive parallel neural structure, but despite its prominent architecture and some clear symptoms of its malfunction, the exact role of the cerebellum is still far from clear. This challenge has attracted a great number of scientists to study it, and the cerebellum is also remarkable for the number of theories put forward to account for its function.