The Cerebellar Nuclei

This chapter, which is largely based on Brodal (1981) and Chan-Palay (1977), is concerned mainly with the lateral (dentate) nucleus, as representative of the cerebellar nuclei, which also include the interpositi (emboliform and globose) and the medial (fastigial) nuclei, the terms in parentheses indicating those for the human cerebellum.

Anatomical Aspects

In humans, there are four distinct cellular masses or nuclei in the white matter of each half of the cerebellum (also termed the deep cerebellar nuclei). Most medial is the fastigial nucleus, followed more laterally by the small globose and emboliform nuclei and, most laterally, the dentate. The dentate nucleus appears in sections as a wrinkled band of gray matter (not unlike the inferior olive) with a medioanteriorly directed hilus. In the rat, cat, monkey, and most mammals, the usually accepted counterparts are the nucleus medialis, nucleus interpositus anterior and posterior, and nucleus lateralis, respectively.

The dentate nucleus is enormous in humans, both in comparison with the other nuclei and in comparison with other species; in fact, it has been estimated to contain some 284,000 cells (see also Heidary and Tomasch 1969). The principal afferent fibers to the cerebellar nuclei are the Purkinje cell axons from the cerebellar cortex, which are inhibitory. Other afferents include collaterals of the climbing and the mossy fibers, which are excitatory. Almost all efferent fibers from the cerebellum are axons of cells in the cerebellar nuclei.