Axonal trajectories of single climbing and mossy fiber neurons in the cerebellar cortex and nucleus

Abstract

A major factor in determining the function of a particular cerebellar cortical region depends upon its afferent and efferent connections. Two distinct afferent pathways convey information to the cerebellar cortex: climbing fibers and mossy fibers. A large amount of fundamental knowledge about afferent projections to the cerebellum from various precerebellar nuclei has been accumulated by using new anatomical methods, but the axonal trajectories of single climbing fiber neurons in the inferior olive and single mossy fiber neurons of multiple sources have not been well understood. The knowledge about the morphologies of single mossy fiber neurons and climbing fiber neurons in the cerebellum is essential for our understanding of the function of the cerebellum. This article will describe and compare the entire axonal trajectories of single olivocerebellar (OC) neurons and single mossy fiber neurons from the lateral reticular nucleus, pontine nucleus and dorsal column nucleus in the cerebellar cortex and nucleus. Furthermore, this chapter will deal with the relationship between the longitudinal cortical and nuclear compartmentations revealed by aldolase C expression and the longitudinal bands of cortical and nuclear axonal terminals of single climbing fiber neurons and single mossy fiber neurons, and discuss the functional significance of these organizations to generate the final output from the cerebellar nucleus to the targets outside the cerebellum for control of movement and other functions.