Quantification and comparison of the neuroarchitecture of deep cerebellar nuclei in the rat and macaque

Abstract

The human cerebellum contains 70% of all neurons in the brain and has expanded considerably in the course of primate and mammalian evolution. This expansion is due to the emergence of the neocerebellum consisting of the cerebellar hemispheres and its output structure, the dentate nucleus. Its function, however, remains something of an enigma to cognitive neuroscience and psychology. The aim of this dissertation is to further our understanding of the processes behind cerebellar evolution by studying the cellular changes in the dentate that led to the specialized human neocerebellum. Our results show that the hypo-scaling of dentate dendrites and excitatory synaptic number would aid and abet a larger number of cerebellar modules in hominoids and humans and could be interpreted as a special miniaturization of the computational units in primate neocerebellum. Our findings shed new light on the special neuroarchitecture of the dentate nucleus and provide a new working hypothesis for the unusual folded and flattened nature of the dentate.