The Dynamic Nature of Neuron Connections: Neuronal Plasticity and Spontaneous Degeneration in the Normal Cerebellum

Abstract

In this detailed analysis of the dentate nucleus, electron microscopy will be used for defining the cytology of the neurons and their processes and the fine synaptic connections between these and axons with extracerebellar origins. A systematic analysis of this type begins with the definition of the most obvious neuronal elements—the perikarya of all neurons, their attached dendrites, large or small, dendritic appendages and thorns, the axonal hillocks and initial segments; then, a catalogue of the synaptic connections upon these receptive surfaces. This was accomplished in two earlier chapters, IV and V. Now, the remaining neuropil is to be analyzed, that mesh-work containing axons and dendrites that are not in continuity with their neurons of origin in thin sections—from any point of view a formidable task. It will be approached by the systematic elimination of the more readily recognized elements in the normal brain, then those identifiable by means of some experimental perturbation such as ablation of a connecting part of the brain.