The modifiable neuronal network of the cerebellum

Recent data of neuronal network structures of the cerebellum are reviewed and experimental evidence is presented for the hypothesis that parallel fiber synapses on Purkinje cells retain plasticity which provides a memory device to the cerebellar cortical network. A corticonuclear microcomplex, consisting of a small area of the cerebellar cortex, a small group of cerebellar and vestibular nuclear neurons, and a small group of inferior olive neurons, which are interconnected, is proposed to form a functional unit of the cerebellum. The idea that a corticonuclear microcomplex endows an extracerebellar system with subtle control capabilities such as coordination, prediction, and adaptation-learning is supported with experimental data on the cerebellar control of the vestibulo-ocular reflex.