A Proposed Functional Significance of Parvicellular Regions of the Lateral and Medial Cerebellar Nuclei

Abstract

Ventral (V) portions of the lateral (NL) and medial (NM) cerebellar nuclei contain a predominant population of small cells which have been tentatively designated as subnuclei in the cat by FLOOD and JANSEN. Based on their afferent and efferent connections, it is suggested that the V-NL and V-NM represent relay centers for cerebellar and vestibular regulation of extraocular movement. The V-NL receives input from the flocculonodular cortex as well as primary and secondary vestibulocerebellar fibers and projects directly to the oculomotor and trochlear complexes via the ascending limb of the brachium conjunctivum. The V-NM may be a relay center for indirect influence on the oculomotor, trochlear and abducens motor nuclei since it projects to these cell groups following relay of its output through the superior and medial vestibular nuclei. These observations do not exclude the possibility that other areas of the NL and/or NM may also influence eye movement, or that V-NL and V-NM may relay data in addition to that proposed.