CONNECTIONS BETWEEN THE CEREBELLAR NUCLEUS INTERPOSITUS AND THE VESTIBULAR NUCLEI - AN ANATOMICAL STUDY IN THE RAT

Interposito-vestibular connections were analysed, using the anterograd e and retrograde tracer biotinylated dextran amine. The interposito-ve stibular projections mainly arise from medial portions of the cerebell ar nuclei interpositi anterior (NIA) and posterior (NIP), and reach ea ch of the main vestibular nuclei, ipsilaterally. The highest density o f projections is found throughout nucleus vestibularis lateralis. Fibr es also reach the peripheral part of nucleus superior, the caudal part of nucleus inferior, and the lateral part of nucleus medialis. Some f ibres also reach groups I, x and f. Contralaterally, few fibres reach zones of the vestibular nuclei symmetric to the ipsilateral projection . A small, reciprocal, vestibulo-interposed projection is sent from th e vestibular nuclei onto NIA-NIP. Possible influences of the interposi to-vestibular projections upon the major targets of the vestibular nuc lei, spinal motoneurones and oculomotor neurones, are discussed. (C) 1 997 Elsevier Science Ireland Ltd.