QUANTITATIVE-ANALYSIS OF CUNEOCEREBELLAR PROJECTIONS IN RATS - DIFFERENTIAL TOPOGRAPHY IN THE ANTERIOR AND POSTERIOR LOBES

The distribution of wheatgerm agglutinin-horseradish peroxidase-labell ed messy fibre terminals of internal and external cuneate projections to the cerebellar anterior and posterior lobes were quantitatively ana lysed in adult rats. Computer-based image analysis mapped the spatial distribution of labelled cuneocerebellar terminals in two-dimensional reconstructions of the unfolded cortex. Cuneocerebellar projections ar e mainly ipsilateral in their distribution. Cuneate projections to the anterior lobe vermis-medial paravermis terminate in well-circumscribe d, irregularly-shaped patches. These terminal patches are aligned and form a longitudinally continuous, parasagittally oriented stripe in th e lateral vermis-medial paravermis of lobules I-V. These terminal patc hes represent the topographically organized divergent projections of d ifferent parts of the internal and external cuneate nuclei. Cuneocereb ellar projections to the lateral paravermis-hemisphere, particularly i n the posterior part of lobule V, are organized as a transversely orie nted band of terminals. Cuneocerebellar projections to the posterior l obe terminate mainly in three transversely oriented bands of terminals located al the junction between lobules. An anterior band of terminal s was located in lobule VI anteriorly and was continuous with the band of terminals located in the posterolateral part of lobule V al the ju nction of these two lobules. Intermediate and posterior transversely o riented bands of terminals were located al the VII-VIII and VIII-IX ju nctions, respectively. Cuneocerebellar projections to these three band s largely appear to represent convergent projections from different pa rts of the cuneate nuclei. These findings are discussed in relation to similarly analysed and previously reported findings on the organizati on of lower thoracic-upper lumbar spinocerebellar projections and in t he context of how cuneocerebellar somatosensory input may be different ially organized and processed in disparate areas of the cerebellar cor tex. (C) 1997 IBRO. Published by Elsevier Science Ltd.