The cerebellar projection from the lateral reticular nucleus as studied with retrograde transport of horseradish peroxidase.

The cerebellar projection from the lateral reticular nucleus (NRL) was studied in cats by means of retrograde axonal transport of horseradish peroxidase (the projection to the paramedian lobule was not included, see Brodal, 1975, for afferents to this cortical region). The entire cerebellar cortex and all cerebellar nuclei receive fibres from the NRL. The strongest connection is with the anterior lobe and lobulus VIIIB of the posterior lobe vermis. As concerns the anterior lobe the observations confirm the previous finding by Brodal (1975) that there is a clearcut topical pattern in the nuclear projection to this part of the cerebellum. The observations furthermore show that crus II is the only cerebellar region devoid of fibres from the subtrigeminal part of the NRL. The cerebellar projection from the NRL is bilateral with a heavy ipsilateral preponderance. The large majority of the labeled cells within the NRL are of the small category (less than 25 micrometer in size). This and the other findings are discussed in relation to previous studies on the efferent and afferent connections of the nucleus.