Topographical organisation within the lateral reticular nucleus mossy fibre projection to the c1 and c2 zones in the rostral paramedian lobule of the cat cerebellum.
The organisation of the projection from the principal lateral reticular nucleus (LRN) to the electrophysiologically defined cerebellar cortical c1 and c2 zones within apical folia of the forelimb-receiving area of the rostral paramedian lobule was investigated in cats. In individual experiments, small injections of either of two retrograde tracers, wheat germ agglutinin-horseradish peroxidase or fluorescent-tagged beads, were made into one or the other of the two zones. The mossy fibre projection from the LRN was found to arise almost entirely from the ipsilateral nucleus, primarily from its magnocellular region. In the pars anterior (folia 1-3) of the paramedian lobule, the projection to the c1 zone arose from cells located throughout most of the rostrocaudal extent of the magnocellular LRN, whereas the projection to the c2 zone was from cells in the rostral half of this region. There was also a small projection from cells in the dorsolateral parvicellular LRN to the c2 zone, but there was none to the c1 zone. Double-label experiments showed that, in territories within LRN where overlap occurred, cells that target either zone were intermingled, and, at most, about 9% of cells had axons that branched to innervate both zones. In the pars posterior (folia 4-6), cells targeting the two zones arose from largely overlapping areas throughout both the magnocellular and the dorsolateral parvicellular LRN, although cells targeting the c2 zone appeared to be more restricted in distribution. In addition to these interzonal differences, it was found that the projection to the pars posterior from cells in the parvicellular LRN was stronger than that to the pars anterior, irrespective of the cortical zone injected. Overall, the present study provides evidence that there is at least some topographical organisation within the LRN mossy fibre projection to certain cerebellar cortical zones.
Apps
R
R
Department of Physiology, School of Medical Sciences, University of Bristol, United Kingdom. r.apps@bristol.ac.uk
Trott
J R
JR
D000344:Afferent Pathways / Q000033:anatomy & histology*; D000818:Animals; D001931:Brain Mapping; D002415:Cats; D002531:Cerebellum / Q000033:anatomy & histology* / Q000502:physiology; D006651:Histocytochemistry; D012154:Reticular Formation / Q000033:anatomy & histology*