ON THE CAUDAL EXTENSION OF THE X-ZONE IN THE CEREBELLAR CORTEX OF THERAT

Following a selective injection of biotinylated dextran amine in the n uclear target (the interstitial cell groups, icg) of the X zone of the rat cerebellum, retrogradely labelled Purkinje cells (PCs) were found within a longitudinal strip of cortex, 250 mu m in width, 1000 mu m l ateral to midline. This labelling delineates two compartments in the X zone, one rostral through lobules II-VI, and one caudal through lobul es VIII-X. The whole rostrocaudal extent of the icg appears to be the target of PCs from both compartments without any apparent topographica l organization.