THE PONTOCEREBELLAR PROJECTION - LONGITUDINAL ZONAL DISTRIBUTION OF FIBERS FROM DISCRETE REGIONS OF THE PONTINE NUCLEI TO VERMAL AND PARAFLOCCULAR CORTICES IN THE RAT

A longitudinal parasagittal organization (alternating labeled and unla beled stripes) of messy fiber terminals in the paraflocculus and in th e vermal lobule VII of the cerebellum was found after small injections (less than 50 nl) of wheat germ agglutinin-horseradish peroxidase (WG A-HRP) into discrete regions of the basilar pontine nuclei (BPN) of ra ts. Up to three stripes were found within the paraflocculus of both si des, following injections (of about 500 mu m in diameter) in either th e medial or lateral region of the caudal half of the BPN. Up to five s tripes were found in the vermal lobule VII after similar size injectio ns into the rostro-ventral region of the BPN. These results emphasize the possibility that the parasagittal zonal arrangement could be a com mon pattern of organization shared by climbing and messy fiber afferen ts.