The pontine projection onto longitudinal zones of the paramedian lobule in the cat.

The distribution of labeled cells in the pontine nuclei was studied following microinjections of horseradish peroxidase into three longitudinal zones in the paramedian lobule in the cat. Labeled cells were only found when the staining of the cerebellar cortex included the granular layer. The labeled cells were present contralateral to the injection site in the cases with the smallest injections, in the others there was a bilateral distribution with a contralateral preponderance. The labeled cells lie concentrated in three groups medially, ventrally, and laterally to the peduncle. No indication of a different projection from these three groups to the three longitudinal paramedian zones was found, although in the same material a zonal projection exists for the climbing fibers from various parts of the inferior olive to the same cerebellar lobule (Brodal and Walberg, 1977).