Patterns of organization of comments on the corticopontine projection in the cat with the pontocerebellar projection.

Following lesions of various parts of the cat cerebral cortex, the distribution of degenerating fibers in the pontine nuclei was mapped in drawings of serial transverse and horizontal sections of Fink and Heimer. All parts of the cerebrum give rise to the corticopontine fibers and each functionally uniform area has its particular projection zones in the pons. Thus, it has been shown that the pontine projection zones from the sensorimotor, auditory, orbital, cingulate and "association" cortices are arranged in longitudinal columns throughout the pons, mostly in well delimited columns, while those from the visual cortex reveal columns oriented transversely in the rostral part of the pons. When the distribution of the pontine afferents from various parts of the cortex are compared in detail, it is evident that there are differences in locations of the columns, clustered in continuous zones of terminations, among different pontine projections, although there are partial overlaps among these projection zones. The present as well as the previous findings of the corticopontine projection are correlated with observations of the pontocerebellar projection obtained by other investigators with the horseradish peroxidase and the autoradiographic methods, and a possible propagation of different modalities of sensations from the cerebral cortex, via the pons, to the cerebellum is discussed with reference to some physiological data. The present study largely confirms and extends the previous data of the corticopontine projection and reveals that the cortico-ponto-cerebellar pathways are more cmplexly organized than was previously assumed.