The corticopontine projection in the cat. I. The projection from the proreate gyrus

Following large and small lesions (in many cases bilateral) of the proreate gyrus in adult cats the ensuing degeneration in the pontine nuclei was studied with the silver impregnation methods of Nauta and of Fink and Heimer. Lesions were produced by transdural thermocoagulation The main results are as follows: All parts of the proreate gyrus on the convexity of the hemisphere emit fibers to the pontine nuclei. The projection from the dorsal part is somewhat less intense than that from the ventral part. The density of projection from the proreate gyrus is far less than from the anterior sigmoid gyrus (motor cortex). The proreate gyrus projects upon two longitudinal columns in the ipsilateral pontine gray. One column is located medially, the other laterally. The exact localization of these columns has been compared with the localization of the columns projected upon by the anterior sigmoid gyrus. No clear difference has been found. No topical localization could be demonstrated within the pontine projection from the proreate gyrus, which in this respect differs from the projection from the anterior sigmoid gyrus (motor cortex), which projects somatotopically upon both columns. Possible relations between the proreate gyrus and the cerebellum are discussed.