The basilar pontine gray of the opossum (Didelphis virginiana). II. Experimental determination of neocortical input

The pattern of neocortical input into the basilar pons of the opossum was determined by employing the Nauta‐Gygax technique ('54) on the brains of animals previously subjected to neocortical lesions. The results indicate that every neocortical area projects to some portion of the basilar pons in this form. Degenerating fibers resulting from more rostral cortical lesions (frontal and preorbital areas) terminated profusely within the medial and ventral nuclei and, to a lesser extent, in the smaller dorsal nucleus. Fascicles from more caudal areas (striate and peristriate cortices) ended abundantly in the lateral nuclear group, and in the lateral part of the ventral nucleus. Every neocortical region studied projected to some portion of the ventral pontine nucleus. Degenerating fibers terminated to some extent within each nucleus of the basilar pons as a result of lesions in midcortical regions (paramarginal, postorbital and parietal cortices). A few fibers of frontal, orbital and parietal origin terminated in the contralateral basilar pontine gray.