Topographical origin and ganglion cell type of the retino-pulvinar projection in the cat.

In order to examine the pattern of the retino-pulvinar projection in the cat, the existence of which has been recently demonstrated using autoradiographic fiber tracing technique, a small amount of horseradish peroxidase (HRP) was injected into the lateral part of the pulvinar nucleus at various rostocaudal levels. The retrogradely labeled ganglion cells were analyzed in terms of their topographical location and cell size, as seen inretinal whole mounts. The results were compared with those obtained following injections into the lateral geniculate nucleus. Retrogradely labeled cells were found in the retina bilaterally after injections of HRP into the pulvinar nucleus. Pulvinar injections produced labeling of retinal cells in the nasal half of the retina contralaterally, and in the temporal half ipsilaterally. The labeled cells were diffusely distributed in a retinotopically organized fashion. The representation of the area centralis in the retino-pulvinar projection is displaced rostrally as compared with the retino-geniculate projection. All labeled cells after pulvinar injections were medium to small size and no large cells were encountered.