Topography of retinodiencephalic projections in adult channel catfish

In order to determine the topography of retinal axons in diencephalic nuclei of Ictalurus punctatus, horseradish peroxidase was applied to the optic papillae. The topography was found to be similar in all nuclei in that the terminal endings of ventral retinal axons innervated rostrodorsally whereas dorsal retinal axons innervated caudoventrally. In general, the retinal topography in the diencephalon corresponded with the topography of retinal axons in the optic tracts. These data suggest a relation between retinal axon ordering within a target and the pathway by which axons enter the target.