Telencephalic efferents in channel catfish, Ictalurus punctatus: projections to the olfactory bulb and optic tectum.

Telencephalic projections to the olfactory bulb and optic tectum were examined with horseradish peroxidase (HRP) methods in catfish. Olfactory bulb afferents arise from the mitral cell layer of the contralateral olfactory bulb and the ipsilateral telencephalon. The majority of labelled cells appear within the ventral and dorsal nuclei of area ventralis telencephali and two divisions of the central zone of area dorsalis telencephali. Excepting one division of the dorsal central zone, all afferent sources are secondary olfactory targets. Tectal HRP injections reveal labelled cells in a third division of the dorsal central zone.