Ascending afferents to the telencephalon of ranid frogs: an anterograde degeneration study.

Sources of telencephalic afferents were examined in two species of frogs, Rana catesbeiana and Rana pipiens, by study of anterograde degeneration resulting from hemisection of the brain at the isthmus or at the caudal border of the thalamus and from electrolytic lesions in various portions of the diencephalon. The results indicate that some telencephalic afferents arise from levels caudal to the isthmus, that some striatal afferents arise from a level between the isthmus and the caudal border of the thalamus, and that a projection to the ipsilateral striatum arises from the anterior and/or middle portions of the dorsal thalamus. Diencephalic projections to pallial portions of the hemisphere were also observed. These results demonstrate substantial non-olfactory afferent projections to the telencephalon in ranid frogs.