A species difference between Rana and Xenopus in the occurrence of intertectal neuronal plasticity.

In anuran amphibians, a system of neuronal connections links the two optic tecta and is involved in projections of the binocular visual field to the optic tecta. Electrophysiological studies have shown that in the frog, Xenopus laevis, the pattern of connections may be modified by procedures such as larval rotation of one eye. This modification appears to be effected by visual experience. Workers in other laboratories, however, found no evidence of such a modification in the related frog Rana pipiens. This difference in results may have been due to different rearing conditions and different recording techniques or may reflect a true species difference, in this respect, between Rana and Xenopus. In the present experiments, an attempt was made to distinguish between these possibilities by performing eye rotations in Rana and Xenopus, rearing them as identically as possible and recording from them under identical conditions. It was found that while Xenopus displayed the modification of intertectal connections, Rana did not. It is concluded that the different responses of the intertectal systems to larval eye rotation in Xenopus and Rana reflect a species difference.