Aberrant retinotectal pathways induced by larval unilateral optic nerve section in Xenopus.

Following unilateral optic nerve section in Xenopus tadpoles and toadlets, the reformation of visual pathways and retinotectal projections was analyzed using [3H]proline autoradiography. Bilateral retinotectal projections were found in 61% of the animals operated on between stages 42 and 58. In these animals, the projections were established through multiple aberrant pathways which included the oculomotor nerve, the trigeminal nerve and the posterior commissure. In contrast, in animals with optic nerve section at stage 62 or after metamorphosis, the regenerated optic fibres arrived at the contralateral and ipsilateral tecta through normal visual pathways.