The formation of direct ipsilateral retinodiencephalic connections from compound eyes in Xenopus

Abstract

An orderly retinotopic organisation in the optic nerve projections to the contralateral visual centres of the brain (the mesencephalic optic tectum, the nucleus of Bellonci (NB), the corpus geniculaum thalamicum (LGB), the pretectal nucleus (PN) and the tegmental nucleus) has been described in the frog. It has also been demonstrated that the peripheral part of the temporal quadrant of the retina projects to the ipsilateral NB, LGB and PN. The time of the specification of the orderly retinotectal connections has been revealed in Xenopus to occur at or after stage 30, that is, before the beginning of the outgrowth of optic fibres to the developing visual centres of the brain. Because the embryonic specification of the connections from the retina to the visual centres was assessed by mapping the retinotectal connections electrophysiologically in the adult toad it has not been determined whether the retinodiencephalic connections are specified at the same time and in the same way than those of the retinotectal connections. This report, a short abstract of which has been published, deals with the development of the ipsilateral retinodiencephalic connections in a compound eye situation.