Project 15

Neurotrauma:The influence of training on axon pathfinding during optic nerve regeneration.

In fish and amphibia, optic nerve regeneration is successful. Retinal ganglion cell axons regenerate to the main visual centre, the optic tectum, within one month and reform a topographic map; as a result, useful vision is restored. By contrast, in birds and mammals, optic nerve regeneration is abortive with little if any spontaneous regeneration beyond the lesion site. In a reptile, the ornate dragon lizard Ctenophorus ornatus, axons regenerate spontaneously to the optic tectum but fail to restore topography and animals remain blind via the experimental eye. We have recently shown that, after optic nerve lesion, visual training on a specific task restores topography within the tectum in the long term as assessed electrophysiologically and anatomically. Pilot anatomical data in long term animals suggest that axons are disordered in the visual pathway en route to the tectum in untrained animals but ordered in trained ones. The implications are that either training influences retinal ganglion cell axon pathfinding as they grow to the tectum or that training results in the removal of inappropriately located axons. The project will examine axon order in the visual pathway of animals at different times after optic nerve crush using confocal microscopy to distinguish between the two possibilities.

Publications

 Beazley L.D., Rodger, J., Chen P., R.V. Stirling, A.L. Taylor, Tee, L.B.G. and Dunlop, S.A. 2003. Training on a visual task improves the outcome of optic nerve regeneration. J. Neurotrauma, 20:1263-1270.