ABSTRACT
We are concerned with the period in vertebrate ontogenesis when the nerve cell layer of the eye, the retina, develops output cells, ganglion cells. Each of these puts out an axon which grows over the surface of the retina and through the optic stalk into the optic pathway to the brain, where it establishes connexions, synapses, with cells of the developing nervous system. In lower vertebrates, such as frog, toad or fish, which are the animals that have been most studied, the main central target structure is the optic tectum. The initial connexions made by the optic nerve fibres are, in some cases, quite haphazard. After some time, however, a final configuration is reached in which there is an ordered map of retina onto tectum. Such maps are called retinotopic. The problem that has been studied in this field for several decades is: how do the fibres manage to find their proper termination area? A large number of experiments has been performed to gather constraints for possible theories. Many of these are reviewed in [1], [2].
