Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris.

The development of the retinofugal projection areas of the brain has been studied in larvae of Triturus alpestris by means of anterograde transported horseradish peroxidase. The optic tract establishes contacts with the optic tectum prior to the onset of robust terminal formation in the diencephalon. The tectum becomes covered by the retinofugal projection in a rostro-caudal direction. The basal optic neuropil develops synchronously with the oculomotor neurons. Their dendrites extend into this neuropil area. A small amount of uncrossed label occurs long before metamorphosis. Around metamorphotic climax this ipsilateral label increases but does not attain the adult pattern even three monts postmetamorphosis. The data are compared with the onset of visual induced behaviour.