Projection of Color Coding Retinal Neurons in Urodele Amphibians

Optic fiber projection in the brain of Salamandra salamandra was investigated by degeneration techniques. Terminal fields are described in the thalamus and in the optic tectum. Microelectrode recordings were performed from ganglion cells in the retina and from their terminals in the thalamus and tectum in Salamandra and Triturus alpestris. 'On' cells showed maximal sensitivity either in the blue or in the yellow spectral region; they project to the thalamus. Color coding 'on-off' cells project to the tectum opticum. In Triturus a seasonal change in these neurons occurs. Probably due to transition of vitamin A2 into vitamin A1 the spectral sensitivity is different. In springtime blue-red opponent-color neurons were recorded, in fall however, blue-yellow neurons were found.