A spatial analysis of on- and off-ganglion cells in the cat retina

Using reduced silver staining methods it was possible to stain all alpha-ganglion cells of the cat retina. The dendritic trees of alpha-cells are unistratified in either of two laminae within the inner plexiform layer. This stratification difference was shown physiologically to correspond to the on-off dichotomy. For all alpha-cells recorded, the dendritic field was covered by the corresponding receptive field centre. In addition the general shape of the receptive field centre corresponded to the shape of the dendritic field. The size of the dendritic tree was always smaller than the receptive field centre. The topographical distribution of on- and off-alpha cells could be studied. They were found to occur in about equal numbers. Both on- and off-alpha-cell perikarya form a regular lattice and both lattices are superimposed independently. The dendritic branches of neighbouring alpha-cells overlap and each retinal point is covered by the dendritic field of at least one on- and one off-alpha-cell. After horseradish peroxidase (HRP) injection into the lateral geniculate nucleus all beta-cells were labelled. In this way it is shown that about 55% of all ganglion cells are beta-cells. The mosaic of on- and off-beta-cells was studied from the HRP-labelled material. It is commonly assumed that beta-cells are associated with the resolution of fine detail in the cat visual system. The mosaic of beta-cells imposes some constraints and permits some predictions to be made with respect to the cat's visual discrimination.