ABSTRACT
An important mechanism for enhancing contrast in the retina is lateral inhibition brought about by horizontal cells. Lateral inhibition can be seen in the receptive fields (RFs) of both bipolar and ganglion cells. Horizontal cells are extensively interconnected via gap junctions forming a network which spans an area of retina termed the S space. The S space horizontal cells provide the signal for surround inhibition and it is thought that this signal is a measure of the mean luminance over quite a wide area of retina. Ganglion cells are the output cells of the retina. Their axons become myelinated at the optic disc and form the optic nerve. Ganglion cells are the only retinal cells capable of firing action potentials. Amacrine cells have no axons but their extensive neurites share properties of both axons and dendrites.