The Neural Control of Vision
C. The Retina

Even though there is only a single layer of photoreceptors in the retina, interconnections give rise to overlapping receptive fields among the more than 10 different classes of retinal ganglion cell types as shown in Figure 7, four of which are shown explicitly. There are more than 3 times as many cone bipolar cells in the retina as there are cone photoreceptors.