Figure 1: Functional circuitry of the retina.

a | Organization of retinal circuits. Rod (R) and cone (C) photoreceptors have cell bodies (CBs) in the outer nuclear layer and extend inner segments (IS), which contain metabolic machinery, and outer segments (OS), which associate with retinal pigment epithelial (RPE) cells. Photoreceptor axons terminate in the outer plexiform layer and synapse with horizontal (H) and bipolar (B) cells in the inner nuclear layer, which also contains Müller glial (M) and amacrine (A) cells. Bipolar cells relay signals to amacrine and ganglion (G) cells through synapses in the inner plexiform layer. Ganglion cell axons project towards the optic nerve head and carry signals to the brain. End-feet of Müller glia form the outer and inner limiting membranes. A representative cone pathway is shown in blue and a representative rod pathway is shown in orange. b | Illustrations of rod and cone morphologies that include subcellular locations of functions. c | A surface-view representation of cone distribution across the mammalian retina. In humans, cones express S opsins (peak sensitivity to blue light), L opsins (peak sensitivity to red light) or M opsins (peak sensitivity to green light) in a mosaic-like pattern. In mice, cones express S opsins and M opsins in opposing distribution gradients along the superior (M opsin-high) to inferior (S opsin-high) axis. Syn, synaptic terminus.