Vision: Life on the dark side

Abstract

Mice detect decreases in illumination in dim light near the visual threshold with OFF retinal ganglion cells.

Figure 1.. Processing of rod signals in the mammalian retina for dim light near the visual threshold.

Many rods synapse onto each rod bipolar cell (RBC). The RBCs then make excitatory glutamatergic synapses onto AII amacrine cells, which convey the rod signals to ON and OFF cone bipolar cells (CBCs) in the following way. The AII amacrines make gap junctions onto ON CBCs, which in turn excite ON ganglion cells (ON GCs). The AII amacrines also make glycinergic inhibitory synapses onto OFF CBCs, which convey the OFF signal to OFF GCs. AII amacrines also make direct inhibitory synapses onto the processes and somata of OFF GCs. AII, AII amacrine cell; C, cone photoreceptor; GCL, ganglion-cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; OFF CBC, off (hyperpolarizing) cone bipolar cell; OFF GC, OFF ganglion cell; ON CBC, on (depolarizing) cone bipolar cell; ON GC, ON ganglion cell; ONL, outer nuclear layer containing inner segments of rods and cones; OPL, outer plexiform layer; OS, outer segments of rods and cones; R, rod photoreceptor; RBC, rod bipolar cell. (Figure by Margery J. Fain.)