A non-canonical pathway for mammalian blue-green color vision

The dynamic range of visual coding is extended by having separate ganglion cell types that respond to light increments and decrements. Although the primordial color vision system in mammals contains a well-characterized ganglion cell that responds to blue light increments (a blue On center cell), less is known about ganglion cells that respond to blue light decrements (blue Off center cells). We identified a regular mosaic of blue Off center ganglion cells in the ground squirrel. Contrary to the standard scheme, blue Off responses came from a blue On bipolar and inverting amacrine cell.