Bipolar cells use kainate and AMPA receptors to filter visual information into separate channels

Unlike cone photoreceptors, whose light responses have a uniform time cours e, retinal ganglion cells are tuned to respond to different temporal compon ents in a changing visual scene. The signals in a mammalian cone flow to th ree to five morphologically distinct "OFF" bipolar cells at a sign-conservi ng, glutamatergic synapse. By recording simultaneously from pairs of synapt ically connected cones and OFF bipolar cells, I now show that each morpholo gical type of OFF bipolar cell receives its signal through a different AMPA or kainate receptor. The characteristic rate at which each receptor recove rs from desensitization divides the cone signal into temporal components. T emporal processing begins at the first synapse in the visual system.