Many cat retinal ganglion cells (types X, Y, and W) have inputs from three separate cone systems. Those with peak sensitivities at 450 and 555 nanometers have been previously shown. A λmax cone with a peak sensitivity of 500 nanometers can be differentiated from other cones by spectral sensitivity andfrom rods by receptive field differences, functioning above rod saturation levels, and by cone-rod breaks in the dark-adaptation curves. The similarity of the three-cone cat retina to the extramacular retina of the rhesus monkey suggests that the cat may have photopic trichromatic vision.
