Unscrambling Color Vision

摘要

Color vision begins when light is absorbed by one of three different visual pigments, located in cone photoreceptor cells of the retinas of humans and some species of monkey. The pigments absorb light at short, middle, or long wavelengths, and the cone photo-receptors containing them are commonly termed blue, green, or red cones. For transmission to the brain, the outputs of the three types of cones are almost immediately re-combined to yield signals distributed along two chromatic axes, one describing a range of wavelengths from green to red and the other a range of wavelengths from blue to yellow (yellow is defined as a mixture of green and red). These retinal computations are embodied in the responses of the retinal ganglion cells, neurons with axons that form the optic nerve. A ganglion cell might be excited by stimulation of the red cones and inhibited by stimulation of the green. Such a cell tells the brain how far along the red-green axis the stimulus fell, with high firing rates representing a stimulus containing a lot of red light and low representing a stimulus containing a lot of green light.