RGB color model spaces for more details. The choice of primary colors is related to the physiology of the human eye; good primaries are stimuli that maximize the difference between the responses of the cone cells of the human retina to light of different wavelengths, and that thereby make a large color triangle. The normal three kinds of light-sensitive photoreceptor cells in the human eye (cone cells) respond most to yellow (long wavelength or L), green (medium or M), and violet (short or S) light (peak wavelengths near 570 nm, 540 nm and 440 nm, respectively). The difference in the signals received from
Intrinsically photosensitive retinal ganglion cells these cells may receive excitatory and inhibitory influences from rods and cones by way of synaptic connections in the retina. The axons from these ganglia innervate regions of the brain related to object recognition, including the superior colliculus and dorsal lateral geniculate nucleus. These photoreceptor cells project both throughout the retina and into the brain. They contain the photopigment melanopsin in varying quantities along the cell membrane, including on the axons up to the optic disc, the soma, and dendrites of the cell. ipRGCs contain membrane receptors for the neurotransmitters glutamate, glycine, and GABA. Photosensitive ganglion cells respond to light