Cone-shaped retinal cells {cone, cell} have daylight-vision photoreceptors and detect color and visual details.
types
Humans have three cone types. Cone maximum wavelength sensitivities are at indigo 437 nm {short-wavelength cone}, green 534 nm {middle-wavelength cone}, and yellow-green 564 nm {long-wavelength cone}. Shrimp can have eleven cone types.
evolution
Long-wavelength cones evolved first, then short-wavelength cones, and then middle-wavelength cones. Long-wavelength and short-wavelength cones differentiated 30,000,000 years ago. Three cone types and trichromatic vision began in Old World monkeys.
fovea
Fovea has patches of only medium-wavelength or only long-wavelength cones. To improve acuity, fovea has few short-wavelength cones, because different colors focus at different distances. Fovea center has no short-wavelength cones [Curcio et al., 1991] [Roorda and Williams, 1999] [Williams et al., 1981] [Williams et al., 1991].
number
There are five million cones, mostly in fovea. Short-wavelength cones are mostly outside fovea.
size
Cones are smaller than rods.
pigment
Cone light-absorbing pigment is iodopsin. Rods have rhodopsin.
frequency
When rods saturate, cones have approximately same sensitivity to blue and red.
Just above cone threshold {mesopic vision, cone}, rods are more sensitive to short wavelengths, so blue colors are brighter but colorless. Retinal receptors do not detect pure or unmixed colors. Red light does not optimally excite one cone type but makes maximum excitation ratio between two cone types. Blue light excites short-wavelength cones and does not excite other cone types. Green light excites all cone types.
output
Cones send to one ON-center and one OFF-center midget ganglion cell.
Consciousness>Consciousness>Sense>Vision>Anatomy>Cells>Retina>Receptors>Cones
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Date Modified: 2022.0224