Design of a trichromatic cone array.
Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative.
Garrigan
Patrick
P
Department of Psychology, Saint Joseph's University, Philadelphia, Pennsylvania, USA. patrick.garrigan@sju.edu
Ratliff
Charles P
CP
Klein
Jennifer M
JM
Sterling
Peter
P
Brainard
David H
DH
Balasubramanian
Vijay
V
D000465:Algorithms; D019295:Computational Biology / Q000379:methods*; D016208:Databases, Factual; D006801:Humans; D008027:Light; D008954:Models, Biological; D010781:Photography; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*