Retina Structure and Color Vision

Study Notes

Rods are most abundant in the periphery of the retina and respond to faint light.
Cones are most abundant in and near the fovea and are more useful in bright light.
Cones are essential for color vision and provide about 90% of the brain's input.
The fovea is the central part of the retina with densely packed cones.
The periphery of the retina has a higher proportion of rods.
Convergence of Input: In the periphery, multiple rods converge onto a single ganglion cell, while in the fovea, a single cone typically connects to a single ganglion cell. This difference explains the greater sensitivity of peripheral vision to dim light and the superior detail vision of foveal vision.

Visible light is a portion of the electromagnetic spectrum perceived by humans.
The wavelength of light determines the color we perceive.
Humans can perceive wavelengths between 400 and 700 nanometers (nm).
Color Vision Theories:*
Trichromatic Theory: Three types of cones – S-cones, M-cones, and L-cones - each sensitive to short, medium, and long wavelengths respectively. The ratio of activity across these cones determines the perceived color.
Opponent-Process Theory: We perceive color in terms of paired opposites, like red vs. green, yellow vs. blue, and white vs. black. This theory explains negative afterimages.
Retinex theory: The cortex compares information from different parts of the retina to determine brightness and color. This theory explains some color illusions.