Chapter 5.3 Flashcards
Color Blindness
inability to perceive color differences, lack cone pigment due to bad X gene
(sex linked=effects mostly men as they have XY)
Dichromatic
use/have two cones
Trichromatic
use/have three cones
Monochromatic
some people lack two types of cones (very rare)
-or achromatopsia
Protanopia (dichromatic)
red/green deficit or color blindness, can’t tell difference between green and
red, 1% of male population, .02% of female population, no L pigment, sex-linked
Deuteranopia (dichromatic)
similar effects as protanope, red/green deficit or color blindness, 1%
men, .01% women, no M pigment (but extra L pigments to make up for lack of M)
Tritanopia (dichromatic)
: blue/yellow deficit or color blindness, very rare not on X chromosome (not
sexlinked), chromosome 7 gene mutation, no S pigment
There are no glasses that “cure” dichromacy
most people who are colorblind
are not fully colorblind so these glasses can help brighten duller colors but these
glasses don’t help people see colors they don’t have the cones to perceive
Why are protanopia and deuteranopia so similar in spectral sensitivities?
Tremendous overlap of M and L cones compared to S cones, M and L relatively closer in
wavelength perception and sensitivity
Monochromats
: 1 in 30,000, only 1 cone type (S cones), “blue cone monochromacy,” virtually
no real color perception
Rod Monochromat
Most monochromats have no cones at all, most common form of
monochromacy
Animal Color Vision
● Some birds have 4 cones
● Zebra finch are tetrachromats: 4 cones, 1 cone just for Ultra-violet spectrum, all cones
sensitive and can perceive UV
● Dogs and cats dichromats: have rods in their fovea= less clear and bright vision
compared to us, see duller versions of colors
● Mantis Shrimp has 12 cones!
Visual Processing in the Cortex
Feature detectors
● Neurons beyond retina respond to specific feature
○ V1 (striate cortex) and V2: shape, angle, spatial frequency
