Ch. 10.5 Color Vision Depends on Special Channels from the Retinal Cones through Cortical Area V4 Flashcards
What is hue?
A dimension of light perception, varying around the color circle through blue, green, yellow, orange, and red.
Why do hues appear different?
- different wavelengths
- intensity of illumination
- surrounding field
- prior exposure to a different stimulus.
What is the trichromatic hypothesis?
There are three different types of cones, each excited by a different region of the spectrum and each having a separate pathway to the brain. (Hermann von Helmholtz 1852)
1. red-sensitive receptors
2. blue-sensitive receptors
3. green-sensitive receptors
This would function like labeled lines.
This is no longer considered correct but the measurements of photopigments in cones stem from this.
What is the opponent-process hypothesis?
The idea that color vision depends on systems that produce opposite responses to light of different wavelengths. (Ewald Hering)
This no longer is considered correct.
Are human visual receptors sensitive to only a narrow part of the visible spectrum?
No, in fact, two of the three retinal cone pigments show some response to light of almost any wavelength.
The pigments have different peaks of sensitivity (short-wavelength, medium wavelength and long wavelength).
Under ordinary conditions, an object of almost any color stimulates at least ____ kinds of cones?
2 (this ensures high visual acuity and good perception of form)
Cones are not color detectors so their names are taken from their peak areas of wavelength sensitivity. What are they?
short-wavelength (S)
medium wavelength (M)
long wavelength (L)
Do color blind people seen no color?
No. A better term would be color deficient
What is spectrally opponent cell
A visual receptor cell that has opposite firing responses to different regions of the spectrum.
