colour vision

Question 1

principle of univariance

Answer 1

the absorption of light by any photoreceptors causes only one effect
no matter what the wavelength

single cone has no differentiation between wavelengths, needs multiple

Question 2

dichromats

Answer 2

individuals who can match all colours with 2 primary lights

protanopia - no L cones
deuteranopia - no M cones
tritanopia - no S cones

Question 3

anomalous trichromats

Answer 3

individuals who match all colours with 3 primary lights but in different proportions

protanomaly - L cones closer to M
deuteranomaly - M cones closer to L

Question 4

trichromacy

Answer 4

have short, medium and long wavelength sensitive cone cells

Question 5

Young-Helmholtz Theory of trichromacy

Answer 5

derived from experiments of colour matching in humans
observers asked to adjust relative amounts of mixture in several wavelengths until it matched the colour of a single wavelength in test stimulus

determined there were 3 types of cone cell
actual proof came from microspectrophotometry

Question 6

colour opponency

Answer 6

colour falls into 4 groups according to how much red, green, blue or yellow they contain

perception of colour based on 4 primary colours
processed by 2 perceptually opponent colour channels
blue-yellow and red-green

mediated by 2 perceptual channels fed by 3 types of cone cells
one channel compares signals from L with M
another compares S with L and M

Question 7

trichromacy vs opponency

Answer 7

trichromacy relies on additive mixing
opponency is subtractive colour mixing
meant they got differing results

perception of different colours made possible by neural circuits that compare the outputs of 3 different photoreceptors (cones) in 2 colour opponent channels