COGS 101A Lecture Notes - Lecture 10: Illusory Motion, Receptive Field, Akinetopsia
● Opponent Processes
○ “Psychological primaries” are red, green, yellow, and blue
○ Opposites
■ Can’t imagine mixing red and green because they’re opposite
○ All colors on the color circle can be represented by the proportion of two of these
four colors
○ Opponent process theory
■ Physiological responses generated by blue v. yellow, red v. green, black
v. white
■ Respond with excitatory response to on range of or wavelengths, and an
inhibitory response to another range
○ LGN
■ Parvocellular layer has evidence of opponent process theory
○ Color after image
○ Adaptation
■ Exact mechanisms are debated
■ Main idea
● Neurons will start to fatigue after responding to preferred stimulus
for a while
● Neurons are inhibited will rebound after inhibition
○ STare at red, so those responsive neurons are tired, so
opposite response cell has spontaneous recovery from
being inhibited, you see green
● Reconciling 2 theories
○ Trichromacy = what happens in cones
■ Cones of opposites talk to a bipolar cell which gives you opposites
■ Example B+Y- means you have the blue cell activated
○ Opponent process = happens later on in the visual system
● Color constancy
○ We see the same color despite changes in the composition of the wavelengths of
light that is striking that object
■ Exp. mondrian
■ Exp. picture has a filter over it but we can still perceive a strawberry as
red (even if no pixel is red)
○ Reflectant
■ The surface that the light reflects off
○ Illuminant
■ The light that hits a surface
○ Retinex theory
■ Retina + cortex, there’s more to color vision going on than what happens
in the retina
○ Discounting
■ Taking out color difference; your brain knows it’s just a reflection
Document Summary
Psychological primaries are red, green, yellow, and blue. Can"t imagine mixing red and green because they"re opposite. All colors on the color circle can be represented by the proportion of two of these four colors. Physiological responses generated by blue v. yellow, red v. green, black: white. Respond with excitatory response to on range of or wavelengths, and an inhibitory response to another range. Parvocellular layer has evidence of opponent process theory. Neurons will start to fatigue after responding to preferred stimulus for a while. Neurons are inhibited will rebound after inhibition. Stare at red, so those responsive neurons are tired, so opposite response cell has spontaneous recovery from being inhibited, you see green. Cones of opposites talk to a bipolar cell which gives you opposites. Example b+y- means you have the blue cell activated. Opponent process = happens later on in the visual system.
