Lecture 3 (pres 2 starting slide 105, thru pres 3)

Question 1

what is the order of variability in unique hues from LEAST to MOST variability? Give answer in terms of 4 colors

Answer 1

LEAST variability: yellow–>blue–>red–>green: MOST variability

Question 2

you’re awesome.

Answer 2

thank you.

Question 3

T/F: the axes of the unique hues fall on the cardinal axes after the LGN

Answer 3

FALSE. Cardinal axis is where you have the MAX activation of the cone-opponent cells, unique hues are NOT on those lines after the LGN (they ARE before)

Question 4

Which of the four unique colors is NOT a spectral color (i.e., does NOT fall on the perimeter of the color space?)

Answer 4

unique RED - it’s not monochromatic. Why? Because it falls on the line of PURPLES

Question 5

What technique was used to derive unique hues? By doing what?

Answer 5

hue CANCELLATION - rotation of the cardinal axes to match the axes of the unique hues.

-Note: will NOT get unique red by doing this - it’s NOT monochromatic!!

Question 6

Are the cardinal axes different between humans? What about the unique hues?

Answer 6

cardinal axes - same

unique hues - DIFFERENT b/w humans - shows variability - recall: GREEN is most variable

Question 7

When they reach the cortex, the parvo/magno/konio pathways all project to what area/layer?

Where, specifically, do the PARVO cells project? How about the MAGNO cells? (what layer)?

Answer 7

4C layer of V1

parvo: 4Cb
magno: 4Ca

Question 8

Within ocular dominance columns, SIMPLE cells respond to…

COMPLEX cells respond to…
BLOBS respond to…

Answer 8

simple: C/S config for bar of light AT UNIQUE ORIENTATION
complex: correct orientation that is MOVING
blobs: process color, not unique hues. Send their info to V2 before sending to V4 (color part of cortex)

Question 9

A color will have maximum contrast when it is surrounded by….

-why does this happen?

Answer 9

its OPPOSING color

• if surround is green, it induces RED in the center. If red is already there, it’s even more pronounced
• Take-Home: the surround INDUCES THE OPPOSITE COLOR

Question 10

which property of color is influenced by ADJACENT color squares?

Answer 10

color ASSIMILATION (like color SPREADING)

• i.e. reds surrounded by yellow make line seem orange.
• red surrounded by blue make line seem violet

Question 11

Color is a property of the ______, making what color property difficult to understand?

Answer 11

MATERIAL - therefore, it’s the same regardless of the lighting…but the lighting varies, changing the constant color’s appearance.

Property: color CONSTANCY (the dress)

Question 12

Topic: color constancy

• OUTSIDE light tends to be (shorter/longer) wavelength.
• How about INSIDE light?

-Our visual system tries to discount WHAT in order to perceive colors as they really are?

Answer 12

outside: LONGER wavelength
inside: SHORTER wavelength

LUMINANCE is discounted. (Different illumination-same as luminance-triggers different cone responses, but somehow the visual system ignores the varying cone responses to keep the color the same)

Question 13

What word defines when our visual system normalizes the cone responses every time there is a change in illumination?

Hint: this is also the MOST IMPORTANT reason why color constancy exists

Answer 13

chromatic adaptation.

-so long as observer and the object are under the SAME illumination, the object’s color stays the same (b/c the visual system normalizes)

Question 14

When does color constancy FAIL? Seen in what effect?

Answer 14

fail: when we see objects WITHOUT SURROUND

- the KEYHOLE effect

Question 15

Three variables of color constancy?

Answer 15

1) chromatic adaptation
2) effect of surroundings (keyhole effect)
3) memory (i.e. remembering red is on top @ traffic light)

Question 16

OLD world monkeys: location? Tails/no tails? Ground/trees? Type of color vision?

Answer 16

africa/asia. NO tails - ground. TRICHROMATIC CV - MALES AND FEMALES

Question 17

NEW world monkeys: location? Tails/no tails? Ground/trees? Type of color vision?

Answer 17

central/south america. HAVE tails - trees. CV: mixture b/w TRI and DIchromatic

• all new-world MALES are dichromatic (2 cones, 1 rod)
• 1/3 new-world FEMALES are DIchrom. (homozygous), 2/3 are TRIchrom (heterozygous)

Question 18

What’s the difference in the X chromosome that causes NEW world monkeys to not always be trichromatic? HINT: recall that new males can NEVER be trichomats, only DIchromats

-BTW, where is the blue opsin as far as genetics is concerned?

Answer 18

X chromosome used to (old world) carry both R and G opsins on the same X chromo. NEW X chromos only carry ONE OPSIN

-blue is on chromosome 7 - the color chromosome…it gets combined w/ the Xs and Ys

Question 19

New world MALES (all DIchromats) all have which three components for color vision?

Answer 19

1) chromosome 7
2) S-CONE opsin
3) random G/R/mixture of 2nd opsin

..so - two cones, one rod. DIchromat.

Question 20

What unique feature of new world FEMALES allows 2/3 of them to have trichromacy?

Answer 20

their unique RETINA allows for it.

Question 21

One theory (the unlikely one) says that a random ___ in the X chromo occurred in old world monkeys and not new ones

Second theory (likely) stated what?

Answer 21

duplication (in only the old world monkeys)

Second theory: exchanging of X-chromo genetic material happens via CROSSOVER - Caused old world monkeys to end up w/ two X-chromos that had two opsins