Lecture 10 (DONE)

Question 1

What are the two types of colors and when would you see them?

Answer 1

1. Spectral (390nm to 750nm) when viewing a rainbow
2. Broadband (multiple wavelengths) typically see all the time.

Question 2

Explain why a blue shirt looks blue (I am not using red on purpose).

Answer 2

When white light from the sun hits a blue shirt some of the wavelengths get absorbed and some get reflected. The wavelengths that get reflected the most are blue and some green, the wavelengths
that get absorbed the most are red and some yellow.

Question 3

How does adaptation of S, M, cones cause a white stimulus to be perceived as red?

Answer 3

Adaptation dampens the S & M cones’ ability to respond to the white stimulus, since their response is much less but the L cone response is still high. The response profile is the same as a red stimulus,
so the white stimulus is perceived as red.

Question 4

Explain what a metamer is.

Answer 4

A metamer are two physically different stimuli that yield the same response profile of the 3 cones / same percept. We perceive them as identical.

Question 5

How are metamers and color blindness related?

Answer 5

People who are color blind experience more metameric matches since the response profiles of the cones are the same. For example, without long wavelength cones a bright red shirt and a dark green shirt both activate M cones the same and without the L cones these are perceived as the same color.

Question 6

Damage to this area of the brain will cause what disorder and describe perceptual qualia of the disorder?

Answer 6

Achromatopsia and the world will be perceived in black and white.

Question 7

If I show a cat a bar moving downward and its neurons respond only to that downward motion what kind of neuron is this? Where is the neuron located?

Answer 7

A direction tuned neuron for downward directions located in area MT

Question 8

Step into the shoes of a philosopher staring at a waterfall but then looking to see the foliage surrounding it seemingly moving upward. Explain why this motion aftereffect happens.

Answer 8

The waterfall is adapting your neurons tuned to down, so when you look to the foliage the small spontaneous response in your up tuned neurons causes it to be perceived as moving upward.

Question 9

What is the reflectance profile?

Answer 9

A graph that shows the pigment of any given object.

Question 10

What does it mean for light to be absorb?

Answer 10

Pigment, anything that absorbs light

Question 11

What happens when light goes through the photo-pigment segment of cones and rods?

Answer 11

It absorbs the light and turns it into an electrical signal which travels through the eye and to the brain.

Question 12

What happens when colors are absorbed and not reflected?

Answer 12

It gets held by the pigment and turned into heat. (BLACK SHIRT IN SUNLIGHT)

Question 13

Why is the sky blue?

Answer 13

Blue light is emitted from the sun and gets scattered when it hits the atmosphere.

Question 14

Why is it forbidden to say the cone types are red, green, and blue? (as opposed to L,M,S)?

Answer 14

Because the peak of the L cone sensitivity is not red and we don’t call them red cones.

Question 15

What is perceived color determined by?

Answer 15

Response profile

Question 16

What does it mean for people to be colorblind?

Answer 16

It means people who are colorblind lack one cone type (usually M or L), and they have trouble discriminating between (some) colors.

Since you’re lacking either L or M cone, the same response is going to match another color’s response profile. (Since you’re lacking that one cone). So that’s why colorblind people have a hard time determining the difference between red and green.

Question 17

What area of the brain is responsible for color vision?

Answer 17

V4

Question 18

What area of the brain is responsible for motion?

Answer 18

Area MT: ability to see translational motion (one direction at a time)

Question 19

What is direction tuning curve?

Answer 19

when you isolate a neuron in MT and you record it; it’s very selective for direction of motion. That neuron has AP if you show it a stimulus of going upwards, it reacts. But when going downwards, it goes silent. If you go off a little bit from up, it may go respond lower.

Question 20

What happens when you damage MT?

Answer 20

Motion blindess- choppy movement like seeing it in a strobe light.

Question 21

What is the response profile for a static stimulus?

Answer 21

up detectors = down detects
(even when there’s no activity, there’s a resting action potential level. So activity is not = 0, because there is spontaneous activity).

Question 22

What is the response profile for an up stimulus?

Answer 22

The upward neuron detector would be activated a lot more than the downward detector. The downward detector would actually be inhibited, b/c the cells are so selective the downward detector would be silent.

Question 23

What happens if we selectively adapt your down detectors and then you look at something static?

Answer 23

After tiring your downward detectors, your upward detector would have a higher response than the downward detector. Which is interpreted as something is moving up.