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PSYO2150 - Midterm #2 - Perceptual Processes > Chapter 9 - Lecture Section 9.2 > Flashcards

Chapter 9 - Lecture Section 9.2 Flashcards

1
Q

What are the two predominant theories of Colour Vision?

A

The Trichromatic Theory of Colour Vision proposed by Thomas Young (1773-1829), supported by Hermann Von Helmholtz (1821-1894) and James Clerk Maxwell (1831-1879)

The Opponent Process Theory of Colour Vision proposed by Ewald Hering (1834-1918)

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2
Q

What is another name for the Trichromatic Colour Theory?

A

It’s often called the Young-Helmholtz Trichromatic Colour Theory with Maxwell being left off, this is due to political reasons, not due to who did the most work.

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3
Q

How was the psychophysical evidence for the Trichromatic Theory of Colour Vision collected?

A

Through Colour-Matching experiments, this was mostly collected by Helmholtz and Maxwell

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4
Q

How were the Colour-Matching experiments done by Helmholtz and Maxwell performed?

A

The subject is presented with a monochromatic test-light, which means there is a test-light that is shining light that has only one wavelength, in this case, ours is a 500nm test-light.

The subject controls the intensity of 3 of the other spotlights that are all shining onto the central area, this is called the Comparison Field, and they can adjust the intensity of the 420nm light, 560nm light, and 640nm light.

By adjusting the intensity of the 3 lights and creating this additive colour mixing, the subject can match any single wavelength by combining the lights of 3 wavelengths. It doesn’t work if you only have 2 lights, you can’t match all of the single wavelength colours. And if you have more dials and more lights, it doesn’t affect anything. 3 appears to be the magic number

When the subject has twisted the dials the perfect amount, and they believe the test field is identical to the Comparison Field, this creates a Metameric Pair.

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5
Q

What are Metameric Pairs?

A

Two lights that appear identical even though they have a different wavelength composition, and are physically different.

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6
Q

How many Cones do we have?

A

We have three types of Cones, each selectively sensitive to either Short, Medium or Long Wavelengths of light.

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7
Q

How is it then that we can see millions of colours when we only have 3 Cones?

A

It is all about the relative activity of the 3 Cone populations, or the proportional activation, what proportions these different cones are being activated for a particular spot that is acting as the stimulant.

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8
Q

Metameric pairs: If S/M/L cones are activated in the same proportion, the light appears ___ regardless of the light’s physical properties

A

the same

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9
Q

Why is it that a Metameric pair of lights can appear perceptually identical to the colour of a single light, but is physically different?

A

Because it’s activating the S, M & L wavelength cones to an identical amount. There’s an identical pattern for these two types of stimuli.

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10
Q

If S, M & L wavelength cones are activated in ___ proportion, the light will appear ___ regardless of the light’s properties.

A

the same // identical

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11
Q

Blue predominantly activates ___ Wavelength cones with very little in the ___ Wavelength.

A

S // M or L

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12
Q

Green predominantly activates the ___ Wavelength cone with less for ___ Wavelength.

A

M // S & L

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13
Q

Red predominantly activates the ___ Wavelength cone with very little ___ Wavelength activation.

A

L // S

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14
Q

White is when all photoreceptor types are ___ active.

A

equally

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15
Q

Perception is not about the ___ of the stimulus, it is about the ___ that those physical attributes produce. So if the ___ is identical, the percept will be identical

A

physical characteristics // pattern of the neural activation // pattern

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16
Q

What is The Principle of Univariance?

A

The ​​Principle of Univariance discusses information channels that allow colour perception.

The Principle of Univariance states that once a photon of light is absorbed by a visual pigment molecule, the identity of the light’s wavelength is lost. This means that the receptor does not know the wavelength of the light that is absorbed, only the total amount of light it has absorbed.

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17
Q

With ONE photopigment, Wavelength and intensity are ___.

A

confounded

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18
Q

What is normal Trichromatic Vision?

A

Where we have all 3 of our Cone Photoreceptors working properly.

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19
Q

What are the 2 types of Rod Monochromats?

A

Typical and Atypical

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20
Q

What is a Rod Monochromat?

A

Monochromats are truly colour blind and see everything in shades of grey.

Rod Monochromats see everything in different intensities/shades of grey.

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21
Q

What is one cause of defects in colour vision?

A

There are several types of colour deficiency that can be produced if you are missing the gene to produce a particular type of Cone Opsin

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22
Q

What is Protanopia?

A

Protanopia occurs when a person is missing the Long-Wavelength Cone Opsin

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23
Q

How does an individual with Protanopia perceive colour?

A

The world appears as shades of Yellow and Blue

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24
Q

How are we able to figure out that people with colour deficiencies see it this way?

A

This can have to do with the genetics of these colour deficits

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25
Q

Is Protanopia sex-linked?

A

Yes, 1% of males and .02% of females

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26
Q

Why does Protanopia occur in males more than females?

A

The genes that encode this opsin are on the X chromosome, therefore, males, who only have one X chromosome are much more likely to suffer from this deficit.
Females have two X chromosomes, so their second X chromosome acts as kind of a backup copy, and so this occurs less in females than males

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27
Q

What is a Chimera?

A

There is a phenomenon in genetics referred to as X chromosome inactivation, this means that in the body of females, some of your cells are using one of the two X chromosomes, and other cells are using the other.
Depending on when X chromosome inactivation occurs during development, you can end up with large chunks of your body that are expressing one X chromosome, while the others are expressing the other.
-The genes that control pigmentation in calico cats are on the X chromosome, and when X chromosome inactivation occurs very early on in the embryo and there are very few cells you can end up with very chunky inactivation, hence why the cat has a complete split down the middle on her face.
This can also happen in human females, in these very rare cases you can end with a human female who has Protonopia in one eye, but the other eye has a functioning copy of the Opsin, and have Tritanopia with the good eye.

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28
Q

How can you test one’s colour vision?

A

Psychophysical examination can be performed to test the Neutral Point

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29
Q

What is the Neutral Point?

A

The Neutral Point is where there’s is a complete lack of colour perception, it’s Achromatic, it is where the two remaining cones have equal activity.

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30
Q

People with Protanopia have ___ Wavelength Cone and are missing ___ Wavelength Cone.

A

S & M // L

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31
Q

What is the Neutral Point for people with Protanopia?

A

492nm

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32
Q

For a Protanope, anything that is shorter than 492nm appears tinted ___, and anything that is longer, which is differentially activating the M cone, appears to be ___. But when these two cones have equal activity, which is more or less in the middle, this leads to a totally ___ at 492 nm.

A

blue // yellow // Achromatic perception with no colour

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33
Q

What is Deuteranopia?

A

Deuteranopia occurs when a person is missing the Medium-wavelength cone

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34
Q

Is Deuteranopia sex-linked?

A

Yes. 1% of males and .01% of females. Both the M and L wavelength cones genes are on the X chromosome, and so Deuteranopia is also sex-linked

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35
Q

What is the Neutral Point for someone with Deuteranopia?

A

498nm

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36
Q

For a person with Deuteranopia, the ___ Wavelength cone is missing, so anything that is S wavelength is seen as ___, and anything that is L wavelength is seen as ___. Right in the middle, because the M wavelength is missing, is a little higher, this is where you get 498nm neutral point where all chromatic information is absent.

A

M // blue // yellow

37
Q

What is Tritanopia?

A

Tritanopia occurs when a person is (probably) missing the Short-wavelength cone

38
Q

Is Tritanopia sex-linked?

A

Yes, -.002% of males, .001% of female

39
Q

What is the rarest form of colour deficiency?

A

Tritanopia

40
Q

Why don’t we know exactly why Tritanopia occurs?

A

Because it is hard to diagnose and hard to test

41
Q

In Tritanopia, the ___ Wavelength Cone is missing, and the point in which the ___ are equally activated is much higher, creating a neutral point of 570nm

A

S // M pigment and L pigment

42
Q

What is Anomalous Trichromatism?

A

This is when an individual has 3 types of Cones, but one opsin has a slightly shifted absorption spectrum

A person who needs to mix a minimum of three wavelengths to match any other wavelength in the spectrum but mixes these wavelengths in different proportions than a trichromat.

43
Q

What is Anomalous Trichromatism?

A

This is when an individual has 3 types of Cones, but one opsin has a slightly shifted absorption spectrum

44
Q

Anomalous Trichromatism happens more frequently with the ___ Wavelength Cone(s), not as much with the ___ Wavelength Cone(s)

A

M & L // S

45
Q

For someone with Anomalous Trichromatism, there’s a very small difference between the photoreceptors expressing the ___ or ___ pigment, so this means they have similar activations.

A

Green // Red

46
Q

Individuals with Anomalous Trichromatism are not as good at discriminating wavelengths that are ___, especially in the ___ range.

A

close together // Longer

47
Q

Who proposed the Opponent Process Theory of Color Vision?

A

Ewald Hering (1834-1918)

48
Q

Why was The Opponent Process Theory of Color Vision not initially taken as seriously as the Trichromatic theory?

A

Because the initial evidence consisted of anecdotal and introspective reports, as well as these hard-to-quantify after image effects.

49
Q

There is a characteristic pairing of colours for ___.

A

Afterimages

50
Q

Red creates a ___ Afterimage result (and vice versa).

A

Green

51
Q

Blue creates a ___ Afterimage result (and vice versa).

A

Yellow

52
Q

Black creates a ___ Afterimage result (and vice versa).

A

White

53
Q

The Opponent Process Theory posits that there is some kind of ___ nature between specific colour types.

A

opponency/opposite

54
Q

Opponent Colours tend to be on ___ of the Colour Wheel.

A

Opposite sides. This can change/depend on who draws the Colour Wheel

55
Q

What are Colour-Scaling Introspection experiments?

A

A type of evidence that Herring used the most for Colour Opponency

56
Q

How did Colour-Scaling Introspection experiments work?

A

Subjects were asked to imagine a colour of a single wavelength, and describe how easy or hard it was to imagine a mix of colours based on their names.

Given a colour consisting of a single wavelength, subjects never describe the colour yellowish-blue or greenish-red.

57
Q

What is a reliability issue with Herring’s Colour-Scaling Introspection experiments?

A

This type of introspection is not convincing to everyone because you could imagine that these subjects were being very cooperative, and were just telling Herring what he wanted to hear.

58
Q

What changed opinion on Opponent Process Theory?

A

Opponent Process theory was not taken very seriously until there was Electrophysiological data which provided very strong support for the pairing of Red-Green, Blue-Yellow, and Black-White.

59
Q

How did Pier Lenny of NYU investigate colour-processing in the Retina beyond just the Photoreceptors?

A

By looking at Ganglion cells as well as neurons in the LGN

60
Q

What did Pier Lenny find when investigating colour-processing in the Retina, Ganglion cells, and neurons in the LGN?

A

They found neurons that had this pairing, R-G, B-Y, and B-W

They coded these Receptive Field types using +’s and -’s and the letters for the given colour.

61
Q

An R+ G- indicates that the neuron is ___ by Red and ___ by Green. This creates what is called ___.

A

excited // inhibited // Single Opponency

62
Q

In Simplified Single-Opponent neurons, if you have a Bipolar cell that is receiving Inhibitory input from an M Wavelength Cone and Excitatory input from an L Wavelength Cone, you would have excitation when there are ___ Wavelengths, and inhibition when there are ___ Wavelengths.

A

L // M

63
Q

In Simplified Single-Opponent neurons, right in between Green and Red is Yellow, so M and L wavelength cones can pool their Excitation in an Amacrine cell which can then Inhibit the Bipolar cell to create a Y-, and S wavelength cones can send excitation to that bipolar cell to become the B+. This leads to a ___ pattern of activation.

A

B+ Y-

64
Q

Why do you see a Red Afterimage after looking at Green for a while?

A

When you stare at Green for a long time, it is selectively bleaching the Green photopigment, so they are less able to send their signal to these Bipolar cells

65
Q

Simultaneous colour contrast cannot be explained by ___, it requires some additional mechanism beyond what is happening at the Retina and LGN, so something has to be happening in the ___.

A

Single Opponent cells // Cortex

66
Q

What is the steps of understanding colour perception?

A

The function of photoreceptors which are explained by the Trichromatic Theory of Colour Vision → Other Retinal cells like the Bipolar cells, to create single Opponent Receptive fields which are explained well by the Opponent Process theory → Neurons in the Primary Visual Cortex which are required to explain the simultaneous colour contrast.

67
Q

In the Primary Visual Cortex, there is evidence that there are ___ just like the kind in LGN, and those are thought to be for filling in colours within ___ regions of space.

A

Single Opponent cells // large

68
Q

What is a Double Opponent Receptive Field?

A

Where instead of just having M+ on one portion and L- on the other, there is M+ L- in one region and L+ M- in the other region.

Red creates excitation in Red area and Red in Green area creates inhibition.

Neurons that have receptive fields in which stimulation of one part of the receptive field causes an excitatory response to wavelengths in one area of the spectrum and an inhibitory response to wavelengths in another area of the spectrum, and stimulation of an adjacent part of the receptive field causes the opposite response.

69
Q

What is the purpose of Double Opponent Receptive Fields?

A

This extra structure that is elaborated in the Primary Visual Cortex is thought to be important for perceiving colours at boundaries, the boundaries between two colours, which is exactly what is produced when the simultaneous colour contrast Afterimage is produced.

70
Q

What are the suggested functions of V1 colour cells?

A

Single Opponent cells: Perceiving colour within regions

Double Opponent cells: Perceiving colour boundaries

71
Q

What is Cerebral Achromatopsia?

A

A type of Cortical colour blindness (colour vs. wavelength) A loss of color vision caused by damage to the cortex.

72
Q

Most subjects with Cerebral Achromatopsia can still detect the ___ between 2 equally bright (equiluminant) colours.

A

border

73
Q

What does it mean if two colours are Equiluminant?

A

It means they are equally bright

74
Q

When two different colours that are equiluminant are viewed through a b&w camera, you’d see them as looking ___.

A

the same

75
Q

People with Cerebral Achromatopsia would view both sides of two side-by-side equiluminant colours as grey, but could still identify the border between the two colours, so it appears they’re still able to use ___ even though it no longer produces the percept of colour.

A

Wavelength

76
Q

Someone with Cerebral Achromatopsia would describe all colours as looking like ___.

A

shades of Grey.

77
Q

Cerebral Achromatopsia is often associated with other deficits like ___.

A

Prosopagnosia

78
Q

What is Prosopagnosia?

A

You can identify the features of a face but cannot use that info to identify whose face you are looking at.

79
Q

Most researchers believe that colour perception arises from the cooperation between ___ and that there is not one ___ that when damaged will remove colour vision altogether.

A

Multiple Cortical areas // Module

80
Q

fMRI studies done by Cavina-Pratesi et al. (2010) using a delayed-match-to-sample task indicate that likely, colour, texture, and shape are all processed together in some kind of Module down the ___ instead of having colour isolated to a specific module

A

Ventral/Temporal Stream/”What”

81
Q

How did Cavina-Pratesi et al. (2010) delayed-match-to-sample task work?

A

You’re presented with one sample at first, and then some time later you’re presented with another sample, and you have to decide whether it matches or not.

The experimenters use weird, abstract shapes, and got the subject to determine a match based on texture (blue), color (green), or shape (red).

Depending on what criterion the subject was using, different parts of the brains were activated either by texture, colour, or shape, or all three

82
Q

What did the fMRI’s in Cavina-Pratesi et al.’s (2010) delayed-match-to-sample tasks show?

A

fMRI signals showed regions activated by texture, colour, shape, or all three

83
Q

Rod Monochromats confound ___ for ___.

A

intensity // wavelength

84
Q

Rod Monochromats fall into the trap for the ___.

A

Principle of Univariance

85
Q

What is the Neutral Point for people with Tritanopia?

A

570nm

86
Q

Being a Chimera is caused by ___.

A

X chromosome inactivation

87
Q

Can males and females both be Chimeras?

A

No, only Females can be Chimeras

88
Q

What does it mean when a Female has X Chromosome Inactivation?

A

Some of your cells are using one of the two X chromosomes, and other cells are using the other.
Depending on when X chromosome inactivation occurs during development, you can end up with large chunks of your body that are expressing one X chromosome, while the others are expressing the other.

89
Q

What can happen in the eyes of someone who is a Chimera?

A

In very rare cases you can end with a human female who has Protonopia in one eye, but the other eye has a functioning copy of the Opsin, and have Tritanopia with the good eye.

PSYO2150 - Midterm #2 - Perceptual Processes (15 decks)

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