Colour Vision Theory Flashcards

1
Q

What is colour vision?

A

ability to differentiate between wavelengths of light within visible light

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2
Q

How can we detect different colours?

What is the Principle of univariance?

A

Ability to detect difference in colour is due to cone response to light.
Multiple cones mean colour info is known bc they respond to different wavelengths - comparing the response @ RGC level allows us to perceive which colour we are seeing.
e.g. if only L cones are activated, then it’s known that it’s red light even though no wavelength info is present

The wavelength info is lost, but intensity info is kept

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3
Q

What are the three opponencies?

A

Blue/yellow
Green/red
Black/white

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4
Q

What is the set up of a blue on cell?

A

Not centre surround

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5
Q

What is the set up of a red on cell?

A

Centre surround

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6
Q

Where is the receptive field of a yellow on cell?

A

In the LGN

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7
Q

What is trichromatic theory and how was it proven?

A

Colour vision relies on 3 receptors
Proven using colour matching experiments which found that any test colour could be matched by combining 3 other wavelengths (sometimes 2)

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8
Q

Why can’t colour be seen when there’s only one cone?

A

Principle of univariance - more than one cone needed in order to compare signals as wavelength info is lost.

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9
Q

How does a monochromat perceive different wavelengths?

A

Higher wavelength receives more intense reaction as sensitivity to higher wavelengths is increased

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10
Q

How can a monochromat tell if a light is just brighter or a different wavelength?

A

They can’t - the PR will respond the same if the brightness of a lower wavelength is increased as it would to a stimulus of a higher wavelength

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11
Q

What did Hering’s colour experiments conclude?

A

Four colours are perceived and are opponent to each other (i.e. have shared pathways which respond to the stronger colour)

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12
Q

What can happen if you view a colour for an extended period of time?

A

Colour aftereffects
Adaptation time causes pathway to ‘get used’ to viewing that colour. When the colour is removed, the opponent colour is seen bc there is reduced sensitivity of the colour which was just being viewed, so it’s perceived that you are viewing the opposite.

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13
Q

At what level is trichromacy theory correct?

A

Photoreceptors

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14
Q

At what level is opponency theory correct?

A

RGC

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15
Q

Where do M & L cone responses combine to create R-G opponency?

A

RGC receptive fields

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16
Q

How is B-Y opponency created?

A

Responses from S cone and yellow input from M & L cones feeds into RGC receptive fields

17
Q

What is a R+G- RGC receptive field?

A

Red-on cell
Excitatory response to red
Inhibitory response to green
Red perceived when cell is excited

18
Q

What is a B+Y- RGC receptive field?

A

Blue-on cell
Excitatory response to blue
Inhibitory response to yellow
Blue perceived when cell is excited

19
Q

What is a Y+B- LGN receptive field?

A

Yellow-on cell
Excitatory response to yellow
Inhibitory response to blue
Yellow perceived when cell is excited

20
Q

Is the R-G chromatic channel parvo- or magnocellular?

A

Parvocellular

21
Q

Is the B-Y chromatic channel parvo- or koniocellular?

A

Koniocellular

22
Q

Is the achromatic luminance channel parvo- or magnocellular?

A

Parvocellular

23
Q

Which area of the brain processes colour?

A

V4

24
Q

Do blobs or interblobs perceive colour?

A

Blobs

25
Q

What do interblobs perceive?

A

Object form

26
Q

How do blobs and interblobs work together to form an image?

A

Parallel processing

27
Q

What could occur to an image if there is damage to interblobs?

A

Colour perceived, but unable to perceive the shape of the object

28
Q

Which layer do koniocellular neurones synapse in V1?

A

Layer 3

29
Q

Which layer do parvocellular neurones synapse in V1?

A

Layer 4C(beta)

30
Q

Where does chromatic and achromatic information separate in V1?

A

Post-synaptic projections from layer 4C(beta) to layer 3

31
Q

What is colour constancy?

A

Ensuring perceived colour stays the same in different illumination conditions

32
Q

What do double opponent cells do in V4?

A

Removes common colours to maintain colour constancy

33
Q

Which cells achieve colour constancy?

A

Double opponent cells