1. Colour Vision Theory

Question 1

Rods give what type of vision?

Answer 1

Scotopic Vision- NOT used in colour vision (this is vision of the eye in low- light conditions).

Question 2

Rods or Cones, Which one is found more in the retina?

Answer 2

Rods

Question 3

What are the 3 types of cones?

Answer 3

1. S-blue
2. M-green
3. L-red

Question 4

Different types of cones are sensitive to different parts of the..?

Answer 4

Visual Spectrum

Question 5

Number of colours you can discriminate is defined by the ?

Answer 5

Number of cones

Question 6

Human visual range?

Answer 6

390-700nm

Question 7

Describe the sensitivity of cones?

Answer 7

Each cone has an individual sensitivity.

Question 8

What was the colour matching experiment+ Young’s theory?

Answer 8

Any test wavelength can be matched by mixing 3 other wavelengths.
CONCLUSION: Colour vision depends on a 3 receptor mechanism.

Question 9

Why can’t we see colour with only 1 cone?

Answer 9

Electric potential difference between inside and outside the cell.

Question 10

What is the principle of univariance?

Answer 10

All wavelength information is lost.

Question 11

You can not see colour with only 1 cone is related to which concept?

Answer 11

Principle of univariance

Question 12

What is meant by monochromat?

Answer 12

Only 1 type of photoreceptor

Question 13

What is the minimum amount of cones required to perceive colour?

Answer 13

2

Question 14

Why can’t you see in the dark?

Answer 14

You only have 1 type of rod, so you have nothing to compare against

Question 15

What is the opponency theory?

Answer 15

Colour is processed by bipolar channels. Referred to as red-green, blue-yellow and black-white.

Question 16

Are trichromatic and opponency theories related?

Answer 16

Trichromacy: occurs at receptor level.
Opponency: First occurs at the ganglion cell and LNG level. Then the colour opponency channel input from different cones.

Question 17

Optic radiations connect?

Answer 17

LGN to higher cortical areas (temporal lobe).

Question 18

Pathways from retina to LGN

Answer 18

Parvocellular pathway: R-G Chromatic channel. Achromatic luminance channel.
Koniocellular pathway: B-Y Chromatic channel.

Question 19

Where does visual processing in the cortex start?

Answer 19

V1

Question 20

How are cells in V1 arranged? And what does the arrangement correspond to?

Answer 20

In hypercolumns- each correspond to a retinal point.

Question 21

Neurones from koniocellular layers synapse in?

Answer 21

Layer 3- known as “blobs”

Question 22

Neurones from parvocellular layers synapse in?

Answer 22

Layer 4Cβ then post-synaptic projections to layer 3.

Question 23

Role of blobs

Answer 23

Analysis of object colour

Question 24

Role of interblobs

Answer 24

Analysis of object form

Question 25

Describe how the processing of achromatic and chromatic information occurs?

Answer 25

Processed in parallel

Question 26

V4 receives input from?

Answer 26

Blobs and interblobs

Question 27

Role of V4

Answer 27

Colour constancy

Question 28

Role of colour constancy?

Answer 28

Ensures colour perceived remains same under different illuminations. Assesses colour of overall visual field. Processed in V4.

Question 29

Describe why S-cones are sensitive to blue light?

Answer 29

Within the photoreceptive cells, the photopigment is sensitive to blue light

Question 30

Thomas Young’s theory was demonstrated by?

Answer 30

A series of experiments with colour matching.

Question 31

Monochromats can not discriminate between different wavelength of colours, but can still identify the difference, how?

Answer 31

Certain colours will dark, others light.

Question 32

How many cones do you need atleast to perceive colour?

Answer 32

2

Question 33

What is a monochromat?

Answer 33

They only have 1 type of photoreceptor

Question 34

Photoreceptors are what type of cells?

Answer 34

Light sensitive cells

Question 35

Are cones specific to a particular wavelength?

Answer 35

Cones have a range of wavelengths to which they are sensitive but have the highest sensitivity to a particular wavelength.

Question 36

Can monochromats make colour discriminations ?

Answer 36

No, certain colours will appear darker.

Question 37

What response is perceptive with RED- ON Cells?

Answer 37

1. Red is perceived when cell is excited.
2. No perception when the cell is inhibited.

Question 37

Is it true that opponent cells have receptive fields?

Answer 37

YES- both in the retina & LGN

Question 38

Describe the B-Y opponent cell

Answer 38

The receptive field is NOT centre-surround.
1. You perceive blue when cell is excited.
2. No perception when cell is inhibited.

Question 39

Y+B cells receptive field is identified at?

Answer 39

LGN

Question 40

What is required to tell 2 colours apart?

Answer 40

Receptive field that contributes to a type of cone and another region next to the cone that contributes to other types of cones.