Perception of Colour and Motion

Question 1

In what layer of the cortex (V1) do M cells terminate?

Answer 1

4Ca

Question 2

In what layer of the cortex (V1) do P cells terminate?

Answer 2

4Cb

Question 3

What are the other 3 main outputs from V1 and the associated layers?

Answer 3

Layer 3 and 4B: to other (extrastriate) cortical areas
Layer 5: superior colliculus and pons
Layer 6: LGN

Question 4

What is the cellular pathway involved in detection of motion?

Answer 4

M ganglion cells project to magnocellular layers of LGN
M cells from LGN project to layer 4Ca of V1
Cells in layer 4Ca project to layer 4B

Question 5

When does mixing of ipsilateral and contralateral visual information occur?

Answer 5

After input into V1

Question 6

Describe the concept of “directional selectivity”. Where are neurons displaying directional selectivity found?

Answer 6

Some neurons show preference for the direction of motion of the target
In layer 4B, area MT

Question 7

What % of the cortex is involved in vision?

Answer 7

40%

Question 8

What are the 2 cortical streams of visual processing and what is each responsible for?

Answer 8

Dorsal pathway: where in the visual field an object is

Ventral pathway: what the object is (shape and colour)

Question 9

What is area MT and what is its role? Which stream is it associated with (ventral or dorsal)

Answer 9

Middle temporal lobe, associated with dorsal stream

For processing object motion

Question 10

From what cortical areas does area MT receive inputs?

Answer 10

V1 (specifically cells in layer 4B), V2, V3

Question 11

How is white observed?

Answer 11

Via red, green and blue light causing equal activation of the 3 types of cones

Question 12

What is a colour opponent centre surround?

Answer 12

Phenomenon exhibited by some P ganglion cells in which they are excited by 1 colour falling on their centre and inhibited by another falling on their surround

Question 13

What pairs of colours are compared (e.g. in colour opponent centre surround)?

Answer 13

Green vs. red

Blue vs. yellow

Question 14

What is area V4 and what is its role? Is it associated with the dorsal or ventral stream?

Answer 14

Associated with ventral stream

Important for perception of shape and colour (object recognition)

Question 15

From what cortical areas does area V4 receive inputs?

Answer 15

Blob and interblob regions of V1, via V2

Question 16

Are neurons in area V4 directionally selective?

Answer 16

They are both directionally selective and colour selective

Question 17

Where is area V4’s major output to?

Answer 17

Area IT (inferior temporal)

Question 18

What do neurons in area IT respond to? What is the major role of area IT?

Answer 18

Neurons respond to a wide variety of abstract shapes and colours
Important for visual memory and perception (especially of faces)

Question 19

What are the 3 groups of colour blindness?

Answer 19

Monochromacy
Dichromacy
Anomalous trichromacy

Question 20

What is monochromacy?

Answer 20

Individuals have only 1 type of cone

Question 21

What is dichromacy?

Answer 21

Individuals have only 2 functional cones

Question 22

What is anomalous trichromacy?

Answer 22

Individuals have all 3 cones, but 1 expresses abnormal pigment and doesn’t work as well as normal cones

Question 23

What are the 3 different type of inherited colour vision deficiency?

Answer 23

Protan
Deutan
Tritan

Question 24

Are M cells wavelength sensitive or insensitive?

Answer 24

Insensitive (do not detect colour)

Question 25

What is the relative frequency of rate of AP firing in R+G- ganglion cells when stimulated a) with R just at the ON centre, b) with R at the ON centre and at the OFF surround, and c) with R at the ON centre and G at the OFF surround? Give some explanation if required

Answer 25

a) Maximal excitation
b) Less excitation than in a) (green cones are excited by red light and so provide some inhibitory input, but not as much as would be produced by green light)
c) Maximal inhibition (low output - similar to no light)

Question 26

What is a protanope vs. a protanomal?

Answer 26

Protanope: no red cones
Protanomal: abnormal red cones

Question 27

What is a deutanope vs. a deutanomal?

Answer 27

Deutanope: no green cones
Deutanomal: abnormal green cones

Question 28

What is a tritanope vs. a tritanomal?

Answer 28

Tritanope: no blue cones
Tritanomal: abnormal blue cones

Question 29

What are some of the everyday deficits experienced by protanopes?

Answer 29

Fail to see red lights and signals as easily, and require larger stopping distances when driving

Question 30

What are some of the everyday deficits experienced by deutanopes?

Answer 30

Can confuse red and yellow traffic lights