The visual system

Question 1

Connections from the retina to the LGN and Superior Colliculus are _____

Answer 1

Parallel

Question 2

Connections from the LGN to the Cortex are _____

Answer 2

serial

Question 3

What happens if the optic chiasm is cut?

Answer 3

Tunnel Vision

Question 4

How is the LGN organized?

Answer 4

In layers (6)

Question 5

From layers 1 to 6 of the LGN, describe the type of cells, present

Answer 5

1 - Magno (C)
2 - Magno (I)
3 - Parvo (I)
4 - Parvo (C)
5 - Parvo (I)
6 - Parvo (C)

Question 6

Magno cells of the LGN are similar to _____ Ganglion cells and Parvo cells are similar to _____ RGCs

Answer 6

Magno = Parasol
Parvo = Midget

Question 7

What is the point of the LGN?

Answer 7

We don’t know (possible relay station)

Question 8

Where do most optic neurons terminate?

Answer 8

In the 4C layer of the primary visual cortex

Question 9

What are the 5 properties of V1?

Answer 9

Retinotopy
Cortical magnification
Ocular Dominance
Orientation selectivity
Direction selectivity

Question 10

What is retinotopy?

Answer 10

The centre of V1 represents the centre of vision on the retina (recall images are flipped and reversed)

Question 11

What is cortical magnification?

Answer 11

The neurons representing the fixation point are much more exaggerated than the periphery

Question 12

True/False? V1 Cells respond best to bars of light

Answer 12

True (several simple cell RFs in a straight line connect to their respective LGN cell, which feeds into a single V1 cell, whose output is proportional to the amount of simple RGCs acviated)

Question 13

True/False? If a V1 Cell doesn’t receive light at exactly the orientation it was optimized for it won’t fire

Answer 13

False (normal distribution)

Question 14

True/False? All V1 cells have an optimal direction

Answer 14

False, some cells are nondirectional

Question 15

Describe the organization of V1 cells

Answer 15

Columnar
Increasing depth reveals neurons representing the same field, whereas moving across reveals neurons whose RFs are shifted

Question 16

What is the difference between Monocular and Binocular neurons?

Answer 16

Monocular neurons will only fire if a specific eye is stimulated, whereas Binocular neurons fire only if both eyes are stimulated

Question 17

What is the Ice Cube model?

Answer 17

The (false) model for the visual cortex, where different layers are stacked according to their orientation. each layer divided based on their LGN receptor