Lecture 3: From LGN to Cortex

Question 1

What is the LGN?

Answer 1

Lateral Geniculate Nucleus

Question 2

How do nasal (parts closer to the nose) parts of retina project on the LGN?

Answer 2

Counter laterally

Question 3

How do lateral parts of the retina project on the LGN?

Answer 3

Ipsilaterally (on the same side)

Question 4

Where is the left visual field represented in the LGN and vice versa?

Answer 4

On the right side and vice versa

Question 5

Describe the layers in the LGN

Answer 5

There are 6 layers, 3 take info from the left eye, and other from right. The 6 layers are split into two, layers 1-2 and 3-6. More info on document.

Question 6

What is a retinotopic map

Answer 6

The order of neurones in the retina are preserved in the LGN.

Question 7

How do cells in the LGN treat different orientations?

Answer 7

Their receptive fields cannot discriminate between stimuli of different orientations (unlike those in the retina).

Question 8

What are the two specific cells in the LGN layers?

Answer 8

Mangocellular and parvocellular (that have centre surround receptive fields similar to ganglion cells).

Question 9

Where does the LGN project?

Answer 9

Primary visual cortex

Question 10

Are neruones in the V1 bi/monocular

Answer 10

Mostly binocular

Question 11

Why is input on a retinotopic map distorted towards the lateral part of the image?

Answer 11

Because more neruones are dedicated in the centre of the visual field (fovea) and less and less towards peripheral areas causing the cortical magnifcation.

Question 12

Describe the centre receptive fields of retinal ganglion cells

Answer 12

They have elongated receptive fields which means they respond best to lights in lines/bars or edges - if light shone in positively connected areas, activation would increase from basline

Question 13

Simple cell receptive fields

Answer 13

respond most optimally to certain properties due to the excitatory and inhibitory regions. This means you can accurately predict their response.

Question 14

What are population codes

Answer 14

A way to represent the activity of different oriented cells

Question 15

Compare the activity of two neruones, one optimally orientated to vertical stimuli with an intense, slanted stimulus, and one with a less intense vertical stimulus

Answer 15

Their activity would be the same because optimal but faint stimuli activate cell equally to suboptimal, intense stimulus

Question 16

What makes complex cells different to simple cells?

Answer 16

Their recpetive fields do not show excitatory/inhibtory regions so activity/receptive field profiles are not easily predicted. Also they approximately give the same response across whole receptive fields, not just in excitary/inhibtiory regions.