Cortical Area V1

Question 1

Where do ganglion cells terminate

Answer 1

LGN of thalamus- primary visual pathway
Superior colliculous- saccades
Pretectum- Pupillary responses
Hypothalamus- circadian control

Question 2

What is central homonymous defect and where is the lesion at

Answer 2

VF defect in central vision OU. Damage to the lesion at tip of occipital lobe

Question 3

Most of the LGNs input is from

Answer 3

Most from V1
RGC 80% parvocellular, 20% magnocellular.

Activation of V1 neurons depends completely on LGN input, but v1 receives many other cortical and subcortical inputs.

Question 4

6 layers of the LGN

Answer 4

1- contra lateral. Magnocelllular. On and off.
2- ipsilateral. Magnocellular. On and off.
3- ipsilateral. Parvo. Off.
4- Contralateral. Parvo. Off
5- ipsilateral. Parvo. On.
6- contra lateral. Parvo. On.

Question 5

Retinotopic Mapping. What portion of the VF does each correspond to?

Posterior LGN
Anterior LGN
Lateral/inf LGN
Medial/Superior LGN

Answer 5

Central visual field
peripheral visual field
superior VF
Inferior VF

Question 6

Ratio of Relay to interneurons

Answer 6

Relay: Interneurons 4:1

Question 7

Relay cells receive input from where?
-what NT does it use
Interneurons do what?
-What NT does it use?

Answer 7

Relay: receive input from sources outside the LGN. Including magnocellular, parvocellular, and koniocellular. Uses glutamate. Excitatory.

Interneurons help with input/output within the LGN.
GABA. Inhibitory.

Question 8

Central sulcus separates what portions of the brain

Answer 8

Frontal and parietal

Question 9

Sylvian/lateral fissure separates what portions of the brain

Answer 9

temporal from frontal and parietal

Question 10

Transverse fissure separates what portions of the brain

Answer 10

Cerebellum from occipital lobe

Question 11

Why is V1 called the striate cortex?

Answer 11

Has a stripe of myelin down the center called the line of gennari. Projects into layer 4B from 4C alpha

Question 12

First site along primary visual pathway that has binocular neurons- they can respond to either eye or both

Answer 12

V1

Question 13

Cortical mag

Answer 13

mm of cortex/deg of VF

Question 14

Inverse cortical mag

Answer 14

deg of VF/mm of cortex.

Question 15

Layers of V1

Answer 15

Layer 1: Supergranular. Synapses are sending info to each other.

Layer 2,3,4A,4B: Supragranular. Send excitatory output to other cortical areas. Koniocellular cells send axons to blob cells in layer 3.

Layer 4C: Granular layer. LGN sends input here from M and P cells. Within this layer, signals from the R and L eye are separated. Monocular.
(parvo–> 4C beta. Magno–> 4C alpha)

Layer 5, 6: Infragranular. Send output to cortical and subcortical areas.

Question 16

Ways to classify visual cortex cells.

Answer 16

Anatomical:
Spiny- excitatory. Glutamate.
Smooth- Inhibitory. Gaba.

Functional classifications:
Simple
Complex
End stopped

Question 17

Simple cells of V1

Answer 17

Little or no spontaneous activity.
Edge detects (-+-) or line detectors (-+)
Spatially linear elongated receptive fields. Not center surround.
Either mono or bino
Show spatial frequency (size) specification

Question 18

Complex cells of V1

Answer 18

Spatially non linear 
High spontaneous activity 
More numerous than simple cells 
Strong orientation specificity (tuning) 
May show true direction of motion
Most binocular

Question 19

End stopped cells of V1

Answer 19

If the stimulus gets beyond a certain length, the cell does not increase its response.

Question 20

What is the simple cell receptive field made up of? What is the complex cell receptive field made up of?

Answer 20

Simple cell receptive field made of LGN input.

Complex cell receptive field made from simple cell input.

Question 21

Huber and Wiesel classification of binocularity

Answer 21

1 can only respond to info from the contralateral eye.
2-3 respond stronger to the contralateral eye but can respond to ipsi.
4 equally responds to ipsi and contralateral.
5-6 respond to ipsilateral stronger but can respond to the contralateral one.
7 can only respond to ipsi