Development of Visual Cortex

Question 1

What is the indirect visual pathway?

Answer 1

Retina - lateral geniculate nucleus (LGN) of thalamus - visual cortex

Question 2

What is the direct visual pathway?

Answer 2

Retina - superior colliculus

Question 3

What is the importance of the orientation selectivity of the visual cortex?

Answer 3

Enables edge detection - for movement detection and object separation

Question 4

What is the importance of the direction selectivity of the visual cortex?

Answer 4

Enables detection of movement direction

Question 5

Where are retinotopic maps found?

Answer 5

Superior colliculus

Visual cortex

Question 6

Which molecular axon guidance cues are important in retinotopic map formation?

Answer 6

Eph/ephrins

Question 7

Which types of neuronal activity are important for refining retinotopic maps?

Answer 7

Retinal waves

Spontaneous activity

Question 8

What is the effect of EphA/ephrinA interaction?

Answer 8

Repulsive

Question 9

What is the effect of EphB/ephrinB interaction?

Answer 9

Attractive

Question 10

What is the effect of an ephrinA KO in mice?

Answer 10

Less organisation and branching of axons in retina

Question 11

What are the characteristics of stage 1 of retinal waves?

Answer 11

Before birth

Slow and infrequent

Question 12

What are the characteristics of stage 2 of retinal waves?

Answer 12

Birth to P10-12
Driven by ACh
Relatively slow and infrequent
Critical for retinotopic map refinement

Question 13

What are the characteristics of stage 3 of retinal waves?

Answer 13

P10 to eye-opening
Driven by glutamate
Fast

Question 14

What is the effect of an nAChR subunit beta2 KO?

Answer 14

Changes stage 2 activity patterns in retina
Still some axon organisation - due to guidance cues
Larger regions of retinotopic map in superior colliculus activated by stimulus - separate areas less clearly define

Question 15

What is required for orientation tuning of visual cortex neurons to develop?

Answer 15

Spontaneous activity

Question 16

Is input required for direction tuning development in the superior colliculus?

Answer 16

No

Question 17

Is input required for direction tuning development in the visual cortex?

Answer 17

Yes

Question 18

What causes the segregation of inputs from each eye in the LGN?

Answer 18

Entirely activity-dependent

Question 19

What is the effect of monocular deprivation on visual cortex neurons?

Answer 19

Ipsilateral monocular cells and binocular cells come contralateral monocular

Question 20

What is the importance of normal vision and why?

Answer 20

Maintenence of normal visual cortex function

Due to experience-dependent plasticity - eye inputs susceptible to changes in visual experience