The 'critical window' (11)

Question 1

What is a critical window in regards to vision?

Answer 1

A period in early life where it is critical to develop the visual cortex. If it is not developed in this window there will be permanent visual impairment.

Question 2

What is the visual cortex - describe it.

Answer 2

• an area of the cerebral cortex
• neurones in the visual cortex recieve info from either the right or the left eye
• these neurones are grouped together into columns called occular dominance columns.

Question 3

What two types of occular dominance columns are there?

Answer 3

Right occular dominance columns and left occular dominance columns.

Right occular dominance columns recieve info from the right eye.

Left occular dominance columns recieve info from the left eye.

Question 4

How does visual stiumlation organise the neurones during the critical period?

Answer 4

• born with many neurones in the visual cortex
• neurones need visual stimulation in order to become properly organised
• during the critical period, synapses which recieve visual stimulation and pass nerve impulses to the visual cortex are retained
• synapses which don’t recieve any stimulation are removed
• so if the eye is not stimulated during the critical period the cortex will not develop properly.

Question 5

What human evidence do we have for the critical period?

Answer 5

Cataracts

• cataracts temporarily impair vision however if they occur during the critical period vision will be permanently impaired