T8: Visual development Flashcards
Describe the role of visual stimulation on the development of the visual cortex during the critical period
Visual development occurs during the critical period
Stimulation is required to allow synapses to form between the thalamus and the visual cortex
How can blindness occur due to a lack of stimulation during the critical period
If there is a lack of visual stimulation in one or both eyes, synapses that do not receive action potential during the critical period are lost and not reformed
Describe what is meant by a critical period
A period at the start of a mammals life in which the mammal must receive adequate visual stimulation in order for full visual development
Explain how the Hubel and Wiesel experiment with kittens showed evidence for a critical period
Newborn kittens had one eye sutured shut and after 6 months the eye was reopened
This showed a low number of neurones reacting in the eye sutured shut and a high number reacting in the eye that was opened. Macroscopic observation showed that ocular dominance columns for the eye that had been sutured shut had shrunk and vice versa
In adult cats that had their eyes sutured shut, when their eyes were opened their vision returned to normal
Explain how the Hubel and Wiesel experiment with
primates showed evidence for a critical period
Sutured their eyelids shut for the sixth months of their lives. Animals had lost all useful vision in the eyes that had been deprived
What would happen if a child that was born with congenital cataracts had them removed
They would still be blind due to the lack of visual stimulation during the critical period meaning that neurones connecting the thalamus and ocular dominance columns were not active
What happens if catarcts caused by old age were removed
Vision would return to normal
