Do blind people have a less developed visual cortex?

Question

I'm just curious, if they do not get visual input if their visual cortex is less developed than someone who gets direct visual input?

I'm wondering because we process a lot of information all at once through our vision, and I would guess that imagined visuals are less taxing to it. So blind people having only imagined visuals should have a less taxed visual cortex, so it wouldn't need to be overly developed. Is this right or wrong?

Do they end up compensating by having even better imagined visuals because their visual cortex still functions at full capacity no matter what?

By imagined visuals I mean visualizations using the mind.

Thanks so much in advance.

Answer 1

.....Your guess is correct. If a person is blind from birth, the visual cortex will not be stimulated during the critical developmental period in infancy when the neurons overgrow, then prune back, leaving the neurons most used. A blind person would have minimal neurons left after pruning.

Also, the more the cortex is used, the more it is stimulated to create neural pathways to establish memory and processing patterns. This means lots of dendrites growing to make the necessary connections. Lack of use means no dendritic growth.

The end result is a much less developed occipital area.

But this is only one area of the brain. Other areas of the brain should develop normally. Also the brain has "plasticity," meaning if necessary, an area of the brain can be used for something other than its usual purpose. Some blind people may develop and use their visual cortex for other functions, if necessary.

Answer 2

Recall from my previous answer that the visual cortex is primarily dominated by its connections to the optic nerves. What you see with your eyes dominate what you will 'see', unless you have shifted attention during daydreaming etc.

Also recall from my previous answer to your question that the visual cortex is also connected to the cerebral cortex via the 'high' route; and to the temporal lobes via the 'low' route, which explain memory, thought, emotions, sound and speech influences to visual processing.

Whereas blind people might not receive primary visual information from the eyes, resulting in the visual cortex being less developed and smaller, it still receives information from these other routes and processes it in its own way. Thus explaining why the visual cortex is less developed but still developed in blind people as explained by Jennifer on develop of neural connections from usage.
Perhaps their 'image construction' of memories, sounds, emotions and words are more vivid than those with normal vision.
http://www.pistolwimp.com/media/52410/
visit here to see a documentary on Ben Underwood: a blind boy (not from birth) develops echo-location.

Also, based on this, i might guess that for normal sighted individuals; the 'imagined vision' during dreams and imagination are primarily influenced by what you experience through your eyes. Our 'imagined vision' becomes very close to 'eye vision'.
For blind people, their 'imagined vision' would probably be primarily influenced by sound and language, followed by touch and smell (senses come first), and subsequently by memory and conscious thought.

Answer 3

The human brain is remarkably adaptive. If someone is blind from birth the part of the brain that would be used for the visual cortex is probably used for something else, unless it is itself damaged and is the cause of the blindness.