I told a friend this and he disagreed. My point to him was that brain and vision integration have to be accomplished at a fairly young age to be of any use. Attaching a functioning vision system to brain that has never learned to accommodate it is not going to yield a properly functioning, or even minimally useful integrated eye-brain vision system as an adult.
Who is right?
Not all blindness is caused by problems with eyes and optic nerves; there could also be brain damage.
Generally true, the “use it or lose it” adage. The occipital lobe would not have developed properly to facilitate normal vision. Some visual sensation may develop, but probably not beyond rough form or contrast recognition.
I believe you are right, overall. Neural vision pathways and processing centers develop during infancy and early childhood based on use.
But the full story behind how this development occurs (or goes awry) is not known by any stretch, so there could be effects we’re not aware of for some folks.
From what I recall, in real world examples where the advance of medicine has allowed sight to be given to blind-from-birth people you are correct, and they can’t interpret what they see. IIRC some asked to be blinded again it was so unpleasant.
Here is a story of a guy who got vision back but his brain could not process all the info
From Darkness to Light: Blind Man Struggles After Regaining Sight - ABC News
I am trying to remember where I read this, but so far I’m still drawing a blank - but apparently one of the issues in those sorts of cases is the brain’s inability to interpret distance/depth. Everything appears to be on the same plane.
It’s my understanding that new theories of brain development posit that there’s a lot more plasticity in how the brain works, even as an adult, than was previously thought, and that the brain can be taught to recognise new input given time (LOTS of time) and patience.
For instance, experiments have been done on totally blind people where a camera attached to their heads was rigged up to an array of tiny heating elements on their backs (nice big flat surface), and the picture translated into a “heat” picture - dark for cold, light for hot. Not only could the subjects learn to interpret this picture and navigate around obstacles with it, but the part of the brain which would normally be used for sight (and was being used for all sorts of other things since no visual input was coming through) was in fac the one being activated.
I have no doubt however that in the short term it would be hard hard work and you certainly couldn’t just connect up all the bits and expect the vision to start working automatically.
Didn’t they do a classic science experiment decades ago where they took newborn lab monkeys and sewed their eyelids shut? (I swear I’ve seen photos, probably in an animal-rights pamphlet or something.) IIRC, once they cut away the stitches and the monkeys - now much older - could open their eyelids, they were still blind, thus proving that the neural pathways are laid down very early.
Is it known what happens if, say, a three-year-old loses vision, and then gains it again 20 years later? Or any lag at all, really – not necessarily a toddlerhood-to-adulthood lag. Maybe an adult who went without sight for a decade, a ten-year-old who was sightless for three years, or something like that.
Read the link I posted above, it covers the exact question you asked.
Reading through it … don’t see much technical info, though. Unless I’m missing something, the excerpt in that link ends before he has the stem-cell surgery.
To give you more info on that case, the guy had a hard time with some tasks after he got his sight back. He could not really learn to read and had a hard time recognizing faces. The vision part of his brain doesn’t work because he did not use it when he was young.
Here is more info
http://www.cbsnews.com/stories/2003/09/03/earlyshow/living/main571462.shtml
His case is so unique that he was studied for a while by a college professor.
Thanks for that. It’s a fascinating field.
I look at my three-year-old son and think of him as being so “grown up” and developed in many ways … but really, he’s got a ways to go. And stories like May’s hammer that home.
I wonder how it would be for a twenty-something to lose sight and regain it years later?
The 1999 Val Kilmer movie At First Sight based on on the story To See And Not See by Oliver Sacks covers much the same territory (less well). I remember being amazed that the newly-sighted Virgil has to learn to tell the difference between an apple and a picture of an apple.
Colin Blakemore did that with kittens. It didn’t endear him to the animal rights people.
Is the experience of adults who receive cochlear implants at all parallel? If so, how well do those work in adults who are deaf since birth?
One thing that is different is deaf people can learn to talk and they can feel vibrations caused by sound.
This (restoring a blind person’s sight) has been done a number of times, going back as far as the 18th century. I would recommend Michael Morgan’s book Molyneux’s Question, which is about just this topic. (Unfortunately there is no preview on Google Books, but it looks like there is a new edition out this year. I read the original 1997 edition.) Anyway, the answer is not that straightforward. The patients involved clearly do get a lot of useful visual function from it, but it is not full, normal vision. Quite how good their restored vision will be depends on a lot of different factors. Also, it appears that they often become quite depressed afterwards, both because it is not nearly as wonderful and beautiful being able to see as they hoped (especially, I guess, as they can’t even see very well), and also because they often find they have gone from being some who has become well adapted to living life as a blind person, to an incompetent sighted person.
There are also a lot of issues about precisely when they went blind, and how blind they are. Many “blind” people actually have some limited degree of visual function, such as being able to tell daylight from darkness, or even being able to make out vague shapes and movements if the contrast is sufficiently high. Also, obviously, if they went blind after a few years as a sighted person, they will know what to expect, and their brains will have developed the necessary pathways (even if they have atrophied a bit in the meantime). As I understand it, it is actually quite rare for people to be blind from birth, and unless you do a detailed ophthalmic exam on a newborn you probably will not even realize that they are blind for quite a while, since new born babies are so uncoordinated and helpless anyway.