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Severed Optical Nerves Can Be Made To Grow Again
Anonymous Coward writes: "It is being hailed as one of the most significant advances in nerve regeneration in a decade. After severing an optic nerve in rats, neurologists have found a way to reconnect it to the brain so that it once again transmits normal electrical signals. As reported in the New Scientist this achievement is a first in mammals, and may hint at ways of reversing some types of blindness in people. Scientists also hope to use a version of the technique to treat people with spinal cord injuries.
I once heard Oliver Sacks talk about somebody who had been blind their whole life (due to completely opaque cataracts, I believe). A new surgery technique restored the fellow's sight. But when he woke up from surgery, all he could see was an overwhelming mass of incomprehensible color. He couldn't distinguish faces, object, or even simple shapes.
His eyes, it turned out, were functioning perfectly. But because he has been blind during infancy, the visual parts of his brain had never developed -- he had never learned to see.
He did slowly learn, but it was agonizing for him. His newfound sight was overwhelming and sent his brain into chaos. After a long time, with tremendous effort, he could shave for a minute or two in front of the mirror -- but it was absolutely exhausting, and had to finish with the lights off.
Eventually, an unrelated optical infection threatened to take his sight, and he chose to let it run its course. Returning to blindness was a tremendous relief.
Perhaps slightly off-topic, but fascinating!
I thought the idea that it was immune system stimulating growth pretty interesting. The immune system releases a lot of signaling molecules at all stages. I'm not an immunologist per se, but I've never heard of any of them stimulating growth, but that certainly doesn't rule out the idea.
The article said that it was just inflammation that induced growth. I somehow doubt that, since everyone who's ever had irritated eyes has felt the fun of histamines and the primary immune response in action. If that sort of thing could make the blind see again, I'd be really surprised, even if it is on a larger scale.
If it is the immune system, I'd bet on cytokines released by helper T cells (those things that HIV targets) simply because these cells release a ton of stimulants. This may be triggered by the nonspecific inflammation like the author suggested, but I'd bet on the helper T as actually secreting growth signal.
If it is possible to use the immune system to regrow neurons, it's very likely applicable in other parts of the body too.
"I may not have morals, but I have standards."
One thing I have to wonder about is if the nerves grow up the 'wrong' pathway, and how long it will take the brain to sort it out.
When I was 15 years old, I put my hand through an old glass door while trying to open it. The glass sliced through my right wrist, severing pretty much everything (apart from about half of one tendon). I probably don't have to mention the large quantities of blood that went everywhere.
Six hours of microsurgery, and it was put back together again...followed by three months of three hours a day physiotherapy.
The thing I found fascinating was that when the median nerve [0] (the nerve that runs up the middle of your wrist and supplies your index finger to thumb and half your palm) is that some of the nerves went the wrong way. I could stroke part of one finger, and the sensation would come out somewhere else - like a different finger, or a different side of the finger. It was...well...very weird.
However, it didn't take long for the brain to fix it. After a short while, the brain learned the error, and sensations came out in the expected place.
It's one thing when this happens to fingers - but I wonder if you'd need some kind of "optotherapy" to coach the brain to fix the image problems you'd get with optical connections wired differently to how they were before.
[0] Movement of the fingers is controlled by the muscles in the forearm. The median nerve does sensation.
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