How to transplant a head

[MillCreek]

http://theweek.com/articles/590807/how-transplant-head

This would truly be a medical breakthrough if enough of the spinal nerves connected/regrew/fused to have meaningful control and sensation of the body.  And of course assuming that the patient wakes up cognitive.

[K Frame]

So, they're trying to create Democrats in the lab now?

We are so *expletive deleted*ed.

[Fly320s]

How is the spinal cord constructed?  Millions of individual nerves or one solid nerve that can handle millions of individual signals?

[K Frame]

I'm pretty sure it's bundles of individual nerves and associated tissues.

Most people don't know that the actual spinal cord doesn't extend the whole way down the spine. It only goes to about midback, where it tapers out into the various nerves for the mid and lower body.

At least that's how I think I remember it being described in something I saw...

[TommyGunn]

How is the spinal cord constructed?  Millions of individual nerves or one solid nerve that can handle millions of individual signals?

Millions of individual nerves .... I don't think the human nervous system has developed the ability to carry duplex signals.
It branches down through the spine, like an upside-down tree, sending out branches into all four limbs and major organs, and other major body parts.

[MillCreek]

Think of the spinal cord as a fiber optic cable: lots of individual fibers inside of a casing.   In cases of spinal cord severance, you have to try to get the individual fibers to reconnect.  There is a ton of work going on across the world on this very issue, from microsurgical techniques, to 'spinal glue', to using medications to encourage regrowth/fusion of the nerves.  The other big question is how many of the spinal nerves have to successfully reconnect/fuse to have meaningful control and sensation over the body.  There is thought that the spinal cord may have lots of excess capacity and if you get 10-25% of the nerves to fuse, this may be a successful result.

[Marnoot]

I'd imagine once they do get some spinal nerve re-connection happening, that oodles of physical therapy will have to follow for the brain to learn the new mappings, since it's probably pretty much impossible to get Nerve 435324 to reconnect to the other end of Nerve 435324 instead of Nerve 895232, etc. Fortunately adult brain plasticity is much more a thing than medicine thought earlier in the 20th century!

That said is there any guarantee that Nerve A, which used to carry impulses to the left calf, can now successfully instead carry impulses to the right foot, etc.? I imagine they must have a good idea that the brain and nerves are capable of figuring things out if they're working to figure out how to get things connecting.

[Hawkmoon]

What's the problem? Aren't the wires nerves properly color-coded?

[Marnoot]

oh duh, nevermind, I was thinking about it wrong. If the bottom half of Nerve A connects to your left calf, it will still send impulses to your left calf, but when connected to the upper half of Nerve B, the brain will have to learn that B is no longer the wire to the right foot, but now is the wire to the left calf, thus solved by brain plasticity.

[Hawkmoon]

I think the sheer magnitude of relearning all the connections would be daunting. I use a chiropractor for back problems, and on the wall in one of the treatment rooms there's a diagram showing all the nerves from the various extremities up to the cerebral cortex. If they just allow the nerves to fuse at random, you would essentially have to relearn every single muscle control in the body. Not just "right hand," but

• right thumb extend
• right thumb contract
• index finger extend
• index finger contract
• middle finger extend
• middle finger contract
• ring finger extend
• ring finger contract
• pinkie extend
• pinkie contract
• wrist extend
• wrist contract
• wrist rotate
• ...

So let's say we want to learn how to extend the right thumb. We HOPE there's a functional nerve connection to that muscle. How do we find it if we have NO idea what nerve connected to it? Basically, the subject has to try every formerly-remembered muscle command until he finds the one that extends the right thumb -- maybe it's the one he remembers as turning the left foot outward. Now he has to train his brain to remember that that command now extends the right thumb rather than turning the left ankle.

And he has to repeat that for every single muscle he wants to control.

A long time ago I taught myself to wiggle my ears, and to raise one eyebrow. Each of those took weeks (or more likely months) of just standing in front of a mirror and watching for any infinitesimal hint of movement, and then learning to amplify that movement consciously. I know that dogs and cats can turn their ears independently, so I see no reason why I can't learn to wiggle ONE ear, rather than both together. But I haven't been able to isolate moving just one ear. The concept of retraining to move every part of the body is simply mind-boggling.

[K Frame]

If they actually start transplanting heads, will that be the end of the Order of the Headless Monks?

[KD5NRH]

I was half expecting it to be a handyman article on toilet replacement.m

[HeroHog]

Hawkmoon, my next door neighbor and I were (are still) drummers growing up and he could wiggle his ears. The cool thing was, he would do it while bobbing his head in time to the music where his ears appeared to stay perfectly still! Funniest thing I had ever seen!

[TommyGunn]

I think the sheer magnitude of relearning all the connections would be daunting. I use a chiropractor for back problems, and on the wall in one of the treatment rooms there's a diagram showing all the nerves from the various extremities up to the cerebral cortex. If they just allow the nerves to fuse at random, you would essentially have to relearn every single muscle control in the body. Not just "right hand," but

• right thumb extend
• right thumb contract
• index finger extend
• index finger contract
• middle finger extend
• middle finger contract
• ring finger extend
• ring finger contract
• pinkie extend
• pinkie contract
• wrist extend
• wrist contract
• wrist rotate
• ...

So let's say we want to learn how to extend the right thumb. We HOPE there's a functional nerve connection to that muscle. How do we find it if we have NO idea what nerve connected to it? Basically, the subject has to try every formerly-remembered muscle command until he finds the one that extends the right thumb -- maybe it's the one he remembers as turning the left foot outward. Now he has to train his brain to remember that that command now extends the right thumb rather than turning the left ankle.

And he has to repeat that for every single muscle he wants to control.

A long time ago I taught myself to wiggle my ears, and to raise one eyebrow. Each of those took weeks (or more likely months) of just standing in front of a mirror and watching for any infinitesimal hint of movement, and then learning to amplify that movement consciously. I know that dogs and cats can turn their ears independently, so I see no reason why I can't learn to wiggle ONE ear, rather than both together. But I haven't been able to isolate moving just one ear. The concept of retraining to move every part of the body is simply mind-boggling.

Well, if  THE SIX MILLION DOLLAR MAN  could do it, anyone should be able to.

[zahc]

It takes babies about a year or two. I would put that as an absolute best limit

[Marnoot]

It takes babies about a year or two. I would put that as an absolute best limit

I'd wager absolute is right. While adult brain plasticity is a thing it's not as plastic as an infant's. Also, an infant is basically learning those mappings more or less constantly while awake at various ages, constantly moving and figuring things out. As an adult, sanity would dictate you not spend that much time working on it.