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Comment by grenoire | Hacker News Reader

How exactly does a nerve transfer work? I always imagined that certain control and reception signals would have their dedicated nerve connections, such that rewiring from a transplanted nerve would jumble up the wiring and give 'incorrect' results.

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Even if the result is incorrect at first, the brain is adaptable and will simply remap to correct the bad wiring.

There are videos on youtube of people who put on googles that invert the view of the world upside down. After a few weeks/months of adaption, they can live in that condition as normal.

I wonder how similar that is to the effect of the "backwards bike" shown in "Smarter every day": https://www.youtube.com/watch?v=MFzDaBzBlL0

It seems like there's a very deep idea of how a bike should work and instead of learning the new behaviour bit by bit the new idea just "clicks" at some point. I've heard people with up/down flipped goggles also say it's quite sudden change. I'm curious if it's similar for reconnected nerves?

That instant clicking is exactly how it feels (for me at least) learning to play music.

I'll practice the same thing over and over, for an hour maybe. It takes so much brain power, it feels weird, sometimes it's good, mostly it's not.

Then stop, go to sleep, come back tomorrow, and 25% of the time it'll just be there with no thought or effort required whatsoever.

This! This is so hard to explain to others who are trying to get into learning a new instrument. The most frustrating part is that rarely will I see the results of my practice on the day of practice, especially for tricky sections, which can make the sessions feel kinda useless. Then I'll come back a day or two later and suddenly my hands know what to do. "Okay let's start at marker B and... oh, okay!"

The hard part then, of course, is letting them get on with it, and only correcting actual mistakes. If I try to analyze what they're doing the whole thing kinda falls apart. That moment when I can switch from focusing on notes and rhythm to ... more like conducting from afar is the moment when a piece really starts to feel playable. But getting there is always a challenge, and pushing through that challenge is the toughest part.

It's really kinda fun to go back to a piece that I used to know really well and dust off the cobwebs. "Now how did this section go? .. I have no idea what chord that was. Hrm... maybe if I start from a phrase earlier and play into it... oh... oh that's how it went!"

I wonder if babies work this way? i.e.The brain doesn't know which connection is which until the it performs thousands/millions of movement tests to see what moves what? Then over time it solidifies the muscle memory?

A lot of stuff is preprogrammed or developed before birth. Most of the senses work and the motor system atleast knows what nerves do what (though coordination is 0).

Other animals come out far more developed when born and have a functional motoric system and brain, our species doesn't do that mainly because it would be difficult to have the baby fit through.

I wonder if they learn some of it still in the womb. After all, most mothers say they can feel "kicking" sometimes. That might actually be the fetus learning how to extend its limbs

As someone who has been pregnant and had a baby, it's much more than feeling kicking "sometimes." It's all sorts of movements, and you can even tell which part of the body is where (depending on the position of the baby). They'll even do somersaults in there before they get too big.

The movement is frequent enough that a measure of health for the baby starting about 3/4 of the way through the pregnancy is to have the mother count movements until she reaches 10, which should take between 30 minutes and 2 hours.

I seem to have awareness that people have redirected the auditory and visual cortexes as an experiment and found that sight and hearing were recovered eventually?

Unfortunately I can't find a source to verify this so hoping someone with better knowledge could confirm that this is just how plastic the brain can be?

There also an experiment where they remove the rods and cones of mice and replace them with light sensitive proteins from some bacteria, and the mice achieve some level of sight after a short period of time. Neuroplasticity is crazy.

Edit: algae not bacteria, here’s a link I found https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4817926/

You may be thinking of this experiment on ferrets: https://www.ncbi.nlm.nih.gov/m/pubmed/1527604/

Yes this is along the right lines - thank you!

I kind of doubt that you can do that because blind people still use their visual cortex when they make out the shape of objects by tough, or when they navigate the world, so I would assume the visual cortex is a specialized "hardware".

It strikes me that it's less specialized to processing sensory input from light and more specialized to constructing a model of where things can be expected to be in relation to where the body is. So it's like a proprioceptory map.

It's interesting because I can look around my bathroom in the light, turn the light off, then reach for and grasp EG a toothbrush from memory on the first try without feeling around. It's like the images are a map of where things are and that map doesn't require the sensory images once it's constructed, nor does it require visual stimulation to construct.

A lot of stuff in biology is "stick it in sees if it works" kind of stuff anyway.

Who knows what will happen in 20 years.

that's how most things reproduce ><

You made my day.

The physical therapy to help the brain remap the wiring following nerve transfers is pretty intensive. It's not something that happens quickly or easily. But even limited function after a long therapy period is much, much preferable to no function at all for these patients.

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