
Prosthetic Limb Restores a Sense of Body Position - oblib
https://www.scientificamerican.com/article/prosthetic-limb-restores-a-sense-of-body-position/
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whymauri
Very excited to see this posted here. I was an undergraduate research
assistant at this lab working on related projects on this team. It's amazing
what the AMI (regenerative antagonist-agonist myoneural interface) can do and
I assisted with a follow-up project to expand the use-cases of this surgical
architecture (currently under review). Solving the proprioception problem is
big news as even people like our PI, Hugh, who have had prosthetics for
decades have to mentally calculate movements that are natural for un-injured
people. It's incredibly tiring and I think we will be seeing a drastic
improvement in the quality-of-life of people with prosthetic devices.

A year ago, I even met someone who had a foot but due to chronic pain wanted
it amputated and was exploring the AMI. That is, they would prefer a bionic
solution with the sort of neuro-integration the AMI can offer over an actual
foot!

I think that hits the core of our group's vision, which is not just
rehabilitation but recovery beyond standard human capacities. This is inspired
by how Hugh was able to rock-climb better post-amputation than before, a
concept he often calls 'Human 2.0'

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kevinmchugh
This is fascinating. I recently read up on phantom limb syndrome and found one
of the most horrifying ideas I've ever seen. Wikipedia summarizes:

> Until recently, the dominant hypothesis for the cause of phantom limbs was
> irritation in the severed nerve endings [...] These nerve endings can become
> inflamed, and were thought to send anomalous signals to the brain [...]
> Treatments based on this hypothesis were generally failures. In extreme
> cases, surgeons would perform a second amputation, shortening the stump,
> with the hope of removing the inflamed nerve endings and causing temporary
> relief from the phantom pain. But instead, the patients' phantom pains
> increased, and many were left with the sensation of both the original
> phantom limb, as well as a new phantom stump, with a pain all its own.[0]

It will be interesting to see if this treatment can stop phantom limb pain.
One hypothesis is that pain is the result of the brain modifying to accomodate
a lack of signals from the severed limb. If this treatment prevents pain, that
would be a good indicator for that hypothesis.

[0]
[https://en.wikipedia.org/wiki/Phantom_limb#Mechanism](https://en.wikipedia.org/wiki/Phantom_limb#Mechanism)

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oblib
I worked with amputees for around 14 years back in the 70-80s and was kind of
shocked when I first heard about phantom limb syndrome. I'd just never
imagined such a thing before then.

It's not just "pain", but really annoying "itches" and other sensations too.
People with above the knee amputations would tell me their "foot was itching".

One of the biggest issues back that was weight gain/loss. Just a few pounds
would change how the the limb fit and since they were held in place in large
part via suction (vacuum) when it didn't fit right it could be somewhat
painful and at the least very annoying when they got loose or too tight. I
spent many hours helping amputees apply and sand "bondo" inside their "leg"
where it attached to their "stump" to get them to fit comfortably.

It's been close to 30 years now since I've worked on those and I've not kept
up on what's changed. I imagine there have been improvements. I sure hope so.

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skybrian
It looks like this might be the paper:

[https://www.media.mit.edu/publications/proprioception-
from-a...](https://www.media.mit.edu/publications/proprioception-from-a-
neurally-controlled-lower-extremity-prosthesis/)

