[HN Gopher] Groundbreaking arm amputation surgery makes a 'phant...
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Groundbreaking arm amputation surgery makes a 'phantom' hand seem
real
Author : hhs
Score : 129 points
Date : 2021-09-18 14:55 UTC (8 hours ago)
(HTM) web link (www.statnews.com)
(TXT) w3m dump (www.statnews.com)
| tyingq wrote:
| This short video of a guy operating a motorized prosthetic foot
| is really interesting:
|
| https://videos-fms.jwpsrv.com/0_6146535c_0xe8e28ca538bc35a69...
|
| And this article does a better job of explaining the surgery:
| https://bionicsforeveryone.com/agonist-antagonist-myoneural-...
|
| I guess, in a nutshell, they attach a small amount of muscle to
| the nerve that controls something that's going to be cut off. And
| they anchor that muscle on both ends. So that contracting and
| relaxing it provides a real-world force feedback loop. Really
| clever.
| hanoz wrote:
| This reminds me of an experiment recounted in a great book
| _Phantoms in the Brain_ , which I always wanted to try.
|
| The subject sits with a model nose placed some distance in front
| of them on which someone taps and strokes in some non predictable
| fashion. At the same time the subject's own nose is touched in
| precisely the same pattern. Subjects apparently report an
| overwhelming sensation that the model nose, some meters in front
| of them, is thier own nose!
| golemotron wrote:
| With an article title like that, you have no idea what you are in
| for.
| amjaeger wrote:
| https://www.science.org/doi/abs/10.1126/scirobotics.aan2971
|
| This is one of the first papers describing the AMI surgery.
| cududa wrote:
| Caveat: not a neuroscientist, but have worked with many and been
| involved in MRI and fMRI imaging for investigating HCI concepts/
| products and marketing. As well, when I was younger had
| trigeminal neuralgia, considered the most painful disease
| (explained below), and became fascinated with neuroscience.
|
| The approach of closing the loop on agonist/ antagonist feedback
| in muscle fibers makes an enormous amount of sense and is
| brilliant.
|
| Without the two "outbound requests" happening in a closed system
| the brain is left to approximate the difference between the
| slight signal shift. Even nanosecond differences in "send/
| receive" requests would be registered as pain.
|
| I had a neurological condition called trigeminal neuralgia where
| the myelin wears down between the positive/ negative nerve
| bundles in the trigeminal nerve and occasionally touch.
|
| The reason it's considered the most painful affliction is the
| trigeminal nerve is where your whole body's pain, pressure, and
| heat sensory nerves converge. So when the +/- touch, every fiber
| of you feels like it's being stabbed, burned, and crushed at the
| same time. About 90% of folks with it have have one occlusion in
| the myelin and will feel excruciating pain in a localized are. I
| had 9 full occlusions and 20+ partial. So lucky me, I got to
| experience it through my whole body.
|
| Basically, when the +/- nerves touch, no part of your body is
| receiving/ returning the expected "latency" for pain, pressure,
| or heat, and perceives the differences of return times as nerves
| (including those in agonist/ antagonist muscle) being split/
| damaged, thus a pain response.
|
| Totally makes sense that closing the proper agonist/ antagonist
| fibers to create a proper feedback loop could eliminate the
| unexpected diff on signal requests that trigger phantom pain.
|
| EDIT: Just to give yourself some real world examples.. Do
| something like build a fence with your friends, all day. One
| person operates the saw, one the hammer, so on and so fourth.
|
| At the end of the day using the same tool in repetition, hold
| your tool, everyone applies blindfolds, then have an
| "experimenter" touch the subjects forearm at different points.
| They'll experience the touch at a different point than if they
| weren't holding the tool.
|
| When you use something for a long time you integrate it into your
| "body schema" - basically your brains map of yourself.
|
| My absolute favorite example of body schema extension are
| experienced crane operators in docks. They can see a container on
| a ship, need to place it on a massive pile they've been building
| all day, and can no longer see in their line of vision where
| they'll place it. But they can still do it without being able to
| see where they're dropping it.
|
| All that's to say - your brain builds better and better models of
| it's container (body) and environment by developing more and more
| precise models of input/ output diff expectations and essentially
| a "path prediction" algorithm.
|
| When the actual data is outside of parameter/ estimates get out
| of whack, we experience things like pain where there's no harm.
| But in an amputee, agonist/ antagonist muscle fibers are no
| longer on the same circuit. The body adapts, and sends two
| different "ping" requests to both channels.
|
| So I guess to simplify all that: When theres a micron of
| difference in length in key paired muscle fibers (as is common in
| amputations, injury, etc), the brain sends two signals, diffs the
| return times and if they're out of wack with past lived
| experience you get pain.
|
| While the amputee still doesn't have the "normal" limb length the
| body is expecting, closing the loop provides the expected send/
| receive timing variance.
| stavros wrote:
| How did you cure your condition?
| cududa wrote:
| Was an experimental one, and actually need to get part of it
| repaired soon which I'm not looking forward to.
|
| But basically, the trigeminal nerve bundle comes up from your
| neck through your right jawbone, heads up around your mouth
| and cheek bone to your ear and brain stem.
|
| Mine involved having a molar removed (I need a new false one
| - this one got me 16 years but the new ones are billed as
| lasting a life time) with laparoscopic surgery to move up
| into the cavity, and insert small bits of poly-fibers between
| the offending occlusions in the myelin. If they manage to get
| all of the offending parts, the myelin degradation stops -
| for most people. Some with atypical cases or a case brought
| on by multiple sclerosis there's no cure. As it is, there's
| no treatment for symptoms but my god for those without a
| solution, assisted suicide is truly the only humane thing.
| Buttons840 wrote:
| > Outside of a brain scanner, the restoration of proprioception
| can in some ways give patients the feeling of having a real foot.
| One AMI amputee was hiking recently while wearing a standard
| prosthesis and stepped into a creek. He later described having
| the sensation of water flowing over his prosthetic foot even
| though it had no way to perceive that. "He trusted or embodied
| his prosthesis more than someone who doesn't have this phantom
| sensation," said Carty.
|
| I read about an experiment where people were shown various black
| and white drawings over random grayish backgrounds. They then had
| to estimate the hue of the grayish background - which was
| tricking because it only has slight amount of red, or blue, etc).
| The results clearly shows that the black sketch which was
| overlayed on the gray background skewered peoples perceptions of
| the color of the background. People could not simply observe the
| color of the background without their other knowledge skewing
| their perception.
|
| Yet another example that we don't really get a "raw feed" from
| out senses. What we perceive has already gone through a lot of
| "post-processing" by our brain.
| agumonkey wrote:
| do you know research about proprioception instability ?
| krisoft wrote:
| Absolutely. This is one of the reason why it is really hard to
| explain to laymans why robotic perception is hard. The
| conversation usually goes: why can't you just make it do
| "obviously good action" when "condition" happens? And since
| "condition" is something they can just see it is hard to
| convince them the robot doesn't have access to it in a clear
| and unambigous maner.
| GravitasFailure wrote:
| Rodney Brooks talked about building an ant robot trying to
| mimic the real thing. He said a real ant has hundreds of
| thousands to millions of sensors while the robot his team
| built had 150, and they only barely could handle that. The
| data living things gather from their environment and the
| processing used on it is absolutely mind boggling.
| alisonkisk wrote:
| A phone camera has millions of sensors...
| wyldfire wrote:
| > Yet another example that we don't really get a "raw feed"
| from out senses. What we perceive has already gone through a
| lot of "post-processing" by our brain.
|
| Looking forward to HDR and Image Stablization in Humanity 2.0
| coming in 102022.
| adwn wrote:
| > in 102022
|
| Is this refering to the holocene calendar? [1] If yes, then I
| think you meant "12022" - unless you're really pessimistic
| about the timeline...
|
| [1] https://en.wikipedia.org/wiki/Holocene_calendar
| GordonS wrote:
| > I read about an experiment where people were shown various
| black and white drawings over random grayish backgrounds. They
| then had to estimate the hue of the grayish background - which
| was tricking because it only has slight amount of red, or blue,
| etc)
|
| I'm colour blind, and if a picture is in black and white, I
| can't always tell.
|
| A long while back our CRT TV broke, and started displaying
| everything without colour - I had no idea until my wife pointed
| it out! It's like my mind just makes up what it doesn't see.
|
| Another example that I always use is grass: if you showed me a
| cropped image of grass and I didn't know it was grass, I'll
| tell you "I don't know what colour it is, but I think it's
| either red, brown or green". But if you point to some grass,
| I'll always say "it's green!".
| Timpy wrote:
| I'm curious about your experience, do you actually feel like
| you are seeing green, or do you just know that green is the
| correct answer?
|
| We had a bunch of different candies on the table at game
| night and I gave my friend some M&Ms, he thought they came
| from a bag of mint flavored M&Ms. He said, "wow I never tried
| these before, they really taste like mint." We all did a
| double take, he definitely did not eat mint M&Ms, I don't
| really remember if we even had mint M&Ms at the table. I
| believe him when he says he says he tasted mint though, like
| his brain placeboed the mint into place.
| GordonS wrote:
| With the TV, I actually feel like I'm seeing colours, even
| if I don't know exactly what they are.
|
| With the grass example, I'm actually not entirely sure! I
| mean, I obviously know that green is the correct answer,
| but that knowledge kind of makes me feel like I'm seeing
| green.
|
| But colour blindness is kind of weird, because for any
| given thing/colour it's never just "I don't know" - I can
| narrow it down to a few options, and _usually_ one of them
| is the correct one; like for a desaturated green, I might
| think it 's grey, green or pink.
| Deestan wrote:
| I wonder if it is related to the gray/red strawberry
| effect https://www.illusionsindex.org/i/grey-strawberries
| jvanderbot wrote:
| To control a large body with ample signal propegation delays,
| the brain probably predicts a lot (Werner's "Cybernetics" --
| outdated but not wrong). Big bodies have bigger brains
| partially for this reason.
| einpoklum wrote:
| This almost sounds like it's about the NVIDIA's trouble with the
| ARM deal.
| ouid wrote:
| I have always felt that the reason that we can't run in dreams is
| because the sensation of running is not something that we
| remember well enough to model. We can verify that sensation, but
| not recreate it. An enormous amount of computation is offloaded
| to the world.
| alisonkisk wrote:
| More likely it's because your body is semi paralyzed in sleep,
| so your dreaming brain notices that your legs aren't moving.
| simion314 wrote:
| My assumption why in my dreams running feels hard like your
| legs are made of led is because of the paralysis we suffer when
| dreaming. Like I want to run but some subconscious things is
| signaling that your legs are blocked so I get this sensation.(I
| had similar experience with attempting to open my eyes n dreams
| and feeling that they are glued or hard to open/keep them open)
| leksak wrote:
| I run in dreams. Good and bad. One of my favourite dreams start
| with me running, and it crescendos towards a feeling of
| effortlessness. The ease of my stride becomes complete, rarely
| and barely do I have to touch the ground to continue propelling
| myself forward. The few times that I do have to make ground
| contact it is as if my forefoot merely licks the ground and I
| experience something akin to almost-flight.
|
| It is not as if I'm weightless as much as having an
| unbelievably elastic Achilles tendon that allows me to bound
| ahead, completely and utterly free. With nothing to impede me.
|
| In nightmares, if I have to run, I'm not as swift.
| YeGoblynQueenne wrote:
| Interesting. When I have one of those dreams I start running
| on all fours. Which is weird because I could never run like
| that in real life. Although I tried to repeat the movement
| when I was in the sea, once, and it kiind of worked, in that
| I could propel myself forward, except I had to be underwater.
|
| Now that I think of it, I've never had a dream where I can't
| _swim_ and I dream of swimming very often.
| leksak wrote:
| Maybe you could learn. Animal locomotion is pretty big on
| YouTube.
| ddlutz wrote:
| Interesting I run in my dreams quite often. I didn't know some
| people couldn't. However in my dreams I can't really punch, all
| punches feel like they have no "weight" to them if that makes
| sense.
| DoreenMichele wrote:
| _Herr said the AMI patients have felt less pain in their residual
| limbs, and their limbs don't atrophy, as is typical after a
| standard amputation, resulting in a poor fit and pain when using
| a prosthesis._
|
| So this is a really significant step forward with immediate
| important benefits. "Use it or lose it." Muscle function is
| preserved so the stump isn't simply rotting. It still has muscle
| function which is essential to preserving vitality.
|
| Coincidentally, I happened to trip across this House MD clip
| about phantom pain recently:
| https://www.youtube.com/watch?v=aIMa6G6EmC8
|
| It reminded me of seeing this on HN:
|
| _The Mirror Man: Treating Phantom Limb Pain With a Simple
| Technology_
|
| https://news.ycombinator.com/item?id=8157932
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