Prosthetic Hand Capable of Delivering Texture Sensations

Zothecula writes: A new prosthetic system allows amputees to feel familiar sensations and also, somewhat unexpectedly, reduces their phantom pain. Researchers at Case Western Reserve University and the Louis Stokes Cleveland Veterans Affairs Medical Center developed the system to reactivate areas of the brain that produce the sense of touch, but recipients of prosthetic hands reported their phantom pain subsiding almost completely after being hooked up to the system.

Comments

Not a medical professional, but:

[kheldan]

Seems to me that when some area of your body doesn't get much or any stimulation for long periods of time, it gets more sensitive. If you lose a limb the associated sensory nerves get zero stimulation, as well as the associated area of the brain. Wouldn't those nerves and that part of your brain 'turn up the gain' and experience more 'noise' in the absence of 'signal' (hence 'phantom pain')? Then you attach something that provides a 'signal' again; 'gain' goes down, S/N ratio goes up?

Re:Not a medical professional, but:

[gstoddart]

Seems to me that when some area of your body doesn't get much or any stimulation for long periods of time, it gets more sensitive

Must ... not ... make ... penis ... joke ...

Re:Not a medical professional, but:

[BringsApples]

Yeah, that's exactly what they say happens. I don't know from experience, but I did see a really good documentary on a doctor that discovered that by simply tricking the brain, causing the phantom pain to go away. The patient that he was working with lost their hand and about 3/4 of the arm to the elbow. The patient reported that it felt as if his hand was squeezing harder and harder (as you point out, 'turning up the gain' and experience more 'noise'). So the doctor decided to try out setting up a mirror-box whereby the patient put his good arm and hand in, looked at the mirror, and would see what appeared to be his other hand (reflection) and by simply opening his other hand, the mind was tricked into seeing the missing hand as opening, causing the pain to stop completely immediately. The patient had to do this every now and then, to continue pain relief. But what an insightful doctor!

Re:Not a medical professional, but:

[Frosty Piss]

Prosthetic Hand Capable of Delivering Texture Sensations

...to my penis.

Re:Not a medical professional, but:

[gstoddart]

While this may just be triggering a fight of flight response, it interesting the note that the irrational portion of the brain seems to override the rational part (the one that 'knows' your hand is safe). After reading BringsApples post it struck me that these two cases may be opposite sides of the same coin.

Well, here I'd substitute rational/irrational with 'conscious' and 'primitive'.

You as a human know you are missing your hand (or in the case of your example that your hand isn't really going to get hit). However, the really primitive bits are still in there going "Hand, this is mission control, do you copy? Status report please." (Or in the case of your hand being there but not getting hit, "Alert! Hand, take evasive action" because its job is to do that kind of thing.)

And this is probably well below what can be your conscious brain. So, no matter what your conscious brain knows and is aware of, the really primitive parts are handling other stuff.

From the exceedingly little I recall from psych class (yes, only one, a long time ago) this is probably the structures of the brain that we share with alligators and pretty much everything else.

I'm inclined to think kheldan probably nailed it (in very broad strokes), the brain is actively looking for a response from the limb and not getting anything. So maybe what this does is fool the primitive part of your brain into going "OK, status report from hand occurred, we can dial back the urgency". And I'm sure that part of your brain can't be overridden with "I know my hand won't get hit because this is just an illusion", so it responds as if it's happening.

No matter what you know rationally, the really basic structures of your brain have their job, and still keep trying to do it.

Though, this should be in no way be considered to be an accurate description of the physical stuff, just a high-level hand-waving thing.

I used to know a quadriplegic who used to occasionally get an itchy foot ... despite the fact that he hadn't had any sensation below his shoulders for 25+ years. Scratching didn't alleviate anything, because it wasn't really itchy. At least, not in the way we tend to think of it. I'm sure the sensation was just as real.

Re:Not a medical professional, but:

[EnempE]

Very interesting. Not quite the same as the article because the subject in this case is blindfolded and its a referred sensation.
Nonetheless I didn't know about this and was happy for the reference.
I think the /. appropriate content is at the links below

Synaethesia in phantom limbs induced with mirrors (1996)
V.S. Ramachandran & D Rogers-Ramachandran
http://chip.ucsd.edu/pdf/Synst...

Phantoms Limbs and Neural Plasticity
V.S. Ramachandran & D Rogers-Ramachandran (2000)
http://www.neurosciences.us/co...

Nerve mapping?

[DoofusOfDeath]

Can anyone here explain to me the issue if/how we can map nerves correctly?

For example: suppose someone's finger gets cut off, and then surgeons manage to reattach it.

I assume that since there are many distinct sensory nerve endings on a finger, each of those must be carried along a distinct electrical pathway up to the brain.

When a surgeon reattaches a finger, does he/she somehow get all of those hundreds(?) of connections to be lined up properly so that the mapping is the same as it was before the accident? If so, how? If not, what happens?

Re:Nerve mapping?

[gstoddart]

I think that if you re-attach soon enough, the nerves end up re-mapping to the neurons as your brain sorts out what's what.

Over time, your brain figures out that this particular one doesn't quite match what it used to, and then maps to the one which is there now.

I suspect during the initial period until the nerves sort themselves out, you have really mismatched/clumsy sensation, but over time as the brain and neurons sort everything out it gets better.

Of course, I'll freely admit I have no real understanding of the process, and that this is pulled out of nothing but speculation and things I think I remember hearing in terms of explanation.

Well duh

[Daetrin]

"A new prosthetic system allows amputees to feel familiar sensations and also, somewhat unexpectedly, reduces their phantom pain."

This seems like one of those things that people might very reasonably not think of ahead of time but which seems blindingly obvious in retrospect. It would probably be expected that if you managed to reattach a severed limb that there wouldn't be any phantom pain afterward. ("Real" pain during the healing process yes, and perhaps lingering aches as one might have with any injury, but not phantom pain.) You'd also expect the same to hold true if you managed to grow a new arm and attach it properly.

But a simple prosthetic isn't enough to prevent or cure phantom pain. So one would expect that at _some_ point in the process between no nerve connections with a peg leg (or equivalent) and full connection with a regrown/reattached limb that the phantom pain would disappear. I guess they just encountered that point earlier than they might have expected.

In hindsight

[blueshift_1]

This is one of those obvious things that makes more sense afterward. Clearly the nerves have had years of constant input and you just take that away... it make sense that system would create false/phantom input as an assumption that it should be receiving some sort of signal. By increasing the amount of input, it creates a more normal state for the body... the more you knooooow.