Scientists create illusion of having 3 arms

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The Reaper
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Scientists create illusion of having 3 arms

Postby The Reaper » Wed Feb 23, 2011 11:39 pm UTC

http://www.physorg.com/news/2011-02-sci ... -arms.html
How we experience our own bodies is a classical question in psychology and neuroscience. It has long been believed that our body image is limited by our innate body plan – in other words that we cannot experience having more than one head, two arms and two legs. However, brain scientists at the Swedish medical university Karolinska Institutet have now shown that it is possible to make healthy volunteers experience having three arms at the same time.

In a novel paper published in the online scientific journal PLoS ONE they describe how it is possible to create an illusion of owning three arms, under controlled conditions in a laboratory. The experiment involves the participant sitting at a table and having a realistic prosthetic arm placed next to their right arm. The subject then sees her two real arms and the extra prosthetic arm, made out of rubber. To produce the feeling of owning the rubber arm, the scientist touches the subject's right hand and the rubber hand with two small brushes at corresponding location – synchronizing the strokes as perfectly as possible.

"What happens then is that a conflict arises in the brain concerning which of the right hands belongs to the participant's body", says Arvid Guterstam, one of the scientists behind the study. "What one could expect is that only one of the hands is experienced as one's own, presumably the real arm. But what we found, surprisingly, is that the brain solves this conflict by accepting both right hands as part of the body image, and the subjects experience having an extra third arm."

The study consists of a series of experiments; in total 154 healthy volunteers were tested.

To prove that the prosthetic arm was truly experienced as a third arm, the scientist 'threatened' either the prosthetic hand or the real hand with a kitchen knife, and measuring the degree of sweating of the palm as a physiological response to this provocation. The results demonstrated that the subjects had the same stress response when the prosthetic hand was threatened as when the real hand was, but only during the periods when they experienced the third arm illusion. For instance, there was no stress reaction when the prosthetic right arm was replaced with a left arm or a prosthetic foot.

The results of the study may benefit patients by creating new applications in prosthetics research.

"It may be possible in the future to offer a stroke patient, who has become paralysed on one side of the body, a prosthetic arm that can be used and experienced as his own, while the paralysed arm remains within the patient's body image", says Henrik Ehrsson, who has led the study at the Department of Neuroscience. "It is also conceivable that people with demanding work situations could benefit of an extra arm, such as firemen during rescue operations, or paramedics in the field".

More information: Guterstam A, Petkova VI, Ehrsson HH (2011) The Illusion of Owning a Third Arm. PLoS ONE 6(2): e17208. doi:10.1371/journal.pone.0017208
Future in cybernetic enhancements, amiright?

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Re: Scientists create illusion of having 3 arms

Postby WaterToFire » Thu Feb 24, 2011 1:23 am UTC

HELL YES. This cures so many of science-fiction nerd insecurities... The future's looking bright and full of many interesting appendages.

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Re: Scientists create illusion of having 3 arms

Postby Thesh » Thu Feb 24, 2011 1:26 am UTC

Now if I can only have a robotic fourth leg.
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Re: Scientists create illusion of having 3 arms

Postby mmmcannibalism » Thu Feb 24, 2011 1:30 am UTC

WaterToFire wrote:HELL YES. This cures so many of science-fiction nerd insecurities... The future's looking bright and full of many interesting appendages.


Indeed.
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Re: Scientists create illusion of having 3 arms

Postby Thesh » Thu Feb 24, 2011 1:31 am UTC

On another note, I wonder if this means that brain transplants would be possible if we can reconnect the nerves?
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Re: Scientists create illusion of having 3 arms

Postby The Reaper » Thu Feb 24, 2011 1:32 am UTC

Thesh wrote:On another note, I wonder if this means that brain transplants would be possible if we can reconnect the nerves?

You'd probably need to take a metric ton of LSD to get that one working right...

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Re: Scientists create illusion of having 3 arms

Postby Internetmeme » Thu Feb 24, 2011 1:41 am UTC

Thesh wrote:Now if I can only have a robotic fox tail.

Fix'd that for me.


Actually, I wonder if that would be possible, to repeat this experiment for something like that. There isn't any analogue in the body for one, though.
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Re: Scientists create illusion of having 3 arms

Postby Thesh » Thu Feb 24, 2011 1:43 am UTC

I think it would be possible, given this:

http://www.youtube.com/watch?v=TJJPbpHoPWo
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Re: Scientists create illusion of having 3 arms

Postby Internetmeme » Thu Feb 24, 2011 2:02 am UTC

Thesh wrote:I think it would be possible, given this:

http://www.youtube.com/watch?v=TJJPbpHoPWo


I now know what I'm going to spend my money on when I get a doctorate in pharmacy.
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Re: Scientists create illusion of having 3 arms

Postby Arancaytar » Thu Feb 24, 2011 2:05 am UTC

Pretty cool. A really great breakthrough would be if the brain not only experienced both arms as its own, but could control them separately (with an implant, like with that monkey). Actually moving several arms with individual motor control would be all kinds of awesome. Though I guess training the brain to do that would be really difficult.
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Re: Scientists create illusion of having 3 arms

Postby Triangle_Man » Thu Feb 24, 2011 4:54 am UTC

So if they can trick the brain into thinking it has a non-existent third arm, than they can get the brain to think of an artificial arm as it's own?

Sweet.
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Re: Scientists create illusion of having 3 arms

Postby Inny Binny » Thu Feb 24, 2011 5:34 am UTC

Ha, this is awesome.

I would think this sort of thing would be possible while consciously dreaming? i.e. the feeling of having three arms, a tail etc.

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Re: Scientists create illusion of having 3 arms

Postby Vellyr » Thu Feb 24, 2011 7:10 am UTC

Inny Binny wrote:Ha, this is awesome.

I would think this sort of thing would be possible while consciously dreaming? i.e. the feeling of having three arms, a tail etc.


Yeah, I've done it before. I'll let you guess which appendage.

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Re: Scientists create illusion of having 3 arms

Postby Angua » Thu Feb 24, 2011 7:55 am UTC

Triangle_Man wrote:So if they can trick the brain into thinking it has a non-existent third arm, than they can get the brain to think of an artificial arm as it's own?

Sweet.
They could already do this - the cool thing about this one is that you think you have 3 arms at once (where as before the covered the second arm so you couldn't see it, then did the whole stroking thing to make you accept the prosthetic one).
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Re: Scientists create illusion of having 3 arms

Postby Triangle_Man » Thu Feb 24, 2011 8:47 am UTC

Angua wrote:
Triangle_Man wrote:So if they can trick the brain into thinking it has a non-existent third arm, than they can get the brain to think of an artificial arm as it's own?

Sweet.
They could already do this - the cool thing about this one is that you think you have 3 arms at once (where as before the covered the second arm so you couldn't see it, then did the whole stroking thing to make you accept the prosthetic one).


I wonder what it would feel like to have a third arm (or at least think you had a third arm)?

But if I am to understand it, they basically took a process that they already knew how to do and improved upon it, right?
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Re: Scientists create illusion of having 3 arms

Postby Technical Ben » Thu Feb 24, 2011 9:00 am UTC

I've got two words. GIANT ROBOTS.
I've already envisioned a 8 legged/armed mecha which would be controlled by brain waves. You would pilot it by moving your "imaginary" arms. A bit like a robotic octopus. The limit would be on how well you adapt. In my fiction it would cause some mental instability to those who try it, so most would be automated.
Good to see there is scientific evidence to back up the idea.

(My old design for a modular robot that you can add arms/legs to http://techy-ben.deviantart.com/gallery ... 01#/dpekwh)
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Re: Scientists create illusion of having 3 arms

Postby Triangle_Man » Thu Feb 24, 2011 9:03 am UTC

Technical Ben wrote:I've got two words. GIANT ROBOTS.
I've already envisioned a 8 legged/armed mecha which would be controlled by brain waves. You would pilot it by moving your "imaginary" arms. A bit like a robotic octopus. The limit would be on how well you adapt. In my fiction it would cause some mental instability to those who try it, so most would be automated.
Good to see there is scientific evidence to back up the idea.

(My old design for a modular robot that you can add arms/legs to http://techy-ben.deviantart.com/gallery ... 01#/dpekwh)


You just around 1000 Internets for coming up with this idea.

What else could you do with imaginary arms?
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Re: Scientists create illusion of having 3 arms

Postby Technical Ben » Thu Feb 24, 2011 9:14 am UTC

A DJ with 4 turn tables... Well, I know you can do it with a computer program. But it would look way cooler to have a DJ with 4 arms. ;)
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Re: Scientists create illusion of having 3 arms

Postby Aikanaro » Thu Feb 24, 2011 12:30 pm UTC

All you folks talking about an extra arm or leg are thinking too small. I've got two words for you: DOC OCK :D
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Re: Scientists create illusion of having 3 arms

Postby Telchar » Thu Feb 24, 2011 3:06 pm UTC

Keep in mind the experience only deals with sensory awareness. The brain can recognize, with difficulty, that it has 3 arms. That doesn't mean it has spacial or motor awareness or that those wouldn't be terribly uncoordinated.

I'm not aware of a way to test 3rd limb motor coordination atm but I assume it would be ballistic movement only for quite some time.
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Re: Scientists create illusion of having 3 arms

Postby Angua » Thu Feb 24, 2011 3:42 pm UTC

Triangle_Man wrote:
Angua wrote:
Triangle_Man wrote:So if they can trick the brain into thinking it has a non-existent third arm, than they can get the brain to think of an artificial arm as it's own?

Sweet.
They could already do this - the cool thing about this one is that you think you have 3 arms at once (where as before the covered the second arm so you couldn't see it, then did the whole stroking thing to make you accept the prosthetic one).


I wonder what it would feel like to have a third arm (or at least think you had a third arm)?

But if I am to understand it, they basically took a process that they already knew how to do and improved upon it, right?
Yeah - you can find youtube videos of people 'adopting' rubber arms and then someone smashing it with a hammer and watching them jump (unfortunately I don't have the time to find it, and can't remember what to search for). This is only new because it is 3 at once, and so means that you could possibly get a prosthetic to work without first cutting off the paralysed arm, but as Telchar pointed out, just because this is sensory perception doesn't mean that it will work mechanically (at least not yet).
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Re: Scientists create illusion of having 3 arms

Postby Technical Ben » Thu Feb 24, 2011 4:38 pm UTC

Telchar wrote:Keep in mind the experience only deals with sensory awareness. The brain can recognize, with difficulty, that it has 3 arms. That doesn't mean it has spacial or motor awareness or that those wouldn't be terribly uncoordinated.

I'm not aware of a way to test 3rd limb motor coordination atm but I assume it would be ballistic movement only for quite some time.

At a complete guess, with the plasticity of the brain, I think it could do anything when it comes to "extra" limbs or sensory input.
Proof of this comes in the experiments done with a compass sensor wired up to a scientists body. He could use it for navigation while blindfolded. Started to become natural after a month or two.
Then you have machine workers and pilots. They work cranes and planes just like it's part of their body. As in, they want it to go somewhere, and the body remembers the movements involved to achieve it.
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Re: Scientists create illusion of having 3 arms

Postby Cleverbeans » Thu Feb 24, 2011 4:41 pm UTC

Somehow I suspect the first practical application of this discovery will come to us from the makers of Viagra...
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Re: Scientists create illusion of having 3 arms

Postby gmalivuk » Thu Feb 24, 2011 6:03 pm UTC

Technical Ben wrote:At a complete guess, with the plasticity of the brain, I think it could do anything when it comes to "extra" limbs or sensory input.
Except, brain plasticity doesn't mean the brain is completely plastic. There are still limits on what it can do. (For example, your "it could do anything" claim would logically have to apply to 100 extra arms the same as just one extra. But do you really believe your brain could handle sensory input from 50 times more arms than it deals with currently?)
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Re: Scientists create illusion of having 3 arms

Postby Telchar » Thu Feb 24, 2011 6:46 pm UTC

One of the peculiarities of motor function would be positioning of the 3rd appendage. Your brain received input for spacial awareness from spindal organs but having hands on the opposite sides of the body makes it hard for them to accidently interfere with what the other is doing. Having one in the middle of your chest, in addition to proccesing seperate information for another hand that could bleed into the others, also adds an element of coordination.

I mean, it's cool. It's just this is more complex than I think people realize. What they did is similar to a psychosomatic response to visual stimuli and has been documented before for 1 limbed patients. Getting a working 3rd limb is something much more than tricking your brain via visual input and while very interesting is really just that.
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Re: Scientists create illusion of having 3 arms

Postby Technical Ben » Fri Feb 25, 2011 12:00 am UTC

gmalivuk wrote:
Technical Ben wrote:At a complete guess, with the plasticity of the brain, I think it could do anything when it comes to "extra" limbs or sensory input.
Except, brain plasticity doesn't mean the brain is completely plastic. There are still limits on what it can do. (For example, your "it could do anything" claim would logically have to apply to 100 extra arms the same as just one extra. But do you really believe your brain could handle sensory input from 50 times more arms than it deals with currently?)

OK. I'll remember not to use any over the top remarks ever. Oops. Did I say ever? I meant "almost anything".
I promise I will do my best to not overly... oh I'm crap at this anyhow. I meant "it could do quite a lot of things. We have an [almost] unlimited imagination. Why not try it."

So, infinite recursion arms anyone?

[edit]
With the likes of thought reading devices coming into the market we may get to see what kind of things are possible. Think of the Knect hacks on a brainwave scanner would be great. Not sure if they could progress enough to work though.
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Re: Scientists create illusion of having 3 arms

Postby phlip » Fri Feb 25, 2011 11:04 am UTC

Angua wrote:Yeah - you can find youtube videos of people 'adopting' rubber arms and then someone smashing it with a hammer and watching them jump (unfortunately I don't have the time to find it, and can't remember what to search for).

Like this one? (Which I saw recently via a link in MMM [edit] Actually, TIL [/edit] followed by some browsing of related videos... so could be the same one you're talking about.)

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Re: Scientists create illusion of having 3 arms

Postby Angua » Fri Feb 25, 2011 11:18 am UTC

phlip wrote:
Angua wrote:Yeah - you can find youtube videos of people 'adopting' rubber arms and then someone smashing it with a hammer and watching them jump (unfortunately I don't have the time to find it, and can't remember what to search for).

Like this one? (Which I saw recently via a link in MMM [edit] Actually, TIL [/edit] followed by some browsing of related videos... so could be the same one you're talking about.)
Yeah - that's the one I remember.
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