
Artificial arms get closer to the real thing - ColinWright
http://www.nature.com/news/artificial-arms-get-closer-to-the-real-thing-1.16111?WT.mc_id=TWT_NatureNews
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aperrien
You know, I've seen all these neural interfaces that connect electrical
impulses to nerve cells, and I wonder: why aren't we using optogenetics to
connect them instead? it would seem to me that using light to penetrate the
skin rather than metal would make for a much longer lived interface, since you
wouldn't have to worry about the body rejecting the metal. Is there some
reason that's not used?

~~~
siyer
I work in the field, so I thought I'd chime in here. Our lab (and others) have
published a few papers on using optogenetics to control peripheral nervous
system targets, but as some of the other commenters have mentioned, it's very
much in the early stages right now, and is likely to be a long way away from
human trials.

A few points:

1\. There are two relevant ways to make motor neurons light sensitive. As
another commenter mentioned, you can create a transgenic line of animals (this
is necessarily restricted to mice/rats). That's been done, and it's been shown
that you can control muscle movement in such mice [1]. In that work, a rather
interesting, and now replicated [2] observation was made, which is that if you
use optogenetics to do this (muscle control) you actually induce less fatigue
than if you use electrical stimulation to do this. Why this is the case is not
yet understood.

2\. The other (more relevant) way to do this would be to use viral vectors to
transduce the motor neurons you want to control with the light-sensitive ion
channels. We published a paper last year showing this was possible in rats
[3]. The advantage here is that you can get control over individual muscles
without any effect on unwanted muscles, through a subtlety of the injection
method used. There are naturally many caveats here, the most important being
that human gene therapy is still in its infancy, and is typically used only
for very life-threatening disorders. It's also important to note that in both
these cases, you still needed a way to deliver light to the relevant nerve.
While there's lots of work going on to make light-sensitive ion channels even
more light-sensitive, it's likely that preliminary optogenetic control of
muscle will still require implants.

3\. One of the applications talked about in the link here goes the other way -
it's focused on delivering touch information back to the brain. There's less
published here with optogenetics than there is in motor control. We've
published a paper using viral methods to control sensation earlier this year
(in mice) [4], but the type of sensation we were trying to control was pain,
not simple touch.

That said, I know that many groups are trying to develop ways to specifically
make touch-transducing neurons light sensitive - I'd be surprised if we didn't
see quite a few papers on this over the next year or two.

[1]
[http://www.nature.com/nm/journal/v16/n10/abs/nm.2228.html](http://www.nature.com/nm/journal/v16/n10/abs/nm.2228.html)
[2]
[http://www.sciencemag.org/content/344/6179/94.short](http://www.sciencemag.org/content/344/6179/94.short)
[3]
[http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna...](http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0072691)
[4]
[http://www.nature.com/nbt/journal/v32/n3/full/nbt.2834.html](http://www.nature.com/nbt/journal/v32/n3/full/nbt.2834.html)

~~~
aperrien
That's incredibly interesting! If you can treat cells to receive signals on
one end, and transmit them on the other, then can you then use some sort of
optical fiber to possibly branch around damage along a nerve path? As they
say, the internet routes around damage. Can we do the same with our nervous
system?

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FigBug
Looks more functional than my real hand. I had an arm reattached which I
believe was the wrong choice. (Doctors argued against, parents argued for) Now
I'm stuck with a useless hand that no doctor will remove. I'd rather just have
a stump and optionally a prosthetic. But I don't understand why so many
prosthetics try and appear real and end up in the uncanny valley. They are
robot arms, make them look like robots.

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cs702
Within the past two decades we have gone from prostheses that do nothing to
simple mechanical arms with _very_ limited functionality to artificial arms
that now provide much of the basic functionality as the organic ones with
which we are born.

Given the accelerating pace of innovation in this field, before long
artificial arms are bound to become better -- faster, stronger, more precise,
etc. -- than the real thing!

~~~
kefka
I'm also watching the 3d printer > sugar printing > test tube blood vessel
creation / organ structure creation > implantation. That research, blended
with adult stem cell biology shows amazing progress in recreating organs at
will.

~~~
tomjen3
It is funny, with all this new technology I fear grow older less and less.

I wonder when we will replace "healthy" organs because the natural organs are
inferier.

~~~
JoeAltmaier
We remove them already - tonsils, appendix, wisdom teeth, cataracts, vestigial
tails

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scalesolved
The tech is amazing, can't believe how fast it's progressing but as someone
that is missing a hand I'd never use one I don't think. I can see how they are
incredibly useful for people that have more difficulties.

