April 3, 2023 • 53 mins
How is it possible for a dog to become a champion surfer? Why does the world’s best archer have no arms? Why might someone come to believe that her leg doesn’t belong to her? How can we build robots that simply figure themselves out? In this episode, Eagleman unmasks mysteries about the brain's shocking flexibility -- revealing how it comes to drive whatever body it finds itself in, how it determines what the "self" is, and what this tells us about our future as humans.
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Episode Transcript
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Speaker 1 (00:05):
Why does the world's best archer have no arms? How
does a dog learn how to skateboard? How can a
robot figure out what its body looks like? How can
someone come to believe that her leg doesn't belong to
her but to someone else? And what does any of
this have to do with babies? Babbling or doc oc
(00:26):
from spider Man. Welcome to innert Cosmos with me, David Eagleman.
I'm a neuroscientist and an author at Stanford University, and
I've spent my whole career studying the intersection between how
the brain works and how we experience life. Have you
(00:54):
ever texted while you're riding your bicycle? So on campus,
i see students doing this all the time, and I'm
amazed because what it tells me is how good the
three pound brain is at controlling the body, running the
petals with the legs, and steering the handlebars with one
hand and hitting these very tiny targets with the other thumb,
(01:18):
and pulling on the brake when they need to slow down,
and so on. And this is all from inside the
brain's mission control center in the skull, in total darkness.
It's controlling all these limbs with a degree of expertise
that we can't even scratch with robotics. So what I
want to talk about today is how you can get
(01:41):
even a better body. And I'm not talking about diet
or fitness. I'm talking about the future of what we
can do with our brains. For example, could you add
new limbs. Let's start with the Spider Man comics from
back in the day, So in July of nineteen sixty three,
(02:02):
a new character got introduced. It was a scientist named
Otto Gunther Octavius. Now he was interesting because he plugs
a device directly into his brain to control four extra
robotic arms. He's able to operate these metal limbs just
as smoothly as his own natural arms, and so he's
(02:24):
able to work this way with radioactive materials. Now in
the comic book, each of his arms is able to
operate independently, in the same way that you can steer
your car with one hand while you change the radio
station with the other. And this is while at the
same time you're switching between the brake and the gas
with your foot. Unfortunately, for doctor Octavius, there's an explosion
(02:48):
and the explosion damages his brain and dooms him to
a life of villany. So he's now lost all his
sense of morality, and he capitalizes on these four extra
arms to climb up buildings and pull safes out from
walls and fight in new ways with multi hand combat.
And now with his new evil personality, he becomes known
(03:11):
as Doctor Octopus or doc OC. So when the comic
book debuted in nineteen sixty three, it was pure sci
fi fantasy to imagine that a human brain could control
robotic limbs, but not anymore. So how close are we
(03:32):
to actually reaching the point of a doc oc? Could
you plug in new limbs like extra legs or wings?
What are the limits? So to get started in understanding this,
the key thing to orient ourselves too is that the
brain has inputs and outputs. The inputs includes all the
(03:53):
information from your senses like vision, hearing, and smell and
so on. The output is how you're brain controls your
body to interact with the world. In a different episode,
I'll talk about input asking how our senses work and
how we can create new senses. But today we're going
to talk about how the brain controls the body and
(04:15):
what the prospects are for changing that or adding on
to that. So let's start back in the nineteen sixties
when a Canadian neurosurgeon named Wilder Penfield was sticking small,
thin wires called electrodes into the brain of a patient
undergoing surgery. Now, it turns out you can stick things
(04:36):
like that directly into the brain, and you can do
that while the patient is awake and it doesn't hurt
at all. Why it's because there are no pain receptors
in the brain, so you can just dunk a metal
electrode right in the tissue the way you'd stick a
toothpick in a block of cheese, and the patient doesn't
feel anything anyway. So Penfield was sticking the electrode into
(04:57):
the brain while he talked with the patient and asking
him what he was feeling. And what Penfield stumbled on
was something that elevated neuroscience. He discovered in the brain
a nap of the body. So let's say I have
the electrode right here on a little strip of brain
(05:18):
tissue where you'd wear a tiara or headphones, and the
electrode is measuring the electrical spikes in the brain cells,
the neurons, And now I touch your shoulder, and it
turns out these neurons only respond to touch on your
shoulder and nowhere else. So now let's say I move
(05:39):
the electrode just a little bit over, still on this strip,
and now I touch your elbow, and Penfield found that
as he moved over a little more, there are neurons
that respond to the forearm, and then next to that
the hand, and elsewhere along this little strip of brain
tissue he found cells that respond to your face, or
(06:01):
your torso, or your legs or your feet. And so
as you move along this strip in the brain you
find the whole body represented where neighboring territories on the
body have neighboring territory in the brain. And this came
to be known as the somatos sensory cortex, which refers
to sensation from the body, the soma. Now, the interesting
(06:25):
part for today's podcast is that he also found a
second map of the body, and this was on a
neighboring strip that we call the motor cortex. It's right
in front of that. So when the cells here are active,
they drive very particular parts of the body. In other words,
they contract particular muscles. So activity in these cells right
(06:48):
here causes your shoulder to twitch, an activity right next
to it causes your bicep to contract, and activity right
next to that causes your forearm to move, and so on.
With a map of the entire body, all the parts
that you can control are represented in this strip here. Now,
(07:09):
it turns out this map doesn't have equal representation everywhere.
The body parts, which are more finely controlled, have larger
areas of representation. So you have a bunch of territory
devoted to your fingers, for example, but not a lot
to the muscles that can move your kneecap or your scalp.
(07:30):
Now we'll come back to this in later episodes, but
what is wild is that this map of the body
is not genetically determined as everyone originally guessed. Instead, it's
shaped by the body's experience in the world. In other words,
it devotes territory to what it can control. And if
(07:51):
you lose your hand in a terrible car accident, your
primary motor cortex begins to shift, often change itself. Over
the course of weeks, the brain areas that control neighboring
arm muscles like your biceps and triceps slowly take over
the cortical territory that formerly operated your hand. Now we
(08:16):
can look at it this way. Neurons that previously drove
your hand, they get their job duty reassigned, and they
now join the team of neurons that control the upper
arm muscles. So what this tells us is that the
motor areas of the brain, those neurons that are sending
their signals down the spinal cord to drive the body,
(08:37):
they optimize themselves to drive the available machinery. And this principle,
as we're going to see, is what opens the door
to rearranging body plans, something that's traditionally been done only
when there's injury, but will soon enough be possible when
we want to add things to the body. So to
(09:01):
understand this, let's start with a wide angle lens looking
at the world of our cousins in the animal kingdom.
So the thing to notice is that there are all
sorts of strange and amazing body plans. To look at
the ant eater with its long proboscis, or an animal
called the star nosed mole, which has essentially twenty two
(09:23):
fingers on its nose with which it feels around in
its dark tunnels. Or look at the sloth or the dragonfish,
or the platypus or the octopus. You find very different
bodies in the animal kingdom. But here's the thing to notice.
All the animals, including us, have surprisingly similar genomes. So
(09:47):
how do the animal's brains come to operate all this
wildly different equipment like prehensile tails or claws, or larynxes
or tentacles, whiskers or or wings. The question is are
their brains preprogrammed for it? How do mountain goats get
(10:07):
so good at leaping up rocks? And how do owls
get so good at plunging down on mice? How do
frogs get so good at hitting flies with their tongues?
So here's what I think the answer is. In my
book Live Wired, I proposed what I call the potato
head model of the brain. And this model proposes that
(10:29):
you can plug in whatever peripheral devices you want, like
arms or fins or wings, just like plugging things into
a potato head, and the brain will figure out how
to drive them. It's kind of like with your computer.
Your laptop manufacturer doesn't have to know the next model
(10:50):
of peripheral that's going to come out in a couple
of years. Your laptop is ready to drive anything whatever
comes along. So in this potato head framework, mother nature
has the freedom to experiment genetically with any kind of
plug in play motor devices. You just plug in whatever
(11:12):
limbs you want and the brain will figure out how
to drive them. It doesn't matter if this is fingers
or flappers or fins. It doesn't matter if your body
shows up with two legs or four legs or eight legs.
It doesn't matter whether you sprout hands or talons or wings.
(11:33):
The fundamental principles of brain operation don't need to be
redesigned every time. The motor system that we're talking about
in the brain, well, it figures out how to drive
the available machinery. So the advantage of such an adaptable
brain is that it allows mother nature to mess around
(11:55):
with genetics to develop new peripheral devices. And it turns
out it's shockingly easy for her to make little adjustments
to the a's and seas and teas and gees, and
you end up with all kinds of different body plants. Okay, now,
wait a mind it, you might say, If bodies are
so easy to modify with tweaks of the genome, how
(12:19):
can we don't see things like a human sometimes being
born with a genetic mutation that gives him a tail
or an extra arm. Well you do. Actually, it turns
out that some genes in your genome act like movie directors.
They carefully control which thing happens when and where, and
(12:41):
in this case, which other gene cascades get triggered to unpack.
So in fruit flies, a few decades ago, it was
discovered that certain mutations in these director genes control the
development of the larger body structure. One of the first
discoveries involved a mutation in the fruit flies in which
(13:05):
a pair of legs would grow where the antennae were
supposed to be, and there's a reverse mutation which placed
antennae where the legs should be. So when you start
looking at the building of the body this way, you
see it's sort of like lego. You can just swap
one thing out for another. Based on these genes coated
in a's and seas and teas and geese. If you
(13:27):
want to look this up further, look up homeobox genes.
The big point I want to make here is just
that some genes act as a switch to turn on
a cascade of other genes, and this is why many
mutations involve the surprising appearance or disappearance of a full
body part. So in humans you can find these surprisingly
(13:50):
small mutations where, for example, a child is born with
a tail, it's just a genetic program which extends the
spinal column and keeps it going. Every year, there are
hundreds of children born with tails, and the tail gets
simply removed with an operation. In Live Wired, I tell
(14:10):
the story of a baby named Gigi who was born
in China a few years ago, and Gigi had three arms. Now,
for the COGNISCINTI, I'll just mention that this sort of
thing sometimes happens because of a parasitic twin in the womb,
where one twin doesn't make it and gets absorbed into
the body of the healthier twin. But that's not the
(14:33):
case with Gigi. His genetics simply dictated the growth of
a third arm. The surgeons in China took several hours
to remove one of the arms because both arms on
the left side were well developed and had individual shoulder blades. Now,
what tails and extra arms illustrate is the way body
(14:55):
plants can change with small alterations of the genetics. And
it goes without saying that this sort of genetic wobble
happens in minor ways all around us. Some people have
longer arms, or stubby your fingers, or a big toe
that's shorter than the second toe, or wider hips or
broader shoulders. And although our nearest cousins, the chimpanzees, are
(15:19):
nearly genetically identical to us, they have a lot of
differences in their body plan. For starters, their bicep muscle
has a higher insertion point, and their hips are turned
more outward, and their toes are much longer. Now, the
point is that the chimpanzee brain, with its mere ninety
(15:39):
thousand genes, doesn't have to be reinvented to figure out
how to drive a chimpanzee body to swing in trees
and to walk on knuckles. And by the same token,
the human brain doesn't have to be reinvented to figure
out how to play pickleball or dance hip hop. In
both cases, the brain just figures out how to best
(16:02):
drive the machinery that it has. So to understand the
power of this principle, consider Matt Stutsman. This is a
(16:26):
guy who is born without arms. He found himself really
attracted to archery, so he learns to manipulate a bow
and arrow with his feet. What he does is notch
the arrow into the string with his toes. Then he
lifts the bow with his right foot, and he's got
a strap around his neck which connects the bow to
(16:48):
his shoulder, and that allows him to position it at
eye level. And then he puts tension on the bow
by pushing it forward with his foot, and when his
aim is on target, he lets the arrow fly. Now,
the thing is that Matt is not simply talented at archery.
He is the best in the world. As of this podcast,
he holds the record for the longest accurate shot in archery.
(17:13):
And that's probably not what his doctors would have predicted
for a baby who came out of the womb without arms,
But perhaps they didn't realize how readily his brain would
adapt its resources to solve problems in the outside world.
Now we see this sort of flexibility everywhere in the
animal kingdom. Consider this incredible dog whose name is Faith,
(17:37):
who was born without front legs, and she grew from
puppyhood to be able to walk on her two hind
legs bipetally the way that a human walks. You can
find YouTube videos of her walking around. It's totally amazing
to watch. And although we might have guessed that dog
brains come hardwired to drive standard dog bodies, Faith shows
(18:02):
us how readily brains will move around the world with
whatever machinery they find themselves in. So what we see
from Matt or from Faith the Dog is that brains
are not predefined for particular bodies. Instead, they adapt themselves
to move and interact and succeed in the world. And
(18:23):
this isn't simply about the body you're born in, but
about whatever opportunities might come along. So take Sir Blake,
a bulldog here in California who's mastered skateboarding. He steps
up onto the skateboard and with his front paw he
scrapes at the ground to get momentum, and at the
(18:43):
right moment, he sets his front paw onto the board
and he leans into the ride, and he shifts his
body weight to steer the board around obstacles, just like
a human wood. And when he's done, he lets the
skateboard slow down almost to a stop, and then he dismount. Now,
given the absence of wheels in the evolutionary history of dogs,
(19:05):
what this shows is the adaptability of brains to steer
new possibilities. Or take this other dog named Sugar who
took up surfboarding and is inducted into the International Surf
Dog Walk of Fame, or on second thought, forget Sugar
and just revel in the fact that there is an
(19:27):
International Surf Dog Walk of Fame, because there are lots
of dogs that do this, and we don't usually think
about studying dog brains in the context of how they
hang ten on a longboard, but you can, because all
the dog requires is the opportunity and their motor systems
will figure it out. So how do these dogs do it?
(19:51):
And what does this have to do with a baby babbling? Well,
a baby learns how to shape its mouth and breathing
to produce language. But this is not from genetics, and
it's not by studying a book or surfing Wikipedia. It's
from babbling. They listen to what's going on around them,
and they try things out, and their brain compares how
(20:15):
close their own sound was to what they're hearing from
the adults around them. And this has helped long because
they get positive reactions for some utterances and not for others.
And so there's this constant feedback loop, and that allows
babies to refine their speech to perfection in whatever language
(20:35):
is being spoken around them, whether that's English or Chinese
or Hindi or any of the seven thousand languages spoken
around the globe. In exactly the same way, the brain
learns how to steer its body by motor babbling, in
other words, babbling with its slims. Just watch a baby
(20:56):
in the crib. She bites her toes, she slaps her forehead,
she tugs on her hair, she bends her fingers, she
knocks on the bar of the crib, and so on.
And by doing this, she's learning how her motor output
corresponds to the sensory feedback she receives. And in this way,
(21:18):
she's learning to understand the language of her body, how
her outputs nap onto the next inputs. She's trying things
out and she's getting feedback, and this is how she
eventually learns how to walk and navigate food to her mouth,
and eventually swim in a pool and dangle on monkey
(21:38):
bars and master a cartwheel. She's trying things out, she's adjusting,
she's motorically babbling. And even better, we use this same
method to attach extensions to our bodies. So think about
riding a bicycle, which is a machine that our genome
presumably did not see coming to master bike riding. Have
(22:00):
to carefully balance your torso, and you change direction by
moving your arms, and you have to stop by squeezing
your hands, and this is all totally different from the
way we normally move. But despite these complexities, most five
year olds can demonstrate that the extended body plan is
(22:20):
easily added to the resume of their motor cortex. And
this isn't just limited to typical bicycles. Consider the sky
named Deston Sandlin. He's an engineer who has given this
very strange bicycle by a friend. It had this elaborate
gearing system so that if you turned the handlebars to
(22:40):
the left, the front wheel would turn to the right,
and vice versa. And so Deston was fairly sure that
this wouldn't be too difficult to master because the concept
is very straightforward. You just steer the opposite direction that
you want to go. But as it turned out, the
bicycle was just too difficult to ride because it required
(23:03):
unlearning the normal operation of a bicycle steering wheel and
training his motor cortex to master this new task was
not as simple as having a cognitive understanding. In other words,
he knew how the bicycle worked, but that didn't mean
he could do the right thing with his body. But
after some weeks he began to get the hang of it.
(23:24):
He practiced every day, and each time he'd try to move,
he would get feedback from the world, like you're falling
to the ride, or you're crashing into a trash can,
or you're swerving in front of the mail truck. And
so he used that feedback to adjust his next moves,
and after several weeks of practicing, he got pretty good
at it. And he did this the same way that
(23:47):
he learned how to ride a normal bike as a kid,
by motor babbling. And by the way, you know what
this is like If you drive and you go to
a country that has the steering wheel on the other
side of the car, if you or an American in
England or vice versa, you keep swerving the wrong way,
but you eventually get better because your visual system looks
(24:08):
at the consequences of each action and adjusts things accordingly.
It's just how Matt Stutsman learned how to shoot bows
or sugar learned how to skateboard. Motor babbling is not
only the way that babies and bicyclists learn, it's also
become a new approach in robotics. So take this starfish
robot developed by my colleague Hodd Lipson. The idea is
(24:32):
that it's a very simple robot. It's just a small
square body with four arms that stick out. The key
is lips and doesn't teach it how to use its body.
It figures itself out. The starfish tries out a move
the way that an infant might flail a limb, and
it analyzes what happens. In the robots case, it's just
(24:55):
using gyroscopes to see how the move tilted the central bot.
So if it does just a single move, that can't
tell it what its body looks like and how it
interacts with the world. But that feedback narrows the space
of possibilities, so it now has a smaller space of
hypotheses about what its body looks like. So now it
(25:17):
does the next move, and the next and so on,
and instead of choosing random movements, it chooses its next
move to do a good job distinguishing the available remaining
hypotheses so by doing this over and over, by motoric babbling,
it develops a clearer and clearer picture of its body.
(25:39):
In this way, it learns itself. You don't need a
preprogram this robot. It learns its own capabilities. And what's
wild is that if you snap off one of the
legs of this robot, it'll figure itself out again. And
it turns out that building a babbling, self exploring robot
is way more flexible than preprogramming the robot. And in
(26:02):
the animal kingdom, nature only has some tens of thousands
of genes to work with to build a creature, so
it can't possibly preprogram all of the actions that one
might do in the world. So it's only choice is
to build a system that figures itself out. Now, think
(26:22):
about the stories that we just talked about with Matt Stutsman,
the archer with no arms, or the skateboarding dog or
the surfing dog or the starfish robot. What they all
have in common is the same principle, whatever kind of
way that you can move around in the world, the
brain on the inside does not have to be redesigned.
It just recalibrates to maximize what it can do. It
(26:47):
figures out how to control whatever body it's in. A
live wired brain doesn't need to be redesigned if there's
a genetic change to the body, planet just adjusts itself.
And that is how evolution can so effectively shape animals
to fit any habitat in different environments. Animals will evolve
(27:09):
hoofs or toes or fins or forearms or trunks or
tails or talons, and Mother Nature doesn't need to reinvent
the principles of the brain or do anything extra to
make the new animal operate correctly. And you know what,
Evolution really couldn't work any other way. It couldn't operate
(27:29):
quickly enough unless body plan changes were easy to deploy
and brain changes just followed without difficulty. And this massive
flexibility is why we can so easily install ourselves into
new bodies. If you ever saw the movie Aliens from
a long time ago, you may remember this climactic deathmatch
(27:51):
that the hero Ellen Ripley has with this giant, slimy alien.
So she scrambles into this enormous robotics just like a
mech suit that allows her movements to be magnified into
these powerful metal arms and legs, and at first, she's
swinging around awkwardly, but after some practice, she's able to
(28:14):
land punches right on the alien. Now what we see
is that Ripley learns how to control her new gargantuan
body plan, and she does so thanks to her brain's
capacity to adjust her relationship between her outputs like swinging
my arm and her inputs. Wears that giant arm right now.
(28:35):
So it's not difficult to learn these kinds of new associations.
Just think about forklift drivers who are using their arms
and these little levers to control something really large, or
crane operators who are sitting in their little booth and
operating this thing that's one hundred feet high, or laparoscopic
surgeons who are controlling levers to control something that's very
(28:58):
very tiny. So all of these folks get out of
bed every morning to pilot strange new bodies. And let's
take another example. There was a very successful young man
named Jean Dominique Bobie who lived in Paris, and he
was on top of the world. He was editor in
chief at El magazine in Paris, and he revolved at
(29:21):
the top of French social circles. And one afternoon in
nineteen ninety five, without any warning, he had a massive
stroke and he instantly fell into a deep coma. So
he stayed in this coma for twenty days, and just
when everyone was giving up hope, he regained consciousness. But
(29:42):
there was a problem. It's the type of thing that
gives everyone who hears about this nightmares, which is that
he was mentally aware. He could see his surroundings, he
could understand everything everyone was saying, but he could not move.
He couldn't twitch his arm, his fingers, his face, his toes.
He couldn't speak, he couldn't cry out. He discovered that
(30:05):
his only available action was to blink his left eyelid.
Other than that, he was locked in the frozen dungeon
of his body. This is called locked in syndrome. So
luckily he had a heroic nurse with a plan. She
would sit with him and recite all of the letters
(30:26):
in the alphabet in the order of their frequency, and
he would blink his eye when she arrived at the
next letter he wanted, and in this way, one letter
at a time, he could communicate, and eventually he wrote
out an entire book called The Diving Bell in the Butterfly.
(30:46):
He died just before I was published. But this became
a huge international bestseller, in part because it allowed readers
to appreciate, probably for the first time, this simple pleasure
of having a brain that successfully drives this enormous meat robot,
and does so with such expertise that were totally unaware
(31:09):
of the massive operations running under the hood. Now here's
the question, what if we could have measured the little
electrical signals in Bobie's brain, the spikes and his neurons,
instead of having to look just at his eyeblinks. What
if we could have eaves dropped on his neural circuits
to figure out what they were trying to say to
(31:31):
the muscles, and then by passed the injury to make
something happen in the outside world. Well, a year after
Bobie's death, researchers at Emory University implanted a brain computer
interface into another locked in patient named Johnny Ray, and
Johnny Ray lived long enough to control a computer cursor
(31:53):
simply by imagining the movement. His motor cortex was unable
to get the signals through the damaged spinal cord, but
this implant could listen to the signals and then pass
along that message to the computer. Then, in two thousand
and six, a paralyzed former football player named Matt Nagel
(32:14):
was able to control lights and open an email, and
play the video game Pawn and draw a circle on
the screen. And this was all because of a four
by four millimeter grid of almost one hundred electrodes implanted
directly into his motor cortex. He would imagine moving his muscles,
which caused activity in his motor cortex, and the researchers
(32:37):
could measure that activity to at least crudely determine the intention.
The technology used with Johnny and Matt it was makeshift
and unpolished, but had proved the possibility, and by twenty eleven,
my neuroscience colleague Andrew Schwartz and his colleagues at the
University of Pittsburgh built a prosthetic arm was almost as
(33:01):
sophisticated and lie as a real arm. And a woman
named Jan Schumann had become paralyzed from a disorder called
spinocerebellar degeneration, and she volunteered herself for a neurosurgery that
would give her control of this arm. So, with the
signals recorded from her motor cortex, Jan imagines making a
(33:25):
movement with her arm, and the robotic arm moves. This
robotic arm is part way across the room, but this
makes no difference because through the bundle of wires that
attaches these electrodes in her brain to the computer and
to the robotic arm, she can make it turn and grasp,
(33:45):
essentially the way that she would have done with her
own arm years ago. Normally, when you think about moving
your arm, the signals traveled from the motor cortex down
your spinal cord, into the peripheral nerves into your muscle fibers.
With Jan, the signals recorded from the brain just take
a different root. They're going long wires connected to motors
(34:05):
instead of neurons connected to muscles. So Jan gets better
and better at using the arm, in part because of
improving technology, but also because her brain is rewiring to
understand how to best control its new limb, just as
it would with a reversed bicycle or a surfboarder Ellen
Ripley's mex suit. Jan is doing motor babbling to figure
(34:29):
out how to drive the arm smoothly, and in an interview,
by the way, Jan said, I'd so much rather have
my brain than my legs. Why did she say that.
It's because if you have the brain, you can build
a new body, but not the other way around. So
we see that brain machine interfaces can restore or replace
(34:52):
damaged limbs, But the question is could you use this
same technology to add an additional limb. So in two
thousand and eight, a monkey with two normal arms used
its thoughts to control a third arm made of metal.
This was again the work of my colleague Andrew Schwartz.
He and his team put a tiny array of electrodes
(35:15):
into the monkey's brain, and when the monkey thought about
different things, that could control the robotic arms to pluck
marshmallows and stick them in his mouth with the robotic arm.
The monkey initially trained for this by moving a cursor
on the screen towards a target, and he'd get rewarded
when he got it right. And at first, the monkey
(35:36):
would move his own arms while he was doing the task.
But something remarkable happened, which is eventually he stopped moving
his arms and the cursor continued to move on its own.
His brain was rewiring to separate out these tasks, so
some neurons corresponded to his real arms and some to
(35:58):
the cursor on screen. Eventually, these signals were able to
be used to control the robotic arm for marshmallow gathering
and sticking in his mouth, all without any physical movement
of his real arms. It had become a new limb,
a third limb. The way that the monkey learned to
(36:19):
use the robotic arm independently of its real arms recalls
docc the character from Spider Man, who controlled his robotic
limbs even while doing other tasks with his flesh hands.
So it shouldn't seem surprising that humans and monkeys can
figure out how to move robotic arms with their thoughts.
(36:41):
It's the same process by which your brain learned to
control your natural, fleshy limbs. As we've seen. Your process
as a baby was to flail your appendages around and
bite your toes in grass your crib bars and poked
(37:01):
yourself in the eye and turn yourself over. For years,
this is how you fine tuned the operation of your machinery.
Your brain sends out commands, compares those with feedback from
the world, and eventually learns the capabilities of your limbs.
So your skin covered arm is really no different from
(37:21):
the clunky, silver robotic arm of the monkey. It just
happens to be the standard operating equipment you're used to,
so you often end up blind to its amazingness. So
for both jan and the monkeys, the robotic arms were
not directly connected to their torsos, but instead connected by
(37:43):
a bundle of wires. The electrodes in their brain sent
wires to a computer which does the processing, and then
the bundle of wires goes from the computer to the
robotic arm. But increasingly this can be done wirelessly, and
that means the robotic arm that you're controlling does it
need to be right next to you or even in
the same room. So could you control a robot on
(38:06):
the other side of the world. While in two thousand
and eight, my colleague Miguel Nikolaylis and his team from
Duke University hooked up electrodes to a monkey and that
monkey controlled the walking patterns of a robot halfway across
the globe. So the monkey would walk on a treadmill,
(38:29):
and the signals from his motor cortex were recorded and
translated into zeros and ones and transmitted via the Internet
to a laboratory in Japan and fed into a robot there.
And while the monkey walked, the five foot tall, two
hundred pound robot would also walk like a metal doppelganger.
(38:49):
So after they demonstrated this proof of principle, the Duke
team stopped the treadmill. But as the monkey looked at
its avatar on the screen, it's thought about walking, and
so the robot Japan kept marching along. So in the
same way that Jan imagines movements and the arm executes
(39:11):
our internal commands, the monkeys motor cortex continued to think
about walking even while he wasn't doing it, and the
robot kept going. So in the not too distant future,
it seems inevitable that we're going to have mind controlled
robots in factories or underwater or on the surface of
(39:31):
the moon. And it's all from the comfort of our
own couches. And this is because our cortical maps, after
extensive training, will be able to incorporate whatever the limbs
of the robot are. That's going to become our tell limbs.
So think about the way we watch television, which means
(39:54):
far sight. I'm coining the term tell limbs because in
the near future, we're going to be control rolling far bodies.
(40:16):
So the bodies that we have right now have evolved
for the conditions of this particular oxygen rich planet. But
leveraging the brain's plasticity to build long distance bodies, that's
surely going to be our main strategy for space exploration.
(40:37):
So what consequence would expanding your body, say with a
robotic arm or a metal avatar across town. What consequence
would this have for your conscious experience? The answer is
that the robot will be perceived as a part of you.
The robot will just be another limb. Now, it's an
(40:58):
unusual limb because of the physical gap between you and it,
but it nonetheless will qualify just as a new limb.
The only reason we're accustomed to connected limbs is that
Mother Nature is a talented seamstress with muscle and sinew
and nerves, but she never worked out how to control
(41:19):
distant limbs via bluetooth. Now, if extra limbs or telelimbs,
if the seems exotic, recall that you have everyday experience
with them. Just look in a mirror and move your arm.
You see a distant object, move in perfect synchrony with
your motor commands. And although babies are at first confused
(41:42):
by mirror images, they come to understand the reflections as themselves,
because although they don't feel any direct sensation from those
distant limbs, they can witness their control over them, and
that's enough for these limbs to be annexed by self hood.
So this notion of this self is analogous to the
(42:04):
borg in Star Trek, who assimilate everything in their path
into their singular identity, except for those things that can't control,
like the impossibly unpredictable Captain Picard. Now this led me
to propose an axiom in Live Wired about the nature
of selfhood. What the body can control becomes the self.
(42:30):
And I think this all pivots on predictability. In other words,
can I predict that signals from my brain will cause
something to happen out there? So this relationship of selfhood
and predictability it allows us to understand disorders such as
asmatic noosa, which translates to not knowing one's body. So
(42:52):
in asmatic noosa, damage to the right pridal lobe of
the brain, say by a stroke or a tumor, means
that a person is no longer able to control a limb,
and as a completely gobsmacking result, the patient will deny
that the limb belongs to her, and sometimes will insist
(43:13):
that the limb belongs to someone else. She will attribute
the arm to a dead friend or a relative, or
a phantasm or a devil, or one of the medical
professionals taking care of her. She'll say that it's not
her arm. She'll explain that her own real arm was
(43:33):
stolen or is simply missing. The manifestations of this can
be varied and strange, So a patient may feel totally
indifferent towards her no longer self limb, or she might
be delusional about it and come up with strange fabrications
to explain what happened, such as saying someone's so this
(43:56):
onto my body, or other patients might sympathetically describe their
limbs as something that they dislike, like a deadweight. And
in a more vicious version of this breakdown of selfhood,
a patient may hate her alien limb, and she might
curse at it and hit it. So there's no gold
(44:17):
standard for this disorder, but you probably have no trouble
guessing my proposal in Live Wired, which is the brain
can no longer control the limb, and so the limb
falls from the brotherhood of the self. It no longer
is part of you. Now. Sometimes these patients will have
a small window of lucidity in which they re recognize
(44:40):
their limb as their own, but it doesn't last long,
And I hypothesize that this may result when the arm
happens to behave like they intended. So it's accidental predictability.
Given a person's lifelong experience of controlling her arm, it
doesn't come as a surprise that even a temporary impression
of control can snap it back into alignment with this self,
(45:04):
if only for a moment. Now, by the way, I
suspect this sense of predictability is related to the way
that a person that you know deeply, like a family member,
becomes something like a part of yourself. Of course, humans
are way too complex to predict perfectly, and the degree
to which your spouse acts surprisingly is the extent to
(45:28):
which he or she remains independent. Okay, Now, one doesn't
need prosthetics or brain surgery to try out new bodies.
The developing field of avatar robotics allows the user to
control a robot at a distance, seeing what it sees
and feeling what it feels. So take something called the
(45:50):
shadow hand, which is one of the most intricate artificial
hands in existence. Each fingertip is equipped with sensors which
feed their data back into haptic gloves that are worn
by the user, So sending data over the internet, one
can control a robotic hand. In London from Silicon Valley
(46:12):
and other groups are working on disaster recovery avatars. These
are robots that are sent in after earthquakes or terrorist
attacks or fires, and the ideas that they can be
piloted by drivers that are sitting somewhere else that's safe. Now,
I haven't yet heard of people using strange bodied avatars,
(46:33):
but they certainly could. Just as the brain learns skis
or trampolines or pogo sticks, it can learn to become
one with a weird and wonderful avatar body. So this
field of avatar robotics is going to allow people to
try out extended or strange bodies. But let's note that
(46:54):
it's super expensive and luckily there's a better way to
try out different body plans, and that's inside virtual reality.
So inside a simulated space, you can make massive changes
to your body plan instantly, inexpensively. So imagine looking into
a mirror in your VR world, you lift your arm,
(47:17):
and you see your virtual avatar in the mirror, raise
its arm, you tilt your neck in the avatar tilts
its neck. Now, imagine that this avatar has not your face,
but that of an Ethiopian woman, or a Norwegian man,
or a Pakistani boy, or a Korean grandmother. So, for
(47:37):
the reasons that we just saw about how the brain
determines selfhood, if I can control what it does, it
becomes me. It only takes a few moments of motor
babbling in front of this VR mirror to convince yourself
that you now inhabit a different body. You can then
walk around in the VR world as a different in person,
(48:00):
experiencing life through a modified identity. Self identity, by the way,
is surprisingly flexible. Researchers have been studying this in recent years,
how taking on the face of a different person can
enhance empathy, but taking on a new face that's just
the beginning. So in the late nineteen eighties, because of
(48:22):
a coding error, the VR study of unusual bodies began.
A scientist was inhabiting the avatar of a dockworker in
VR when a programmer accidentally made his arm enormous, like
the size of a construction crane because he inserted too
many zeros into the scaling factor. And to everyone's surprise,
(48:46):
the person in VR was none less able to figure
out how he could operate accurately and efficiently with this megaarm.
And so this led people to wonder what kind of
bodies could be occupied. So my friend Jaron Lanier and
his colleague An Lasco made an experience in which people
(49:06):
inhabited the bodies of eight legged lobsters. So your two
arms controlled the first two arms of the lobster, and
then they tried out several complicated algorithms to control the
other arms. And it was pretty tough work to control
the eight legs of the lobster, but apparently some people
(49:27):
were able to make it come to pass. So Jaron
coined the term homuncular flexibility. The homunculus is the little
man inside your head, the little naps. He coined this
term homuncular flexibility to capture the surprising elasticity of the
brain's representation of its body. Some years later, my Stanford
(49:50):
colleague Jeremy Baylinson and his team set out to test
homuncular flexibility more scientifically. They asked whether people could learn
to act accurately control a third arm in VR. So
imagine strapping on the VR goggles and you grasp two
controllers in your hand, and so you can see your
(50:11):
own arms in virtual space, and you see an additional
arm as well, coming out from the middle of your chest.
The task is pretty simple. You touch a box as
soon as it changes color. But there are a lot
of boxes, and to do well you have to employ
all three arms. So the first two virtual arms are
(50:31):
simply controlled by your own arms, and the third arm
is controlled by rotating your wrists. Within three minutes, users
got it. They could accommodate the new body plan with
this third arm and do the task really well. There's
really no limit to the physiques or body plans that
you could explore. Imagine finding a virtual tail protruding from
(50:56):
your tail moan which you could accurately control with your movement,
or becoming the size of a golf ball or the
size of a building, or having six fingers, or becoming
a housefly with wings, or like doc oc, becoming an octopus.
Marrying the flexibility of the brain to the burgeoning creativity
(51:20):
of the VR design world. This is why we're moving
into an era in which our virtual identities are not
going to be limited by the bodies that we happen
to have evolved. What we can do instead is speed
up evolution from eons to hours. We can explore bodies
that Mother Nature couldn't dream of, making virtual avatars reel
(51:46):
to the brain. So let's wrap this up. We saw
with Matt the archer or Faith the dog that brains
adjust to drive whatever body they find themselves in, and
like Jam's robotic arm, brains can also figure out how
to operate new hardware additions. Massive networks of brain cells
(52:11):
pull off this trick by putting out motor commands like
lean to the left and assessing the feedback like the
skateboard tilted and wobbled, and then it adjusts its parameters
to climb the mountain of expertise. So our progeny won't
have to limit themselves to the boundaries of their bodies. Instead,
(52:33):
they're going to be able to extend across the universe
according to whatever is under their control. Imagine learning how
to control a drone as part of your body, or
build robotic wings and control them with your thoughts, just
how you control your arms and flying across the city
that way, or imagine having a sail for balancing, or
(52:56):
a propeller or peripheral devices like a forklift. How would
you build a better body than the one you inherit
it from a long road of evolution. That's all for
this week. To find out more and to share your thoughts,
head over to eagleman dot com, slash podcasts, and you
(53:18):
can also watch full episodes of Inner Cosmos on YouTube.
Subscribe to my channel so you can follow along each
week for new updates until next time. I'm David Eagleman,
and this is Inner Cosmos.
Why does the world's best archer have no arms? How
does a dog learn how to skateboard? How can a
robot figure out what its body looks like? How can
someone come to believe that her leg doesn't belong to
her but to someone else? And what does any of
this have to do with babies? Babbling or doc oc
(00:26):
from spider Man. Welcome to innert Cosmos with me, David Eagleman.
I'm a neuroscientist and an author at Stanford University, and
I've spent my whole career studying the intersection between how
the brain works and how we experience life. Have you
(00:54):
ever texted while you're riding your bicycle? So on campus,
i see students doing this all the time, and I'm
amazed because what it tells me is how good the
three pound brain is at controlling the body, running the
petals with the legs, and steering the handlebars with one
hand and hitting these very tiny targets with the other thumb,
(01:18):
and pulling on the brake when they need to slow down,
and so on. And this is all from inside the
brain's mission control center in the skull, in total darkness.
It's controlling all these limbs with a degree of expertise
that we can't even scratch with robotics. So what I
want to talk about today is how you can get
(01:41):
even a better body. And I'm not talking about diet
or fitness. I'm talking about the future of what we
can do with our brains. For example, could you add
new limbs. Let's start with the Spider Man comics from
back in the day, So in July of nineteen sixty three,
(02:02):
a new character got introduced. It was a scientist named
Otto Gunther Octavius. Now he was interesting because he plugs
a device directly into his brain to control four extra
robotic arms. He's able to operate these metal limbs just
as smoothly as his own natural arms, and so he's
(02:24):
able to work this way with radioactive materials. Now in
the comic book, each of his arms is able to
operate independently, in the same way that you can steer
your car with one hand while you change the radio
station with the other. And this is while at the
same time you're switching between the brake and the gas
with your foot. Unfortunately, for doctor Octavius, there's an explosion
(02:48):
and the explosion damages his brain and dooms him to
a life of villany. So he's now lost all his
sense of morality, and he capitalizes on these four extra
arms to climb up buildings and pull safes out from
walls and fight in new ways with multi hand combat.
And now with his new evil personality, he becomes known
(03:11):
as Doctor Octopus or doc OC. So when the comic
book debuted in nineteen sixty three, it was pure sci
fi fantasy to imagine that a human brain could control
robotic limbs, but not anymore. So how close are we
(03:32):
to actually reaching the point of a doc oc? Could
you plug in new limbs like extra legs or wings?
What are the limits? So to get started in understanding this,
the key thing to orient ourselves too is that the
brain has inputs and outputs. The inputs includes all the
(03:53):
information from your senses like vision, hearing, and smell and
so on. The output is how you're brain controls your
body to interact with the world. In a different episode,
I'll talk about input asking how our senses work and
how we can create new senses. But today we're going
to talk about how the brain controls the body and
(04:15):
what the prospects are for changing that or adding on
to that. So let's start back in the nineteen sixties
when a Canadian neurosurgeon named Wilder Penfield was sticking small,
thin wires called electrodes into the brain of a patient
undergoing surgery. Now, it turns out you can stick things
(04:36):
like that directly into the brain, and you can do
that while the patient is awake and it doesn't hurt
at all. Why it's because there are no pain receptors
in the brain, so you can just dunk a metal
electrode right in the tissue the way you'd stick a
toothpick in a block of cheese, and the patient doesn't
feel anything anyway. So Penfield was sticking the electrode into
(04:57):
the brain while he talked with the patient and asking
him what he was feeling. And what Penfield stumbled on
was something that elevated neuroscience. He discovered in the brain
a nap of the body. So let's say I have
the electrode right here on a little strip of brain
(05:18):
tissue where you'd wear a tiara or headphones, and the
electrode is measuring the electrical spikes in the brain cells,
the neurons, And now I touch your shoulder, and it
turns out these neurons only respond to touch on your
shoulder and nowhere else. So now let's say I move
(05:39):
the electrode just a little bit over, still on this strip,
and now I touch your elbow, and Penfield found that
as he moved over a little more, there are neurons
that respond to the forearm, and then next to that
the hand, and elsewhere along this little strip of brain
tissue he found cells that respond to your face, or
(06:01):
your torso, or your legs or your feet. And so
as you move along this strip in the brain you
find the whole body represented where neighboring territories on the
body have neighboring territory in the brain. And this came
to be known as the somatos sensory cortex, which refers
to sensation from the body, the soma. Now, the interesting
(06:25):
part for today's podcast is that he also found a
second map of the body, and this was on a
neighboring strip that we call the motor cortex. It's right
in front of that. So when the cells here are active,
they drive very particular parts of the body. In other words,
they contract particular muscles. So activity in these cells right
(06:48):
here causes your shoulder to twitch, an activity right next
to it causes your bicep to contract, and activity right
next to that causes your forearm to move, and so on.
With a map of the entire body, all the parts
that you can control are represented in this strip here. Now,
(07:09):
it turns out this map doesn't have equal representation everywhere.
The body parts, which are more finely controlled, have larger
areas of representation. So you have a bunch of territory
devoted to your fingers, for example, but not a lot
to the muscles that can move your kneecap or your scalp.
(07:30):
Now we'll come back to this in later episodes, but
what is wild is that this map of the body
is not genetically determined as everyone originally guessed. Instead, it's
shaped by the body's experience in the world. In other words,
it devotes territory to what it can control. And if
(07:51):
you lose your hand in a terrible car accident, your
primary motor cortex begins to shift, often change itself. Over
the course of weeks, the brain areas that control neighboring
arm muscles like your biceps and triceps slowly take over
the cortical territory that formerly operated your hand. Now we
(08:16):
can look at it this way. Neurons that previously drove
your hand, they get their job duty reassigned, and they
now join the team of neurons that control the upper
arm muscles. So what this tells us is that the
motor areas of the brain, those neurons that are sending
their signals down the spinal cord to drive the body,
(08:37):
they optimize themselves to drive the available machinery. And this principle,
as we're going to see, is what opens the door
to rearranging body plans, something that's traditionally been done only
when there's injury, but will soon enough be possible when
we want to add things to the body. So to
(09:01):
understand this, let's start with a wide angle lens looking
at the world of our cousins in the animal kingdom.
So the thing to notice is that there are all
sorts of strange and amazing body plans. To look at
the ant eater with its long proboscis, or an animal
called the star nosed mole, which has essentially twenty two
(09:23):
fingers on its nose with which it feels around in
its dark tunnels. Or look at the sloth or the dragonfish,
or the platypus or the octopus. You find very different
bodies in the animal kingdom. But here's the thing to notice.
All the animals, including us, have surprisingly similar genomes. So
(09:47):
how do the animal's brains come to operate all this
wildly different equipment like prehensile tails or claws, or larynxes
or tentacles, whiskers or or wings. The question is are
their brains preprogrammed for it? How do mountain goats get
(10:07):
so good at leaping up rocks? And how do owls
get so good at plunging down on mice? How do
frogs get so good at hitting flies with their tongues?
So here's what I think the answer is. In my
book Live Wired, I proposed what I call the potato
head model of the brain. And this model proposes that
(10:29):
you can plug in whatever peripheral devices you want, like
arms or fins or wings, just like plugging things into
a potato head, and the brain will figure out how
to drive them. It's kind of like with your computer.
Your laptop manufacturer doesn't have to know the next model
(10:50):
of peripheral that's going to come out in a couple
of years. Your laptop is ready to drive anything whatever
comes along. So in this potato head framework, mother nature
has the freedom to experiment genetically with any kind of
plug in play motor devices. You just plug in whatever
(11:12):
limbs you want and the brain will figure out how
to drive them. It doesn't matter if this is fingers
or flappers or fins. It doesn't matter if your body
shows up with two legs or four legs or eight legs.
It doesn't matter whether you sprout hands or talons or wings.
(11:33):
The fundamental principles of brain operation don't need to be
redesigned every time. The motor system that we're talking about
in the brain, well, it figures out how to drive
the available machinery. So the advantage of such an adaptable
brain is that it allows mother nature to mess around
(11:55):
with genetics to develop new peripheral devices. And it turns
out it's shockingly easy for her to make little adjustments
to the a's and seas and teas and gees, and
you end up with all kinds of different body plants. Okay, now,
wait a mind it, you might say, If bodies are
so easy to modify with tweaks of the genome, how
(12:19):
can we don't see things like a human sometimes being
born with a genetic mutation that gives him a tail
or an extra arm. Well you do. Actually, it turns
out that some genes in your genome act like movie directors.
They carefully control which thing happens when and where, and
(12:41):
in this case, which other gene cascades get triggered to unpack.
So in fruit flies, a few decades ago, it was
discovered that certain mutations in these director genes control the
development of the larger body structure. One of the first
discoveries involved a mutation in the fruit flies in which
(13:05):
a pair of legs would grow where the antennae were
supposed to be, and there's a reverse mutation which placed
antennae where the legs should be. So when you start
looking at the building of the body this way, you
see it's sort of like lego. You can just swap
one thing out for another. Based on these genes coated
in a's and seas and teas and geese. If you
(13:27):
want to look this up further, look up homeobox genes.
The big point I want to make here is just
that some genes act as a switch to turn on
a cascade of other genes, and this is why many
mutations involve the surprising appearance or disappearance of a full
body part. So in humans you can find these surprisingly
(13:50):
small mutations where, for example, a child is born with
a tail, it's just a genetic program which extends the
spinal column and keeps it going. Every year, there are
hundreds of children born with tails, and the tail gets
simply removed with an operation. In Live Wired, I tell
(14:10):
the story of a baby named Gigi who was born
in China a few years ago, and Gigi had three arms. Now,
for the COGNISCINTI, I'll just mention that this sort of
thing sometimes happens because of a parasitic twin in the womb,
where one twin doesn't make it and gets absorbed into
the body of the healthier twin. But that's not the
(14:33):
case with Gigi. His genetics simply dictated the growth of
a third arm. The surgeons in China took several hours
to remove one of the arms because both arms on
the left side were well developed and had individual shoulder blades. Now,
what tails and extra arms illustrate is the way body
(14:55):
plants can change with small alterations of the genetics. And
it goes without saying that this sort of genetic wobble
happens in minor ways all around us. Some people have
longer arms, or stubby your fingers, or a big toe
that's shorter than the second toe, or wider hips or
broader shoulders. And although our nearest cousins, the chimpanzees, are
(15:19):
nearly genetically identical to us, they have a lot of
differences in their body plan. For starters, their bicep muscle
has a higher insertion point, and their hips are turned
more outward, and their toes are much longer. Now, the
point is that the chimpanzee brain, with its mere ninety
(15:39):
thousand genes, doesn't have to be reinvented to figure out
how to drive a chimpanzee body to swing in trees
and to walk on knuckles. And by the same token,
the human brain doesn't have to be reinvented to figure
out how to play pickleball or dance hip hop. In
both cases, the brain just figures out how to best
(16:02):
drive the machinery that it has. So to understand the
power of this principle, consider Matt Stutsman. This is a
(16:26):
guy who is born without arms. He found himself really
attracted to archery, so he learns to manipulate a bow
and arrow with his feet. What he does is notch
the arrow into the string with his toes. Then he
lifts the bow with his right foot, and he's got
a strap around his neck which connects the bow to
(16:48):
his shoulder, and that allows him to position it at
eye level. And then he puts tension on the bow
by pushing it forward with his foot, and when his
aim is on target, he lets the arrow fly. Now,
the thing is that Matt is not simply talented at archery.
He is the best in the world. As of this podcast,
he holds the record for the longest accurate shot in archery.
(17:13):
And that's probably not what his doctors would have predicted
for a baby who came out of the womb without arms,
But perhaps they didn't realize how readily his brain would
adapt its resources to solve problems in the outside world.
Now we see this sort of flexibility everywhere in the
animal kingdom. Consider this incredible dog whose name is Faith,
(17:37):
who was born without front legs, and she grew from
puppyhood to be able to walk on her two hind
legs bipetally the way that a human walks. You can
find YouTube videos of her walking around. It's totally amazing
to watch. And although we might have guessed that dog
brains come hardwired to drive standard dog bodies, Faith shows
(18:02):
us how readily brains will move around the world with
whatever machinery they find themselves in. So what we see
from Matt or from Faith the Dog is that brains
are not predefined for particular bodies. Instead, they adapt themselves
to move and interact and succeed in the world. And
(18:23):
this isn't simply about the body you're born in, but
about whatever opportunities might come along. So take Sir Blake,
a bulldog here in California who's mastered skateboarding. He steps
up onto the skateboard and with his front paw he
scrapes at the ground to get momentum, and at the
(18:43):
right moment, he sets his front paw onto the board
and he leans into the ride, and he shifts his
body weight to steer the board around obstacles, just like
a human wood. And when he's done, he lets the
skateboard slow down almost to a stop, and then he dismount. Now,
given the absence of wheels in the evolutionary history of dogs,
(19:05):
what this shows is the adaptability of brains to steer
new possibilities. Or take this other dog named Sugar who
took up surfboarding and is inducted into the International Surf
Dog Walk of Fame, or on second thought, forget Sugar
and just revel in the fact that there is an
(19:27):
International Surf Dog Walk of Fame, because there are lots
of dogs that do this, and we don't usually think
about studying dog brains in the context of how they
hang ten on a longboard, but you can, because all
the dog requires is the opportunity and their motor systems
will figure it out. So how do these dogs do it?
(19:51):
And what does this have to do with a baby babbling? Well,
a baby learns how to shape its mouth and breathing
to produce language. But this is not from genetics, and
it's not by studying a book or surfing Wikipedia. It's
from babbling. They listen to what's going on around them,
and they try things out, and their brain compares how
(20:15):
close their own sound was to what they're hearing from
the adults around them. And this has helped long because
they get positive reactions for some utterances and not for others.
And so there's this constant feedback loop, and that allows
babies to refine their speech to perfection in whatever language
(20:35):
is being spoken around them, whether that's English or Chinese
or Hindi or any of the seven thousand languages spoken
around the globe. In exactly the same way, the brain
learns how to steer its body by motor babbling, in
other words, babbling with its slims. Just watch a baby
(20:56):
in the crib. She bites her toes, she slaps her forehead,
she tugs on her hair, she bends her fingers, she
knocks on the bar of the crib, and so on.
And by doing this, she's learning how her motor output
corresponds to the sensory feedback she receives. And in this way,
(21:18):
she's learning to understand the language of her body, how
her outputs nap onto the next inputs. She's trying things
out and she's getting feedback, and this is how she
eventually learns how to walk and navigate food to her mouth,
and eventually swim in a pool and dangle on monkey
(21:38):
bars and master a cartwheel. She's trying things out, she's adjusting,
she's motorically babbling. And even better, we use this same
method to attach extensions to our bodies. So think about
riding a bicycle, which is a machine that our genome
presumably did not see coming to master bike riding. Have
(22:00):
to carefully balance your torso, and you change direction by
moving your arms, and you have to stop by squeezing
your hands, and this is all totally different from the
way we normally move. But despite these complexities, most five
year olds can demonstrate that the extended body plan is
(22:20):
easily added to the resume of their motor cortex. And
this isn't just limited to typical bicycles. Consider the sky
named Deston Sandlin. He's an engineer who has given this
very strange bicycle by a friend. It had this elaborate
gearing system so that if you turned the handlebars to
(22:40):
the left, the front wheel would turn to the right,
and vice versa. And so Deston was fairly sure that
this wouldn't be too difficult to master because the concept
is very straightforward. You just steer the opposite direction that
you want to go. But as it turned out, the
bicycle was just too difficult to ride because it required
(23:03):
unlearning the normal operation of a bicycle steering wheel and
training his motor cortex to master this new task was
not as simple as having a cognitive understanding. In other words,
he knew how the bicycle worked, but that didn't mean
he could do the right thing with his body. But
after some weeks he began to get the hang of it.
(23:24):
He practiced every day, and each time he'd try to move,
he would get feedback from the world, like you're falling
to the ride, or you're crashing into a trash can,
or you're swerving in front of the mail truck. And
so he used that feedback to adjust his next moves,
and after several weeks of practicing, he got pretty good
at it. And he did this the same way that
(23:47):
he learned how to ride a normal bike as a kid,
by motor babbling. And by the way, you know what
this is like If you drive and you go to
a country that has the steering wheel on the other
side of the car, if you or an American in
England or vice versa, you keep swerving the wrong way,
but you eventually get better because your visual system looks
(24:08):
at the consequences of each action and adjusts things accordingly.
It's just how Matt Stutsman learned how to shoot bows
or sugar learned how to skateboard. Motor babbling is not
only the way that babies and bicyclists learn, it's also
become a new approach in robotics. So take this starfish
robot developed by my colleague Hodd Lipson. The idea is
(24:32):
that it's a very simple robot. It's just a small
square body with four arms that stick out. The key
is lips and doesn't teach it how to use its body.
It figures itself out. The starfish tries out a move
the way that an infant might flail a limb, and
it analyzes what happens. In the robots case, it's just
(24:55):
using gyroscopes to see how the move tilted the central bot.
So if it does just a single move, that can't
tell it what its body looks like and how it
interacts with the world. But that feedback narrows the space
of possibilities, so it now has a smaller space of
hypotheses about what its body looks like. So now it
(25:17):
does the next move, and the next and so on,
and instead of choosing random movements, it chooses its next
move to do a good job distinguishing the available remaining
hypotheses so by doing this over and over, by motoric babbling,
it develops a clearer and clearer picture of its body.
(25:39):
In this way, it learns itself. You don't need a
preprogram this robot. It learns its own capabilities. And what's
wild is that if you snap off one of the
legs of this robot, it'll figure itself out again. And
it turns out that building a babbling, self exploring robot
is way more flexible than preprogramming the robot. And in
(26:02):
the animal kingdom, nature only has some tens of thousands
of genes to work with to build a creature, so
it can't possibly preprogram all of the actions that one
might do in the world. So it's only choice is
to build a system that figures itself out. Now, think
(26:22):
about the stories that we just talked about with Matt Stutsman,
the archer with no arms, or the skateboarding dog or
the surfing dog or the starfish robot. What they all
have in common is the same principle, whatever kind of
way that you can move around in the world, the
brain on the inside does not have to be redesigned.
It just recalibrates to maximize what it can do. It
(26:47):
figures out how to control whatever body it's in. A
live wired brain doesn't need to be redesigned if there's
a genetic change to the body, planet just adjusts itself.
And that is how evolution can so effectively shape animals
to fit any habitat in different environments. Animals will evolve
(27:09):
hoofs or toes or fins or forearms or trunks or
tails or talons, and Mother Nature doesn't need to reinvent
the principles of the brain or do anything extra to
make the new animal operate correctly. And you know what,
Evolution really couldn't work any other way. It couldn't operate
(27:29):
quickly enough unless body plan changes were easy to deploy
and brain changes just followed without difficulty. And this massive
flexibility is why we can so easily install ourselves into
new bodies. If you ever saw the movie Aliens from
a long time ago, you may remember this climactic deathmatch
(27:51):
that the hero Ellen Ripley has with this giant, slimy alien.
So she scrambles into this enormous robotics just like a
mech suit that allows her movements to be magnified into
these powerful metal arms and legs, and at first, she's
swinging around awkwardly, but after some practice, she's able to
(28:14):
land punches right on the alien. Now what we see
is that Ripley learns how to control her new gargantuan
body plan, and she does so thanks to her brain's
capacity to adjust her relationship between her outputs like swinging
my arm and her inputs. Wears that giant arm right now.
(28:35):
So it's not difficult to learn these kinds of new associations.
Just think about forklift drivers who are using their arms
and these little levers to control something really large, or
crane operators who are sitting in their little booth and
operating this thing that's one hundred feet high, or laparoscopic
surgeons who are controlling levers to control something that's very
(28:58):
very tiny. So all of these folks get out of
bed every morning to pilot strange new bodies. And let's
take another example. There was a very successful young man
named Jean Dominique Bobie who lived in Paris, and he
was on top of the world. He was editor in
chief at El magazine in Paris, and he revolved at
(29:21):
the top of French social circles. And one afternoon in
nineteen ninety five, without any warning, he had a massive
stroke and he instantly fell into a deep coma. So
he stayed in this coma for twenty days, and just
when everyone was giving up hope, he regained consciousness. But
(29:42):
there was a problem. It's the type of thing that
gives everyone who hears about this nightmares, which is that
he was mentally aware. He could see his surroundings, he
could understand everything everyone was saying, but he could not move.
He couldn't twitch his arm, his fingers, his face, his toes.
He couldn't speak, he couldn't cry out. He discovered that
(30:05):
his only available action was to blink his left eyelid.
Other than that, he was locked in the frozen dungeon
of his body. This is called locked in syndrome. So
luckily he had a heroic nurse with a plan. She
would sit with him and recite all of the letters
(30:26):
in the alphabet in the order of their frequency, and
he would blink his eye when she arrived at the
next letter he wanted, and in this way, one letter
at a time, he could communicate, and eventually he wrote
out an entire book called The Diving Bell in the Butterfly.
(30:46):
He died just before I was published. But this became
a huge international bestseller, in part because it allowed readers
to appreciate, probably for the first time, this simple pleasure
of having a brain that successfully drives this enormous meat robot,
and does so with such expertise that were totally unaware
(31:09):
of the massive operations running under the hood. Now here's
the question, what if we could have measured the little
electrical signals in Bobie's brain, the spikes and his neurons,
instead of having to look just at his eyeblinks. What
if we could have eaves dropped on his neural circuits
to figure out what they were trying to say to
(31:31):
the muscles, and then by passed the injury to make
something happen in the outside world. Well, a year after
Bobie's death, researchers at Emory University implanted a brain computer
interface into another locked in patient named Johnny Ray, and
Johnny Ray lived long enough to control a computer cursor
(31:53):
simply by imagining the movement. His motor cortex was unable
to get the signals through the damaged spinal cord, but
this implant could listen to the signals and then pass
along that message to the computer. Then, in two thousand
and six, a paralyzed former football player named Matt Nagel
(32:14):
was able to control lights and open an email, and
play the video game Pawn and draw a circle on
the screen. And this was all because of a four
by four millimeter grid of almost one hundred electrodes implanted
directly into his motor cortex. He would imagine moving his muscles,
which caused activity in his motor cortex, and the researchers
(32:37):
could measure that activity to at least crudely determine the intention.
The technology used with Johnny and Matt it was makeshift
and unpolished, but had proved the possibility, and by twenty eleven,
my neuroscience colleague Andrew Schwartz and his colleagues at the
University of Pittsburgh built a prosthetic arm was almost as
(33:01):
sophisticated and lie as a real arm. And a woman
named Jan Schumann had become paralyzed from a disorder called
spinocerebellar degeneration, and she volunteered herself for a neurosurgery that
would give her control of this arm. So, with the
signals recorded from her motor cortex, Jan imagines making a
(33:25):
movement with her arm, and the robotic arm moves. This
robotic arm is part way across the room, but this
makes no difference because through the bundle of wires that
attaches these electrodes in her brain to the computer and
to the robotic arm, she can make it turn and grasp,
(33:45):
essentially the way that she would have done with her
own arm years ago. Normally, when you think about moving
your arm, the signals traveled from the motor cortex down
your spinal cord, into the peripheral nerves into your muscle fibers.
With Jan, the signals recorded from the brain just take
a different root. They're going long wires connected to motors
(34:05):
instead of neurons connected to muscles. So Jan gets better
and better at using the arm, in part because of
improving technology, but also because her brain is rewiring to
understand how to best control its new limb, just as
it would with a reversed bicycle or a surfboarder Ellen
Ripley's mex suit. Jan is doing motor babbling to figure
(34:29):
out how to drive the arm smoothly, and in an interview,
by the way, Jan said, I'd so much rather have
my brain than my legs. Why did she say that.
It's because if you have the brain, you can build
a new body, but not the other way around. So
we see that brain machine interfaces can restore or replace
(34:52):
damaged limbs, But the question is could you use this
same technology to add an additional limb. So in two
thousand and eight, a monkey with two normal arms used
its thoughts to control a third arm made of metal.
This was again the work of my colleague Andrew Schwartz.
He and his team put a tiny array of electrodes
(35:15):
into the monkey's brain, and when the monkey thought about
different things, that could control the robotic arms to pluck
marshmallows and stick them in his mouth with the robotic arm.
The monkey initially trained for this by moving a cursor
on the screen towards a target, and he'd get rewarded
when he got it right. And at first, the monkey
(35:36):
would move his own arms while he was doing the task.
But something remarkable happened, which is eventually he stopped moving
his arms and the cursor continued to move on its own.
His brain was rewiring to separate out these tasks, so
some neurons corresponded to his real arms and some to
(35:58):
the cursor on screen. Eventually, these signals were able to
be used to control the robotic arm for marshmallow gathering
and sticking in his mouth, all without any physical movement
of his real arms. It had become a new limb,
a third limb. The way that the monkey learned to
(36:19):
use the robotic arm independently of its real arms recalls
docc the character from Spider Man, who controlled his robotic
limbs even while doing other tasks with his flesh hands.
So it shouldn't seem surprising that humans and monkeys can
figure out how to move robotic arms with their thoughts.
(36:41):
It's the same process by which your brain learned to
control your natural, fleshy limbs. As we've seen. Your process
as a baby was to flail your appendages around and
bite your toes in grass your crib bars and poked
(37:01):
yourself in the eye and turn yourself over. For years,
this is how you fine tuned the operation of your machinery.
Your brain sends out commands, compares those with feedback from
the world, and eventually learns the capabilities of your limbs.
So your skin covered arm is really no different from
(37:21):
the clunky, silver robotic arm of the monkey. It just
happens to be the standard operating equipment you're used to,
so you often end up blind to its amazingness. So
for both jan and the monkeys, the robotic arms were
not directly connected to their torsos, but instead connected by
(37:43):
a bundle of wires. The electrodes in their brain sent
wires to a computer which does the processing, and then
the bundle of wires goes from the computer to the
robotic arm. But increasingly this can be done wirelessly, and
that means the robotic arm that you're controlling does it
need to be right next to you or even in
the same room. So could you control a robot on
(38:06):
the other side of the world. While in two thousand
and eight, my colleague Miguel Nikolaylis and his team from
Duke University hooked up electrodes to a monkey and that
monkey controlled the walking patterns of a robot halfway across
the globe. So the monkey would walk on a treadmill,
(38:29):
and the signals from his motor cortex were recorded and
translated into zeros and ones and transmitted via the Internet
to a laboratory in Japan and fed into a robot there.
And while the monkey walked, the five foot tall, two
hundred pound robot would also walk like a metal doppelganger.
(38:49):
So after they demonstrated this proof of principle, the Duke
team stopped the treadmill. But as the monkey looked at
its avatar on the screen, it's thought about walking, and
so the robot Japan kept marching along. So in the
same way that Jan imagines movements and the arm executes
(39:11):
our internal commands, the monkeys motor cortex continued to think
about walking even while he wasn't doing it, and the
robot kept going. So in the not too distant future,
it seems inevitable that we're going to have mind controlled
robots in factories or underwater or on the surface of
(39:31):
the moon. And it's all from the comfort of our
own couches. And this is because our cortical maps, after
extensive training, will be able to incorporate whatever the limbs
of the robot are. That's going to become our tell limbs.
So think about the way we watch television, which means
(39:54):
far sight. I'm coining the term tell limbs because in
the near future, we're going to be control rolling far bodies.
(40:16):
So the bodies that we have right now have evolved
for the conditions of this particular oxygen rich planet. But
leveraging the brain's plasticity to build long distance bodies, that's
surely going to be our main strategy for space exploration.
(40:37):
So what consequence would expanding your body, say with a
robotic arm or a metal avatar across town. What consequence
would this have for your conscious experience? The answer is
that the robot will be perceived as a part of you.
The robot will just be another limb. Now, it's an
(40:58):
unusual limb because of the physical gap between you and it,
but it nonetheless will qualify just as a new limb.
The only reason we're accustomed to connected limbs is that
Mother Nature is a talented seamstress with muscle and sinew
and nerves, but she never worked out how to control
(41:19):
distant limbs via bluetooth. Now, if extra limbs or telelimbs,
if the seems exotic, recall that you have everyday experience
with them. Just look in a mirror and move your arm.
You see a distant object, move in perfect synchrony with
your motor commands. And although babies are at first confused
(41:42):
by mirror images, they come to understand the reflections as themselves,
because although they don't feel any direct sensation from those
distant limbs, they can witness their control over them, and
that's enough for these limbs to be annexed by self hood.
So this notion of this self is analogous to the
(42:04):
borg in Star Trek, who assimilate everything in their path
into their singular identity, except for those things that can't control,
like the impossibly unpredictable Captain Picard. Now this led me
to propose an axiom in Live Wired about the nature
of selfhood. What the body can control becomes the self.
(42:30):
And I think this all pivots on predictability. In other words,
can I predict that signals from my brain will cause
something to happen out there? So this relationship of selfhood
and predictability it allows us to understand disorders such as
asmatic noosa, which translates to not knowing one's body. So
(42:52):
in asmatic noosa, damage to the right pridal lobe of
the brain, say by a stroke or a tumor, means
that a person is no longer able to control a limb,
and as a completely gobsmacking result, the patient will deny
that the limb belongs to her, and sometimes will insist
(43:13):
that the limb belongs to someone else. She will attribute
the arm to a dead friend or a relative, or
a phantasm or a devil, or one of the medical
professionals taking care of her. She'll say that it's not
her arm. She'll explain that her own real arm was
(43:33):
stolen or is simply missing. The manifestations of this can
be varied and strange, So a patient may feel totally
indifferent towards her no longer self limb, or she might
be delusional about it and come up with strange fabrications
to explain what happened, such as saying someone's so this
(43:56):
onto my body, or other patients might sympathetically describe their
limbs as something that they dislike, like a deadweight. And
in a more vicious version of this breakdown of selfhood,
a patient may hate her alien limb, and she might
curse at it and hit it. So there's no gold
(44:17):
standard for this disorder, but you probably have no trouble
guessing my proposal in Live Wired, which is the brain
can no longer control the limb, and so the limb
falls from the brotherhood of the self. It no longer
is part of you. Now. Sometimes these patients will have
a small window of lucidity in which they re recognize
(44:40):
their limb as their own, but it doesn't last long,
And I hypothesize that this may result when the arm
happens to behave like they intended. So it's accidental predictability.
Given a person's lifelong experience of controlling her arm, it
doesn't come as a surprise that even a temporary impression
of control can snap it back into alignment with this self,
(45:04):
if only for a moment. Now, by the way, I
suspect this sense of predictability is related to the way
that a person that you know deeply, like a family member,
becomes something like a part of yourself. Of course, humans
are way too complex to predict perfectly, and the degree
to which your spouse acts surprisingly is the extent to
(45:28):
which he or she remains independent. Okay, Now, one doesn't
need prosthetics or brain surgery to try out new bodies.
The developing field of avatar robotics allows the user to
control a robot at a distance, seeing what it sees
and feeling what it feels. So take something called the
(45:50):
shadow hand, which is one of the most intricate artificial
hands in existence. Each fingertip is equipped with sensors which
feed their data back into haptic gloves that are worn
by the user, So sending data over the internet, one
can control a robotic hand. In London from Silicon Valley
(46:12):
and other groups are working on disaster recovery avatars. These
are robots that are sent in after earthquakes or terrorist
attacks or fires, and the ideas that they can be
piloted by drivers that are sitting somewhere else that's safe. Now,
I haven't yet heard of people using strange bodied avatars,
(46:33):
but they certainly could. Just as the brain learns skis
or trampolines or pogo sticks, it can learn to become
one with a weird and wonderful avatar body. So this
field of avatar robotics is going to allow people to
try out extended or strange bodies. But let's note that
(46:54):
it's super expensive and luckily there's a better way to
try out different body plans, and that's inside virtual reality.
So inside a simulated space, you can make massive changes
to your body plan instantly, inexpensively. So imagine looking into
a mirror in your VR world, you lift your arm,
(47:17):
and you see your virtual avatar in the mirror, raise
its arm, you tilt your neck in the avatar tilts
its neck. Now, imagine that this avatar has not your face,
but that of an Ethiopian woman, or a Norwegian man,
or a Pakistani boy, or a Korean grandmother. So, for
(47:37):
the reasons that we just saw about how the brain
determines selfhood, if I can control what it does, it
becomes me. It only takes a few moments of motor
babbling in front of this VR mirror to convince yourself
that you now inhabit a different body. You can then
walk around in the VR world as a different in person,
(48:00):
experiencing life through a modified identity. Self identity, by the way,
is surprisingly flexible. Researchers have been studying this in recent years,
how taking on the face of a different person can
enhance empathy, but taking on a new face that's just
the beginning. So in the late nineteen eighties, because of
(48:22):
a coding error, the VR study of unusual bodies began.
A scientist was inhabiting the avatar of a dockworker in
VR when a programmer accidentally made his arm enormous, like
the size of a construction crane because he inserted too
many zeros into the scaling factor. And to everyone's surprise,
(48:46):
the person in VR was none less able to figure
out how he could operate accurately and efficiently with this megaarm.
And so this led people to wonder what kind of
bodies could be occupied. So my friend Jaron Lanier and
his colleague An Lasco made an experience in which people
(49:06):
inhabited the bodies of eight legged lobsters. So your two
arms controlled the first two arms of the lobster, and
then they tried out several complicated algorithms to control the
other arms. And it was pretty tough work to control
the eight legs of the lobster, but apparently some people
(49:27):
were able to make it come to pass. So Jaron
coined the term homuncular flexibility. The homunculus is the little
man inside your head, the little naps. He coined this
term homuncular flexibility to capture the surprising elasticity of the
brain's representation of its body. Some years later, my Stanford
(49:50):
colleague Jeremy Baylinson and his team set out to test
homuncular flexibility more scientifically. They asked whether people could learn
to act accurately control a third arm in VR. So
imagine strapping on the VR goggles and you grasp two
controllers in your hand, and so you can see your
(50:11):
own arms in virtual space, and you see an additional
arm as well, coming out from the middle of your chest.
The task is pretty simple. You touch a box as
soon as it changes color. But there are a lot
of boxes, and to do well you have to employ
all three arms. So the first two virtual arms are
(50:31):
simply controlled by your own arms, and the third arm
is controlled by rotating your wrists. Within three minutes, users
got it. They could accommodate the new body plan with
this third arm and do the task really well. There's
really no limit to the physiques or body plans that
you could explore. Imagine finding a virtual tail protruding from
(50:56):
your tail moan which you could accurately control with your movement,
or becoming the size of a golf ball or the
size of a building, or having six fingers, or becoming
a housefly with wings, or like doc oc, becoming an octopus.
Marrying the flexibility of the brain to the burgeoning creativity
(51:20):
of the VR design world. This is why we're moving
into an era in which our virtual identities are not
going to be limited by the bodies that we happen
to have evolved. What we can do instead is speed
up evolution from eons to hours. We can explore bodies
that Mother Nature couldn't dream of, making virtual avatars reel
(51:46):
to the brain. So let's wrap this up. We saw
with Matt the archer or Faith the dog that brains
adjust to drive whatever body they find themselves in, and
like Jam's robotic arm, brains can also figure out how
to operate new hardware additions. Massive networks of brain cells
(52:11):
pull off this trick by putting out motor commands like
lean to the left and assessing the feedback like the
skateboard tilted and wobbled, and then it adjusts its parameters
to climb the mountain of expertise. So our progeny won't
have to limit themselves to the boundaries of their bodies. Instead,
(52:33):
they're going to be able to extend across the universe
according to whatever is under their control. Imagine learning how
to control a drone as part of your body, or
build robotic wings and control them with your thoughts, just
how you control your arms and flying across the city
that way, or imagine having a sail for balancing, or
(52:56):
a propeller or peripheral devices like a forklift. How would
you build a better body than the one you inherit
it from a long road of evolution. That's all for
this week. To find out more and to share your thoughts,
head over to eagleman dot com, slash podcasts, and you
(53:18):
can also watch full episodes of Inner Cosmos on YouTube.
Subscribe to my channel so you can follow along each
week for new updates until next time. I'm David Eagleman,
and this is Inner Cosmos.
Host
David Eagleman
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