Who Will We Be? The Brain with David Eagleman

This programme contains some scenes which some viewers may find upsetting

Over the last 100,000 years, our species has been on quite a ride.

We've gone from primitive hunter-gatherers

poking around for scraps

to a world-conquering, city-dwelling,

hyper-connected super-species,

and it's all thanks to the three pounds of wet biological

material stored up here.

We live surrounded by our inventions.

We have the means to travel, to make,

to communicate, to build.

What I find incredible is that all of this was built with

the same neural material that our ancestors used to hunt

and to build primitive tools.

The genius of Mother Nature and the secret to her success

was to build a brain that could innovate,

to make the journey from primitive man to this

in a very short amount of time.

I want to explore what it is about the brain

that's made this journey possible.

If we can understand how it works,

then maybe we can direct its power in new ways

and open a new chapter in the human story.

So what's next for our brains?

What do the next 1,000 years have in store for us?

And in the far future, what is the human race going to look like?

What will we be capable of?

This is a journey into who we might become.

We'll look at how we can use our brains

to control new kinds of bodies.

ROBOT HAND BUZZES

How our sensory experience can be expanded to new horizons.

We'll look at how we might one day separate our minds

from our physical selves -

even possibly overcome death.

The human body - it's a masterpiece of complexity and beauty.

It's a symphony of 40 trillion cells all operating in concert,

and it's all orchestrated by the three-pound organ we call the brain.

Sensory information floods in.

Decisions are made.

Responses are formulated.

The brain sends out commands and the body moves into action,

but what if the brain could do more - handle more?

What if there were other ways for it to operate?

We're heading for a fundamental change in the relationship

between the body, the brain and the outside world.

We're marrying our biology with our technology

and that's poised to transform who we will be.

This is all possible thanks to a special property of the brain

called "plasticity".

It's best illustrated through a remarkable story.

Meet Cameron Mott.

In this home movie, she's four years old.

I'm a princess girl, Daddy!

A princess girl!

I'm a princess girl.

One day, Cameron suddenly started having seizures.

SHE GROANS

The really big issue was that Cameron's seizures were

drop seizures where she would fall down to the floor very quickly

and they were very aggressive.

-Cameron... Whoopsie!

-SHE SHRIEKS

She was diagnosed with Rasmussen syndrome,

an inflammatory disease that attacks the brain.

It causes paralysis and ultimately death.

To save Cameron's life,

her physicians proposed a radical solution.

They would remove the diseased part of her brain.

Blow harder.

'The procedure itself is probably the most drastic surgical procedure

'that can be done in neurosurgery.'

You know, it's not a simple operation.

There are... On a scale of one to ten,

ten being one of the more difficult operations

that we would typically perform in neurosurgery,

I'd say it's a ten.

Seeing no other option, Cameron's parents consented.

The real risk in the surgery is not

what happens if we do the surgery.

The question is,

what happens to this person if we don't do the surgery?

MACHINE BEEPS

The issue was that an entire half of Cameron's brain had been affected.

Our biggest concern was, would she survive?

Would there be some complication?

Would we go through all of this and then still have seizures at the end?

This is Cameron's preoperative scan.

This is the material that underpins her intellect and her emotion,

and her sense of humour - who she is.

In this scan, the empty space

is where half of her brain has been removed.

No-one could be sure how the loss of that much brain tissue

would affect Cameron.

What would she lose?

Could she be like other children?

This is Cameron seven years on.

She's seizure-free,

and more importantly, beyond a slight weakness on one side,

she betrays no sign of the ordeal that she went through.

I like to run a lot and do different types of stuff outside.

I love math.

Give me... Give me three quizzes to do and I'll do it.

OK, let it go.

Just imagine taking your laptop

and tearing out half the motherboard and expecting it to still function.

It would never work with a computer but it can work with a young brain,

and that has dramatic implications.

We used to think of the brain as a fixed system, with different parts

dedicated to specific jobs like seeing or deciding and moving,

but no region works in isolation.

The brain is a vast, dynamic, interconnected network

that's always changing.

Instead of hard-wired, I like to think of the brain as live-wired,

and that flexibility of the brain opens up new possibilities

for our future.

It could be argued that this future has been with us

since the 1970s, in the form of a simple piece of technology.

This is a cochlear implant and it can give hearing to deaf people.

MACHINE BUZZES It picks up sounds

and converts them to electrical signals

that plug directly into the cells of the inner ear.

Now, when it was first introduced,

researchers didn't think it was going to work,

because biology is wired up with such precision and specificity,

and this just takes crude signals and shoves them into the brain,

in a way that the brain's not expecting.

The cochlear implant represents a marriage between metal electrodes

and biological cells, and yet, it works.

Around the world, almost 750,000 people have had the chance to

hear for the first time, thanks to these implants.

Wow.

Here's how.

Whether it comes from your ears or your eyes

or a touch on your skin...

..all the information that enters your brain is converted into

the same stuff - electrochemical signals.

These are the common currency of the brain.

When the implant produces these signals, however crudely,

the brain finds a way to make sense of them.

It hunts for patterns... BUZZING AND CRACKLING

..cross-referencing with other senses.

TRAFFIC RUMBLES

At first, the signals are unintelligible,

but soon, meaning emerges. BELL RINGS

Cochlear implants reveal something amazing about the brain,

which is whatever signals you feed into it, the brain will figure out

how to extract something useful out of that.

As long as the data coming in has a structure that maps onto

the outside world, the brain will figure out how to decode it,

and this turns out to be one of nature's greatest tricks.

And now that we know about it, it opens up a world of possibilities.

Why restrict ourselves to trying to replace lost or damaged senses?

There must be ways for us

to enhance or add to the senses that we already have.

In my laboratory, we've created this vest.

It turns sound into patterns of vibration

that are felt on the skin of the torso.

'The idea is that, given enough time,

'the wearer's brain will learn to

'automatically decode these vibrations.

'They'll instinctively feel and understand information.'

This is the alien language game, so you're going to feel a word

presented to you as a pattern of vibration on your torso.

Through time, you're going to get better and better at this,

as your brain starts decoding how these inputs

map onto words that you know,

and your job is just to figure out what the language of the vest is.

I can feel the vibrations on my body. It makes no sense to me.

They're just random.

I'm aware that may be one on the left shoulder

or right shoulder or lower back...

BELL RINGS

One of my lab members, Joshua, wore the vest as he went about his day.

An app sends a pattern of vibrations to his torso.

He guesses what word that pattern represents

and he's told whether he's right or wrong.

'For the first week or so, I mean, it was just total nonsense,

'to try to figure out which word was just projected onto me,

'but as time has gone by, I am able to,'

through some process, distinguish them.

It seems strange that you could understand information

through your torso, but that's the surprise -

it doesn't matter how signals find their way to the brain.

We have these peripheral senses that we plug in,

but here's the thing - our eyes, our nose, our mouth -

these are just what we inherit from our evolutionary past.

It's what we come to the table with, but we don't have to stick with it,

because it might be possible

that we could plug some sensory channel into an unusual port

into the brain and the brain will just figure it out,

and it may be that, in the near future,

we can invent new sorts of sensory devices

and plug them directly into the brain.

In theory, there's no limit to the new sensory expansion

that we can create.

So, just imagine if we could feed in an input of real-time weather data,

so you could feel if it's raining 100 miles away

or if it's going to snow tomorrow.

THUNDER RUMBLES Or imagine feeding in

real-time stock data and developing an intuitive sense

of how the markets were moving.

You'd be plugged in to the global economy.

Because of the brain's capacity to take on new inputs,

we should be able to expand the experience of being human.

We could enjoy things that wouldn't be possible with

the traditional senses we arrive with.

It may be that the evolution of our technology, rather than our

biology, is what guides the journey of our species from here on out.

As we move into the future,

we'll increasingly design our own portals on the world

and, as far as we can tell, there's no limit

in what the brain can incorporate.

Instead, we now have the tools to shape our own sensory experiences -

to widen our small windows on reality.

Now, how we sense the world - that's only half the story.

The other half is how we interact with it.

What if we could use the brain's flexibility to

change our physical bodies?

This is Jan Scheuermann.

Because of a rare genetic disease, the spinal-cord nerves that

connect her brain to her muscles have deteriorated.

I can't move anything below my neck.

Though the stem of my brain meets my spinal-cord,

there's some deterioration there,

then the signals aren't getting through

so my brain is saying, "Lift up," to my arm,

and my arm is saying, "I can't hear you!"

Now Jan is participating in a trailblazing experiment -

part neurosurgery, part robotics.

Two electrode arrays implanted into her brain provide

a link from her motor cortex to this -

the world's most advanced robotic arm.

ROBOTIC ARM BUZZES AND HUMS

OK. Up. Down.

Its fingers can curl and uncurl.

It can roll.

The wrist can flex.

Jan can control it just by thinking about it.

Right...

and grasp.

Though she speaks the commands out loud, she has no need to.

-Back to me.

-There's a direct physical link

between the arm and her brain.

Down.

An arm normally moves

because of a storm of activity in the motor cortex.

From there, the signals travel down the spinal-cord to

the muscles of the arm.

In Jan's case, electrodes eavesdrop on the cortical signals directly

and redirect those to Hector, her new arm.

Like riding a bicycle,

the brain doesn't forget how to move the arm,

even though it hasn't moved in ten years.

With practice, this relationship will become fully unconscious.

She'll be able to move Hector automatically

without thinking about it,

just as we do with our biological limbs.

Oh, it feels very good to be able to shake hands

and fist-bump and interact.

It's so very life-affirming to me,

to be able to reach out and touch a person.

Jan's experience points to a future in which

we use technology to enhance and extend our bodies,

not only replacing limbs or organs but improving them,

elevating them, from human fragility to indestructibility.

Hollywood has often imagined a person who is part machine -

well, that fantasy is fast becoming real.

ARM BUZZES

As we learn how to take on new sensory experiences

and control new kinds of bodies,

that's going to profoundly change who we are as individuals,

and that's because our physicality sets the tone

for how we feel and how we think, and who we are.

At this moment in history, it may be that we have more in common with our

Stone Age ancestors than we do with our descendants in the near future.

We're already beginning to extend the human body, but no matter how

much we enhance ourselves, there's something we need to keep in mind.

Our body is made of flesh and bones.

It's going to deteriorate and die,

but what if the study of the brain could address our mortality?

What if, in the future, we didn't have to die?

There will come a moment

when all of your neural activity will come to a halt

and then the glorious experience of being conscious will come to an end,

and it doesn't matter who you know or what you do,

it's the fate of all of us.

It's the fate of all life,

but only humans are so unusually intelligent

that we suffer over this.

'When someone dies, those who are left grieve.

'They mourn the lost relationship

'but, with every death, there's another loss.

'Every brain contains a lifetime of information,

'experiences, knowledge, wisdom.

'At the moment of death, all that becomes lost.'

Francis Crick was one of the discoverers of the structure of DNA.

And he was also a friend and a mentor to me.

And when he died,

I remembered thinking about what a waste it was

that he was cremated and this brain of one of the greats

of 20th-century biology was going up in flames.

Because, even after a person dies, there's a lot of information

about them stored in the physical structure of their brain.

And we are reaching a point in neuroscience where it becomes

a possibility that we could preserve a brain

and read out the information and live with that person again.

Brain preservation is a new field.

It's controversial and its promise is still unproven.

Nonetheless, some people are actively exploring the possibility.

Here in the Arizona desert,

the researchers at the Alcor Life Extension Foundation

believe they can give the dead a chance to live again.

This facility holds the remains of over 100 people

preserved at ultra-low temperature.

It's run by Max More, who describes himself as a futurologist.

As soon as legal death has been declared, which is really not

biological death, but we have to wait for that point legally,

we can then move the patient from the bed into the ice bath,

we can add external ice on top, we restart respiration...

we restart circulation by doing essentially mechanical CPR

and then we also administer 16 different medications to try

and protect the cells as we cool down.

Each body is submerged in liquid nitrogen,

bringing its temperature below -300 degrees.

This process is known as cryonic suspension

and it doesn't require a whole body.

Sometimes a client chooses to preserve only their head and brain.

So what we will do is we'll do the neuro separation

somewhere down here, a few vertebras down.

We'll move the patient's cephalon into the cephalon ring

where the head is essentially upside down

so we can access the carotids and, just like the whole body procedure,

except there we go through the chest, here we are washing out

the blood and body fluids from the brain.

The idea is to perfectly preserve a body into the distant future,

with the hope that an advanced technology not yet invented

will allow for thawing and reanimation.

So, Max, tell me about these dewars.

Well, our patients are stored in these.

We call this a bigfoot dewar. It contains four whole body patients.

So, as you can see from this 3-D printed model,

each of those goes in an aluminium pod that gives extra protection

and we also get five neuro patients in the centre column.

So these fill up with about 450 gallons of liquid nitrogen.

They're not sealed, we just have a polystyrene cap floating on the top

and we top these up once a week with liquid nitrogen to keep them full.

-So there are nine people in here?

-Not in every one.

It depends on how many neuro patients we have.

There's actually room for more neuro patients.

So some of them have neuro patients, others don't,

so between four and nine.

Alcor began 50 years ago.

Currently, it houses 129 frozen residents...

and that number continues to grow.

Some of the pictures say,

"First Life Cycle, 1927-1996."

Do you see it as being a second life cycle?

What we're doing is we're really just giving people

another chance at life. Just as if today you're in your 30s or 40s,

had a heart attack and we did some experimental surgery

and brought you back, you might have several decades more.

But we're talking something a little bit more radical.

We're talking not just another 80 years,

but potentially thousands of years, maybe longer.

The people in these dewars have taken a leap of faith

into an unknown future.

There's no guarantee that the technology will ever

come along that allows them to wake up again.

So perhaps there are other ways to access the information

stored in a brain -

not by bringing a deceased person back to life,

but by finding a way to read out the data directly.

This is both a promising idea and a monumental challenge.

At the Department of Brain and Cognitive Sciences at MIT,

Sebastian Seung is among one of the first pioneers of that process.

He's attempting to map out the innumerable connections that

underlie a brain's function.

That unimaginably vast network of pathways

and links is called the connectome.

Your connectome is unique.

It's one of the deepest theories in neuroscience

that your memories are stored in your unique pattern of connections.

I like to think of it as a theory of personal identity -

what makes you you.

The average human brain has 86 billion neurons

and thousands of trillions of synaptic connections.

When the connectome is fully worked out,

it will be the most complex wiring diagram ever created.

It's very difficult to map out conductivity inside the brain.

There's only one technology right now which promises to give us

all the connections from a single piece of brain

and that's called serial electron microscopy.

Seung is beginning by mapping a mouse brain.

The process starts with taking a piece of brain tissue

and slicing it.

It's a hi-tech deli slicer for cutting very thin slices of brain.

To cut really thin, you have to have a very sharp knife.

This is the world's sharpest knife, a diamond knife,

whose blade is honed to atomic sharpness.

You can see a metal part which is moving up and down,

a piece of the brain is mounted on it

and the brain is being moved back and forth against a blade.

So slice after slice of brain are floating onto the surface

of the water - each slice pushes the previous slice of forward.

In order to see this cutting process,

a microscope is mounted on top of the ultra-microtome and it projects

an image onto this computer screen where we see the cutting happening.

This conveyor belt produces a tape, a very long tape, which is

kind of like a movie, every frame of which is a slice of brain.

Once the brain has been arranged in these film-like strips,

each sample is subdivided into tiny areas,

which are then scanned by a powerful electron microscope.

That process produces this,

a segment of the brain magnified 100,000 times.

At this resolution, it's possible to see almost every feature.

These small black dots are DNA inside an individual cell.

The next step is to compile these images.

By stacking them in the thousands, one on top of each other,

and then tracking the neurons through each image,

it's possible to reconstruct the exact way that the neurons

are connected, a three-dimensional model of the conductivity.

It should be possible to do this with a whole human brain someday.

The result would be a map of all the wiring that underpins

a person's thoughts, experiences and beliefs.

There's just one issue.

If you image an entire human brain with this resolution,

it would be a zettabyte of information.

Sounds like a dirty word, a zettabyte.

You've never heard it before, it's never spoken in polite company.

Well, it's the total digital content of the world right now.

That's...how much information it would be.

It's a daunting figure.

Does it mean that the idea of reading out a human brain

will always remain beyond our reach?

Well, experience says that computing power alone shouldn't be

a barrier for too much longer.

There is a common observation in computing called Moore's law.

It states that processing power doubles every two years.

If that doesn't sound like much, think of it this way.

It means that computers today are one million times more powerful

than they were in the 1970s.

Just 20 years ago, this supercomputer behind me

was equivalent to all the computing power on the planet.

20 years from now, it will probably be considered a modest force

of the type you might shrink down and wear on your body.

We're in an era now where we are developing technologies that

can store unimaginable amounts of data and run gargantuan simulations

and this is where our biology is on a crash course with our technology.

So let's say the time will come when computer power isn't an issue.

That opens up a new realm of possibility.

Suppose we could make a digital copy of the brain.

Then, not only could we read it out, we could make it run.

In the same way that computer software can run on different

hardware, it may be that the software of the mind can

run on other platforms.

In other words, what if there's nothing special

about the biological neurons themselves,

and instead it's only how they connect and interact

that makes a person who they are?

If that proved to be correct, it would follow

that we can exist digitally by running ourselves as a simulation.

And this is what is known as the computational hypothesis

of the brain.

The idea is that the wet biological gushy stuff

isn't the important part.

What matters are the computations that are running on top.

The idea is that the mind is not what the brain is,

it's what the brain does.

In theory, you might swap cells for circuits, oxygen for electricity.

The medium doesn't matter, provided all the pieces

and parts are connecting and interacting in the same way.

All your thoughts, emotions, memories,

your whole personality would still emerge.

There'd be no biological brain,

but there'd still be a fully functioning version of you.

This sounds like science fiction,

but a team in Switzerland has begun an exceptionally ambitious

project that takes the first steps down this path.

They're attempting to build a full working simulation of a brain.

It's called the Blue Brain Project.

Sean Hill is one of the members of the team.

What is the long-term goal here?

To deliver by 2023 a software and hardware infrastructure

capable of running a whole human brain simulation.

If we want to move towards being able to simulate an entire

human brain, how do we know what are the important things to capture,

the structure of the cells all the way down to the proteins,

the molecules, how do we know?

We're working at sub-cellular, we're working at cellular,

we're working at micro circuit,

we're working at brain regions, the meso circuits,

and then we have whole brain but for very simplified neurons.

So our goal is to get to whole brain

but with the very detailed neurons.

As a starting point, they're looking at rat brains.

They take tiny slices of brain and subject them

to minute jolts of electrical current.

That mimics the activity of the living brain

and prompts the cells to interact.

Each interaction is recreated on the project's supercomputer

and then integrated into a larger model with

data from hundreds of other labs around the world.

The result is this electrical storm.

This is the best approximation of what a very tiny fraction

of your brain is doing when you're, say, just staring into space.

The total activity in your brain is hundreds of millions times

more than what you're seeing here.

And this typhoon of activity

is roaring along every second of your life.

We're not building abstract models.

We're actually taking data from laboratories,

we're extracting probabilities, we're extracting distributions

from that to build a much larger model

that is based on biological data.

Not based on the assumption of how biology works,

but actually on data that comes out of a bio laboratory.

The Blue Brain Team hopes to achieve their goal by 2023 -

a full working simulation of a human brain.

And that raises a question.

What will the finished product be?

Will it be a mind? Will it think, will it be self-aware?

If the answer is yes and a mind can live in a computer,

then do we have to copy nature's biological blueprints

or might it be possible to program a different kind of intelligence,

one of our own invention?

People have been trying for a long time to create machines that think.

This field, called artificial intelligence, has been

around since at least the 1950s.

The problem has turned out to be unexpectedly difficult,

and this speaks to the extraordinary enigma of

how the brain does what it does.

Because while we'll soon have cars that drive themselves

and it's almost two decades since a computer first beat

a chess grandmaster,

the goal of a truly sentient machine still waits to be achieved.

One of the latest attempts to create an artificial intelligence

can be found at the University of Plymouth in England.

It's called iCub.

It's a humanoid robot and it's designed to learn as a child learns.

Traditionally, robots are pre-programmed with everything

they need to know.

But what if you could create a robot by developing it

the way a human infant grows?

ICub is about the size of a two-year-old.

It has eyes and ears and touch sensors

and these allow it to interact with the world and learn from it.

Babies don't come into the world knowing how to speak and walk,

but they come with curiosity and they pay attention and they imitate.

They use the world that they're in as a textbook

so they can learn by example.

So what if you wanted to create a robot to do the same thing?

Well, you would take a crude brain simulation and you'd give it

a mechanical body so that it could interact with the world.

-Hello.

-Hello, I'm iCub.

This is a red ball.

It's a red ball.

This is a yellow cup.

Yellow cup.

The aim is that, with each interaction,

the robot continually adds to its base of knowledge.

It's making connections

and building a repertoire of appropriate responses.

And, because it looks and sounds a bit like a human,

it's easy to be convinced that it thinks like one.

Where is the yellow cup?

Where is the red ball?

Often, iCub gets it wrong - that's part of the process.

-What is this?

-I'm sorry, I don't know what this is.

But the more it gets it wrong,

the more you get the sense there's no real mind behind the program.

What is this?

I'm sorry, I don't know what this is.

What becomes clear is that iCub is purely mechanical.

You can feel that it's run by lines of code,

instead of trains of thought.

So, it can say "red ball",

but does it really experience redness or the concept of roundness?

Do computers do just what they're programmed to do,

or can it ever really have internal experience?

In the 1980s, the philosopher John Searle was chewing on this problem,

and he came up with a thought experiment

that gets right at the heart of it, and he called this the Chinese Room.

'The experiment goes like this.

'I am locked in a room.

'Outside, there is someone who only communicates in Chinese.

'She writes out some questions,

'and then posts those to me in the room.'

Now, I don't speak Chinese.

But I do have these books. And they give me instructions

on exactly what to do with these symbols.

So, I look in the book and, if I can find a match to the symbols,

then the book tells me exactly how to respond.

So, I can look up this response.

That matches, so, now,

I can post this as the reply to the message I received.

'When our Chinese speaker receives the message,

'it makes perfect sense to her.

'As far as she's concerned,

'we're having a conversation in her language.'

Just by following a set of instructions,

I can convince somebody on the outside that I speak Chinese.

And, if I have a large enough set of response books,

I can have a conversation about anything.

But, here's the important part.

I, the operator, do not understand Chinese.

I can manipulate symbols all day long.

But none of it has any meaning to me.

'The argument goes that this is just what happens inside a computer.

'No matter how sentient it seems,

'the computer is only ever following instructions.

'Manipulating symbols.'

Now, not everybody agrees with this interpretation of the Chinese Room.

Some people point out that,

although the operator doesn't understand Chinese,

the system as a whole, the operator plus the books,

does understand Chinese.

Whatever the correct interpretation, the important thing is this.

It exposes the difficulty and the mystery

of how physical pieces and parts ever come to equal

our experience of being alive in the world.

With every attempt to simulate or create subjective experience,

we are confronted with one of the greatest mysteries of neuroscience.

Every brain cell is just a cell.

Running its basic operations, following its local rules,

how do billions of these add up to the feeling of me?

'If we want to see how simple parts can give rise to something bigger,

'one can look to the natural world.'

The Houston Zoo is home to a large colony of leafcutter ants.

Individually, each ant behaves simplistically.

But, when these ants work together, the colony is like a super organism

that accomplishes something much greater.

All of these ants have a different job.

There are some that are really, really good at just cutting leaves.

Others that are good at carrying leaves.

And then others that do other functions within the group.

They're independent, but they all work towards a common cause.

So, they are all coming out, doing what their job is to do,

for the good of the whole colony.

So, do these ants communicate by chemical signalling?

Yes, they do. Whenever they find something that is

a great leaf for them to cut, or fruit or vegetables,

when one ant goes and finds that, they will relay that signal,

and then the rest will just follow.

It becomes a very straight line, instead of them branching out,

going different directions, to get to the same thing.

They all follow the chemical signal.

So, what happens if one of these ants is just off by himself?

If we were to get this guy, this is a bigger ant here.

-Yeah, poor guy, he's just running...

-Going around in circles.

..and spinning in circles, yeah.

He's not getting that signal, that chemical signal back

that you are going in the right directions.

This ant can't function outside the network of local signals

because he needs those to tell him what to do.

Put him back into the network

and he does just what's needed to serve the greater purpose.

The scout ants only worry about where to find the best plants.

The leafcutters do the cutting.

The carriers know which parts to bring back to the nest.

And there, inside, other ants build, tend, harvest, mate.

It's an entire system regulated by local signalling between them.

In all of this, no one ant sees the big picture

about the agricultural society they have created.

And it doesn't matter.

The power of the colony emerges

from the local interactions between the ants.

Put enough ants together and, bang, you get a super organism

with sophisticated properties that don't belong to any of the parts.

And this is the concept of emergent properties.

Put enough simple units together,

and have them interact in the right ways, and something larger emerges.

The idea is that something like this happens in the brain.

A neuron has certain properties.

It can gather chemical and electrical signals,

and spit out signals to other neurons.

But, fundamentally, it's a cell,

like trillions of others in the human body.

It spends its life embedded in a network of other cells

and, whatever its function, all it does is react to local signals.

Just like the ant,

a brain cell spends its life running its local programmes.

But, get enough brain cells together,

interacting in the right ways, and the mind emerges.

The concept of emergent properties offers a possible way to understand

how the vast neural populations of the brain

might produce consciousness.

And it gives rise to a question.

Could consciousness emerge

from anything that has lots of interacting parts?

Could a city be conscious?

Or maybe it's not enough to have lots of simple pieces interacting.

Maybe the parts need to interact in very specific ways.

If that's true, then we might expect to find particular signatures

of activity in networks that are conscious.

At the University Of Wisconsin,

Giulio Tononi and his team are hunting for those signatures.

They're focusing on the transition to consciousness

that happens in the brain every single day when we wake up.

When you wake up in the morning, from a dreamless sleep,

before, there was absolutely nothing, and then you are awake

and, in the space of a few seconds, there is everything.

Colours, sounds, people, thoughts, desires, plans for the day.

And, of course, the world around you.

That is consciousness.

Tononi's experiments use TMS, transcranial magnetic stimulation,

to make small, targeted disruptions in brain activity.

And they can do this while a person is awake, or asleep.

In the awake brain,

an electrical pulse moves outwards across the cortex,

like ripples on a pond.

But, in the sleeping brain, only nearby areas react.

The ripples hardly spread.

When you fall into a dreamless sleep,

somehow, the neurons are not able to talk to each other.

What we activate with TMS remains very local,

it remains there, it doesn't travel any more.

That spread of activity across the waking brain

may be a clue to consciousness.

While different regions of the brain are invested in different tasks,

consciousness seems to have something to do with

integrating activity across vast brain territories,

linking areas to produce a single, unified experience.

You don't have an experience split in two pieces.

When I see your shirt,

I don't see a shape and the colour separated from each other.

They are together, they are bound together.

So, every experience is one.

'Every moment of experience is a composite

'created from innumerable possibilities.

'I might be feeling the heat of the day.

'I might be remembering an event from high school.

'My stomach might be digesting lunch. I'm also seeing, I'm hearing.

'My brain will create my sense of self

'from all these different strands.

'How the strands are woven together is still a mystery.'

But Tononi believes that the key to consciousness

is contained in these patterns of interaction.

He also believes that this key

doesn't have to belong only to biological creatures.

That definitely is how it evolved.

And it takes an organisation of that kind to do it.

It just needs to be made the right way.

Building consciousness on another medium

is still squarely in the realm of speculation.

It could turn out that there is something special about neurons

so that only a biological brain could produce consciousness.

Nonetheless, this idea offers us a glimpse of one possible future.

With powerful enough computers

simulating all the interactions of a human brain,

we could, one day, become non-biological beings.

And that would be the greatest leap in the history of our species.

We could leave these bodies behind.

'Digitally, you could live whatever life you wanted,

'wherever you wanted, with a kind of immortality on offer.'

While the stars are far beyond the reach of

any flesh-and-blood human lifespan,

you could be uploaded, and sent off to experience other solar systems.

Or, you could enter an existence in a simulated world.

One in which you flew.

Or lived underwater.

Or lived a life of luxury.

Maybe you could journey into a reconstructed version of the past.

When we imagine simulated life, the choices are endless.

'And they include a strange possibility

'that what we're talking about

'is something that's happening already, right now.'

The simulation could look something like this.

And it could be that we're already in it.

'Now, that idea might seem preposterous.

'But it's surprisingly difficult to disprove.'

It seems hard to imagine that all of this could be a simulation.

But we already know how easily we can be fooled.

Every night when you go to sleep, you have bizarre dreams.

And, when you're there, you believe those worlds entirely.

The fact that you can be so fooled by your dreams

is sufficient reason to question what you are experiencing right now.

The philosopher Rene Descartes wondered,

how can we ever know whether what we're experiencing is reality?

He said, how do I know I'm not just a brain in a vat

that's being stimulated in just the right ways so that I believe that

I am touching the ground, and seeing people, and hearing their voices?

And he realised there's no way to know.

'But he realised something else, that there is some "me"

'at the centre of all this, trying to figure this out.'

So, even if I am a brain in a simulation, I am thinking about it.

And, therefore, I am.

Over the course of this series,

we've discovered just how complex and remarkable the human brain is.

How reality is something constructed inside our heads.

How we are built to need others.

How so much of who we are, and what we choose to do,

is governed by factors outside our conscious minds.

Now, it seems to me that we stand at a major turning point,

one where we might take control of our own development.

We face a future of unchartered possibilities...

..in which our relationship with our own body,

our relationship with the world,

the very basic nature of who we are,

is set to be transformed.

For thousands of generations,

humans have lived the same life cycle over and over.

We're born, we control a fragile body,

we experience a limited reality, and we die.

But science and technology are giving us tools

to transcend that evolutionary story.

Our brains don't have to remain as we've inherited them.

We're capable of extending our reality, of inhabiting new bodies,

and possibly shedding our physical forms altogether.

Our species is just at the beginning of something,

and we're discovering the tools to shape our own destiny.

Who we become is up to us.