All language subtitles for brain3

Who are we?

What makes us tick?

How do our minds work?

For centuries, these questions were largely left

to philosophers and theologians.

Then, around 100 years ago,

a new science opened a window on the inner workings of the mind.

It was called experimental psychology.

In this series, I will explore the history of how this new science

revealed things about human nature that were surprising,

and often profoundly shocking.

ELECTRICAL CRACKLE

- The experiment requires that we continue...
- But he might be dead!

Ever since I was a medical student,

I have been fascinated by psychology, by its brutal history,

and by how far some researchers have been prepared to go

in the search for answers.

This time, I'm investigating how studying the abnormal brain

has shone a bright light on to the workings of the normal brain.

It got totally out of control,

he's smacking me and hitting me and pulling my hair out.

When the brain is damaged by natural causes,

or by operations that go wrong,

the bizarre symptoms that sometimes then result

are often extremely illuminating.

< Can you tell me that number?

Five. >

What we've learnt from experiments done on these unique,

unfortunate individuals, has implications for us all.

It's taught us astonishing things,

not just how the brain works, but its hidden potential.

I'm actually using it pretty much like I would use vision.

Excellent.

Angela, a 45-year-old mother, has been having epileptic fits.

- NURSE:
- One, two, three.

Her temporal lobe is damaged,

creating of electrical impulses that spread across her brain

causing frequent, uncontrollable seizures.

Drugs haven't worked, so she's opted for a more radical treatment.

We're going to take out roughly a line like...

- A line like that.
- Right.

Her surgeon, Paul Eldridge, is about to remove part of her brain.

The damage lies deep inside the brain, beneath the temporal lobe.

Paul has to open her skull and navigate

through critical regions of her brain to reach the area.

It is an extremely delicate procedure.

It should end Angela's fits, but there are significant risks.

The knowledge to make this operation possible has been hard-won.

Success relies on a detailed understanding

of what different parts of the brain do.

We all know that thoughts, ideas, beliefs,

the things that make us human, are somehow generated

within this lump of grey porridge up here in our heads.

But until relatively recently, that wasn't fully understood.

In fact, up until about 150 years ago,

we knew very little about what the human brain actually did.

MECHANICAL WHIRRING

So, how did doctors begin to put it all together?

How did they first start to map the brain?

I've come to Paris to see a very special brain,

because it kick-started the whole of modern neuroscience

and it also utterly transformed our understanding

of how our own brains work.

The brain I'm looking for should be in this room here.

Ha! Wow.

Wow...

Anatomists in the 19th century made great strides in understanding

how the key organs in the body work.

And through studying deformed and diseased specimens,

such as these at the Dupuytren Museum,

they were able to learn how our organs develop.

But by far the hardest organ to study was the brain.

Unlike other organs, you cannot guess which bits of the brain do

what simply by looking at them.

Then, in 1861, a surgeon was called to the bedside of a dying man.

His name was Leborgne, and we know relatively little about him.

Legend has it that as a young man he contracted syphilis,

rather like this unfortunate over here.

And as a result of that, he lost the power of speech,

apart from the ability to say one word, "tan".

Leborgne had gangrene in his right leg,

and local surgeon Paul Broca was asked to examine him.

Broca became intrigued by Leborgne's unusual speech impediment.

His voice box was undamaged, and he clearly understood questions,

so why could he only say "tan"?

Broca could do nothing for Leborgne.

The gangrene spread, and he died two days later.

The important thing is, Broca knew he had a unique opportunity

and he seized it with both hands.

He got out his saw, he cut open Leborgne's head,

and he extracted his brain, this brain.

This is the brain that Broca removed.

It's in pretty manky condition, but then again, it's 150 years old.

And it is fairly obvious, when you look at it, where the damage lies,

it's this region over here.

Broca was able to put two and two together.

Leborgne had suffered from a severe problem with his speech -

he could only say, "tan, tan".

There's a big chunk of his brain missing here.

Well, that suggested to Broca that this area here

must be responsible for speech.

When news of his discovery got out, Broca became extremely famous.

He modestly lent his own name to the region he'd uncovered.

It's known as "Broca's area".

Whatever caused Leborgne's unfortunate brain damage,

his life and then death

helped Paul Broca establish a important principle,

that different parts of the brain have different skills,

they do different things.

It's something called localisation.

Localisation is at the heart of our understanding

of how the brain works.

Today, scientists are still trying to work out, in ever finer detail,

exactly what different parts of the brain do.

And it is still patients with damaged brains who offer

the greatest insights.

An area that continues to fascinate is the area

that Paul Broca himself studied - language.

SHE SPEAKS IN GERMAN

Julia Sedera is fluent in German, Spanish and English.

She used to work as a management consultant.

I used to be on the phone all the time. I used to talk, talk, talk.

But then, three years ago, she had a massive stroke.

I could say absolutely nothing.

When I had to say something, I couldn't even say my...

Um, my husband's man - name, his name, I couldn't even say his name.

The only thing I knew was Sophia.

She seems to have recovered well,

but when her speech is tested at University College, London,

a very different picture emerges.

- You're going to look at the picture.
- OK.
- And tell me what it is.

Pi, pi, pe, pa, perry, pa, pike, perry, peak.

That's it.

- Pi?
- Pi, perry, pay,

pa, no.

Can you tell me anything about it?

It's hot, it's very good, in Brazil loads of people eat that a lot.

Julia is unable to name things.

You can buy them, they're called, le, be, ah, bet.

What do you do with it?

Put it in there, paper.

Envel?

- Again.
- Envelope.
- Elephone?

Envelope.

For neurologist Cathy Price,

rare cases like Julia are an invaluable opportunity

to learn more about the intricacies of speech.

It's very clear when you're speaking to her,

that she understands what is happening, what she's looking at.

Rum, brum, brum, tummel.

She's also able to generate a lot of speech that sounds very fluent.

The problem that she has is linking up.

Finding the right words to describe the meanings she's thinking of.

Jur, juri, du, jury,

jury, ah, jury.

- Are you talking about Egypt?
- Yes, that one.

- Tell me how you feel when you're doing this.
- I just...

I've no idea how to say it, I can't even think about it.

I know exactly what it is, but there is no idea what I can say,

I don't know what I should say, I just can't say it.

Unlike Broca, who could only study his patients after they died,

Cathy can look at Julia's brain

while it's processing language, to see what's gone wrong.

"Dome".

"Cow".

Looking at Julia's scan,

the first surprise is her Broca's area is completely intact.

The damage is further back in her brain.

This is a picture of the structure of Julia's brain.

We can see a dark area here, in the parietal cortex,

where the stroke has caused quite a lot of damage.

This is one of many areas of the brain

which are now known to be involved in creating speech.

The scan also shows Cathy which areas light up

when Julia tries to speak, which she can compare to a healthy brain.

The red signal shows that the undamaged Broca's area is active.

The adjacent blue area is where the damage lies.

What you can see here in the blue area

is that she's got less activation than normal.

And this fits in with her symptoms, in so far as this area here

is important for, for translating visual information into speech.

It's because this blue area is damaged

that Julia can't say "pineapple", even though she knows what it is.

But there's one other fascinating finding.

What's interesting is that this yellow area here,

in the anterior part of the temporal lobe,

and this is an area of the brain that's associated with meaning,

this area's more activated,

which suggests that she's relying more on the meaning of the word

to work out how to say it.

Julia is one of hundreds of stroke victims who are contributing

to Cathy's ambitious project to produce a detailed map

of brain areas we use for language.

We now know that there are many, many regions of the brain

that are involved in language.

We could probably label half the brain "involved in language".

And the new research is trying to break those areas down

into smaller and smaller components,

where we understand how different areas of the brain

respond in a much more precise way.

I think that's very good.

This picture of language ability spread right across the brain

helps explain Julia's partial recovery.

Although she's lost a big chunk of brain, Julia communicates

by using some of the remaining, undamaged language areas.

I can't say this and that, but I can say, "Can you help me, please?"

that way or that way, and it, like playing around what I have to say.

And I'm so much more myself again,

And I think, "I can't say all these things, so what?"

I can help with that. I can do what I think I need.

Taking off the top bit will give me...

It's an hour into Angela's operation.

Paul is carefully cutting his way through an area

called the anterior temporal lobe.

He's about a centimetre from the area that's triggering her epilepsy.

Temporal lobe down here, so that's going to be coming out.

He's picked his way through Angela's brain

without doing her serious harm, thanks to maps.

Maps based on years of painstaking experimentation.

It means Paul knows which areas are safe to pass through.

What should that bit of brain be doing?

Not much, so that if you take it out, not much seems to happen.

It's hard to believe there are bits of brain that don't do anything.

- They used to be known as the "silent areas".
- Right.

Now Paul really has an excellent idea of where he is,

he's got all this technology around him.

But in the early days of neuroscience,

they had very imprecise maps

and as a result, mistakes were made and terrible tragedies occurred.

But from those tragedies, the greatest lessons were learned.

Perhaps the most notorious example of a surgical intervention

that went horribly wrong occurred in 1953.

For a long time, the patient, Henry Molaison,

was one of psychology's most closely guarded secrets -

known only by his initials, HM.

- TAPE:
- Do you know what you did yesterday?
- No, I don't.

How about this morning?

I don't even remember that.

Can you tell me what day of the week it is?

No, I can't.

An accident when he was young triggered a chain of events

that robbed Henry of a normal life,

but helped science unravel one of the great mysteries of the mind,

how our memories work.

When he was seven years old, Henry was playing in the street.

Something caught his eye and he ran out onto the road.

He was knocked to the ground by a passing bicycle.

A trivial-sounding accident, the sort that happens all the time.

Young Henry needed a number of stitches in his head,

but seemed otherwise OK.

Yet this trivial incident would shape his entire life,

and would eventually lead to his becoming the most studied person

in the whole history of psychology.

At first, things carried on normally, Henry played with friends,

went on trips with his father.

But increasingly, he found himself having vacant periods

that he couldn't account for.

On his 16th birthday, Henry got into his parents' car

and prepared to head off to town to celebrate.

As they crossed the bridge into Hartford,

Henry's body seized up, his limbs and head jerking violently.

The childhood head injury had left a terrible legacy - epilepsy.

From then on, Henry's life was dominated by his illness.

In the 1940s, attitudes were less enlightened.

His father turned his back on him,

saying it was "shameful to have a mental in the family".

By age 27, he was having massive seizures on a weekly basis.

Something had to be done.

He was referred to a local surgeon, William Scoville,

whose chief specialities were ruptured discs and lobotomies.

A colleague of Scoville's described him as a free spirit,

unfettered by rules or regulations.

Probably not the sort of man you'd want operating on your son.

Scoville thought an area of the brain called the hippocampus

might be causing Henry's epilepsy.

Little was known about this region,

and surgeons hadn't dared penetrate that deeply into the brain.

So, on no more than a hunch,

Scoville decided to remove Henry's hippocampus and see what happened.

With Henry anaesthetised, but fully awake,

Scoville drilled into his skull, then pulled out his favourite tool.

He inserted a silver straw deep into Henry's brain

and then started to suck.

Since Henry was awake throughout, you wonder what he made of it.

By the time Scoville paused for breath,

he had sucked out the entire structure known as the hippocampus,

and some of the cells around it.

Not surprisingly, Henry emerged from the operation a changed man.

He still had his personality and his IQ,

but he could no longer form new memories.

It was like he was lost in a deep fog.

He could remember his childhood,

and up to the operation, but nothing after that.

- TAPE: Well, I possibly had an operation or something.
- Uh-huh?

- Tell me about that.
- I don't remember it.

Do you remember your doctor's name?

No, I don't.

- Does the name Doctor Scoville sound familiar?
- Yes, that does.

Tell me about Doctor Scoville.

Well, he did medical research on people.

At first, Doctor Scoville seemed unconcerned by his error.

Apparently, he went home to his wife and said,

"Guess what? I tried to cut the epilepsy out of a patient,

"and instead took his memory. What a trade!"

He admitted that the surgery had been frankly experimental,

and urged other surgeons not to repeat his dreadful mistake.

One thing Scoville did get right was he kept meticulous notes

of exactly what he had removed.

His clean surgical strike meant he had created the perfect amnesiac.

Henry's surgically altered brain was a potential gold mine

for psychologists keen to understand

exactly how it is we build memories.

For the next 50 years, Henry was visited almost daily

by a stream of eager researchers, keen to try out their ideas.

One of the last academics to come here to Henry's care home

and investigate his brain was Professor Elizabeth Kensinger,

from the Massachusetts Institute of Technology.

- Good morning. Hello.
- Good morning.

- Hello.
- Hi, it's very nice to meet you.

Do you think he minded at all, people coming in and

probing around inside his head, or asking him questions all the time?

I don't think so! Of course, he would have no idea

that people had come with him to this frequency.

We would have a natural banter and he would know what was going on.

But if there was a knock at the door,

and I had to talk to that person,

when I looked back at Henry, he no longer had any idea

of what we'd been talking about before.

Why was there so much interest in Henry?

We suddenly understood that there was a particular part of the brain,

the hippocampus and the tissues surrounding the hippocampus,

that was important, and that if you didn't have that tissue,

you weren't going to be able to record new memories

that you would have conscious access to.

Now they knew that the hippocampus was crucial for creating memories

from the events of our lives,

researchers could begin to explore the details of how it did this.

Memories require a diffuse association between many areas.

If you think about your conscious memory of having breakfast,

it'll the sight of the food, the smell, the taste of the food,

it's going to involve all of these different elements.

You need some part of the brain that can bind together elements

and have it be a representation that comes back to you

and that feels complete.

It's astonishing how much research was generated from this one man.

He generated an awful lot of research, didn't he?

There have been over 100 scientists that have worked with him,

and more than 10,000 articles that have cited studies

that have been done with him.

Everything that we know about memory

began with the study of Henry.

Down the years, every aspect of Henry's mind was examined,

from the content of his dreams to his memory for pain.

OK, so if you want to come on in here, this is a...

But a simple experiment, involving nothing more than a mirror,

was perhaps the most surprising and revealing of them all.

So what I'd like for you to do in this task

is to just look at the reflection in the mirror,

and use that to try to trace along the outline of the star

that you see there in the mirror.

OK, so a very simple task.

I'm going away, therefore I'm coming toward.

Damn! The opposite doesn't,

the opposite takes me off in that direction,

so I need to do the inverse opposite.

Now I just think, OK, I just go that way!

But you don't go that way... No, not that way.

Cor, blimey, I'm done, I'll take my hand out.

- All right.
- How long did that take?

- Not very impressive, I don't think.
- That's it.

This is pretty typical of a first trial, actually.

When Henry was given the mirror test to do, over a series of days,

he quickly became very good at it,

despite insisting each time that he had never done the test before.

This revealed that Henry's surgery

had removed his ability to form new conscious memories,

or episodic memories, but it hadn't disrupted his ability

to show learning on these types of motor tasks.

Since he had no hippocampus, remembering physical skills

must be processed in a different part of the brain.

- And this was big?
- This was huge.

Before this time, we didn't really understand

that there were different forms of memory.

Henry had unwittingly contributed to a major discovery,

that there are two types of memory.

One allows us to unconsciously remember physical skills,

like riding a bike.

The other, to consciously recall the moments of our life.

Henry died in 2008, at the grand old age of 82.

Many people came to his funeral, mostly academics.

He had transformed our understanding of memory,

but he had no idea of the part he'd played.

- TAPE:
- How long have you had trouble remembering things?

That I don't know myself.

I can't tell you, because I don't remember.

What do you think you'll do tomorrow?

- Whatever's beneficial.
- Good answer.

The story of Henry's brain didn't end with his death.

His brain was considered so important to neuroscience,

it was removed within hours of his death, and taken on a long journey.

Henry's brain ended up here in San Diego,

at a specially built facility,

thousands of miles away from where he had lived and died.

This multi-million pound brain observatory

was set up specially so scientists could continue to learn from Henry.

Henry's became the first brain to undergo an experimental procedure,

devised by Professor Jacopo Annese.

It's been shaved forensically into 2,401 micro-thin segments

and put through a chemical process to preserve every detail.

"Brain Observatory", I think I'm in the right place.

- Come in.
- Hello, there.

- Michael Mosley, how do you do?
- Jacopo.
- What a fantastic office!

- Thank you.
- I've come to see Henry's brain.

OK. It's the only brain that I keep in my office.

- OK.
- So we're going to show you some slides.

To Jacopo, these slides are not research,

they are the essence of Henry.

- It's not just a specimen, it's a person.
- Yes, he had a life.

Even calling them by name, you know, knowing who they were,

everybody here just feels very...more reverent.

- We're continuing the biography of HM, based on these images.
- Yes.

The new technique involves taking very high resolution images

of each slice of brain, which can then be examined in all dimensions.

It's brain-mapping on a micro level,

the most precise ever attempted.

The goal was to be able to navigate everywhere in the brain,

to look at single neurons.

Now, this is the resolution that we need to understand

- exactly what structures were affected by the lesion.
- OK.

This new data can be cross-referenced

to the psychological research collected on Henry over the years.

The aim is to build a complete picture of how the memory works,

right down to the level of the neuron.

- This is massively detailed.
- This is a massive amount of data too.

But you see, you can recognise individual cells.

So we're zooming in now.

You can resolve individual neurons in the cortex, individual fibres.

- You can go in the little alleyways, not just the big freeways.
- Yes.

The brain observatory is expanding,

opening its doors to other extraordinary individuals

who have been studied in life, and will now be studied in death.

They have a hugely ambitious goal,

to find physical traces in the brain of all our memories.

Do you think ultimately we'll be able to make more sense of this?

We're trying to find out if there is, indeed, like clues left behind.

Like of this conversation -

will there be something in these images in our brains.

That it's a testimony of what happened.

- That's what is fascinating to me.
- Are we getting closer to that?

It seems to me that you're getting to ever greater complexity.

We don't know what's relevant, that's the big question mark.

That's why we're trying to catalogue and to make a registry

that will catalogue every little detail in the brain.

Jacopo is carefully preserving unusual brains,

in the hope that scholars in the future

will be able to study them using technologies we cannot yet imagine.

The Latins used to say, "what's in writing stays".

So, this is what was written in the brain, and you cannot change that.

So, a story which begins with a boy being hit by a bicycle

nearly 80 years ago ends with his brain being preserved

in this building in the form of thousands of slices,

but also terabytes of data.

It is a form of immortality

that I'm sure Henry himself would never have dreamt of.

I'll check some...

It's now 90 minutes into Angela's epilepsy operation,

and Paul has succeeded in exposing the scarred area

within her temporal lobe that he wants to remove.

- This is the source of her epilepsy?
- Yeah.

So when you remove that,

what's the chance that will cure her epilepsy?

The stated figures are around...

a 70% seizure-free rate.

'Angela is fortunate.

'Paul has identified the focus of her seizures.

'When that isn't possible, a more drastic form of surgery,

'pioneered more than 60 years ago, may be called for.'

Back in the 1940s, surgeons decided to try a radical new approach.

Instead of, as with Angela, cutting out a small section of the brain,

they decided it would be a good idea to cut the corpus callosum,

the highway that connects the two hemispheres of the brain.

The effect of doing this was utterly unexpected.

- TV:
- 'Put your left hand through the screen. OK.

'I'm going to put a number in your hand now.

'He observes what happens when the housewife cannot see her hands.

'Can you tell me what that number was?

'Four?'

The corpus callosum is a band of 55 million nerve fibres

which connect the two halves of the brain and keep them in contact.

OK, Dave, I'm going to start to divide the corpus callosum.

In the new operation, surgeons slice through this superhighway,

disconnecting the two halves of the brain.

This halted the electrical activity that caused seizures.

After they had recovered from their operation,

they appeared to be normal.

Which was amazing, given the extent to which

the whole architecture of their brains had been altered.

This 12-year-old boy is doing some pretty impressive subdivision,

and his spelling isn't bad either.

But in psychology circles, they became legends.

And that is because these patients would, in time,

reveal something that to me is truly astonishing.

The two halves of our brain contain a sort of separate consciousness.

Each hemisphere is capable of its own independent action.

This sensational finding came about by accident.

A group of scientists in California recognised

the experimental potential of the split-brain patients.

As their brains had been separated, it was a unique opportunity

to find out if the different hemispheres had different abilities,

and if so, what?

To do this, they had to devise ingenious experiments

that would test each hemisphere in isolation.

Neurobiologist Roger Sperry set to work.

The results were bizarre, for the patients and for the researchers.

I remember seeing this footage nearly 30 years ago,

and being completely blown away.

Sperry's experiments made use of the fact that the right hand

is controlled by the left hemisphere, and vice versa.

- RESEARCHER:
- Put your left hand through the screen, OK.

I'm going to put a number in your hand now.

And what I want you to do is signal the answer.

So here's the first number.

So far, no great surprises.

But then the researcher asks her to name out loud

the number that she's got in her hand.

Can you tell me what that number was?

Four? >

OK. Now let me give you another number.

She gestures eight, which is the correct answer.

- Can you tell me again what the number was?
- Six?

But she says "six", which is of course completely wrong.

So what's going on?

What was happening is the numbers were put in her left hand,

which is controlled by the right hemisphere.

The right hemisphere can't speak, so the left hand communicated

with researchers by waving fingers up like that.

The left hemisphere meanwhile is completely in the dark.

It cannot see or feel what the left hand is doing, so it guesses.

Five.

This was the first proof of what people had previously suspected,

that language resides solely in the left hemisphere.

Sperry now decided to find out just what the right hemisphere could do.

So what's happening here is the left hand,

controlled by the right hemisphere, is being given a puzzle to solve.

The puzzle required rearranging blocks so they matched the picture.

And it's pretty good, it gets the puzzle solved pretty damn fast.

So now it's the turn of the other hemisphere,

and I have to say it's making a real pig's ear of it.

The left hemisphere hasn't got a clue how to solve this puzzle.

The other hand decides to come in and help.

No, never going to get there.

This is pretty convincing evidence that although the left hemisphere

may have language, the right hemisphere has spatial skills.

The discovery that the right side

is responsible for spatial awareness,

was followed up by other discoveries,

such as the fact that the right side can recognise faces.

But more than that, Sperry was convinced that, as he put it,

each hemisphere is a conscious system in its own right,

perceiving, thinking, remembering,

reasoning, willing and emoting.

In 1981, Sperry received a Nobel Prize for his work,

but in a cruel twist of fate, by then he was suffering

from a degenerative brain disease called Kuru,

probably picked up in the early days of his research splitting brains.

The split-brain experiments

had revealed the characteristics of each hemisphere.

The next question was, how did the two halves interact with each other?

Most people who have had their corpus callosum cut,

who've had the split-brain operation, are normal afterwards.

Cross them in the street and you wouldn't know anything had happened.

But in some cases, the end results are particularly dramatic.

From childhood, Karen Byrne suffered from daily epileptic seizures.

She decided that having her brain surgically split

was her best chance of a normal life.

Hello, Karen?

- Hi, how are you? Nice to meet you.
- How do you do? Nice to meet you.

I did have a little trepidation,

as to what kind of condition I was going to be in after the surgery.

I woke up and I'm telling you,

I was not the same girl I was 48 hours before that day,

that's for sure.

I was not the same person.

And I never would be again.

Surgery resolved the epilepsy, but created a new problem.

Dr O'Connor said, "Karen, what are you doing?"

I just looked at him and I said, "What are you talking about?"

He said, "Your hand's undressing you."

- And I had no idea, my hand was opening up the buttons.
- Right.

And so I'm rebuttoning them with the right hand,

and the left hand's unbuttoning them.

And he put in an emergency call through to Dr Sprung,

said, "Mike, you've got to get here right away.

"You've got to get here, we've got a problem."

- DOCTOR:
- Can you lift your hands up in the air?

How about the other hand, can you lift your left hand in the air?

Karen emerged from the operation

with a left hand that had a mind of its own.

An extremely rare condition known as alien hand syndrome.

You look almost possessed there.

Yep, that's how you do look, yes. It's terrible, it's terrible.

She was eventually discharged from hospital,

but she had to live with a wayward, wilful hand.

This hand would do one thing, and this hand would do the opposite.

So you're trying to have a cigarette...

Yes, this hand would put it out.

The phone would ring and I would answer it,

and the left hand would hit the clicker.

The thing on the phone, to hang up the phone.

It is just like an annoying five-year-old, isn't it?

Definitely. Definitely, and it got so frustrating.

And then you couldn't get mad at it, because it was you.

Karen's alien hand syndrome was caused

by a power struggle going on in her brain.

Our brains normally function smoothly,

because the analytical left hemisphere dominates,

having the final say in what actions we perform.

And this was certainly true of the bulk of the split-brain patients.

Karen was extremely unlucky. After the operation,

the right side of her brain refused to be dominated by the left,

leaving her hands in near constant conflict.

It's very strange, isn't it, the thought that all of us, within us,

have these two hemispheres,

and that they are wrestling, to some extent, for dominance.

- Yes, yes, yes.
- And that normally the left is in control,

but in your case, after the split-brain,

the right became very powerful.

Oh, defintely. It's so dominant! Oh, my gosh!

And, for a short period of time, it frightened me, it really did,

because I just didn't understand why it was fighting so hard

to have such power over the other side.

'Finally, her doctors found a medication that restrained

'her impulsive right hemisphere,

'bringing her alien hand back under her conscious control.'

If you really think about it, a lot of it is just horrific,

and yet, you know, it's also tremendously funny.

Yes, it really is. You've got to admit it!

How could you not think it's funny?

Psychiatrists are not encouraged to laugh at their patients, are they?

BOTH LAUGH

Karen, thank you, it's been an absolute pleasure.

- I appreciate everything, thank you.
- Lovely to see you.
- Thank you.

- Maybe I should shake both hands.
- Yes, I think you should!

Now see, that's the way to do it. That's the way to do it.

- Thank you, thank you.
- Thank you.

Life with two warring hemispheres would be impossible.

Scientists now believe it was the evolution of a left hemisphere

that was dominant with its human attributes of logic and language

that helped us become what we are today.

'It's now a couple of hours into Angela's surgery.

'Paul is about to remove the scarred area of her temporal lobe

'that has been triggering her seizures.'

This is the temporal lobe,

so this is giving us access to it.

- There it is.
- That is quite a big chunk of brain, isn't it?

Paul's now removed the damaged area,

and he's hopeful that she'll now make a full recovery.

The success of an operation like this, the fact that a surgeon

can take out a big chunk of brain without damaging the patient,

is dramatic proof of just how far we have come

in understanding the anatomy of the brain.

Angela, open your eyes for me? >

Hopefully, Angela will now be given a new lease of life.

There was a final discovery

that sprang from the study of damaged brains.

It turns out that the map of brain function

is not as rigid as scientists had always believed,

and that has some astonishing implications.

This new way of thinking was triggered by a personal tragedy,

one that changed our understanding of what the brain is capable of.

In 1960, a poet called Pedro Bach-y-Rita

had a massive paralysing stroke.

At the time, it was widely believed that once brain tissue is dead,

there is no real scope for recovery.

The family were told there was nothing more that could be done.

Pedro's eldest son George decided to ignore the doctor's advice.

He took his father home and began a series of exercises

to see how far he could push his recovery.

Pedro couldn't talk or walk, so George made him crawl.

The neighbours were horrified with the idea that the son

was making this elderly man crawl like a dog.

But, he started to recover,

and then George made him do tasks all around the house,

like washing up, and when he broke the plates,

he simply replaced them with metal ones.

He kept at it for three long years,

by the end of which Pedro had made an almost miraculous recovery.

He went back to work, got remarried and when he eventually died,

it was not from a stroke but from a heart attack,

following a climb up a mountain.

By that time, Pedro's younger son Paul was a neurologist.

Because his father had made such a good recovery, he assumed

the stroke must have affected a small area of his brain.

Paul took the unusual decision to go to his father's autopsy.

What he saw was a complete surprise.

Paul was absolutely stunned.

There were huge areas of damage in his father's brain.

97% of the nerves connecting the cortex to the spinal cord

had been destroyed. So how had Pedro learned to walk again?

Paul decided that his father's brain

must have learnt to reorganise itself,

replacing the dead tissue with other sections of living brain.

Pedro's example showed that with the right support,

stroke victims can sometimes make amazing recoveries.

It helped transform how stroke victims are treated.

Paul decided to dedicate his life

to trying to understand what had happened to his father's brain.

It's a concept we now call neuroplasticity.

The idea is that your brain can, given the right stimulation,

reconfigure itself, even in late adulthood.

Paul wondered just how far this concept could be pushed.

Just how flexible is the adult brain?

Can it be trained to work in completely new ways?

Many of his fellow neurologists did not believe this was possible.

Paul decided that the best way to convince his sceptical colleagues

was to build a machine that was able to demonstrate

just what he was talking about.

Paul was convinced that the blind can be taught

to harness the part of the brain that is normally devoted to vision.

They can literally learn to see,

using a completely different sense, touch.

The important point here is that the brain is able to use information

coming from the skin as if it were coming from the eyes.

He designed a chair containing a series of vibrating pins

that made contact with the backs of his blind subjects.

An image picked up by a camera was then translated into a crude outline by the vibrating pins.

OK, it's a telephone,

and the receiver is to the right.

Bach-y-Rita was something of a maverick.

His supervisor, a Nobel Prize winner,

told him to stop playing around with toys.

But Bach-y-Rita was convinced that his research would demonstrate

that the brain is far more flexible and far more plastic

than people gave it credit for.

So he ignored the well-meant advice and carried on his research,

here at the University of Wisconsin.

He died four years ago,

just as the prototype of an even more ambitious device was completed.

- This is the thing, is it?
- Yes, it is.

That's a Stephen Hawking box.

'It's called the brain port,

'and the idea is it will help the blind see using their tongues.

'I'm having a go under the instruction of Paul's protege, Aimee Arnoldussen.'

Looking very stylish.

'The lenses are blackened so I can't see anything,

'and there's a camera that translates images to a device

'that goes in my mouth.'

- This is going to go on my tongue?
- You are correct.

There are 400 electrodes,

so each of those electrodes will act like a pixel.

If you were to increase the intensity, as you do,

you see the pixilation on the tongue.

And so any pixel that's white is a strong stimulation,

any pixel that's black is no stimulation,

and then with training,

people feel the grey as medium stimulation.

I'm going to put something in front of you, to set the intensity.

You can turn the intensity down, or take it out of your mouth.

Ooh, that's very, very tickly.

- I am intensely ticklish, I should have warned you.
- I didn't know! OK.

It looks bizarre, but I'm told you can learn how to use it very fast.

It's going to go to the front of the tongue.

This is what a horizontal line feels like, OK.

It's in the field of view of the camera.

You're no longer laughing. Are you becoming accustomed to it?

- Now you know what to expect?
- Hmm.

Whatever I'm looking at now, I feel a stimulation on the left hand side,

and it's sort of going like that. Don't what I'm looking at, but...

The contrast that you felt at a diagonal

is where my shirt and my skin intersect.

So, I'm just looking at your cleavage!

I know! I was trying to say that a little bit more delicately!

- Right, OK.
- HE LAUGHS

Oh, dear, yes...

'Once I immersed myself in the task and really focused,

'I was surprised by how quickly I made progress.'

On that side it's rounded, yes, very good.

What kind of things have that kind of shape?

- A spoon.
- Very good. Why don't you touch it?

It's long and thin, and more circular at the end.

Excellent, that was impressive,

I wasn't sure you'd even get the key features, but you did.

What's happening is, it's like a torch which I'm using

to illuminate an object, you know, and feel round an object,

and then I get a general sense of its shape.

I'm using it like I would use vision, I suppose in a funny way.

Yes, that's exactly what I'm doing.

'Scanning studies have confirmed that the sensations on the tongue

'are indeed passing through to the visual cortex,

'something that wasn't previously thought possible.'

You're getting good at reaching for and grabbing the objects.

- Very good. Oh!
- HE GIGGLES

Proof of brain plasticity,

that the brain, even in adulthood, can reconfigure itself,

is turning the idea that its structure is unchanging on its head.

There is a map, but it isn't necessarily fixed.

The original thought of the brain not being plastic,

or being very fixed is an old notion.

Now that you also think that maybe the brain has capabilities

that we haven't been able to measure yet.

It responds to its environment.

It changes as a result of the experiences it gets.

- Which is rather encouraging.
- It sure is, it sure is.

In the last few decades, we have learned so much that is novel

and surprising about the workings of our own brains.

And that, in no small part,

is thanks to those individuals with damaged brains,

who played such a crucial role in the history of psychology.

They were operated and experimented on in the name of science,

and often with little personal gain.

Unusual individuals will continue to be prised and probed

but I do hope that in the future they will also benefit

from the insights they help uncover.

We owe them so much,

because it is from them that we have gleaned the knowledge

of how our own minds work.

They've opened a window into who we really are.