Between the turmoil of puberty and the decline of old age,
the human body reaches its peak.
In biological terms, as adults, we are the finished article.
Now is the time when we begin to live our life, rather than prepare for life.
There's something unique about the adult body
which has made us the most powerful animal species on Earth.
It has enabled us to rule the natural world.
It has given us the flexibility to escape the confines of our planet,
to venture out into space.
We've even managed to explore inside our own bodies.
Every day, doctors make repairs to our internal world.
So, all the triumphs of human endeavour stem from one thing.
It's the most mysterious part of the human body,
and yet it dominates the way we live our adult lives. It is the brain.
The human brain is a miracle of evolution.
It's the most complicated object in the known universe.
But to understand how it works, we really need to know
how it evolved and where it came from.
The brain of our ape-like ancestors was pretty small.
Its volume was about half a litre.
That's the size of the engine capacity of a Fiat 500,
or a modern-day chimp's brain.
The human brain is about three times bigger,
about the size of a sports car engine.
As our ancient ancestors evolved, they had to learn ever more complicated skills.
They needed bigger, better brains,
brains that would be more powerful and more adaptable.
It's difficult to get across how rapidly the human brain enlarged.
From our ape-like ancestors to the bigger-brained humans
was two and a half million years. That may seem a long time,
but in evolutionary terms, it's remarkably quick.
The human brain was increasing by the equivalent of 150,000 nerve cells
at each generation.
But in nature, there's no such thing as a free lunch. Everything has its cost,
and a bigger brain, like a bigger engine, is more expensive to run.
The human brain uses up more energy to run than any other organ in the body,
burning a whopping one fifth of the food that we consume.
This makes the head hotter than the rest of the body,
shown here by a heat-sensitive camera.
We invest so much in the brain because of its importance.
It's what makes each one of us who we are.
It's amazing to consider that I'm holding in my hands
the place where someone once felt, thought and loved.
From just looking at it, there's nothing to suggest very much ability at all.
It appears rather gruesome - wrinkled like a walnut
and with the consistency of mushroom.
For centuries, scientists have been battling to understand
what this unappealing object is all about.
The philosopher Aristotle, of ancient Greece,
believed that the brain helped regulate the body's temperature.
A runny nose was the cooling fluid leaking out of the brain.
He reasoned that since the heart beat faster when you were excited,
it must be responsible for our feelings and thoughts.
It's easy to laugh at him now,
but Aristotle was the first person to think seriously about how the human body worked.
We've come a long way since the fourth century BC.
Now we can actually see inside a living brain.
Medical scanners prove the brain is indeed where we think and feel.
When a particular area of my brain is working hard,
extra blood flows there, through my arteries, to provide energy for the active nerve cells.
The scanner can detect these changes in blood flow,
giving us a completely new window into the fascinating world of the mind.
Using this technique, we can actually watch the brain at work.
Here I'm listening to music.
Not one, but several areas light up.
This part of the brain is where we process all sounds,
and this is where we appreciate music.
Amazingly, there are even separate bits for melody...
for rhythm...
and for pitch.
But what's actually happening deep inside the brain?
It's a fascinating story, but it's complicated.
It all starts with this tree-like structure: a single brain cell or neurone.
Here is an actual neurone, magnified 10,000 times.
Neurones are the tiny building blocks of the brain.
They do something remarkable, which prompts all our thoughts.
They fire an electrical impulse.
Amazingly, we can now see one firing.
This is the first time it's been shown on television.
The electricity is bursting along the neurone at 400 kilometres an hour.
Here we're seeing it in slow motion.
Within a tiny fraction of a second, it's ready to fire again.
Your brain has a staggering 100 billion of these neurones.
Together they could generate enough electricity to illuminate a light bulb.
To make things more complicated still, the branches of each neurone
are connected to thousands of other neurones.
It's hard to grasp the sheer scale of all these connections.
Imagine a bustling city the size of New York.
Give every person in that city 10,000 pieces of string.
Tell each person to attach each piece of string to a different person.
Now make the city a thousand times bigger.
This is the incredible tangle we call the brain.
And there's more.
Go deeper into this tangle,
travel along a single neurone and take a close look at the junction with its neighbour.
0ddly, the neurones are not physically joined together at all.
There's a tiny gap.
To bridge this gap, the neurones release minute quantities of chemicals
every time they fire, chemical go-betweens that influence our thoughts.
This cocktail of chemicals swirling about the brain is finely balanced.
It needs to be to control the activity of the brain.
Because it's so much on a knife-edge, it's very easy to disrupt.
People do it every day. I like to do it,
just occasionally, with some Cabernet Sauvignon.
People have been drinking alcohol for thousands of years.
But surprisingly, it's only in the last couple of years that scientists have discovered
precisely how it works.
So, in the interests of science, I've put myself forward as a guinea pig.
Before I start, I need to test my reaction time.
This little red light will come on, and I'll press the red button.
That's fifteen hundredths of a second, just under one fifth of a second. That's about average.
Well, I've now had three glasses.
Unlike what most people think, it isn't actually the alcohol itself which makes you drunk.
Rather, as soon as the alcohol enters your body,
there are a series, a cascade of chemical reactions.
It's the by-product of one of these reactions, the fatty acid compounds,
which make you drunk.
Well, I've had well over a bottle of wine now,
and although I feel pretty good, my ac...
..reaction time isn't what it should be. We'll try testing it.
It's about quarter of a second.
Slower than before.
There's a good reason why my reactions are sluggish.
The normal chemical balance in my brain is being disrupted,
as those fatty acids clog up the surface of the neurones.
The fatty acids attack only parts of my brain,
including those that control my speech, my mood and my memory.
What was I saying? Well, what was I saying?
Alcohol just influences behaviour. Some people...
..just get belliru...belligerent.
0thers... No, wait a minute.
Actually, I can't remember terribly what I'm supposed to say.
(MAN) Action.
What was I saying? Alcohol also influences behaviour.
Where's the coffee?
Sorry?
Well, I... Just say ''action'' and I'll be on the ball.
Action.
I'm not sure I can get my head round this completely now. Actually.
How can all my thoughts and behaviour come from chemicals and little neurones?
Some people compare the brain to a computer,
but I think it's much more like a termite mound.
It's all to do with the whole thing being greater than the sum of its parts.
A termite colony is extraordinary.
It is as intricate and as complex as a city.
It can dominate whole areas of the bush and wage war against other insects.
Above all, it can build these stupendous structures,
with columns and buttresses
and air-conditioning ducts.
So where is the knowledge for this incredible organisation kept?
Not in an individual worker termite.
They are supremely dim, with a brain the size of a pinhead.
Nor in the enormous, squirming, egg-producing queen.
Her brain is even smaller than a worker's.
No. The intricate behaviour of the termite colony
emerges from the collective effort of all the termites.
Here, a group of worker termites are constructing a new wall.
Not a single one of them carries a blueprint for the wall, but working together, it gets built.
Termites send out chemical signals,
and between them they pile up their tiny mouthfuls of mud.
Clearly the human brain is totally different from the termite mound.
Both, though, are composed of numerous building blocks; either neurones or termites.
Each, when acting in harmony, is capable of extraordinary feats.
It makes no sense to search for the root of knowledge
in single neurones in the brain, or, for that matter, in one termite in a colony.
The success of both depends on many millions of simple units working together.
So it's teams of neurones acting in unison that give us all our skills.
Each team, based in a particular region of the brain, takes on a different responsibility,
from our most advanced human abilities, such as language and memory,
to the more basic ones, like movement.
Because we walk, run and reach without thinking,
we forget how such incredible precision is possible.
To see how much brain effort is required,
look what happens when we're plunged into a totally new environment.
- OK. - OK, there we go.
Astronauts have to learn to move from scratch when they enter a world without gravity.
The reason why we're able to learn new tasks and carry them out automatically lies here.
It's a part of the brain called the cerebellum, or little brain,
because it sticks out right at the base of the brain proper.
Here are stored the practised movements we all learn, be it riding a bike, playing the piano,
or even fixing a satellite.
The astronauts are in the cargo bay of the shuttle, but they're not out in space.
This is the closest they can get to space back on Earth, an enormous swimming pool -
a pool so large that four space shuttles can fit inside it.
Here astronauts can practise their tasks over and over again,
until they can move automatically without thinking.
(ASTR0NAUT) I had to jig it a little to lock.
Yeah, it is finicky about being directly perpendicular to the rail,
so try to wriggle it back and forth, from starboard to port, and from forward to aft.
OK.
- We're assuming the latches didn't work. - So they're manually...
Marsha Ivens is one such astronaut.
Talk about seeing the world.
She's been on four shuttle missions and orbited the planet 683 times.
(MARSHA IVENS) Learning to deal with the absence of gravity takes a little getting used to.
We are used to walking from place to place, and you don't walk, you float or fly.
So when I want to cross the room or the cabin, I push off with my hand or feet.
If I push too hard, I smash into the wall. If I push in the wrong direction, I miss it.
If I don't push off hard enough, I don't get to the wall. It takes a bit of getting used to.
0nce we've practised a skill enough, the cerebellum can take over automatically.
A thought starts it off, and then the cerebellum does the work,
sending out instructions to the rest of the body.
This happens without us even being aware of it.
In fact, the unconscious part of the brain is often more skilful than the conscious part.
0n the space shuttle is a robot arm.
The astronauts have to train hard to operate it, using a joystick.
But the secret with moving a robot arm smoothly is not to think too much about it.
Let the cerebellum take over.
(MARSHA IVENS) For me it was difficult to think about moving each joint as I moved it.
And I just did it, and it got there.
The more experienced you get, the more rotations you can make at the same time.
That's probably true of learning to use your hand.
When you reach for something, you make complex motions with your arm,
and that's probably as learned a response as it is learning to control the robot arm.
The astronauts use the same mental equipment to control the robot arm
as we first use as babies to control our flesh and blood arms.
People have a fantastic ability to make almost any tool an extension of their bodies.
As an infertility doctor, I make full use of my cerebellum to perform keyhole surgery.
Here, I'm investigating why a woman is unable to conceive.
Surgical tools allow me to examine inside her, without resorting to major surgery.
After enough training, it is relatively simple for me to co-ordinate what I do with my hands
with what I see on the screen.
Truth is, that this surgical manipulation, like all surgical manipulation,
looks incredibly skilled and very intricate.
But actually, most of the time you're doing it totally on autopilot,
and you can do quite involved procedures without really thinking about it.
It's only when there's something untoward, or the surgeon hits an emergency,
that you suddenly need to concentrate much harder and the conscious brain takes over.
Most mammals have a cerebellum just as developed as ours.
A rat's primitive brain is largely cerebellum.
They don't need much more for their relatively simple lives.
And in humans, the basic design of this rudimentary part of the brain
has changed little as we've evolved.
It is the rest of our brain that has enlarged so massively.
Why did it get so big?
Well, surprisingly, a whole quarter of our oversized brain is devoted to vision,
much more than for any of our other senses.
What you see when you peer into the back of the eye is the only part of the brain
which is visible from the outside world.
The optic nerve at the back of the eye is a direct extension of the brain.
Travelling along the optic nerve, we pass right through the brain.
Here, at the back of the head, is where the visual information arrives.
0ur eyes are just a window. We actually see with our brain.
It's difficult to grasp how complicated vision is, until you try to programme a computer to see.
It's staggeringly difficult.
What the scientists hadn't realised was that the eye is merely the first step.
The brain does most of the real work.
These robots have excellent cameras on board,
but they lack the clout of the brain to make sense of what they see.
This can be a handicap.
0ur brains are so powerful that we very much take our visual skills for granted.
To fly this 1940s biplane,
Marsha Ivens relies more on the view from the cockpit than the instrument panel.
(MARSHA IVENS) In an airplane like this, vision is your primary means
of knowing where you are, relative to the world, in the airplane.
My brand of flying doesn't really require a whole lot of dials.
I can tell what my rate of descent is. You learn with experience.
I make periodic checks of the altimeter and the airspeed and the vertical speed indicator
for that information, but mostly I do that by looking outside.
Whenever we look around us, we see the world instantly.
The shape of a plane, its movement, its colour.
But what's surprising is that all these aspects of the image
have to be processed by the brain separately.
We know these various elements of vision are distinct,
because certain people with brain damage are missing one of them.
Some cannot discriminate colour...
..while, more bizarrely, others are unable to perceive motion.
It's as if they're seeing a stationary snapshot of the world every couple of seconds.
But in normal vision, our powerful brain combines all these disparate elements
into one coherent view of the world.
As the brainpower of our ancestors increased, they not only observed the world
but also invented ways of shaping it.
We can see this in action by looking at the tools that chimps make.
The chimps from this group use an impressive 19 types of tool.
Most of them are to get at food. Thin sticks help them catch ants and termites.
Chimps even use stone anvils and wooden hammers to crush the shells of nuts.
It's jolly difficult making a stone tool.
So, here's one that was prepared earlier.
About two million years earlier.
The creature that made it chipped away slivers of stone to give it a sharp edge,
and it was probably used as a kind of axe.
Archaeologists here in the Great Rift Valley of Africa
are really excited about this and the other tools they've found,
because it wasn't apes that made them, it was people.
Louise, what's so interesting about this area?
All this site is special because there're such vast concentrations of stone tools here,
and this is because it was a lake basin.
The early humans were coming down to catch their animals, kill them
and use the stone tools on the carcasses.
I found it quite difficult making a stone tool. What's the trick?
You need a big brain, and to be quite well practised to manipulate your hands
to strike a flake off a piece of rock and come up with a result like this.
I'll forgive the slur on my brain, but how do you know that these were used to butcher meat?
That seems a bit far-fetched.
We've found stone tools with a carcass, say of an early elephant,
where you've got stone tools and bones which show cut marks,
so you're pretty sure those stone tools were used to butcher that animal.
A chimp cannot make a stone hand axe. It's not just the lack of brains.
A chimp's thumb is very short compared to its other fingers,
making it awkward to use all but the simplest tools.
But over hundreds of thousands of years, our human thumb lengthened.
This gave us an enormous advantage.
We could make a precise finger pinch between thumb and forefinger.
It's called ''the opposable thumb,''
and it allowed us to manipulate objects with great dexterity.
Marsha harnesses this precision control of her fingers to do safety checks on her plane.
I pluck the wires on the tail and should hear them ring the same tone.
and the pilot.
As I walk around the airplane, sometimes your hand will feel something your eye doesn't see.
If I run my fingers along the propeller,
I can feel a nick that I wouldn't necessarily see.
I don't want nicks, as that disrupts the airflow.
The sensitivity of our fingers comes from the ridges and grooves of our fingerprints.
These ridges also give us better grip, especially in wet conditions,
just like the tread of a car tyre, cornering in the rain.
But what have fingers got to do with the brain?
Well, throughout our evolution, developments of the brain and the body
were constantly bouncing off one another. As one advanced, it drove the other forward.
This feedback relied on a key turning point, one that other animals failed to make.
Chimp hands aren't very dextrous, because they do two contradictory jobs with them.
They hold things, but they also walk on their hands. So their hands are a compromise.
Not bad for knuckle walking, but not so good for creating tools.
Human hands excelled at creating tools and manipulating objects
because they were largely dedicated to just one activity.
Unlike chimps, we did this.
We stood up on our hind limbs.
This crucial advance happened over 3.5 million years ago.
Standing up gave our hands enormous freedom and boosted our brainpower dramatically.
We never looked back.
Standing tall on two legs happened very early on in the development of the human body,
before we had opposable thumbs, before we had stone tools, before we had language.
Indeed, standing helped these developments.
Early humans literally had time on their hands -
time to challenge their tiny Fiat 500 brain, jump-starting it into further evolution.
As our brain got bigger, so it perfected one rather special trick.
It learned to make order out of chaos, putting things into categories.
Coffee with caffeine and coffee without? Kenyan or Colombian?
It's no accident that this is how we organise our daily life.
I'll take a couple of those. Thank you.
We came to classify things this way so that we could cope with the complexity of nature.
To survive, we had to learn which plants were poisonous and which we could eat;
to know which animals would make a good meal and which were likely to make a meal of us.
Animals do this to some extent, but the human brain excelled at it.
We still use this skill in city life,
but in the natural world, you can witness it the way it was originally deployed.
Philip Alderson is a park ranger in north Australia.
Forest fires sweep the park in the dry season, and Philip lights small control fires
to burn up dry tinder and stop the spread of a bigger fire that's approaching.
It's called ''back burning,'' and has been used by Aboriginal people for thousands of years.
You can see the big cloud of smoke over there, and it's roaring through.
When the main fire front comes along, it gets really windy,
with little whirly winds everywhere.
The back burning stops it from coming any further with the wind.
It would carry it across the other side of the road, all that debris and sparks.
The ability to understand and control the natural world
was crucial to survival throughout our past.
This river is teeming with crocodiles.
The same skills that Philip's ancestors used to kill them, Philip now uses to count them.
He tracks them down by knowing their habits.
(PHILIP ALDERS0N) They live underneath the bank where there's tree roots.
They dig a hole underneath the tree root.
If you see this hole, you know it's a breathing hole.
They pick out an area for their hunting.
If another crocodile goes in there, they soon have a go at him,
because they get very territorial.
To outwit nature, we needed our brains above all.
Most important was powerful memory.
Working memory, usually lasting only a few minutes, is like a mental blackboard,
storing just seven items or so.
Working memory is remembering if that's the same crocodile you saw before
or where you just put your notebook down.
The vast majority of these memories quickly disappear.
But there's a part of the brain that ensures memories can be stored for much longer.
As certain thoughts are remembered, over and over, they are passed to the cortex,
the folded part enveloping the front of the brain.
This is where our long-term memory resides.
How these memories persist is not yet fully understood,
but the best explanation is that memories are shared across many different neurones.
0ver time, the branching connections between these neurones are strengthened.
This is how we remember our family and friends, the important events of our life.
0ne estimate is that an average person store in their brain a million different items.
This powerful memory originally evolved to help us navigate our way around our environment.
(PHILIP ALDERS0N) If you come back at night, you can pick out certain points or channels.
You know where you are then, you know.
- It is quiet, isn't it? - Yeah, it's quiet.
- You'd reckon we'd pick one up by now. - Yeah... Look straight up there, mate.
The crocodiles prefer to come out at night.
In the dark, Philip can still spot them. Their eyes reflect the torchlight.
(PHILIP ALDERS0N) There's one there, straight up, near the bank.
Every time Philip revisits the river,
he gets to know it that little bit better, as it's etched on his mind.
Turn to the left.
Guess what?
Got a fish.
A few people have memory skills well beyond the ordinary,
and most of the best are collected here, at the 13th Mind 0lympiad in London.
They've come to flex their powers of recall.
so you get 15 minutes to commit to memory,
starting now.
The contenders come from a surprising range of backgrounds.
There's a DJ, a fireman, a naval officer, and the usual contingent of students.
They all share the staggering ability to memorise thousands of numbers off by heart.
Andy Bell has been coming here for three years.
I'm here is to try and win. It's very competitive.
I've broken some records, but the main thing is to try to win the championship.
There's little chance of that today.
(ADJUDICAT0R) Ready, steady, go.
This man has won the memory championships four times.
This man has learnt the answer to every single Trivial Pursuit question.
The only thing that stands between him and victory today is a full deck of cards,
he has to view in under 40 seconds and memorise in just three minutes.
He is Dominic O'Brien.
How do they do it?
(ADJUDICAT0R) Stop memorisation, start recall.
The National Institutes of Health in America has spent three years
and a quarter of a million dollars to find out what was different about these people's brains.
Six of spades, eight of spades.
Their conclusion: these people are completely normal.
Three of spades.
They don't have photographic memory, which most scientists believe is a myth.
In fact, the only difference between them and you
is that they have trained the memory that we all share.
Queen of diamonds. Is that right?
(ADJUDICAT0R) One minute.
That's the one I got wrong.
Another victory for Dominic O'Brien.
So what's Dominic's secret?
(D0MINIC O'BRIEN) If I'm presented with a hundred-digit number, it doesn't mean anything
unless I break it up. So I break up a long number, sequence it into pairs of digits,
and give each pair of digits a character.
For instance, the number 10 is Dudley Moore and the number 07 is Roger Moore.
99 would be Mr Whippy.
Then I have something I can work with. To remember those numbers in sequence,
I imagine them on a journey. It's a bit like making up a story involving those characters.
That means the story for the number 1-0-0-7-9-9 would be
Dudley Moore meets Roger Moore
for an ice cream. Easy.
(D0MINIC O'BRIEN) We're born to hunt and gather,
so that's why I use journeys.
I have to translate the abstract thousands of meaningless numbers
to something my primitive - if you like, caveman-like brain - can understand.
You look very serious. A little bit happier.
Dominic turns random information into stories
because his brain has evolved to absorb stories easily.
Stories have played a key role in retaining other much longer memories.
The Aboriginal animals and gods on this wall tell their own tales from long ago.
Rock art is really just an extension of memory,
a more lasting way of storing traditions.
The big red kangaroo on the top there. There's some barramundi.
Perch, another one.
If you'd hunted your first fish, they'd paint it up on the wall,
so everyone can have a look at what type of fish it was.
A lot of these paintings are 20,000- to 40,000-year-old paintings,
and you can see it was almost like painted yesterday.
You find them down there sinking the hole.
Parents teaching their children is another way of passing on information.
Philip shows his son how to find the turtles that live in the mud.
They're in the hollow, Sam. Hollow one, like rock.
That's the one. Big one. Dig him up.
They're learning a lot.
Teaching a kid from a young age is important, because it helps you keep your culture,
and understand the grassroots of where you come from.
Through our parents, through art, through education, we learn about the world.
All this knowledge is absorbed by the powerful human brain.
I mean, in many parts of Islam, if a woman can't reproduce, she is very badly damaged.
Sometimes we look at Islam and think ''How bizarre,'' but it's the same in all religions.
I'm a Jew. It's the same, to some extent, in Judaism.
It's the same in Christian society.
The brain's hardest task is how to deal with human society.
Perhaps the ability to cope with other people and get on in society
has been the main force behind the growth of the human brain.
If you think about it, the most complicated thing
that an ancient human would meet in their lives would not be food,
nor a tool. Not a predator, but another person.
It's other people, not the world itself, that's difficult to deal with.
To work out the motives of others, to persuade, to charm, to make friends and not enemies,
all this takes brains.
We can see it in action with our closest relatives.
Chimps are constantly vying with one another to be leader of the troop.
Here, a young male chimp is attempting to usurp the older male.
And while fights are certainly dramatic, often more important than just brute strength
is the ability to forge alliances with other chimps. Brain over brawn.
Chimps spend hours picking through the hair of their colleagues.
It's called grooming, and it's the key to social climbing.
The better chimps are at these social niceties,
the more likely they are to rise through the ranks.
Scientists have discovered
that the more complex the social group an animal belongs to, the bigger its brain.
An ability to deceive, to make allies, to win others over,
must have been vital in the development of the chimp mind.
Sound familiar?
Human societies are the most complicated of all animal societies.
There's continual pressure to be number one.
And where better to look for it but in the corridors of power?
While the ceremony of parliamentary life looks rather splendid,
it's the jostling that goes on behind the scenes that is often more important.
Politicians huddle together in conspiratorial whispers.
Deals are made and broken.
The MPs, the lords and ladies,
are demonstrating skills that haven't changed for millions of years.
I should know, I work in the place.
We're not chimps, but it's a jungle out there.
And you don't have to go to the Houses of Parliament to come across politics.
All the time our brains are dealing with politics with a small ''p''.
Gossip, flattery, backbiting.
At home or in the office, it's really just our way of getting along with people.
0ver millions of years,
the human brain and body have evolved to meet ever more complicated challenges.
We learned to manipulate tools, we made full use of our visual sense,
and we developed a powerful memory.
More recently, we mastered language, a highly efficient form of social grooming.
We can now build up a detailed picture of the brain we've evolved:
the cerebellum, responsible for automatic movements;
the back of the brain for vision;
the frontal cortex for memory.
There's even a particular site for language.
But there's still something missing from this map.
It's the mysterious thing that makes you who you are and me who I am.
Scientists call it consciousness.
Consciousness is the greatest of the brain's qualities.
It's actually very difficult to define,
but essentially it's our ability to be aware of our own thoughts and feelings,
for each of us to have our own personality.
Without consciousness, we'd be little more than robots,
trundling through the motions of life.
Consciousness allows us to appreciate the greater things in life:
love, art, science, and religion.
Consciousness makes our brain more than just a collection of little grey cells and electricity.
It's what makes us truly human.
As a subject, consciousness is extremely difficult to study.
But a series of extraordinary surgical operations have revealed some startling new facts.
This rather sad story began in the 1960s.
Brain surgeons, desperate to treat their severely epileptic patients,
pioneered an operation to try and control epileptic fits.
OK, Dave, I'm going to start to divide the corpus callosum.
This dramatic surgery involved slicing the brain right down the middle.
They hoped to restrict future fits to one side of the brain only.
It was a radical approach.
But the patients had such severe epilepsy that this was their last hope.
The operation usually worked, but it had unfortunate side-effects in a few patients.
Vicky is one such patient.
Afterwards, scientists discovered the surgery gave her two independent minds,
each controlling one half of her body.
It became apparent even when Vicky got dressed.
(VICKY) I knew what I wanted to wear,
and I would open up my closet, and one hand would get ready to take it out,
but my other hand would just take control.
A couple of times I had a pair of shorts on,
and I found myself putting another pair on,
on top of the pair I had on, which I knew was wrong.
I wouldn't go out the house that way.
Each of her hands is obeying one half of her brain.
It's as if her consciousness has been split in half,
two minds in her one brain.
This is extraordinary.
If our consciousness is located in just one side of the brain,
it can never be separated into two, in the way that it is for Vicky.
So I cannot point at one part of my brain and say that is where ''I'' reside.
Put simply, consciousness is part of the whole brain.
Perhaps, in the same mysterious way that the termites work together in the colony,
so the many elements which make up our consciousness work in harmony.
It looks like the higher abilities of the brain -
memory, perception and emotions -
are seamlessly bound into one wonderful whole.
But is there more to it than this?
As a scientist, I believe that science is the most powerful way
of finding out about the human body.
Even so, there will always be some questions that it just cannot answer.
As a religious person, I believe that much of what makes us human
will forever remain mysterious, even spiritual.
I call it the soul.