I look in the mirror, and I don't know who that is.
I can be looking straight at something and I just don't know what I'm looking at.
It's almost as if I'm day dreaming.
There is no sense no meaning in what I see.
One man can't recognise every day objects. Another can't recognise faces.
Damage to their brains is preventing them from making sense of the world.
If it's the brain that sees, how does it do it?
How does our brain manage the immense task of generating vision?
Las Vegas, the brightest city on earth.
A city that erupts every night into an explosion of light.
It feels as though we see it all without effort
but our brains are working away frantically.
Vision seems so simple.
We just open our eyes and we see what's there.
But in fact we're taking on an awesome challenge.
What's actually hitting our eyes is a jumble of light,
and transforming this jumble into the complex world we know
demands a phenomenal amount of brain power.
Yet we do it all, in the blink of an eye.
Every aspect of everything we see has to be constructed inside our heads.
Movement, shape, colour, size, what everything is and where it is.
Nothing in the world is simply there.
It all has to be pieced together by the brain.
The more we learn about how the visual system actually works,
the more it seems to contradict the actual experience of sight.
Information coming into our eyes is dismantled
and reassembled so convincingly that we never realise what's actually going on.
As neuro scientists gradually discover the elegant tricks
and bold short cuts the brain uses,
it's becoming clear thatour mental image of the world
is only loosely based on reality.
Could our experience of just seeing what's out there be an elaborate illusion?
Even the most basic features of vision are constructed by the brain.
The most compelling evidence for this comes
from the study of extremely rare cases of highly selective brain damage.
Twenty years ago Gisela Leibold suffered a stroke.
It left her unable to see motion.
Everything she sees is frozen,
even though her other senses shout out that the world is moving by.
For Gisela Leibold, it's so hard to see the movin
Faced with the massive amount of visual information coming into our eyes,
it seems we divide up the task of building
the scene in our heads into different components,
and Gisela has lost one vital component of her visual world.
My first impression was that it's something really very strange
and when I ask her now what is your problem she told me
I can't see objects in motion and like others I didn't believe it,
because nobody has ever described a case like this.
Move
Professor Josef Zihl has studied
the unique phenomenon of Giselia Leibold for twenty years.
His tests reveal how she now struggles to make sense of the world.
She relies on the fact that the static image she is seeing is eventually updated.
After a delay of a few seconds she can deduce that something is moving
if the snapshot in her mind has changed.
Gisela Leibold's stroke damaged a small area at the back of her brain.
What makes her unique is that the damage was precise and also symmetrical.
This accident of chance proves that when damaged particular brain regions
can selectively prevent the processing of movement.
It is very difficult to imagine how the world of Frau Leibold may look like.
Although she cannot see movement in the sense of tell us
whether something is moving or not,
or tell us the direction of movement or the speed of movement,
moving objects appear to her as restless
and this is what makes her feel very unwell,
and irritates her and makes life so difficult for her.
Our eyes only capture static images, still photographs of the world outside.
These images travel to the back of the brain,
where they are incorporated into the sensation of seeing movement.
And we now know that different aspects of vision
are dealt with by different visual sub systems.
No one knows why the brain is organised this way,
but it makes sense to me that this division of labour
is the most efficient way for coping with everything that's bombarding the eye.
If the brain would be built in a way that only one structure,
or one mechanism or one module,
would have to process all the visual information which is coming in,
then it would take a much longer time.
So the solution is to have smaller visual areas, smaller mechanisms,
and each mechanism is dealing with just one aspect of visual information,
Iike form or colour, or depth or movement.
Gradually, neuro scientists are building up
a detailed map of this parallel processing.
The raw jumble of information from the eyes travels to the primary visual cortex
and on to a series of increasingly specialised areas for processing.
So far over 30 different areas have been discovered,
working on motion, colour, depth, shape and even which way an edge is pointing.
We can't say yet exactly what they all do
but recently an underlying logic to this assortment of areas has been uncovered.
OK, so if you close your eyes.
These two bars are exactly the same size.
It seems as though my visual system has been totally fooled by this illusion,
but this experiment proves that's not the case.
OK if you open your eyes again.
Can you tell me which looks longer if either of them do.
Yes this looks longer
Fine OK
The precise movements of my fingers
are tracked by a special set of cameras as I reach for the bars.
Perfect.
If my entire visual system has been fooled,
then my grasp should be wider for the bar that looks bigger.
And open them and tell me again are they the same or different?
No this looks bigger.
OK so when I say go pick up the one on the right. 2, 1 - Go
Great.
The movements of my fingers
reveal a fascinating aspect of the workings of my brain.
The bars look different lengths
but my fingers shape to pick them up in exactly the same way for each.
Part of my visual system which is guiding
my hand has not been tricked by the illusion
and is acting independently of what I'm consciously seeing.
This kind of ingenious research shows that all the specialised visual areas
are organised into two different pathways with very different roles.
One pathway, which was guiding my hand, helps us interact with the world.
We're unaware of it but every movement
we make is fed by information from this pathway.
The more laborious task of recognising
what things are is handled by a different pathway.
Maybe that's so we don't have to wait until we know
what something is before we move to deal with it.
It seems my hand can ignore what I think my eyes are actually seeing
because these two tasks are treated so separately in the brain.
We don't yet fully understand why the segregation occurs,
but of the two it is the recognition system
that seems to take up more brain power.
Recognition is a vital part of our visual system.
It turns seeing into understanding.
Of all the things we need to recognise,
there's one which is fundamental to how we live our lives - the human face.
It's how we know who someone is, who we love, who we hate, and who we fear.
Our brains seem tuned to spot faces.
We have so much hardware in our heads that is dedicated to recognising faces.
It takes almost nothing to make us see a face,
I mean just a big chunk of our brain is saying where's the face, where's the face?
So you know the most minimal configuration of lines
and a couple of curves will look like a face.
Even you know clouds, the man in the moon.
Just the pattern of craters on the moon we see as a face.
But Lincoln Holmes finds recognising a face impossible.
Thirty years ago he was in a car accident
that damaged an isolated part of his brain,
and he is now completely face blind.
I'll have moments when I'm suddenly alone
and I don't know where anybody that I'm with is.
There can be a surge of fear and it's lonely in that sense.
The very thought of something so basic
as recognising faces being lost is not only hard to imagine,
but it's pretty scary.
One of the things that makes it hard for people to believe that
I have such a deficit is that I'm not blind.
I see them and er seeing in our vocabulary
is synonymous in some ways with understanding - I see what you mean.
Er and it's very hard for folks to understand that I can see them,
and not know who they are.
Sometimes it seems like maybe he recognises me
because I'm in the right place at the right time.
I've said we're going to meet at such and such a location and he finds me,
and he says Hi Holly,
but I think it's because we've made pre arrangements that yes
we're going to meet at X place at X time.
Maybe another way to put that is that
when there are just the two of us sitting here it's one thing
when we go out to the supermarket say and get separated
then there are a couple of dozen female faces walking all around
and I haven't got a prayer, I haven't got a prayer.
I haven't got a prayer of picking you out of all those faces.
-What's that? -That's a key.
Great.
-That's an apple. -OK
That's a place setting with a knife, fork and spoon and a plate.
All right
Who is it?
Um... I don't know, I don't know.
OK, young woman, old woman?
To be very honest I'm having trouble answering that question. Um...
Let me give you some biographical details.
She's a movie star, from the 1950's, very glamorous.
She sang Happy Birthday to President Kennedy once.
-Marilyn Munroe? -Yes
Marilyn Munroe as you know had a close affiliation with more than one Kennedy
but that's neither here nor there.
When I'm asked by people sometimes do faces all look the same,
er the answer to that question is that no they don't all look the same.
And they say well why don't you recognise them
and the answer is they don't all look the same,
but they don't all, in other words they don't all look like John Smith.
None of them look like anyone.
They all are faces, but they are not recognisable
as anyone's face, any of them.
He sees the skin, he can see the texture of the skin.
He can see the individual features fairly well,
but what he doesn't see is the totality of the face.
He can't um simultaneously apprehend all of those different parts together
and that's what we have to do to be able to recognise a face.
It's hard to imagine what Lincoln is actually seeing when he looks at a face.
It seems that his brain is not allowing him
to put all the pieces of the puzzle together.
Instead he is confronted with a jumbled up mixture of features
which he cannot connect with even the most familiar of faces.
OK how about that person?
Um, don't know.
Any sense of familiarity?
No. What about the, there's a child's face sort of looking over his shoulder.
Any familiarity there?
This is the nastiest one of all isn't it? This is me?
Yes
How do you feel looking at a picture of your own face,
and not recognising it?
For me
it is a face, it's not my face. It's a face.
And there is some sense of incompleteness there but er,... So be it.
Lincoln's story has helped reveal how our brains process faces.
Each time we look at another human being,
a specific facial recognition system is activated.
It turns out that this system is so specialised,
it only deals with faces which are the right way up.
It seems that facial recognition is such a demanding
and important part of our lives
that we need to dedicate a whole sub system of the brain to this task.
And the work with Lincoln suggests that
this face area plays no role in recognising
any other type of object.
Muhammed Ali, Cassius Clay.
Uh hum. Yeah. Absolutely right good.
Albert Einstein.
Good.
Um it's an oblong
um it's got lots of legs on it.
Er,...There's a black thing at the top of it, don't know what it is.
If I told you that it was a kind of scrubbing brush,
what you referred to as the legs are actually the bristles.
Oh OK.
The black part at the top is actually just a shadow that's falling from the lighting,
it's not actually part of the object itself.
I could see how that could be a scrubbing brush but I didn't get it. OK.
In Ottawa, Kevin Chappell provides another vital clue
to the brain's visual recognition system.
He has no trouble with faces,
but a car accident has left him totally unable to make sense of the world.
He sees all the details, but not what things are.
Well after all these years I've kind of got used to it now.
It's me, it's how I am, that's my world.
Often I'll let things just pass me by.
If I have to then I'll make an effort to figure out what it is,
for example you know
if the upper part of what I'm seeing is blue therefore probably sky.
The green is obviously if it's sticking up that's the skyline, they're trees,
if it's flat it's you know grass.
That's how I make my sort of judgements about where I am. Many times I'm wrong.
It's a very interesting and fairly rare condition
Whereby the eyes are working just fine
and can take in the light from the visual world in a perfectly normal fashion.
The problem is in Kevin's case in being able to decode these signals
and produce a coherent interpretation of the world.
So it's not like he has lost his knowledge of what objects are
and it's not like he simply cannot produce the name for it,
you know maybe he's just forgotten what the word is,
none of those can account for his problem.
The problem is an inability for the information from the visual world
that's coming into his brain to make contact with this knowledge
that he has about objects.
Um... I really don't know what, coloured, coloured squares.
There are a few faces in the squares, um. I can see certain faces.
What about in the parts where there aren't faces?
There are just red blotches and black blotches.
Oh they could be playing cards, with the blotches.
It's interesting that you were so rapidly able to pick up the faces,
but the suits somehow didn't quite make sense to you.
It's becoming increasingly clear that the brain segregates objects from faces,
but we still don't fully understand why or how this compartmentalisation occurs.
What is so special about faces
that means they need separate processing in the brain?
One reason might be that faces actually look very similar,
so a specialised area within the brain is required
with a finer more powerful level of processing.
Without this facility, we'd be able to spot a face
but we wouldn't be able to distinguish whose face it was.
Object recognition seems to be a simpler task.
It doesn't need such a high level of processing.
Once we've named an object
we don't normally need to take the recognition task any further,
and so a more basic part of the brain is used.
But even with all these specialised
systems working away the brain would be overloaded
if it tried to tackle every detail of every object at once.
So we just don't bother.
We're all equipped with the means of selecting the key aspects
of a scene one at a time.
This attention system allows us to concentrate on one thing,
while the rest of the world falls into the background.
All this happens so automatically that we don't notice it
but our brains are constantly scanning the scene,
not just passively analysing what's coming in
but actively deciding what it is it wants to see.
It seems that we don't just have to point our eyes in the right direction,
we also have to point our brains
The difference between these two men seems obvious
Their faces are different, their hair is different,
even their shirts are a different colour.
And yet an experiment by psychologists Dan Simons and Chris Shabrie at Harvard
reveals that our brains actually process very little of
what comes in through the eyes.
In this experiment a subject comes up to a counter
and our first experimenter hands them a consent form,
As soon as they've finished signing the consent form,
they hand it back to the first experimenter,
who then takes the consent form, ducks down behind the counter and puts it away,
and a different experimenter then stands up
and hands the subject a packet of information and sends them into a hallway
where we ask them questions about it.
This wonderful experiment uncovers an aspect of
the brain's attention system known as change blindness.
Change blindness is the idea
that we often miss large changes to our visual world from one view to the next,
we're often not able to see large changes that would appear to be perfectly obvious,
to somebody who knows that they're going to happen.
And incredibly in 75% of cases the subjects don't notice a thing.
The lady who took me up here,
she opened the door for me and told me to walk over to the desk.
I think there was a sign that said experiment
and a man there gave me a form to sign
There was a guy standing under a big sign that said experiment
and to my left there was like a pot with some dirt in it
and some plastic containers.
Oh I filled out a form right...
I asked him how long it would take, and he said about 10, 15 minutes or so.
I guess I have the time.
Did you notice anything unusual at all after you signed the consent form?
I just signed it and I didn't even pay attention to anything
that was written on it.
OK after you'd handed it back to him,
did you notice anything unusual happen at all?
If you could just take this into the next room?
No, no I probably wasn't even looking that direction,
I probably turned and looked towards the clear door and saw some people there,
then I turned back and looked at him for a second.
Did you notice anything unusual at all after you signed the consent form?
No.
This will only take 5 or 10 minutes.
Yeah it's real short.
The person who stood up was actually a different person.
OK.
I gather you didn't notice that was different?
A different person actually stood up and handed you this form,
and sent you out towards me.
I gather from your reaction you didn't notice that?
-No! -OK don't feel bad about that.
Actually most of the time, we find about 75% of people don't notice.
-Are you serious? -Yeah.
The person who stood up with the packet was actually a different person
-than the first person. -That is incredible.
-I gather you didn't see it? -I didn't catch that no.
What's really interesting is that some people notice these changes
and other people don't notice these changes.
If you could just take this.
And we really don't yet have a good idea what separates those people
who don't from those people who do.
It might be that there are individual differences
and some people are better able to detect these sorts of changes.
But it's also possible that it's just coincidence that the people
who noticed it just happened to be focusing on a feature that changed.
They just happened to be paying attention to the colour of the person's shirt.
Oh!
And the people who failed to notice
it just happened to be paying attention to something else.
The brain's attention system allows us actively to select what to look at.
It makes us very good at concentrating on tasks,
but it can also make us miss something happening right in front of our eyes.
Magic is all about making us think we are seeing everything,
when in fact we are missing the most important thing of all.
Magicians exploit the brain's attention system to the extreme,
but understanding how attention is organised in the brain
has been a difficult challenge.
Once again it's damage to the brain
which reveals much about how the normal brain functions.
The attention system is often affected
after injury to the right hand side of the brain.
This leads to a condition known as neglect.
Neglect leaves patients with a baffling syndrome,
as if half their world has disappeared.
Neglect is a very difficult concept.
It's a medical term that has been used for almost a hundred years
to describe a variety of behavioural conditions,
that is what patients actually do when they've had a stroke.
And most of these patients have strokes involving the right hemisphere,
the right part of their brain.
And basically what they tend to do
which is descriptive of neglect is they ignore one side of space.
So for instance they dress one side of their body,
they write on the right hand side of the page,
they miss things on the left hand side.
The stroke that Peggy Palmer suffered ten years ago
has left her with extreme neglect of the left hand side of her world.
Peter Halligan has spent many years
testing Peggy to try and understand exactly what is going on in her brain.
Actuality chat.
This time Peggy I'm going to show you this picture of a cat,
and I'd like you to draw it as accurately as you can.
Right OK.
Neglect is very little if anything to do with your eyes.
The vast majority of the problem arises
from the brain processes involved in attention.
Your attentional system provides for where your eyes move.
So in other words if something happens in my visual field
that's interesting I'll move my eyes there,
but why would you move your eyes there?
Only if your attentional system indicated that you needed to move there.
So your eyes are slaves to your attentional system,
and what's wrong in neglect is the attentional system has been damaged.
This cat has got two tails
No I didn't notice that.
See you don't have them on that side do you.
Is there anything else missing on it?
Um,
For instance look round around the left hand side.
That looks, yes that shoulder's missing isn't it.
The upper part of the body is.
I don't think about it you see.
So you thought you'd drawn a complete cat,
-with all the details. -Yeah.
When I show this to you now, and you're seeing this again,
does this surprise you?
I was very surprised to see that other tail, very surprised.
-What did you think when you saw it? -I really didn't see that at all.
What do you think when you see something like this now,
when I draw attention to it?
I don't know how I could have missed that.
I don't how I could have missed it, I really don't
Peggy as far as I'm aware never reports
when you ask her afterwards seeing half a cat
In fact I can draw half a cat and show it to her she'll say that's half a cat,
and she can distinguish between a half cat and a full cat.
So she can know the difference.
What she draws is different to what she actually seems to see inside her brain.
So Peggy is actually seeing a whole picture.
Her brain is filling in the gaps completing the parts that are missing.
Peggy's neglect reveals another vital aspect of the brain's visual system.
In her mind her drawing is complete.
What is missing on paper is generated by her imagination.
The power of our imagination is what makes a good horror film so frightening.
It isn't necessarily what's up on the screen that really gets our pulses racing,
it's what we think is on the screen.
It seems that the less we see the more we imagine,
and film makers have learnt that
there's nothing more vivid than the pictures we can generate inside our head.
But the imagination isn't just active occasionally Research
increasingly suggests that our brains are constantly distorting what we see.
Using imagination, our brains take a bold shortcut.
We guess what's out there from past experience,
rather than having to build up the image in our minds each time from scratch.
Every moment we open our eyes
our brains are filling in a vast amount of additional information.
The brain doesn't just allow us to see what's out there,
it actually invents much of it,
and over the last few decades neuro scientists have slowly begun to understand
how we can create this highly personal inner world.
If you look around the world seems to be high resolution,
almost photographically sharp and complete.
But in fact you're actually taking in remarkably little.
A lot of what you see,
or you think you're seeing you're actually filling in from memory,
you're actually completing from information
that's been stored from previous times, previous experiences with the world.
How the brain does this has baffled scientists for decades.
But in recent years an extraordinary theory has emerged.
Anatomical studies have revealed
that the visual brain relies as much on information coming
from our memories as from our eyes.
We are using our knowledge of everything
we've ever seen in the past to imagine what is actually out there.
I think the most remarkable facts about the brain is that
of the 32 known visual areas virtually all of them
that send a connection to another area,
receive a connection backwards from that area,
and those backwards connections are of comparable size to the forward one.
So there's enormous amount of information flowing backwards.
The discovery of these pathways
has completely revolutionised our understanding of the visual brain.
We can no longer think of vision as a one way street,
with information flooding in from the outside world
Instead it seems to be a two way street,
with massive amounts of stored information
flowing backwards from deep inside the brain.
It's a two edged sword.
On the one hand it makes it easier,
you don't have to register every little thing that's out there.
On the other hand it's dangerous you can see things,
quote unquote "see" things that aren't really there
So our perception of the world is affected
as much by what our brains expect to see as what is actually in front of us.
This room looks normal, but in fact it's massively distorted.
The girls are exactly the same size,
and yet your brain won't allow you to see them that way.
You can't tell that the left side of the room is much bigger than the right side,
or that the floor slopes down to the left corner,
and that the furniture has been specially designed to fool your brain.
All this creates the illusion
that the girl is changing size as she walks across the room.
Your brain simply will not let you see the room as it actually is.
Instead it uses its' store of memories to take a short cut,
creating an image of this room based on how you expect all rooms to look.
It's an astonishing example of how much our visual memories,
our imaginations, can influence what is right in front of our eyes.
Kevin Chappell helps us understand the process at work.
When he walks on to a football field he doesn't understand a thing.
He sees green, but doesn't recognise the grass.
He coaches the local football team, even though the moving white object
doesn't come together in his head as a ball.
Kevin uses his memories from before the accident
which damaged his brain to imagine what is in front of him.
These images are so vivid.
It allows him to hide how little he actually sees.
I still have the knowledge of what objects are,
based on my visual memory, and the ability to imagine.
You're on a green field, the ball's round and it's white and you kick it.
But when the players get in together
and they're tackling each other and there's a scramble in the goal mouth,
I can't tell you what's going on.
It's like this collage of different colours and movement.
It's the images stored inside his brain
that allow Kevin to cope with the world around him.
His brain damage has left these pathways undamaged,
even though his recognition system is completely destroyed.
Go ahead.
It's kind of a plate with writing on it.
Why don't you go and hold it. Go ahead and hold it, close your eyes.
It feels like an old 45.
Do you have an image now in your mind of what that is?
It's a 45 with the centre punched out.
Hm. Good.
Bizarrely, Kevin can use his imagination to draw objects
he can't recognise in the real world.
You know lets go ahead and do some drawing.
Why don't we start off by getting you to draw something like a scrubbing brush.
OK
Scrubbing brush OK.
Kevin presents to us a very clear example of a person
who unable to recognise objects is nevertheless able to see
those same objects in his mind's eye.
In other words to be able to have very detailed
and distinct and rich visual, mental imagery.
That's pretty good.
So that's kind of the handle and these are all the bristles coming down.
Yes. There's also I tried to give some depth to it as well,
it's not like the other drawings which are just 2D, this is a 3D drawing.
Uh huh. Good.
There seems to be a complete split between
what Kevin can see and what he can imagine.
He can't even recognise his own drawings.
Any idea what this is?
Um a tape player.
Uh hum. It's actually a bicycle.
And it's something that you yourself have drawn for me previously,
this is your drawing of a bicycle.
It doesn't look familiar to you?
No it doesn't look like a bicycle either.
It's very surprising to find a patient like Kevin
who shows a dissociation between visual mental imagery and perception.
The received wisdom in this area has been that visual mental imagery
and visual perception are simply two sides of the same coin,
it's just that one proceeds from the outside world inwards
and the other one proceeds from the brain in a downwards fashion.
In fact having a patient who shows a dissociation like this suggests
that these two processes are really not one
and the same as has traditionally been argued.
Kevin's condition has revealed a separation between the parts of the brain
that generate imagery and the parts we use for perception.
So how do these two systems fit together?
That someone like Kevin exists, makes it very difficult to understand
where all the different components of vision
are finally brought together in the brain.
There doesn't seem to be any very obvious area of the brain
where the back projections
and the forward projections reach each other and make contact,
and Eureka a coherent interpretation of the world is provided.
In fact I think there probably is no such area.
I think even if we were able to go and look in the brain
and see whether we could identify such an area
I think we would fail in that pursuit.
It's the most intensively studied of all the senses,
and yet vision remains elusive.
But one by one we're uncovering all the ingenious strategies
and short cuts our brain uses to tackle the awesome challenge of seeing.
Everything we're learning takes us further
and further from the simple idea that we just open our eyes and see what's there.
A few years ago I worked in New York with professor Rudolfo Llinas.
He's always liked making provocative claims,
and now he's convinced it's time for a revolution in how we think of vision.
It sounds extraordinary, but for him seeing is just another form of dreaming.
If you consider what happens when you dream
you find that amazingly you actually do feel pain and you do feel surprise
and you see things and you hear things, and the people that you know talk to you
in the proper language with the proper intonation.
So what that tells you is that dreaming and being awake are next of kin,
if not exactly the same thing.
If this were to be the case, and this is hypothesis,
then we would begin to really understand what the brain is about
because the brain is about making images.
This idea is in complete contrast to our normal understanding of the visual system.
Rudolfo believes that everything is running in reverse,
with the brain creating images that are then transformed into reality
by the information coming in through the eyes.
Basically the brain is a dreaming machine
It is the brain that generates reality, secretes reality so to speak.
The reality is modulated, it's limited by the senses.
We need to see, we need to perceive and to dream actively
because this is the only way we can take this huge universe
and put it inside a very tiny head.
We fold it, we make an image,
and then we project it out, and that's what we do.
We are only just beginning to understand
how the brain conquers the massive challenge of perception.
If Rudolfo Llinas is right
then what is going on inside our brains is much more important than
what is going on around us.
As I see it, vision is not about simply soaking up the outside world.
Instead it's an active process which invents,
ignores and distorts what's entering through the eyes.
It seems that all this is an optional extra.
What counts is what goes on inside our heads,
and what happens there is completely personal.
It's not so much that our visual system rebuilds the outside world,
but rather that we create from scratch our own private universe, our own reality.
In the next programme,
what is it about our brains are suppose to put in short of the planet,
which is the source of uniguse power to create cities and civilizations.