What's in Your Head? Royal Institution Christmas Lectures


What's in Your Head?

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Meet Charlie and Iona.

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As you can plainly see, Charlie is much taller than Iona.

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But sometimes reality is not what it seems.

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Welcome to the 2011 Royal Institution Christmas Lectures,

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Meet Your Brain.

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Let me introduce myself.

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I'm Bruce Hood, and I am a scientist interested in the human brain,

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what it is and how it changes as we grow older.

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Actually, when I said "I am Bruce Hood" what I really should have said is, "This is Bruce Hood".

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Because everything I am is really a product of my brain.

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It's not my heart, it's not my kidneys -

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these are important organs, but I could have them transplanted

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and I'd still be the same person.

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That's because it's our brain that makes us who we are.

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In this series of lectures, we're going to be looking at the human brain,

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what it is, how it works and most importantly, how it interacts with other brains.

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But before I do so, I'd like to introduce you to someone else here.

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Or rather, someone who is here no longer.

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This is a real human brain, from a person.

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Before they died, they made the decision to donate their brain to science,

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so that we could discover

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the workings of this most astonishing, amazing organ.

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It is so mysterious and complicated,

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we can't even begin to really know how it works!

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I brought this brain along tonight to remind you

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exactly who we are, and what we are trying to understand.

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It is truly awe-inspiring.

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Every one of you here tonight, and watching at home,

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has a brain inside your head.

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Every brain is important. Every brain is unique.

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But all brains have the same basic machinery -

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so how does a brain work?

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To help me answer these questions,

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I've invited along another brain scientist, Professor Vince Walsh from UCL.

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Give a big round of applause to Vince!

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APPLAUSE AND CHEERING

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So Vince, you've brought along this special machine

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that influences the brain.

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We're going to see it in action.

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But before we do, let's start with a simple demonstration.

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Do you know the Nursery Rhyme "Baa Baa Black Sheep"?

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-I think so.

-Could you give us the first line?

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Baa baa black sheep, have you any wool?

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That's good.

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Reassuring to know that professors still know their nursery rhymes.

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OK. I'm going to get you to repeat that,

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but this time, I'm going to stimulate this part of your brain

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with your machine.

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Start, please.

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Baa baa black...

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VOICE BECOMES DISTORTED

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LAUGHTER

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Don't be alarmed.

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-You're perfectly OK, Vince, aren't you?

-I'm fine, yes.

-That's very good.

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Somehow this machine has disrupted Vince's brain.

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This is a trans-magnetic stimulator.

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It's delivering a very powerful magnetic pulse

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for a brief fraction of a second

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but why is it disrupting Vince's ability to speak?

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I'm going to give you a clue with the next demonstration.

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Have a look at this old television over here.

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I'm going to need a magnet.

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You can see the image on the television is perfectly normal

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but look what happens when I bring a magnet close to it.

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You can see the image is being distorted by the magnet.

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Now, why is this?

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Well, remarkably, the answer comes from none other

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than the founder of the Royal Institution Christmas Lectures,

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Michael Faraday, because Faraday discovered over 150 years ago

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and often demonstrated in this very theatre

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that there's a relationship between magnets and electrical fields.

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The image on the television is produced by an electrified beam

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so that when I bring a magnet close to it,

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it's distorting the path of that beam

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and that's why the image is being distorted.

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So let's put these pieces of information together.

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A magnet can disrupt an electrical field.

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We know the magnet is disrupting Vince's ability to speak

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which is a product of his brain so we can conclude that the brain

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must be using some form of electrical communication to make you speak.

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-Is that roughly correct, Vince?

-True, yeah.

-OK, Vince.

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If I put a magnet next to my head,

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it doesn't seem to disrupt any of my ability to speak, so why is that?

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That's because the field you've got next to your head is static.

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Even though you're moving at about, it's moving very slowly.

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To create an electric field that disturbs brain cells, it's got to move very, very rapidly.

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Every one of those clicks you hear is 1/10000 of a millisecond

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so the field has to change very, very quickly

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to create any electricity in the brain.

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Would you like me to do some more disruption of Vince's brain?

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-AUDIENCE:

-Yes.

-Vince, I'm sorry,

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but we're going to put you through some more. OK, so, what else shall we try?

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How about some motor control?

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We could do that. We could try left and right-handed.

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Can we try just affecting your right hand, would that be OK?

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Right, so I'm going to take my magnet. Is it fully charged up again?

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-It is.

-I'll touch my nose a few times.

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Let's see how accurate it you are when I place it up here.

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-Is that the correct area?

-Mhm.

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ELECTRICAL CLICKING

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AUDIENCE LAUGHS

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Vince, tell the audience what that feels like?

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It's actually quite painless but I've lost control of my muscles.

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I've lost control of my ability to locate my hand in space.

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-It's a very, very weird sensation.

-Can we do one last example?

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Can you, um...can you clap for us?

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I'm just going to stick the magnet here, here we go.

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You ready? Start clapping, please.

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ELECTRICAL CLICKING

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AUDIENCE LAUGHS

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OK, I think we've put you through enough, Vince.

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Before you go, tell us, please.

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We've seen how a magnet can disrupt normal function,

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but does it have any application?

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It does. What we've done has been very dramatic.

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We've been using very high magnetic fields to influence the brain

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so we can see that it does affect the brain but if we use lower fields

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and stimulate specific areas of the brain, we can work on treating

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things like depression, or modelling brain disorders

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or modelling stroke in real research,

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so it's got lots and lots of applications.

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Vince, that's been absolutely fascinating.

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Would everyone give Vince a round of applause.

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APPLAUSE

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Do you realise we've just proved that the brain

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is an electrical system, and I think that's pretty cool.

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Not only do magnets disrupt brain function

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but we can use magnets to look at the workings of the brain.

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But to do so you have to have a very powerful magnet.

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And we happen to have access to one not here in London

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but up in Cheltenham where we've set up a live link.

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We recorded this earlier.

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Hello, I'm Dr Thalia Gjersoe

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and I'm here at the MRI scanner so you can read my mind.

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I'm here with Iain Lyburn who's going to take us through it.

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Welcome to the Cheltenham Imaging Centre.

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It's run by the Cobalt Appeal Fund

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and houses imaging for PET and MRI

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and today we're going to have an MRI scan looking at your brain, seeing how it works.

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What I'd like to do is show you the scanner first of all.

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-Have you seen it before?

-No, I haven't.

-Shall we've a look inside?

-OK.

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It's got a big metal door because it's housed in a big metal cage.

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This is the scanner.

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You'll be going in with your head in the scanner

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and it's got a very strong magnetic field which is part of the way it works.

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Karen's going to show us how strong the magnet is.

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-She's actually got...

-I've got a spanner on the end of a bit of rope.

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You can see how powerful it is. So that's how strong it is.

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Quite impressive that, actually, isn't it?

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-Wow. Iain, can you hear me?

-Yes, hi, good evening.

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We've just seen this magnet of yours.

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It's extraordinarily powerful. How powerful is it?

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30,000 times as strong as the magnetic field of the Earth.

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That sounds dangerous to me. Why doesn't it affect the human brain

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when you put someone in a scanner?

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Well, the magnet's actually fixed.

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It doesn't move, there's no movement,

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so it's safe to go in and use for imaging.

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So it's not like the TMS. It's a static magnetic field.

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-Is that correct?

-It's a static magnetic field, so it's safe.

-OK.

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-Thalia, can you hear me?

-Yes, I can, Bruce. Hello.

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I wouldn't go into that machine with anything magnetic.

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Have you got something small that you can put in your hand?

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-I do. I've got a walnut.

-You've got a walnut? All right.

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Well, I want you to take the walnut into the scanner, OK,

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and don't tell us which hand you're going to put it in

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because were we're going to do a bit of mind reading, I think.

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We'll be seeing a bit more of you later on. Or, should I say, we'll be seeing more of your brain.

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For the moment, though,

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can we give a warm round of applause to Thalia and Professor Iain Lyburn.

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APPLAUSE

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So all brains work by electrical signalling

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and all brains are very similar but they can also be quite different, in some ways.

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Take a look at all of these animal brains.

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Take a guess at which brain you think this animal belongs to.

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I'm going to give you a pound coin so you can estimate the size.

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-Now, what animal do you think that might be? Shout it out.

-Spider!

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A spider?

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-No, it's not a spider. Can we have another example?

-Mouse!

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Mouse? Who said mouse? Hands up. You're correct. It's a mouse.

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OK, what about this creature here?

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Rat.

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Did someone say rat?

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AUDIENCE CALL OUT

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It's a rat's brain. What about this brain here?

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AUDIENCE CALL OUT

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It's a...it's a chicken. Believe it or not, that's a chicken's brain.

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And what about this one here?

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AUDIENCE CALL OUT

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A tortoise? No. No.

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AUDIENCE CALL OUT

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It's a cat's brain. And here we have... a dog.

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And finally this one. What's this one belong to?

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AUDIENCE CALL OUT

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A horse. Who said a horse?

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Hands up if you said horse.

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Let's consider the horse for a moment.

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It's a very large animal, isn't it? A horse is on average three times bigger than a human

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but look at the horse's brain in comparison to the human brain.

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Let me take it around to show you.

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Even though a horse is much larger than a human,

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the brain is actually smaller

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so this shows you the size of the body size

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doesn't predict the size of the brain.

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In fact, if you think about the size of a human body on average,

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our brain is seven times larger than you would ever imagine.

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So, who would like to hold a human brain?

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That's an awful lot of you.

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Unfortunately, we can't let you hold the human brain

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but I just happen to have one which is just as good,

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made out of synthetic plastic over here.

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It's a very good copy.

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It's the same shape, it's the same size and it's the same weight.

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So, would you like to hold the human brain?

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Who wants to halt the human brain. You do? Put your hands out.

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-What's the first thing you notice about it?

-It's quite heavy.

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It extraordinarily heavy, isn't it? It's about one half pounds.

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You can pass it along.

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One and a half kilos, I should say. OK.

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It's really quite heavy.

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What else is it? What else do you notice about it?

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Let me tell you.

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Can I have my brain back? Thank you.

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The brain, as you can see,

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is made up of two halves and each half is called a hemisphere.

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The interesting thing about the hemisphere is it controls

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the opposite side of the body, so if you remember

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when we were stimulating Vince's brain

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with the trans-magnetic stimulator,

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when I was activating his left side of the brain,

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it was his right hand which was being affected.

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Now, we don't really know why the brain is organised like that.

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It's a little bit of a mystery.

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In fact, you probably wouldn't be aware

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unless you've got some damage on the opposite side and you noticed the behaviour was affected.

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The other thing about the brain which I think is quite fascinating

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is all these folds and creases

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because all brains have this to some extent

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but if you look at the example of the mouse brain or the rat brain,

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they're really quite smooth.

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In the human, these folds and creases are quite pronounced

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so why is that?

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To get an answer for that, you really have to zoom in

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to the building blocks of the brain

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to a special kind of cell called a neuron and here we have

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the image of a neuron and as you can see

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it looks like a kind of strange alien creature from outer space

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and there's a lot of them.

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There are about 100 billion neurons in the average brain.

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And all these tentacles are dendrites

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and this is the way neurons are communicating with each other,

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by sending electrical impulses.

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Each neuron typically has one very thick connecting fibre

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called the axon and it's the axon that sends out information

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to connect up with all the others.

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Now, it turns out that the neurons

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and the connections which are related to those things we consider

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intelligence and being clever, they're not throughout the brain.

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They're concentrated in just the outer layer of the brain,

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a layer that's only 3-4 millimetres thick.

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We call this the cortex.

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The cortex comes from the Latin word for bark.

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So it's this outer layer with all these connections which make us

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very clever and flexible in our thinking.

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So it's not so much the size of the brain that's important.

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Rather, it's the surface area of the cortex

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and how big that is that allows for all these connections.

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If you take the human brain and flatten it out,

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it would have this degree of surface area.

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Would you hold my brain for a moment?

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OK, so this is how big the human cortex is if you flatten it out.

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That's a very big area, so how do you get all that inside a normal head?

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Well, here's nature's solution.

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It's all folded up.

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So nature has come up with an answer

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for, basically, an engineering problem.

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Thank you very much.

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Now, if it wasn't all folded up like that,

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then your head would have to be half as big again, which is not a good look

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and, for any mothers watching, it's bad enough giving birth

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to a baby of a normal sized head without it being any larger.

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OK, so let's now consider some other animals. Look at these little guys.

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They're quite exotic, aren't they?

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Does anyone know what they are? They're jellyfish, that's right.

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They're Australian Blubber Jellyfish

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and you can see them moving around in the pool.

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So what's so special about the brain of a jellyfish?

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Would anyone like to answer?

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-Sir?

-Is it transparent?

-That's a good answer.

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-Anything else? Yes?

-It doesn't have one?

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It doesn't have one. Well done.

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A trick question. They do have a central nervous system

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but they don't really have a brain as such.

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So if jellyfish don't have brains,

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then why do all these other animals have brains?

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Why do you think we have a brain in the first place?

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Who would like to answer? Yes.

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Because otherwise we wouldn't be alive?

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Otherwise we wouldn't be alive, that's good. Any more answers?

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-Yes?

-Memory.

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These are all great answers but the basic answer for all the animals

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which have brains is that we use brains to navigate around the world.

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The jellyfish can move

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but it's not keeping track of where it's going and jellyfish

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tend to go with the ebb and flow of the tides whereas animals that have

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brains are using them to navigate their world, to find food,

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to seek mates, to avoid predators

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and to keep track of where they're going

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in order to plan their movements in the world.

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So brains are for figuring out and predicting what's going to go next.

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If you think about it, an animal, or an animal like us,

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is really a kind of complex mobile moving factory made up of many subdivisions,

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different processing plants, recycling centres

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and movement machinery, and that all has to be coordinated.

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If it wasn't, we'd fall apart

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so brains are really for controlling all these different activities.

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Now some of these activities are fairly automated.

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For example, breathing and hearts are controlled by the brainstem

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which is below the cortex, so it doesn't require a lot of consciousness.

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And other things like your movements that you've learnt well, you don't have to think about them.

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Even walking. You know where you're going and you can plan that, but coordinating the movements,

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you don't have to think about that.

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And that's controlled by the cerebellum at the bottom here.

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So whether they're automatic or controlled,

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the whole point is they still need to be coordinated by a system

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and that's what the cortex does, sitting up here.

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So the information is flooding up into the brain

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through the central nervous system.

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The information from the most extreme parts, for example the arms

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or even the legs, they form part of the peripheral nervous system.

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So how fast does a nerve impulse travel?

0:18:120:18:14

Well, we're going to try a little experiment. We're going to measure the speed of a nerve impulse

0:18:140:18:18

travelling the length of one arm and I'm going to need some volunteers.

0:18:180:18:22

In fact, I'm going to need all of Row E, so stand up, row E.

0:18:220:18:27

Big round of applause.

0:18:270:18:29

APPLAUSE

0:18:290:18:32

-What's your name, sir?

-My name's Omar.

-Omar?

-Yep.

0:18:360:18:39

-OK, Omar, and who do we have at the end?

-Tim.

-Hello, Tim.

0:18:390:18:43

Omar, what I'm going to do is I'm going to grip your left shoulder with my right hand

0:18:430:18:47

and with your right hand, you grip the left shoulder

0:18:470:18:50

and everyone copy everyone so you form a chain reaction.

0:18:500:18:52

OK. Are you all holding? Right.

0:18:520:18:55

What I'm going to do is I'm going to squeeze your shoulder gently and everyone do it gently.

0:18:550:19:00

When you feel your shoulder being squeezed, and not before,

0:19:000:19:03

you squeeze your neighbour's shoulder, so it's going to pass the entire length of Row E.

0:19:030:19:07

OK? And Tim at the end, when you feel your shoulder being squeezed,

0:19:070:19:10

you shout stop because we're going to measure the speed,

0:19:100:19:14

the time it takes for that response to travel the full length of Row E.

0:19:140:19:18

You got it?

0:19:180:19:19

So let's go.

0:19:190:19:22

-Stop.

-OK, that's pretty good. That's 3.10 seconds.

0:19:240:19:28

Let's see if you can get a bit faster. All right, ready again?

0:19:280:19:32

-Stop.

-OK, that's just under three seconds. That's pretty good. You are getting better with practise.

0:19:360:19:41

Now, this time I don't want you to grip the shoulder.

0:19:410:19:44

I want you to hold hands. You should be even faster now, shouldn't you?

0:19:440:19:48

Squeeze your neighbour's hand when you feel your left hand is squeezed

0:19:480:19:51

and, again, Tim, you shout stop when you feel that.

0:19:510:19:54

OK, ready?

0:19:540:19:55

Stop.

0:19:590:20:00

That's three seconds, almost a full second longer.

0:20:000:20:05

Now, why does it take longer for the nerve impulse to travel the full distance?

0:20:050:20:09

If you think about it, the first time we did it

0:20:090:20:11

it's only travelling the length of one arm.

0:20:110:20:14

But when we're holding hands,

0:20:140:20:15

it has to travel the length of one arm plus an extra arm to the person next to you.

0:20:150:20:20

An arm is almost a metre long, isn't it?

0:20:200:20:23

And with 15 arms, that's an extra 15 metres it has to travel

0:20:230:20:27

in just under about a second, so it's somewhere between 10 and 15 metres per second,

0:20:270:20:31

which is about right for that kind of nerve impulse.

0:20:310:20:33

So, a big round of applause for row E.

0:20:330:20:35

APPLAUSE

0:20:350:20:39

So, we were estimating the speed of a nerve impulse in the arm,

0:20:410:20:44

and it's usually roundabout that kind of speed,

0:20:440:20:47

and that's usually a lot slower than people imagine,

0:20:470:20:50

because when you think about nerve impulses we often assume

0:20:500:20:53

they must be almost as fast as electricity,

0:20:530:20:56

because it seems like it is an electrical impulse.

0:20:560:20:58

But, in fact, electricity travels about three million times faster than a nerve impulse.

0:20:580:21:04

So, we've been using these sorts of experiments to try

0:21:040:21:07

and estimate how the brain is working,

0:21:070:21:10

but can you ever really measure directly nerve activity?

0:21:100:21:13

Remarkably, you can if you're an expert and you know what you're doing,

0:21:130:21:17

and you happen to have a very thin wire.

0:21:170:21:19

So, would you give a warm welcome to two experts from Newcastle,

0:21:190:21:22

Dr Claire Rind and Dr Peter Simmons.

0:21:220:21:25

APPLAUSE

0:21:250:21:29

So, Claire, I believe you've had some interesting travelling

0:21:350:21:39

companions with you, is that right?

0:21:390:21:41

We have, we've come down on the train with a box full of locusts.

0:21:410:21:44

Oh, right. So these are live locusts?

0:21:440:21:48

Yes, they're all munching on the grass,

0:21:480:21:51

there's about six of them in there, varying sizes.

0:21:510:21:54

So he's gently being placed on his back, is that right?

0:21:540:21:57

Yes, in a little bed of Plasticine - it's actually a she -

0:21:570:22:02

lying on her back in a bed of Plasticine

0:22:020:22:05

and we've restrained the animal with little loops of Plasticine,

0:22:050:22:10

and Peter is putting a very fine wire into its chest.

0:22:100:22:15

The wire is rather like an acupuncture wire, very fine,

0:22:150:22:19

-just a small diameter wire.

-So it doesn't hurt the locust at all?

0:22:190:22:23

-No, not at all.

-That's amazing.

0:22:230:22:25

Whilst Peter is setting up, because this is a very delicate procedure,

0:22:250:22:29

let me tell you a little bit about the locust.

0:22:290:22:32

The locust is really a giant kind of grasshopper, and it has this

0:22:320:22:36

very simple nervous system for avoiding bumping into things.

0:22:360:22:40

The reason it needs to do this is

0:22:400:22:42

because when they get large in numbers they can become swarms,

0:22:420:22:46

which are travelling in their vast numbers,

0:22:460:22:48

and there's literally millions of them,

0:22:480:22:50

and they can fly without bumping into each other.

0:22:500:22:53

Swarms can be a real problem, because when they land on a crop

0:22:530:22:57

they'll just ravish a crop and eat it within minutes.

0:22:570:23:00

So, they are usually a pest to humans,

0:23:000:23:02

but they've also been very helpful because we can measure their brain activity without hurting them.

0:23:020:23:08

This is what you've been doing in your research, is that right?

0:23:080:23:11

Yes, we've been looking at particular nerve cells

0:23:110:23:15

within its nervous system and using this recording equipment

0:23:150:23:19

to record electrical activity that the nerve cells make.

0:23:190:23:23

In fact, the noise that you'll hear eventually is from

0:23:230:23:27

a single nerve cell within the locust's nerve system.

0:23:270:23:31

It's a very important neuron,

0:23:310:23:33

one of the biggest in the body of the locust,

0:23:330:23:38

and it communicates down to the wings

0:23:380:23:40

and can actually shut off the flight cycle

0:23:400:23:43

so that the locust will make a dive and avoid a predator

0:23:430:23:47

or adjust its flight to avoid another member of the swarm.

0:23:470:23:51

OK, so, Peter, are we ready?

0:23:510:23:53

We're ready, I think she's ready, as well.

0:23:530:23:56

I couldn't tell the difference, but I presume they're larger, the females?

0:23:560:24:00

The female's larger, yes.

0:24:000:24:02

OK, so which part of the visual field are we going to be recording from?

0:24:020:24:06

We're recording from the right side of the locust,

0:24:060:24:09

but it's the eye that is looking towards the left,

0:24:090:24:13

she's on her back, so she's watching you.

0:24:130:24:16

-She's watching me now?

-She's watching you now.

0:24:160:24:18

-Right, so we're going to listen in to her responding to me, is that correct?

-Yes.

0:24:180:24:23

Let's have some silence, listen very carefully,

0:24:230:24:26

what you'll be hearing is the activity of the neurons.

0:24:260:24:30

STATIC CRACKLING IN TIME WITH HAND MOVEMENTS

0:24:300:24:35

Can you hear that?

0:24:350:24:36

Do you realise you are listening to the brain of a locust?

0:24:390:24:44

We know it's from that side because if I come from the other side...

0:24:440:24:50

..you don't get the effect.

0:24:530:24:54

Whereas, actually, I think she's paying quite a lot of attention to me now, isn't she?

0:24:540:25:00

That is absolutely fascinating. Shall we try with this?

0:25:020:25:06

This represents another large locust flying in the swarm towards it.

0:25:060:25:10

RYTHMIC CRACKLING

0:25:100:25:14

That's great.

0:25:140:25:16

So, tell me, Claire, with this research what have you been able to do?

0:25:160:25:19

Does it have any application for humans at all?

0:25:190:25:22

It's a fascinating circuit the locust has and we've built

0:25:220:25:25

an artificial circuit that we've been able to put into a sensor

0:25:250:25:31

that is used for collision avoidance in cars,

0:25:310:25:34

so we're hoping in the future that the circuits based on the locust

0:25:340:25:38

will be able to help drivers avoid collisions in traffic.

0:25:380:25:43

So, the locust insect is helping humans to avoid pileups on the M1?

0:25:430:25:47

Eventually, that's what we think.

0:25:470:25:49

Well, I think that's very useful.

0:25:490:25:51

Can you release the locust to just show everything is fine with her?

0:25:510:25:54

Can we get a close-up of the locust, just to show you?

0:25:560:25:59

We can't let go because if she gets the chance she'll run away.

0:25:590:26:02

You can see there she's perfectly OK.

0:26:020:26:05

-And she bit me.

-That's revenge, she's getting her own back, Peter.

0:26:050:26:08

Let's put her back with her friends and let them go.

0:26:080:26:12

Can we have a big round of applause for the locust...

0:26:120:26:15

APPLAUSE

0:26:150:26:16

...and Peter and Claire. Thank you so much for coming down.

0:26:160:26:20

That was fascinating,

0:26:270:26:29

but can we ever do the same thing for a human?

0:26:290:26:31

Well, we chose a volunteer earlier, and this is Billy.

0:26:310:26:34

He can't talk to us at the moment because we have him wired up.

0:26:340:26:38

We're not sticking an electrode in his brain,

0:26:380:26:41

rather we're recording from the outside, because it turns out

0:26:410:26:45

that, if you have lots of neurons firing, they generate enough

0:26:450:26:48

electrical activity that we can detect it with tiny electrodes.

0:26:480:26:51

Normally when scientists do this, they have lots of electrodes,

0:26:510:26:55

but for tonight's purposes we're just interested in the back of Billy's head,

0:26:550:27:00

because this is where his visual area is,

0:27:000:27:02

the visual cortex in the human.

0:27:020:27:04

So, as before, we saw the locust was looking at a human - me -

0:27:040:27:08

approaching the locust, this time we're presenting a locust

0:27:080:27:11

to a human to see how they respond.

0:27:110:27:13

And here we see this big pattern starting to build up.

0:27:130:27:16

This is the response of Billy's visual area. Thank you, Kate.

0:27:160:27:21

As you can see, as the locust was coming on it was responding,

0:27:210:27:25

so the picture of the locust was generating activity in his eyes,

0:27:250:27:29

then sending these impulses along the optic fibre

0:27:290:27:31

to the back of the brain where the visual processing area is, then responding to that.

0:27:310:27:36

That's the onset of the pattern, when the locust first appears,

0:27:360:27:40

and this is the rest of the brainwave, showing how he processes it.

0:27:400:27:43

So, Billy, it turns out that you do have a brain,

0:27:430:27:45

so thank you very much and a big round of applause to Kate and Billy.

0:27:450:27:50

APPLAUSE AND CHEERING

0:27:500:27:53

Animals might be all moving and interacting in the same environment,

0:27:530:27:58

like the locusts and humans, but their brains are very different,

0:27:580:28:02

and what they're experiencing must be different.

0:28:020:28:05

And even our own experience is often not what it seems.

0:28:050:28:09

So, consider vision again.

0:28:090:28:11

Most of us think that vision is rich and full of detail -

0:28:110:28:15

in fact, a lot of us think it's almost like a camera, but is it really?

0:28:150:28:18

Let's test that idea out. Joe, would you come in here?

0:28:180:28:22

Joe's got a camera on his shoulder and he's taking the image

0:28:220:28:26

and you can see that the image is projected above me

0:28:260:28:29

and it's nice and rich and full of detail.

0:28:290:28:31

This is what we think vision is really like,

0:28:310:28:34

but, actually, human vision isn't like that at all,

0:28:340:28:37

because we know from the studies using these techniques

0:28:370:28:40

you're only ever processing the centre part of your vision,

0:28:400:28:43

and in fact it's about the size of your thumb held at arm's length.

0:28:430:28:46

So, can we make the camera appear like human vision?

0:28:460:28:50

Now you can see it's all blurred at the edge

0:28:500:28:52

and it's only the central part of the field which is clear and detailed.

0:28:520:28:56

That's a bit strange, because that's not the way you experience vision, do you?

0:28:560:29:01

You see it as full and complex.

0:29:010:29:03

So, why is that? Well, let me show you.

0:29:030:29:07

If I move a bit closer...

0:29:070:29:09

the way that it seems more detailed is, of course,

0:29:090:29:12

I simply move my eyes around.

0:29:120:29:15

And I'm moving them quite rapidly, about four or five times per second.

0:29:150:29:20

These are called saccades.

0:29:200:29:21

This is how the brain builds up a picture of complexity,

0:29:210:29:24

because you're sampling the world

0:29:240:29:26

then storing that information, and the brain is remembering it,

0:29:260:29:30

and this is what makes the world seem much more complex.

0:29:300:29:33

There's a problem, though,

0:29:330:29:35

because if a camera was to move like human vision,

0:29:350:29:38

there'd be a real distortion, so let's take that away.

0:29:380:29:41

Joe, can you move your camera like an eye movement?

0:29:410:29:44

Let's see what that looks like.

0:29:440:29:46

Now, what's wrong with that? Any suggestions? Yes.

0:29:550:29:59

-AUDIENCE MEMBER:

-It's kind of moving quite fast.

0:29:590:30:01

It's very jerky, isn't it? It's very blurred.

0:30:010:30:04

If that was your normal vision it'd make you very seasick,

0:30:040:30:07

so your brain does a very clever trick.

0:30:070:30:10

Every time you move your eyes it cuts out the visual information,

0:30:100:30:14

so you don't see all those jerky, smeared, blurred images.

0:30:140:30:17

So, Joe, can you simulate that, can you turn off the visual signal

0:30:170:30:21

every time you're moving the camera?

0:30:210:30:23

OK, your brain is literally cutting off all the visual information, in fact you can't see anything.

0:30:290:30:35

We know that's true, I'm going to prove it and I'll need a volunteer.

0:30:350:30:39

Let's see who we can choose. Do we have anyone? Young lady.

0:30:390:30:42

-What's your name?

-Amy.

0:30:420:30:44

Amy, OK, would you hold the mirror like this, OK?

0:30:440:30:47

Josh, can you pick up Amy? Good.

0:30:470:30:49

Now, Amy, have a look at your left eye.

0:30:490:30:52

Now look at your right eye.

0:30:520:30:54

Swap backwards and forwards.

0:30:540:30:56

-Can you see your eyes moving?

-No.

0:30:560:31:00

Can you see your eyes moving at all?

0:31:010:31:04

-Can anyone else see her eyes moving?

-AUDIENCE:

-Yes.

0:31:040:31:06

Amy, your eyes are moving, would you like me to prove it to you?

0:31:060:31:10

Have a look up there.

0:31:100:31:12

Ready?

0:31:120:31:14

LAUGHTER

0:31:170:31:19

It would seem like you're surprised, but don't worry,

0:31:190:31:22

you're perfectly normal, you can't see your own eyes moving at all.

0:31:220:31:25

Applause for Amy, please.

0:31:250:31:28

APPLAUSE

0:31:280:31:31

Now, you can try that all at home, actually.

0:31:330:31:36

If you're brushing your teeth, just look in the mirror

0:31:360:31:39

then focus on your left eye and shift to your right eye,

0:31:390:31:42

see if you can see your eyes moving, and you won't be able to,

0:31:420:31:45

because, no matter how you try, your brain is making you blind.

0:31:450:31:48

Effectively, if you add up all the gaps - you're moving your eyes all the time when you're awake -

0:31:480:31:54

you're blind for about two hours of the day, and you never even know that. Isn't that remarkable?

0:31:540:31:59

Clearly the mind has amazing tricks that keep the world looking

0:31:590:32:03

rich and full of detail and information.

0:32:030:32:06

So, what happens to all that information once you've detected it?

0:32:060:32:09

Ice creams! Get your ice creams here! Ice creams!

0:32:090:32:12

Ah, here's some rich information - an ice cream. Thank you very much.

0:32:120:32:16

So, consider an ice cream. It's full of lots of information.

0:32:160:32:22

It looks delicious, it smells delicious, I'm going to do this...

0:32:220:32:27

You can hear the crunch, it's cold, and it tastes very yummy,

0:32:280:32:34

but somehow my brain combines all these different sensations

0:32:340:32:38

into one experience a delicious ice cream.

0:32:380:32:41

How does it do that?

0:32:410:32:42

I'm going to show you by building a very simple brain in this auditorium.

0:32:420:32:48

OK, we had some helmets given out earlier, so pop your helmets on.

0:32:480:32:52

Those with the helmets, would you mind standing up?

0:32:520:32:56

these are our volunteers.

0:32:560:32:58

You're going to represent different groups of neurons.

0:32:580:33:01

Let's say this part of the brain is coding for shapes.

0:33:010:33:05

Sir, at the back, you code for anything which is round.

0:33:050:33:08

And you in the front code for anything which is long, like a pencil.

0:33:080:33:11

This part of the audience will represent the part of the brain

0:33:110:33:15

which codes for colour, so you're going to be green,

0:33:150:33:18

and you're going to respond to anything that's yellow.

0:33:180:33:21

And over here we have a part of the brain which codes for taste,

0:33:210:33:24

so you're getting information from the mouth, and you at the back,

0:33:240:33:28

you're going to be sweet and you're going to be salty.

0:33:280:33:31

Now hold-up these connections, because these are going to stand

0:33:310:33:35

for all the connections between the different regions of the brain.

0:33:350:33:40

Now press your buttons and let's see all the activity in the brain sending signals.

0:33:400:33:44

You can flash them, let's see a lot of random connections.

0:33:440:33:47

So here's our simple brain. How does a simple brain learn about objects?

0:33:470:33:51

Well, we're going to teach it to learn about fruit.

0:33:510:33:54

OK, so pop your lights off for a moment.

0:33:540:33:58

Now, imagine that you've never eaten a banana before.

0:33:580:34:01

So, let's have you responding, if your feature's present, hold down your button.

0:34:010:34:05

Let's see what that looks like.

0:34:050:34:07

So it's long, it's yellow,

0:34:070:34:09

and you pop it in your mouth and what does it taste like? Sweet.

0:34:090:34:12

Sweet. So that's the pattern for a banana.

0:34:120:34:15

All right, now everyone switch your lights on again,

0:34:150:34:19

communicating again, there it's talking to itself, and put them off.

0:34:190:34:23

Let's come across another fruit.

0:34:230:34:26

This time, it's round, hold it down...

0:34:260:34:29

it's green...

0:34:290:34:31

and you pop it into your mouth and it's sweet.

0:34:310:34:34

And every time you eat a banana, or a grape,

0:34:360:34:39

that pattern becomes stronger.

0:34:390:34:41

This is because the neurons that fire together are wiring together.

0:34:410:34:45

Now, you might notice how the banana and the grape

0:34:450:34:50

are activating the same part, which is the sweet centres.

0:34:500:34:53

That shows you the brain can reuse the same regions

0:34:530:34:56

to code for different objects.

0:34:560:34:57

So, what happens when you go to a new part of the world

0:34:570:35:01

and encounter new food you've never had before?

0:35:010:35:04

Turn your lights off for a moment.

0:35:040:35:06

Let's say you go to the Mediterranean

0:35:060:35:08

and you see this small, round, green thing.

0:35:080:35:11

So it's round, it's green, and your brain thinks,

0:35:110:35:15

"Well, it looks like a grape, so it's going to be sweet."

0:35:150:35:18

So, sweet, pop your light on.

0:35:180:35:20

But then when you pop it into your mouth...

0:35:200:35:23

Yuck! It's salty!

0:35:230:35:26

So, this is why you can be very surprised

0:35:260:35:28

when you encounter something new which seems so familiar.

0:35:280:35:31

That's why new foods can surprise you.

0:35:310:35:35

Let's consider our simple brain again.

0:35:350:35:38

If I show you this pattern...

0:35:380:35:41

Tell us, audience, what do you think that stands for, that pattern?

0:35:410:35:45

AUDIENCE: Banana.

0:35:450:35:47

It stands for banana, but it's not really a banana, is it?

0:35:470:35:51

It's just how the brain recreates the sensation of eating bananas.

0:35:510:35:54

It's what we call a representation,

0:35:540:35:57

because the brain is re-presenting the original experience.

0:35:570:36:01

Representations are really the language of the brain.

0:36:010:36:04

Now, I have given you a very simple demonstration with only a few groups of neurons,

0:36:040:36:09

just to give you an idea of different patterns,

0:36:090:36:11

but the brain is much more complex.

0:36:110:36:13

If this were a real brain, there'd be 100 billion neurons,

0:36:130:36:17

and you wouldn't just be holding a couple of connections,

0:36:170:36:20

because the neurons have up to 10,000 connections between them,

0:36:200:36:24

and if you add up all the connections end to end,

0:36:240:36:26

that stretches to 180,000 kilometres,

0:36:260:36:30

and that's long enough to stretch around the world four times.

0:36:300:36:33

That's rather mind blowing, isn't it?

0:36:330:36:35

Because it means your brain has the capacity to encode an almost

0:36:350:36:38

infinite number of patterns, which is why we say the human brain

0:36:380:36:42

is the most complex structure to be found in nature.

0:36:420:36:45

So, let's have a big round of applause for our small brain.

0:36:450:36:49

APPLAUSE

0:36:490:36:53

So, our world is full of rich experiences that are combined into these meaningful patterns,

0:36:540:36:59

and these representations reflect all the structure and order

0:36:590:37:03

that we encounter on a regular basis in our existence, in our lives.

0:37:030:37:08

So, for example, if I have this garbage lid,

0:37:080:37:11

you're processing this in different parts of your brain.

0:37:110:37:14

You have a areas which are processing the vision,

0:37:140:37:17

and if I drop it...

0:37:170:37:19

you have areas of your brain processing the sound.

0:37:190:37:22

So your visual area's active, and so are your sound areas.

0:37:220:37:25

In fact, you've got a set of neurons which combine that experience of sight and sound.

0:37:250:37:30

This representation of sight and sound is usually quite reliable,

0:37:300:37:33

because sights usually go with sounds, but sometimes

0:37:330:37:36

it can lead you to some false and surprising conclusions.

0:37:360:37:40

BELCHING SOUNDS

0:37:420:37:45

Let's try that one more time.

0:37:450:37:48

BELCHING SOUNDS

0:37:480:37:50

So, what you're doing there is you think that the skull is burping,

0:37:500:37:54

but of course he isn't really, what's happening

0:37:540:37:57

is you're seeing the skull move and you're hearing the sound

0:37:570:38:01

and your brain's readily putting those things together.

0:38:010:38:04

This is called the ventriloquist effect.

0:38:040:38:06

And so, when people see ventriloquists they think they're throwing their voice,

0:38:060:38:10

but they're not really throwing their voice,

0:38:100:38:13

they're minimising the movement of their own mouths,

0:38:130:38:16

making a sound, and exaggerating the mouth of the puppet.

0:38:160:38:19

I can do that for a little bit, let's see if I can try

0:38:190:38:22

and convince you this skull is talking,

0:38:220:38:24

So if I go, she sells seashells on the seashore.

0:38:240:38:29

OK.

0:38:290:38:30

Not only does a ventriloquist shape where you think a sound's coming from,

0:38:300:38:35

because sights and sounds usually come from the same place,

0:38:350:38:38

the ventriloquist effect can also influence what you're hearing.

0:38:380:38:42

So, in this next example, I want you to watch very carefully

0:38:420:38:45

this little bit of video and see if you can hear what I'm saying.

0:38:450:38:49

REPEATS EITHER "BA-BA! OR "DA-DA"

0:38:510:38:55

What did you hear?

0:38:550:38:57

AUDIENCE GIVES A MIXED RESPONSE

0:38:570:39:00

Who heard "da-da", put your hand up?

0:39:000:39:03

OK, everybody sitting in the middle. Let's try it again.

0:39:030:39:06

REPEATS EITHER 'BA-BA' OR 'DA-DA'

0:39:060:39:10

What do you hear? "Da-da?"

0:39:100:39:12

Middle section only, what did you hear?

0:39:120:39:14

"Da?" "Ba?"

0:39:140:39:16

MIXED RESPONSE

0:39:160:39:18

All right, let's make this easier.

0:39:180:39:20

I want you to listen again, but close your eyes, OK?

0:39:200:39:24

REPEATS EITHER "BA-BA" OR "DA-DA"

0:39:260:39:30

What did you hear this time?

0:39:300:39:32

AUDIENCE: "Ba".

0:39:320:39:33

Definitely it was "Ba".

0:39:330:39:34

If you heard "da" you were being fooled by an illusion called the McGurk effect,

0:39:340:39:39

because I'm not actually mouthing "ba-ba" or "da-da",

0:39:390:39:42

what I'm mouthing is "ga-ga".

0:39:420:39:45

So the brain gets the signal of "ga", and it's hearing "ba",

0:39:450:39:48

but these are patterns it's never encountered before,

0:39:480:39:51

and it comes up with a solution which is "da".

0:39:510:39:54

So your brain's always trying to interpret experiences

0:39:540:39:58

to come up with the best solution.

0:39:580:40:00

Now, this way when you're watching people speak,

0:40:000:40:03

you watch their mouths moving and the shape of their mouths

0:40:030:40:06

can influence what you think you're hearing.

0:40:060:40:08

Here's a very simple party trick -

0:40:080:40:10

I want you to turn to the person next to you

0:40:100:40:13

and mouth the words "elephant juice". Don't say it, just mouth it.

0:40:130:40:17

Turn to the person next to you.

0:40:170:40:19

What does it sound like? What do you think the person might be saying?

0:40:230:40:27

Why are you laughing?

0:40:270:40:30

OK, OK.

0:40:300:40:32

Does it look like they could be saying "I love you"?

0:40:320:40:35

Do I hear "I love you"?

0:40:350:40:37

I love you all, wouldn't the world be a greater place

0:40:370:40:40

if everyone said "elephant juice" a little more often to each other?

0:40:400:40:45

OK, so your brain is not just forming representations

0:40:450:40:50

of the outside world, it's also storing these representations of your own bodies,

0:40:500:40:55

and so for this next demonstration I'm going to require someone

0:40:550:40:59

who doesn't mind losing their hand.

0:40:590:41:01

Lady on the end here, why don't you come down?

0:41:020:41:06

APPLAUSE

0:41:060:41:10

It's all right, just there. What's your name, first of all?

0:41:100:41:14

-Josie.

-Josie, so you're quite prepared to lose your hand

0:41:140:41:18

for medical science, is that correct? You don't mind losing a hand?

0:41:180:41:22

Don't worry, I'm not going to remove your hand,

0:41:220:41:24

I'm going to create the illusion that you're losing your hand.

0:41:240:41:28

So, for this I need you to put on this very strange jacket.

0:41:280:41:31

It's actually got three arms.

0:41:310:41:33

OK, so put your arm through that one, then through the other one.

0:41:330:41:37

That's the regular part of the jacket.

0:41:370:41:39

Is that going to be a bit small for you? Perfect.

0:41:390:41:42

-Now, we're going to torture you. OK, so now, Josie, did you say?

-Yes.

0:41:420:41:46

OK, Josie, take a seat. I want you to put your other hand

0:41:460:41:49

up here, your left hand, both hands are there.

0:41:490:41:52

OK, now, that looks a little bit strange,

0:41:520:41:55

but I want you just to focus on this, this is a rubber hand.

0:41:550:41:59

It's about the same size as Josie's hand, and I want you

0:41:590:42:02

not to look at the audience, just concentrate on the hand, OK?

0:42:020:42:05

This illusion takes about a minute or two to form.

0:42:050:42:09

What should happen is that Josie is looking at this hand of hers,

0:42:090:42:13

and it's in the same place her normal hand is.

0:42:130:42:16

So, her brain is a little bit confused, because that hand should belong to her.

0:42:160:42:22

At the same time, to make the illusion even more strong,

0:42:220:42:25

Kate is simultaneously stroking the hands,

0:42:250:42:28

so the brain is now receiving all this touch information.

0:42:280:42:32

Again, it's combining information, trying to make sense of it.

0:42:320:42:36

-How does that feel?

-It feels really weird.

0:42:360:42:39

-Does it feel very weird?

-Yeah.

-OK.

0:42:390:42:42

So, just keep doing that for a moment.

0:42:420:42:44

Now just keep focusing on the hand, OK?

0:42:490:42:53

Ready?

0:42:530:42:54

Did you get a strange... Did that feel a bit odd?

0:42:550:42:58

OK, don't worry, I wasn't going to hurt your hand.

0:42:580:43:00

Round of applause.

0:43:000:43:02

APPLAUSE

0:43:020:43:06

Thank you very much. Well done.

0:43:100:43:12

Now, the reason that happened is because the brain wasn't

0:43:120:43:15

exactly sure whether it was the rubber hand any more,

0:43:150:43:18

and that's why most people you do that experiment with get this surprise.

0:43:180:43:22

I can't bring you all down to try the rubber hand illusion,

0:43:220:43:26

but I can show you a similar experience,

0:43:260:43:28

so I'll need another volunteer, someone from this side.

0:43:280:43:31

Young lady in the blue, why don't you come down?

0:43:310:43:33

APPLAUSE

0:43:350:43:38

-What's your name?

-Charlotte.

0:43:380:43:40

OK, Charlotte, here's a very simple way to induce the rubber hand illusion.

0:43:400:43:44

I'm just going to turn you this way for a bit.

0:43:440:43:46

There you go, Charlotte. Now put up your right hand.

0:43:460:43:49

OK.

0:43:490:43:51

Now, with your other hand just grip like this.

0:43:510:43:55

Now, looking at your index finger, just move your fingers up and down whilst you're doing it.

0:43:550:44:00

-Does that feel a little strange? You can all try this.

-Yes.

0:44:000:44:03

Just turn to the person next to you.

0:44:030:44:06

With your thumb and forefinger see if you can do this.

0:44:060:44:10

It's strange, isn't it? It is very, very weird.

0:44:120:44:15

You can try it at home as well, if you like.

0:44:150:44:18

All right, guys, let's settle down.

0:44:240:44:27

Let's give a round of applause to Charlotte.

0:44:270:44:30

-APPLAUSE

-Thank you, Charlotte.

0:44:300:44:34

So, your brain is always trying to make sense of the world.

0:44:380:44:41

Sometimes, when it gets strange signals, it comes up with strange experiences and illusions.

0:44:410:44:46

We see things all the time. It might be faces in a cloud or animals in ink stains.

0:44:460:44:53

Just simple coffee beans.

0:44:530:44:55

If I scatter them onto here, you can see all sorts of patterns in that.

0:44:550:45:01

Can anyone see a pattern forming there at all?

0:45:010:45:05

Shout if you see anything.

0:45:050:45:07

There's a mouse?

0:45:070:45:09

SHOUTING FROM AUDIENCE

0:45:090:45:12

What else?

0:45:120:45:13

Oh...

0:45:150:45:16

AUDIENCE SHOUTS

0:45:160:45:19

OK.

0:45:190:45:20

So, you're all seeing lots of patterns. That's very good.

0:45:220:45:27

OK. Clearly you're all seeing lots of things. That's very reassuring.

0:45:270:45:31

Your brain always tries to impose structure and order.

0:45:310:45:34

This is most obvious with certain types of illusions

0:45:340:45:38

where you have patterns which can be seen in more than one way.

0:45:380:45:42

Probably one of the most famous examples is called The Necker Cube.

0:45:420:45:46

Here is a Necker Cube.

0:45:460:45:48

It is an outline of a cube. If you look at it long enough, you think it's pointing in one direction

0:45:480:45:53

but then, if you stare at it long enough, your brain switches

0:45:530:45:57

and it appears to be in the opposite direction.

0:45:570:46:01

Is anyone having that experience? Hands up.

0:46:010:46:03

That's great.

0:46:030:46:05

We can make it stronger if we put a bit of movement into it.

0:46:050:46:07

So just watch as it turns.

0:46:070:46:11

It seems to be going in one direction. Then, is anyone getting it turning in the other direction?

0:46:110:46:18

Yeah? Just watch. You know what makes it really good?

0:46:180:46:23

If you blink, while you're watching, you'll see it switch.

0:46:230:46:26

We're not using any computer trickery here.

0:46:260:46:30

It's simply your brain switching from one version versus the other.

0:46:300:46:34

Isn't that remarkable?

0:46:360:46:38

AUDIENCE MURMURS

0:46:380:46:40

Here is another interesting point.

0:46:400:46:42

Your brain doesn't allow you to see all the patterns at once.

0:46:420:46:47

It forces you into one perception versus the other.

0:46:470:46:50

This might explain why some of you sometimes see things like ghosts, for example.

0:46:500:46:56

I am going to conjure up a ghost in front of your very eyes, OK?

0:46:560:47:00

Don't worry, it won't be a headless horseman. It'll be more simple and friendly than that.

0:47:000:47:06

All you need for this,

0:47:060:47:07

and you can try this at home, are just four circles of paper.

0:47:070:47:11

It's such a simple illusion but it's very compelling.

0:47:110:47:14

All I have to do his cut a quarter of the circle.

0:47:180:47:22

If you then align up the circles...

0:47:290:47:32

..you will see something that isn't really there.

0:47:340:47:39

What does anyone see? Hands up. Shout out.

0:47:400:47:43

-AUDIENCE SHOUTS

-That's right. A square.

0:47:430:47:46

But, of course, there isn't a square there, is there?

0:47:460:47:49

When I take this away it disappears and back it comes again.

0:47:490:47:53

This is a very simple illusion, but it's also a very powerful one

0:47:530:47:57

because I think it explains one of the most important points about the brain.

0:47:570:48:02

If I went into the back of your brain with a wire, I could measure activity

0:48:020:48:08

of neurons which are firing as if they're really was a square there.

0:48:080:48:12

So this is remarkable - the brain is creating its own experience, isn't it?

0:48:120:48:18

In fact, we can even show that you think this is a solid object.

0:48:180:48:23

They've done this recently in an experiment

0:48:230:48:25

where they've put people in a brain scanner and they've showed them this square.

0:48:250:48:30

It's called the Kanizsa Illusion.

0:48:300:48:32

Here we have the square. Then they made the square move.

0:48:330:48:37

You see, it is travelling across.

0:48:390:48:43

Watch as it moves across the screen.

0:48:430:48:47

There it goes again. Undulating like a real object.

0:48:500:48:53

Isn't that very bizarre?

0:48:550:48:57

AUDIENCE MURMURS

0:48:590:49:03

It's moving across the screen. See if we can move it a bit faster.

0:49:030:49:08

There it goes, moving across the screen.

0:49:080:49:10

What's remarkable is that the movement areas of the brain are being activated

0:49:150:49:19

which are going in the same direction as the illusory ghostly square.

0:49:190:49:24

So, your brain doesn't allow you to have contact with reality.

0:49:240:49:28

It is generating reality the whole time.

0:49:280:49:31

It is quite remarkable.

0:49:310:49:33

Let us come back to Charlie and Iona, at the beginning.

0:49:330:49:37

Let's get them back in for the rest of the show.

0:49:370:49:40

Where are you? Come one down.

0:49:400:49:42

A big round of applause, please.

0:49:420:49:44

APPLAUSE

0:49:440:49:47

-So, guys, how are you enjoying the show so far?

-It is great.

0:49:500:49:53

Reality hasn't changed for you. You're still very tall, Charlie,

0:49:530:49:55

-and you're still A bit shorter, aren't you?

-Yes.

-Would you like to be taller than Charlie?

-Yes.

0:49:550:50:01

Well, with the RI Christmas show we can actually make that happen

0:50:010:50:05

so please follow Kate out of the room for a moment.

0:50:050:50:08

We will be seeing them very shortly.

0:50:080:50:11

Throughout the lecture tonight, we've been watching how reality is created by the brain.

0:50:110:50:17

And it uses past experiences to make sense of the world.

0:50:170:50:21

But things are not always as they seem.

0:50:210:50:25

Sometimes we can fool the...

0:50:250:50:28

Oh! Hello, guys.

0:50:280:50:30

There we go! Can you give a wave, Charlie.

0:50:300:50:32

-Charlie, that room seems a bit small, doesn't it?

-Yeah.

0:50:320:50:36

Maybe you should try going to the opposite corner.

0:50:360:50:40

-Iona, why don't you switch places?

-OK.

-OK.

0:50:400:50:42

Oh, my gosh! How did that happen? Switch places again.

0:50:440:50:49

Can you hold hands? Can you reach each other?

0:50:540:50:57

There we go.

0:50:570:50:59

Look, it's a giant and a smaller person.

0:50:590:51:02

OK. You can have the bit of fun in there because I'll explain what's going on.

0:51:030:51:07

To do that, I need a model.

0:51:070:51:10

What you can't see is that's obviously not a normal room.

0:51:100:51:13

In fact, the room has this sort of shape.

0:51:130:51:17

It is just the way we have set the camera angle.

0:51:170:51:20

What week doing is fooling and tricking your brain into thinking that is, in fact, a square room.

0:51:200:51:27

I can illustrate this with the next example over here.

0:51:270:51:30

Do these lines look equally long to you?

0:51:330:51:36

AUDIENCE: Yes.

0:51:360:51:38

The green lines? Who says they look the same?

0:51:380:51:41

That is a very strange brain you have. The rest of you, I hope...

0:51:410:51:45

Who things they look longer?

0:51:450:51:47

That's great! Because, of course, it's an illusion.

0:51:480:51:53

This is the Ponzo Illusion.

0:51:530:51:55

In fact, the lines are exactly the same length.

0:51:550:51:58

I'm going to make that big again.

0:52:000:52:02

What is going on here is your brain has been fooled by what are called perspective cues.

0:52:020:52:08

It's almost like it's on a railway track

0:52:080:52:10

and because railway tracks recede off into the distance, they converge.

0:52:100:52:15

Because this seems to be further away

0:52:150:52:18

and it is stretching over the edge, we assume it must be much larger

0:52:180:52:22

than this block which is sitting inside the tracks.

0:52:220:52:25

Once again, even though your brain tells you that they look different

0:52:250:52:28

in fact they are exactly the same length.

0:52:280:52:32

So, at this is what is going on in the Ames Room.

0:52:340:52:37

It uses these perspective cues of slanted lines to fool your brain

0:52:370:52:41

into thinking that the room is actually the same distance.

0:52:410:52:45

In fact, it is actually longer.

0:52:450:52:47

I suppose the best way to show you how it will work is if I go out there

0:52:470:52:50

and you can see what I am like and what the room is really like. OK?

0:52:500:52:55

-Here we are at the Ames Room. How are you doing?

-Fine.

0:53:000:53:03

If you have a look a round,

0:53:030:53:04

you can see that the room the room isn't straight or normal.

0:53:040:53:07

It has slanting lines and the way the team have built it...

0:53:070:53:11

when you shoot it from one angle it looks as if the perspective is correct,

0:53:110:53:15

but in fact it is entirely wrong. Why don't you swap over again?

0:53:150:53:18

In fact, I think I'll join you.

0:53:180:53:21

So you can watch me going into the room

0:53:210:53:23

and look how I transform in size. Here I come!

0:53:230:53:25

So, I'm big.

0:53:250:53:27

And now, Iona, you're bigger than both of us.

0:53:300:53:34

So, that's part of the magic of the Royal Institution.

0:53:340:53:37

Why don't you come back in and give a big round of applause for everyone?

0:53:370:53:42

APPLAUSE

0:53:420:53:44

So, all these illusions demonstrate

0:53:530:53:55

our brains constantly try to make sense of the world

0:53:550:53:58

and understand based on these stored representations.

0:53:580:54:01

The remarkable thing about illusions is, even when you know how they work,

0:54:010:54:04

and I've just demonstrated with the models and shown

0:54:040:54:07

that these are illusions, you can't help but see them one way or the other.

0:54:070:54:11

It's because your brain is creating your mind's experience.

0:54:110:54:14

You can't avoid that.

0:54:140:54:15

So, you remember I promised you we were going to look at Thalia's brain

0:54:150:54:19

and read her mind? Let's go back to Cheltenham and see if we've made that link.

0:54:190:54:24

Hello, Cheltenham, can you hear me at all?

0:54:240:54:27

-It's Cheltenham here. Hi, London.

-Is that Iain, is it?

0:54:270:54:30

Yes, hi, Bruce, hi!

0:54:300:54:32

Hi, hi! How's it been going? Have you managed to scan Thalia's brain?

0:54:320:54:36

Yeah, we've got some great pictures. It looks good.

0:54:360:54:38

Good. Can you send through the first image so we can get an idea of what you've got.

0:54:380:54:42

-That's structural image, is that correct?

-Yeah.

0:54:420:54:45

So, I'm going to tell the audience, to give them an idea what they're looking at.

0:54:450:54:51

Imagine I'm Thalia and I'm lying inside the scanner. Here I am.

0:54:510:54:55

And so the scan is going from the bottom of my brain up to the top of my head.

0:54:550:55:00

So this side of the screen is the right side of my brain, OK?

0:55:000:55:05

This side of the image on this side of the screen is the left side of my brain.

0:55:050:55:10

So, Iain, am I correct? Did you try showing Thalia a visual image earlier, is that right?

0:55:100:55:16

Yes, we did. We showed her a visual object, yeah.

0:55:160:55:19

Can you show us what the brain activation was like

0:55:190:55:23

when she was looking at a visual object? OK.

0:55:230:55:26

So, tell us, what part of the brain is that that's being activated?

0:55:260:55:30

-The back.

-So, if it's the back part of the brain, what's going on?

0:55:300:55:35

-Which area's that?

-Vision.

-That's right. We showed Thalia a picture.

0:55:350:55:39

When she looked at the picture, the back of her brain was more active.

0:55:390:55:43

This was showing the functions of her brain working.

0:55:430:55:45

Now, Thalia, we asked her to...

0:55:450:55:49

we had a walnut and we asked her to put it in one of her hands.

0:55:490:55:52

Have you been processing that image, Iain?

0:55:520:55:54

Yes, we have. We've been processing the image.

0:55:540:55:57

You say she had a walnut in one hand. We took some pictures while she was squeezing the walnut with her hand.

0:55:570:56:02

Great. Have you got those images ready for us? OK.

0:56:020:56:05

So, if that's the image, which side of the brain is more active? Which side of the image is it?

0:56:050:56:10

-Right.

-So, it's on the right side.

0:56:100:56:13

This is the right side of my brain. What you've learned tonight

0:56:130:56:16

about how things cross over, which hand is Thalia holding the walnut in?

0:56:160:56:20

-Left!

-Thalia, could you confirm to me which hand you were squeezing the walnut with?

0:56:200:56:26

My left hand.

0:56:260:56:29

Thank you.

0:56:290:56:32

You have just mind read Thalia because you predicted which hand

0:56:330:56:36

she was holding it in. Do you realise that's over 100 miles away?

0:56:360:56:41

A big round of applause, everyone.

0:56:410:56:43

APPLAUSE

0:56:430:56:45

Before we go, can we say thank you and good night to Thalia and Iain? Good night, Cheltenham.

0:56:530:56:57

Good night.

0:56:570:56:59

So, that's what's inside your head.

0:56:590:57:01

Your brain is interpreting the world around you into meaningful patterns

0:57:010:57:06

and storing those patterns of representations. With these technologies

0:57:060:57:10

we can read the activity of the brain.

0:57:100:57:12

Does that mean, to know what's on someone's mind, we have to look at brain activity?

0:57:120:57:16

The technologies are useful if you know what you're looking for

0:57:160:57:19

and the tasks are very simple, like squeezing a walnut in one hand.

0:57:190:57:24

But, the thing about humans is, we're very complicated.

0:57:240:57:27

The tasks we can do are very difficult.

0:57:270:57:29

That's what makes us human in many ways.

0:57:290:57:31

So, that raises the question,

0:57:310:57:34

who was coordinating all these difficult tasks and activities?

0:57:340:57:38

Who is in charge anyway? We'll be addressing that in the next lecture.

0:57:380:57:43

Good night and look after your brains. Good night.

0:57:430:57:46

CHEERING AND APPLAUSE

0:57:460:57:50

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