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Transcriber: Joseph Geni
Reviewer: Madeleine Aronson
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Today I want to tell you
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about a project being carried out
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by scientists all over the world
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to paint a neural portrait of the human mind.
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And the central idea of this work
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is that the human mind and brain
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is not a single, general-purpose processor,
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but a collection of highly specialized components,
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each solving a different specific problem,
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and yet collectively making up
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who we are as human beings and thinkers.
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To give you a feel for this idea,
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imagine the following scenario:
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You walk into your child's day care center.
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As usual, there's a dozen kids there
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waiting to get picked up,
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but this time,
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the children's faces look weirdly similar,
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and you can't figure out which child is yours.
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Do you need new glasses?
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Are you losing your mind?
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You run through a quick mental checklist.
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No, you seem to be thinking clearly,
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and your vision is perfectly sharp.
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And everything looks normal
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except the children's faces.
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You can see the faces,
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but they don't look distinctive,
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and none of them looks familiar,
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and it's only by spotting an orange hair ribbon
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that you find your daughter.
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This sudden loss of the ability to recognize faces
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actually happens to people.
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It's called prosopagnosia,
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and it results from damage
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to a particular part of the brain.
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The striking thing about it
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is that only face recognition is impaired;
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everything else is just fine.
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Prosopagnosia is one of many surprisingly specific
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mental deficits that can happen after brain damage.
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These syndromes collectively
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have suggested for a long time
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that the mind is divvied up into distinct components,
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but the effort to discover those components
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has jumped to warp speed
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with the invention of brain imaging technology,
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especially MRI.
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So MRI enables you to see internal anatomy
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at high resolution,
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so I'm going to show you in a second
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a set of MRI cross-sectional images
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through a familiar object,
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and we're going to fly through them
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and you're going to try to figure out what the object is.
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Here we go.
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It's not that easy. It's an artichoke.
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Okay, let's try another one,
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starting from the bottom and going through the top.
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Broccoli! It's a head of broccoli.
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Isn't it beautiful? I love that.
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Okay, here's another one. It's a brain, of course.
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In fact, it's my brain.
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We're going through slices through my head like that.
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That's my nose over on the right, and now
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we're going over here, right there.
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So this picture's nice, if I do say so myself,
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but it shows only anatomy.
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The really cool advance with functional imaging
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happened when scientists figured out how to make
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pictures that show not just anatomy but activity,
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that is, where neurons are firing.
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So here's how this works.
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Brains are like muscles.
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When they get active,
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they need increased blood flow to supply that activity,
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and lucky for us, blood flow
control to the brain is local,
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so if a bunch of neurons, say, right there
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get active and start firing,
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then blood flow increases just right there.
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So functional MRI picks up
on that blood flow increase,
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producing a higher MRI response
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where neural activity goes up.
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So to give you a concrete feel
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for how a functional MRI experiment goes
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and what you can learn from it
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and what you can't,
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let me describe one of the first studies I ever did.
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We wanted to know if there was a special
part of the brain for recognizing faces,
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and there was already reason to
think there might be such a thing
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based on this phenomenon of prosopagnosia
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that I described a moment ago,
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but nobody had ever seen that part of the brain
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in a normal person,
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so we set out to look for it.
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So I was the first subject.
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I went into the scanner, I lay on my back,
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I held my head as still as I could
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while staring at pictures of faces like these
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and objects like these
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and faces and objects for hours.
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So as somebody who has
pretty close to the world record
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of total number of hours spent inside an MRI scanner,
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I can tell you that one of the skills
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that's really important for MRI research
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is bladder control.
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(Laughter)
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When I got out of the scanner,
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I did a quick analysis of the data,
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looking for any parts of my brain
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that produced a higher response
when I was looking at faces
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than when I was looking at objects,
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and here's what I saw.
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Now this image looks just awful by today's standards,
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but at the time I thought it was beautiful.
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What it shows is that region right there,
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that little blob,
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it's about the size of an olive
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and it's on the bottom surface of my brain
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about an inch straight in from right there.
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And what that part of my brain is doing
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is producing a higher MRI response,
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that is, higher neural activity,
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when I was looking at faces
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than when I was looking at objects.
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So that's pretty cool,
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but how do we know this isn't a fluke?
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Well, the easiest way
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is to just do the experiment again.
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So I got back in the scanner,
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I looked at more faces and I looked at more objects
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and I got a similar blob,
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and then I did it again
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and I did it again
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and again and again,
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and around about then
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I decided to believe it was for real.
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But still, maybe this is
something weird about my brain
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and no one else has one of these things in there,
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so to find out, we scanned a bunch of other people
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and found that pretty much everyone
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has that little face-processing region
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in a similar neighborhood of the brain.
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So the next question was,
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what does this thing really do?
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Is it really specialized just for face recognition?
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Well, maybe not, right?
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Maybe it responds not only to faces
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but to any body part.
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Maybe it responds to anything human
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or anything alive
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or anything round.
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The only way to be really sure that that region
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is specialized for face recognition
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is to rule out all of those hypotheses.
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So we spent much of the next couple of years
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scanning subjects while they looked at lots
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of different kinds of images,
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and we showed that that part of the brain
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responds strongly when you look at
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any images that are faces of any kind,
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and it responds much less strongly
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to any image you show that isn't a face,
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like some of these.
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So have we finally nailed the case
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that this region is necessary for face recognition?
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No, we haven't.
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Brain imaging can never tell you
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if a region is necessary for anything.
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All you can do with brain imaging
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is watch regions turn on and off
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as people think different thoughts.
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To tell if a part of the brain is
necessary for a mental function,
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you need to mess with it and see what happens,
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and normally we don't get to do that.
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But an amazing opportunity came about
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very recently when a couple of colleagues of mine
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tested this man who has epilepsy
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and who is shown here in his hospital bed
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where he's just had electrodes placed
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on the surface of his brain
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to identify the source of his seizures.
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So it turned out by total chance
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that two of the electrodes
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happened to be right on top of his face area.
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So with the patient's consent,
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the doctors asked him what happened
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when they electrically stimulated
that part of his brain.
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Now, the patient doesn't know
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where those electrodes are,
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and he's never heard of the face area.
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So let's watch what happens.
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It's going to start with a control condition
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that will say "Sham" nearly invisibly
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in red in the lower left,
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when no current is delivered,
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and you'll hear the neurologist speaking
to the patient first. So let's watch.
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(Video) Neurologist: Okay, just look at my face
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and tell me what happens when I do this.
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All right?
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Patient: Okay.
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Neurologist: One, two, three.
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Patient: Nothing.
Neurologist: Nothing? Okay.
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I'm going to do it one more time.
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Look at my face.
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One, two, three.
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Patient: You just turned into somebody else.
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Your face metamorphosed.
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Your nose got saggy, it went to the left.
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You almost looked like somebody I'd seen before,
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but somebody different.
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That was a trip.
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(Laughter)
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Nancy Kanwisher: So this experiment —
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(Applause) —
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this experiment finally nails the case
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that this region of the brain is not only
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selectively responsive to faces
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but causally involved in face perception.
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So I went through all of these details
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about the face region to show you what it takes
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to really establish that a part of the brain
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is selectively involved in a specific mental process.
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Next, I'll go through much more quickly
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some of the other specialized regions of the brain
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that we and others have found.
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So to do this, I've spent a lot of time
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in the scanner over the last month
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so I can show you these things in my brain.
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So let's get started. Here's my right hemisphere.
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So we're oriented like that.
You're looking at my head this way.
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Imagine taking the skull off
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and looking at the surface of the brain like that.
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Okay, now as you can see,
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the surface of the brain is all folded up.
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So that's not good. Stuff could be hidden in there.
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We want to see the whole thing,
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so let's inflate it so we can see the whole thing.
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Next, let's find that face area I've been talking about
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that responds to images like these.
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To see that, let's turn the brain around
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and look on the inside surface on the bottom,
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and there it is, that's my face area.
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Just to the right of that is another region
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that is shown in purple
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that responds when you process color information,
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and near those regions are other regions
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that are involved in perceiving places,
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like right now, I'm seeing
this layout of space around me
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and these regions in green right there
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are really active.
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There's another one out on the outside surface again
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where there's a couple more face regions as well.
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Also in this vicinity
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is a region that's selectively involved
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in processing visual motion,
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like these moving dots here,
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and that's in yellow at the bottom of the brain,
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and near that is a region that responds
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when you look at images of bodies and body parts
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like these, and that region is shown in lime green
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at the bottom of the brain.
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Now all these regions I've shown you so far
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are involved in specific aspects of visual perception.
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Do we also have specialized brain regions
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for other senses, like hearing?
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Yes, we do. So if we turn the brain around a little bit,
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here's a region in dark blue
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that we reported just a couple of months ago,
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and this region responds strongly
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when you hear sounds with pitch, like these.
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(Sirens)
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(Cello music)
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(Doorbell)
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In contrast, that same region
does not respond strongly
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when you hear perfectly familiar sounds
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that don't have a clear pitch, like these.
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(Chomping)
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(Drum roll)
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(Toilet flushing)
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Okay. Next to the pitch region
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is another set of regions that
are selectively responsive
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when you hear the sounds of speech.
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Okay, now let's look at these same regions.
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In my left hemisphere, there's a similar arrangement —
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not identical, but similar —
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and most of the same regions are in here,
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albeit sometimes different in size.
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Now, everything I've shown you so far
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are regions that are involved in
different aspects of perception,
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vision and hearing.
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Do we also have specialized brain regions
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for really fancy, complicated mental processes?
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Yes, we do.
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So here in pink are my language regions.
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So it's been known for a very long time
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that that general vicinity of the brain
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is involved in processing language,
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but we showed very recently
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that these pink regions
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respond extremely selectively.
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They respond when you understand
the meaning of a sentence,
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but not when you do other complex mental things,
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like mental arithmetic
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or holding information in memory
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or appreciating the complex structure
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in a piece of music.
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The most amazing region that's been found yet
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is this one right here in turquoise.
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This region responds
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when you think about what another person is thinking.
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So that may seem crazy,
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but actually, we humans do this all the time.
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You're doing this when you realize
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that your partner is going to be worried
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if you don't call home to say you're running late.
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I'm doing this with that region of my brain right now
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when I realize that you guys
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are probably now wondering about
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all that gray, uncharted territory in the brain,
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and what's up with that?
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Well, I'm wondering about that too,
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and we're running a bunch of
experiments in my lab right now
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to try to find a number of other
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possible specializations in the brain
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for other very specific mental functions.
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But importantly, I don't think we have
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specializations in the brain
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for every important mental function,
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even mental functions that may be critical for survival.
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In fact, a few years ago,
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there was a scientist in my lab
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who became quite convinced
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that he'd found a brain region
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for detecting food,
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and it responded really strongly in the scanner
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when people looked at images like this.
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And further, he found a similar response
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in more or less the same location
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in 10 out of 12 subjects.
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So he was pretty stoked,
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and he was running around the lab
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telling everyone that he was going to go on "Oprah"
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with his big discovery.
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But then he devised the critical test:
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He showed subjects images of food like this
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and compared them to images with very similar
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color and shape, but that weren't food, like these.
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And his region responded the same
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to both sets of images.
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So it wasn't a food area,
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it was just a region that liked colors and shapes.
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So much for "Oprah."
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But then the question, of course, is,
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how do we process all this other stuff
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that we don't have specialized brain regions for?
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Well, I think the answer is that in addition
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to these highly specialized components
that I've been describing,
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we also have a lot of very general-
purpose machinery in our heads
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that enables us to tackle
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whatever problem comes along.
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In fact, we've shown recently that
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these regions here in white
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respond whenever you do any difficult mental task
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at all —
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well, of the seven that we've tested.
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So each of the brain regions that I've described
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to you today
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is present in approximately the same location
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in every normal subject.
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I could take any of you,
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pop you in the scanner,
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and find each of those regions in your brain,
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and it would look a lot like my brain,
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although the regions would be slightly different
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in their exact location and in their size.
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What's important to me about this work
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is not the particular locations of these brain regions,
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but the simple fact that we have
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selective, specific components of mind and brain
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in the first place.
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I mean, it could have been otherwise.
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The brain could have been a single,
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general-purpose processor,
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more like a kitchen knife
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than a Swiss Army knife.
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Instead, what brain imaging has delivered
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is this rich and interesting picture of the human mind.
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So we have this picture of very general-purpose
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machinery in our heads
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in addition to this surprising array
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of very specialized components.
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It's early days in this enterprise.
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We've painted only the first brushstrokes
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in our neural portrait of the human mind.
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The most fundamental questions remain unanswered.
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So for example, what does each
of these regions do exactly?
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Why do we need three face areas
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and three place areas,
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and what's the division of labor between them?
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Second, how are all these things
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connected in the brain?
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With diffusion imaging,
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you can trace bundles of neurons
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that connect to different parts of the brain,
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and with this method shown here,
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you can trace the connections of
individual neurons in the brain,
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potentially someday giving us a wiring diagram
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of the entire human brain.
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Third, how does all of this
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very systematic structure get built,
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both over development in childhood
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and over the evolution of our species?
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To address questions like that,
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scientists are now scanning
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other species of animals,
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and they're also scanning human infants.
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Many people justify the high
cost of neuroscience research
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by pointing out that it may help us someday
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to treat brain disorders like Alzheimer's and autism.
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That's a hugely important goal,
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and I'd be thrilled if any of my work contributed to it,
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but fixing things that are broken in the world
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is not the only thing that's worth doing.
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The effort to understand the human mind and brain
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is worthwhile even if it never led to the treatment
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of a single disease.
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What could be more thrilling
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than to understand the fundamental mechanisms
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that underlie human experience,
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to understand, in essence, who we are?
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This is, I think, the greatest scientific quest
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of all time.
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(Applause)
