ABOUT THE SPEAKER
Nancy Kanwisher - Brain researcher
Using fMRI imaging to watch the human brain at work, Nancy Kanwisher’s team has discovered cortical regions responsible for some surprisingly specific elements of cognition.

Why you should listen

Does the brain use specialized processors to solve complex problems, or does it rely instead on more general-purpose systems?

This question has been at the crux of brain research for centuries. MIT researcher Nancy Kanwisher seeks to answer this question by discovering a “parts list” for the human mind and brain. "Understanding the nature of the human mind," she says, "is arguably the greatest intellectual quest of all time."

Kanwisher and her colleagues have used fMRI to identify distinct sites in the brain for face recognition, knowing where you are, and thinking about other people’s thoughts. Yet these discoveries are a prelude to bigger questions: How do these brain regions develop and function? What are the actual computations that go on in each region, and how are these computations implemented in circuits of neurons? And how do these work together to produce human intelligence?

To learn more, see Kanwisher's collection of short talks on how scientists actually study the human mind and brain and what they have learned so far.

More profile about the speaker
Nancy Kanwisher | Speaker | TED.com
TED2014

Nancy Kanwisher: A neural portrait of the human mind

Filmed:
1,164,184 views

Brain imaging pioneer Nancy Kanwisher, who uses fMRI scans to see activity in brain regions (often her own), shares what she and her colleagues have learned: The brain is made up of both highly specialized components and general-purpose "machinery." Another surprise: There's so much left to learn.
- Brain researcher
Using fMRI imaging to watch the human brain at work, Nancy Kanwisher’s team has discovered cortical regions responsible for some surprisingly specific elements of cognition. Full bio

Double-click the English transcript below to play the video.

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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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11:41
vision and hearing.
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11:43
Do we also have specialized brain regions
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11:44
for really fancy, complicated mental processes?
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3435
11:48
Yes, we do.
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11:49
So here in pink are my language regions.
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3389
11:53
So it's been known for a very long time
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11:54
that that general vicinity of the brain
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2035
11:56
is involved in processing language,
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11:58
but we showed very recently
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12:00
that these pink regions
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1710
12:02
respond extremely selectively.
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12:04
They respond when you understand
the meaning of a sentence,
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2812
12:07
but not when you do other complex mental things,
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12:10
like mental arithmetic
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2179
12:12
or holding information in memory
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2396
12:14
or appreciating the complex structure
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12:17
in a piece of music.
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2284
12:21
The most amazing region that's been found yet
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2889
12:24
is this one right here in turquoise.
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3307
12:27
This region responds
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2190
12:30
when you think about what another person is thinking.
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4268
12:34
So that may seem crazy,
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1644
12:35
but actually, we humans do this all the time.
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12:39
You're doing this when you realize
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2193
12:42
that your partner is going to be worried
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12:43
if you don't call home to say you're running late.
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2507
12:46
I'm doing this with that region of my brain right now
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3469
12:49
when I realize that you guys
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2281
12:51
are probably now wondering about
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1598
12:53
all that gray, uncharted territory in the brain,
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2547
12:56
and what's up with that?
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1964
12:58
Well, I'm wondering about that too,
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1685
12:59
and we're running a bunch of
experiments in my lab right now
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2395
13:02
to try to find a number of other
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2013
13:04
possible specializations in the brain
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772113
2032
13:06
for other very specific mental functions.
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3368
13:09
But importantly, I don't think we have
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2621
13:12
specializations in the brain
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1564
13:13
for every important mental function,
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2746
13:16
even mental functions that may be critical for survival.
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3409
13:19
In fact, a few years ago,
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2102
13:21
there was a scientist in my lab
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1117
13:23
who became quite convinced
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791072
1409
13:24
that he'd found a brain region
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792481
1749
13:26
for detecting food,
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794230
1912
13:28
and it responded really strongly in the scanner
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796142
1918
13:30
when people looked at images like this.
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798060
2728
13:32
And further, he found a similar response
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800788
2912
13:35
in more or less the same location
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803700
1939
13:37
in 10 out of 12 subjects.
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805639
2001
13:39
So he was pretty stoked,
340
807640
2294
13:41
and he was running around the lab
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1260
13:43
telling everyone that he was going to go on "Oprah"
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811194
2002
13:45
with his big discovery.
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813196
2018
13:47
But then he devised the critical test:
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3022
13:50
He showed subjects images of food like this
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3183
13:53
and compared them to images with very similar
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821419
2741
13:56
color and shape, but that weren't food, like these.
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824160
3810
13:59
And his region responded the same
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827970
2131
14:02
to both sets of images.
349
830101
1949
14:04
So it wasn't a food area,
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1327
14:05
it was just a region that liked colors and shapes.
351
833377
2771
14:08
So much for "Oprah."
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836148
2561
14:12
But then the question, of course, is,
353
840483
2225
14:14
how do we process all this other stuff
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2126
14:16
that we don't have specialized brain regions for?
355
844834
2970
14:19
Well, I think the answer is that in addition
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847804
1811
14:21
to these highly specialized components
that I've been describing,
357
849615
3554
14:25
we also have a lot of very general-
purpose machinery in our heads
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853169
3679
14:28
that enables us to tackle
359
856848
1494
14:30
whatever problem comes along.
360
858342
2106
14:32
In fact, we've shown recently that
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860448
2055
14:34
these regions here in white
362
862503
2068
14:36
respond whenever you do any difficult mental task
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864571
3411
14:39
at all —
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867982
1101
14:41
well, of the seven that we've tested.
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869083
3571
14:44
So each of the brain regions that I've described
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872654
2169
14:46
to you today
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874823
1306
14:48
is present in approximately the same location
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876129
2767
14:50
in every normal subject.
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878896
1742
14:52
I could take any of you,
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1623
14:54
pop you in the scanner,
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882261
1226
14:55
and find each of those regions in your brain,
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883487
2285
14:57
and it would look a lot like my brain,
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885772
1905
14:59
although the regions would be slightly different
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887677
2070
15:01
in their exact location and in their size.
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889747
3564
15:05
What's important to me about this work
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2365
15:07
is not the particular locations of these brain regions,
377
895676
2969
15:10
but the simple fact that we have
378
898645
2587
15:13
selective, specific components of mind and brain
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2568
15:15
in the first place.
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903800
1648
15:17
I mean, it could have been otherwise.
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2011
15:19
The brain could have been a single,
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907459
2441
15:21
general-purpose processor,
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1495
15:23
more like a kitchen knife
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911395
1472
15:24
than a Swiss Army knife.
385
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1683
15:26
Instead, what brain imaging has delivered
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3111
15:29
is this rich and interesting picture of the human mind.
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917661
3846
15:33
So we have this picture of very general-purpose
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2463
15:35
machinery in our heads
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1070
15:37
in addition to this surprising array
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2357
15:39
of very specialized components.
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927397
3435
15:43
It's early days in this enterprise.
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2153
15:45
We've painted only the first brushstrokes
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2776
15:48
in our neural portrait of the human mind.
394
936641
2927
15:51
The most fundamental questions remain unanswered.
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3082
15:54
So for example, what does each
of these regions do exactly?
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942650
3800
15:58
Why do we need three face areas
397
946450
2142
16:00
and three place areas,
398
948592
1465
16:02
and what's the division of labor between them?
399
950057
2868
16:04
Second, how are all these things
400
952925
2693
16:07
connected in the brain?
401
955618
1712
16:09
With diffusion imaging,
402
957330
1587
16:10
you can trace bundles of neurons
403
958917
2179
16:13
that connect to different parts of the brain,
404
961096
2575
16:15
and with this method shown here,
405
963671
1631
16:17
you can trace the connections of
individual neurons in the brain,
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965302
3697
16:20
potentially someday giving us a wiring diagram
407
968999
2718
16:23
of the entire human brain.
408
971717
2066
16:25
Third, how does all of this
409
973783
2047
16:27
very systematic structure get built,
410
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3149
16:30
both over development in childhood
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978979
2956
16:33
and over the evolution of our species?
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981935
2812
16:36
To address questions like that,
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1900
16:38
scientists are now scanning
414
986647
1783
16:40
other species of animals,
415
988430
2157
16:42
and they're also scanning human infants.
416
990587
5386
16:48
Many people justify the high
cost of neuroscience research
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996931
3651
16:52
by pointing out that it may help us someday
418
1000582
2754
16:55
to treat brain disorders like Alzheimer's and autism.
419
1003336
3457
16:58
That's a hugely important goal,
420
1006793
1947
17:00
and I'd be thrilled if any of my work contributed to it,
421
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3221
17:03
but fixing things that are broken in the world
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2998
17:06
is not the only thing that's worth doing.
423
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2801
17:09
The effort to understand the human mind and brain
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3228
17:12
is worthwhile even if it never led to the treatment
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2818
17:15
of a single disease.
426
1023806
1677
17:17
What could be more thrilling
427
1025483
2037
17:19
than to understand the fundamental mechanisms
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3141
17:22
that underlie human experience,
429
1030661
2296
17:24
to understand, in essence, who we are?
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2926
17:27
This is, I think, the greatest scientific quest
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1035883
3449
17:31
of all time.
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2713
17:34
(Applause)
433
1042045
5470
Translated by Joseph Geni
Reviewed by Mad Aronson

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ABOUT THE SPEAKER
Nancy Kanwisher - Brain researcher
Using fMRI imaging to watch the human brain at work, Nancy Kanwisher’s team has discovered cortical regions responsible for some surprisingly specific elements of cognition.

Why you should listen

Does the brain use specialized processors to solve complex problems, or does it rely instead on more general-purpose systems?

This question has been at the crux of brain research for centuries. MIT researcher Nancy Kanwisher seeks to answer this question by discovering a “parts list” for the human mind and brain. "Understanding the nature of the human mind," she says, "is arguably the greatest intellectual quest of all time."

Kanwisher and her colleagues have used fMRI to identify distinct sites in the brain for face recognition, knowing where you are, and thinking about other people’s thoughts. Yet these discoveries are a prelude to bigger questions: How do these brain regions develop and function? What are the actual computations that go on in each region, and how are these computations implemented in circuits of neurons? And how do these work together to produce human intelligence?

To learn more, see Kanwisher's collection of short talks on how scientists actually study the human mind and brain and what they have learned so far.

More profile about the speaker
Nancy Kanwisher | Speaker | TED.com