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: 2014-03-14

Readability: 4.2

1,226,930 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.

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. 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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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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12:12

or holding information in memory

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12:14

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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12:56

and what's up with that?

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Well, I'm wondering about that too,

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12:59

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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13:04

possible specializations in the brain

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13:06

for other very specific mental functions.

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13:09

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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13:16

even mental functions that may be critical for survival.

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13:19

In fact, a few years ago,

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13:21

there was a scientist in my lab

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who became quite convinced

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13:24

that he'd found a brain region

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13:26

for detecting food,

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13:28

and it responded really strongly in the scanner

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13:30

when people looked at images like this.

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13:32

And further, he found a similar response

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13:35

in more or less the same location

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13:37

in 10 out of 12 subjects.

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13:39

So he was pretty stoked,

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13:41

and he was running around the lab

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13:43

telling everyone that he was going to go on "Oprah"

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13:45

with his big discovery.

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13:47

But then he devised the critical test:

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13:50

He showed subjects images of food like this

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and compared them to images with very similar

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13:56

color and shape, but that weren't food, like these.

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13:59

And his region responded the same

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14:02

to both sets of images.

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14:04

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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14:08

So much for "Oprah."

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14:12

But then the question, of course, is,

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14:14

how do we process all this other stuff

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14:16

that we don't have specialized brain regions for?

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14:19

Well, I think the answer is that in addition

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14:21

to these highly specialized components
that I've been describing,

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14:25

we also have a lot of very general-
purpose machinery in our heads

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14:28

that enables us to tackle

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14:30

whatever problem comes along.

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14:32

In fact, we've shown recently that

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14:34

these regions here in white

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14:36

respond whenever you do any difficult mental task

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14:39

at all —

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14:41

well, of the seven that we've tested.

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14:44

So each of the brain regions that I've described

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14:46

to you today

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is present in approximately the same location

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14:50

in every normal subject.

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14:52

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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14:57

and it would look a lot like my brain,

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14:59

although the regions would be slightly different

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15:01

in their exact location and in their size.

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15:05

What's important to me about this work

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15:07

is not the particular locations of these brain regions,

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15:10

but the simple fact that we have

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15:13

selective, specific components of mind and brain

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15:15

in the first place.

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15:17

I mean, it could have been otherwise.

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15:19

The brain could have been a single,

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15:21

general-purpose processor,

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15:23

more like a kitchen knife

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15:24

than a Swiss Army knife.

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15:26

Instead, what brain imaging has delivered

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15:29

is this rich and interesting picture of the human mind.

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15:33

So we have this picture of very general-purpose

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15:35

machinery in our heads

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15:37

in addition to this surprising array

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15:39

of very specialized components.

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15:43

It's early days in this enterprise.

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We've painted only the first brushstrokes

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15:48

in our neural portrait of the human mind.

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15:51

The most fundamental questions remain unanswered.

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15:54

So for example, what does each
of these regions do exactly?

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15:58

Why do we need three face areas

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16:00

and three place areas,

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16:02

and what's the division of labor between them?

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16:04

Second, how are all these things

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16:07

connected in the brain?

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16:09

With diffusion imaging,

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16:10

you can trace bundles of neurons

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16:13

that connect to different parts of the brain,

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16:15

and with this method shown here,

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16:17

you can trace the connections of
individual neurons in the brain,

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16:20

potentially someday giving us a wiring diagram

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16:23

of the entire human brain.

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16:25

Third, how does all of this

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16:27

very systematic structure get built,

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16:30

both over development in childhood

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16:33

and over the evolution of our species?

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16:36

To address questions like that,

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16:38

scientists are now scanning

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16:40

other species of animals,

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16:42

and they're also scanning human infants.

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16:48

Many people justify the high
cost of neuroscience research

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16:52

by pointing out that it may help us someday

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16:55

to treat brain disorders like Alzheimer's and autism.

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16:58

That's a hugely important goal,

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17:00

and I'd be thrilled if any of my work contributed to it,

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17:03

but fixing things that are broken in the world

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17:06

is not the only thing that's worth doing.

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17:09

The effort to understand the human mind and brain

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17:12

is worthwhile even if it never led to the treatment

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17:15

of a single disease.

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17:17

What could be more thrilling

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17:19

than to understand the fundamental mechanisms

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17:22

that underlie human experience,

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17:24

to understand, in essence, who we are?

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This is, I think, the greatest scientific quest

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17:31

of all time.

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(Applause)

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Translated by Joseph Geni
Reviewed by Mad Aronson

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

THE ORIGINAL VIDEO ON TED.COM

Nancy Kanwisher: A neural portrait of the human mind | TED Talk | TED.com