Name: 【TED】Nancy Kanwisher: A neural portrait of the human mind (Nancy Kanwisher: A neural portrait of the human mind)
Uploaded: 2014-10-24T16:54:00.000Z
Duration: 17 min 45 s
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Today I want to tell you about a project being carried out by scientists all over the world

to paint a neural portrait of the human mind.

is that the human mind and brain is not a single, general-purpose processor,

but a collection of highly specialized components,

each solving a different specific problem,

and yet collectively making up who we are as human beings and thinkers.

To give you a feel for this idea, imagined the following scenario:

You walk into your child's daycare center.

As usual, there's a dozen kids there, waiting to get picked up.

But this time, the children's faces look weirdly similar,

and you can't figure out which child is yours.

You run through a quick mental checklist.

And everything looks normal, except the children's faces.

You can see the faces, but they don't look distinctive,

and it's only by spotting an orange hair ribbon that you find your daughter.

This sudden lost of the ability to recognize faces actually happens to people.

and it results from damage to a particular part of the brain.

The striking thing about it is that only face recognition is impaired,

So prosopagnosia is one of many surprisingly specific mental deficits that can happen after brain damage.

These syndromes collectively have suggested for a long time

that the mind is divvied up into distinct components,

but the effort to discover those components has jumped to warp speed

with the invention of brain imaging technology,

So MRI enables you to see internal anatomy at high resolution.

a set of MRI cross-sectional images through a familiar object,

and we're going to fly through them and you're going to try to figure out what the object is. Here we go.

starting from the bottom and going through the top.

Broccoli! It's a head of broccoli. It's it beautiful? I love that.

It's a brain, of course. In fact, it's my brain.

We're going through slices through my head like that.

That's my nose over on the right, and now we're going over here. Right there.

The really cool advance with functional imaging happened when scientists figured out

how to make pictures that show not just anatomy but activity,

Brains are like muscles. When they get active,

they need increased blood flow to supply that activity,

and lucky for us, blood flow control to the brain is local.

So if a bunch of neurons, say, right there get active and start firing,

then blood flow increases just right there.

So functional MRI picks up on that blood flow increase,

producing a higher MRI response where neural activity goes up.

So to give you a concrete feel for how a functional MRI experiment goes

and what you can learn from it and what you can't,

let me describe one of the first studies I ever did.

We wanted to know if there was a special part of the brain for recognizing faces,

and there was already reason to think there might be such a thing

based on this phenomenon of prosopagnosia that I described a moment ago.

But nobody had ever seen that part of the brain in a normal person,

I went into the scanner, I lay on my back,

I held my head as still as I could while staring at pictures of faces

So as somebody who has pretty close to the world record of total number of hours spent inside a MRI scanner,

I can tell you that one of the skills that's really important for MRI research

When I got out of the scanner, I did a quick analysis of the data,

looking for any parts of my brain that produced a higher response when I was looking at faces than when I was looking at objects,

Now, this image looks just awful by today's standards,

but at the time I thought it was beautiful.

What it shows is that region right there, that little blob,

and it's on the bottom surface of my brain about an inch straight in from right there.

And what that part of my brain is doing is producing a higher MRI response,

that is, higher neural activity, when I was looking at faces

Well, the easiest way is to just do the experiment again.

So I got back in the scanner, I looked at more faces and I looked at more objects

and around about then I decided to believe it was for real.

But still, maybe this is something weird about my brain

and no one else has one of these things in there.

So to find out, we scanned a bunch of other people and found that

pretty much everyone has that little face-processing region

So the next question was, what does this thing really do?