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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.

  • And the central idea of this work

  • 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.

  • Do you need new glasses?

  • Are you losing your mind?

  • You run through a quick mental checklist.

  • No, you seem to be thinking clearly,

  • and your vision is perfectly sharp.

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

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

  • and none of them looks familiar,

  • 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.

  • It's called prosopagnosia,

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

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

  • everything else is just fine.

  • 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,

  • especially MRI.

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

  • So I'm going to show you in a second

  • 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.

  • It's not that easy. It's an artichoke.

  • Okay let's try another one,

  • starting from the bottom and going through the top.

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

  • Okay here's another one.

  • 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.

  • So this picture is nice,

  • if I do say so myself.

  • But it shows only anatomy.

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

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

  • that is, where neurons are firing.

  • So here's how this works.

  • 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,

  • so we set out to look for it.

  • So I was the first subject.

  • 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

  • like these

  • and objects like these

  • and facesand objectsfor hours.

  • 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

  • is bladder control.

  • 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,

  • and here's what I saw.

  • 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,

  • it's about the size of an olive

  • 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

  • than when I was looking at objects.

  • So that's pretty cool.

  • But how do we know this isn't a fluke?

  • 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 I got a similar blob.

  • And then I did it again,

  • I did it again and again and again,

  • 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

  • in a similar neighbourhood of the brain.

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

  • Is it really specialized just for face recognition?

  • Well, maybe not, right?

  • Maybe it responds not only to faces but to any body part.

  • Maybe it responds to anything human or anything alive or anything round.

  • The only way to be really sure that that region is specialized for face recognition

  • is to rule out all those hypotheses.

  • So we spent much of the next couple of years

  • scanning subjects while they looked at lots of different kinds of images,

  • and we showed that that part of the brain responds strongly when you look at any images that are faces of any kind,

  • and it responds much less strongly to any image you show that isn't a face, like some of these.

  • So have we finally nailed the case that this region is necessary for face recognition?

  • No, we haven't.

  • Brain imaging can never tell you if a region is necessary for anything.

  • All you can do with brain imaging is watch regions turn on and off as people think different thoughts.

  • To tell if a part of the brain is necessary for a mental function,

  • you need to mess with it and see what happens,

  • and normally we don't get to do that.

  • But an amazing opportunity came about

  • very recently when a couple of colleagues of mine tested this man who has epilepsy

  • and who is shown here in this hospital bed

  • where he's just had electrodes placed on the surface of his brain

  • to identify the source of his seizures.

  • So it turned out by total chance that

  • two of the electrodes happen to be right on top of this face area.

  • So with the patient's consent,

  • the doctors asked him what happened when they electrically stimulated that part of his brain.

  • Now, the patient doesn't know where those electrodes are,

  • and he's never heard of the face area.

  • So let's watch what happens.

  • It's going to start with a control condition that will saySham

  • nearly invisibly in red in the lower left,

  • when no current is delivered,

  • and you'll hear the neurologist speaking to the patient first. So let's watch.

  • Okay, just look at my face and tell me what happens when I do this. Alright?

  • One, two three.

  • Nothing. –Nothing?

  • Okay, I'm going to do it one more time.

  • Look at my face

  • One, two, three.

  • You just turned into somebody else.

  • Your face metamorphosed.

  • Your nose got saggy. It went to the left.

  • You almost looked like somebody I'd seen before, but somebody different.

  • That was a trip.

  • So this experiment

  • This experiment finally nails the case

  • that this region of the brain is not only selectively responsive to faces,

  • but causally involved in face perception.

  • that this region of the brain is not only selectively responsive to faces,

  • to really establish that a part of the brain is selectively involved in a specific mental process.

  • Next, I'll go through much more quickly some of the other specialized regions of the brain that we and others have found.

  • So to do this, I've spent a lot of time in the scanner over the last month

  • so I can show you these things in my brain.

  • So let's get started.

  • Here's my right hemisphere. So we're oriented like that.

  • You're looking at my head this way. Imagine taking the skull off and looking at the surface of the brain like that.

  • Okay, now as you can see, the surface of the brain is all folded up.

  • So that's not good. Stuff could be hidden in there. We want to see the whole thing.

  • So let's inflate it so we can see the whole thing.

  • Next, let's find that face area I've been talking about that responds to images like these.

  • To see that, let's turn the brain around and look on the inside surface on the bottom,

  • and there it is, that's my face area.

  • Just to the right of that is another region that is shown in purple

  • that responds when you process color information.

  • And near those regions are other regions that are involved in perceiving places,

  • like right now I'm seeing this layout of space around me,

  • and these regions in green right there are really active.

  • There's another one out on the outside surface again

  • where there's a couple more face regions as well.

  • Also in this vicinity is a region that's selectively involved in processing visual motion,

  • like these moving dots here,

  • and that's in yellow at the bottom of the brain.

  • And near that is a region that responds when you look at images of bodies and body parts like these,

  • and that region is shown in lime green at the bottom of the brain.

  • Now all these regions I've shown you so far

  • are involved in specific aspects of visual perception.

  • Do we also have specialized brain regions for other senses, like hearing?

  • Yes, we do. So if we turn the brain around a little bit,

  • here's a region in dark blue that we recorded just a couple of months ago,

  • and this region responds strongly when you hear sounds with pitch, like these.

  • Okay? In contrast, that same region does not respond strongly when you hear perfectly familiar sounds that don't have a clear pitch, like these.

  • Next to the pitch region is another set of regions that are selectively responsive when you hear the sounds of speech.

  • Okay, now let's look at these same regions.

  • In my left hemisphere, there's a similar arrangement, not identical, but similar,

  • and most of the same regions are in here,

  • albeit sometimes different in size.

  • Now, everything I've shown you so far

  • are regions that are involved in different aspects of perception, vision and hearing.

  • Do we also have specialized brain regions for really fancy, complicated mental processes?

  • Yes, we do. So here in pink are my language regions.

  • So it's been known for a very long time that that general vicinity of the brain is involved in processing language.

  • But we showed very recently that these pink regions respond extremely selectively.

  • They respond when you understand the meaning of a sentence,

  • but not when you do other complex mental things

  • like mental arithmetic or holding information in memory

  • or appreciating the complex structure in a piece of music.

  • The most amazing region that's been found yet is this one right here in turquoise.

  • This region responds when you think about what another person is thinking.

  • So that may seem crazy, but actually we humans do this all the time.

  • You're doing this when you realize that your partner is going to be worried if you don't call home to say you're running late.

  • I'm doing this with that region of my brain right now

  • when I realize that you guys are probably now wondering about all that gray, uncharted territory in the brain, what's up with that?

  • Well, I'm wondering about that too,

  • and we're running a bunch of experiments in my lab right now

  • to try to find a number of other possible specializations in the brain for other very specific mental functions.

  • But importantly, I don't think we have specializations in the brain for every important mental function,

  • even mental functions that may be critical for survival.

  • In fact, a few years ago,

  • there was a scientist in my lab who became quite convinced that he'd found a brain region for detecting food,

  • and it responded really strongly in the scanner when people look at images like this.

  • And further, he found a similar response in more or less the same location in 10 out of 12 subjects.

  • So he was pretty stoked and he was running around the lab

  • telling everyone that he was going to go on Oprah with his big discovery.

  • But then he devised the critical test.

  • He showed subjects images of food like this

  • and compared them to images with very similar color and shape, but that weren't food, like these,

  • and his region responded the same to both sets of images.

  • So it wasn't a food area. It was just a region that liked colors and shapes.

  • So much for Oprah.

  • But then the question, of course, is,

  • how do we process all this other stuff that we don't have specialized brain regions for?

  • Well, I think the answer is that, in addition

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

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

  • that enables us to tackle whatever problem comes along.

  • In fact, we've shown recently that these regions here in white

  • respond whenever you do any difficult mental task at all,

  • well, of the seven that we've tested.

  • So each of the brain regions that I've described to you today

  • is present in approximately the same location in every normal subject.

  • I could take any of you, pop you in a scanner,

  • and find each of those regions in your brain,