to paint a neural portrait of the human mind.

今日お話ししたい事は

And the central idea of this work

世界中の科学者が行っている

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

あるプロジェクト

but a collection of highly specialized components,

ヒトの脳の神経が描く像についてです

each solving a different specific problem,

この研究の中心となる考えは

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

ヒトの思考と脳は

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

汎用な単一目的の プロセッサ―なのではなく

You walk into your child's daycare center.

高度に特殊化された 各部の複合体であり

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

その１つ１つが各々 固有の問題を解決しながらも

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

総合的に

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

思考する我々を 作っているという事です

Do you need new glasses?

これを理解する為

Are you losing your mind?

次のシナリオを想像してみて下さい

You run through a quick mental checklist.

あなたは自分の子供がいる 保育所に入って行きます

No, you seem to be thinking clearly,

いつものように何十人もの子どもがいて

and your vision is perfectly sharp.

親の迎えを待っていますが

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

今日は

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

子ども達の顔が奇妙に同じに見えます

and none of them looks familiar,

どの子が自分の子なのか 見分けがつきません

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

新しい眼鏡がいるのでしょうか？

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

気がおかしくなったのでしょうか？

It's called prosopagnosia,

素早く色々な事が頭をよぎります

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

いいえ頭ははっきりしていて

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

目も問題なく良く見えています

everything else is just fine.

全てがまともなのに

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

子供達の顔だけがそうでないのです

These syndromes collectively have suggested for a long time

顔は見えるのですが

that the mind is divvied up into distinct components,

区別ができず

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

どの子も覚えのない顔なのです

with the invention of brain imaging technology,

オレンジ色のリボンを見つけて

especially MRI.

ようやくそれが自分の子供だと分かります

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

このように急に顔を 認識できなくなることが

So I'm going to show you in a second

実際起きるのです

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

それは相貌失認と呼ばれ

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

脳のある特定の場所に

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

障害が起きた結果起きます

Okay let's try another one,

これに驚かされる事は

starting from the bottom and going through the top.

顔認知だけに障害があり

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

その他は問題がない事です

Okay here's another one.

相貌失認は脳損傷後におきる

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

数々の 驚くほど特異な 脳機能障害の１つです

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

このような症状などを総合して

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

脳は明確に役割が分担された領域別に

So this picture is nice,

分かれている事が長い間 示唆されていたのですが

if I do say so myself.

それ等の領域を探求する研究に

But it shows only anatomy.

一気に進歩をもたらしたのは

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

脳画像技術に於ける発明—

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

特にMRIです

that is, where neurons are firing.

MRIを使い脳内部の組織構造を

So here's how this works.

高解度画像で見ることができます

Brains are like muscles. When they get active,

MRIの断面画像を

they need increased blood flow to supply that activity,

MRIの断面画像を

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

よくご存知のものを通して

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

お見せしましょう

then blood flow increases just right there.

その物とは何か分かるでしょうか

So functional MRI picks up on that blood flow increase,

これです

producing a higher MRI response where neural activity goes up.

分かり難いですが アーティチョークです

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

ではこれはどうでしょう

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

下から上まで行きますよ

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

ブロッコリーの頭です！

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

綺麗でしょう？私は好きです

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

もう１つ 勿論これはヒトの脳です

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

実はこれは私の脳です

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

私の脳をスライスして行きます

so we set out to look for it.

右の方に鼻があり

So I was the first subject.

今ここに来ました ちょうどここです

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

この画像はいいですね 自分でも本当にそう思いますが

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

組織を映し出してるだけに過ぎません

like these

機能画像という本当にすごい進歩は

and objects like these

科学者が組織だけでなく

and faces… and objects… for hours.

活動 すなわちニューロンの発火を 捉える技術を

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

編み出した時に起きました

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

それは このような働きをします

is bladder control.

脳は筋肉の様なもので

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

活発な時は

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,

その活動の為に 送り込む血量を増やします

and here's what I saw.

幸いに脳の血流制御は 局部的なので

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

例えばここで 多くのニューロンが

but at the time I thought it was beautiful.

活発に発火し始めたら

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

そこの血流は増します

it's about the size of an olive

fMRIはその血流の 増加をキャッチし

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

ニューロンが活性化した箇所で

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

高反応を示します

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

具体的に

than when I was looking at objects.

fMRIの実験が如何に行われるか

So that's pretty cool.

そこからどんな事が分かるか

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

又 分からないかを説明するため

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

最初の研究の１つを お話しします

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

我々が知りたかったのは 顔認知だけの領野があるかどうかです

and I got a similar blob.

既に その存在は

And then I did it again,

お話しした相貌失認に基づき

I did it again and again and again,

推察されてはいましたが

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

健常者の脳にそれを確認した者は

But still, maybe this is something weird about my brain

誰もいませんでした

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

それで我々はその探索に 乗り出しました

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

私が最初の実験台になり

pretty much everyone has that little face-processing region

MRI 内に入り横たわりました

in a similar neighbourhood of the brain.

頭を出来るだけ動かさず

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

このような顔や物を

Is it really specialized just for face recognition?

何時間も見つめました

Well, maybe not, right?

何時間も見つめました

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

私は fMRIスキャナーの中で

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

費やした時間の合計が 世界記録に

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

近いと思いますが

is to rule out all those hypotheses.

この研究で 本当に大切なスキルの一つは

So we spent much of the next couple of years

膀胱制御でした

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

（笑）

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

スキャナーから出た時

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

データをすぐに分析して

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

私の脳の中で

No, we haven't.

顔を見ている時に 物体を見たときよりも

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

強い反応を示す箇所を探しました

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

これが私が見たものです

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

この画像は今の基準からすると ひどいもののように見えますが

you need to mess with it and see what happens,

当時は美しいものだと思いました

and normally we don't get to do that.

小さな塊が見える

But an amazing opportunity came about

箇所がありますが

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

オリーブサイズ位で

and who is shown here in this hospital bed

私の脳表面の下部—

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

ここから約2.5cm真っすぐ中に 入った所です

to identify the source of his seizures.

脳のその箇所が示しているのは

So it turned out by total chance that

強い fMRI反応 つまり

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

非常に活発な脳の神経の活動です

So with the patient's consent,

私が 物体でなく

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

人の顔写真を見ている時のものです

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

かなり面白いのですが

and he's never heard of the face area.

何故これが偶然でないと 分かるのでしょう？

So let's watch what happens.

では最も簡単な方法は

It's going to start with a control condition that will say “Sham”

実験をもう一度やってみる事です

nearly invisibly in red in the lower left,

私はMRIスキャナーに戻り

when no current is delivered,

もっと顔や物の写真を見ました

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

そして同じ様な斑点が見られました

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

それからもう一度やり

One, two three.

又同じ結果がでました

Nothing. –Nothing?

もう一度 もう一度と

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

もうその頃には

Look at my face

これは本物だと 信じる事にしました

One, two, three.

しかし これは私の脳が 何かおかしいからであり

You just turned into somebody else.

他の誰にも こういう事は 起きないのかもしれないと

Your face metamorphosed.

他の多くの人達も スキャンして調べると

Your nose got saggy. It went to the left.

殆ど同じ結果で

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

小さな顔領域が 誰でも

That was a trip.

同じ様な部位にありました

So this experiment…

それで次にくる疑問は

This experiment finally nails the case

この箇所の機能です

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

顔認知だけでしょうか？ そうでないかもしれませんね

but causally involved in face perception.

顔認知だけでしょうか？ そうでないかもしれませんね

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

人の顔だけに反応するのでなく

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

他の身体部分にも 反応するかもしれません

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

人の様な物や他の生物や

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

丸っこい物にも

so I can show you these things in my brain.

反応するかもしれません

So let's get started.

その領域が顔の認知に 特化して機能する事を

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

はっきり確かめる唯一の方法は

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

仮説を全て除外していく事です

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

そこで我々はそれから数年

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

色々な写真を見る人々の脳を

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

スキャンして

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

何の顔であろうと

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

顔の写真を見ている時は

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

顔以外の写真の時と比べて

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

脳のその領野が

that responds when you process color information.

強く反応しているのが

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

観察されました

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

これで我々は

and these regions in green right there are really active.

ここは顔認知に必要な領域だと 決定づけたのでしょうか

There's another one out on the outside surface again

いいえ そうではありません

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

脳画像だけでは 特定の領野が

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

特定の機能に必要かどうかは 分からないのです

like these moving dots here,

脳画像で私たちが出来る事は

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

様々な思考で あらゆる領野のニューロンが

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

活性・不活性化されるのを 見るだけです

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

脳の一部がある心的機能に 必要かどうかを見るには

Now all these regions I've shown you so far

そこを刺激して 反応を見る必要がありますが

are involved in specific aspects of visual perception.

普段そういう事はできません

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

しかし最近驚くべき機会が巡ってきて

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

私の同僚数人が

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

癲癇持ちのある男性を テストしました

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

これが病院のベットに 横たわるその男性です

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.

脳の表面に

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

癲癇の源を特定するための

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

電極が 配置されたばかりです

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

全く偶然に

and most of the same regions are in here,

電極の二つが

albeit sometimes different in size.

顔認知領域の上部に 配置されていました

Now, everything I've shown you so far

それで患者の同意を得て

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

医師達は

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

脳のその部位を電気で刺激して どうなるか彼に尋ねました

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

患者はどこに電極が あるのか知りませんし

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

患者はどこに電極が あるのか知りませんし

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

顔認知領域の事など 聞いた事もありません

They respond when you understand the meaning of a sentence,

では どうなるか見てみましょう

but not when you do other complex mental things

比較用の条件から始めます

like mental arithmetic or holding information in memory

殆ど見えないくらい「Sham」と

or appreciating the complex structure in a piece of music.

左下に赤く

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

電気が流されてない時に 出てきます

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

神経学者が患者にまず 話しかけているが聞こえます

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

神経学者：「私の顔を見て下さい

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.

こうした時に 何が起きるか言って下さい

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

いいですか？」

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

患者：「OK」

Well, I'm wondering about that too,

神経学者：「１､２､３」

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

患者：「何も起きません」 神経学者：「何も？Ok」

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

神経学者：「もう一度します

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

私の顔を見て

even mental functions that may be critical for survival.

１､２､３」

In fact, a few years ago,

患者：「他の誰かになっただけです

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

顔が変形して

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

鼻が下がり左に行き

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

見た事がある様な 他の人みたいになりました

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

でも全く他の誰かです

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

ドラッグでもやったようでした」

But then he devised the critical test.

（笑）

He showed subjects images of food like this

この実験が・・・

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

（拍手）

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

この実験で ついに確定したことは

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

この脳の領域は

So much for Oprah.

顔だけに反応するのでなく

But then the question, of course, is,

顔を認識する為に無くてはならないものだという事です

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

こうして顔認知領域に関しての 詳細を見てきたのは

Well, I think the answer is that, in addition

脳には特定の思考過程に関与する

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

領域がある事を確定するには

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

どのようにする必要があるのかを お伝えする為です