Placeholder Image

字幕表 動画を再生する

  • Today I want to tell you about a project being carried out by scientists all over the world

    翻訳: Reiko Bovee 校正: Eriko T

  • 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 facesand objectsfor 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 saySham

    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

  • that enables us to tackle whatever problem comes along.

    次にもっと端的に

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

    今までに発見された 機能が分化した脳領域

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

    に関してお話しします