I grew up watching Star Trek. I love Star Trek.

《星際爭霸戰》讓我想要看外星生物，

Star Trek made me want to see alien creatures,

從遙遠星球來的生物。

creatures from a far-distant world.

但事實上，我發現我可以在地球上

But basically, I figured out that I could find

找到這些外星生物。

those alien creatures right on Earth.

我所作的就是研究昆蟲。

And what I do is I study insects.

我迷上了昆蟲， 尤其是昆蟲飛行。

I'm obsessed with insects, particularly insect flight.

我認為昆蟲飛行的演化

I think the evolution of insect flight is perhaps

大概是生命史上最重要的事。

one of the most important events in the history of life.

如果沒有昆蟲， 就不會有開花植物。

Without insects, there'd be no flowering plants.

沒有開花植物， 就不會有聰明、

Without flowering plants, there would be no

吃水果的靈長類在TED演講。

clever, fruit-eating primates giving TED Talks.

（笑聲）

(Laughter)

現在，

Now,

大衛、希地可和科踏希

David and Hidehiko and Ketaki

說了一個很令人信服的故事，

gave a very compelling story about

故事關於果蠅與人的相似處。

the similarities between fruit flies and humans,

我們真的有許多相似之處，

and there are many similarities,

所以你也許會認為 如果人跟果蠅是相似的，

and so you might think that if humans are similar to fruit flies,

那麼果蠅最喜歡的行為可能是這個

the favorite behavior of a fruit fly might be this, for example --

（笑聲）

(Laughter)

但在我的演講中， 我不想強調果蠅與人的相似之處，

but in my talk, I don't want to emphasize on the similarities

我反而要談兩者間不同的部份，

between humans and fruit flies, but rather the differences,

而且我要強調果蠅擅長的行為。

and focus on the behaviors that I think fruit flies excel at doing.

所以我想要給你們看一段高速影片，

And so I want to show you a high-speed video sequence

是在紅外光照明下 以每秒 7 千幅拍攝果蠅飛行的影片，

of a fly shot at 7,000 frames per second in infrared lighting,

在右邊螢幕外， 有個電子虛擬獵食者

and to the right, off-screen, is an electronic looming predator

會飛去捕食果蠅。

that is going to go at the fly.

果蠅會感受到這個獵食者。

The fly is going to sense this predator.

牠會伸長它的腿。

It is going to extend its legs out.

牠會以搖曳生姿飛走

It's going to sashay away

然後多活一天。

to live to fly another day.

我仔細裁剪了這個影片

Now I have carefully cropped this sequence

讓他的速度跟 人類眨眼速度一樣，

to be exactly the duration of a human eye blink,

所以在你眨眼所需要的時間中，

so in the time that it would take you to blink your eye,

果蠅會看到這個獵食者、

the fly has seen this looming predator,

估計位置、開始運動並飛走，

estimated its position, initiated a motor pattern to fly it away,

以每秒拍動翅膀 220 次的速度飛走。

beating its wings at 220 times a second as it does so.

我認為這是一個令人著迷的行為，

I think this is a fascinating behavior

這表示果蠅的大腦 可以如此快速地處理資訊。

that shows how fast the fly's brain can process information.

飛行需要什麼？

Now, flight -- what does it take to fly?

嗯，要能夠飛翔， 就得像人類的飛機一樣，

Well, in order to fly, just as in a human aircraft,

你需要可以產生 足夠空氣動力的翅膀，

you need wings that can generate sufficient aerodynamic forces,

你需要能夠產生 足夠飛行所需能量的發動機，

you need an engine sufficient to generate the power required for flight,

且你需要一個控制器。

and you need a controller,

在人類第一架飛機上，控制器基本上是

and in the first human aircraft, the controller was basically

坐在駕駛艙的奧維爾和威爾伯的大腦。

the brain of Orville and Wilbur sitting in the cockpit.

這跟果蠅比較起來是如何呢？

Now, how does this compare to a fly?

嗯，我早期的研究 花了很多時間試圖找出

Well, I spent a lot of my early career trying to figure out

昆蟲翅膀如何生成 足夠的能量使果蠅得以維持在空中。

how insect wings generate enough force to keep the flies in the air.

你也許聽說過工程師如何證明

And you might have heard how engineers proved

熊蜂飛不起來。

that bumblebees couldn't fly.

嗯，這個思考邏輯的問題是

Well, the problem was in thinking that the insect wings

認為兩者翅膀的運作方式一樣。 但事實上不然。

function in the way that aircraft wings work. But they don't.

我們研究的方法是建造巨大模型，

And we tackle this problem by building giant,

按動態比例建造巨大機器昆蟲

dynamically scaled model robot insects

並在礦物油巨型池當中拍打翅膀，

that would flap in giant pools of mineral oil

這樣我們可以研究空氣動力。

where we could study the aerodynamic forces.

我們發現昆蟲以 一種非常聰明的方法拍動翅膀，

And it turns out that the insects flap their wings

有非常大的攻角，

in a very clever way, at a very high angle of attack

使翅膀前沿產生一個像龍捲風的結構

that creates a structure at the leading edge of the wing,

叫作前緣渦，

a little tornado-like structure called a leading edge vortex,

而且正是這個翅膀上的前緣渦

and it's that vortex that actually enables the wings

讓動物能夠產生足以停留在空中的動力。

to make enough force for the animal to stay in the air.

但是實際上迷人的

But the thing that's actually most -- so, what's fascinating

並不是這個構造有多稀奇。

is not so much that the wing has some interesting morphology.

而是聰明的果蠅如何拍打它，

What's clever is the way the fly flaps it,

這當然最終是 受中樞神經系統控制，

which of course ultimately is controlled by the nervous system,

而這也是果蠅可以執行

and this is what enables flies to perform

這些高超飛行技巧的原因。

these remarkable aerial maneuvers.

那麼引擎呢？

Now, what about the engine?

果蠅的引擎絕對令人著迷。

The engine of the fly is absolutely fascinating.

牠們有兩種類型的飛行肌：

They have two types of flight muscle:

所謂的能量肌肉，這是牽張啟動，

so-called power muscle, which is stretch-activated,

也就是說它可以自我啟動

which means that it activates itself and does not need to be controlled

不需要中樞神經 不斷收縮來控制。

on a contraction-by-contraction basis by the nervous system.

這是由飛行所需 巨大的力量所專一化出來的，

It's specialized to generate the enormous power required for flight,

這肌肉充滿了果蠅中間的部分，

and it fills the middle portion of the fly,

所以當一隻果蠅撞到你的擋風玻璃時，

so when a fly hits your windshield,

基本上你看到的 就是這些能量肌肉的動作。

it's basically the power muscle that you're looking at.

但在機翼的基部

But attached to the base of the wing

有一套小小的微型控制肌肉，

is a set of little, tiny control muscles

它們不大有力但速度非常快，

that are not very powerful at all, but they're very fast,

它們能夠以每一拍擊為基礎

and they're able to reconfigure the hinge of the wing

重新配置機翼轉軸，

on a stroke-by-stroke basis,

這使果蠅得以調整翅膀

and this is what enables the fly to change its wing

來產生及更改空氣動力，

and generate the changes in aerodynamic forces

並連帶改變其飛行軌跡。

which change its flight trajectory.

當然，中樞神經系統控制這一切。

And of course, the role of the nervous system is to control all this.

所以讓我們來看看控制器。

So let's look at the controller.

果蠅在這方面

Now flies excel in the sorts of sensors

有各種非常精巧的感應器。

that they carry to this problem.

牠們有天線可以感受氣味和風向。

They have antennae that sense odors and detect wind detection.

牠們有複雜的眼睛，

They have a sophisticated eye which is

是這個星球上最快的視覺系統。

the fastest visual system on the planet.

牠們在頭頂上有另一對眼睛，

They have another set of eyes on the top of their head.

但目前我們還不清楚它們的用處。

We have no idea what they do.

牠們的翅膀上有感應器。

They have sensors on their wing.

牠們的翅耪上充滿了感應器，

Their wing is covered with sensors, including sensors

包括感應機翼變形的感應器。

that sense deformation of the wing.

牠們甚至可以 用翅膀偵測味道。

They can even taste with their wings.

果蠅最複雜的感應器之一

One of the most sophisticated sensors a fly has

是一種被稱為「平衡棒」的構造。

is a structure called the halteres.

平衡棒其實就是陀螺儀。

The halteres are actually gyroscopes.

這個構造在飛行時 大約以 200 赫茲的速度擺動

These devices beat back and forth about 200 hertz during flight,

使動物可以用它們偵測身體旋轉，

and the animal can use them to sense its body rotation

並啟動非常、非常快速地糾正動作。

and initiate very, very fast corrective maneuvers.

但所有感官資訊 都需要經由大腦處理，

But all of this sensory information has to be processed

是的，果蠅有大腦的，

by a brain, and yes, indeed, flies have a brain,

一個大約有 10 萬神經元的大腦。

a brain of about 100,000 neurons.

已經有一些人在這次會議中

Now several people at this conference

提出果蠅可以作為神經科學的模型，

have already suggested that fruit flies could serve neuroscience

因為牠們具有簡單的大腦。

because they're a simple model of brain function.

然後我的演講的結語會是：

And the basic punchline of my talk is,

我想要直接反駁它。

I'd like to turn that over on its head.

我不認為牠們是任何東西的簡單模型。

I don't think they're a simple model of anything.

我認為果蠅是一個偉大的模型。

And I think that flies are a great model.

牠們是為飛行而生的偉大模型。

They're a great model for flies.

（笑聲）

(Laughter)

且讓我們研究一下這種簡單的想法。

And let's explore this notion of simplicity.

所以我認為很多的神經學家

So I think, unfortunately, a lot of neuroscientists,

都不幸地有些自戀。

we're all somewhat narcissistic.

當我們想到大腦時， 我們當然想自己的大腦。

When we think of brain, we of course imagine our own brain.

但請記住這種腦，

But remember that this kind of brain,

體積小很多很多的腦

which is much, much smaller

— 它沒有 1 千億神經元，它只有 1 萬神經元 —

— instead of 100 billion neurons, it has 100,000 neurons —

但這是這個星球上最常見的大腦形式

but this is the most common form of brain on the planet

而且已經存在 4 億年了。

and has been for 400 million years.

說它簡單公平嗎？

And is it fair to say that it's simple?

嗯，以神經元數量來說是簡單的，

Well, it's simple in the sense that it has fewer neurons,

但這是一個公平的指標嗎？

but is that a fair metric?

我認為這不是一個公平的指標。

And I would propose it's not a fair metric.

讓我們來想一想。 我們必須進行比較 ——

So let's sort of think about this. I think we have to compare --

（笑聲） ——

(Laughter) —

我們要比較大腦大小

we have to compare the size of the brain

與大腦可以做什麼。

with what the brain can do.

假設我們有王牌數，

So I propose we have a Trump number,

王牌數是這個男人可以做的事

and the Trump number is the ratio of this man's

跟大腦中神經元數目的比值。

behavioral repertoire to the number of neurons in his brain.

我們也可以計算出果蠅的王牌號。

We'll calculate the Trump number for the fruit fly.

現在，有多少人在這裡覺得果蠅的

Now, how many people here think the Trump number

王牌數會比較高？

is higher for the fruit fly?

（掌聲）

(Applause)

真是很聰明、很聰明的觀眾。

It's a very smart, smart audience.

雖然這比較不完全恰當， 但至少我認為是這樣的。

Yes, the inequality goes in this direction, or I would posit it.

好，我知道比較人和果蠅的行為

Now I realize that it is a little bit absurd

是有點荒謬。

to compare the behavioral repertoire of a human to a fly.

但讓我們看另一種動物：一隻小鼠。

But let's take another animal just as an example. Here's a mouse.

一隻小鼠的神經元數目大約是果蠅的 1 千倍。

A mouse has about 1,000 times as many neurons as a fly.

我以前研究過小鼠。 當我還在研究小鼠時，

I used to study mice. When I studied mice,

我講話速度慢很多。

I used to talk really slowly.

這在當我開始研究果蠅時產生了變化。

And then something happened when I started to work on flies.

（笑聲）

(Laughter)

我覺得如果你比較果蠅和小鼠的自然史，

And I think if you compare the natural history of flies and mice,

它們是可比的。 牠們都要覓食。

it's really comparable. They have to forage for food.

牠們都要求愛。

They have to engage in courtship.

牠們都會發生性關係。 牠們都要躲避獵食者。

They have sex. They hide from predators.

牠們做很多類似的事情。

They do a lot of the similar things.

但我想說果蠅做更多。

But I would argue that flies do more.

例如，我要給你們看一段影片，

So for example, I'm going to show you a sequence,

我不得不說， 我的一些資金來源來自軍方，

and I have to say, some of my funding comes from the military,

所以，我給你們這部機密影片，

so I'm showing this classified sequence

請你們離開這裡後必須絕口不提。好嗎？

and you cannot discuss it outside of this room. Okay?

所以想要你們看看果蠅尾巴

So I want you to look at the payload

的有效載荷。

at the tail of the fruit fly.

仔細看，

Watch it very closely,

你們會懂為什麼我的六歲兒子

and you'll see why my six-year-old son

現在想要成為一個神經學家。

now wants to be a neuroscientist.

等一下。

Wait for it.

噓。

Pshhew.

所以至少你們得承認， 如果果蠅沒有小鼠聰明，

So at least you'll admit that if fruit flies are not as clever as mice,

牠們至少達到鴿子的等級。 （笑聲）

they're at least as clever as pigeons. (Laughter)

現在，我想要傳達的不只是數字，

Now, I want to get across that it's not just a matter of numbers

還有果蠅大腦要用少量神經元

but also the challenge for a fly to compute

計算這所有資訊所面臨的挑戰。

everything its brain has to compute with such tiny neurons.

這是小鼠視覺中間神經元的美麗影像，

So this is a beautiful image of a visual interneuron from a mouse

這來自傑夫·歷之曼的實驗室，

that came from Jeff Lichtman's lab,

你們可以看到他在他的演講中

and you can see the wonderful images of brains

使用的精彩大腦影像。

that he showed in his talk.

在右上角你們將看到，

But up in the corner, in the right corner, you'll see,

在同樣的比例之下 一隻果蠅的視覺中間神經元。

at the same scale, a visual interneuron from a fly.

我把這展開。

And I'll expand this up.

它是一個精美複雜的神經元。

And it's a beautifully complex neuron.

它真是非常、 非常地小， 這必須克服許多生物物理的挑戰，

It's just very, very tiny, and there's lots of biophysical challenges

才能用極為微小的神經元來計算資訊。

with trying to compute information with tiny, tiny neurons.

神經元能有多小？ 那麼，讓我們看看這個有趣的昆蟲。

How small can neurons get? Well, look at this interesting insect.

牠看起來有點像果蠅。牠有翅膀，牠有眼睛，

It looks sort of like a fly. It has wings, it has eyes,

牠有天線，牠有腿， 也有複雜的生活史。

it has antennae, its legs, complicated life history,

牠是一種寄生蟲， 牠要到處飛，並尋找毛毛蟲

it's a parasite, it has to fly around and find caterpillars

當作寄主，

to parasatize,

牠的大腦很小，

but not only is its brain the size of a salt grain,

跟果蠅可相比較，

which is comparable for a fruit fly,

它也只有鹽粒大小。

it is the size of a salt grain.

所以這裡是一些其它類似規模的物種。

So here's some other organisms at the similar scale.

這個動物是草履蟲和變形蟲大小，

This animal is the size of a paramecium and an amoeba,

牠的大腦大約有 7 千神經元 —

and it has a brain of 7,000 neurons that's so small --

你知道有種叫做細胞體的東西，

you know these things called cell bodies you've been hearing about,

就是神經元的細胞核所在的地方？

where the nucleus of the neuron is?

這種動物沒有細胞體， 因為它們太佔空間了。

This animal gets rid of them because they take up too much space.

這是神經科學研究的新領域。

So this is a session on frontiers in neuroscience.

我認為神經科學其中 一個新領域就是要研究這類大腦的運作。

I would posit that one frontier in neuroscience is to figure out how the brain of that thing works.

但讓我們想一想。 如何讓少量的神經元做很多事？

But let's think about this. How can you make a small number of neurons do a lot?

我認為，從工程的角度看，

And I think, from an engineering perspective,

要多功能。

you think of multiplexing.

你們可以拿一個硬體，並用該硬體

You can take a hardware and have that hardware

在不同的時間做不同的事情

do different things at different times,

或用不同部分的硬體做不同的事情。

or have different parts of the hardware doing different things.

這些是我想要探討的兩個概念。

And these are the two concepts I'd like to explore.

但不是我想出來的概念，

And they're not concepts that I've come up with,

而是過去由其他人提出的概念。

but concepts that have been proposed by others in the past.

一個想法是來自於咀嚼螃蟹的經驗。

And one idea comes from lessons from chewing crabs.

我不是指吃螃蟹。

And I don't mean chewing the crabs.

我在巴爾的摩長大， 我非常、非常會吃螃蟹。

I grew up in Baltimore, and I chew crabs very, very well.

但我說的螃蟹的咀嚼。

But I'm talking about the crabs actually doing the chewing.

螃蟹的咀嚼實在令人著迷。

Crab chewing is actually really fascinating.

螃蟹在其甲殼下有個複雜的結構

Crabs have this complicated structure under their carapace

叫作胃磨機，

called the gastric mill

以各種不同方式磨牠們的食物。

that grinds their food in a variety of different ways.

而這是內鏡下看到的這種結構的影片。

And here's an endoscopic movie of this structure.

令人驚訝的是它是由一組非常小的神經元控制，

The amazing thing about this is that it's controlled

約有 20 多個神經元可以

by a really tiny set of neurons, about two dozen neurons

產生多種不同的運動模式，

that can produce a vast variety of different motor patterns,

它可以這樣做的原因 是這個螃蟹身上的小小神經節

and the reason it can do this is that this little tiny ganglion

實際上是被許多 神經調節物質所包圍。

in the crab is actually inundated by many, many neuromodulators.

你們剛剛已經聽過神經調節物質了。

You heard about neuromodulators earlier.

這個結構中可以改變、支配神經元的

There are more neuromodulators

神經調節物質比 構造中的神經元還多，