TEDEd のホームページへはこちら
から。
直接、ここ
で観ることもできます。
しかし脳は外観からその役割を知ることは困難
筋肉へ送られる信号は同じ
ベースの音は波長が長く電流も大きい
４．これを見て神経科学に興味を持ってくれたらうれしい
neurons ：ニューロン、脳細胞
eavesdrop ：聞き耳を立てる、盗聴する
spike ：波形の急に飛び出した山のこと
anesthetize ：麻痺させる
cold blooded ：冷血動物、変温動物、外部の温度によって体温が変化する動物、爬虫類、魚類、昆虫が代表例
chillax ：chill out（落ち着く）と relax（リラックス）の合成語
prickly ：棘
zip ：高速で送信する
axon ：神経軸？脚から脳までをつなぐ背骨の中を通っている部分を指していると思います
action potential ：活動電位、神経細胞同士の情報伝達のために生じる電気のこと
perceive ：気づく、分かる
current ：電流
【transcript】
When you think about the brain,it's sort of a difficult thing to derstand, because if I were to ask you right now, how does the heart work, you would instantly tell me it's a pump. It pumps blood.
And if I were to ask you how your lungs work, you would say it exchanges oxygen for carbon dioxide. That's easy.
Now if I were to ask you how the brain works, it's a hard thing to understand because you can't just look at a brain and understand what it is. It's not a mechanical object, it's not a pump, it's not an airbag. It's just like, if you held it in your hand when it was dead, it's just a piece of fat. And so to understand how the brain works, you have to go inside a living brain. Because the brain's not mechanical, the brain is electrical and it's chemical.
Your brain is made out of 100 billion cells, and these cells are called neurons. And these neurons communicate with each other with electricity. And we're going to eavesdrop in on a conversation between two cells, and we're going to listen to something called a spike.
But we're not going to record my brain or your brain or your teacher's brains, we're going to use our good friend the cockroach. Not just because I think they're cool, but because they have brains very similar to ours.
And so if you learn a little bit about how their brains work, we're going to learn a lot about how our brains work.
So I'm going to put them in some ice water here and then ...
(Audience: Ew!) ... yeah ...
So what's happening right now is that they're becoming anesthetized, because they're cold blooded, they become the temperature of the water and they can't control it so they just basically "chillax," right? They're not going to be able to feel anything, and that may just tell you a little bit about what we're going to be doing.
We're going to be doing a scientific experiment to understand the brain.
So ... This is the leg of a cockroach and a cockroach has all these beautiful hairs and pricklies all over it. Underneath each one of those is a cell, and this cell's a neuron, and this neuron's going to send information about wind or vibrations. If you ever try to catch a cockroach, it's hard because they can feel you coming before you're even there, they start running. So these cells are zipping up this information up to the brain using those little axons with electronic messages in there.
So we're going to record by sticking a pin right in there.
So we need to take off the leg of a cockroach --Don't worry, they'll grow back --Then we're going to put two pins in there. One of the pins, these are metal pins, will pick up this electronic message, this electric message is going by.
So, we're now going to do the surgery, let's see if you guys can see this.
Yeah, it's gross ...
All right ... so there we go ...
You guys can see his leg right there.
So now I'm going to take this leg, I'm going to put it in this invention that we came up with called the Spikerbox -- and this replaces lots of expensive equipment in a research lab so you guys can do this in your own high schools, or in your own basements if it's me --
So, there. (Laughter)
Can you guys see that? Alright, so I'm going to go ahead and turn this on. I'm going to plug it in. (Sound of neurons firing)
To me, this is the most beautiful sound in the world. This is what your brain is doing right now. You have 100 billion cells making these raindrop-type noises. So let's go ahead and take a look at what it looks like, let's pull it up on the iPad screen. I plugged my iPad into here as well. So remember what we said about the axon, what we said it looks like, looks like a spike.
So we're going to take a look at what one of them looks like in just a brief second. We're going to tap here, so we can sort of average this guy. So there we see it. That's an action potential. You've got 100 billion cells in your brain doing this right now, sending all this information back about what you're seeing, what you're hearing.
So we also said this is a cell that's going to be taking up information about vibrations in the wind. So what if we do an experiment?
We can actually blow on this and hear if we see a change. Are you guys going to be ready for this? If I blow on it you tell me if you hear anything.
(Sound of spikes reacting to wind)
Let me just touch this with a little pen here.
(Noise)
That's actually the neural firing range. That actually took a while in neuroscience to understand this. This is called rate coding, which is that the harder you press on something, the more spikes there are, and all that information is coming up to your brain. That's how you perceive things.
So that's one way of doing an experiment with electricity. The other way is that your brain is not only taking in electrical impulses, you're also sending out. That's how you move your muscles around.
Let's see what happens if I've plugged in something that's electric into the cockroach leg here.
I'm going to take two pins, I'm going to plug them onto the cockroach. I'm going to take the other end, I'm going to plug in into my iPod. It's my iPhone actually. I don't know if you guys know this, but do you guys know how your earbuds work in your ears? You have a battery in your phone, your iPod, right? It's sending electrical current into these magnets in your earbuds which shake back and forth and allow you to hear things. But that electric current's the same currency that our brain uses so we can send that directly to our cockroach leg and hopefully if this works, we can actually see what happens when we play music into the cockroach. Let's take a look.
(Music beat) Can we turn it up? There we go.
(Music beats) (Audience reacts and gasps) So what's happening?
(Music beats)
So you see what's moving. It's moving on the bass. All those audio files out there. If you have awesome, kicking car stereos, you know, the bass speakers are the biggest speakers. The biggest speakers have the longest waves, the longest waves have the most current, and the current is what's causing these things to move.
So it's not just speakers that are causing electricity. Microphones also cause electricity.
(Beat)
So I'm going to go ahead and invite another person out on the stage here to help me out with this. So there we go.
(Beatboxing)
This is the first time this has ever happened in the history of mankind. Human beatbox to a cockroach leg.
When you guys go back to your high school, think about neuroscience and how you guys can begin the neuro-revolution.
Thank you very much. Bye bye. (Applause)