Carl Schoonover: How to look inside the brain

75,240 views ・ 2012-05-17

TED


Please double-click on the English subtitles below to play the video.

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This is a thousand-year-old drawing of the brain.
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It's a diagram of the visual system.
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And some things look very familiar today.
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Two eyes at the bottom, optic nerve flowing out from the back.
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There's a very large nose
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that doesn't seem to be connected to anything in particular.
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And if we compare this
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to more recent representations of the visual system,
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you'll see that things have gotten substantially more complicated
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over the intervening thousand years.
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And that's because today we can see what's inside of the brain,
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rather than just looking at its overall shape.
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Imagine you wanted to understand how a computer works
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and all you could see was a keyboard, a mouse, a screen.
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You really would be kind of out of luck.
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You want to be able to open it up, crack it open,
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look at the wiring inside.
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And up until a little more than a century ago,
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nobody was able to do that with the brain.
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Nobody had had a glimpse of the brain's wiring.
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And that's because if you take a brain out of the skull
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and you cut a thin slice of it,
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put it under even a very powerful microscope,
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there's nothing there.
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It's gray, formless.
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There's no structure. It won't tell you anything.
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And this all changed in the late 19th century.
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Suddenly, new chemical stains for brain tissue were developed
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and they gave us our first glimpses at brain wiring.
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The computer was cracked open.
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So what really launched modern neuroscience
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was a stain called the Golgi stain.
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And it works in a very particular way.
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Instead of staining all of the cells inside of a tissue,
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it somehow only stains about one percent of them.
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It clears the forest, reveals the trees inside.
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If everything had been labeled, nothing would have been visible.
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So somehow it shows what's there.
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Spanish neuroanatomist Santiago Ramon y Cajal,
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who's widely considered the father of modern neuroscience,
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applied this Golgi stain, which yields data which looks like this,
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and really gave us the modern notion of the nerve cell, the neuron.
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And if you're thinking of the brain as a computer,
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this is the transistor.
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And very quickly Cajal realized
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that neurons don't operate alone,
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but rather make connections with others
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that form circuits just like in a computer.
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Today, a century later, when researchers want to visualize neurons,
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they light them up from the inside rather than darkening them.
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And there's several ways of doing this.
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But one of the most popular ones
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involves green fluorescent protein.
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Now green fluorescent protein,
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which oddly enough comes from a bioluminescent jellyfish,
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is very useful.
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Because if you can get the gene for green fluorescent protein
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and deliver it to a cell,
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that cell will glow green --
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or any of the many variants now of green fluorescent protein,
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you get a cell to glow many different colors.
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And so coming back to the brain,
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this is from a genetically engineered mouse called "Brainbow."
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And it's so called, of course,
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because all of these neurons are glowing different colors.
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Now sometimes neuroscientists need to identify
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individual molecular components of neurons, molecules,
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rather than the entire cell.
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And there's several ways of doing this,
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but one of the most popular ones
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involves using antibodies.
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And you're familiar, of course,
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with antibodies as the henchmen of the immune system.
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But it turns out that they're so useful to the immune system
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because they can recognize specific molecules,
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like, for example, the coat protein
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of a virus that's invading the body.
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And researchers have used this fact
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in order to recognize specific molecules inside of the brain,
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recognize specific substructures of the cell
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and identify them individually.
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And a lot of the images I've been showing you here are very beautiful,
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but they're also very powerful.
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They have great explanatory power.
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This, for example, is an antibody staining
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against serotonin transporters in a slice of mouse brain.
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And you've heard of serotonin, of course,
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in the context of diseases like depression and anxiety.
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You've heard of SSRIs,
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which are drugs that are used to treat these diseases.
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And in order to understand how serotonin works,
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it's critical to understand where the serontonin machinery is.
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And antibody stainings like this one
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can be used to understand that sort of question.
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I'd like to leave you with the following thought:
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Green fluorescent protein and antibodies
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are both totally natural products at the get-go.
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They were evolved by nature
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in order to get a jellyfish to glow green for whatever reason,
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or in order to detect the coat protein of an invading virus, for example.
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And only much later did scientists come onto the scene
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and say, "Hey, these are tools,
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these are functions that we could use
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in our own research tool palette."
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And instead of applying feeble human minds
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to designing these tools from scratch,
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there were these ready-made solutions right out there in nature
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developed and refined steadily for millions of years
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by the greatest engineer of all.
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Thank you.
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(Applause)
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