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  • (Zombie noises) Doctor 1: So, here we are again.

  • You know, I've been thinking. Why is this thing so angry?

  • Doctor 2: Maybe he's just hungry.

  • D1: (Laughs) I'm not going in there to feed it.

  • No, this seems like something very primal.

  • D2: This is kind of a hard one,

  • because we don't really have any biological definitions for emotions like anger.

  • Sure, brain imaging studies have shown that some brain regions are more active when people are angry,

  • but these are almost always correlational.

  • When it's warmer outside, people wear less clothing,

  • but if I strip down to my birthday suit, it doesn't make it sunny.

  • D1: (Laughs) It's like having someone run on a treadmill and saying

  • "Look at how much more his arms move when he runs faster!

  • The arms must be where running happens."

  • D2: That's why working with people with brain lesions is so important to neuroscience.

  • It adds some causal evidence that a brain area might be required for a behavior.

  • Same with brain simulation studies.

  • If stimulating a brain area causes a behavior,

  • then that's good evidence that the brain region is involved in that behavior.

  • So like studies with cats in the 1950s

  • showed that stimulating a small almond-shaped area deep in the brain called the amygdala

  • leads to aggressive or predatory behaviors.

  • These things look pretty aggressive to me.

  • D1: Right. But other studies have shown that stimulating different parts of the amygdala

  • can actually suppress predatory behaviors.

  • So it's kind of a complicated little brain structure.

  • D2: Yeah. And fMRI studies have found that the amygdala is active in violent criminals.

  • D1: Whoa, whoa, whoa. Careful there.

  • Just because criminals have the same active brain regions as people who are angry,

  • doesn't mean that they're inherently aggressive.

  • That's like saying because I kiss with the same face hole that I use to burp,

  • then these two things are related.

  • It's a false equivalence.

  • D2: Huh! Never thought of it like that. That's a good point.

  • D1: You know, the amygdala is part of the Papez circuit.

  • This system was discovered by James Papez, who used the rabies virus to lesion different areas in the cat's brain.

  • He found that the amygdala was physically connected to another region called the hippocampus --

  • a little seahorse-shaped area that is needed to turn short-term memories into long-term memories.

  • It's thought that this connection between the amygdala and hippocampus

  • links emotion and memory together,

  • so that you remember really emotional stuff better than boring everyday things.

  • D2: Yeah, like Patient H.M. In the 1950s, surgeons removed both his left and right hippocampuses

  • to treat his epilepsy.

  • But after the surgery, he couldn't remember any new information for longer than a few minutes.

  • Zombies appear to be pretty forgetful, wouldn't you agree?

  • D1: (Laughs) Absolutely. Between the amygdala-related aggression,

  • and memory deficits from the hippocampus,

  • Papez may have actually accidentally created the first zombie cat.

  • D2: Aw, come on now, let's not get carried away.

  • But now we do have some testable hypotheses.

  • I'd put money on its aggression and memory problems being linked to abnormalities

  • in its amygdala and hippocampus, respectively.

  • D1: Great! So all we need to do now is figure out how to experimentally test this.

  • Do you think it'll let us examine its brain to verify our hypothesis?

  • D2: Uh, you know, I think I might be more comfortable not knowing the answer to this one.

  • D1: Hmm. Maybe we could get a graduate student to do it for us?

(Zombie noises) Doctor 1: So, here we are again.


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B1 中級

TED-ED】ゾンビを診断する:脳と行動 - ティム・ベルスティネン&ブラッドリー・ボイテック (【TED-Ed】Diagnosing a zombie: Brain and behavior - Tim Verstynen & Bradley Voytek)

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    劉淑萍 に公開 2021 年 01 月 14 日