TED: Vilayanur Ramachandran - 3 clues to understanding your brain (2007) | Текст песни

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• TED: Vilayanur Ramachandran
• 3 clues to understanding your brain (2007)

00:11
Well, as Chris pointed out, I study the human brain, the functions and structure of the human brain. And I just want you to think for a minute about what this entails. Here is this mass of jelly, three-pound mass of jelly you can hold in the palm of your hand, and it can contemplate the vastness of interstellar space. It can contemplate the meaning of infinity and it can contemplate itself contemplating on the meaning of infinity. And this peculiar recursive quality that we call self-awareness, which I think is the holy grail of neuroscience, of neurology, and hopefully, someday, we'll understand how that happens.
00:51
OK, so how do you study this mysterious organ? I mean, you have 100 billion nerve cells, little wisps of protoplasm, interacting with each other, and from this activity emerges the whole spectrum of abilities that we call human nature and human consciousness. How does this happen? Well, there are many ways of approaching the functions of the human brain. One approach, the one we use mainly, is to look at patients with sustained damage to a small region of the brain, where there's been a genetic change in a small region of the brain. What then happens is not an across-the-board reduction in all your mental capacities, a sort of blunting of your cognitive ability. What you get is a highly selective loss of one function, with other functions being preserved intact, and this gives you some confidence in asserting that that part of the brain is somehow involved in mediating that function. So you can then map function onto structure, and then find out what the circuitry's doing to generate that particular function. So that's what we're trying to do.
01:51
So let me give you a few striking examples of this. In fact, I'm giving you three examples, six minutes each, during this talk. The first example is an extraordinary syndrome called Capgras syndrome. If you look at the first slide there, that's the temporal lobes, frontal lobes, parietal lobes, OK -- the lobes that constitute the brain. And if you look, tucked away inside the inner surface of the temporal lobes -- you can't see it there -- is a little structure called the fusiform gyrus. And that's been called the face area in the brain, because when it's damaged, you can no longer recognize people's faces. You can still recognize them from their voice and say, "Oh yeah, that's Joe," but you can't look at their face and know who it is, right? You can't even recognize yourself in the mirror. I mean, you know it's you because you wink and it winks, and you know it's a mirror, but you don't really recognize yourself as yourself.
02:42
OK. Now that syndrome is well known as caused by damage to the fusiform gyrus. But there's another rare syndrome, so rare, in fact, that very few physicians have heard about it, not even neurologists. This is called the Capgras delusion, and that is a patient, who's otherwise completely normal, has had a head injury, comes out of coma, otherwise completely normal, he looks at his mother and says, "This looks exactly like my mother, this woman, but she's an impostor. She's some other woman pretending to be my mother." Now, why does this happen? Why would somebody -- and this person is perfectly lucid and intelligent in all other respects, but when he sees his mother, his delusion kicks in and says, it's not mother.
03:21
Now, the most common interpretation of this, which you find in all the psychiatry textbooks, is a Freudian view, and that is that this chap -- and the same argument applies to women, by the way, but I'll just talk about guys. When you're a little baby, a young baby, you had a strong sexual attraction to your mother. This is the so-called Oedipus complex of Freud. I'm not saying I believe this, but this is the standard Freudian view. And then, as you grow up, the cortex develops, and inhibits these latent sexual urges towards your mother. Thank God, or you would all be sexually aroused when you saw your mother. And then what happens is, there's a blow to your head, damaging the cortex, allowing these latent sexual urges to emerge, flaming to the surface, and suddenly and inexplicably you find yourself being sexually aroused by your mother. And you say, "My God, if this is my mom, how come I'm being sexually turned on? She's some other woman. She's an impostor." It's the only interpretation that makes sense to your damaged brain.
04:19
This has never made much sense to me, this argument. It's very ingenious, as all Freudian arguments are -- (Laughter) -- but didn't make much sense because I have seen the same delusion, a patient having the same delusion, about his pet poodle. (Laughter) He'll say, "Doctor, this is not Fifi. It looks exactly like Fifi, but it's some other dog." Right? Now, you try using the Freudian explanation there. (Laughter) You'll start talking about the latent bestiality in all humans, or some such thing, which is quite absurd, of course.
04:52
Now, what's really going on? So, to explain this curious disorder, we look at the structure and functions of the normal visual pathways in the brain. Normally, visual signals come in, into the eyeballs, go to the visual areas in the brain. There are, in fact, 30 areas in the back of your brain concerned with just vision, and after processing all that, the message goes to a small structure called the fusiform gyrus, where you perceive faces. There are neurons there that are sensitive to faces. You can call it the face area of the brain, right? I talked about that earlier. Now, when that area's damaged, you lose the ability to see faces, right?
05:27
But from that area, the message cascades into a structure called the amygdala in the limbic system, the emotional core of the brain, and that structure, called the amygdala, gauges the emotional significance of what you're looking at. Is it prey? Is it predator? Is it mate? Or is it something absolutely trivial, like a piece of lint, or a piece of chalk, or a -- I don't want to point to that, but -- or a shoe, or something like that? OK? Which you can completely ignore. So if the amygdala is excited, and this is something important, the messages then cascade into the autonomic nervous system. Your heart starts beating faster. You start sweating to dissipate the heat that you're going to create from muscular exertion. And that's fortunate, because we can put two electrodes on your palm and measure the change in skin resistance produced by sweating. So I can determine, when you're looking at something, whether you're excited or whether you're aroused, or not, OK? And I'll get to that in a minute.
06:22
So my idea was, when this chap looks at an object, when he looks at his -- any object for that matter, it goes to the visual areas and, however, and it's processed in the fusiform gyrus, and you recognize it as a pea plant, or a table, or your mother, for that matter, OK? And then the message cascades into the amygdala, and then goes down the autonomic nervous system. But maybe, in this chap, that wire that goes from the amygdala to the limbic system, the emotional core of the brain, is cut by the accident. So because the fusiform is intact, the chap can still recognize his mother, and says, "Oh yeah, this looks like my mother." But because the wire is cut to the emotional centers, he says, "But how come, if it's my mother, I don't experience a warmth?" Or terror, as the case may be? Right? (Laughter) And therefore, he says, "How do I account for this inexplicable lack of emotions? This can't be my mother. It's some strange woman pretending to be my mother."
07:18
How do you test this? Well, what you do is, if you take any one of you here, and put you in front of a screen, and measure your galvanic skin response, and show pictures on the screen, I can measure how you sweat when you see an object, like a table or an umbrella. Of course, you don't sweat. If I show you a picture of a lion, or a tiger, or a pinup, you start sweating, right? And, believe it or not, if I show you a picture of your mother -- I'm talking about normal people -- you start sweating. You don't even have to be Jewish. (Laughter)
07:47
Now, what happens if you show this patient? You take the patient and show him pictures on the screen and measure his galvanic skin response. Tables and chairs and lint, nothing happens, as in normal people, but when you show him a picture of his mother, the galvanic skin response is flat. There's no emotional reaction to his mother, because that wire going from the visual areas to the emotional centers is cut. So his vision is normal because the visual areas are normal, his emotions are normal -- he'll laugh, he'll cry, so on and so forth -- but the wire from vision to emotions is cut and therefore he has this delusion that his mother is an impostor. It's a lovely example of the sort of thing we do: take a bizarre, seemingly incomprehensible, neural psychiatric syndrome and say that the standard Freudian view is wrong

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