一瞬之光

神經元何以建構人類文明

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主講人:V.S. Ramachandran拉瑪錢德朗/神經學專家

    印度裔美國人,於加州大學從事認知醫學的研究

線上觀看TED影音內容

http://tinyurl.com/7cmoj6e

今天,我想和大家一探大腦的奧秘, 我在加州大學做相關研究。 試著思考一下這個問題。 這裏有一堆肉, 大概重三磅左右, 可以用一掌來握住。 但它卻可以探究浩瀚的星際空間; 可以探究無限 的意義; 可以探究自身存在的意義; 可以探究上帝的本質。

這是世界上最 不可思議之事。 這是人類面臨 的最大難題之一。 這一切是怎麼 來的? 正如你們所 知,腦組織是由神經元所組成的。 這就是神經 元。 成人腦組織裏 含有一千億個神經元。 每個神經元與 其他神經元的 交接點約有一 千至一萬處。 基於此,人們 對之進行了計算, 並得出各種大 腦活動的組合總量 超過了宇宙中 基本粒子的數量。

所以,我們應 該如何研究大腦? 一種方法是觀 察那些有受過腦部 損傷的人, 以 來研究他們行為的變遷。 這是我於上次 TED大會上所講的內容。 今天我將講述 一種新的方法。 這種方法是將 電極線置放於大腦的不同部位, 以記錄單個神 經細胞的活動性。 頗類似於竊聽 神經細胞在大腦內的活動。

最近,義大利 帕爾馬的 研究人員們, 亦就是裏左拉蒂與其同事們 在大腦前額葉 發現了一組神 經元, 這組神經元被 他們稱作鏡像神經元。 此外,大腦裏 面還有一組神經元, 稱作運動神經 元,也位於大腦的前半部分, 這組神經元是 50年前的發現。 當我們要做某 種運動時,這組神經元就會發射資訊至相關器官。 例如,假若我 這樣做,我向前屈伸,然後抓住一隻蘋果, 一個運動神經 元則會[向我的手]發射一組資訊。 假如我向前 屈伸,並回拉一件物品,另外一個神經元則會 發射另一組 資訊 以控制我的行動。 很早以前, 這些運動神經元就被發現了。

不過,裏佐 拉蒂他們發現 這組神經元 中包含著另外一組神經元, 大約百分之 二十左右。 這些神經元是會當我觀看他人 行動時, 所以,當我 向前抓住某物件時,有個神經元會發出相關資訊, 可是若我觀 看喬做相同的動作時,另一個神經元也會發出相關資訊。 這實在是令 人震驚。 因為這表 明,神經元也會 採納別人的 觀點。 幾乎就是模 仿了他人的動作, 有如虛擬現 實仿真。

那麼,這些 鏡像神經元有何存在意義呢? 這裏我必須 引入模仿和仿真的概念。 假使我們要 模仿一種複雜的行為, 那麼我們的 大腦則需要採納他人的行為觀點。 因此模仿和 仿真是非常重要的。 好了,它們 為什麼重要呢? 讓我們看看 下一張幻燈片。 你怎樣進行 模仿?模仿為什麼重要? 鏡像神經 元,模仿和仿真。

現在,讓我 們從人類文化方面入手。 讓我們回到 七萬五千年至十萬年前時, 我們來觀測 下人類進化的過程,結果發現 于七萬五千 年前左右,一件重大事件影響了人類的發展。 那就是,各 種獨特的“人類”技巧 突然出現以 及迅速傳播。這些技巧包括 工具的使 用、 火的使用、 房屋的出現和語言交流, 以及讀取他 人心思的能力和 理解他人的 行為。 這一切都相 對地較快發生。

原始人類的 大腦形狀大約于四至五十萬年前 就已經發育 至今人的形狀, 不過這些事 件則是十萬年前才快速地發生。 我認為這些 事件的產生是 源于先進的 鏡像神經元系統的突然浮現, 這些神經元 將允許你模仿他人的行為 所以當氏族 的某一成員偶然 發現,火的 使用, 而非凋零消 亡, 這種方法將會橫向傳播於氏族中, 或者代代縱 向傳播。

所以,這是 一種拉馬克式進化, 而非達爾文 式。 達爾文式進 化是異乎緩慢的,它大概需要幾千年的時間來產生效用。 若要使一隻 北極熊進化出一件外衣, 則需要他們 經過數千代的傳承,或許需要十萬年方能得出外衣。 一個人類小 孩,則僅需觀看他的父母 如何屠殺另 一隻北極熊, 將其剝皮拆 骨,用來製造外衣。 小孩因此可 以快速掌握這一技能。 北極熊需要 十萬年才得以進化出外衣, 人類小孩僅 僅要五分鐘或者十分鐘就學會了。 當他們學會 之後,這項技能將以 燎原之勢散 播於他們的氏族當中。

這就是本 源。文化就是模仿 複雜的行為 活動,而文明則產於此。 現在我將講 到另外一種鏡像神經元, 擔負另外的 功能。 有些鏡像神 經元 只管活動, 換句話來 說,假如某人觸碰了我, 我的手,位 於軀體感覺皮層的神經元 將會發出一 組資訊。 但同一個神 經元,在某些情況下, 當我觀看他 人被觸碰時,也會發出資訊。 注意,我是 說他人被觸碰。

大多數的神 經元都會於我被觸碰時 發出資訊。 不同的神經元負責不同的身體區域。 偏偏有小部 分的神經元在我觀看他人被觸碰時 也會發出相 同的資訊。 因此,這裏 又有一群神經元 參與進了你 與他人之間的共鳴。 不過問題 是:假如我只觀看他人被觸碰, 那麼為什麼 我不會 有那種被觸 碰的感覺呢? 我與那人產 生共鳴,但我並未產生觸碰感。 那是因為我 們皮膚上有感受器, 一種痛感受 器,它會向大腦 回饋道: “切莫擔心,你還未被觸碰呢。 注意,是另 外一個人被觸碰呢, 而不是我們 自己呀。 要不我們自 己則會搞混呢。”

所以,這裏 會有一種回饋信號 以阻止鏡像 神經元所發出的信號, 從而使你避 免感覺到那股錯誤的觸碰感。 然而,當你 移除你的手臂時, 或者向你的 手臂注射麻醉劑, 從而麻醉臂 叢神經 使你無法感 覺到你的手臂的時候, 假如你現在 觀看他人手掌被觸碰, 你的手掌也 會有被觸碰的感覺。 換句話說, 你將你與他人之間的 隔膜溶解 了。 因此,我稱 他們為甘地神經元,或者是共鳴神經元。 (笑聲)

這並不是種 抽象的道理, 將你與他人 隔開的 就是你的皮 膚。 移除你的皮 膚,你將會與他人感同身受。 你將你與他 人之間的隔膜溶解了。 這些當然就 是大部分東方哲學的基礎。 那就是沒有 真實獨立的自我 將你與他人 隔開,從而以審視這個世界, 審視他人。 事實上,我 們與他人交結並不只是通過Facebook或是網路, 而是各式各 樣的神經元。 在這間大廳 裏,有一群的神經元正互相交談著呢。 你與他人的 意識 並沒有任何 真正的差異。

這並不是晦 澀難懂的哲學。 這是由基礎 神經學所引申出來的。 當你接診一 位有幻肢的病人時,幻肢即是 截肢或殘廢 的患者仍感到自己有該肢體的存在,當他觀察他人 被觸碰時, 他也會有此感。 令人震驚的 是, 當你患有幻 肢痛時,你對他人的手掌 進行按摩 時, 你的疼痛感 便會減輕。 這是因為你 的神經元 正獲取他人 被按摩時 所獲得的舒 適感。

這是我最後 一張幻燈片。 長期以來, 人們都將科學與 人文學科分 開, C.P.斯 諾指出兩種文化: 一種是科 學,一種是人文; 將永不相 見。 而我則認為 鏡像神經元系統將再次引起 一場思潮, 將使你重新思考什麼是意識, 什麼代表自 我, 什麼將你于 他人區分開, 什麼使你與 他人產生共鳴, 什麼使文化 與文明產生, 什麼才是人 類所獨有的事物。謝謝。

I'd like to talk to you today about the human brain, which is what we do research on at the University of California. Just think about this problem for a second. Here is a lump of flesh, about three pounds, which you can hold in the palm of your hand. But it can contemplate the vastness of interstellar space. It can contemplate the meaning of infinity, ask questions about the meaning of its own existence, about the nature of God.

And this is truly the most amazing thing in the world. It's the greatest mystery confronting human beings: How does this all come about? Well, the brain, as you know, is made up of neurons. We're looking at neurons here. There are 100 billion neurons in the adult human brain. And each neuron makes something like 1,000 to 10,000 contacts with other neurons in the brain. And based on this, people have calculated that the number of permutations and combinations of brain activity exceeds the number of elementary particles in the universe.

So, how do you go about studying the brain? One approach is to look at patients who had lesions in different part of the brain, and study changes in their behavior. This is what I spoke about in the last TED. Today I'll talk about a different approach, which is to put electrodes in different parts of the brain, and actually record the activity of individual nerve cells in the brain. Sort of eavesdrop on the activity of nerve cells in the brain.

Now, one recent discovery that has been made by researchers in Italy, in Parma, by Giacomo Rizzolatti and his colleagues, is a group of neurons called mirror neurons, which are on the front of the brain in the frontal lobes. Now, it turns out there are neurons which are called ordinary motor command neurons in the front of the brain, which have been known for over 50 years. These neurons will fire when a person performs a specific action. For example, if I do that, and reach and grab an apple, a motor command neuron in the front of my brain will fire. If I reach out and pull an object, another neuron will fire, commanding me to pull that object. These are called motor command neurons that have been known for a long time.

But what Rizzolatti found was a subset of these neurons, maybe about 20 percent of them, will also fire when I'm looking at somebody else performing the same action. So, here is a neuron that fires when I reach and grab something, but it also fires when I watch Joe reaching and grabbing something. And this is truly astonishing. Because it's as though this neuron is adopting the other person's point of view. It's almost as though it's performing a virtual reality simulation of the other person's action.

Now, what is the significance of these mirror neurons? For one thing they must be involved in things like imitation and emulation. Because to imitate a complex act requires my brain to adopt the other person's point of view. So, this is important for imitation and emulation. Well, why is that important? Well, let's take a look at the next slide. So, how do you do imitation? Why is imitation important? Mirror neurons and imitation, emulation.

Now, let's look at culture, the phenomenon of human culture. If you go back in time about [75,000] to 100,000 years ago, let's look at human evolution, it turns out that something very important happened around 75,000 years ago. And that is, there is a sudden emergence and rapid spread of a number of skills that are unique to human beings like tool use, the use of fire, the use of shelters, and, of course, language, and the ability to read somebody else's mind and interpret that person's behavior. All of that happened relatively quickly.

Even though the human brain had achieved its present size almost three or four hundred thousand years ago, 100,000 years ago all of this happened very, very quickly. And I claim that what happened was the sudden emergence of a sophisticated mirror neuron system, which allowed you to emulate and imitate other people's actions. So that when there was a sudden accidental discovery by one member of the group, say the use of fire, or a particular type of tool, instead of dying out, this spread rapidly, horizontally across the population, or was transmitted vertically, down the generations.

So, this made evolution suddenly Lamarckian, instead of Darwinian. Darwinian evolution is slow; it takes hundreds of thousands of years. A polar bear, to evolve a coat, will take thousands of generations, maybe 100,000 years. A human being, a child, can just watch its parent kill another polar bear, and skin it and put the skin on its body, fur on the body, and learn it in one step. What the polar bear took 100,000 years to learn, it can learn in five minutes, maybe 10 minutes. And then once it's learned this it spreads in geometric proportion across a population.

This is the basis. The imitation of complex skills is what we call culture and is the basis of civilization. Now there is another kind of mirror neuron, which is involved in something quite different. And that is, there are mirror neurons, just as there are mirror neurons for action, there are mirror neurons for touch. In other words, if somebody touches me, my hand, neuron in the somatosensory cortex in the sensory region of the brain fires. But the same neuron, in some cases, will fire when I simply watch another person being touched. So, it's empathizing the other person being touched.

So, most of them will fire when I'm touched in different locations. Different neurons for different locations. But a subset of them will fire even when I watch somebody else being touched in the same location. So, here again you have neurons which are enrolled in empathy. Now, the question then arises: If I simply watch another person being touched, why do I not get confused and literally feel that touch sensation merely by watching somebody being touched? I mean, I empathize with that person but I don't literally feel the touch. Well, that's because you've got receptors in your skin, touch and pain receptors, going back into your brain and saying "Don't worry, you're not being touched. So, empathize, by all means, with the other person, but do not actually experience the touch, otherwise you'll get confused and muddled."

Okay, so there is a feedback signal that vetoes the signal of the mirror neuron preventing you from consciously experiencing that touch. But if you remove the arm, you simply anesthetize my arm, so you put an injection into my arm, anesthetize the brachial plexus, so the arm is numb, and there is no sensations coming in, if I now watch you being touched, I literally feel it in my hand. In other words, you have dissolved the barrier between you and other human beings. So, I call them Gandhi neurons, or empathy neurons. (Laughter)

And this is not in some abstract metaphorical sense. All that's separating you from him, from the other person, is your skin. Remove the skin, you experience that person's touch in your mind. You've dissolved the barrier between you and other human beings. And this, of course, is the basis of much of Eastern philosophy, and that is there is no real independent self, aloof from other human beings, inspecting the world, inspecting other people. You are, in fact, connected not just via Facebook and Internet, you're actually quite literally connected by your neurons. And there is whole chains of neurons around this room, talking to each other. And there is no real distinctiveness of your consciousness from somebody else's consciousness.

And this is not mumbo-jumbo philosophy. It emerges from our understanding of basic neuroscience. So, you have a patient with a phantom limb. If the arm has been removed and you have a phantom, and you watch somebody else being touched, you feel it in your phantom. Now the astonishing thing is, if you have pain in your phantom limb, you squeeze the other person's hand, massage the other person's hand, that relieves the pain in your phantom hand, almost as though the neuron were obtaining relief from merely watching somebody else being massaged.

So, here you have my last slide. For the longest time people have regarded science and humanities as being distinct. C.P. Snow spoke of the two cultures: science on the one hand, humanities on the other; never the twain shall meet. So, I'm saying the mirror neuron system underlies the interface allowing you to rethink about issues like consciousness, representation of self, what separates you from other human beings, what allows you to empathize with other human beings, and also even things like the emergence of culture and civilization, which is unique to human beings. Thank you.

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人們 對之進行了計算, 並得出各種大 腦活動的組合總量 超過了宇宙中 基本粒子的數量。
我對於這種計算方法存疑,他是怎麼計的?

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