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  • Imagine, for a second, a duck teaching a French class,

    花個幾秒鐘想像一下 一隻鴨子在教法文課

  • a ping-pong match in orbit around a black hole,

    一場在黑洞旁軌道上的乒乓球賽

  • a dolphin balancing a pineapple.

    一隻海豚試圖平衡一顆鳳梨

  • You probably haven't actually seen any of these things,

    你也許從沒看過剛剛的任何一樣東西

  • but you could imagine them instantly.

    但你可以立刻想像出他們

  • How does your brain produce an image of something you've never seen?

    你的大腦是怎麼產生出一張你從沒看過東西的畫面呢?

  • That may not seem hard,

    那似乎不是太困難

  • but that's only because we're so used to doing it.

    但那只是因為我們非常習慣於這件事了

  • It turns out that this is actually a complex problem

    這實際上是個複雜的問題

  • that requires sophisticated coordination inside your brain.

    你的大腦中需要複雜的協調合作

  • That's because to create these new, weird images,

    創造出這些新奇的畫面

  • your brain takes familiar pieces and assembles them in new ways,

    你的大腦需要取出相近的片段 再將他們用不同的方式組合起來

  • like a collage made from fragments of photos.

    就像利用各部份相片完成一幅拼貼畫作

  • The brain has to juggle a sea of thousands of electrical signals

    大腦必須應付海一般成千上萬的電子訊號

  • getting them all to their destination at precisely the right time.

    並在準確的時間點將他們放到各自的目的地

  • When you look at an object,

    當你看著一樣東西

  • thousands of neurons in your posterior cortex fire.

    後皮質裡上千個神經元正受到激發

  • These neurons encode various characteristics of the object:

    這些神經元編碼出各種關於這樣東西的特性:

  • spiky, fruit, brown, green, and yellow.

    帶刺的、水果、咖啡色、綠色和黃色

  • This synchronous firing strengthens the connections between that set of neurons,

    這個同步激發使的那些神經元彼此間的連結更強

  • linking them together into what's known as a neuronal ensemble,

    讓他們結成了我們所知道的神經元集群

  • in this case the one for pineapple.

    鳳梨這個例子中

  • In neuroscience, this is called the Hebbian principle,

    在神經科學裡稱之為赫布理論

  • neurons that fire together wire together.

    那些共同受到激發有所連結的神經元

  • If you try to imagine a pineapple later,

    假設過了一下子,你試圖去想像一個鳳梨

  • the whole ensemble will light up, assembling a complete mental image.

    整個集群會亮起來並組合出一個完整的心理意象

  • Dolphins are encoded by a different neuronal ensemble.

    海豚則會由不同神經元集群來編碼出來

  • In fact, every object that you've seen

    事實上,你看到的每一樣物品

  • is encoded by a neuronal ensemble associated with it,

    皆由一個神經元集群來產生與它相關的編碼

  • the neurons wired together by that synchronized firing.

    藉由同時受到激發而使那些神經元連結在一起

  • But this principle doesn't explain the infinite number of objects

    然而這個理論並無法解釋我們如何想像出無限多種物品

  • that we can conjure up in our imaginations without ever seeing them.

    即使我們從未見過那些東西

  • The neuronal ensemble for a dolphin balancing a pineapple doesn't exist.

    "一隻海豚試圖平衡鳳梨"這樣的神經元集群並不存在

  • So how come you can imagine it anyway?

    那麼,你為什麼能想像這個畫面呢?

  • One hypothesis, called the Mental Synthesis Theory,

    有一個假說叫"心理合成理論"

  • says that, again, timing is key.

    又再次重申了關鍵在於時間點

  • If the neuronal ensembles for the dolphin and pineapple

    如果海豚與鳳梨的兩個神經元集群

  • are activated at the same time,

    同時受被激發

  • we can perceive the two separate objects as a single image.

    我們便能在同一畫面中感知到兩個不同物品

  • But something in your brain has to coordinate that firing.

    但必須由你大腦中的某樣東西來協調這樣的激發

  • One plausible candidate is the prefrontal cortex,

    最有可能的角色就是前額皮質

  • which is involved in all complex cognitive functions.

    因為它幾乎參與了所有複雜的認知行為

  • Prefrontal cortex neurons are connected to the posterior cortex

    前額皮質中的神經元與後皮質連結在一起

  • by long, spindly cell extensions called neural fibers.

    藉由長且纖細的組織延伸 稱之為神經纖維

  • The mental synthesis theory proposes that like a puppeteer pulling the strings,

    心理合成理論認為如同木偶師操縱著繩子

  • the prefrontal cortex neurons send electrical signals

    前額皮質神經元傳送出電子訊號

  • down these neural fibers

    沿著那些神經纖維

  • to multiple ensembles in the posterior cortex.

    抵達數個後皮質中的神經元集群

  • This activates them in unison.

    使得他們行為一致

  • If the neuronal ensembles are turned on at the same time,

    若那些神經元群集能夠在同時受到激發

  • you experience the composite image just as if you'd actually seen it.

    你就如真的看見一般想像出合成畫面

  • This conscious purposeful synchronization

    這個感知有目的的藉由前額皮質

  • of different neuronal ensembles by the prefrontal cortex

    使得數個神經元集群達成同步

  • is called mental synthesis.

    稱之為心理合成

  • In order for mental sythesis to work,

    為了使它順利運作

  • signals would have to arrive at both neuronal ensembles at the same time.

    訊號必須同時抵達神經元集群

  • The problem is that some neurons

    會出現的問題是

  • are much farther away from the prefrontal cortex than others.

    有些神經元比其他前額皮質中的神經元遠的多

  • If the signals travel down both fibers at the same rate,

    如果訊號以同樣速度在神經纖維中傳輸

  • they'd arrive out of sync.

    他們並無法同時到達

  • You can't change the length of the connections,

    你無法改變連結的長度

  • but your brain, especially as it develops in childhood,

    但你的大腦,特別是在孩童發展階段

  • does have a way to change the conduction velocity.

    的確有辦法改變傳導速度

  • Neural fibers are wrapped in a fatty substance called myelin.

    神經纖維外層包裹著富含脂肪的物質稱為髓鞘

  • Myelin is an insulator

    髓鞘是一種絕緣體

  • and speeds up the electrical signals zipping down the nerve fiber.

    可以加快電子訊號在神經纖維中的傳送速度

  • Some neural fibers have as many as 100 layers of myelin.

    有些神經纖維外甚至包著100層之多的髓鞘

  • Others only have a few.

    其他的則數量較少

  • And fibers with thicker layers of myelin

    那些包裹著較厚髓鞘層的神經纖維

  • can conduct signals 100 times faster or more

    相較於沒那麼厚的神經纖維

  • than those with thinner ones.

    傳導速度可達到或超過100倍

  • Some scientists now think that this difference in myelination

    部份科學家開始認為這些髓鞘層的厚薄程度

  • could be the key to uniform conduction time in the brain,

    也許就是平衡大腦中傳導時間的關鍵

  • and consequently, to our mental synthesis ability.

    所以,對於我們心理合成的能力

  • A lot of this myelination happens in childhood,

    大部分的髓鞘生長於孩童時期

  • so from an early age,

    因此小時候

  • our vibrant imaginations may have a lot to do with building up brains

    我們活躍的想像力對於建構大腦有很大的作用

  • whose carefully myelinated connections

    有著髓鞘良好發展的連結

  • can craft creative symphonies throughout our lives.

    能作出富有創造力的生命樂章

Imagine, for a second, a duck teaching a French class,

花個幾秒鐘想像一下 一隻鴨子在教法文課

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B2 中高級 中文 TED-Ed 神經元 纖維 皮質 激發 前額

【TED-Ed】想象力的神經科學--安德烈-維謝茲基(Andrey Vyshedskiy) (【TED-Ed】The neuroscience of imagination - Andrey Vyshedskiy)

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    小爸 發佈於 2021 年 01 月 14 日
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