中級 1249 分類 收藏
開始影片後,點擊或框選字幕可以立即查詢單字
字庫載入中…
回報字幕錯誤
Imagine, for a second, a duck teaching a French class,
a ping-pong match in orbit around a black hole,
a dolphin balancing a pineapple.
You probably haven't actually seen any of these things,
but you could imagine them instantly.
How does your brain produce an image of something you've never seen?
That may not seem hard,
but that's only because we're so used to doing it.
It turns out that this is actually a complex problem
that requires sophisticated coordination inside your brain.
That's because to create these new, weird images,
your brain takes familiar pieces and assembles them in new ways,
like a collage made from fragments of photos.
The brain has to juggle a sea of thousands of electrical signals
getting them all to their destination at precisely the right time.
When you look at an object,
thousands of neurons in your posterior cortex fire.
These neurons encode various characteristics of the object:
spiky, fruit, brown, green, and yellow.
This synchronous firing strengthens the connections between that set of neurons,
linking them together into what's known as a neuronal ensemble,
in this case the one for pineapple.
In neuroscience, this is called the Hebbian principle,
neurons that fire together wire together.
If you try to imagine a pineapple later,
the whole ensemble will light up, assembling a complete mental image.
Dolphins are encoded by a different neuronal ensemble.
In fact, every object that you've seen
is encoded by a neuronal ensemble associated with it,
the neurons wired together by that synchronized firing.
But this principle doesn't explain the infinite number of objects
that we can conjure up in our imaginations without ever seeing them.
The neuronal ensemble for a dolphin balancing a pineapple doesn't exist.
So how come you can imagine it anyway?
One hypothesis, called the Mental Synthesis Theory,
says that, again, timing is key.
If the neuronal ensembles for the dolphin and pineapple
are activated at the same time,
we can perceive the two separate objects as a single image.
But something in your brain has to coordinate that firing.
One plausible candidate is the prefrontal cortex,
which is involved in all complex cognitive functions.
Prefrontal cortex neurons are connected to the posterior cortex
by long, spindly cell extensions called neural fibers.
The mental synthesis theory proposes that like a puppeteer pulling the strings,
the prefrontal cortex neurons send electrical signals
down these neural fibers
to multiple ensembles in the posterior cortex.
This activates them in unison.
If the neuronal ensembles are turned on at the same time,
you experience the composite image just as if you'd actually seen it.
This conscious purposeful synchronization
of different neuronal ensembles by the prefrontal cortex
is called mental synthesis.
In order for mental sythesis to work,
signals would have to arrive at both neuronal ensembles at the same time.
The problem is that some neurons
are much farther away from the prefrontal cortex than others.
If the signals travel down both fibers at the same rate,
they'd arrive out of sync.
You can't change the length of the connections,
but your brain, especially as it develops in childhood,
does have a way to change the conduction velocity.
Neural fibers are wrapped in a fatty substance called myelin.
Myelin is an insulator
and speeds up the electrical signals zipping down the nerve fiber.
Some neural fibers have as many as 100 layers of myelin.
Others only have a few.
And fibers with thicker layers of myelin
can conduct signals 100 times faster or more
than those with thinner ones.
Some scientists now think that this difference in myelination
could be the key to uniform conduction time in the brain,
and consequently, to our mental synthesis ability.
A lot of this myelination happens in childhood,
so from an early age,
our vibrant imaginations may have a lot to do with building up brains
whose carefully myelinated connections
can craft creative symphonies throughout our lives.
提示:點選文章或是影片下面的字幕單字,可以直接快速翻譯喔!

載入中…

【TED-Ed】神經科學的想像力-TED-ed (The neuroscience of imagination - Andrey Vyshedskiy)

1249 分類 收藏
小爸 發佈於 2017 年 7 月 12 日
看更多推薦影片

影片討論

載入中…
  1. 1. 單字查詢

    在字幕上選取單字即可即時查詢單字喔!

  2. 2. 單句重複播放

    可重複聽取一句單句,加強聽力!

  3. 3. 使用快速鍵

    使用影片快速鍵,讓學習更有效率!

  4. 4. 關閉語言字幕

    進階版練習可關閉字幕純聽英文哦!

  5. 5. 內嵌播放器

    可以將英文字幕學習播放器內嵌到部落格等地方喔

  6. 6. 展開播放器

    可隱藏右方全文及字典欄位,觀看影片更舒適!

  1. 英文聽力測驗

    挑戰字幕英文聽力測驗!

  1. 點擊展開筆記本讓你看的更舒服

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔