How spontaneous brain activity keeps you alive - Nathan S. Jacobs

自發性腦部活動如何讓你活著—南森·雅各 (Nathan S. Jacobs)

譯者: Regina Chu 審譯者: Marssi Draw

You probably don't need to be told how important your brain is.

你大概不需要別人 告訴你大腦有多重要

After all, every single thing you experience,

畢竟，你經歷的每件事

your thoughts and your actions,

你的思想、你的行動

your perceptions and your memories

你的知覺、你的記憶

are processed here in your body's control center.

都在你體內的這個控制中心處理

But if this already seems like a lot for a single organ to handle,

如果這對單一器官而言 工作似乎太多了

it's actually only a small part of what the brain does.

其實這還只是腦部工作的一小部分

大部分的腦部活動 都在你無意識的狀態下進行

Most of its activities are ones you'd never be aware of,

unless they suddenly stopped.

除非這些活動突然停止

The brain is made up of billions of neurons,

腦由無數的神經元

and trillions of connections.

及數不清的連接點組成

Neurons can be activated by specific stimuli or thoughts,

神經元可由特定的刺激或思想活化

but they are also often spontaneously active.

但也常常有自發性活動

Some fire cyclically in a set pattern.

有些會以固定模式產生週期性發射

Others fire rapidly in short bursts before switching off,

有些則在關閉前產生短暫猝發

or remain quiet for long periods

還有一些是保持安靜很長一段時間

until thousands of inputs from other neurons line up in just the right way.

直到從其它神經元輸入的無數訊號 以正確的方式排列才發射

On a large scale,

大規模看

this results in elaborate rhythms of internally generated brain activity,

這會使內部產生的 腦部活動產生複雜節律

humming quietly in the background

在背景輕輕作響

whether we're awake, asleep,

無論我們是醒著、睡著

or trying not to think about anything at all.

還是試圖放空都這樣響著

And these spontaneously occurring brain functions

這些自發性的腦部功能

form the foundation upon which all other brain functions rely.

成為其它腦部活動的依賴基礎

The most crucial of these automatically occurring activities

這些自發活動中最重要的

are the ones that keep us alive.

是使我們活著的活動

For example, while you've been paying attention to this video

舉例來說 就在你專心看這段影片的同時

spontaneous activity in your brain has been maintaining your breathing

你腦部的自發活動 就在讓你保持呼吸

at 12 to 16 breaths a minute, making sure that you don't suffocate.

每分鐘 12 到 16 次 確保你沒有窒息

Without any conscious effort,

無需任何意識

signals from parts of your brainstem are sent through the spinal cord

從腦幹傳來的訊號會經過脊髓

to the muscles that inflate your lungs,

送到肌肉，使你的肺充氣

making them expand and contract, whether or not you're paying attention.

無論你有沒有注意 都會使肺部擴張收縮

The neuronal circuits underlying such rhythmic spontaneous activity

潛藏在此種節律自發 活動底下的神經元電路

are called central pattern generators,

稱為中樞模式發生器

and control many simple repetitive behaviors,

並控制許多簡單、重複的行為

like breathing,

例如呼吸

walking,

走路

and swallowing.

及吞嚥

Ongoing neural activity also underlies our sensory perception.

不斷進行的神經活動 也藏在我們的知覺下

It may seem

雖然看起來像是

that the neurons in your retina that translate light into neural signals

視網膜的神經元 將光轉變成神經訊號

would remain quiet in the dark,

而此訊號在黑暗下會保持安靜

but in fact,

但事實是

the retinal ganglion cells that communicate with the brain

與大腦溝通的視網膜神經節細胞

are always active.

永遠處在活化狀態下

And the signals they send are increases and decreases in the rate of activity,

它們傳出的訊號隨活動增加或減少

rather than separate bursts.

而非分開的猝發

So at every level, our nervous system is teeming with spontaneous activity

所以我們的神經系統在每個層面 都充滿了自發性的活動

that helps it interpret and respond to any signals it might receive.

幫助系統闡釋接受的訊號並做出反應

And our brain's autopilot isn't just limited to our basic biological functions.

我們腦部的自動駕駛 可不只限於基礎生物功能

Have you ever been on the way home,

你可曾在回家路上

started thinking about what's for dinner,

想晚餐要吃什麼

and then realized you don't remember walking for the past five minutes?

然後突然意識到 你不記得這五分鐘在走路？

While we don't understand all the details,

雖然我們並不了解所有的細節

we do know that the ongoing activity in multiple parts of your brain

我們的確知道在你腦中 數個部位的持續活動

is somehow able to coordinate what is actually a complex task

以某種方式協調複雜的

involving both cognitive and motor functions,

認知及運動功能任務

guiding you down the right path and moving your legs

即使你在想晚餐要吃什麼

while you're getting dinner figured out.

還是能帶你走對的路、移動腳

But perhaps the most interesting thing about spontaneous brain function

但是自發性腦部功能最有趣的部分

is its involvement in one of the most mysterious

大概是其與身體中最神秘

and poorly understood phenomena of our bodies: sleep.

最不為人知的現象的關聯：睡眠

You may shut down and become inactive at night,

你可能晚上睡死了動也不動

but your brain doesn't.

但是你的腦部可不是這樣

While you sleep,

你睡覺的時候

ongoing spontaneous activity gradually becomes more and more synchronized,

持續進行的自發性活動 逐漸變得愈來愈同步

eventually developing into large, rhythmic neural oscillations

最終變成大型節律神經震盪

that envelop your brain.

籠罩你的腦部

This transition to the more organized rhythms of sleep

這種轉變成更有規律的睡眠節律過程

starts with small clusters of neurons tucked in the hypothalamus.

始於擠在海馬區裡的一小叢神經元

Despite their small number,

儘管數量很少

these neurons have a huge effect

這些神經元對關閉 平常讓你清醒和警覺的腦幹區域

in turning off brainstem regions that normally keep you awake and alert,

有極大的效力

letting other parts, like the cortex and thalamus,

使其它部位如皮質及視丘

slowly slip into their own default rhythms.

慢慢轉成原本預設的節律

The deeper we fall into sleep,

我們睡得愈熟

the slower and more synchronized this rhythm becomes,

這種節律就愈慢且愈同步

with the deepest stages dominated by large amplitude, low frequency delta waves.

最深層階段的睡眠則由 大振幅低頻率的德爾塔波控制

But surprisingly, in the middle of this slow wave sleep,

但令人驚訝的是 在這種慢波睡眠期間

the brain's synchronized spontaneous activity

腦部的同步自發性活動

repeatedly transitions into the sort of varied bursts

又轉變成在我們完全清醒時

that occur when we're wide awake.

才會發生的各式猝發

This is the sleep stage known as REM sleep,

這個階段稱為快速動眼期

where our eyes move rapidly back and forth as we dream.

此時我們的眼球會快速 來回移動，還會作夢

Neuroscientists are still trying to answer many fundamental questions about sleep,

神經科學家仍然試著找出 睡眠基礎問題的答案

such as its role in rejuvenating cognitive capacity,

譬如它如何恢復認知能力

cellular homeostasis,

細胞穩態

and strengthening memory.

及強化記憶

And more broadly, they are exploring

他們還更廣泛地探索

how it is that brain can accomplish such important and complex tasks,

腦部如何能完成如此 重要又複雜的工作

such as driving, or even breathing, without our awareness.

如無意識的開車甚至呼吸

But for now, until we are better able

但是現在，在我們能更進一步

to understand the inner workings of their spontaneous functioning,

瞭解腦部自發性功能 內部如何運作前

we need to give our brains credit for being much smarter

我們必須承認我們的腦部

than we ourselves are.

比我們自己要聰明多了