[MUSIC]

For many of us, the worst moment of every day goes something like this…

對很多人來說，一天之中最糟糕的時刻就像這樣......

[ALARM CLOCK NOISE]

[鬧鐘響... 響.... 還在響....]

That noise marks our daily return from the

日復一日，這個聲音提醒了我們該從

mysterious world that we call sleep. We spend a third of our lives asleep, yet, other than

被稱之為「睡眠」的神祕不可思議世界回來了。人們花了三分之一的生命在睡覺。然而，除了

the odd snapshot of a dream here and there, most of us have no idea what happens after

一些片段、零散的夢境內容之外，絕大多數的人對於閉上眼睛後所發生的事

we close our eyes.

一無所知。

Luckily we’re in good company, because there’s also a lot scientists don’t know about sleep, too.

幸運的是，我們跟其他人沒什麼不同，因為也有很多科學家對睡眠完全不了解。

For a long time, it was just something that happened, everyone assumed that our brains

一直以來，睡眠都被當成"就是這樣"的事，大家認為大腦

were hitting the reset button and just turning off for a while. But in the past few decades

會按下重新開機鍵然後暫時休息一陣子。但在最近數十年內，

it’s become clear that sleep might be the single most important behavior that humans

睡眠已經成為人類和其他動物生命中最重要的單一事項，

and other animals experience.

沒有之一。

It might seem like we don’t do much while we're sleep, but neuroscience tells a different

雖然我們在睡覺時看起來什麼都沒在做，但神經科學告訴我們事情並不是那麼簡單的

story. Human sleep patterns are controlled by two competing networks of chemical and electrical signals in the brain.

人類的睡眠模式被腦中兩種互相拮抗的的電子化學信號所控制。

During our waking hours, neurotransmitters released deep within our brain keep our cerebral

當我們醒著的時候，腦內深處分泌的神經傳導素會幫助我們刺激大腦的皮質

cortex alert and primed for consciousness. But throughout the day, as our neurons break

並幫助我們保持清醒，但一整天下來，身體中的神經元在分解三磷酸腺苷

down ATP for energy, the byproduct adenosine builds up and activates sleep control neurons

以產生能量的同時，隨之產生的腺苷刺激並促進了腦下視丘附近

near the hypothalamus.

負責控制睡眠的神經元。

A special region in the center of our brain acts as our master biological clock.

在我們的大腦中有一個精準的、像是生物時鐘一樣的特別區域，

Light sensitive cells in our retinas feed signals deep into that brain region, training neurons

視網膜上的光敏細胞會將信號送至這個區域，讓神經元

to sync up with Earth’s 24 hour cycle of day and night. These circadian rhythms are

能和地球上24小時的日夜循環同步。這種全天式的循環節奏正是

the control switch that tells us when to feel sleepy or awake.

告訴我們何時該起床或睡覺的控制開關。

As the world goes dark, this master switch tells our pineal gland to increase levels

當天黑的時候，這個總開關會刺激松果體提高血液中

of the hormone melatonin in the bloodstream, sort of like a chemical lullaby. Feelings

褪黑激素的濃度，就像一種化學性的搖籃曲一樣。

of fatigue set in, body temperature lowers slightly, that heat loss is actually why many

開始有疲勞的感覺、體溫稍微降低。實際上失溫正是當我們

of us like to fall asleep with our feet sticking out of the covers, true story! Together all

把腳伸出棉被外時會感到想睡的原因，真的沒騙你！

this neurochemistry sends one clear message to our bodies: when it’s dark, it’s time

所有的神經化學反應都送出同一個明確的訊息：當天黑的時候，

to go to bed.

就是該上床睡覺的時候了。

Unfortunately, in modern times, darkness is increasingly rare. In the United States, 99

不幸地是，在現代社會中，"黑暗"的時刻越來越少了。在美國，有99%的人

percent of people live in areas that meet standards for light pollution, and we’ve

生活在達到光害標準的地區之內，

got one person to thank for that: Thomas Alva Edison.

這都多虧了一個人：愛迪生。

Edison thought sleep was lazy, unhealthy, or inefficient, even though he took several

愛迪生認為睡覺是懶惰的行為，既不健康又沒效率 (雖然他一天打盹恍神好多次)

naps a day. But despite that hypocrisy his work more/sleep less view changed our world

但是，撇開他是否真的睡得很少這件事，他的「多工作、少睡覺」觀點確實從此改變了世界。

forever. Illuminating the night became a sign of economic progress, and humankind was no

被點亮的夜空是經濟進步的象徵，而人類也不再遵從自然的時鐘規律，

longer at the mercy of nature’s clock. Or so we thought.

至少我們是這麼認為的。

Artificial light can have serious effects on our sleep cycle. When we’re exposed to

不自然的光明嚴重影響了我們的睡眠循環，當我們在晚上卻仍

bright light at night, our brain doesn’t know better than to think the sun is shining.

暴露在燈光之下時，我們的大腦沒那麼聰明，它會以為太陽仍高掛空中。

This can be very confusing, preventing the release of melatonin and the onset of sleep.

這種錯誤的認知會混淆我們的大腦，抑制褪黑激素分泌和睡眠循環的啟動。

Depression, heart disease, diabetes, and cancer have all been linked to chronic overexposure

心情不好、心臟病、糖尿病和癌症都和長期慢性過度暴露

to artificial light.

在非自然光照下有關。

Until just a couple hundred years ago, it was common for people to fall asleep right

在近兩百年以前，日落而息對人類來說還是很自然的事情，

after the sun went down, snooze for a while, wake up around midnight, where they would

先小睡一下，在半夜時起床，

read or study or do other stuff, then go back to sleep until morning.

看個書或做點什麼其他事情，然後再回去繼續睡到早上。

Modern experiments have suggested that if people are kept away from artificial light,

近代的實驗提出假說，如果人類不再受人造光源的干擾，

their bodies will return to this pattern of first and second sleep, yet most of us insist

身體將會自然回到這樣兩段式睡眠的模式。然而，大多數人

on sleeping the whole night through. What’s worse, our circadian rhythms are so tuned

堅決認為要睡整個晚上。而更糟的是，我們的生理循環和日夜交替的關聯性

to day and night that if we stay up past our usual bedtime, we don’t wake up later, we

是如此的分秒不差，如果熬夜，我們並不會因此而晚起，

just tend to sleep less.

而是傾向於直接少睡了一點。

As a result, we’re massively sleep-deprived. Most adults average just six and a half hours

結論就是，我們嚴重地睡眠不足。絕大多數的成人平均一天只睡6.5小時，

a night. Teenagers average just five hours on school nights, which is half of what they

而青少年在周間的平均睡眠時間更只有5個小時，只有身體所需的一半。

need. To fight this chronic exhaustion, we turn to stimulants like caffeine to help our

為了應付這樣慢性的過勞，我們轉向於利用咖啡因來使我們的

brains ignore that buildup of adenosine, and then to fight the stimulants, many people

大腦忽視腺苷濃度的上升。而為了拮抗咖啡因等興奮劑，許多人

rely on alcohol, which just sedates us, it doesn’t even help with real, restful sleep.

開始依賴酒精。但酒精只能麻醉我們，對於真正的、充分的睡眠一點幫助都沒有。

This vicious cycle is worth literally billions of dollars a year. It’s kinda messed up.

這種惡性循環一年要付出數十億美元的代價，這真的太糟糕了！

I still love you though, coffee.

雖然我這樣講，可是咖啡，我還是愛你的唷

So what is sleep for? In short, we’re not really sure, but we know it’s essential

所以到底為什麼要睡覺，其實我們並不是很確定，不過我們知道睡覺對活下去而言

to life. Animals deprived of sleep for a long enough time will have seizures, and can literally

是很重要的。長期被剝奪睡眠的動物會出現突發性癲癇，而且真的

die from exhaustion, plus a whopping 15% of our genes are linked to circadian rhythms.

會因為過勞而死，再加上我們身體裡又有高達15%的基因和日夜循環的節奏相關。(所以睡眠真的很重要！)

Still, there’s no consensus on exactly why our bodies need sleep.

目前對於為何我們的身體需要睡眠確切原因仍尚未達成共識。

We’re definitely less active at night, but considering we only burn about 100 fewer calories

確實，我們的身體在晚上不那麼活躍，但考量到睡眠時其實只比清醒時少消耗100卡的能量，

while sleeping, it’s not a very good energy-saving strategy overall. We definitely do a lot of

睡眠並不是一個好的「節能」方式。在睡夢中，我們真的做了很多事，

cellular repair, protein synthesis, and general biological upkeep while we’re in dreamland,

像是細胞修復、蛋白質合成以及生理上的一般性保養等等，

but it’s not like we don’t do that stuff when we’re awake too.

但這並不表示當我們醒著的時候就不做這些了。

Another theory says that our bodies use time asleep to flush out all the neurogarbage,

另一派理論認為身體會利用睡覺的時間來排出所有的神經傳導廢物，

removing waste products that build up in our neurons and brain cells. And, decision-making

移除堆積在神經元和腦細胞中的垃圾。而且，我們腦中的決策中樞

regions of our brain like the prefrontal cortex, well they don’t get any downtime while we’re

「腦前額葉皮質」，在醒著的時候一刻都不得閒。

awake, like even if you’re totally relaxed and you think your mind is clear, your prefrontal

即使你完全放鬆、腦袋放空，你的腦前額葉皮質

cortex is still prefrontal cortexing. Just try and think about nothing. Go ahead. See?

也依然在運轉。來啊，試試看什麼都不想。你看，

You’re thinking about not thinking. Sleep seems to be the only time for this region

你正在想「我什麼都沒在想」。睡覺是這個腦區塊唯一可以

to power down and get a break.

關機並稍作休息的時間。

The greatest benefit of sleep may lie in processing information and consolidating memories from

睡覺最大的好處大概是可以整理整天接收的資訊和整合固化所有的記憶，

throughout the day, letting the brain do all the rewiring that is necessary for thinkin’

讓大腦有時間優化所有思考所需的連結。

better. Sleep deprived people do worse when learning new tasks and they're less able to

睡眠不足的人在學習新事物時表現較差而且處理新資訊時的

process new information, whereas a good night’s rest appears to make us more creative so we

能力也較差，反之好的睡眠讓我們更有創造力，

can come up with solutions to new problems that we haven’t seen before.

讓我們在面對從沒見過的問題時能夠想出解決辦法。

Perhaps the biggest mystery is how sleep evolved in the first place. Snoozin’ animals are

或許最大的謎團是睡眠這件事最初到底是如何發生的？因為睡著的小動物

easy targets for predators, so you’d think evolution would have come up with something

對掠食者來說是絕佳的目標，所以你可能會認為生物的自然演化會發產出什麼

better. But it hasn’t. There’s no way to get around the need for sleep.

比較好的應變方法。但事情並沒有這樣發展，沒有任何方法能逃避動物對睡眠的魔掌。

Some animals have come up with interesting ways to deal with the inconvenience of sleeping,

即使如此，仍有些動物演化出一些有趣的方法來面對睡著可能引發的麻煩，

though. Dolphins obviously can’t nod off without drowning, so they only sleep with

很明顯地，海豚無法一邊睡覺而維持自己不溺水，因此牠們

one half of their brain at a time, swimming along using the half of their body that’s

一次只睡半邊腦，然後用另一半清醒的腦來負責游泳。

still awake. Before baby dolphins learn that trick, they take adorable little dolphin naps

在小海豚還沒學會這招之前，海豚爸媽們會在小海豚打盹的時候

while their parents keep them afloat.

撐住牠們，讓牠們浮在水面上，維持可以呼吸的狀態。

Sleep or similar patterns of rest are seen so universally throughout the animal kingdom

休息睡覺或類似的模式在整個動物界中源遠流長而且屢見不鮮。

that they must have an ancient origin, and one clue comes from a tiny, ocean-dwelling worm.

從一種住在海裡的小小蟲蟲身上就可見一斑。

Every night, these worms swarm near the surface of the ocean to feed, and every day they sink

每天晚上，這些蟲蟲成群結隊地浮上海面覓食，而白天則

down deep to avoid light and predators. The worms have special daylight-sensing cells

躲到深海以避免光亮和掠食者。這種蟲蟲的背上有特殊的光感應細胞，

on their back, just like the ones in our eyes. When it’s dark, those cells trigger the

就像我們眼睛裡也有的那種。當天黑的時候，這些細胞會刺激

production of melatonin, just like in our brains. As the melatonin builds up, tiny hairs

褪黑激素的分泌，就像我們的腦袋被刺激那樣。隨著褪黑激素越來越多，它身上細小的毛髮

on their bodies stop beating and the worms begin to sink, just in time for the sun to

開始停止擺動，而蟲蟲也開始往下沉，剛好可以趕上太陽升起的時間。

come up. As the melatonin disappears throughout the day, the hairs begin beating again and

而當褪黑激素隨白天時間的過去減退時，這些毛髮又開始擺動，

they swim back up to the surface to do it all over again.

使得蟲蟲能重新游回海面，日復一日，年復一年。

Sleep might have evolved 700 million years ago, the last time we shared a common ancestor

睡覺這檔事已經演化了七億年之久，可以追溯到我們最早的共同祖先，

with that tiny worm. It's pretty important, so maybe we should all make a little more

那種蟲蟲。所以說，睡覺真的很重要，也許我們都應該留更多時間

time for it.

來睡個覺。

If you want to learn more about the science of sleep, one book that really helped me is

如果你想知道更多跟睡眠有關的科學知識，我推薦一本書：「Dreamland: Adventures in the Strange Science of Sleep」，

“Dreamland: Adventures in the Strange Science of Sleep” by David Randall. And also, be

是由David Randall所寫的。然後，別忘了

sure to check out this half-hour playlist from our friends at The Good Stuff that digs

去看看我們的好朋友在 The Good Stuff 上的半小時播放列表，裡面對於

even deeper into what are brains are doing while we’re asleep, plus Craig goes to a

我們睡著時腦袋在做的事有更深入的研究，還有Criaig跑去

sleep lab to find out how to get a better night’s rest. Sleeping on the job, Craig,

睡眠實驗室，試圖找出晚上能睡得更好的方法。你的工作就是睡覺，Craig，

real professional. Oh and over at BrainCraft, Vanessa has a video with some scientific tips

超專業的。噢還有，Venessa在 BrainCraft上有部關於如何用科學方法克服時差的影片

on how to beat jet lag. In fact, just make sure you’re subscribed

事實上，只要確認你有訂閱我們的頻道

to The Good Stuff and BrainCraft, they are awesome. Links to all that down in the description.

「好東西以及大腦解密」，超棒的。連結都在底下的說明

Stay curious.

保持好奇心喲！