How long should your naps be? - Sara C. Mednick

譯者: Claire Hsu 審譯者: Amanda Zhu

Your eyes get heavy and gradually... close...

眼皮變得沉重，而逐漸…… 闔上……

But wait!

但是等等！

It’s only lunchtime and you still have so much to do.

現在才午餐時間而已， 而你還有好多事情要做。

Would taking a nap help? Or would it derail your day?

小睡一下有幫助嗎？ 還是會拖垮你整天的行程呢？

Our sleep, both at night and in naps,

白天的打盹與夜晚的睡眠，

is made up of approximately 90 minute sleep cycles with four stages each.

由數個大約 90 分鐘的睡眠週期構成， 每週期分成四階段。

A nap can last anywhere from five minutes to three hours,

一次午覺可以持續五分鐘到三小時，

so it can include full sleep cycles or just a few stages.

可包含完整的睡眠週期， 或只有其中的幾個階段。

As you fall asleep, you enter Stage 1: the first two to five minutes of sleep.

在入眠時，你進入了第一階段： 最開頭二到五分鐘的睡眠。

Stage 2 comes next, for about 30 minutes.

接著是第二階段，大約有 30 分鐘。

In Stage 2, body temperature drops, muscles relax,

在第二階段當中， 體溫下降、肌肉放鬆，

and breathing and heart rate become more regular.

而呼吸與心跳頻率逐漸更有規律，

Your neurons start to fire in unison,

神經元會開始 同步「開火」，產生脈衝，

creating waves of activity that sweep across the cortex,

製造出一波一波的活動， 席捲整個大腦的皮質層，

punctuated by rapid bursts of neural activity called sleep spindles.

其間不時出現快速爆發的神經活動， 稱為「睡眠紡錘波」。

As you enter Stage 3, or slow wave sleep,

當你進入第三階段， 也是所謂的「慢波睡眠」，

the rolling waves increase as your neurons fire in coordination.

滾滾的腦波會隨著 神經元同時發生的脈衝而加大。

This phase lasts about 20 to 30 minutes and is where your deepest sleep occurs.

此階段會持續大約 20～30 分鐘， 最深層的睡眠在這階段發生。

Then, you enter REM sleep, which lasts about 10 to 20 minutes in a nap.

然後你進入了快速動眼期睡眠， 小睡時，這會持續大約 10～20 分鐘。

In REM, the brain becomes more active, more like your brain activity while awake.

快速動眼期當中，大腦變得更加活躍， 更像你清醒時的大腦活動。

The end of REM signals the completion of a sleep cycle.

快速動眼期的結束表示 一個睡眠週期的完成。

OK, but will a nap make you feel better?

好，但小睡一下能讓你感覺更好嗎？

Well, that depends on a few things—

這就取決於一些因素，

especially what stages of sleep the nap includes.

特別是你的小睡包含了哪些睡眠階段。

Take a 30 minute nap, which consists mainly of Stage 2 sleep.

30 分鐘的小睡， 主要包含的是第二階段的睡眠。

Stage 2 sleep is associated with long-term potentiation,

第二階段的睡眠被認為 與「長期增強效應」有關，

a process that's thought to strengthen the synapses between neurons,

一般認為這效應能夠強化 神經細胞之間的突觸，

which is essential for learning.

是學習的關鍵。

A 20 to 30 minute nap stops short of Stage 3′s deep sleep,

小睡 20～30 分鐘， 在第三階段的深度睡眠前就止步 ，

making it relatively easy to wake up from.

這時會相對地容易醒來。

A 30 to 60 minute nap, meanwhile, has the benefits of Stage 2 sleep

小睡 30～60 分鐘，同時可以享受 第二階段的睡眠帶來的好處，

and also takes you into the deeper sleep of Stage 3.

也帶你進入第三階段更深層的睡眠。

During Stage 3, multiple brain areas work together to transfer information

在第三階段中， 大腦中的多個區域會一起合作

將資訊從短期記憶的儲存區 轉移到長期記憶的儲存區，

from short-term memory storage to long-term storage,

stabilizing and strengthening long-term memory

由結合睡眠紡錘波與緩慢的腦波

by coupling sleep spindles with slow waves.

穩定強化長期記憶。

Stage 3 is the most difficult stage to wake up from.

第三階段是最難從中醒來的。

So while a 30 to 60 minute nap can have cognitive benefits,

所以雖然小睡 30 到 60 分鐘 對認知能力有好處，

those benefits often don’t kick in until about 15 minutes after waking up.

但是這些好處通常要等 醒來 15 分鐘過後才會發揮作用。

60 to 90 minute naps enter the REM stage.

睡 60～90 分鐘，會進入快速動眼期。

While in REM, the prefrontal cortex,

在快速動眼期當中，

負責衝動抑制與認知控制的 前額葉皮質區，

which is largely responsible for inhibition and cognitive control,

becomes much less active.

會變得很不活躍。

Meanwhile, the amygdala and cingulate cortex,

同時，和情緒與動機相關的 杏仁體與扣帶迴皮質區

regions associated with emotion and motivation, are highly active.

會變得非常活躍。

Researchers have posited that the combination of these things

研究人員們已經推斷， 這些因素綜合起來

leads to bizarre dreams during REM sleep:

會導致大腦在快速動眼期間 產生古怪的夢境：

the decrease in inhibition and cognitive control might lead to wild associations—

衝動抑制與認知控制減少， 可能催生出天馬行空的聯想；

and, thanks to the amygdala and cingulate cortex activity,

而由於杏仁體與扣帶迴皮質區的活動，

those associations can be between emotionally charged topics.

這些聯想所觸及的主題 可能會更加情緒化。

Some researchers think this stage might help us make innovative connections

有些研究人員認為這階段 可能會幫助我們在醒來之前

between ideas upon waking.

在不同想法之間產生創新的連結。

Because the brain activity during REM is closer to waking,

因為快速動眼期的腦部活動 和清醒時的活動較相似，

it may be easier to wake up from REM than Stage 3,

人在快速動眼期當中 比第三階段更容易醒來，

even though the nap is longer.

儘管睡得也比較久。

The time of day also matters.

在什麼時間小睡也很重要。

Our need for deep Stage 3 sleep progressively increases

一天當中，我們對第三階段 深度睡眠的需求

throughout the day.

會隨著時間過去逐漸增加。

So if you nap later,

所以如果你越晚打盹，

you may rob yourself of the sleep pressure needed to go to sleep at night.

你可能會失去讓你 晚上好好睡覺的睡眠壓力。

This doesn't happen for REM sleep.

但快速動眼期睡眠不會如此。

Longer periods of REM occur during morning hours,

較長的快速動眼期會在上午發生，

so morning naps are dominated by REM,

所以早上的補眠以快速動眼期為主，

midday naps have about equal parts of REM and deep sleep,

午睡時，快速動眼期 與深度睡眠比例大致相等，

and evening naps contain more deep sleep.

晚間的睡眠則包含較多深度睡眠。

On top of all this, it seems that we’re just about evenly split

除了這些之外，

人們睡午覺或不睡午覺的比例 大約剛好是一半一半。

between nappers and non-nappers.

Nappers consistently show cognitive benefits from napping,

會睡午覺的人始終表現出 午覺對認知能力上的好處，

but non-nappers may not.

但是不睡午覺的人可能就沒有。

Researchers think this could be because nappers

研究人員認為這可能是因為 會睡午覺的人

are able to stay in a lighter sleep and move through sleep stages more easily.

容易維持較淺眠的狀態， 較容易通過不同睡眠階段。

Meanwhile, non-nappers may experience more deep sleep while napping,

同時，不睡午覺的人在小睡期間 會經歷較長的深度睡眠，

making them groggy afterward.

醒來之後容易頭腦昏沉。

So will a nap help?

所以，小睡一下有幫助嗎？

Well, there’s only one way to find out...

這個嘛，只有睡一覺才能知道了……