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

翻译人员: Yanyan Hong 校对人员: Jiasi Hao

你的眼皮变得沉重， 慢慢地……合上……

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

But wait!

但等等！

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

才刚到午餐时间， 而你还有这么多事情要做。

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

打个盹会有帮助吗？ 还是说这会妨碍你的一天？

Our sleep, both at night and in naps,

我们的睡眠， 无论是夜间还是午睡

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

都是由大约 90 分钟的睡眠周期组成， 每个周期分四个阶段。

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

小睡可以持续 5 分钟到 3 小时，

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

所以它可以包括完整的睡眠周期 或者只是几个阶段。

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

当你入睡时，你进入了第一阶段： 睡眠开始的 2-5 分钟。

Stage 2 comes next, for about 30 minutes.

接下来是第二阶段，大约 30 分钟。

In Stage 2, body temperature drops, muscles relax,

在第二阶段，体温下降、肌肉放松，

and breathing and heart rate become more regular.

呼吸和心率变得更加规律。

Your neurons start to fire in unison,

你的神经元开始齐射，

creating waves of activity that sweep across the cortex,

产生扫过大脑皮层的活动波，

punctuated by rapid bursts of neural activity called sleep spindles.

被名为 “睡眠纺锤波” 的 高频爆发神经活动打断并结合。

As you enter Stage 3, or slow wave sleep,

当你进入第三阶段， 或慢波睡眠时，

the rolling waves increase as your neurons fire in coordination.

随着你的神经元 协作发射，滚动波增加。

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

这个阶段持续约 20 至 30 分钟， 也是你进入深度睡眠之际。

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

然后，你进入快速眼动睡眠， 在小睡中大约持续 10 至 20 分钟。

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

在快速眼动睡眠时，大脑变得更加活跃， 更像大脑清醒时的活动。

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

快速眼动睡眠信号结束 标志着一个睡眠周期的完成。

OK, but will a nap make you feel better?

好吧，但打个盹会让你感觉更好吗？

Well, that depends on a few things—

那取决于一些要素——

especially what stages of sleep the nap includes.

尤其是小睡包括哪些睡眠阶段。

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

比方说 30 分钟小睡， 主要包括第二阶段的睡眠。

Stage 2 sleep is associated with long-term potentiation,

第二阶段的睡眠 与长时程增强作用有关，

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

长时程增强作用被认为 能加强神经元之间的突触，

which is essential for learning.

这对学习至关重要。

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

20 到 30 分钟的小睡 在第三阶段的深层睡眠前就会停止，

making it relatively easy to wake up from.

因此从睡梦中醒来相对容易。

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

30 到 60 分钟的小睡，同样， 会带来第二阶段睡眠的好处，

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

也会让你进入第三阶段的深度睡眠。

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

在第三阶段， 多个大脑区域协同工作

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

将信息从短期记忆储存 转移到长期记忆，

stabilizing and strengthening long-term memory

通过将睡眠纺锤波与慢波耦合，

by coupling sleep spindles with slow waves.

稳定并加强长期记忆。

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

第三阶段是最难醒来的阶段，

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

因此，虽然 30 到 60 分钟的 小睡有利于认知能力，

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

但这些好处往往要到醒后 15 分钟左右才会显现出来。

60 to 90 minute naps enter the REM stage.

60 至 90 分钟的小睡 会进入快速眼动阶段，

While in REM, the prefrontal cortex,

而在快速眼动阶段，

which is largely responsible for inhibition and cognitive control,

主要负责抑制和认知控制的前额叶皮层

becomes much less active.

变得不那么活跃。

Meanwhile, the amygdala and cingulate cortex,

同时，杏仁核和扣带皮层，

regions associated with emotion and motivation, are highly active.

与情绪和动机相关的区域 反而高度活跃。

Researchers have posited that the combination of these things

研究人员认为，这些现象的结合

leads to bizarre dreams during REM sleep:

会在快速眼动睡眠期间 催生出怪异的梦境：

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

抑制和认知控制的减少 可能会导致疯狂的联想——

and, thanks to the amygdala and cingulate cortex activity,

而且，由于杏仁核 和扣带回皮层的活动，

those associations can be between emotionally charged topics.

这些联想可能常 处在情绪化的话题中。

Some researchers think this stage might help us make innovative connections

一些研究人员认为这个阶段 可能有助于我们在醒来后

between ideas upon waking.

在想法间产生创新的联系。

Because the brain activity during REM is closer to waking,

因为，大脑活动在快速动眼 睡眠期间与清醒时相似，

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

尽管小睡的时间更长，

even though the nap is longer.

但可能比第三阶段更容易醒来。

The time of day also matters.

一天中小睡的时间也很重要。

Our need for deep Stage 3 sleep progressively increases

我们对第三阶段深度睡眠的需求 在一天中

throughout the day.

随着时间推移逐渐增加，

So if you nap later,

因此，如果你晚点打盹，

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

你可能会让自己晚上睡不着。

This doesn't happen for REM sleep.

但对于快速动眼睡眠这不成问题，

Longer periods of REM occur during morning hours,

长时间的快速眼动发生在早晨，

so morning naps are dominated by REM,

所以早晨的小睡主要是快速眼动，

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

中午的小睡有相当部分的 快速眼动和深度睡眠，

and evening naps contain more deep sleep.

而晚上睡觉多数是深度睡眠。

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

总之，似乎喜欢小睡 和不喜欢小睡的人

between nappers and non-nappers.

平分秋色。

Nappers consistently show cognitive benefits from napping,

喜欢小睡的人总是表现出 小睡对认知的好处，

but non-nappers may not.

但不喜欢小睡的人则没有。

Researchers think this could be because nappers

研究人员认为这可能是 因为喜欢小睡的人

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

能够保持较轻的睡眠状态， 更容易转换于不同睡眠阶段。

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

同时，不喜欢小睡的人在打盹时 可能会经历更多的深度睡眠，

making them groggy afterward.

让他们醒来后昏昏沉沉。

So will a nap help?

那么小睡一下会有帮助吗？

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

只有一个办法可以知道……