Why does that lack of sleep make us so emotionally irrational and hyper-reactive?

為什麼睡眠不足會讓我們情緒如此反常，而且反應過度？

Well, several years ago, we conducted a brain imaging study.

我們在幾年前做了一個腦造影的研究。

And we took a group of healthy adults.

我們找來一群健康的成年人，

And we either gave them a full night of sleep or we sleep-deprived them.

其中一組人可以一夜好眠，另一組人則會徹夜難眠。

And then the next day, we placed them inside an MRI scanner, and we looked at how their emotional brain was reacting.

隔天，我們讓他們做核磁共振，再看他們的情緒腦怎麼反應。

And we focused on one structure in particular, it's called the amygdala.

我們特別專注在其中一個構造：杏仁核。

And the amygdala is one of the centerpiece regions for the generation of strong emotional reactions, including negative emotional reactions.

杏仁核是產生強烈情緒反應的關鍵部位，其中也包含了負面的情緒反應。

Now when we looked at those people who had a full night of sleep, what we saw was a nice, appropriate, moderate degree of reactivity from the amygdala.

我們發現睡飽的那組人， 他們的杏仁核有良好、 適當且適度的反應。

It wasn't as though there was no response at all, but it was an appropriate response.

它不是完全沒有反應， 但那是適當的反應。

Yet in those people who were sleep-deprived, that deep emotional brain center was in fact, hyperactive.

至於那組沒睡飽的人，他們的深層情緒腦中心會反應過度。

Indeed, the amygdala was almost 60 percent more responsive under conditions of a lack of sleep.

事實上，沒睡飽的時候，杏仁核的反應會增加近六成之多。

But why was that the case?

但為什麼會這樣？

And what we went on to discover, is that there's another brain region that's involved.

我們後來發現， 腦中還有另一個部位也受影響。

This brain region is called the prefrontal cortex, and it sits directly above your eyes.

這個部位稱為前額葉皮質，就位在你眼睛的正上方。

And you can think of the prefrontal cortex almost like the CEO of your brain.

你可以把前額葉皮質想像成是你大腦的執行長。

It's very good at making high-level, executive, top-down control decisions and reactions.

它很擅於做高階、決策、統籌控制決定和反應。

In fact, it's one of the most evolved regions of our brain.

其實前額葉皮質是我們大腦中進化最多的區域。

And one of the parts of the brain that it controls is this deep emotional center, the amygdala.

它在腦內控制的部位之一就是這個深層情緒中心，杏仁核。

Now in those people who had a full night of sleep, there was a nice, strong communication and connection between the prefrontal cortex, regulating that deep emotional brain center.

那些一夜好眠的人，他們的前額葉皮質之間有良好的溝通和連繫，調節那個深層情緒大腦中心。

But in those people who were sleep-deprived, that communication, that connection between the prefrontal cortex and that deep amygdala emotional brain center had essentially been severed.

但睡不飽的那群人， 前額葉皮質和深層情緒大腦中心杏仁核之間的溝通和連結，基本上被切斷了。

And as a consequence, the amygdala was responding far more reactively due to a lack of sleep.

結果是杏仁核的反應過度， 而這是睡眠不足造成的。

It's almost as though without sleep we become all emotional accelerator pedal, and too little regulatory control brake.

就好像沒有睡眠變成只剩情緒加速器， 而調節用的控制煞車則變少了。

And that seems to be the reason that we become so unbuckled in terms of our emotional integrity when we haven't been sleeping well.

這似乎就是我們在睡不好的時候情緒會如此失控的原因。

So that's the bad that can happen if I take sleep away from you.

如果我不讓你睡， 就會造成這種負面效果。因為我們晚上睡覺的時候，

But it turns out that there's something good that happens when you get your sleep back.

但其實只要你能夠補眠就會有正面效果。

And sleep, particularly rapid eye movement sleep, actually offers a form of emotional first aid.

睡眠，特別是快速動眼期的睡眠，其實是提供情緒急救的一種方式。

Because it's during sleep at night that we take these difficult emotional experiences that we've been having during the day,

帶著白天這些難受的情緒經驗上床，

and that sleep acts almost like a nocturnal soothing balm, taking the sharp edges off those difficult experiences.

睡眠扮演的角色就像夜間舒緩膏， 撫平那些難受經驗的刺。

And so perhaps it's not time that heals all wounds, it's time during sleep that provides that form of emotional convalescence.

因此也許並非時間撫平所有的傷痛，而是睡眠提供了這樣的情緒休養期。

So that when we come back the next day, we're able to cope with those emotional memories.

這樣我們隔天回來，就能處理那些情緒記憶了。