研究称上班摸鱼是大脑在排毒

近日，发表在《当代生物学》（Current Biology）期刊上的一项研究表明，在一天中人越努力思考，大脑前额叶皮层中「谷氨酸」的含量积累得越多。而谷氨酸积累过多会破坏大脑功能，让人觉得疲惫不堪、难以集中精神。

想要消除这种「毒素」？那就停下来打个盹、摸摸鱼，休息一下吧！

无注释原文：

Why thinking hard makes you tired

From: EurekAlert!

11-AUG-2022

It’s no surprise that hard physical labor wears you out, but what about hard mental labor? Sitting around thinking hard for hours makes one feel worn out, too. Now, researchers have new evidence to explain why this is, and, based on their findings, the reason you feel mentally exhausted (as opposed to drowsy) from intense thinking isn’t all in your head.

Their studies, reported in Current Biology on August 11, show that when intense cognitive work is prolonged for several hours, it causes potentially toxic byproducts to build up in the part of the brain known as the prefrontal cortex. This in turn alters your control over decisions, so you shift toward low-cost actions requiring no effort or waiting as cognitive fatigue sets in, the researchers explain.  

“Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity,” says Mathias Pessiglione of Pitié-Salpêtrière University in Paris, France. “But our findings show that cognitive work results in a true functional alteration—accumulation of noxious substances—so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning.”

Pessiglione and colleagues including first author of the study Antonius Wiehler wanted to understand what mental fatigue really is. While machines can compute continuously, the brain can’t. They wanted to find out why. They suspected the reason had to do with the need to recycle potentially toxic substances that arise from neural activity.

To look for evidence of this, they used magnetic resonance spectroscopy (MRS) to monitor brain chemistry over the course of a workday. They looked at two groups of people: those who needed to think hard and those who had relatively easier cognitive tasks.

They saw signs of fatigue, including reduced pupil dilation, only in the group doing hard work. Those in that group also showed in their choices a shift toward options proposing rewards at short delay with little effort. Critically, they also had higher levels of glutamate in synapses of the brain’s prefrontal cortex. Together with earlier evidence, the authors say it supports the notion that glutamate accumulation makes further activation of the prefrontal cortex more costly, such that cognitive control is more difficult after a mentally tough workday.

So, is there some way around this limitation of our brain’s ability to think hard?

“I would employ good old recipes: rest and sleep! There is good evidence that glutamate is eliminated from synapses during sleep,” Pessiglione said.

There may be other practical implications. For example, the researchers say, monitoring of prefrontal metabolites could help to detect severe mental fatigue. Such an ability may help adjust work agendas to avoid burnout. He also advises people to avoid making important decisions when they’re tired.

In future studies, they hope to learn why the prefrontal cortex seems especially susceptible to glutamate accumulation and fatigue. They’re also curious to learn whether the same markers of fatigue in the brain may predict recovery from health conditions, such as depression or cancer.

- ◆ -

注：中文文本为机器翻译仅供参考，并非一一对应

含注释全文：

Why thinking hard makes you tired

From: EurekAlert!

11-AUG-2022

It’s no surprise that hard physical labor wears you out, but what about hard mental labor? Sitting around thinking hard for hours makes one feel worn out, too. Now, researchers have new evidence to explain why this is, and, based on their findings, the reason you feel mentally exhausted (as opposed to drowsy) from intense thinking isn’t all in your head.

重体力劳动会让你筋疲力尽，这并不奇怪，但是重脑力劳动呢？坐在那里努力思考几个小时也会让人感到筋疲力尽。现在，研究人员有了新的证据来解释为什么会这样。根据他们的发现，你因为紧张的思考而感到精神疲惫（而不是昏昏欲睡）的原因并不全在于大脑。

wear sb out

表示“使（某人）筋疲力尽”，英文解释为“to make someone extremely tired”举个🌰：

Walking around a museum all day really wears you out.

整天在博物馆里走来走去，真的让人筋疲力尽。

drowsy

drowsy /ˈdraʊ.zi/ 表示“睡意朦肬的，半梦半醒的，似睡非睡的”，英文解释为“being in a state between sleeping and being awake”举个🌰：

The room is so warm it's making me feel drowsy.

房间非常暖和，让我有些昏昏欲睡。

🎬电影《副作用》（Side Effects）中的台词提到：After a few minutes, you'll probably get drowsy and fall asleep. 再过几分钟你就会昏昏入睡的。

Their studies, reported in Current Biology on August 11, show that when intense cognitive work is prolonged for several hours, it causes potentially toxic byproducts to build up in the part of the brain known as the prefrontal cortex. This in turn alters your control over decisions, so you shift toward low-cost actions requiring no effort or waiting as cognitive fatigue sets in, the researchers explain.

他们的研究发表在8月11日的《当代生物学》（Current Biology）期刊上。研究表明，当高强度的认知工作持续数小时后，它会导致潜在的有毒副产品积聚在大脑中被称为前额叶皮层的区域。研究人员解释说，这反过来会改变你对决策的控制，所以当你开始感到认知疲劳时，你会转向不需要努力或等待的低成本行动。

cognitive

表示“认知的；感知的；认识的”，英文解释为“Cognitive means relating to the mental process involved in knowing, learning, and understanding things.”举个🌰：

As children grow older, their cognitive processes become sharper. 

随着孩子们长大，他们的认知过程也变得越来越敏锐了。

prolonged

表示“延续很久的，长期的”，英文解释为“continuing for a long time”举个🌰：

Prolonged use of the drug is known to have harmful side-effects.

据了解，长期服用此药会产生对人体有害的副作用。

toxic

toxic /ˈtɒksɪk/ 1）表示“有毒的；引起中毒的”，相当于poisonous，如：toxic waste/chemicals/effluent 有毒的废料/化学品/废水，牛津词典2018年度词汇就是：Toxic.

2）表示“令人极不愉快的；不可接受的”，英文解释为“very unpleasant or unacceptable”。

3）表示“恶毒的；造成阴影的”，英文解释为“causing you a lot of harm and unhappiness over a long period of time”如：a toxic relationship 带毒的友谊。

byproduct

表示“副产品”，英文解释为“something that is produced as a result of making something else, or something unexpected that happens as a result of something else”

prefrontal cortex

prefrontal cortex /ˌpriː.frʌn.təl ˈkɔː.teks/ 表示“前额皮质；前额叶皮层”，英文解释为“the front part of the brain, that is important in human behaviour such as planning, decision-making, and self-control”举个🌰：

Exercise counters age-related shrinking of the prefrontal cortex.

运动能抵消与年龄相关的前额皮质缩小。

fatigue

fatigue /fəˈtiːɡ/ 可以作动词，也可以作名词，表示“疲劳；劳累”，英文解释为“a feeling of being extremely tired, usually because of hard work or exercise”，如：physical and mental fatigue 身体和精神的疲劳。

set in

表示“（不好的事）到来，开始（而且可能会持续）”，英文解释为“When something unpleasant sets in, it begins and seems likely to continue in a serious way.”举个🌰：

This rain looks as if it has set in for the rest of the day.

看来今天雨不会停。

🎬电影《人类之子》（Children of Men）中的台词提到：As the sound of the playgrounds faded, the despair set in. 游乐场的声音逐渐淡去，接着是绝望。

“Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity,” says Mathias Pessiglione of Pitié-Salpêtrière University in Paris, France. “But our findings show that cognitive work results in a true functional alteration—accumulation of noxious substances—so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning.”

“有影响力的理论认为，疲劳是大脑制造的一种幻觉，目的是让我们停止正在做的任何事情，转向更令人满意的活动，”法国巴黎皮提耶-萨勒佩特里大学的马蒂亚斯·佩西格隆（Mathias Pessiglione）说。“但是我们的研究结果表明，认知工作会导致真正的功能性改变——有毒物质的积聚——所以疲劳确实是一个让我们停止工作的信号，但目的不同：保持大脑功能的完整性。”

illusion

表示“错误的观念；幻想；假象，错觉”，英文解释为“a false idea or belief, especially about sb or about a situation”举个🌰：

I have no illusions about her feelings for me.

我对她跟我的感情不抱什么幻想。

cook sth up

cook /kʊk/ 表示“编造，捏造”，英文解释为“to invent a story, plan, etc., usually dishonestly”举个🌰：

She cooked up some weird scheme that was going to earn her a fortune.

她想出了个能使自己发财的怪点子。

gratifying

gratifying /ˈɡræt.ɪ.faɪ.ɪŋ/ 表示“心满意足的”，英文解释为“pleasing and satisfying”举个🌰：

It must be very gratifying to see all your children grown up and happy.

看到孩子们都长大成人、生活幸福，你一定感到心满意足吧。

accumulation

accumulation /əˌkjuː.mjəˈleɪ.ʃən/ 表示“积累；积聚；积攒”，英文解释为“an amount of something that has been collected”举个🌰：

Despite this accumulation of evidence, the government persisted in doing nothing.

尽管种种迹象不断出现，政府仍然坚持不采取任何行动。

noxious

noxious /ˈnɒk.ʃəs/ 1）表示“（尤指气体或其他物质）有毒的，有害的”，英文解释为“Something, especially a gas or other substance, that is noxious is poisonous or very harmful.”举个🌰：

They died from inhaling noxious fumes.

他们吸入有毒烟雾致死。

2）表示“有害的；令人不愉快的；讨厌的”，英文解释为“harmful and unpleasant”如：a noxious smell/influence 难闻的气味/不良的影响。

preserve

表示“保护，维护；保留；保养”，英文解释为“to keep something as it is, especially in order to prevent it from decaying or being damaged or destroyed”如：to preserve the environment 保护环境。

integrity

1）表示“完整”，英文解释为“the quality of being whole and complete”举个🌰：

A modern extension on the old building would ruin its architectural integrity.

在古老建筑物上附加扩建的现代建筑会破坏建筑风格的完整统一。

2）表示“正直；诚实；职业操守”，英文解释为“the quality of being honest and having strong moral principles that you refuse to change”举个🌰：

No one doubted that the president was a man of the highest integrity.

没有人怀疑总裁是个光明磊落的人。

Pessiglione and colleagues including first author of the study Antonius Wiehler wanted to understand what mental fatigue really is. While machines can compute continuously, the brain can’t. They wanted to find out why. They suspected the reason had to do with the need to recycle potentially toxic substances that arise from neural activity.

佩西格隆和他的同事，包括这项研究的第一作者安东尼尔斯·维勒（Antonius Wiehler），想了解精神疲劳（mental fatigue）到底是什么。虽然机器可以持续计算，但大脑不能。他们想找出原因。他们怀疑这与神经活动产生的潜在有害物质需要回收有关。

arise

表示“发生；产生；出现”，英文解释为“to happen”举个🌰：

Should the opportunity arise, I'd love to go to Beijing.

要是有机会的话，我很想去北京。

To look for evidence of this, they used magnetic resonance spectroscopy (MRS) to monitor brain chemistry over the course of a workday. They looked at two groups of people: those who needed to think hard and those who had relatively easier cognitive tasks.

为了寻找这方面的证据，他们使用磁共振波谱（MRS）监测一个工作日内的脑化学变化。他们观察了两组人：需要努力思考的人和认知任务相对容易的人。

magnetic

magnetic /mæɡˈnet.ɪk/ 表示“磁的，有磁性的；磁化的”，英文解释为“with the power of a magnet”

resonance

resonance /ˈrezənəns/ 1）resonance /ˈrez.ən.əns/ 表示“共振（某物由于另一个物质的振动／摇动而发出声音）”，英文解释为“the production of a sound as a result of vibration (= shaking) of another object”如：magnetic resonance 磁共振。

2）表示“共鸣（一个作品或一曲音乐使你产生的感情、思想、回忆等，也可指作品或乐曲中使这种情况发生的特质）”，英文解释为“a feeling, thought, memory, etc. that a piece of writing or music makes you have, or the quality in a piece of writing, etc. that makes this happen”

spectroscope

spectroscopy /spekˈtrɒs.kə.pi/ 表示“光谱学”，英文解释为“the study of the way matter absorbs or sends out light and other radiation (= energy from light or heat that you cannot see) ”

monitor

表示“监视；检查；跟踪调查”，英文解释为“to watch and check sth over a period of time in order to see how it develops, so that you can make any necessary changes”举个🌰：

Each student's progress is closely monitored.

每一位同学的学习情况都受到密切的关注。

They saw signs of fatigue, including reduced pupil dilation, only in the group doing hard work. Those in that group also showed in their choices a shift toward options proposing rewards at short delay with little effort. Critically, they also had higher levels of glutamate in synapses of the brain’s prefrontal cortex. Together with earlier evidence, the authors say it supports the notion that glutamate accumulation makes further activation of the prefrontal cortex more costly, such that cognitive control is more difficult after a mentally tough workday.

他们发现了疲劳的迹象，包括瞳孔扩张减少，但这只发生在努力工作的那组人身上。该组人在决策中也表现出向在短时间就能轻而易举获得奖励的选项转变。关键的是，他们大脑前额叶皮层突触中的谷氨酸（glutamate）水平也较高。作者说，结合早期的证据，这支持了谷氨酸的积累会使前额叶皮层进一步激活的成本更高的观点，因此在精神紧张的一天之后，认知控制会更加困难。

pupil

pupil /ˈpjuː.pəl/ 表示“学生，（尤指）小学生”，此次熟词僻义，表示“瞳孔”，英文解释为“the circular black area in the centre of an eye, through which light enters”举个🌰：

Pupils contract in bright light, and dilate in darkness.

瞳孔在明亮的光线下会收缩，在黑暗中会扩大。

dilation

dilation /daɪˈleɪ.ʃən/ 表示“扩张”，英文解释为“the state of being larger or more open than usual”

synapse

synapse /ˈsaɪ.næps/ 表示“（神经元的）突触”，英文解释为“the point at which electrical signals move from one nerve cell to another”

So, is there some way around this limitation of our brain’s ability to think hard?

那么，有没有办法克服我们大脑努力思考能力的限制？

“I would employ good old recipes: rest and sleep! There is good evidence that glutamate is eliminated from synapses during sleep,” Pessiglione said.

佩西格隆说：“我会采用很好的老方法：休息和睡眠！有很好的证据表明，谷氨酸在睡眠过程中会从突触中消除。”

employ

熟词僻义，表示“使用，利用”，英文解释为“If you employ certain methods, materials, or expressions, you use them.”举个🌰：

The group will employ a mix of tactics to achieve its aim. 

该团体将运用混合策略来实现其目标。

recipe

除了表示“食谱”，还可以指“方法；秘诀；诀窍”，英文解释为“a method or an idea that seems likely to have a particular result”举个🌰：

What's her recipe for success?

她成功的秘诀是什么？

There may be other practical implications. For example, the researchers say, monitoring of prefrontal metabolites could help to detect severe mental fatigue. Such an ability may help adjust work agendas to avoid burnout. He also advises people to avoid making important decisions when they’re tired.

可能还有其他实际意义。例如，研究人员说，监测前额代谢物有助于发现严重的精神疲劳。这种能力可能有助于调整工作议程，以避免过度劳累。他还建议人们在疲劳时避免做出重要决定。

implication

1）表示“可能的影响（或作用、结果）”，英文解释为“a possible effect or result of an action or a decision”举个🌰：

The development of the site will have implications for the surrounding countryside.

这个地点的开发将会影响周围的乡村。

2）表示“含意；暗指，暗示”，英文解释为“an occasion when you seem to suggest something without saying it directly”举个🌰：

From what she said, the implication was that they were splitting up.

她的话中暗示他们将要分手。

metabolite

metabolite /məˈtæb.ə.laɪt/ 表示“代谢物”，英文解释为“any substance involved in metabolism (= the chemical processes in the body needed for life)”如：metabolite levels 代谢物水平。

burnout

表示“极度劳累；疲劳过度”，英文解释为“extreme tiredness usually caused by working too much”如：employees complaining of/suffering burn-out 抱怨/感到极度劳累的员工。

根据世界卫生组织，职业过劳（Occupational burnout）是一种由慢性工作压力导致的症候群，症状包含“精神耗尽、对工作的心理距离增加、对工作的负面感觉、以及工作效率的减少”。职业过劳不被归类为一种医学疾病。

In future studies, they hope to learn why the prefrontal cortex seems especially susceptible to glutamate accumulation and fatigue. They’re also curious to learn whether the same markers of fatigue in the brain may predict recovery from health conditions, such as depression or cancer.

在未来的研究中，他们希望了解为什么前额叶皮层似乎特别容易受到谷氨酸积累和疲劳的影响。他们还想知道大脑中同样的疲劳标志是否可以预测健康状况的恢复，如抑郁症或癌症。

susceptible

susceptible /səˈseptəbl/ 表示“易受影响（或伤害等）；敏感；过敏”，英文解释为“very likely to be influenced, harmed or affected by sb/sth”举个🌰：

Some of these plants are more susceptible to frost damage than others.

这些植物中有一些较其他的易受霜冻危害。

- 今日盘点 -

wear sb out

drowsy

cognitive

prolonged

toxic

byproduct

prefrontal cortex

fatigue

set in

illusion

cook sth up

gratifying

accumulation

noxious

preserve

integrity

arise

magnetic

resonance

spectroscope

monitor

pupil

dilation

synapse

employ

recipe

implication

metabolite

burnout

susceptible

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