Until recently, scientists thought that, much like muscles, the brain becomes fatigued when it uses up energy.

直到最近，科學家們還認為，就像肌肉一樣，大腦在耗盡能量後也會變得疲勞。

The problem with that theory is that the energy needed to think is pretty minimal.

這一理論的問題在於，思考所需的能量微乎其微。

So if it's not a lack of energy that causes cognitive fatigue, what does?

那麼，如果不是因為缺乏能量導致認知疲勞，那又是什麼原因呢？

In 2022, a team of scientists asked participants to perform six hours of various assignments that involved thinking.

2022 年，一個科學家小組要求參與者完成 6 個小時的各種涉及思考的任務。

One group was asked to do easy tasks and another, hard tasks.

一組被要求完成簡單的任務，另一組則被要求完成困難的任務。

Throughout the study, the scientists measured the biochemical changes in the participants' brains.

在整個研究過程中，科學家們測量了參與者大腦中的生化變化。

When the volunteers were performing hard tasks, the scientists found higher concentrations of glutamate in the lateral prefrontal cortex, the part of the brain associated with cognitive control.

當志願者執行艱鉅任務時，科學家發現外側前額葉皮層中的穀氨酸濃度更高，而這部分大腦與認知控制有關。

Glutamate is an excitatory neurotransmitter, a chemical signal which triggers neurons to fire.

穀氨酸是一種興奮性神經遞質，是一種觸發神經元發射的化學信號。

Scientists think that the build-up of glutamate might make it more difficult for the prefrontal cortex to perform activities, such as planning, decision-making, and learning.

科學家們認為，穀氨酸的堆積可能會使前額葉皮層更難完成規劃、決策和學習等活動。

When you rest or sleep, the glutamate levels fall.

休息或睡眠時，穀氨酸水準會下降。

Scientists speculate that when thinking makes you feel tired, it's your brain signaling that you need a break to preserve its function.

科學家推測，當思考讓你感到疲倦時，是你的大腦在發出信號，告訴你需要休息以保持其功能。

Future research into glutamate levels in the brain could help scientists devise a way to help avoid burnout.

未來對大腦中谷氨酸水準的研究可能會幫助科學家們設計出一種避免倦怠的方法。