上班很累？可能是你思考过度了

上班族们，如果你在办公室忙碌了一天后感到筋疲力尽，可能是因为你想得太多了。研究人员发现，过多使用脑力会导致精神疲劳，使人更难做出决定。科学家们分析了两组人在大约一个工作日内的大脑化学成分变化。其中一组分配到了简单的任务，而另一组分配到了要求更高的相同认知任务。

结果显示，瞳孔扩张缩小等疲劳迹象只有在执行更复杂任务的组中被记录下来。

巴黎皮蒂耶-萨勒佩特里埃大学附属医院(Pitie-Salpetriere University Hospital)的研究人员利用磁共振波谱技术发现，高要求的认知工作导致了谷氨酸在大脑前额叶皮层区域的积累。谷氨酸是一种神经细胞用来向其他细胞传递信号的化学物质。管理过量的谷氨酸会使其他前额叶皮层的活动变得更加困难，例如计划和决策，导致受试者在认知疲劳开始时更喜欢低努力、高回报的行为。

该研究作者之一的马赛亚斯·佩西利昂(Mathias Pessiglione)表示，之前的理论表明，疲劳是大脑制造的一种错觉，是为了让人们停止正在做的事情，转而从事更令人愉悦的活动。“但我们的研究结果表明，认知工作导致了真正的功能变化：有害物质的积累。因此，疲劳确实是让我们停止工作的信号，但目的不同：保护大脑功能的完整性。”他表示。

研究人员称，监测大脑前额叶皮层的化学变化可能具有实际意义，比如帮助检测严重的精神疲劳，从而避免职业倦怠。

The results showed that signs of fatigue such as pupil dilation and contraction were recorded only in the group performing more complex tasks.

Using magnetic resonance spectroscopy, researchers at the affiliated Hospital of Pettiere-Salepetrier University (Pitie-Salpetriere University Hospital) in Paris found that demanding cognitive work led to the accumulation of glutamate in the prefrontal cortex. Glutamate is a chemical that nerve cells use to send signals to other cells. Managing excess glutamate makes other prefrontal cortex activities more difficult, such as planning and decision-making, causing subjects to prefer low-effort, high-reward behaviors at the beginning of cognitive fatigue.

Mathias Pessiglione, one of the authors of the study, said previous theories suggested that fatigue was an illusion created by the brain to get people to stop what they were doing and switch to more enjoyable activities. “but our findings suggest that cognitive work leads to a real functional change: the accumulation of harmful substances. So fatigue is indeed a sign that we stop working, but for a different purpose: to protect the integrity of brain function. ” He said.

Researchers say monitoring chemical changes in the prefrontal cortex may be of practical significance, such as helping to detect severe mental fatigue to avoid job burnout.