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。
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.