Why does thinking so much tire?

After hours of complex work that requires a lot of thought and concentration, it is normal to feel a massive mental fatigue. And no, that’s not in your head. Researchers at the University of Paris in France have discovered that the sensation is caused by the accumulation of toxic substances that the brain produces when required to the extreme. The organ does this as a precaution, to prevent further severe wear and tear of the neural circuits involved in cognition activities, which are mainly concentrated in the prefrontal cortex. This is why thinking is so tiring.

To this day, the idea has been that mental exhaustion is the product of an illusion created by the brain so that the individual leaves the daunting task to devote himself to something more enjoyable. “But what our study showed is that stressful mental work leads to real physiological change,” says Matthias Besiglione, the work coordinator. “Fatigue is then a signal for us to stop working, but for another purpose: to preserve brain function,” he adds.

The research revealed that after a long period of mental work, a buildup of glutamate, one of the compounds that circulates through the brain, occurs. The process gradually makes the activity of thinking more difficult.

Scientists say that when you get to this point, there is no point in insisting. It is better to stop and rest. “Sleep helps too. There is evidence that glutamate is eliminated during sleep,” says Bisiglione.