Exhaustion due to intensive thinking – a phenomenon that is mainly known to people who work primarily cognitively. But why is that? A research team from France has an idea…
Do you know the feeling of being completely exhausted after work and falling exhausted on the sofa – even though you’ve actually “only” been sitting on your office chair all day? While it is often considered normal when doing physical work to be tired in the evening, many office workers sometimes wonder about the evening low.
But yes – even thinking makes us tired at some point. A recent study published in the journal Current Biology now shows what mental work costs us.
The French research team led by Antonius Wiehler from the Paris Brain Institute had 40 participants solve various tasks on the screen. Sometimes they had to sort letters by color, sometimes by vowel and consonant. The setting also included memory exercises.
The researchers had their subjects complete not hundreds but thousands of these tests at two different levels of difficulty in order to achieve fatigue.
Exhaustion: how long can we think?
“After six hours, regardless of the difficulty of the task, both groups said they felt exhausted,” said Antonius Wiehler, first author of the study and behavioral scientist at the Paris Brain Institute, when presenting the study we are conditioned to feel exhausted after a day’s work.
Now the Paris research team is not the first group to take on the phenomenon of thought fatigue. A few years ago, scientists were able to find out, for example, that the lateral prefrontal cortex plays a major role in intensive thinking and important decisions.
However, little research has been done on why all of this sometimes leads to exhaustion and poor concentration.
Glutamate makes it difficult for us to think
So the Paris scientists used a special magnetic resonance spectroscopy to take a look at what happens in the brain during mental work. The result: glutamate makes it difficult for us to think. “In the groups that had to solve the more difficult tasks, the glutamate concentration rose significantly more over time,” explains Wiehler.
The amino acid glutamate is one of the most important messenger substances in the brain and can not only cause concentration problems, but also headaches and tachycardia. In high concentrations, however, glutamate is toxic. Reason enough for our body to actively regulate the glutamate balance under normal circumstances. However, when we do intensive mental work, the balance seems to be difficult.
When glutamate takes control
And what if glutamate takes over? The research team has an assumption: if the front cerebral cortex produces too much glutamate, it becomes more difficult to activate nerve cells. Actually, the area in the brain responsible for regulating feelings, planning actions and maintaining self-control. An excess of glutamate leads to exhaustion and a lack of self-control.
Antonius Wiehler also used the study to show what this means for our everyday lives: He gave the subjects a choice: “Do you want 20 euros now, or 50 euros in a year?” The participants who had to solve the cognitively more difficult tasks tended to opt for quick money, while the other group took a longer-term view.
Wiehler’s conclusion: “When cognitive fatigue sets in, we opt for simpler processes or actions that, for example, do not require effort or waiting.”
Glutamate makes you tired – right?
Overall, the study shows that glutamate plays a role in cognitive fatigue. Fritjof Helmchen from the Institute for Brain Research at the University of Zurich said in an interview with “Spektrum”: “It is not clear whether an increased glutamate content causes a decrease in nerve activity in the front cerebral cortex, but the study shows that both are related. “
A slight increase in the glutamate level under targeted stimulation is nothing new for the neurophysicist Harald Möller from the Max Planck Institute. In an interview with the German Press Agency, he points out that the messenger substance quickly falls off again after the stimulation has ended. Therefore, in his opinion, the French researchers should also have measured the glutamate content during rest phases in order to have a holistic picture.
Either way – glutamate plays a role when we want to go straight from the office chair to the sofa. And according to the Parisian scientists, it is also what brings our glutamate balance into balance: a large portion of sleep.
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Source: Stern
