A study recently published in the scientific journal Current Biology shows that prolonged intense cognitive work — around 4 to 5 hours — causes potentially toxic byproducts to accumulate in the part of the brain known as the prefrontal cortex and thus lead to burnout. . As cognitive fatigue sets in, behavior begins to change and causes people to seek (albeit unintentionally) paths that require less effort, the researchers explain.
“Influential theories have suggested that fatigue is a kind of illusion invented by the brain to make us stop what we are doing and turn to a more fulfilling activity, but our findings show that cognitive work results in a true functional change, with accumulation of harmful substances. So fatigue would in fact be a sign that would make us stop working, but with a different purpose: to preserve the integrity of the brain’s functioning”, says one of the study’s authors, researcher Mathias Pessiglione, from the Pitié-Salpêtrière University in Paris. , in France.
The researchers used magnetic resonance spectroscopy to monitor brain chemistry during a workday. They looked at two groups of people: those who needed to think a lot and those who had easier cognitive tasks. In the groups that did heavy work, signs of fatigue were seen, including reduced pupil dilation, as well as showing a shift in their choices to options that offered short-term rewards with little effort.
This group also had higher levels of the neurotransmitter glutamate at synapses in the brain’s prefrontal cortex. That, jTogether with previous evidence, it supports the notion that glutamate accumulation makes additional activation of the prefrontal cortex more expensive, so that cognitive control is more difficult after a mentally difficult workday.
For Pessiglione, there is no way around this limitation of our brain’s ability to think a lot. The specialist indicates the “good old recipes: rest and sleep”. “There is good evidence that glutamate is cleared from synapses during sleep,” he said.