Intense cognitive work over several hours leads to potentially toxic byproducts building up in the brain, causing fatigue.
Published Aug 16, 2022 | 8:00 AM ⚊ Updated Aug 16, 2022 | 8:00 AM
Cognitive work results in a true functional alteration— accumulation of noxious substances in the brain. (Creative Commons)
Work involving intense concentration can be as tiring as physical work, and can result in exhaustion.
According to a study, intense cognitive work over several hours causes potentially toxic byproducts to build up in the part of the brain known as the prefrontal cortex, which leads to cognitive fatigue.
Researchers have found out that these byproducts, in turn, alter your control over the decisions you make.
“It’s no surprise that hard physical labour wears you out, but we don’t give priority to our mental health. It (the brain) gets tired, it needs rest just like our other body parts. Fatigue of our mind is a normal phenomenon,” Dr Manovikas Prasad, a psychiatrist in Hyderabad, told South First.
“Influential theories suggest that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity,” said Mathias Pessiglione of Pitié-Salpêtrière University in Paris and one of the authors of the study.
“Our findings show that cognitive work results in a true functional alteration — accumulation of noxious substances — so fatigue would indeed be a signal to make us stop working but for a different purpose: To preserve the integrity of brain functioning,” added Pessiglione.
To understand what mental fatigue really is, the researchers explored whether it had to do with the need to recycle potentially toxic substances that arise from neural activity.
To look for evidence of this, they used magnetic resonance spectroscopy (MRS) to monitor brain chemistry over the course of a workday. They looked at two groups of people: Those who needed to think hard and those who had relatively easier cognitive tasks.
They saw signs of fatigue, including reduced pupil dilation, only in the group doing hard work.
They also had higher levels of glutamate in the synapses of the brain’s prefrontal cortex.
Together with earlier evidence, the authors say it supports the notion that glutamate accumulation makes further activation of the prefrontal cortex more costly, such that cognitive control is more difficult after a mentally tough workday.
“Rest and sleep. There is good evidence that glutamate is eliminated from synapses during sleep. Avoid making important decisions when they’re tired,” said the researchers.
