•The researchers also suggested brain scans could help to detect severe mental fatigue.
•Pessiglione and other researchers of the study like Antonius Wiehler wanted to understand what mental fatigue is.
Ever wondered why you will still feel tired and angry even after spending the entire day sitting at your working desk?
For most employed people, working during the eight-hour shift while taking regular breaks to walk to the coffee makers, or water dispenser or use the washroom does not amount to physical activity.
Sitting around thinking hard for hours makes one feel worn out, too. It all narrows down to mental status.
Recent research published in Current Biology on August 11, explains why this happens.
"Influential theories suggested 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," says Mathias Pessiglione, one of the study authors.
"But our findings show that cognitive work results in a true functional alteration. So fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning."
Pessiglione and other researchers of the study like Antonius Wiehler wanted to understand what mental fatigue is.
While machines can compute continuously, the brain can not, that is why we need frequent breaks and a good night’s rest, as human beings.
The evidence
To look for evidence, they used magnetic resonance spectroscopy (MRS) to monitor brain chemistry throughout a workday.
They looked at two groups of people: those who needed to think hard and those who had relatively easier cognitive tasks.
One of the signs of fatigue they noted was reduced pupil dilation, only in the group doing hard work.
They also had higher levels of brain activity in the brain's prefrontal cortex which makes cognitive control more difficult after a mentally tough workday.
Higher experiences of this often can also be deadly.
So, is there some way around this limitation of our brain's ability to think hard?
"Not really, I'm afraid," Pessiglione said.
"I would employ good old recipes: rest and sleep! There is good evidence that glutamate (the inflammation) is eliminated from part of the brain during sleep."
The researchers also suggested brain scans could help to detect severe mental fatigue.
They also advised people to avoid making important decisions when they are tired as mind control is more difficult after a mentally tough workday.