Cape Argus E-dition

Study finds mental fatigue is all in the brain

SHAUN SMILLIE shaun.smillie@inl.co.za

I would employ good old recipes: rest and sleep. There is good evidence that glutamate is eliminated from synapses during sleep

MATHIAS PESSIGLIONE

Pitié-Salpêtrière University

THINKING hard makes your brain hurt and finally there is the science to prove it.

For a long time those who complained that they were feeling tired after stretches of power thinking were told it was all in their heads.

But now scientists have pinpointed just why you feel mentally exhausted after a night of cramming for an exam or sitting through a day-long meeting. It has all got to do with toxins. In a study released in the journal Current Biology this week, researchers found that an intensive cognitive workout causes potentially toxic by-products to build up in the part of the brain called the prefrontal cortex.

When this happens the brain gears down and shifts to low cost actions that require less effort, and with it comes that tired feeling.

“Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we’re doing and turn to a more gratifying activity,” said Mathias Pessiglione of Pitié-Salpêtrière University in Paris.

“But our findings show that cognitive work results in a true functional alteration – accumulation of noxious substances – 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 his colleagues wanted to unpack what mental fatigue was, although they already had a hunch it might be the brain having to recycle toxins that had accumulated because of extra neural activity.

To get a peek into what was happening in the brain during these cognitive workouts, they used magnetic resonance spectroscopy.

Two groups of volunteers were gathered for the experiment.

The first group were required to complete tasks where they had to think hard, while the second took it easy and handled far simpler cognitive tasks.

What the researchers found in the hard working group were tell-tale signs of fatigue that included reduced pupil dilation.

This group also began choosing tasks with little effort. They were also found to have had higher levels of glutamate in the synapses of their brain’s prefrontal cortex.

The authors were able to conclude that the accumulation of glutamate made further activation of the prefrontal cortex more costly, and this in turn made cognitive control difficult after a long day of heavy mental lifting.

The research could one day help to prevent burnout.

Through the monitoring of prefrontal metabolites medical professionals might be able to detect severe mental fatigue and adjust work loads accordingly. It might have applications in predicting recovery from health conditions, such as depression or cancer.

Pessiglione also advised people to avoid making important decisions when they’re tired.

Unfortunately, energy drinks and caffeine won’t help give the prefrontal cortex a pick me up. It comes down to a bit of age-old advice.

“I would employ good old recipes: rest and sleep. There is good evidence that glutamate is eliminated from synapses during sleep,” Pessiglione said.

METRO

en-za

2022-08-13T07:00:00.0000000Z

2022-08-13T07:00:00.0000000Z

http://capeargus.pressreader.com/article/281642488951837

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