Nature: Is your brain tired? Researchers are discovering the roots of mental fatigue

[Kalliope]

Putting this article in the "General ME/CFS News" section as it mentions ME several times.
Some of the article is behind paywall.

Quotes:

To better understand fatigue, Pessiglione, Chib and other researchers are trying to bridge an understanding of its biochemical workings with how it affects motivation. The current hypothesis: cognitive fatigue arises from metabolic changes in parts of the brain that are responsible for cognitive control. And those changes, whether resulting from depleted energy stores or amassed waste, alter how brain circuits weigh the costs and benefits of exerting mental effort — nudging decisions towards easier options that are more immediately rewarding.

...

In people with long COVID or ME/CFS, a small mental task can feel as intimidating as performing brain surgery.

For Ana Lia Tamariz, an artist and health-and-wellness coach in Miami, Florida, who has ME/CFS, simply listening to music or reading a book often requires immense effort. “Sometimes, I cannot read one more word,” she says. “Imagine coming out of anaesthesia from a surgical procedure groggy. Imagine you never exit that state.”

For her, the cognitive and physical fatigue can be hard to separate. Any cognitively demanding task can make her physically drained, she says. And anything physically demanding can leave her mentally spent. Tamariz says she is constantly doing the calculation: “Is this worth my energy?”

Is your brain tired? Researchers are discovering the roots of mental fatigue

Better ways to measure cognitive exhaustion could point to treatments for long COVID and other debilitating disorders.

www.nature.com

 

[Jonathan Edwards]

I find it hard to believe that the problem is energy drainage or waste accumulation. A brain keeps working for hours - for a junior doctor sometimes 36 hours on the trot. Energy must be constantly supplied. If it wasn't then problems would occur very quickly. The same goes for waste - if build up was a problem it would occur much quicker.

And when you have a viral infection like flu you have severe mental fatigue when there is no reason to think energy supply or waste removal should be problematic. Everything suggests that the brain is being told to stop trying to do things in order to get you to lie down and stop spreading germs.

 

[rvallee]

Ugh. We're going to be hearing a lot of nonsense about effort preference in the next few years, are we?

In a 2022 study, Pessiglione and his team simulated a workday by asking otherwise healthy participants to spend several hours on either easy or hard versions of the same cognitive tasks.

Ayup. We sure are. the study doesn't state effort preference but it explicitly describes it as a preference related to effort, 13 times.

Good grief. Can we have machines take over already? Humans are so not fit to do research on humans, we're only good at dealing with lab stuff, math and engineering. Basically the exact opposite of the usual tropes. LLM can write better poetry than 99% of humans, and massively outperform most humans at empathy but struggle with basic reasoning.

They're totally mixing the concept of fatigue and tiredness, which have little in common. It's fine and normal to be tired after making an effort, it's not at all normal to be pathologically weak and exhausted all the time, or even the awful combination of both from lack of sleep. It's absurd how the most basic concepts of health are the least well defined and understood.

And those changes, whether resulting from depleted energy stores or amassed waste, alter how brain circuits weigh the costs and benefits of exerting mental effort — nudging decisions towards easier options that are more immediately rewarding.

And what they are referring here is obviously not tiredness itself but an adaptation to it, similar to how on a very long walk people's gait will adapt to minimize energy expenditure.

This is not progress. It's literally regress. They're still whacking at the same dead horse.

 

[obeat]

We need to get away from the concept of energy and use the concept of stamina