Sep 03, 2022 12:00:00

Why is brain work 'tired' without moving the body?

Thinking seriously about things looks like just lying down or sitting, but in reality it can be very exhausting. A new study suggests that just as strenuous exercise can be physically exhausting, so can mental work.

A neuro-metabolic account of why daylong cognitive work alters the control of economic decisions: Current Biology

https://doi.org/10.1016/j.cub.2022.07.010

Why thinking hard makes you tired | EurekAlert!
https://www.eurekalert.org/news-releases/960845

It Really Is in Your Head: Thinking Hard And Long Can Cause Brain Drain : ScienceAlert
https://www.sciencealert.com/it-really-is-in-your-head-thinking-hard-and-long-can-cause-brain-drain

People who have done strenuous physical labor can quickly see that they are tired from the appearance of perspiration all over the body, trembling muscles, and heavy breathing. On the other hand, mental work does not change the appearance so much, and it is not possible to judge whether the person is tired unless the person says 'I'm tired.' Still, if you've actually thought through a school test or a difficult assignment, you can agree that 'brain work is exhausting.'

This fatigue is more like a kind of cognitive fatigue, and it's more like a feeling of difficulty performing or concentrating on a task rather than feeling sleepy. However, scientists still do not understand well why brain work is tiring.

A new study has shown that

glutamic acid , known as one of the umami ingredients, may be involved in mental fatigue. Glutamate is a major excitatory neurotransmitter in the central nervous system and plays an important role in higher brain functions such as memory and learning. is known.

The research team conducted an experiment in which 24 subjects performed an intense computer task for more than 6 hours and monitored the brain using MR spectroscopy , a type of MRI. As a result, it was found that subjects who used their brains a lot had increased glutamate in the lateral prefrontal cortex , which is involved in higher cognitive abilities such as short-term memory and decision-making.

On the other hand, no increase in glutamate in the lateral prefrontal cortex was observed in 16 subjects who performed a simple computer task on the same day. From these results, the research team speculates that increased glutamate may be one of the factors limiting human mental endurance.

Among the hypotheses proposed so far regarding fatigue due to mental work, there were many that it was caused by some kind of deficiency, such as ``the lack of energy in the brain'' and ``the decrease in dopamine has an effect''. thing. But the hypothesis that it's caused by an increase in glutamate, which can be a toxic substance in excess, suggests that brain work really does result in functional changes in the brain.

``There is evidence that glutamate is cleared from synapses during sleep,'' said clinical psychologist Mathias Pessiglione, a senior author on the paper. claimed.