Thinking too much and for too long can, yes, tire the brain — now we know how

Thinking too long and too hard does tire the brain, yes — and now we have scientific proof of that, according to scientists. It’s not like we don’t know it happens, but it’s always been hard to find physical proof of it, as sensation is subjective. If someone says they are mentally fatigued, all we can do is believe it. At least, until now.

It was not known why intense thoughts or heightened mental exertion caused cognitive fatigue, by the way. The sensation is described as more difficulty completing tasks or focusing on them, not exactly sleep or tiredness. Now, a neurotransmitter known for about 70 years comes to give us more information about brain fatigue: it is glutamate.

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tired the brain

Glutamate is the most common excitatory neurotransmitter in the brain, and since its discovery, it has been surprising scientists. Research indicates, for example, that these amino acids control the strength of brain signals by regulating their distribution to other neurons, and they can even excite neurons to death — loads of 8,000 glutamate molecules encapsulated in a single synapse pocket have been detected.

The thing is, too much glutamate can be a problem, and it’s linked to brain fatigue. Monitoring organ chemistry in 24 participants, scientists in a study published last Thursday (11) in the journal Current Biology put them to solve computational tasks for more than 6 hours.

In them, an increase in glutamate levels was detected in the lateral prefrontal cortex, the part of the brain associated with high cognitive abilities such as short-term memory and decision making.

Another 16 participants, who received simple tasks, did not show accumulations of the neurotransmitter in this part of the brain, leading the researchers to believe that extracellular glutamate may be one of the limits to human mental vigor. In other words, the brain may end up making cognitive tasks more difficult as a mechanism to protect our neurons from excess excitatory neurotransmitters.

Another theory talks about glucose, a substance used by the brain as a source of energy. It remains to be seen, however, how the lack of it would make thinking difficult, at least biochemically speaking. Some researchers propose that this causes a loss of dopamine in the brain, disengaging the individual from tasks more easily. This would make us look for more satisfying tasks, which would bring us more dopamine.

There is also evidence that glutamate is eliminated from synapses during sleep, which explains the mental renewal brought about by a good night’s rest. Functional magnetic resonance imaging (fMRI) of the prefrontal cortex has already shown that this part of the brain is involved in cognitive efforts that become less excitable over time: in other words, the more we use our mind, at the end of the day. the same activity will need more effort than at the beginning.

Now that we know that glutamate accumulates and makes the activation of the prefrontal cortex more costly after a day of intense mental effort, we need to find out why the amino acid accumulates more in this part of the brain, and find out more about its role in the organ. — and that’s exactly what the scientists plan to do. This is when their brains’ glutamate decreases again.

Source: Current Biology, J. Am. Chem. social

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