Thinking long and hard can cause brain drain: ScienceAlert

19th century American writer Wallace D. Wattles once claimed“Thinking is the hardest and most exhausting of all works.”

At first glance, this may seem like a controversial comparison, but a new study suggests that thinking too hard for too long can really exhaust your brain, just like exercise can exhaust the body.

Hard physical labor is obviously tiring, but the sweat on a person’s forehead or the quivering of his muscles says nothing about the intensity of his thoughts.

When someone says they feel mentally drained, we just have to take their word for it.

As a result, scientists still don’t fully understand why intense thinking causes cognitive fatigue. It’s not exactly a sleepy feeling; rather, it is a feeling that tasks are getting harder and harder to accomplish or focus on.

Some researchers now suspect the most abundant excitatory neurotransmitter in the brain is responsible for this lack of mental stamina.

Glutamate is an excitatory amino acid that has not been correctly described in the 1950salthough it is present in more than 90% of neuron-to-neuron communication in the human brain.

Over the decades, this underappreciated chemical has continually surprised scientists. Neurons, for example, have been shown control the strength of their signals in the brain by regulating the amount of glutamate they release into other neurons.

Glutamate can even excite neurons to deathwith as much as 8,000 encapsulated glutamate molecules in a single pocket of a synapse, the junction where two neurons meet.

The overabundance of glutamate is clearly a problem, and that’s part of why it’s been linked to brain drain.

When monitoring the brain chemistry of 24 participants tasked with performing strenuous computerized sorting tasks for more than six hours, the researchers found an increase in glutamate in the lateral prefrontal cortex. It is the part of the brain associated with higher-order cognitive powers, such as short-term memory and decision-making.

In comparison, 16 other participants who were assigned easier tasks for the day showed no signs of glutamate buildup in this part of their brain.

As such, researchers believe that an increase in extracellular glutamate may be at least one of the limiting factors in human mental endurance.

Obviously, the brain also gobbles up a lot of glucose when it works. Other theories suggest that this energy source is probably another limiting factor, but it’s still unclear how a loss of glucose makes thinking more difficult, from a biochemical perspective.

Some researchers have offers that a drop in blood sugar triggers a loss of dopamine in the brain, which makes it easier for a person to lose interest in certain cognitive tasks.

“Influential theories suggest that fatigue is a kind of illusion concocted by the brain to make us stop whatever we are doing and turn to a more rewarding activity,” Explain clinical psychologist Mathias Pessiglione from the Pitié-Salpêtrière University in Paris, France.

“But our results show that cognitive work results in a real functional alteration – accumulation of harmful substances – so fatigue would be a signal that makes us stop working but for another purpose: to preserve the integrity of brain function.”

Pessiglione also says there is good evidence that glutamate is cleared from synapses during sleep.

This could be part of the reason why a night’s rest can leave a person feeling mentally refreshed the next day.

brain imaging study as of 2016, which used a MRI (fMRI), also found that the lateral prefrontal cortex (lPFC) was involved in intense cognitive effort that reduced its excitability over time.

Activating this region at the end of a long, hard day would require even more effort than at the beginning. Hence the feeling of brain drain.

“Taken together with previous fMRI data, these findings support a neuro-metabolic model in which glutamate accumulation triggers a regulatory mechanism that makes lPFC activation more costly, explaining why cognitive control is more difficult to mobilize. after an intense day’s work”, Pessiglione and his colleagues conclude.

Glutamate is an incredibly fast acting neurotransmitter. This is part of what makes this amino acid so powerful. But it also makes the chemical difficult to measure.

Studies like the current one are using new technologies to further explore the rapid role of glutamate in our brains.

The authors now hope to investigate why glutamate accumulates so much in the prefrontal cortex compared to other parts of the brain.

The study was published in Current biology.

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