Thinking too much tires. Anyone who spends their hours to ‘squeeze neurons’ You know that, no matter how much you spend all day sitting at a table, jobs that require a lot of concentration and reasoning in the long run can also cause an intense feeling of exhaustion. A fatigue that affects both physically and mentally. But how can it be that our body feels exhausted from thinking so much? What causes this feeling of tiredness? And, above all, is there anything we can do to avoid this mental fatigue? An international team of neuroscientists has found some keys to understanding this phenomenon.
Lets start by the beginning. For understanding what happens in our brain when we make intense cognitive work for several hours. As revealed a new studio published this Thursday in the scientific journal ‘Current Biology’when “we think a lot” and “for many hours” a series of substances accumulate in our brain that, in excess, hinder the functioning of our gray matter. To be more specific, the recently published research suggests that people who spend a lot of time thinking accumulate large amounts of glutamate (one of the excitatory neurotransmitters, responsible for ‘triggering’ the action of neurons) in the prefrontal cortex (one of the areas of the brain dedicated to managing from complex cognitive processes to decision making).
This process seems to be intensified depending on the intensity of cognitive activity as of time spent on it. In this sense, then, it is explained why it is more tiring to carry out activities that require concentration and analysis than others that are more mechanical. One of the most illustrative examples, as explained by the team of neuroscientists who have led this work, is that of chess players. It is said that even the best in the profession they start to fail when they are four or five hours into the game. It is usually explained that many of the mistakes made later in the game would be much more unlikely early in the game, when the players have the ‘more rested brain’.
“Functional disturbance”
But what is the relationship accumulation of neurotransmitters with mental fatigue? Or put another way. Why does an excess of glutamate in one area of our brain make us feel more exhausted? Everything indicates that the accumulation of substances causes a true “functional impairment“of the brain which, in turn, alter decision making. “Mental fatigue presents itself as a kind of ‘alert signal’ that tells us to stop working to preserve the integrity of the brain“, explains Mathias Pessiglione, a researcher at Pitie-Salpetriere University and one of the main authors of this recently presented study.
“Mental fatigue is presented as a kind of ‘warning signal’ that tells us to stop working to preserve the integrity of the brain”
Mathias Pessiglione, neuroscientist
The research is based on the analysis of a series of MRIs conducted to monitor the brain chemistry of a group of office workers. To do this, the scientists observed two groups of employees. On the one hand, workers who spend many hours on intense cognitive work. And on the other hand, people who had easier cognitive tasks. The comparison between the two revealed, for example, that those who spent more effort and hours thinking, in addition to accumulating more neurotransmitters in the prefrontal cortex, also experienced typical symptoms of exhaustion as the reduction in the size of the pupils. Hence, in a way, the famous mental fatigue can be measured.
This approach contradicts one of the most widespread hypotheses to explain this phenomenon. Until now, it was believed that mental fatigue was a kind of “illusionary feeling“invented by our brain to ‘force’ us to put aside activities more demanding cognitive abilities (such as thinking very intensely for a long time) to spend your efforts on something more rewarding (such as watching a humorous video, eating something sweet or simply disconnecting). This mechanism, in turn, is also used to explain why when we are especially exhausted we prefer to watch the same episode of the Simpsons over and over again (in which we already know where the funniest moments are and, therefore, we can ‘unplug the brain’ and relax) before betting on a new series (which would require more attention).
Remedies against mental fatigue
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Once the possible mechanism behind brain fatigue, many will wonder if something has also been discovered to stop the cascade of neurotransmitters that accumulate in our gray matter and hinder our thinking. “Not yet,” the researchers who have led this work respond forcefully. “The best thing to stop mental fatigue is to use remedies as old as rest and sleep“, comments Pessiglione, recalling that, according to several studies, synapses that occur in our brain during sleep remove excess glutamate. And this, in turn, could ease feelings of mental exhaustion.
“The best thing to stop mental fatigue is to use remedies as old as rest and sleep”
As explained by the team of neuroscientists responsible for this new finding, in the future it will also be necessary to investigate why the prefrontal cortex is especially susceptible to the accumulation of glutamate. And if this type of marker could be used for both detect cases of severe mental fatigue or as for seek treatments to deal with this type of brain exhaustion.