Tiredness following mentally strenuous work is due to the build-up of certain neurotransmitters in the brain, a new study has found.
The Paris Brain Research Institute at the University Hospital of Pittier Salpetrière, France, found that the neurotransmitter glutamate builds up in the prefrontal cortex of the brain when mentally demanding work is done. The prefrontal cortex is the anterior part of the frontal lobe of the cerebral cortex, and the excitatory neurotransmitter glutamate is a potentially toxic metabolite. “I wanted to determine the cause of mental fatigue, which has remained a mystery until now,” said Dr. This is because mental fatigue has a huge impact on economic decisions, job management, schooling, and clinical treatment.
The research team investigated and analyzed 40 people who performed five cognitive tasks over six hours. The research team asked the experimental group (24 people) to do a more difficult or more demanding cognitive task, and the control group (16 people) to do a simpler or less demanding cognitive task. Then, magnetic resonance spectroscopy (MRS) was used to evaluate metabolic changes in the participants’ brains. The study found that significantly more glutamate accumulated in the prefrontal cortex of participants who performed more difficult or more demanding cognitive tasks. After hours of intense and challenging cognitive tasks, glutamate, a potentially toxic byproduct of neural activity, builds up in the prefrontal cortex. For this reason, it was analyzed that mental work for a long period of time causes ‘cognitive fatigue’ just like physical work. “When glutamate builds up, it causes cognitive fatigue, changing control over decisions,” Biller said.
According to the research team, because of the potential toxic effects, it is necessary to get rid of the excess glutamate, which can increase the effort required for mental tasks and cause fatigue. Cognitive regulation is a cognitive or mental process that enables an individual to adjust thoughts and behaviors according to goals while suppressing automatic or impulsive behavior. Cognitive control is required, for example, to control the urge to eat junk food (high-calorie, low-nutrition fast foods and instant foods) in pursuit of the long-term goal of maintaining a healthy weight. During cognitive fatigue, the ability to maintain cognitive control declines, increasing the likelihood of impulsive behaviors that result in immediate gratification.
Previous studies have shown increased glutamate release by neurons during tasks that require cognitive control. However, too much glutamate outside neurons can interfere with communication between neurons and cause toxic effects. So, if glutamate builds up during more difficult or more demanding cognitive tasks, you need to control its levels. Controlling glutamate levels requires more cognitive effort, which can lead to people taking less cognitively demanding choices. Studies have also shown that glutamate levels in the brain are lowered following sleep. This means that getting a good night’s sleep can reduce cognitive fatigue.
The researchers said further studies are needed to demonstrate a causal relationship beyond the association between mental fatigue and glutamate accumulation. We are also looking at the possibility that changes in glutamate levels may occur as by-products of other metabolic processes. The research team said that by monitoring and analyzing prefrontal metabolites, signs of severe fatigue and exhaustion might be detected in various situations. This can be helpful in controlling the work of executives and employees, managing the physical condition of athletes who are running heavy training programs or before competitions, and controlling the learning intensity of students before exams. The results of this study (A neuro-metabolic account of why daylong cognitive work alters the control of economic decisions) were published in the international academic journal ≪Current Biology≫ and introduced by the British health medical media ‘Medical News Today’.
By Kim Young-seop, staff reporter edwdkim@kormedi.com
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