Physical labor wears people out physically, but what about sitting around thinking hard for hours? A study suggests that hard mental labor also makes people feel worn out and that being mentally exhausted from intense thinking is a real experience.
Mental or cognitive fatigue could arise from a long day of writing emails, making phone calls, attending meetings virtually or face-to-face, and even spending most of the day just sitting in a chair. Although this is a real experience, scientists have yet to fully understand why some cognitive tasks feel so draining.
Glutamate Buildup Contributes to Mental Fatigue
The paper "A Neuro-Metabolic Account of Why Daylong Cognitive Work Alters the Control of Economic Decisions" published in Current Biology suggests that the buildup of glutamate could be a contributing factor to mental fatigue after hours of thinking hard. Glutamate is a chemical that neurons use to send messages and is involved in learning and memory, which can be toxic at high levels.
Antonius Wiehler, Ph.D., a researcher at the Paris Brain Institute and one of the study's authors, said that fatigue might be an adaptation to reduce the accumulation of glutamate. In simpler terms, getting tired is the way the brain tells a person to stop glutamate levels so they will not get higher.
According to WebMD, the experiment involved 40 participants who were divided into two groups. The first group spent six hours on mentally draining tasks while the second group was given easier tasks.
The first group displayed more signs of fatigue at the end of the day, such as reduced pupil dilation and a tendency to favor less effort and fast rewards. For example, they would most likely choose to receive a smaller amount of money rather than wait for a larger sum.
More so, they are more likely to choose a less draining activity for a 30-minute task and a lower resistance level for 30 minutes on a stationary bicycle. That means they would rather choose tasks that need less self-control that requires less effort. Researchers hypothesize that it must have been too costly for the first group to apply control, hence choosing those tasks.
The team used magnetic resonance spectroscopy to monitor the brain chemistry of the participants, finding higher glutamate levels in the first group than in the second group. Wiehler explained that glutamate is important inside the cells, but it is potentially harmful outside and in between cells.
What Can You Do About Cognitive Fatigue?
Psychiatrist Dr. Alex Dimitriu, the founder of Menlo Park Psychiatry & Sleep Medicine, told Healthline that the first thing to know is how a person feels if he is not working. Understanding the reason behind the fatigue, whether it may be due to sleep, anxiety, or the level of busyness during the day is important.
He pointed out that the study mentioned that glutamate levels decrease during sleep, which adds to evidence of how important getting enough sleep is to fight cognitive fatigue.
Meanwhile, senior research scientist Jennifer Bramen, Ph.D., from the Pacific Neuroscience Institute at Providence Saint John's Health Center also told Healthline that avoiding multi-tasking can help prevent the brain from feeling worn out. She recommends spending time on each activity instead of doing more than one at the same time.
Also, changing the physical surroundings during breaks may provide benefits. Although it is tempting to stay glued to the desk, stretching and getting some sunlight and air are also crucial to one's well-being.
Experts also recommend drinking caffeine but not later than noon. Lastly, taking a power nap helps regulate the brain's level of excitement. It will be helpful next time to record when it is mostly cognitively draining to remind oneself not to make decisions during those periods.
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