What is Behind Mental Fatigue?

A common issue faced by people today is mental fatigue. It always feels like there is too much on our plates, never ending cognitive workloads to deal with. The issue is, no one knows exactly why we get mentally fatigued, how it happens, or why we feel it the way we do. The research into mental fatigue is important, so we can learn how to avoid it. However, researchers this time wanted to look into the role of glutamate, a neurotransmitter, in mental fatigue. Glutamate is important for synaptic connections, learning, and memory and must be tightly regulated by the body or else it can lead “neuronal dysfunction”.

The researchers took 40 participants and placed them in two groups. One group was given easy mental tasks to complete, and the other was given hard mental tasks. They were asked to perform the tasks inside and outside of a brain scanner, and for the same duration.

At the end of the study, the participants from both groups reported equal levels of mental fatigue. However, those in the hard mental task group had reduced pupil dilation, preferred immediate rewards to waiting longer for better rewards, and higher levels of glutamate in the prefrontal cortex.

The results show that high cognitive workloads lead to the buildup of byproducts in the prefrontal cortex, a rise in glutamate, leading the brain to switch to lower-cost actions, like eating out instead of figuring out what you want to eat, and then cognitive fatigue.

Previous research has hypothesized that mental fatigue was merely an illusion by the brain but researchers in this study believed they found a “functional alteration” in the brain caused by the buildup of substances, showing that mental fatigue has the purpose of preserving brain function, and is not merely an illusion. The researchers point out that there is still much more to learn about this mechanism.

Original Article: https://www.psypost.org/2022/09/neuroimaging-study-suggests-mental-fatigue-helps-preserve-the-chemical-integrity-of-the-brain-63926

Study: https://www.sciencedirect.com/science/article/abs/pii/S0960982222011113

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