How Does The Brain Get Tired?

This piece, by Onno Berkan, was published on 02/04/25. The original text, by Qi et al., was published by the Journal of Engineering (China) on 04/02/19.

This Tongji University study looked at the neural correlates of mental fatigue. This feeling of tiredness and exhaustion can lead to serious consequences, including reduced productivity and increased accidents, particularly among night-shift workers and medical residents.

The study explains that despite over 100 years of research, scientists still don't fully understand exactly how mental fatigue works in the brain. Several theories try to explain it: some suggest that boring, repetitive tasks lead to fatigue because our minds wander; others propose that we have a limited pool of mental resources (willpower) that gets depleted with use. About 38% of US workers report experiencing fatigue, with two-thirds saying it reduces their productivity.

Recent research has revealed that mental fatigue isn't just about individual brain areas becoming tired– it's about how different parts of the brain communicate with each other. When we're mentally fatigued, the brain's network becomes less efficient, with different regions having more difficulty working together. Taking breaks can help recover from fatigue and improve cognitive performance.

The study found different types of tasks cause different patterns of fatigue in the brain. For example, driving simulation and vigilance tasks showed distinct effects on brain network organization. During prolonged driving, the brain's network becomes less efficient at communicating, likely due to the monotonous nature of the task.

One important finding is that people vary significantly in how resistant they are to mental fatigue, suggesting that some individuals may naturally handle long periods of mental work better than others. The research also shows that mental fatigue isn't just about specific brain regions becoming tired– it involves changes in both local brain areas and the broader network of connections throughout the brain.

The researchers believe this new understanding of how brain networks change during mental fatigue could lead to better ways to detect and prevent fatigue-related errors in the workplace. They suggest that by monitoring brain network changes, we might be able to identify when someone is becoming dangerously fatigued before their performance significantly declines.

This study represents an important shift in how scientists study mental fatigue, moving from looking at individual brain regions to examining how the entire brain network functions together. The researchers believe this approach will not only help us better understand why we get mentally tired but could also lead to practical applications for preventing fatigue-related accidents and improving workplace safety.

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