Have you ever found yourself physically exhausted after a long day at work, even if you were just sitting behind a computer table?
Scientists have discovered that there is a reason for this: a toxic chemical begins to build up in the brain after being active for long periods of time. So the brain turns toward actions that don’t require the same amount of effort to avoid circulating this chemical, glutamate, anymore.
This manifests itself as a lack of desire to work, or cognitive fatigue, say neuroscientists from Pitié-Salpêtrière University in Paris, France.
Dr. Matthias Besiglione, who led the study, said: ‘Influential theories suggest that fatigue is a kind of illusion that the brain creates to make us stop what we’re doing and switch to a more satisfying activity. But our findings show that cognitive work leads to real functional change – the accumulation of substances Harmful — so fatigue will actually be a signal to stop working but with a different purpose: to keep the brain functioning.”
Physical fatigue is a direct result of hard manual labor, but thinking hard for a long time instead causes mental exhaustion, causing symptoms such as a lack of motivation and the ability to focus.
In the study, published in Current Biology, researchers set out to understand what mental fatigue really is and why it manifests itself.
To do this, they used magnetic resonance spectroscopy (MRS) to monitor the brain chemistry over the course of a work day for two groups of study participants.
They divided the group into easy and difficult computer memory tasks that involved remembering and matching a series of letters of different colors for nearly six and a half hours.
The results showed that people with more difficult tasks tended to options that offered smaller rewards for less effort or those that produced results more quickly.
Next, the scientists studied their levels of glutamate at synapses in the prefrontal cortex of the brain, and found that they were higher for the group with mentally stressful tasks.
The researchers say this supports their hypothesis that glutamate buildup causes the brain to switch to less stressful actions.
This is her way of avoiding cycling or increasing the buildup of this toxic chemical, which can impair brain function.
The researchers hope this finding will provide a new way to detect severe mental fatigue, and inform work agendas to help avoid burnout.
In future studies, they hope to further understand why the prefrontal cortex experiences glutamate buildup and fatigue after neural activity.
They’re also curious to see if the same signs of brain fatigue might predict recovery from health conditions, such as depression or cancer.
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