Food For Thought

"Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity."

"But our findings show that cognitive work results in a true functional alteration -- accumulation of noxious substances -- so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning."

Mathias Pessiglione, Pitie-Salpetriere University, Paris

"This dissociation [peoples' inability to listen to their bodies and take heed] is common in everyday life; for instance when people go on working or driving and start making errors because they failed to detect their true fatigue state."

Researchers on brain fatigue

Creator: Igor Ustynskyy

 

It isn't just our imagination that thinking and performing thoughtful work can lead to fatigue, by overworking one's brain. Both physical and mental 'work' are equally capable of producing a state of tiredness leading to exhausting lethargy. Advice given to office workers to get up from time to time from their computers and take a break, walk around for a few minutes doesn't only exercise one's limbs, but also gives the limbic brain a needed rest, to come back following a break feeling a little refreshed. 

It's not imagination that leaves people feeling tired and spent after a day of sitting at a desk, akin to a degree to someone spending the day on construction work. The mind and body are a working team, after all.  An overworked brain, according to a recent study, can lead to poisoning the brain with chemicals released to the prefrontal cortex, forcing the body to slow down in a bid for time to enable the production of the toxins to be flushed away.

When a situation has reached the point of continuing to push the brain to perform past exhaustion, thinking becomes difficult, manifesting as fatigue and tiredness, as both body and mind require a routine break to excrete toxins. A conclusion dispelling a long-standing theory that feeling tired as a result of thinking is a myth, according to the researchers.

Brain chemistry was monitored over the course of a working day in 40 people, 24 of whom were required to use their brain intensively, while the remainder were not. The group performing difficult mental work saw researchers identify signs of fatigue, including reduced pupil dilation, along with signs that low-effort decisions indicative of tiredness were being made.  

 

Higher levels of a chemical called glutamate appeared in the brain's prefrontal cortex, accumulating in the synapses between neurons, interfering with the transmission of messages passed throughout the brain. According to the study authors, this is seen as proof that glutamate prods further activation of this part of the brain in an effort, such that cognitive control becomes more difficult following a tough day.

There are no shortcuts to stop the brain making you tired; only a break or a nap can mend the state of tiredness. Volunteers were given tasks interspersed with choice trials, asked to choose between cash rewards -- small values given instantly, or larger values at a later date. Those volunteers subjected to difficult tasks were likelier to choose the low-effort rewards requiring less waiting time.

When volunteers were also asked to score their levels of fatigue, the two groups rated themselves similarly, leaving the researchers to conclude that people are not attuned to messages sent by the body to the brain. The study was published in the journal Current Biology.

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