How thinking hard makes the brain tired | The Economist - 0 views
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brain research science psychology brain science fatigue
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Mental labour can also be exhausting. Even resisting that last glistening chocolate-chip cookie after a long day at a consuming desk job is difficult. Cognitive control, the umbrella term encompassing mental exertion, self-control and willpower, also fades with effort.
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unlike the mechanism of physical fatigue, the cause of cognitive fatigue has been poorly understood.
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It posits that exerting cognitive control uses up energy in the form of glucose. At the end of a day spent intensely cogitating, the brain is metaphorically running on fumes. The problem with this version of events is that the energy cost associated with thinking is minimal.
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To induce cognitive fatigue, a group of participants were asked to perform just over six hours of various tasks that involve thinking.
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In other words, cognitive work results in chemical changes in the brain, which present behaviourally as fatigue. This, therefore, is a signal to stop working in order to restore balance to the brain.
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a neurometabolic point of view. They hypothesise that cognitive fatigue results from an accumulation of a certain chemical in the region of the brain underpinning control. That substance, glutamate, is an excitatory neurotransmitter
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Periodically, throughout the experiment, participants were asked to make decisions that could reveal their cognitive fatigue.
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The time it takes for the pupil to subsequently dilate reflects the amount of mental exerted. The pupil-dilation times of participants assigned hard tasks fell off significantly as the experiment progressed.
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During the experiment the scientists used a technique called magnetic-resonance spectroscopy to measure biochemical changes in the brain. In particular, they focused on the lateral prefrontal cortex, a region of the brain associated with cognitive control. If their hypothesis was to hold, there would be a measurable chemical difference between the brains of hard- and easy-task participants
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Their analysis indicated higher concentrations of glutamate in the synapses of a hard-task participant’s lateral prefrontal cortex. Thus showing cognitive fatigue is associated with increased glutamate in the prefrontal cortex
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There may well be ways to reduce the glutamate levels, and no doubt some researchers will now be looking at potions that might hack the brain in a way to artificially speed up its recovery from fatigue. Meanwhile, the best solution is the natural one: sleep