Feeling of saturation, of being unable to think or make a decision… Everyone has experienced mental fatigue, which can occur after intense and prolonged intellectual effort. Little by little, scientific work is lifting the veil on the mechanisms of this form of fatigue, which has been shown to reduce cognitive and physical performance.
In a study published in August 2022 in Current Biology, Mathias Pessiglione, neuroscientist at the Brain Institute (ICM, Paris), and his colleagues have thus demonstrated, thanks to healthy volunteers subjected to demanding cognitive tasks for more than six hours, an accumulation of a neurotransmitter, glutamate in the lateral prefrontal cortex (CPFL). The researchers hypothesize that mental fatigue corresponds to a difficulty in recruiting the executive control system, which relies on this region of the brain.
Using the same mental fatigue induction protocol, the ICM team is now seeking to develop a “fatigue decoder”, as part of a project funded by the National Research Agency (ANR). ” On the electroencephalogram (EEG), mental fatigue is reflected by an increase in low-frequency waves in the CPFL. The challenge now is to go from a sophisticated device with 128 electrodes to a portable and inexpensive EEG with sensors located above the CPFL “, explains Mathias Pessiglione.
In particular, he envisages an application in resistant depression, where mental fatigue is one of the most frequent symptoms and the least well relieved by conventional antidepressants. ” A fatigue decoder could help predict the effectiveness of treatments and personalize care “, he hopes.
The use of the smartphone in test
In Dijon, Romuald Lepers’ team (Inserm U1093, University of Burgundy) is studying more specifically the mental fatigue induced by prolonged use of the smartphone. As part of a project with ANR funding, these researchers recruited a population of students, and subjected them to three types of test for forty-five minutes: consulting social networks or playing video games on their phone. ; watching an emotionally neutral movie; perform a cognitively demanding task (Stroop test). Their mental fatigue was then measured subjectively, by visual analogue scales, then objectively, by an EEG (looking for slow alpha and theta waves) and behavioral tasks evaluating reaction time.
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