A group of scientists has attempted to find out what is behind the feeling of being mentally exhausted and why it can really drain one's brain.
According to a survey published in Current Biology, glutamate - an excitatory amino acid that is present in over 90% of neuron-to-neuron communications in the human brain - should be blamed for the lack of mental endurance. It can even excite neurons to death, scientists warned.
During their experiment, the researchers monitored the brain chemistry of 24 participants who were tasked with completing computer-based sorting tasks for more than six hours.
The researchers found an increase in glutamate in the participants' lateral prefrontal cortex. Meanwhile, 16 other participants who were given easier tasks for the day didn't show signs of glutamate accumulation in this part of the brain.
The overabundance of glutamate in one's brain may result in a sensation that tasks are getting harder to focus on and complete.