Overturn old theories!

Fatigue while performing demanding mental tasks may stem from a buildup of the neurotransmitter glutamate, according to a study published today (August 11) in Current Biology

Previous theories have suggested that people's fatigue due to mental exertion stems from the depletion of energy reserves

Mental fatigue also appears to shift decision-making toward a simple push-button mode, said study co-author Antonius Wiehler, a cognitive neuroscientist at the Motivation, Brain and Behavior Laboratory at the Paris Institute for Brain Research.

In their analysis, the researchers of the new study assessed two groups of people over a six-and-a-half hour period: a group of 24 performed a difficult, frequently changing cognitive task, while a group of 16 performed an easy task tasks that rarely change

The study also assessed changes in participants' decision-making throughout the day by asking the two groups to make economic choices on a regular basis

Glenn Wylie, a neuroscientist at the nonprofit Kessler Foundation in New Jersey who was not involved in the study, described the experiment as elegant

Apps also believes that boredom or depression may affect participants' assessments of their own level of fatigue

Wylie also pointed out that if glutamate severely hindered cognitive control, then you would expect that those participants with higher glutamate concentrations would have decreased performance, but this is not the case

While Wylie sees limitations to the study, he says such studies have important implications for patients with traumatic brain injury, ME/CFS, multiple sclerosis and other conditions that cause the brain to have to work harder