Science Daily August 11, 2022
Beyond subjective report, cognitive fatigue has been conceived as an inflated cost of cognitive control, objectified by more impulsive decisions. Researchers in France have proposed a neuro-metabolic account: the cost would relate to the necessity of recycling potentially toxic substances accumulated during cognitive control exertion. They validated this account using magnetic resonance spectroscopy (MRS) to monitor brain metabolites throughout an approximate workday, during which two groups of participants performed either high-demand or low-demand cognitive control tasks, interleaved with economic decisions. Choice-related fatigue markers were only present in the high-demand group, with a reduction of pupil dilation during decision-making and a preference shift toward short-delay and little-effort options. At the end of the day, high-demand cognitive work resulted in higher glutamate concentration and glutamate/glutamine diffusion in a cognitive control brain region, relative to low-demand cognitive work and to a reference brain region. According to the researchers, taken together with previous fMRI data, these results support a neuro-metabolic model in which glutamate accumulation triggers a regulation mechanism that makes cognitive control brain region activation more costly, explaining why cognitive control is harder to mobilize after a strenuous workday…read more. Open Access TECHNICAL ARTICLEÂ
Neuro-metabolic predictions. Credit: Current Biology, August 11, 2022Â