Effects of sustained cognitive load on behavior and event-related potentials in perceptual decision-making

Perceptual decision-making involves interpreting external stimuli and selecting the most appropriate response. Success depends on cognitive control, which includes processes like attention, working-memory, and inhibitory control regulated by differential responses of fronto-parietal networks. However, the effects on behavior and neural activity of mental fatigue induced by sustained cognitive control are still unclear. Here we show that sustained cognitive load alters cortical dynamics, leading to faster, automatic responses and hence to an increased error rate. We acquired continuous hd-EEG data from 64 scalp electrodes in 25 young adults during a go/no-go task, comparing it to a duration-matched control session without cognitive exertion. Event-related potentials (ERPs) and spectral features related to errors were observed in both frontal and posterior parietal areas, confirming the fundamental role of these regions in cognitive control and decision-making. Conversely, the experimental control condition was associated with increasingly slow reaction times. The ERP and behavioral analysis suggested that this was likely due to a decrease in task engagement. Our results showed that cognitive load can lead to a change in the subjects' behavioral strategy, opting for a more impulsive responses but with an increased likelihood of errors. Moreover, we observed several ERP components indicative of individuals’ ability to exert adequate control over their actions. This study sheds light on the brain functional mechanisms underlying behavioral errors in response selection emerging under conditions of mental fatigue induced by the extended exertion of cognitive control.