Ongoing EEG oscillatory dynamics suggesting evolution of mental fatigue in a color-word matching stroop task

Mental fatigue would develop when performing a tedious cognitive task for a long time. The present study evaluated the evolution of mental fatigue in a Stroop task using electroencephalography (EEG) with independent component analysis (ICA) method. Specifically, two aspects of mental fatigue, i.e., mental effort and mental engagement, were tracked by the ongoing oscillatory dynamics from frontal independent component (IC) related to cognitive control and posterior ICs related to attention. While behavioral data, i.e., number of errors and response times, indicated complicated patterns along the time, increasing patterns were consistently observed in the theta band activity of the frontal IC and in the alpha band activity of the posterior ICs as the time on task. These patterns are indicative of a gradual impairment of mental effort and mental engagement (or sustained attention), which can be explained by the evolution of mental fatigue. The present results demonstrate that ongoing EEG obtained from ICA is a sensitive and reliable mean to measure mental fatigue.