Two paths to mental fatigue: Effects of cognitive underload and overload on mental fatigue and inhibitory control

Mental fatigue impairs inhibitory control, a key executive function involved in suppressing impulsive responses and resolving conflicts, which is critical for effective decision-making and behavioral regulation. Yet, subtle differences in inhibitory brain function arising from prolonged underload (non-adaptive, non-executive task) versus overload (adaptive, executive task) remain underexplored. Participants attended two laboratory sessions, each involving completion of a distinct fatigue-inducing task, preceded and followed by a set of computer-based ERP evaluation tests (Flanker and Go/No-Go tasks). Subjective ratings of workload, fatigue, sleepiness, and boredom were collected alongside electroencephalographic (EEG) and electrocardiographic (ECG) signals to capture psychophysiological markers of mental fatigue. Perceived fatigue increased similarly during underload and overload. However, underload induced greater sleepiness and boredom, whereas overload elicited higher perceived workload. Behavioral and psychophysiological analyses are ongoing. These findings are expected to advance understanding of how different cognitive demands modulate inhibitory function under fatigue and to inform strategies for mitigating fatigue-related performance impairments in both low- and high-demand environments.