Network activation and its association with perceived stress underlie performance under stressful high demand.

This fMRI study examined the neural mechanisms underlying cognitive performance under stress, with a focus on individual differences in this capacity. Using an Ecological Multitasking under Stress (EMTS) paradigm, 50 healthy males performed a dual task combining executive function and flight navigation across five levels of task demand. The task was performed twice - with or without an additional stressor unrelated to task demand, consisting of social evaluation and aversive sirens. Subjective distress and autonomic measures were recorded throughout the task, confirming the effectiveness of the stress manipulation. Behavioral results showed that both stress and task demand significantly hampered performance accuracy and speed and increased subjective distress. Neural activation increased with task demand in the executive control network (ECN) and default mode network (DMN), whereas additional stress selectively increased activation in the salience network. Higher task demand across runs was also associated with enhanced ECN-DMN anticorrelation, indicating reduced functional integration between these networks. Notably, at the highest task-demand level under stress, perceived stress predicted performance decline and mediated the association between greater ECN activation and poorer executive performance. These findings further highlight a potential mechanism through which subjective distress may impair performance, whereby increased ECN engagement under conditions of high demand and stress may reflect inefficient cognitive control. This work may inform the development of brain-guided interventions to improve coping with high cognitive demands under stress.