Prefrontal activation and attentional bias under different levels of perceived military stress: An fNIRS study

Military personnel deployed above 2500 m face both professional and environmental stressors that can impair mental health and cognition, risking overall performance. This study explores how chronic stress levels affect attentional bias and prefrontal activation in this population.

104 Chinese plateau-area military personnel were categorized into high- or low-stress groups based on self-reported psychological stress. They completed a dot-probe task while monitored with functional near-infrared spectroscopy (fNIRS).

The results showed that the high-stress group exhibited greater self-reported attention bias (both negative and positive) compared to the low-stress group. Reaction times were longer in than positive conditions. Critically, fNIRS results revealed robust group-dependent differences in prefrontal activation patterns across multiple regions, including the VLPFC, FPC, and OFC, with significant interactions involving affect, congruence, and hemispheric position. Importantly, regression analyses further demonstrated that stress levels continuously predicted both behavioral and neural responses. Higher stress was associated with longer reaction times in positive congruent trials, as well as increased HbO₂ responses in the FPC. In addition, stress levels positively predicted activation in the left DLPFC and VLPFC during negative congruent trials, and in the left FPC and right OFC during positive incongruent trials.

Chronic stress is associated with systematic and scalable alterations in prefrontal activation during attentional processing, reflecting both group-level differences and continuous modulation by stress severity. These findings highlight that stress-related cognitive vulnerability is better captured at the neural level and varies as a function of emotional valence and task demands.