Hyperbaric oxygen intervention enhances cooperative gains in high-trust people at high altitude: the role of medial prefrontal interbrain synchrony.

Successful cooperation requires efficient integration of self and other-related information. Whether hyperbaric oxygen intervention improves cooperative performance under high-altitude hypoxic conditions, and whether such effects depend on interpersonal neural coordination, remains unclear. In this randomized crossover study, 62 dyads completed a cooperative task under both hyperbaric oxygen intervention and high-altitude hypoxic conditions while undergoing functional near-infrared spectroscopy (fNIRS) hyperscanning. We examined whether hyperbaric oxygen intervention enhanced cooperative performance and whether this effect was associated with interpersonal trust and inter-brain synchrony (IBS). High-trust dyads exhibited greater hyperbaric-oxygen-related cooperation gains. Increases in medial prefrontal cortex (mPFC) IBS predicted improvements in cooperation success rate and cooperation efficiency, and both associations were moderated by interpersonal trust: positive associations were observed only in high-trust dyads. Pseudo-dyad analyses further indicated that this effect reflected real interpersonal interaction rather than shared task structure. These findings suggest that the cooperative benefits of hyperbaric oxygen intervention are not uniform but depend on interpersonal relationship quality. mPFC IBS may constitute an important neural correlate of hyperbaric-oxygen-related cooperation gains in high-trust dyads.