Combined effects of moderate normobaric hypoxia and sleep restriction on visual and auditory integration

The ability of operators to integrate visual and auditory information places a high demand on their attention when monitoring instruments and systems. In this context, physiological constraints such as reduced oxygen levels alone or combined with restricted sleep are known to impair attention capacities. However, it is not known whether EEG markers of visual attention are affected differently from those of auditory attention in a situation combining both constraints. This study aimed to investigate the effects of prolonged moderate hypoxia exposure (4 h at fraction of inspired oxygen FiO₂ = 13.6%, ≃ 3500 m), sleep restriction (3 h of time-in-bed) and their combination on the evoked potential P300 and the alpha rhythm in 17 healthy participants. We first found that visually and auditory evoked P300 amplitude were reduced by sleep restriction and the combination of hypoxia plus sleep restriction, but not by hypoxia alone, reproducing previous findings regarding sleep restriction. We also found less efficient alpha event-related desynchronization (α-ERD) and alpha inter-trial phase coherence (α-ITPC) as it has already been observed during sleep restriction, while also providing novel insights into the effects of acute moderate and prolonged hypoxia exposure. Furthermore, our results confirm that certain neural aspects of visual and auditory attentional processes are differentially affected by hypoxia and sleep restriction, and also suggest that sleep restriction plays a primary role in driving the effects observed under combined constraints.