Functional Near-Infrared Spectroscopy Brain Network Dynamics Reveal Cognitive Function Variability During Acute High-Altitude Exposure

Abstract After acute exposure to high altitude (HA), the mechanism underlying hemodynamics-related cerebral function remains unclear and comprehensive and systematic studies are lacking. In this paper, functional near-infrared spectroscopy (fNIRS) was used to characterize cerebral activation and brain network dynamics during acute exposure to HA. Thirty healthy volunteers were recruited and divided equally into two groups, the HA group and the low-altitude (LA) control group, to perform a resting-state experiment. The amplitude of low-frequency fluctuation (ALFF, 0.09-0.8 Hz) and signal complexity were calculated to evaluate spontaneous neural activity. Moreover, the small-world networks were established to describe the corresponding brain network dynamics. Compared with the LA control group, the ALFF values of the HA group in the left middle frontal gyrus (L-MFG), left inferior frontal gyrus (L-IFG) and right inferior frontal gyrus (R-IFG) were significantly decreased $$\:\left(p<0.05\right).$$ Meanwhile, the HA group's signal complexity was significantly higher than that of the LA control group in the L-MFG, left superior frontal gyrus (L-SFG) and right superior frontal gyrus (R-SFG). This pattern can be described as higher chaotic complexity with lower fluctuation amplitude in spontaneous brain activity. Brain network results indicated altered brain network patterns in the prefrontal cortex with significantly reduced efficiency and increased randomness. During acute exposure to HA, abnormal changes in hemodynamics-related cerebral function were confirmed, which can potentially reveal the neurodynamic mechanisms underlying physiological responses to HA. These findings may contribute to a further understanding of abnormal neural function during acute exposure to HA.