Relationship between spontaneous EEG oscillations at 7 and 45 days of acute plateau exposure and the plateau acclimatization index

IntroductionThis study tracked 47 high-altitude migrants to investigate the adaptive mechanisms of the brain to hypoxic environments.MethodsEEG and physiological indicators (SpO2, HCT, AAI) were recorded during the acute (7 days) and chronic (45 days) phases of high-altitude exposure. EEG complexity was assessed using multiscale entropy (MSE), and inter-regional brain coupling was also analyzed.ResultsCompared with the chronic phase, EEG complexity in the frontal, parietal, and occipital lobes was higher in the acute phase, whereas inter-regional brain coupling was stronger in the chronic phase. SpO2 decreased during the acute phase and then slowly recovered; HCT continued to rise; AAI showed a decelerating downward trend. Correlation analysis revealed that SpO2 was negatively correlated with fine-scale MSE, and HCT was negatively correlated with medium- to coarse-scale MSE. AAI was correlated only with occipital MSE during the acute phase. During the chronic phase, AAI was negatively correlated with MSE coupling across multiple brain regions but not with MSE itself.DiscussionThese findings suggest that hypoxia may increase fine-scale complexity by enhancing local neural interconnections, whereas elevated HCT reduces long-range interactions between distributed neural populations. The brain exhibits a compensatory pattern of “complexity reduction with enhanced inter-regional coupling” during hypoxic adaptation, which may represent an optimization of neural efficiency under sustained hypoxia.