A study on the effects of virtual high-altitude exposure on brain function activity in people with different severity of fear of heights.

Introduction: The electroencephalography (EEG) microstate method has been extensively used to investigate brain function activity in patients with mental disorders. However, previous studies mainly focused on the analysis of basic microstate features. In this study, we aimed to explore brain electrical activities of individuals with different severity of fear of heights (FoH) during virtual high-altitude exposure using power spectrum and functional brain network based on microstate EEG. Methods: First, 69 male participants were included and classified into one of three degrees of FoH (i.e., no-FoH, mild or moderate FoH (m-FoH) and severe FoH (s-FoH)) according to their acrophobia questionnaire (AQ) scores. Then, 32-channel EEG signals were recorded from each subject during virtual high-altitude exposure. Subsequently, microstate EEG signals and corresponding microstate time windows for all subjects were obtained by the microstate analysis. Finally, the Welch method and weighted phase lag index were applied to these signals to compute microstate power spectrum features and brain network properties, and these measures were compared among three groups. Results: The results showed that the s-FoH group had significantly higher relative delta power than the no-FoH group for microstates B and F, and than the m-FoH group for microstates B, C and F. In constrast, the s-FoH group had lower relative alpha power than no-FoH group for microstates B, D and F, and than m-FoH group for microstates D and F. These differences were observed in multiple brain regions, mainly including the frontal and frontal-central areas. The s-FoH group also exhibited a significantly larger power ratio theta/alpha in the frontal-central region for microstates B, C, D and F compared to the no-FoH group, and in the central region for microstate D relative to the m-FoH group. Moreover, these features of microstate power spectrum with significant differences between different FoH groups significantly associated with the scores of AQ. For microstate functional brain network, prominently increased clustering coefficient and local efficiency were observed in both the m-FoH and s-FoH (i.e. FoH) groups for microstate F compared to the no-FoH group. It was also found that FoH individuals have significantly reduced robustness of microstate brain network F. Regarding degree distribution, the FoH groups exhibited power law distributions in microstate brain network A, whereas the no-FoH group displayed exponentially truncated power law patterns, which was opposite for microstate D. Discussion: In summary, our findings revealed the disrupted power spectrum and functional brain network in individuals with FoH during virtual high-altitude exposure from the perspective of microstate EEG, which may advance our understanding of the neuropathology of fear of heights and provide a novel electrophysiological tool for its clinical assessment. However, to control the influence of gender and age on fear responses and EEG dynamics, only young male participants in their early twenties were recruited. Therefore, the present findings should be interpreted with caution, and their generalizability to female populations and older adults remains to be verified.