Effects of long-term exposure to high altitudes on perceptual closure

Objective:To investigate the neural mechanism of long-term exposure to high altitudes environment on the processing stage of perceptual closure.Methods:A cross-sectional study was conducted. Thirty college students who first entered the plateau area (at an altitude of 3 658 m) and had lived in high-altitude areas for two years were selected as high altitude group (HA group), and 29 college students matched in age, gender and education level who had never been to the plateau area were selected as sea level group (SL group). The differences of basic physiological parameters were compared between the two groups.The face pairwise comparison paradigm was applied in the subjects of the two groups and the differences between the two groups were compared by event-related potentials (ERPs) technology. SPSS 22.0 software was used for statistical analysis, and the mean ± standard deviation was used for statistical description. Independent sample t test was used for comparison of physiological data between the two groups, and repeated measurement variance analysis was used for ERP data. Results:The physiological results revealed that the HA group had a higher pulse rate((86.71±10.82)/min, (75.97±11.28)/min ; t=-3.19, P=0.002) and diastolic blood pressure than the SL group ((75.93±9.19)mmHg, ( 68.59±11.42) mmHg ; t=-3.20, P=0.002). The oxygen saturation level was significantly lower than that of SL group ((90.77±2.25)%, (98.31±1.56) %) ; t=14.00, P<0.001). In the face pairwise comparison paradigm test, the main effect of P1 latency of ERP was significant.Compared with SL group, HA group showed significantly shortened latency of P1 ((105.10±15.59) ms, (128.35±14.40)ms, P<0.001). The main effect of group of N170 amplitude was significant, HA group was larger than that of SL group((-7.57±3.83) μV, ( -5.11±3.26) μV, P=0.005). The interaction effect between group and hemisphere of NCL amplitude was significant ( F(1, 57)=9.72, P=0.003). Simple effect test showed that the amplitude on the right hemisphere of SL group was significantly larger than that on the left hemisphere((0.46±1.31) μV), (1.16±1.33) μV ). The latency of P1 was significantly correlated with heart rate( r=-0.46, P<0.01), oxygen saturation level( r=0.64, P<0.01) and diastolic blood pressure( r=-0.26, P=0.049). Conclusion:After long-term exposure to high altitude, the neural response related to early visual perception is faster. More psychological resources are recruited during the face structural encoding stage. Contra-lateral compensating effect appeares in the stage of perceptual closure.