Figure 1. Schematic illustration of the time and altitude of data collection.
Before the EEG recording, HR and SpO2 were measured with a finger clamp pulse oximeter (model DEDAKJ-CMS50D) at rest, vital capacity (VC) was assessed by a digital vital capacity tester (WQS-8888), and an Omron sphygmomanometer (model HEM -7124) was applied to detect resting blood pressure (systolic pressure, SBP and diastolic pressure, DBP).
The EEG experiment lasted approximately fifteen minutes. Participants were seated in a comfortable chair approximately 70 cm in front of the screen in a dimly lit cabin, which subtended 4.8°×6° of visual angle. The facial S1-S2 paradigm was adopted in this study. During the test, 120 trials were randomly presented, and 18 practice trials were used to ensure that all the participants understood the experiment. Two face photographs (S1 is an incomplete face, S2 is an complete face) were presented in order in each trial. All photographs were black and white and keep the same luminance. The probability that S1 and S2 are the same face is 50%. If S1 and S2 are identical, it is the congruent condition; otherwise, it is the incongruent condition (Figure 2). The stimuli were presented by E-Prime 2.0 (Psychology Software Tools, Pittsburgh, PA). Each stimulus was presented 500 ms on the screen and followed by a blank screen with a “+” in the center. Participants need to figure out whether S1 and S2 are the same face and respond by pressing “F” or “J” on the keyboard. The ISI (interstimulus interval) was 800 ms, and the ITI (intertrial interval) was randomly varied from 800 to 1200 ms.