Methods
Participants
A total of 23 students who came from an aid education team of Xiamen
University (Fujian province, China P.R.) were recruited as paid
volunteers. Five participants were removed due to noisy EEG data and
drug use, which affected the central nervous system. Thus, the final
sample consisted of 18 individuals (5 males, mean ± SD age: 19.15 ± 0.99
years). According to the self-report, all participants had normal or
corrected-to-normal vision and were right-handed. None of them had any
history of alcohol consumption, neurological or psychiatric diseases,
hypertension, heart disease, lung disease or chronic altitude sickness.
None of the participants had been to HA areas before, except for two
team leaders who went to HA for a short stay one year ago. Oxygen supply
equipment was not used throughout the study period. Informed consent was
obtained from all the participants prior to the experiment.
Stimulus
Sixty natural neutral facial pictures were quoted from the Chinese
Standard Emotional Face Picture System . Half of them were male, and
half were female. Adobe Photoshop was used to randomly occlude pictures,
with an occlusion ratio of 50% for each picture, which makes the
perceptual process more difficult. The picture pixel resolution is
260×300 (width× height). Each stimulus appeared in the center of the
17-inch LCD computer screen (resolution 1024×768 pixels, refresh rate 75
Hz).