Effects Of Different Luminance Contrasts And Sound Intensities On Brain Perceptual Function During Exposure To Mild And Moderate Hypoxia

Graduate: Qin Yun Supervisor : Professor Ma RuishanTutors : Senior Engineer Ni Keying Lecturer Cheng Hongwei AbstractAcute hypoxia influences brain function mostly through visual and auditory passage. This influence is showed out by delay of P300 latency and reaction time (RT). Today as the wide use of computer on plane, how to elevate the brain function during flight in the condition of computer as a visual display terminal has become more and more important. So studying the effects of different luminance contrasts on brain function is valuable. On the other hand because most information is passed through visual passage, visual workload is too heavy to avoid accidents. In this case auditory passage causes more notice, because it is another important information access to brain. Studying its efficiency during flight in mild hypoxia also values. In the end, it hasn't come to a conclusion when brain function begins to decline during acute hypoxia. Additive Factors Method was used in this experiment to find out when brain function begins to decline during acute hypoxia.The main objects of this experiment were: 1) To get the most suitable luminance contrasts in mild and moderate hypoxia. 2) To get the most suitable sound intensities in mild and moderate hypoxia. 3) To find out when the brain function begins to decline during acute hypoxia.14 healthy young men were chosen for the experiment. They were asked to do visual oddball tasks with 5 different luminance contrasts (8:1, 10:1, 12:1, 14:1, 16:1) and auditory oddball tasks with 5 different sound intensities (55> 60> 70> 80^ 85dB). The primary luminance of the screenwas 20cd/m2 and the environment noise was 30dB. The altitudes, the luminance contrasts and the sound intensities were randomized. The experiment was divided into two parts. Visual oddball task was the first part and auditory task was second. During the experiment the P300 latency and RT were recorded. At the same time blood oxygen saturation (SaO2) , respire rate and the subjective feeling were recorded too. At last the data were analyzed.The main conclusions of the experiment were below :1. At 3 000m and 5 000m when the luminance of the display was 20cd/m2 and the contrast was 14:1, P300 latency and RT were shortest compared with other contrasts. There were significant differences of P300 latency and RT at different altitudes. The results showed that in moderate hypoxia stress when the luminance of the display was 20cd/m2 the most suitable contrast of visual display terminal (VDT) was 14:1.2. At ground and 1 500m when sound intensities were 60,70,80,85dB, P300 latency and RT were significantly shorter compared with 55dB. But there were no significant differences of P300 latency and RT among them. At 3 000m and 5 000m when sound intensities were 70, 80, 85dB , P300 latency and RT were significantly shorter compared with the other two's while significant distinctions among theirs were not found .According to subject feelings sound intensities above 80dB were unbearable. So the most suitable sound intensity for ground and light hypoxia was 60~70dB;while for moderate hypoxia it might be 70~80dB.3. Interaction between hypoxia and stimulus intensity was found for P300 latency and RT. Acute hypoxia influenced the preprocessing stage of information processing.