轻、中度缺氧应激时亮度对比度对脑认知功能的影响

Effect of luminance contrast on brain event related potentials and reaction time during mild and moderate hypoxia

目的 选出轻、中度缺氧条件下最佳亮度对比度值。 方法 14名受试者在地面及15 0 0 m、3 0 0 0 m、5 0 0 0 m三个模拟高度 (吸低氧混合气体 )分别进行 5种不同亮度对比度 ( 8∶ 1、10∶ 1、12∶ 1、14∶ 1、16∶ 1)的视觉 Oddball测试 ,记录脑电图 ( EEG)及反应时 ,EEG经叠加平均处理提取出脑事件相关电位 ( ERP)中的 P3潜时。以 P3潜时和 RT为主要指标评定脑认知能力。采用两因素析因分析及统计学处理。 结果 在地面及 15 0 0 m,五个亮度对比度的视觉 Oddball任务的 P3潜时及 RT无明显差别 ;在 3 0 0 0 m、5 0 0 0 m,14∶ 1及 16∶ 1两个对比度的 P3潜时及 RT明显短于其它对比度的 P3潜时和RT,其中对比度为 14∶ 1时 P3潜时及 RT最短。 结论 在 3 0 0 0 m及 5 0 0 0 m高度中度缺氧条件下 ,对比度 14∶ 1为最佳亮度对比度 ,此时 P3潜时及 RT最短。缺氧会减慢脑信息加工过程。

Objective To draw the most suitable luminance contrast during mild and moderate hypoxia. Method Fourteen healthy and well trained students served as subjects. They were arranged to perform visual Oddball tasks under 5 different luminance contrasts(8∶1,10∶1, 12∶1, 14∶1, 16∶1) at 4 altitudes(ground, 1 500 m, 3 000 m, 5 000 m). IBM PC was used to display characters of different luminance. BM-5 luminance meter was used to measure luminance of displaying characters. The subjects breathed low oxygen mixture to simulate different altitudes. EEG data and reaction time were recorded, and P 3 waves of eventrelated potential(ERP) were extracted. P 3 latency and RT, the main indexes to measure the brain cognitive response speed in our study, were analyzed using a 2factor (contrast×altitude) analysis of variance. Results There were no significant differences among P 3 latencies and RTs during performing Oddball tasks under different luminance contrasts at ground level and 1 500 m altitude. While at 3 000 m and 5 000 m altitude, P 3 latencies and RTs under 14∶1 and 16∶1 contrasts were significantly shorter than those under other contrasts, and they were shortest under 14∶1. Conclusion The results show that during moderate hypoxia the most suitable contrast of visual display terminal (VDT) is 14∶1 when the luminance of the display is 20 cd/m2.