[Effect of head-down bed rest on human EEG].

Objective. To study the influences of short-term simulated weightlessness on human EEG. Method. EEG of 12 male subjects (aged 18-22) was recorded, pre-HDBR (-6 degrees head down bed rest), mid-HDBR (3rd, 4th, 6th day) and post-HDBR (3rd day). Then these EEG recordings were analyzed by power spectral analysis. Result. During HDBR, peak frequency of EEG gradually slowed down (6th day, P<0.05). Alpha-band activities were enhanced (alpha1: P<0.001. Alpha2: 3rd and 6th day, P<0.05; 4th day, P<0.001) and reached maximum on the 4th day. Alpha1/alpha2 ascended (6th day, C3 and C4: p<0.02; F4, P4, T3, T4, T5: P<0.05). Theta-band activities enhanced (P<0.001), and reached maximum on the 3rd day at frontal regions, on the 4th day at parieto-occipital regions. Theta/alpha ascended obviously (6th day, P3, O1: P<0.05). Meanwhile, beta1, activities also enhanced (P<0.001), and reached maximum on the 3rd day at frontal regions. After HDBR, the index that recovered to the pre-HDBR level first was EEG peak frequency. Conclusion. HDBR caused obvious changes of EEG power spectrum characteristic. There exists a potential influence on brain function.

[Effects of simulated microgravity on the contents of monoamine transmitters in human plasma during heat stress].

AIM AND METHODS: Using high performance liquid chromatography-electrochemistry detection method to study the effects of simulated microgravity of a 7-day bed-rest in - 6 degrees head-down title (HDT) position, heat stress and their combination on the contents of monoamine transmitters in human plasma, the aim of the present study is to examine effects of simulated microgravity on the contents of monoamine transmitters during heat stress and to investigate the mechanism of human responses to heat stress in spaceflight. RESULTS: (1) The content of 5-HT, NE, E did not change significantly (P > 0.05) after simulated microgravity alone. (2) Exposed to heat stress alone, the content of 5-HT produced a marked decrease (P < 0.01) at > 40 degrees C, while the contents of NE, E had manifested increases (P < 0.01) at > or = 50 degrees C. (3) Under the effect of the combination of simulated microgravity and heat stress, compared with control group, there was a significant decrease in the content of 5-HT (P < 0.01), but NE, E did not change significantly (P > 0.05). Compared with heat stress alone, there was a significant decrease in the content of NE, E (P < 0.001), while 5-HT did not change significantly (P > 0.05). CONCLUSION: Simulated microgravity decreased the content of heat-induced NE, E, significantly, and the suppression probably plays an important role in degraded human response to heat stress in spaceflight.