Cognitive Processing Mechanism Of Mental Rotation Under Simulated Weightlessness Condition

The physiological effects of the distribution to the head of blood and body fluids during the flight under weightlessness condition affect the brain function, which will decrease the performance of astronauts and do harm to flight safety. A good astronaut must have extraordinary spatial cognition ability. Mental rotation was first revealed in behavioral experiments, which refers to a type of spatial ability in which a person imagines how an object or array would appear if rotated away from the presented orientation. There are two types MR test. Stimuli of allocentric MR is images of two or three-dimensional graphics, letter like characters. Stimuli of egocentric MR is body parts like hands, feet, arms or legs.The results from many researches and our latest studies indicated that the changes of cognitive function of visual dorsal pathway caused by weightless physiological effect has its own self-adaptively, and the aging and the balanced characteristics reflect the internal neural mechanism of self-adaptive ability. Research shows that, head-down tilt(HDT)bed rest can effectively simulated the physiological effects of body fluid redistribution caused by microgravity, which is a good model for researchers to use. In this study, we intend to use head-down bed rest model to simulate physiological effects of weightlessness, and using behavior, electrophysiology techniques to compare the changes of visual dorsal cognitive functions before and after human short-term simulated weightlessness state. The results are useful to indicate the effect of weightless on cognitive function of visual dorsal pathway and its mechanism and to explore self-adaptive mechanism of brain cognitive function under weightless environment. The conclusion can provide theoretical and practical basis for the formulation of the tasks of China’s medium-and long-term manned space program and astronaut selection and training.Main results:Experiment One: Cognitive Processing Mechanism of Allocentric MR under Simulated Weightlessness Condition1. Behavioral results: 20 males participated in allocentric MR research 24.3±2.96 years old. 320 EEG files in all, and 316 are valid. The effective rate is over 98%. From Test Pre to day 8, the correct rates are 88%, 87%, and 86% for the rest few days. RA of stimuli and RT had significant linear relationship. From Test Pre to Test Post, the linear fitting intercept and slope of RT changing with RA are both no statistics difference, intercept F=1.028,p=0.418, slope F=13.000,p=0.076.2. ERP results: Main effect between RA and P300 amplitude is significant different, F=17.000,p<0.001, so is the latency, F=25.763, p<0.001.The amplitude and latency of RA 120?and RA180? are increase alone with HDT. The main effect between HDT time and P300 amplitude is no significant difference, F=1.200,p=0.057, so is the latency, F=1.670,p=0.110. The amplitude and latency shows in decrease-increase-decrease and increase pattern. In different RA, the mean of amplitude is first decrease and then increase in the first 3 days. HDT D2 is the lowest, and HDT D3 increase gently. There is no obvious changing pattern after HDT 3 days. Latency is decrease after HDT. Amplitude an latency didn’t recover to the original level after HDT test.3. ERD results: The allocentric MR task have evoked α ERD. The main effect between RA and ERD amplitude is not significant different, F=1.609,p=0.197, so is the latency, F=4.042,p=0.059.The main effect between HDT time and ERD amplitude is no significant difference, F=1.258,p=0.225, so is the latency, F=2.894,p=0.014.In different RA, ERD amplitude is highest in HDT D2, and HDT D3 decrease gently. There is no obvious changing pattern after HDT 3 days.4. s LORETA results: Use s LORETA analyze the source of P300. MR task activated Parietal Lobe(Precuneus, BA7), Frontal Lobe(Paracentral Lobule, BA5), Frontal Lobe(Postcentral Gyrus, BA4), Frontal Lobe(Paracentral Lobule, BA3), Limbic Lobe(Cingulate Gyrus, BA31), and Parietal Lobe(Sub-Gyral, BA40).Experiment Two: Cognitive Processing Mechanism of Egocentric MR under Simulated Weightlessness Condition1. Behavioral results: 20 males participated in egocentric MR research 24.3±2.96 years old. 320 EEG files in all, and 314 are valid. The effective rate is over 98%. From day 0 to day 8, the correct rates of TEST PRE is 93%, HDT D1, HDT D3 and HDT D5 are 91%, and 92% for the rest few days. RA and RT had significant linear relationship. From Test Pre to Test Post, the linear fitting intercept of RT changing with RA is statistics difference, intercept F=4.136,p=0.006, but slope is no statistics difference, F=2.025,p=0.095.2. ERP results: Main effect between RA and P300 amplitude is significant different, F=10.799,p <0.001, so is the latency, F=6.894, p<0.001.The amplitude is increase with RA. The main effect between HDT time and P300 amplitude is no significant difference, F=1.079,p=0.381, so is the latency, F=0.948,p=0.479. The amplitude an latency shows in decrease-increase-decrease and increase pattern. In different RA, the mean of amplitude is first decrease and then increase in the first 3 days. HDT D2 is the lowest, and HDT D3 increase gently. There is no obvious changing pattern after HDT 3 days. Latency is decrease after HDT. Amplitude an latency didn’t recover to the original level after HDT test.3. ERD results: The main effect between RA and ERD amplitude is not significant different, F=2.373,p=0.080, so is the latency, F=3.142,p=0.032.The main effect between HDT time and ERD amplitude is no significant difference, F=1.673,p=0.109, so is the latency, F=5.020,p=0.575.In different RA, ERD amplitude is highest in HDT D2,, and HDT D3 decrease gently. There is no obvious changing pattern after HDT 3 days.4. s LORETA results: The areas that MR task activated from near to fast are Frontal Lobe(Paracentral Lobule, BA5), Parietal Lobe(Precuneus, BA7) and Frontal Lobe(Medial Frontal Gyrus, BA6). Limbic Lobe(Cingulate Gyrus, BA31) has been active 7 times. The areas that active in 9 tests are alike. In HDT D2 and HDTD4, the active areas are different from other days: HDT D2 has active BA8, BA9, BA10, BA46 and BA 32. HDT D2 has active BA17, BA18, BA19, BA31 and BA 6.Conclusion:1. Simulated weightlessness doesn’t change the basic process of MR;2. Simulated weightlessness have the same effect on allocentric MR and egocentric MR.3. In allocentric MR tasks, the effect that microgravity on pictures of acute angle is not linear. The processing speed of obtuse angle picture is increases linearly, and the depth of processing is linearly decline. In upside down pictures, the processing speed and depth are non linear. In egocentric MR task, the processing speed and depth are non linear in 4 angles. The processing depth of normal pictures is linearly decline. The processing power of upside down pictures is increases linearly.4. Allocentric MR task have activated almost the same areas in parietal lobe with left hemisphere lateralization. MR ability has decrease during microgravity, then sensory system will activate as compensatory areas. Egocentric MR task have activated different areas, most in frontal lobe. MR ability has decrease during microgravity, then motor system will activate as compensatory areas. No obvious lateralization has been found.5. The effect of simulated weightlessness is internal neural mechanism of self-adaptive. In the first 3 days, MR ability change like “decrease-increase-decrease” pattern, just like letter “U”. The rest days have changed randomly. There are two explanations for this phenomenon: First, there are 3 stages when human body in simulated weightlessness condition. They are warning, resist and fatigue stage. After that, MR ability will change randomly according to individual’s self-adaptive ability. Another explanation is the effect of simulated weightlessness on human is periodicity. The first period is 3 days, in which period MR ability will change like “decrease- increasedecrease” pattern. The second period is 3 days or longer, in which period MR ability will go up and down.