In this study, researchers conduct work employs 20 male subjects in a 7-day−6° head-down tilted (HDT) bed rest model to simulate physiological effects under weightlessness condition, and use behavioral, electrophysiological techniques to compare the changes of mental rotation ability (MR ability) before and after short-term simulated weightlessness state.

This variation of brain function will influence the performance of astronauts and therefore create possible harm to flight safety. Behavioral results suggested that significant linear relationship existed between the rotation angle of stimuli and the reaction time, which means mental rotation process do happen during the MR task in simulated weightlessness state.

In the first 3 days, the P300 component induced by object mental rotation followed the “down-up-down” pattern. In the following 4 days, it changed randomly. On HDT D2, the mean of the amplitude of the P300 was the lowest, while increased gently on HDT D3. There was no obvious changing pattern of the amplitude of P300 observed after 3 days of HDT.

Simulated weightlessness doesn't change the basic process of mental rotation. The effect of simulated weightlessness is neural mechanism of self-adaptation. MR ability didn't bounce back to the original level after HDT test. In the present study, 20 healthy males participated in a 7-day MR task under −6° HDT model.

Behavioral data shows that the accuracy at baseline was higher than HDT period and post HDT period. This finding indicated that simulated microgravity may have negative effects on people's MR ability. Linear regression analysis showed that RT is in significantly liner relationship with RA. As RT is prolonged along with the increasing RA, which is consistent with previous research, they may draw the conclusion that simulated microgravity hasn't changed the basic regularity of mental rotation.

The slope of the regression equation was related to the mental rotation speed according to the results of regression analysis with RA as an independent variable and reaction time as dependent variable. Despite that the difficulty of letter rotation differs in this study, research shows that the rotation speed of slope is not affected by the difficulty or ease of experimental materials.

In the period of pre-, during and post-HDT, the individual's mental rotation processing speed from high to low were HDT, HDT, D1, D2, HDT D3 HDT D7, Test the Pre, HDT D4, HDT D5, and Post bed rest. The rotation speed first increased and then decreased, and was slower than baseline after HDT.

In conclusion, the rest days it went into a state of random fluctuations. The time series of MR ability changes observed in the current HDT study could help us clarify the performance damage occurred in the early stage of spaceflight. As indicated by the current result, the first 3 days may be the critical period for performance maintain during spaceflight.