From ancient mythology of ‘goddess Chang flying to the moon’ to ‘Star Trek’, humans have always dreamed of living in space, and even immigrate to a new planet. However, to achieve this dream, humans not only need to master more advanced aerospace and space technology, but also to be able to cope with risks and uncertainties during long-duration spaceflight. Long-duration space missions pose unique challenges and unexpected risks, and a successful space mission requires effective risk management. Take the ‘interactive docking’ as an example, the risk of this decision task is very high: the consequences of failure could be just crashing interactive docking device or causing ‘boat crash’. However, currently very few researchers have explored the risk behavior of astronauts that are exposed to weightlessness conditions.

Numerous studies have investigated whether physiological and psychological changes are affected during real spaceflight or simulated microgravity. Surprisingly, few studies have investigated astronauts’ risk-taking behavior. As a high-level cognitive function, risky decision making plays an important role in the activities of individuals in an uncertain and isolated environment during exposure to weightlessness or simulated weightlessness. Furthermore, to understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on the functional architecture of the brain. On the one hand, the neural basis of microgravity effects on risk taking can be found based on the task-related fMRI research. On the other hand, because resting-state brain activity can predict the brain activities evoked by a variety of cognitive tasks, exploring the effects of microgravity on the intrinsic functional architecture of the brain may provide valuable insight into the neural mechanisms underlying the physiological and psychological changes that occur in microgravity.

To investigate the effects of simulated microgravity on individuals’ risky decision making and brain activity, Prof. LI Shu’s research team from the Institute of Psychology, CAS, conducted a study in collaboration with the team from the Chinese Astronaut Research and Training Center. Sixteen healthy adult males aged between 20 and 34 (M ± SD, 26.6 ± 4.2), participated in the study. Researchers collected both behavioral and fMRI data when participants performed a Balloon Analogue Risk Task (BART), and fMRI data during rest in which the participants just closed their eyes and had a rest. They performed all daily activities lying down and were not permitted to leave their beds (Fig1). The experiment consisted of three stages: a 10-day baseline control period, a 45-day head-down tilt (HDT) bed rest period, and a 10-15-day post-HDT ambulatory recovery period. For the BART behavioral experiment, eight tests were scheduled for each participant, one in the 7th day before bed rest, six in the 7th, 14th 21st, 28th, 35th, 41st day during the bed rest and one in the 7th day after bed rest. For the fMRI experiment, two tests were conducted, one in the 8th day before bed rest and one in the 3rd day after bed rest.

Fig1.The participant was doing the experiment.

The results showed that participants’ risk-taking behavior was not affected by bed rest. However, Prof. LI Shu’s research team found that the ventromedial prefrontal cortex (VMPFC) showed less deactivation after bed rest (Fig2) and that the VMPFC activation in the active choice conditions showed no significant difference between the win outcome and the loss outcome after bed rest, although its activation was significantly greater in the win outcome than in the loss outcome before bed rest. Because the VMPFC was reported to be involved in value calculation in risk decision making, these results suggested that microgravity has effect on individual higher-level cognitive functioning and the participants showed a decreased level of value calculation after the bed rest. Resting-state functional MRI showed decreased degree centrality (DC) in two regions, the left anterior insula (aINS) and the anterior part of the middle cingulate cortex (MCC) in the male volunteers after 45 days bed rest (Fig3). Furthermore, seed-based resting-state functional connectivity analyses revealed that a functional network anchored in the aINS and MCC was particularly influenced by simulated microgravity. These results provide evidence that simulated microgravity alters the resting-state functional architecture of the brains of males and suggest that the processing of salience information, which is primarily subserved by the aINS–MCC functional network, is particularly influenced by spaceflight.

Fig2. The deactivation of VMPFC decreased after the bed rest.