Influences of microgravity on human spatial orientation during six-month long-term spaceflight

As human space missions become longer in duration, astronauts are required to perform increasingly complex spatial operations involving spatial orientation and related cognitive processes. However, the cognitive consequences of long-term exposure to microgravity remain poorly understood, particularly because the role of gravitational cues in shaping spatial cognition is still debated. Therefore, we recruited participants aboard the China Space Station and terrestrial to perform a spatial orientation task involving egocentric and allocentric directional judgments during six months long-duration spaceflight. Tasks were repeatedly administered at multiple mission time points. We found that prolonged exposure to microgravity disrupts the 1G internal model of gravity. Upon initial adaptation to microgravity, the influence of the Earth-based internal gravity model diminished. By approximately 75 days into the mission, spatial orientation tasks aligned with the egocentric reference frame were performed more efficiently, as indicated by shorter response times. In contrast, tasks requiring misaligned or allocentric transformations showed increased response times in microgravity. In summary, these results emphasize the dynamic nature of the human spatial cognitive systems. • We examined how a six-month long-term space mission affects human spatial orientation using repeated cognitive assessments in orbit. • On Earth, spatial orientation is influenced by an internal model of gravity (IMG), which supports egocentric processing in vertical tasks. • Upon entering microgravity, the IMG effect is initially disrupted but gradually reconstructed through visual and bodily adaptation. • Over time, participants rely more on egocentric reference frames, but the reformed IMG remains less stable than under 1g conditions. • These findings reveal the dynamic and plastic nature of spatial cognition and highlight the critical role of gravity in structuring spatial reference frames.