A groundbreaking study reveals that astronauts’ brains can experience changes in shape and position during their time in space, presenting significant implications for NASA’s objectives of long-duration missions to the Moon and Mars.

Published on Monday in the Journal Proceedings of the National Academy of Sciences, the research indicates that astronauts’ brains tilted upward after spaceflight, deviating from their normal Earth position and shifting within their skulls. The study identified that areas associated with sensory functions, motion sickness, disorientation, and balance were notably affected.

This research contributes to the evolving field of aerospace medicine, which investigates the physical toll spaceflight and microgravity exert on the human body. Such insights are crucial for planning NASA’s ambitious projects to establish a base on the Moon and conduct crewed missions deeper into the solar system.

“Understanding these changes and their implications is vital for ensuring astronauts’ safety and health, as well as ensuring their longevity in space,” stated Rachel Seidler, a professor at the University of Florida and co-author of the study.

Seidler and her team examined MRI scans of 26 astronauts taken before and after their missions in orbit. The duration of spaceflight varied from a few weeks (for Space Shuttle missions) to about six months (the typical length for International Space Station missions). Some astronauts even spent a year aboard the station.

“Those who spent a year in space exhibited the most significant changes,” Seidler revealed. “We observed noticeable alterations even in astronauts who were in space for just two weeks, indicating that duration is a key factor.”

She added that among astronauts who remained in microgravity for over six months, the upward movement of their brains was “quite widespread,” particularly within the upper brain structures.

“The movement is in the range of a few millimeters. While this might not seem significant, in terms of brain dynamics, it truly is,” she noted.

Seidler pointed out that the observed brain changes often lead to “sensory conflicts” while astronauts are in space, resulting in temporary disorientation and motion sickness. Upon returning to Earth, such changes may also contribute to balance issues as astronauts readjust to the planet’s gravity. However, the study did not report any severe symptoms, like headaches or cognitive impairment, either during or after spaceflight.

“That was a surprise to me,” Seidler remarked.

For a comparative analysis, the research team also examined brain scans of 24 civilian participants who underwent bed rest for up to 60 days with their heads positioned at a 6-degree angle downward, mimicking microgravity conditions. Similar changes in brain position and shape were observed, yet astronauts’ brains displayed a more pronounced upward shift.

Dr. Mark Rosenberg, assistant professor of neurology and director of the Aerospace and Performance Neurology Program at the Medical University of South Carolina, emphasized that while the effects of spaceflight on the brain have been recognized, Seidler’s study is pioneering in documenting how these upward shifts impact astronauts both in space and upon their return to Earth.

“While we knew the brain shifted upward, we needed to explore any operational consequences,” said Rosenberg, who did not participate in the study. “This work helps clarify those relationships.”

The findings prompt additional questions for future studies, including whether brain changes differ between male and female astronauts and whether the age of crew members influences these changes. However, gathering a comprehensive dataset is challenged by the limited number of astronauts launched to the International Space Station each year, a demographic that has predominantly been male.

Further research is essential to establish whether the observed brain changes have long-term repercussions.

Currently, these changes do not appear to be permanent, similar to various physiological changes astronauts experience post-mission, such as bone density loss, muscle atrophy, and fluid redistribution. Once the body readjusts to Earth’s gravity, conditions largely normalize, Rosenberg explained.

However, it remains uncertain whether different gravitational environments might introduce new complications.

“If an astronaut were on Mars, which has one-third of Earth’s gravity, or on the Moon, with one-sixth of Earth’s gravity, how much longer would it take to return to normal?” Rosenberg queried.

Both he and Seidler assert that the current findings shouldn’t deter humans from spending extended periods in space. It is crucial, however, to comprehend any potential long-lasting damage and identify strategies to mitigate it.

“Whether we acknowledge it or not, we are destined to become a spacefaring species,” Rosenberg concluded. “It’s merely a matter of time. These are just some of the essential questions we need to address.”