Astronauts’ brains change shape and position in space: study

Astronauts’ brains can change shape and change position during their time in space, according to a new study with implications for NASA’s goals of conducting long-duration missions to the Moon and Mars.

The study, published Monday in the journal Proceedings of the National Academy of Sciences, found that after spaceflight, astronauts’ brains were tilted upward and moved up and down in the skull compared to their normal position on Earth. Affected areas of the brain included sensory regions linked to motion sickness, disorientation and loss of balance, the scientists found.

The research adds to a growing but still nascent field of aerospace medicine focused on the detrimental consequences of spaceflight and the microgravity environment on the human body. Such research is crucial for planning long-term missions, as NASA seeks to build a base on the Moon and send astronauts deeper into the solar system.

“We need to understand these changes and their impacts to ensure the safety and health of astronauts and protect their longevity,” said Rachael Seidler, a professor in the department of applied physiology and kinesiology at the University of Florida and co-author of the study.

Seidler and his colleagues analyzed MRI scans of 26 astronauts before and after their time in orbit. The time participants spent in space ranged from a few weeks (for Space Shuttle flights) to about six months – the standard length of missions aboard the International Space Station. A few people studied spent extended stays of a year at the space station.

“The people who went for a year showed the biggest changes,” Seidler said. “There were still obvious changes in people who went for two weeks, but the duration seemed to be the determining factor.”

She added that among astronauts who stayed in space six months or more, upward motion was “quite extensive,” particularly in structures at the top of the brain.

“It’s on the order of a few millimeters,” she said, “which doesn’t seem like a big number, but when you’re talking about brain movement, it really is. That kind of change is visible to the naked eye.”

Seidler said the observed brain changes sometimes caused “sensory conflicts” for astronauts in space, manifesting as temporary disorientation or motion sickness. Back on Earth, these changes can also contribute to balance problems as astronauts readjust to Earth’s gravity. But she said the study did not detect serious symptoms, such as headaches or cognitive impairment, during or after spaceflight.

“It surprised me,” Seidler said.

For comparison, the research team also analyzed brain scans of 24 civilian participants on Earth who were bedridden for 60 days while tilted back, so their heads were 6 degrees below their feet. The idea was to simulate a microgravity environment, and the scientists found similar changes in the position and shape of the brain after the period of bed rest. The astronauts’ brains, however, experienced a greater upward shift.

Dr. Mark Rosenberg, assistant professor of neurology at the Medical University of South Carolina and director of its Aerospace and Performance Neurology Program, said scientists know that spaceflight can affect the brain, but Seidler’s study is one of the first to document how these bottom-up changes influence how astronauts function in space and on Earth.

“We knew the brain moved upward, but does that really have an operational impact? said Rosenberg, who was not involved in the study. “This study is able to establish some of these associations.”

The findings raise new questions for potential follow-up, such as whether there are differences in brain changes between male and female astronauts, and whether a crew member’s age is a factor. However, painting a complete picture is limited by a sample size problem: Only about a dozen astronauts launch to the International Space Station each year, and NASA’s astronaut corps has always been dominated by men.

Further research is also needed to understand whether the observed brain changes have longer-term impacts.

So far, like most other changes to astronauts’ bodies after time in space – including bone loss, deterioration of muscle strength and fluid redistribution – these changes do not appear to be permanent. Once the body readjusts to the familiar effect of Earth’s gravity, things return more or less to normal, Rosenberg said.

But it is not yet clear whether different gravitational environments will lead to new complications.

“If you’ve been on Mars with one-third of Earth’s gravity, or on the Moon with one-sixth of Earth’s gravity, will it take three or six times as long to get back to normal?” Rosenberg said.

He and Seidler both said the results so far should not be seen as an argument against humans spending long periods of time in space. But it will be essential to determine whether there is lasting damage and how to avoid it, if possible.

“Whether we want to admit it or not, we will eventually become a space-faring species,” Rosenberg said. “It’s only a matter of time. And these are just some of the unanswered questions we need to resolve.”