Astronaut Brains Change Shape in Space

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Ohver the last half century of human spaceflight, scientists have learned a lot about how the human body responds once freed from the confines of Earth’s gravity. The vertebrae move away from each other, the bones lose their density, the muscles atrophy and fluids tend to migrate towards the head. But what about the brain?

According to a new study published today in PNASthe human brain moves and changes shape in space. Scientists came to this conclusion after studying MRI scans taken on 26 astronauts before and after spending time in microgravity. Overall, they found that astronauts’ brains moved backwards, upwards, and rotated backwards after spaceflight.

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Of course, detecting the movement of a gelatinous organ surrounded by liquid in microgravity doesn’t sound like brain surgery (or wizarding genius). The scientists therefore decided to go further, also studying changes in specific regions of the brain. Actually, this is where things got interesting. They found that different areas of the astronauts’ brains were moved more than others, and sometimes in a different direction than the brain as a whole.

Interestingly, the specific regions showing the largest shifts were those responsible for sensorimotor functions. In astronauts who spent more than a year in space, the supplementary motor cortex, that is, the part of the brain responsible for planning and coordinating movements, shifted upward more than other brain regions.

Some of these changes have also affected the capabilities of astronauts on Earth. Greater movements in the posterior insula, which processes bodily sensations, were associated with greater declines in balance after flight. Fortunately, these changes were not permanent: the astronauts’ brains recovered about six months after their feet returned to dry land.

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Main image: Yta23 / Shutterstock

• Jake Currie

  Published on January 12, 2026

  Jake Currie is a writer based in Brooklyn, New York.