Spaceflight takes a physical toll on astronauts, causing muscles to atrophy, bones to thin and bodily fluids to shift. According to a new study published in the journal PNAS, we can now add another major change to that list. Being in microgravity causes the brain to change shape.

Here on Earth, gravity helps to keep the brain anchored in place while the cerebrospinal fluid that surrounds it acts as a cushion. Scientists already knew that, without gravity’s steady pull, the brain moves upward, but this new research showed that it is also stretched and compressed in several areas.

Brains on the move Researchers led by Rachel Seidler at the University of Florida reached this conclusion after studying MRI scans of 26 astronauts taken before and after their missions to the International Space Station. These were compared with scans from 24 volunteers who participated in a head-down tilt bed rest experiment. They spent 60 days lying at a six-degree downward angle to mimic how weightlessness causes bodily fluids and organs to move toward the head.