Astronauts’ brains change shape during spaceflight, according to a study published in Nature Microgravity in December 2016. MRIs of the brains of 26 astronauts taken before and after missions show that their brains compress and expand in space. The longer the astronaut spent in space, the more pronounced the changes were, the researchers said.

The University of Michigan researchers examined structural MRIs in 12 astronauts who spent two weeks as shuttle crew members, and 14 who spent six months on the International Space Station (ISS). All of them experienced increases and decreases in gray matter in different parts of the brain. But the more time the astronaut spent in space, the more pronounced the brain changes.

Rachael Seidler is professor of kinesiology and psychology at the University of Michigan. She said in a statement:

We found large regions of gray matter volume decreases, which could be related to redistribution of cerebrospinal fluid in space. Gravity is not available to pull fluids down in the body, resulting in so-called puffy face in space. This may result in a shift of brain position or compression.

The researchers also found increases in gray matter volume in regions that control leg movement and process sensory information from legs, which they say might reflect changes related to the brain learning how to move in microgravity. These changes were greater in Space Station astronauts because their brains were learning and adapting around the clock. Seidler said:

It’s interesting because even if you love something you won’t practice more than an hour a day. But the brain changes researchers observed were equivalent to someone practicing a new skill round-the-clock. In space, it’s an extreme example of neuroplasticity in the brain because you’re in a microgravity environment 24 hours a day.

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Bottom line: According to a University of Michigan study, astronauts’ brains change shape during spaceflight. MRIs taken before and after missions show that astronauts’ brains compress and expand in space.

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