The International Space Station (ISS), photographed by an astronaut aboard the space shuttle Endeavour on Feb. 10, 2010. Astronauts who flew on ISS and space shuttle missions experienced changes in brain volume, a new study has found.

NASA

It appears that spaceflight really goes to astronauts heads.

Doctors and scientists have long known that exposure to a weightless environment causes muscles to atrophy, bones to weaken andvision to deteriorate, among other effects. Now, a new study has determined that spaceflight also causes some parts of the brain to expand and others to contract. [The Human Body in Space: 6 Wild Facts]

We found large regions of gray-matter volume decreases, which could be related to redistribution of cerebrospinal fluid in space, study principal investigator Rachael Seidler, a professor of kinesiology and psychology at the University of Michigan,said in a statement.

Gravity is not available to pull fluids down in the body, resulting in so-called puffy face in space, Seidler added. This may result in a shift of brain position or compression.

Seidler and her team studied magnetic resonance imaging (MRI) scans of 26 astronauts -- 12 who flew on two-week-long space shuttle missions, and 14 others who lived aboard the International Space Station (ISS) for five to six months.

These MRI scans are the first images ever to show how spaceflight changes brain structure in humans. Blue shows areas of gray-matter volume decrease, likely reflecting shifting of cerebrospinal fluid. Orange shows regions of gray-matter volume increase, in the regions that control movement of the legs.

Koppelmans et al./Nature Microgravity

The brains of all 26 astronauts changed shape as a result of their off-Earth stints, and the magnitude of these changes was greater in the ISS crewmembers.

The brain regions that expanded are associated with the control of leg movement and the processing of sensory information from the lower body, team members said. Therefore, the MRIs are likely capturing the brain learning a new skill -- how to move inmicrogravity-- and doing so around the clock, Seidler said.

Its interesting, because even if you love something, you wont practice more than an hour a day, she said. In space, its an extreme example of neuroplasticity in the brain, because youre in a microgravity environment 24 hours a day.

Its unclear how long these changes last after astronauts come back to Earth, or how the shifts may affect cognitive ability, the researchers said. Seidler and her team are currently conducting another long-term study to look into these questions.

The new study was published in December 2016 in the journalNature Microgravity. The lead author is Vincent Koppelmans, of the University of Michigans School of Kinesiology.

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