MRI Study Shows Spaceflight Physically Changes Astronauts’ Brains

Scientists know that extended periods of time spent in space can have effects on the human body, caused by altered vestibular inputs and lack of gravity. But what happens to your brain in space?

A new study from University of Michigan researchers used MRI scans to examine how astronauts’ brains compress and expand in spaceflight. The findings could have implications for treating other health conditions that affect brain function.

The retrospective follow-up study is believed to be the first to examine structural changes during spaceflight. Results show that the volume of gray matter increased or decreased, and the extent of the alteration depended on the length of time spent in space.

Gray Matter Alterations

Researchers looked at structural MRIs in 12 astronauts who spent two weeks as shuttle crew members, and 14 who spent six months on the International Space Station. All experienced increases and decreases in gray matter in different parts of the brain.

brain changes with long duration bed rest

The top row shows brain changes with long duration bed rest; the bottom row shows brain changes with spaceflight. Orange shows regions of increase; blue = decrease. There is some overlap but also notable differences with spaceflight showing more changes in the cerebellum, a structure that is involved in motor learning. Credit: U. Michigan

The longer the astronaut spent in space, the more pronounced the changes were. Rachael Seidler, professor of kinesiology and psychology at the University of Michigan, said:

“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.”

Possibly reflecting changes related to the brain learning how to move in microgravity, researchers also found increases in gray matter volume in regions that control leg movement and process sensory information from legs  (precentral gyrus, postcentral gyrus, the posterior cingulate gyrus, and precuneus cortex). These changes were greater in space station astronauts because their brains were learning and adapting around the clock.

“It’s interesting because even if you love something you won’t practice more than an hour a day,” Seidler says. 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.”

Extreme Neuroplasticity

Though they haven’t pinpointed the exact nature of the changes, the findings may lead to new ways of thinking about certain health conditions.

For example, people on long-duration bed rest or people who have normal pressure hydrocephalus, a condition in which cerebrospinal spinal fluid accumulates in ventricles in the brain and causes pressure.

gray matter volume changes

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. Credit: U. Michigan

The brain changes could reflect new connections between neurons, says Seidler, who is leading another long-term study that will help determine the repercussions on cognition and physical performance, as well as how long the brain changes last.

For example, even after balance returns, the brain might still recruit different pathways to compensate for the structural brain changes caused by spaceflight.

“The behavior may return to normal, but the way the brain controls the behavior may change,” she says.

The study was funded by a grant from the National Aeronautics and Space Administration (NASA).

Vincent Koppelmans, Jacob J Bloomberg, Ajitkumar P Mulavara & Rachael D Seidler
Brain structural plasticity with spaceflight
npj Microgravity 2, Article number: 2 (2016) doi:10.1038/s41526-016-0001-9

Top Image: Kate Whitley, Wellcome Images