Going to space does more than change the way you look at the world — it also changes your brain.

In a new small study, published Oct. 24 as a Letter to the Editor in The New England Journal of Medicine, a team of researchers from Germany, Belgium and Russia detailed changes in the brains of 10 cosmonauts before and after long-term missions to space, finding "extensive" changes to the brain's white and gray matter.

What these changes mean for the cosmonauts is still an open question. "However, whether or not the extensive alterations shown in the gray and the white matter lead to any changes in cognition remains unclear at present," study co-author Dr. Peter zu Eulenburg, a neurologist and professor of neuroimaging at Ludwig-Maximilians-Univeristat München in Germany, said in a statement.

What's more, the researchers found that the circulation of cerebrospinal fluid — the clear liquid that cushions the brain and spinal cord — remained altered long after spaceflight. [7 Everyday Things That Happen Strangely in Space]

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"Taken together, our results point to prolonged changes in the pattern of cerebrospinal fluid circulation over a period of at least seven months following the return to Earth," zu Eulenburg said.

Before and after

To study the brain changes, the researchers looked at MRI scans of the cosmonauts' brains taken before spaceflight, shortly after (nine days, on average) returning from spaceflight and about seven months after spaceflight. All 10 cosmonauts participated in the first two brain scans; seven participated in the final scan.

The cosmonauts were all men with average age of 44 who traveled to the International Space Station. On average, they spent 189 days, or about six months, in space.

The researchers focused on three variables in the brain scans: gray matter volume, white matter volume and cerebrospinal fluid volume. Gray matter, which makes up the outer surface of the brain, contains the cell bodies of neurons and other support cells, while white matter contains the axons, the long branches that connect neurons.

Compared with gray matter volume pre-spaceflight, the researchers found "widespread" reduction in gray matter volume upon examination when the cosmonauts returned. However, at the long-term postflight follow-up, the researchers reported most of the reductions in gray matter volume had recovered toward preflight levels; in other words, these weren't lasting changes.

White matter was a different story: Compared with measurements before the cosmonauts' space travel, white matter volume decreased in one part of the brain. But when the seven cosmonauts returned for a follow-up scan seven months later, white matter volumes had decreased even more.

Cerebrospinal fluid volumes also changed after the cosmonauts' missions. On the first postflight brain scan, the CSF volume was increased in some areas and decreased in others relative to preflight levels. By the later scan, however, the CSF volume in the center of brain had returned to preflight levels, while the fluid in space between the brain and the skull had increased further.

Originally published on Live Science.