Astronauts often talk about the overview effect, the cognitive shift that makes you realize the fragility of our world once you see it among the interplanetary void. But space travelers experience more than just psychological changes. There are neurological changes too. Their brains are changed by being in space.
New research, published in Scientific Reports, looked at MRI scans of 15 astronauts before their extended sojourn in space, immediately as they returned, then after one month, three months, and six months. They were compared to 16 non-astronauts that acted as a control sample.
The analysis showed that astronauts experience increases in perivascular spaces – the regions in the brain that surrounds blood vessels where cerebrospinal fluid flows – after long-duration space flights. While that was a major change, there didn’t appear to be problems with the astronauts’ balance or visual memories, suggesting no impairment.
“These findings have important implications as we continue space exploration,” senior author Dr Juan Piantino, assistant professor of pediatrics (neurology) in the Oregon Health & Science University School of Medicine, said in a statement. “It also forces you to think about some basic fundamental questions of science and how life evolved here on Earth.”
Once in space, the fluids in our bodies shift. This is a consequence of not having gravity pulling everything down. Our body undergoes changes, including getting rid of red blood cells, to reach a balance or homeostasis again. This change in the brain seems to be a consequence of that and it is seen in first-time astronauts before and after their first flights. Veteran astronauts, on the other hand, don't seem to experience any changes in perivascular space before and after flying.
“Experienced astronauts may have reached some kind of homeostasis,” Piantino said.
The perivascular spaces in the brain are considered the underlying “hardware” of the glymphatic system. This is the system that cleanses the brain of metabolic proteins and it works best in deep sleep.
When the glymphatic system is not working too well, there is a build-up of metabolic proteins, which has been associated with the development of dementia. The perivascular spaces have been known to enlarge as a person ages.
“These findings not only help to understand fundamental changes that happen during space flight, but also for people on Earth who suffer from diseases that affect circulation of cerebrospinal fluid,” Piantino said.
This is not the first study to look at the brains of space travelers. A previous report saw an increase in the quantity of gray matter on the top of the brain and a reduction at the bottom, again a consequence of a shift in cerebrospinal fluid.