Global Courant
What happens to the brain when you take away gravity? That experience causes physical changes that researchers believe take at least three years to recover from between longer missions, according to a new study that looks at astronauts both before and after space travel.
The study looked at the brains of 30 astronauts and found that cavities in the brain had enlarged during their time off Earth.
Astronauts who went into space for six months had the most marked change in their brains, while shorter trips of two weeks or less came with very little physical change in comparison.
“We found that the more time people spent in space, the larger their ventricles got,” said Rachael Seidler, a professor of applied physiology and kinesiology at the University of Florida and author of the study. said in a press release. “Many astronauts travel to space more than once, and our research shows that it takes about three years between flights for the ventricles to fully recover.”
It’s actually not a new idea that space travel changes our bodies. It has long been documented that the lack of gravity affects muscle and bone mass, and previous studies have also looked at how space affects brain morphology.
What happens when you spend time in space is that the lack of gravity causes the brain to essentially float to the top of the skull, a physical shift seen in displacements of cerebrospinal fluid, which surrounds the brain. Previous research has tracked how astronauts returning home to Earth subsequently experienced a decrease in fluid at the top of the brain and an increase in volume at the base of the brain — fluid that flows back down as gravity reaffirms itself.
Structures also shift in the brain itself. Gray matter, the tissue in the brain that contains neurons and connections that enable much of our daily functioning, increases in volume at the top of the brain as a result of space travel, while it decreases at the base of the brain.
But while this phenomenon has been studied before, scientists still don’t know the implications for more long-term space travel.
HOW THE BRAIN CHANGES AS YOU STAY IN SPACE LONGER
What this new study, published Thursday in the peer-reviewed journal Scientific Reportswanted to investigate whether the impact on your brain increases the longer you stay in space.
They found that the answer was yes, but that this effect didn’t start right away or last forever. Instead, there was a time period when most of the changes occurred.
“The biggest jump comes when you go from two weeks to six months in space,” Seidler said. “There is no measurable change in ventricular volume after just two weeks.”
Ventricles are cavities in the blood that contain cerebrospinal fluid, a substance that helps the brain and spinal fluid collect and drain waste products from the brain. As the fluid moves upward in the body due to the lack of gravity, the ventricles in the brain expand.
The expansion of ventricles is something that happens naturally as we age, but the expansion we saw in the astronauts was greater than what happens with age.
Researchers looked at both ventricular expansion and gray matter volume over time and found that short space travel of two weeks or less resulted in smaller ventricular increases or even decreases compared to longer trips.
Longer trips meant more ventricular enlargement and gray matter displacement, but after six months this effect slowed down — a good sign, researchers say, that this effect won’t get exponentially worse as space travel gets longer and longer.
“Crew members who completed 6-month and 1-year missions showed similar degrees of expansion of these ventricles post-flight, providing preliminary evidence that changes begin to subside during 6-month missions,” the authors wrote. the research.
Half of the data comes from a previous study of the effects of spaceflight between 2014 and 2020, which used astronauts who had spent six months or an entire year on the International Space Station. The other 15 astronauts came from the NASA Lifetime Surveillance of Astronaut Health Repository.
WHAT DOES THIS MEAN FOR ASTRONAUT RECOVERY?
If the brain is affected so much by one trip to space, what about several?
Researchers looked at the length of time astronauts had between spaceflights to see if it affected their brain changes on their next trip.
They found that when astronauts had less than three years to recover from their previous space mission before going back into space, their ventricles expanded less on the second trip — because they hadn’t fully healed and returned to their normal state.
Scientists theorize that the expansion of the brain’s ventricles during spaceflight could help humans compensate for other effects on the brain, meaning a weakened ability to expand and contract could be a problem.
If the ventricles are already enlarged from a previous long-duration space journey when an astronaut returns to space, they may not be able to expand properly and have less cerebrospinal fluid storage, which means less protection for the brain.
Researchers say this study could help establish baselines for travel duration and recovery times for astronauts and space travelers as space tourism picks up and people reach for the stars more and more.
“We’re not yet sure what the long-term implications of this are for the health and behavior of space travelers,” Seidler said, “so it seems like a good idea to give the brain time to recover.”
Only a handful of the astronauts included in the study had been on a year-long mission, meaning there are still many questions about long-term space travel.
The study has a few other limitations, including the lack of MRI scans for all participants, as well as different MRI scan parameters between the two groups. Researchers obtained MRI brain scans from 28 of the astronauts, but only had complete scans from 15 of them in total. The MRI scans after space travel were also obtained on average about six days after the astronauts landed back on Earth, meaning the brain may have already begun to recover from the space effects before the scan.
