(h) EPA/SpaceX
Illustrative image of astronauts from SpaceX Crew Dragon Demo2 (2020)
A new study analyzed brain MRI scans of 26 astronauts and found that the longer they spent in space, the more their brains moved in the skull.
Going to space is hard on the human body. As a study concluded in January in PNASthe brain moves up and back and deforms inside the skull after space flight.
Research has also shown that the extent of these changes is greater for those who spent more time in space.
As NASA plans longer space missions and space travel expands beyond professional astronauts, these discoveries will become increasingly relevant.
Why it’s important
On Earth, gravity constantly pulls the fluids in your body and your brain toward the center of the Earth. In space, this force disappears. Body fluids move toward the head, which gives the astronauts a swollen face. Under normal gravity, the brain, cerebrospinal fluid and surrounding tissues reach a stable equilibrium. In microgravity, this balance changes.
Without gravity pulling it down, the brain floats in the skull and experiences various forces from the surrounding soft tissues and the skull itself.
Previous studies have shown that the brain appears higher in the skull after spaceflight. But most of these studies have focused on average or whole-brain measurements, which can mask important effects within different areas of the brain. The aim of the new “was to observe more closely”.
How we do our work
As he details in an article in , brain MRI scans of 26 astronauts who spent different periods of time in space, from a few weeks to more than a year, were analyzed.
To focus on brain movement, each person’s skull was aligned between scans before and after spaceflight.
This comparison made it possible to measure how the brain moved in relation to the skull itself. Instead of treating the brain as a single object, he divided it into more than 100 regions and tracked how each one moved. This approach allowed us to see patterns that were overlooked when looking at the brain as a whole, on average.
It turned out that the brain “consistently moved up and back” when comparing post-flight with pre-flight. The longer someone stayed in space, the greater the displacement. One of the most striking discoveries came from examining individual brain regions.
In astronauts who spent about a year aboard the International Space Station, some areas near the top of the brain moved upward by more than 2 millimeters, while the rest of the brain barely moved at all. This distance may seem small, but within the densely packed space of the skull, it is significant.
As areas involved in movement and sensation showed the largest displacements. Structures on both sides of the brain moved toward the midline, meaning they moved in the opposite direction in each brain hemisphere. These opposing patterns cancel each other out in whole-brain averages, which explains why previous studies haven’t detected them.
A Most displacements and deformations gradually returned to normal within six months of returning to Earth.
O backward displacement showed less recoveryo, probably because gravity pulls downward rather than forward, so some effects of spaceflight on brain position may last longer than others.
What’s next
NASA’s Artemis program will mark a new era of space exploration. Understanding how the brain responds will help scientists assess long-term risks and develop countermeasures.
These findings do not mean, however, that people should not travel to space, nor do they reveal immediate health risks.
Furthermore, the crew members did not experience overt symptoms – such as headaches or brain fog – related to the shifts in brain position.
Knowing how the brain moves during space flight and subsequently recovers allows researchers to understand the effects of microgravity on human physiology, and could help space agencies design safer missions.
