Space Travel Shifts Brain Position, Study Finds – and What It Means for Future Missions

Going to space is harsh on the human body, and a new study finds that the brain shifts upward and backward and deforms inside the skull after spaceflight.

The extent of these changes was greater for those who spent longer in space. As NASA plans longer space missions, and space travel expands beyond professional astronauts, these findings will become increasingly relevant.

Why it matters

On Earth, gravity constantly pulls fluids in your body and your brain toward the center of the Earth. In space, that force disappears. This fluid shift causes astronauts to experience a puffy face. Under normal gravity, the brain, cerebrospinal fluid, and surrounding tissues exist in a stable balance. In microgravity, that balance changes. Without gravity pulling downward, the brain essentially floats within the skull, experiencing forces from the surrounding soft tissues and the skull itself. Previous studies indicated that the brain appears higher in the skull after spaceflight, but often focused on average or whole-brain measures, potentially obscuring important effects within specific brain areas.

This new research aimed for a more detailed examination. Researchers analyzed brain MRI scans from 26 astronauts who spent varying lengths of time in space, ranging from a few weeks to over a year. To focus on brain movement, they aligned each person’s skull across scans taken before and after spaceflight. This comparison allowed them to measure how the brain shifted relative to the skull. Instead of treating the brain as a single unit, they divided it into over 100 regions and tracked the movement of each one, revealing patterns that might have been missed when looking at the whole brain as a single entity.

The study found that the brain consistently moved upward and backward when comparing postflight scans to preflight scans. The longer an astronaut spent in space, the more pronounced the shift. In astronauts who spent approximately a year aboard the International Space Station, some areas near the top of the brain moved upward by more than 2 millimeters, while other areas showed minimal movement. While 2 millimeters may seem small, it is a significant distance within the confined space of the skull.

Areas of the brain involved in movement and sensation exhibited the largest shifts. Structures on opposite sides of the brain moved toward the midline, a pattern that would be masked when considering the whole brain average. Most of these shifts and deformations gradually returned to normal within six months of returning to Earth. However, the backward shift showed less recovery, potentially because gravity pulls downward, not forward, meaning some effects of spaceflight on brain position may be longer lasting.

How we do our work

The research team analyzed brain MRI scans from 26 astronauts, comparing scans taken before and after spaceflight. By aligning each astronaut’s skull, they were able to precisely measure the brain’s shift relative to the skull. This detailed approach, dividing the brain into over 100 regions, allowed for the identification of subtle patterns that would have been missed by analyzing the brain as a whole.

What’s next

As NASA’s Artemis program ushers in a new era of space exploration, understanding how the brain responds to the challenges of spaceflight is crucial. This knowledge will help scientists assess long-term risks and develop countermeasures to protect astronauts on future missions.

Importantly, the study’s findings do not suggest that space travel is inherently unsafe. While larger shifts in certain brain regions correlated with postflight balance changes, the astronauts did not experience overt symptoms like headaches or brain fog. The research provides valuable insights into the physiological effects of microgravity, allowing space agencies to design safer missions and better prepare astronauts for the challenges of long-duration spaceflight.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.