Credit: PNAS
I've been captivated by everything related to space travel and how it affects the bodies of those who travel outside of Earth. Consider astronauts that spend months floating in orbit; how would their bodies change? How about their brains?
The latest MRI studies show that if you are in space for a long time, gravity's effects on the brain can actually displace it up and down, stretching and squeezing areas of the brain responsible for movement and sensory processing.
As NASA and other international space agencies prepare for extended missions beyond the Earth to the Moon and Mars, understanding and maintaining the neurological health of astronauts will play an integral role in astronaut safety and performance.
On Earth, gravity helps fluids and soft tissue stay in the same general area of the body (ie fluid between the brain and skull). In microgravity, however, fluids tend to shift toward the head. This redistribution can alter how cerebrospinal fluid interacts with the brain, sometimes causing the brain to shift slightly within the skull. MRI studies of astronauts have shown that long periods in microgravity can lead to small structural changes in brain position and shape.
Prior research suggested that isolation and uncontrolled weightlessness would negatively impact one's all-around health (physical and mental); however, MRI technology has allowed scientists to see these types of physical changes. Where normal (pre-space) MRI scans will show brain positions near the center of the skull, astronauts show that the brain has been displaced upwards and backwards within the skull after returning from an extended duration (6 months) mission aboard the ISS.
Astronauts' displacements show deformations in specific areas of the brain responsible for balance, coordination, and sensory perception. Although individuals will experience a gradual return to normalcy in their brains, some backwards displacements and rotations may remain for longer periods due to the extent of being in microgravity, thus emphasizing the importance of monitoring their neurological health and establishing countermeasures to mitigate the effects of being in space for long periods.
"These findings are critical for understanding the effects of spaceflight on the human brain and behaviour," as noted in the study's significance statement (from researchers including lead author Tianyi Wang and senior author Rachael D. Seidler)
To further reduce the risk, astronauts should follow exercise programs and utilize countermeasures that help retain impairment of balance or equilibrium. In addition to monitoring the neurological health of astronauts, space agencies will also be required to implement procedures and technology that help limit or manage upward displacement, such as using lower-body negative pressure suits, as well as provide periodic assessments of the astronauts' neurological health to facilitate astronauts' ability to remain alert, coordinated, and cognitively intact over a long space mission.
Space travel poses numerous challenges to the astronaut's body. More importantly, it is also changing the astronaut's brain. Understanding what these changes are and developing countermeasures to mitigate these changes will help ensure the successful safety and capability of humans as they explore the Moon, Mars, and beyond.
Reference
Wang, T., Odor, R. J., De Dios, Y. E., Mulder, E., Bloomberg, J. J., Wood, S. J., & Seidler, R. D. (2026). Brain displacement and nonlinear deformation following human spaceflight. Proceedings of the National Academy of Sciences, 123(3), e2505682122. https://doi.org/10.1073/pnas.2505682122