Overview
- Pre- and postflight MRI scans of 26 astronauts showed millimeter-scale upward and backward brain movement along with regional reshaping.
- Shifts were greatest in sensory and sensorimotor regions, with posterior insula displacement associated with post-flight balance declines.
- Changes scaled with mission duration, with yearlong stays showing the largest effects and even two-week flights showing detectable shifts.
- Most deformation resolved within about six months after return, though some measures persisted, and serious cognitive symptoms were not observed.
- A 24-participant head-down bed-rest analog produced similar but smaller changes, highlighting operational questions for lunar and Mars planning and the need for larger, more diverse samples.