Spaceflight shifts astronauts' brains backward, upward and tilted inside the skull

An MIT study found that astronauts' brains tend to move backward, upward and rotate after time in microgravity, with some positional changes still detectable up to six months after return; a head‑down bed‑rest analog produced similar but not identical shifts.

A team led by Rachel Seidler at the Massachusetts Institute of Technology examined how spaceflight affects brain anatomy using MRI scans. The researchers analyzed scans from a group that included astronauts and participants in a long‑duration head‑down tilt bed‑rest experiment. The study, published Jan. 12, compared regional brain positions before and after time in microgravity or its analog. The authors report persistent position changes in multiple brain regions after spaceflight. Key findings: - The analysis divided the brain into 130 regions and found consistent displacement across many areas rather than a single localized shift. - Across participants, brains tended to move backward and upward and to rotate in pitch after exposure to microgravity. - Some individual displacements measured up to about 2.52 millimeters in subjects with the most time in space. - The bed‑rest analog produced broadly similar directional movement but with differences: astronauts showed a stronger upward component while bed‑rest participants showed a stronger backward component. - Displacement in sensory‑related brain regions was associated with larger declines in balance after landing, and some anatomical changes persisted for as long as six months post‑flight. - The authors note typical spaceflight research limits, including small sample sizes and constrained imaging schedules. Summary: The study documents measurable shifts in how the brain sits inside the skull after exposure to microgravity and links some regional changes with balance declines on return to Earth. The authors recommend further research with larger astronaut groups and a range of mission lengths to clarify when shifts begin, how they evolve, and how recovery unfolds.