Astronauts’ brains shift back, forward, and rotate inside skull during spaceflight, study finds

Astronaut Brains Move Backward, Upward, and Rotate (Image: Canva)

A study led by MIT researchers found that prolonged spaceflight causes the human brain to shift position inside the skull due to microgravity. Using MRI scans of astronauts and comparison groups, scientists observed lasting changes linked to balance issues after return, highlighting the long-term neurological effects of time spent in space.

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Spaceflight does more than change how astronauts see Earth, a new study reports, showing that time spent in microgravity physically shifts the brain’s position inside the skull, with effects lasting months after return.

What happens to the brain in microgravity

Researchers examined how extended space missions affect brain anatomy. The study was led by Rachel Seidler at MIT. It was published on 12 January. Scientists analysed MRI scans from astronauts and control participants. The team compared 26 astronauts with 24 non-astronaut participants. The focus was physiological changes, not psychological experiences. Researchers studied how microgravity alters brain positioning.

MRI scans showed consistent movement patterns after spaceflight. The brain shifted backward and upward inside the skull. It also rotated upward following time in space. Some changes remained months after Earth return. Scientists have long tracked spaceflight effects on bodies. Brain anatomy responses remain less clearly understood. This study aimed to close that knowledge gap.

What the study found across missions

Fifteen astronauts provided scans before and after missions. Another eleven astronauts contributed additional MRI data. Researchers also studied a bed rest experiment group. Bed rest simulated microgravity using head down tilt. The team divided the brain into 130 regions. Each region was analysed independently for displacement. Results showed widespread movement across many brain areas.

Changes occurred across two main spatial axes. This indicated broad repositioning, not localised effects. Participants included short and long mission astronauts. Groups represented two-week, six-month, and one-year missions. Longer missions showed greater positional brain shifts. Some displacements reached 2.52 millimetres in magnitude. Astronaut brains showed stronger upward movement patterns. Bed rest participants showed stronger backward shifts instead. Only some spaceflight changes appeared in simulations. This highlighted limits of current microgravity models.

What it means after astronauts return

Researchers examined links between brain changes and performance. Balance problems often affect astronauts after landing. Inner ear orientation takes time to readjust. The study found sensory region displacement linked to balance decline. Greater brain movement correlated with worse post-flight balance. Most astronauts regain balance within about one week. Brain position changes lasted far longer. Some shifts persisted up to six months. Authors described these as long lasting neuroanatomical effects. Scientists noted typical space research limitations. Sample sizes remain small and imaging windows tight. The team recommended studies with larger astronaut groups. Future research should cover broader mission durations. Scientists aim to understand onset and recovery timelines.