Long-term consequences for the astronaut brain

White matter and cerebral fluid change months after their return

A longer space mission leaves long-term consequences in the brain of the astronauts - they are still detectable months later. © NASA
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Persistent aftereffects: Long space missions alter the brain structure of astronauts - and these consequences can persist for months after landing, as revealed by a long-term study. For Russian cosmonauts, cerebral fluid increased seven months after the return to Earth, while the white matter shrank. Whether these late effects can affect the intellectual achievements of astronauts, is still unclear. Before a Mars flight or a moon station this must be clarified urgently, so the researchers.

Astronauts do not have it easy: Even in low Earth orbit, they get a fever and their muscles and bones dwindle through the weightlessness, if they do not constantly train against it. However, if they leave the protective sphere of the terrestrial magnetic field, further adversity threatens. Observations on Apollo astronauts suggest that cosmic rays could damage the cardiovascular system. And in mice, the high-energy particle bombardment even caused dementia and brain damage.

Less gray matter after landing

But as it turns out, the brain of astronauts even changes in the Earth orbit - and this sustainable. This was discovered by Angelique Van Ombergen of the University of Antwerp and her colleagues when they analyzed the brain structure of ten cosmonauts who spent an average of 189 days on board the International Space Station (ISS) between 2014 and 2018. The participants were examined before their start, immediately after landing and seven months later by means of magnetic resonance tomography.

The result: As already known from previous studies, the brain structure changed during the stay in orbit. The gray matter shrank as the fluid-filled spaces in the brain gained volume. However, the white matter - the part of the brain tissue that mainly consists of nerve fibers - hardly changed immediately after landing, as the researchers report. The cause of these changes are the altered pressure conditions in the body during weightlessness.

Delayed consequences for white matter

But the surprising thing was the long-term consequences: Seven months after returning to Earth, the gray matter in the brain of the cosmonauts had clearly recovered. In some areas, however, including the right temporal lobe, the volume remained smaller than before the space visit, as the brain scans revealed. On the other hand, the cerebral fluid had not returned to normal: its volume had risen further. In addition to the ventricles, the fluid in the area around the brain was now increasing. display

There were also consequences for the cosmonaut's white matter: it shrank significantly in the months after landing. "Compared to the measurements immediately after the space flight, there was a global reduction of the white matter in the long-term control, " report Van Ombergen and her colleagues.

Impact on mental performance unclear

"Overall, our findings point to a continued change in CSF circulation many months after returning to Earth, " says co-author Peter zu Eulenburg of the University of Munich. "Whether the observed large-scale changes in the gray and white matter are of relevance for the cosmonaut's cognition is currently unclear." To assess possible risks to cosmonauts To better estimate astronauts, further studies are urgently needed.

The Grudn is obvious: at least before the start of manned missions to the Moon and Mars should be clarified in which mental state the astronauts would arrive at their destination. (The New England Journal of Medicine, 2018; doi: 10.1056 / NEJMc1809011)

(Ludwig-Maximilians-University Munich, 25.10.2018 - NPO)