Traveling in space can alter the brain, according to a study

Spending long periods in space can not only lead to muscle atrophy and reduced bone density, but also have lasting effects on the brain, warned the first long-term study of Russian cosmonauts. exposure to microgravity, said a researcher from the Ludwig Maximilian University Munich (LMU) in Germany. It is unclear whether and to what extent the neuroanatomical changes observed until now persist after the return to normal gravity, they said.

The study, published in the New England Journal of Medicine, shows that differential changes in the three major brain tissue volumes remain detectable for at least six months after the end of their last mission. The study was conducted on ten cosmonauts, each of whom spent an average of 189 days aboard the International Space Station (ISS). Researchers used magnetic resonance tomography (MRT) to image subjects' brains before and shortly after the end of their long-term missions.

In addition, seven members of the cohort were re-examined seven months after their return from space. "It is actually the first study in which it has been possible to objectively quantify changes in brain structures following a space mission, including an extended follow-up period", said Peter zu Eulenburg, professor at LMU. MRT analyzes performed a few days after returning to Earth revealed that the gray matter volume (the part of the cerebral cortex made up mainly of neuronal cell bodies) was reduced compared to baseline measurement before launch.

In the follow-up analyzes performed seven months later, this effect was partly reversed, but still detectable. In contrast, the volume of cerebrospinal fluid, which fills the internal and external cavities of the brain, increased in the cortex during prolonged exposure to microgravity.

In addition, this process was also observable in the outer spaces that cover the brain after return to Earth, while the spaces of cerebrospinal fluid inside had returned to an almost normal size. The volume of the white matter tissues (the parts of the brain mainly made of nerve fibers) seemed to have remained unchanged during investigations immediately after the landing. However, the subsequent review six months later showed a generalized reduction in volume compared with the previous two measurements. In this case, the researchers postulate that during a long passage in space, the volume of the white substance can be replaced slowly by an influx of cerebrospinal fluid.

On return to Earth, this process is then gradually reversed, resulting in a relative reduction in the volume of white matter. "Taken together, our findings indicate prolonged changes in the pattern of cerebrospinal fluid circulation over a period of at least seven months after returning to Earth," said Eulenburg.

"However, the fact that significant changes in the gray matter and white matter are leading to changes in cognition is still unclear," he said. According to the researchers, in order to minimize the risks associated with long-term missions and to characterize any clinical significance of their structural outcomes, new studies using a greater number of diagnostic methods are considered essential.