Spending long periods in space not only leads to muscle atrophy and reductions in bone density, it also has lasting effects on the brain, suggests a study.
However, little is known about how different tissues of the brain react to exposure to microgravity, and it remains unclear whether and to what extent the neuroanatomical changes so far observed persist following return to normal gravity.
About the study
The study was led by a team of neuroscientists from the University of Antwerp in Belgium and Ludwig-Maximilians-University (LMU) of Munich.
It was published in the journal New England Journal of Medicine.
Cosmonauts examined
The study was carried out on 10 cosmonauts, each of whom had spent an average of 189 days on board the International Space Station (ISS).
The authors used magnetic resonance tomography (MRT) to image the brains of the subjects both before and shortly after the conclusion of their long-term missions.
In addition, seven members of the cohort were re-examined seven months after their return from space.
"This is actually the first study in which it has been possible to objectively quantify changes in brain structures following a space mission also including an extended follow-up period," LMU neurologist Peter zu Eulenburg points out.
"We started this research in 2013", says Angelique Van Ombergen of UAntwerp.
"This kind of study always takes a long time, as very few people actually go into space," she added.
Pre-space travel v/s post-space travel results
The MRT scans performed in the days after the return to Earth revealed that the volume of the grey matter (the part of the cerebral cortex that mainly consists of the cell bodies of the neurons) was reduced compared to the baseline measurement before launch.
In the follow-up scans done seven months later, this effect was partly reversed, but nevertheless still detectable.
In contrast, the volume of the cerebrospinal fluid, which fills the inner and outer cavities of the brain, increased within the cortex during long-term exposure to microgravity.
Moreover, this process was also observable in the outside spaces that cover the brain after the return to Earth, while the cerebrospinal fluid spaces within returned to near normal size.
The white matter tissue volume (those parts of the brain that are primarily made up of nerve fibres) appeared to be unchanged upon investigation immediately after landing.
However, the subsequent examination six months later showed a widespread reduction in volume relative to both earlier measurements.