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On 08.04.2023 at 10:00 a.m.
Modified on 08.04.2023 at 22:00
If human genetics mold our body to evolve on Earth, it does not prepare it at all for a stay in space. Weightlessness and adaptation to a zero-gravity environment have consequences for the health of astronauts. Especially on their brain.
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The scriptwriters of Star Wars or Star Trek have never taken this data into account. Traveling in space is not trivial for the human body. We already know that weightlessness has an influence on the muscles which tend to atrophy. The same is true for the heart, which can lose up to 27% of its mass, as was observed in astronaut Scott Kelly on his return from a long stay on board the ISS in 2015. Two studies are recently added to scientific knowledge because they have looked into the effects of space travel on the brain.
A “rewired” brain
The most recent of these two experiments, the results of which were published in the journal Frontiers of neutral circuits at the end of February, was carried out by a team of researchers from the European space agency and Roscosmos, the Russian agency. Together, they examined twelve astronauts before and following their mission aboard the International Space Station. They subjected them to MRIs with a specific technique called “tractography” which highlights the neural pathways of the brain.
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Their analyzes revealed several changes in the subjects’ cortex. First, the regions in charge of motricity have undergone some modifications. In space, astronauts must adopt new movements to move and this upheaval has caused a variation in the connection between the neurons initiating movement commands. “In weightlessness, an astronaut must adapt his movement strategies in relation to the Earth. Our study shows their brains have rewired, so to speak “explains Andrei Doroshin, one of the authors of the study.
In addition, they noted a dilation of the cerebral vesicles which are between the right and left hemisphere causing a compression of the corpus callosum, the part which makes the junction between the two hemispheres.
Essential experiments for lunar and martian missions
These findings complement work from Oregon Health and Science University. In May 2022, American researchers also subjected astronauts to an MRI. They were regarding fifteen to have stayed several on board the ISS. Their brains were scrutinized before their departure, upon their return and then 3 and 6 months following resuming daily life on Earth.
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Here, it is another zone, around the cortex, which was observed. The scientists focused on the perivascular spaces, tiny interstices around the veins and arteries that supply the brain. It is in these spaces that circulates the cerebrospinal fluid responsible for evacuating certain proteins during sleep. A sort of cleaning circuit. The observations of the researchers had something to puzzle them. Indeed, the stay in space had the effect of dilating these perivascular spaces, but only in the least experienced astronauts, fortunately without associated symptoms. Those with more flying hours showed no variation.
If their study did not succeed in explaining this difference, it nevertheless makes it possible to adapt the care and the instructions given to novice cosmonauts. On land, excessive dilation of the perivascular spaces is observed in elderly people with dementia and those with hydrocephalus responsible for vomiting, epileptic seizures or hypertrophy of the head. Preventing these ailments in astronauts who will soon be on the Moon with the Artemis mission or on Mars by 2040 is an essential issue for the future of space exploration.
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