Staying in space for prolonged periods of time puts a strain on our bodies. Experiencing microgravity leads to changes to our anatomy, which has never had to adapt to deal with prolonged weightlessness. Bones lose calcium, the size and shape of your heart changes, eyes are deformed, and a major concern suggested being in space could lead to some permanent neurodegeneration.
In a study published in Science Advances, an international team of researchers studied the brains of 11 cosmonauts from the Russian Space Agency Roscosmos who spent on average six months on the International Space Station. They found no evidence suggesting that months in microgravity led to permanent damage to the nervous system. The findings also provide some important information on how the brain reorganizes itself in microgravity conditions.
The cosmonauts' brains were scanned using neuroimaging techniques like diffusion MRI imaging before the flight to space and then nine days after they returned to Earth. Eight of them were scanned a third time within seven months of returning from their space missions.
The interesting changes in the brain that the team report include an increase in the quantity of gray matter tissue in the top part of the brain and decreases in gray matter in the region that divides the frontal and parietal lobes from the temporal lobe. However, these changes were due to the shift of cerebrospinal fluid – without gravity, bodily fluids tend to accumulate in the head – not changes in net quantity of gray matter. This shift in cerebrospinal fluid observed supports previous evidence the brain itself moves closer to the top of the skull in microgravity, but also suggests the cerebellum shifts up, too.
When the eight cosmonauts were re-examined after seven months, the changes had mostly reversed, although the team noticed that the recovery was more pronounced at the top of the brain than at the bottom.
The team also reported changes to the cosmonauts' vision, which showed a decrease in sharpness after being in space, a symptom caused by a condition called spaceflight-associated neuro-ocular syndrome. The data suggested this was linked to larger expansion in the brain's ventricles, but this goes against a previous study's findings so the researchers suggest more observations are necessary to understand what exactly is happening.
This research is important because we lacked a full understanding of the effects living in space has on the human body, and this study provides some answers and highlights some important issues. Together with NASA’s twin study on astronauts Scott and Mark Kelly, it provides important insights into what future deep-space exploration might have to take into account.