Scans of the astronauts’ brains showed that the organ adapts to weightlessness. Analysis of the images of eleven astronauts, who spent about six months in orbit, revealed an increase in white and gray matter in three areas of the brain that are closely associated with physical movement.
These changes reflect the “neuroplasticity” of the brain, in which nerve tissue, in this case, the cells that control movement or motor activity, readjust to cope with the new needs of life in orbit.
“With the techniques we used, we can clearly see microstructural changes in the three main areas of the brain that are involved in processing information,” said Stephen Gillings, a neuroscientist at the University of Antwerp in Belgium.
Before and after images of the astronauts’ brains, it was confirmed that cerebrospinal fluid also redistributes itself, pushing the brain towards the top of the skull. It also expands the fluid-filled cavities – this may be due to the loss of visual acuity of astronauts.
The scans also revealed microstructural changes in three areas of the brain: the primary motor cortex, which sends signals to muscles, the cerebellum, and the basal ganglia. Some of the changes persisted for seven months after returning to Earth.
There is also an assumption that the volume of white and gray matter decreases due to neurodegeneration – the death of a part of nerve cells. In this case, changes in the structure of the astronauts’ brains are likely to be permanent or at least long-term: if the formation of new neurons in adults continues, then it is unlikely to be able to completely cover the loss of cells in this case. However, there are no studies in which changes in the brain structure of those who have been in space were monitored for at least several months after returning to Earth.