Travelling in space can play havoc with the human mind. Because of micro-gravity, astronauts frequently experience weird sensory effects, such as the world suddenly appearing upside down. Even their ability to rotate objects in their mind’s eye is sometimes affected. A new open-access study in the journal Microgravity is the first to explore the structural brain changes caused by spaceflight and which may contribute to, or reflect, these and other sensory and cognitive effects.
Vincent Koppelmans and his colleagues, including Jacob Bloomberg at NASA’s Johnson Space Center in Houston, compared brain scans taken of 27 astronauts before a space mission with a second scan taken once they were back on earth. The results revealed a mix of shrinkage and enlargement across the brain. There were widespread reductions in grey matter as well as some more localised increases in grey matter in regions that are involved in sensory processing and motor control.
Thirteen of the scanned astronauts had taken part in shuttle missions lasting around two weeks, the others had visited the International Space Station for a period of around six months. The pre-mission scans were conducted a median of 194 days before the mission, usually after significant amount of astronaut training had already been completed, which helps reduce, but not eliminate, the possibility that any observed brain changes were caused by training rather than spaceflight. The post-mission scans were taken between one to twenty days after landing back home.
On average, after experiencing spaceflight, the astronauts’ brains had shrunk in various frontal and temporal regions and in the cerebellum (a region at the back of the brain involved in coordination, among other things). This is fairly similar to what’s been found in a previous study of the effects of 70 days’ bed rest on brain structure, which was intended to be an approximate simulation of micro-gravity.
Koppelmans and his colleagues think these widespread grey matter reductions – which were more extensive in astronauts who’d spent longer in space – might be caused by the way that micro-gravity leads to increased fluid pressure in the brain leading to a gradual upward shift of the brain’s centre of mass in the skull (our bodies usually compensate for the downward pull of gravity on internal fluids; when gravity is reduced, the compensation processes continue, leading to pressure build up in the head and brain).
Meanwhile, there were also some more localised areas in which brain volume appeared to have increased, on average, including in parts of the parietal lobe, which are involved in motor control. This might reflect changes to brain structure involved in the astronauts’ adaptation to a micro-gravity environment. However, the magnitude of these brain changes did not correlate with the amount of balance problems that the astronauts showed after landing back on earth.
This study marks a useful start in understanding how spaceflight affects the physical structure of the brain, which in turn could help inform counter-measures to help astronauts adapt to microgravity during flight and then cope with adapting back to life on earth. However, as the researchers acknowledge, the results are speculative because of the many methodological drawbacks. For example, the fact the astronauts had a range of spaceflight experiences and the initial brain scans were sometimes taken many months before take-off means that the study lacked precision. Moreover, some of the astronauts already had earlier spaceflight experiences, which may have already altered their brain structure.