Is French astronaut Thomas Pesquet’s brain the same on earth as it is aboard the international space station (ISS)? Though humans are subjected to significant sensorimotor changes during space flights, until now no studies had ever examined the effects of space travel on the structure of the human brain. But this is changing thanks to researchers at the University of Michigan who have recently published a first report on the structural brain changes in humans due to space travel. How does the human brain change in space?

For their study, a team led by V. Koppelmans used data from 27 astronauts, 13 of whom had spent 2 weeks in space (inside a shuttle) and 14 others who had spent 6 months (inside ISS). The subjects’ ages ranged from 40 to 60 (average = 48) and their experience with space flights varied from 0 to over 300 days. All information (MRI and neurosensory data) was collected during medical follow-ups after each of the different missions. So what did the scientists find?

First, variations in gray matter volume were seen in different brain areas. Keep in mind that neurons are found in this “gray matter,” which processes information from different sensory organs. Thus, the researchers saw a reduction in the gray matter volume in large areas covering the temporal and frontal lobes and around the eye sockets. And this effect is more pronounced in ISS astronauts than in the members of the shuttle team. Conversely, they saw an increase in gray matter in the somatosensory and motor cortex, the brain areas linked to the movement of the lower limbs.

According to the authors of the study, published in npj Microgravity, this change can be explained by the astronauts’ need to adapt and learn to move about in an environment with low gravity. According to them, certain brain areas lose gray matter due to the absence of gravity. The observations indicate that the longer the trip, the greater the changes in the astronauts' brains. It can be seen as an “extreme illustration of brain plasticity, proof that our brain is capable of adapting to many situations."

Given the increase in the duration of manned flights, the studies on the extent and types of structural changes that can occur in the human brain during long stays in space should also increase. Learning more about these brain changes in astronauts is all the more critical in developing plans to remotely explore Mars.