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Before astronauts embark on a mission to Mars, it is imperative for scientists to know everything they can about the impact of long term space travel on the human body. Previous studies have shown that extended exposure to microgravity causes muscles and bones to weaken, deteriorates vision, and, in some cases, even alters the astronaut’s DNA. Now, there is evidence that spending a long time in space could also permanently change the brain’s structure.

The study, conducted by a team led by Dr. Donna Roberts of the Medical University of South Carolina, compared MRI brain scans of two groups of astronauts, all close in age and flight experience, taken before and after space missions. One, comprised 16 scientists who had spent an average of just two weeks aboard the International Space Station (ISS), while the other group of 18 had lived there for about six months.

The MRI’s showed that the brains of the long-term space travelers had floated upward and were closer to the skull. Roberts believes this is similar to the “fluid shift” – the upward movement of bodily fluids which has been previously observed in astronauts. The expert says, “One of our theories is that because there is no longer the force of gravity pulling the brain down, the brain moves upward.”

Brain images taken before and after spaceflight. Panels A and B show the before and after MRI scans from a long-duration spaceflight astronaut. Panels C and D show the before and after scans of a short-duration spaceflight astronaut. Photo Credit: NEJM

The brain’s upward movement causes the cerebrospinal fluid, which protects the precious organ and clears out metabolic waste, to move from the top of the brain into spaces, called ventricles, that lie within the brain. Roberts and her team are not sure if the fluid shift has a negative impact on the body. That’s because though displacement of the fluid has been observed in patients with brain disorders such as Alzheimer’s disease and multiple sclerosis, researchers have been unable to determine if it is the cause, or effect, of the affliction.

While the brain shift was not observed in astronauts who had been on the shorter duration missions, the scientists say it could be because the change was less dramatic, and adjusted itself before the MRI’s were taken.

These were not the only changes the brain scans uncovered. For 17 of the 18 astronauts, the central sulcus, a fold at the top of the brain that separates the motor cortex from the sensory cortex, also became narrower. This phenomenon was observed only in three of the 16 short-duration astronauts. Roberts speculates that the brain compression “might lead to functional changes,” and may be the reason some space travelers have a harder time adjusting to zero gravity. While the researchers initially thought the brain shift could also be pulling on the optic nerve, only three of the astronauts involved in the study suffered impaired vision, leading the scientists to conclude that there were probably other factors at work.

Image Credit: By NASA [Public domain], via Wikimedia Commons

Since none of the astronauts in the study have had a follow-up scan, the team, who published their findings in the New England Journal of Medicine on November 2, is not sure if the upward brain shift is permanent. But even if that is the case, experts do not think it will derail the Mars mission. Dorit Donoviel, the interim director of the Translational Research Institute for Space Health, is not surprised at the findings. The researcher thinks the human body is amazingly resilient and says that if need be, there are ways to prevent the “fluid shift” and keep the brain in position.

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