Our brains change as we age and grow here on Earth. But what happens to the human brain after being in space for a long time?
In a new study, a collaborative effort between the European Space Agency and Russia's space agency Roscosmos, researchers have explored how cosmonauts' brains change after traveling to space and back. And they showed how the brain adapts to spaceflight, finding that the brain is almost "rewired," and both fluid shifts and shape changes occur. These changes can last for months after a person returns to Earth, the researchers found.
The strange brain changes that the team observed were "very new and very unexpected," study lead Floris Wuyts, a researcher at the University of Antwerp in Belgium, told Space.com.
How to study the brain in space
For this study, the international research team studied the brains of 12 male cosmonauts shortly before and after their flights to the International Space Station. They also observed these same cosmonauts' brains seven months after returning to Earth. All cosmonauts in this study took part in long-duration flights that lasted, on average, 172 days, or just over five and a half months.
"We focused initially on neuroplasticity to see how the brain adapts to spaceflight," Wuyts said, adding that the team also focused on connectivity within the brains of the cosmonaut subjects.
"Structural analyses [of astronaut brains] have been done already, but not yet connectivity research," Wuyts said. "With this paper [on] connectivity, we finally approach the answers regarding this neuroplasticity."
To accomplish this, the team used a brain imaging technique called fiber tractography, a 3D reconstruction technique that uses data from diffusion MRI (magnetic resonance imaging), or dMRI scans to study the structure and connectivity within the brain.
"Fiber tractography gives a sort of wiring scheme of the brain. Our study is the first to use this specific method to detect changes in brain structure after spaceflight," Wuyts said in an emailed statement.
MRI data can tell researchers quite a lot about a subject's brain, Wuyts explained.
"MRI looks at structure at the level [of] gray matter (like the microprocessors in a PC) and white matter (the connections on the motherboard of a PC, between all the processing units). MRI also looks at the fluid in the brain, called the cerebrospinal fluid (CSF)," Wuyts told Space.com.
What changes in the brain?
"After spaceflight, these structures appear to be altered, mainly due to the deformations that are caused by the fluid shift which happens in space," Wuyts said. Interestingly, the team also found an increase in gray and white matter. In the brain, white matter facilitates communication between gray matter in the brain and between gray matter and the rest of the body.
In addition to this fluid shift, the team noticed shape changes in the brain, specifically in the corpus callosum, which is a large bundle of nerve fibers that Wuyts described in the statement as "the central highway connecting both hemispheres of the brain."
Previously, it was thought that spaceflight could cause structural changes in the corpus callosum itself. However, the team found that the ventricles nearby actually dilate, which shifts the neural tissue of this region around the corpus callosum, changing its shape, Wuyts explained. Ventricles in the brain are pockets that both produce and store CSF, the fluid that surrounds the brain and spinal cord.
The researchers also "found changes in the neural connections between several motor areas of the brain," lead author Andrei Doroshin, a researcher at Drexel University in Pennsylvania, said in the statement. "Motor areas are brain centers where commands for movements are initiated. In weightlessness, an astronaut needs to adapt his or her movement strategies drastically, compared to Earth. Our study shows that their brain is rewired, so to speak."
"From previous studies, we know that these motor areas show signs of adaptation after spaceflight. Now, we have a first indication that it is also reflected at the level of connections between those regions," Wuyts added in the statement.
But these changes weren't just noticed immediately after cosmonauts returned to Earth. In the brain scans taken of the subjects seven months after landing, the team found that these changes were still present.
What can be done?
This study is part of a growing body of research that is exploring exactly how spaceflight, especially long-duration space travel, affects the human body. This isn't the end of our understanding on the subject, but it does reveal new insights into how the brain can be affected, information which researchers can then use to better protect humans going to space.
"Our research shows that we should invoke countermeasures to be sure that the fluid shifts and shape changes of the brain are limited," Wuyts told Space.com.
Wuyts added that one measure that could reduce these effects would be artificial gravity. Artificial gravity is, in theory, created by an inertial force to replicate the feeling of gravity as, for example, we experience it here on Earth. A well-worn staple of science fiction, scientists in recent years have started to bring this concept into reality.
"Using artificial gravity on board the space station or [a] rocket to Mars will most likely solve the fluid shift issue. The rotating donut like in the film by Stanley Kubrick 'Space Odyssey 2001' is a great example of what would be ideal. However, it is complicated to realize. Yet, it may be the way to go. Future research will tell," Wuyts said.
This work was published Friday (Feb. 18) in the journal Frontiers in Neural Circuits.