Microgravity affects the body in many interesting ways. If you watch videos of astronauts above the International Space Station, you may notice that their faces look puffy. This is because, without gravity, the fluids in the body that are usually distributed to the lower part of the body are free to be distributed more evenly.
This lack of gravity can also play a bit of havoc with human perception, too. Because the vestibular system, the inner ear system that senses direction and speed in order to maintain balance, relies on gravity, the absence of gravity causes the brain to feel like the body is falling.
But balance is also keyed in with vision; what the person sees works together with the vestibular system to let the brain know how the body is oriented. Because in space, the human sees nothing amiss while the inner ear reports a falling sensation, this can lead to dizziness and disorientation. Add to that the fluid that is now floating around in the astronaut's face, which feels like hanging upside down, and you have a lot of weird things going on in the brain.
After a few days in space, the brain does adapt to this weird set of circumstances, but there are interesting things going on in the old cranium that require looking into. For one thing, experienced astronauts returning to space adapt to this disorientation faster than newbies.
In addition, according to NASA research, and first-hand reports from astronauts, microgravity has an effect on the human ability to function, both physically and mentally. Astronauts have a harder time controlling their movements, and completing cognitive tasks.
To help figure out what is going on in the brain in both structure and function that causes these phenomena, both NASA and the ESA are putting astronauts through a series of tests.
Both space agencies are using a MRI machine to look at astronauts' brains pre- and post-flight.
For NASA, this is occurring as part of its NeuroMapping program at the University of Michigan under principal investigator Rachael Seidler, director of the university's Neuromotor Behaviour Laboratory. "We are looking at the volume of different structures in the brain and whether they change in size or shape during spaceflight," Seidler said.
The astronauts will undergo both functional and structural MRI scans. For the functional scans, they will complete a task while being scanned. This way, the researchers can gauge if there's any change in brain activity. The structural scan will look for physical changes in the brain, such as loss of volume.
For the ESA, the research, set to be completed in 2018, is being conducted by the universities of Antwerp, Liege and Leuven in Belgium, under the leadership of principal investigator Floris Wuyts, head of the Antwerp University Research Centre for Equilibrium and Aerospace. In May this year, Wuyts and his team published a paper that described a reduction in the brain's motor cortex, which controls movement, and the insular cortex, which controls balance.
This research, Wuyts said, is relevant here on Earth, too. It can help understand what happens to the brains of bedridden patients, since astronauts don't move around as much as people on Earth. It can also help understand conditions such as vertigo. Additionally, it can help understand how the brain adapts to change: Does it revert to a previous state, or does it have to learn how to compensate for a new set of circumstances all over again?
"The research on astronauts is an ethical way to look at people's brains before and after a stressful incident," Wuyts explained.
"Ideally, we would have brain scans of people when they were healthy and after they started suffering from a disorder, because then we can see where the changes have taken place. But such an ideal situation does not exist, and neither can we give subjects a traumatic experience on purpose, of course."
Astronauts' brains provide a rare opportunity, since researchers know more or less ahead of time what the astronauts are going to experience, and can therefore relate it back to similar experiences, such as perceptual signals going haywire, here on Earth.