How Does Spaceflight Affect White Matter in the Brain: A New Study
When it comes to spaceflight, there are various hazards that humans face. From a decrease in bone density and muscle mass to vision problems, and of course exposure to radiation. Now, experts are studying the effects of space on the human brain, and the results are concerning. A recent study published in JAMA Neurology finds that a zero-g environment can cause irregularities in the structure and shape of the brain.
These results highlight how little experts know about the effects of space on the health of the human brain. Rachael Seidler, the coauthor of the JAMA study and a professor of applied physiology and kinesiology from the University of Florida, explained that the changes they witnessed in the brain from spaceflight were similar to what they see as one grows old except the changes happened faster with spaceflight.
The results of the paper are focused on the way intracranial fluids move within the skull and, for the first time they studied how zero gravity impacts the brain’s white matter rather than gray matter, which is mostly made up of neuronal cell bodies and has a lot to do with muscle control and sensory perception. On the other hand, white matter is mainly composed of fat-covered nerve fibres, that work to pass messages from various parts of the brain to the nervous system. The development of grey matter reaches its peak when we are in our 20s, but white matter develops for much longer and only peaks at middle age. Thus, this causes more worry that spaceflight could impede or distort parts of brain development, especially in young astronauts who are usually the ones fit for long-duration spaceflight.
Many studies have revealed that when astronauts return to Earth, they feel disoriented and show signs of impairment in motor control, balance, and functional mobility and cognition. Furthermore, experts know that the brain moves upward in the skull when one flies to space, and the somatosensory cortex (which is responsible for processing sensory information) also swells in the volume of gray matter. Nevertheless, it’s been unclear how these different issues relate to each other. Plus, the effect of spaceflight on white matter has never been fully grasped.
Therefore, Seidler and her colleagues came up with a new technique that enabled them to quantify the shifts in fluid that took place within an astronaut’s brain via diffusion MRI (dMRI) scans that were able to monitor the way water molecules moved in the brain. The motion of water molecules is restricted by white matter fibre tracts in the human brain, allowing the team to get a better understanding of how the structure of white matter shifts due to spaceflight.
They were able to study both preflight and postflight dMRI scans from 15 astronauts from the years 2010 to 2015. Of those 15 astronauts, seven were part of a Space Shuttle mission that only lasted under 30 days, and eight of them finished a long space mission that lasted just under 200 days. The study looked at 12 men and three women with the average age being 47.2.
The results showed that spaceflight lessened fluid near the top of the brain, and greatly increased fluid near the bottom of the brain, this demonstrated that the distributions of fluid are changed by the way the brain moves upward within the skull. What’s more, the team discovered changes to white matter near pathways in the brain that are responsible for processing visual and spatial information, balance, vertical perception, and the control of movement.
The astronauts who suffered the most changes in white matter also had the most significant disturbances in these brain functions.
Fortunately, there were some signs that the human body can adapt. For instance, those who went into space more frequently regardless of how long the mission was or the total days in space — underwent less dramatic movements of intracranial fluid. The researchers believe this could be a sign the human body can get used to microgravity environments. However, it necessitates multiple instances of transitions between environments for this to happen.
Of course, NASA and other space agencies don’t want their astronauts to go through dangerous changes to their bodies while up in space, particularly the brain. Yet, the current problem is that there is not enough data to fully understand how bad or troublesome the changes really are. This is because of the tiny percentage of humans who have actually gone into space, and because most of those people have not spent more than a few months up there.
Seidler explained that what happens as a result of these changes to the brain is still unknown. It will be essential to have long term follow up in order to get a better understanding of how these changes in the brain might impact ageing or if there is recovery as time goes on. Seidler and her coworkers are now looking at follow-up MRI scans to figure out if there is a recovery process, but the results will take several months or even years.
Although it may seem like the movement of fluid or the changes in white matter are problematic, in an editorial published in JAMA in conjunction with the new study. The writers say it’s possible these changes are the brain’s way of getting used to a new environment, and it could represent a positive neuroadaptive response.
However, we will only know for sure after much more extensive studies.
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