A new study published in Frontiers in Neural Circuits is the first to
analyze the structural connectivity changes that happen in the brain after
long-duration spaceflight. The results show significant microstructural
changes in several white matter tracts such as the sensorimotor tracts. The
study can form a basis for future research into the full scope of brain
changes during human space exploration.
Our brain can change and adapt in structure and function throughout our
lives. As human exploration of space reaches new horizons, understanding the
effects of spaceflight on human brains is crucial. Previous research has
shown that spaceflight has the potential to alter both the shape and
function of an adult brain.
Through a collaborative project between the European Space Agency (ESA) and
Roscosmos, a team of international researchers, led by Dr. Floris Wuyts of
the University of Antwerp, have been studying the brains of humans traveling
to space.
Wuyts and his colleagues have, for the first time, investigated structural
changes in the brain after spaceflight at the level of deep-brain white
matter tracts.
White matter refers to the parts of the brain that are responsible for
communication between gray matter and the body and between various gray
matter regions. In short, white matter is the channel of communication of
the brain and gray matter is where information processing is done.
The learned brain
To study brain structure and function after spaceflight, the researchers
used a brain imaging technique called fiber tractography.
"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," explained Wuyts.
Wuyts and his team acquired diffusion MRI (dMRI) scans of 12 male cosmonauts
before and right after their spaceflights. They also collected eight
follow-up scans, seven months after spaceflight. The cosmonauts all engaged
in long-duration missions of an average length of 172 days.
The researchers found proof of the concept of 'the learned brain'; in other
words, the level of neuroplasticity the brain has to adapt to spaceflight.
"We found changes in the neural connections between several motor areas of
the brain," said first author Dr. Andrei Doroshin, of Drexel University.
"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."
The follow-up scans revealed that after seven months of returning to Earth,
these changes were still visible.
"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," continued
Wuyts.
The authors also find an explanation for anatomical brain shifts observed
after spaceflight.
"We initially thought to have detected changes in the corpus callosum, which
is the central highway connecting both hemispheres of the brain," explained
Wuyts. The corpus callosum borders the brain ventricles, a communicating
network of chambers filled with fluid, which expand because of spaceflight.
"The structural changes we initially found in the corpus callosum are
actually caused by the dilation of the ventricles that induce anatomical
shifts of the adjacent neural tissue," said Wuyts. "Where initially it was
thought that there are real structural changes in the brain, we only observe
shape changes. This puts the findings in a different perspective."
The future of spaceflight research
The study illustrates a need for understanding how spaceflight affects our
body, specifically via long-term research on the effects on the human brain.
Current countermeasures exist for muscle and bone loss, such as exercising
for a minimum of two hours a day. Future research may provide evidence that
countermeasures are necessary for the brain.
"These findings give us additional pieces of the entire puzzle. Since this
research is so pioneering, we don't know how the whole puzzle will look yet.
These results contribute to our overall understanding of what's going on in
the brains of space travelers. It is crucial to maintain this line of
research, looking for spaceflight induced brain changes from different
perspectives and using different techniques," concluded Wuyts.
Reference:
Doroshin A, Jillings S, et al. Brain Connectometry Changes in Space Travelers
After Long-Duration Spaceflight. Front. Neural Circuits 16:815838.
DOI: 10.3389/fncir.2022.815838