Space-Brain Is Real, and It Could Affect Future Manned Missions

Before humans sent the first dogs and chimps into space, there was genuine fear: Can a living creature evolved for gravity survive in sustained zero-G? Many posited that the result would be fatal, as gas bubbles formed in the veins or stomach acid rose to eat the body from within.
Soon enough, though, it became clear that spaceflight is not, in and of itself, all that harmful to mammals, their hearts, or their brains. The biggest impact on astronauts is likely on bone density and equilibrium, both of which can be rebuilt when they return.
Now, a new study published in PNAS suggests that long periods in space could have much more profound impacts than previously believed. Looking at 26 astronauts and 24 non-astronauts, the team came to a startling conclusion: Astronauts’ brains are reliably re-seated in their skulls during spaceflight.
The shift seemed to be “backward, upward, and rotated back in the pitch direction from before to after spaceflight.” In terms of magnitude, the biggest shift was about 2.5mm. This might not seem like much, but even a few millimeters of movement near the back of the brain can cause instant unconsciousness, so small movements can clearly have big impacts.
The effect might not be easy to reverse, either. Astronauts generally find their land legs again within a couple of weeks of splashdown, but the perceived shifts took 6 months or more to recede. Worse, some elements of the changes persisted after the study concluded.
The study used a combination of data from astronauts and non-astronauts who agreed to sleep in a head-down-tilt position to mildly simulate microgravity. Both cohorts showed shifting in the brain’s position, though the astronauts seemed to have a more pronounced effect.
The researchers found that subjects with more pronounced shifts in the sensory areas of the brain had a harder time regaining their equilibrium, suggesting that these effects could affect performance.
Stints in space tend to be a bit shorter these days, with rocket launches no longer being quite as rare as in the past. Russian cosmonaut Valeri Polyakov holds the record for the longest single time spent in space, at 437 days aboard the Mir space station in the mid-90s.
In all, the study obviously didn’t find that space is secretly lethal to human brains, but it did find that space can fundamentally impact the brain. What long-term effects that could have, over years or even decades spent in space, we can only speculate.
The real question, and one that gets back to the types of worries that pervaded spaceflight at the beginning, is whether a brain could develop properly in zero-G starting at conception. Colonization of the Moon and Mars will have to advance quite a bit to make that question relevant, but it’s worth wondering: Will future mothers return planet-side for birth and early child-rearing?
Science fiction has long posited situations in which those born in space struggle to live in planetary gravity; this study may have provided some of the first concrete scientific evidence that this is a well-founded fear.
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