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What Does Space Do to an Astronaut's Brain?

The Apollo 11 anniversary really had my neurons firing.

Last night, on the 50th anniversary of the Apollo 11 launch, I strolled down to the National Mall for a show that paid tribute to the groundbreaking 1969 mission when man first set foot on the Moon.

The Apollo 11 rocket, the Saturn V, was projected on the side of the Washington Monument and—true to scale at 363 feet—towered above the thousands of spectators below. As the launch countdown began and a hush descended over the crowd, there was a brief moment where I thought: This whole “going to space” thing could be dangerous for the astronauts’ brains, right? How bad is spending time in space, really?

Ruben Rodriguez, used with permission
Source: Ruben Rodriguez, used with permission

Blame my background in neuroscience, or the unbearable heatwave that had temperatures still hovering around 100ºF at 10 in the evening, but my brain kept traveling back to those questions. So here we are.

The good news is that there are a lot of researchers out there asking similar things, and astronaut health research—brain-related and otherwise—is ongoing.

I was intrigued by one recent study in particular. Earlier this year, a group of researchers investigated how white matter distribution in our brains could be affected by spaceflight. Although their sample size was relatively small, their findings provide a good baseline for future work.

So first, let’s briefly talk about the white matter. You’ll find white matter in your central nervous system, which includes your brain, in areas mostly made up of myelinated axons—regions of neurons coated in a fatty substance called myelin. Myelin not only gives white matter its color, but it is also critical for signaling between the cells in your brain called neurons. That signaling allows different parts of your brain to communicate with one another and your body to function normally. White matter breaks down as we age, in some people more than others, and as it does we experience changes in things like memory, thought processing, and balance.

These researchers analyzed diffusion magnetic resonance imaging (dMRI) data from 15 astronauts—12 men, 3 women—that had been collected between 2010 and 2015, both pre- and post-flight. A dMRI is like an MRI, where the goal is to get detailed pictures of soft tissues (like your brain) but it uses the diffusion of water molecules to generate contrast in those pictures, allowing you to see structures that restrict the movement of that water—like white matter.

The researchers found a significant increase in the amount of fluid in the frontal, temporal, and occipital lobes of the astronauts’ brains, but a decrease in the posterior part of the cranial vertex—toward the back of the head. This shift in fluid means that the astronauts' brains were floating higher in their skulls than usual, the potential risks of which are still unknown. In addition to changes in fluid distribution, all astronauts showed significant changes in white matter throughout their brains—in regions like the superior longitudinal fasciculus (SLF), a fiber tract that runs along both hemispheres of the brain and is so important for things like working memory and regulating motor behaviors. Astronauts did show changes in balance before and after spaceflight, and that's thought to be the result of changes to white matter in the superior longitudinal fasciculus.

This study, and others before it, have given us an idea of how the brains of astronauts could change while in space, but in terms of the duration of those changes, as well as the long-term consequences, we’re still mostly in the dark.

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