New research sheds light on the effects of space travel on astronauts’ brains. The study, published in Scientific Reportsfound that long space missions and shorter breaks between missions can lead to changes in the fluid in the brain that may not return to normal before the next space flight.
The motivation behind this study was to understand the effects of space travel on the human brain, specifically the changes in fluid dynamics and structural morphology. Space travel poses various hazards such as radiation exposure, microgravity and isolation, which can affect the human body in different ways. Previous studies have shown that space travel induces changes in the brain, including expansion of the ventricles (cavities filled with CSF) and shifts in gray and white matter volume.
The researchers wanted to study how these brain changes differ depending on the duration of space missions and the astronauts’ previous flight experience. They wanted to understand whether longer missions or shorter recovery periods between missions have a greater impact on the brain. This knowledge is crucial because when planning future long-term space missions, such as to Mars, it is important to understand the potential risks and effects on astronauts’ brains.
“Microgravity is a state in which we have not yet evolved – it is fascinating to see how the nervous system changes and adapts in this context,” said study author Rachael Seidler, professor of applied physiology and kinesiology and professor of neurology at the University of Florida.
For the study, the researchers used magnetic resonance imaging (MRI) to scan the brains of 30 astronauts before and after their space flights. The sample included astronauts completing two-week missions, six-month missions, and longer missions. They collected T1-weighted anatomical scans and diffusion-weighted MRI (dMRI) scans of the astronauts.
The MRI scans were obtained using a 3 Tesla MRI scanner at the University of Texas Medical Department. The T1-weighted images provided structural information about the brain, while the dMRI scans allowed the researchers to analyze white matter microstructure and fluid distribution in the brain.
Seidler and her colleagues found that longer space flights resulted in increased enlargement of certain areas in the brain called ventricles, which are filled with cerebrospinal fluid. However, that growth seemed to slow down after about six months in space. The study also found that astronauts with more flight experience had less ventricular enlargement than those who were new to spaceflight.
“Structural brain changes that occur during spaceflight vary based on the time spent in space,” Seidler told PsyPost. “Those who travel a few weeks notice little to no change in ventricular volume – good news for those traveling on short space trips.” Those who have spent about 6 months in space have increased ventricular volume. Those that lasted about a year showed no further changes, which may bode well for even longer-planned missions like Mars.”
The length of time between successive space missions, so-called inter-mission intervals, also played a role in the brain changes. Astronauts who had less than three years of recovery time between missions showed little to no ventricular enlargement after their current mission, while those with three or more years of recovery time showed ventricular enlargement.
The researchers theorize that if the time between spaceflights is less than three years, there may not be enough time for the ventricles to recover and be able again to absorb the increased fluid in the brain. This keeps the ventricles enlarged when astronauts return to space within this shorter time span.
“I was surprised to see that it can take about three years for the brain to return to its pre-flight state after a prolonged flight,” Seidler said.
There are some limitations to consider in this study. The post-flight MRI scans were taken an average of about six days after the astronauts returned to Earth, with some scans taken a day and others as late as 20 days after landing. Although the researchers took into account the time lag between landing and the post-flight MRI scan in their analyses, this timing may have influenced the observed brain changes.
“We don’t yet understand the long-term consequences of these brain changes for health and human performance,” added Seidler. “I am currently conducting a new study in which we will follow individuals for up to five years after flight.”
The study “Effects of space travel experience on human brain structure” was authored by Heather R McGregor, Kathleen E Hupfeld, Ofer Pasternak, Nichole E Beltran, Yiri E De Dios, Jacob J Bloomberg, Scott J Wood , Ajitkumar P .Mulavara, Roy F. Riascos, Patricia A. Reuter-Lorenz, and Rachael D. Seidler.