As part of her εpsilon mission aboard the International Space Station, ESA astronaut Sophie Adenot is taking part in the Brain-DTI experiment, which investigates how the brain adapts to life in microgravity, and how it recovers once astronauts return to Earth.
Brain-DTI uses a suite of MRI techniques to study the brain at structural, anatomical and functional levels. First, Diffusion Tensor Imaging (DTI) tracks how water molecules move through brain tissue, allowing researchers to map neural pathways and detect changes in the brain's white matter. Resting-state functional MRI (rs-fMRI) then reveals how different brain regions communicate with one another by measuring the blood oxygenation level dependent (BOLD) signal. Complementing these, standard anatomical sequences allow researchers to measure how much the brain shifts within the skull during spaceflight, how much the ventricles inflate and how cerebrospinal fluid is redistributed as part of the broader fluid shift that occurs in microgravity. Together, these methods provide a comprehensive picture of neuroplasticity: the brain's capacity to reorganise itself in response to new environments.
The fluid redistribution data gathered by Brain-DTI also feeds into research on Spaceflight Associated Neuro-ocular Syndrome (SANS), a condition observed in some astronauts that can impair eyesight during long-duration missions as well as cause other issues with the eye and brain. SANS is thought to be linked to increased pressure in the fluid surrounding the brain and spinal cord, which can cause the eyeball to flatten. BRAIN-DTI researchers aim to uncover the connections between these phenomena, with implications that extend well beyond human spaceflight.
Spaceflight poses an extraordinary challenge to the human brain. In microgravity, the vestibular system – which governs our sense of balance, orientation and motion – receives sensory inputs that are fundamentally different from anything experienced on Earth. Astronauts must adapt to this altered environment, a process that can initially manifest as space motion sickness, spatial disorientation and other sensory conflicts.
This very challenge makes spaceflight an unparalleled opportunity for neuroscientists. By comparing brain scans collected before and after a mission, and correlating them with astronauts' in-flight experiences and symptoms, researchers can identify biological markers of neuroplasticity under controlled, reproducible conditions.
Since its first scans in 2013, BRAIN-DTI has grown into the most extensive neuroimaging database in the history of human spaceflight.
"Since 2013, we've collected brain MRIs from around 50 astronauts and cosmonauts, making BRAIN-DTI the biggest neuroimaging study in human spaceflight," says Principal Investigator Prof. Dr. Floris Wuyts of the University of Antwerp. "The findings are already helping people with disorders linked to dizziness and vertigo today, and are shedding light on the fundamental mechanisms behind vestibular diseases and recovery.
"Obtaining large datasets is essential to reach statistical significance, and in space physiology, large numbers are very difficult to achieve. That is why the BRAIN-DTI team is so privileged that the entire Crew-12 team and the entire Expedition 75 crew participated in this experiment. Each additional astronaut contributes valuable data, and the more female astronauts we can include in the study, the better, because we still don't know how large any sex differences may be, if they exist at all. I also want to stress that BRAIN-DTI is a truly international team, with experts from Belgium, Germany, Italy, Russia and several other countries."
Because the brain begins readjusting to Earth's gravity almost immediately after landing, post-flight scans must be collected as quickly as possible. Three MRI sessions were carried out at DLR’s :envihab facility, located next to the European Astronaut Centre in Cologne, Germany, within the first two weeks after Sophie Adenot’s return from her 237-day mission.
The multiple timepoints will allow researchers to determine whether the brain's readaptation follows a linear, exponential or more complex trajectory. A final scan is planned six months after her return, to assess how long full neurological recovery takes after such an extended stay in space.
As Prof. Wuyts notes: "Eight months in space has a profound impact on the human body, and full recovery to the pre-flight state takes time." BRAIN-DTI is helping scientists understand exactly how long, and why.
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