On February 18, the journal Frontiers in Neural Circuits published a study conducted by experts from around the world as part of a joint project of the European Space Agency (ESA) and Roscosmos. This is the first major work devoted to a thorough analysis of changes in the structural connections in the human brain that occurred as a result of a long stay in space. The identified changes are associated with sensorimotor, language and visual functions. They persist for a long time and scientists do not know how long it takes to reach the preflight state.

The study involved 12 cosmonauts with an average stay on the International Space Station (ISS) of about six months. Their brains were studied using tractography or diffusion MRI before the flight (on average for 89 days) and after returning to Earth - after 10 days and 230 days. The method makes it possible to quantitatively measure the diffusion of water molecules in tissues. It is widely used to build 3D models of the brain. Due to the detailed visualization of the system of pathways (tracts of the white matter) of the brain, even the smallest microstructural changes can be detected.

The examinations were carried out from February 2014 to February 2020 on a General Electric (GE) Discovery MR750 3T MRI tomograph. The most common were changes in the tracts associated with motor and sensory functions, including the corticospinal, corticostriate, and dentoalveolar tracts. There is a theory that microgravity has a significant impact on how the brain imagines the body and controls movement. The brain adapts to changes in the environment due to its neuroplasticity. Recorded changes may support this theory.

At the same time, as scientists note, previous studies have found several specific anatomical anomalies that appeared as a result of long-term space flights, such as an increase in the ventricles of the brain, narrowing of the longitudinal fissure and dislocation of the brain. Recorded microstructural changes may be associated with these anatomical abnormalities and fluid redistribution. In particular, scientists associate the anomalies found in the corpus callosum precisely with the changing anatomy, calling it unlikely that changes will occur under the influence of neuroplasticity.

Presumably, the detected anomalies in the arcuate fascicle connecting the Block and Wernicke areas are also associated exclusively with anatomical changes. In addition, microstructural changes were recorded in the basal ganglia, sensorimotor cortex, and cerebellum.

In the course of post-flight examinations, scientists found that the normalization phase of the body is very slow, and it is still unknown how much is needed to achieve the pre-flight state, and whether it will be achieved at all. There is some normalization of the state seven months after the flight, but the residual effects from a long stay in space remained in all the subjects. The authors look forward to future studies that will bring them closer to answering these questions, as well as solve two key problems of current work - a small sample and the inability to detect effects (due to the specifics of the method) resulting from fluid shifts, changes in the anatomical shape of the brain. or neuroplasticity.

In fact, the authors cannot indicate what specifically caused these or those anomalies. This is a very important point, since the answer to this question will create suitable conditions for the crew to compensate for the negative impact of an environment hostile to humans. This problem is especially relevant for long-term space flights.

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See Brain Connectometry Changes in Space Travelers After Long-Duration Spaceflight for details in Frontiers in Neural Circuits. DOI: 10.3389/fncir.2022.815838

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