Click to Enlarge: The brain shows positive and negative correlations between global connectivity and cumulative flight hours. Positive correlations between ICC values and flight hours are illustrated in green, whereas negative correlations are illustrated in magenta. A threshold of p < 0.005 uncorrected at the voxel-level and p < 0.05 family-wise error rate at the cluster-level were applied. Age was regressed out of the analysis. Plots illustrate the average ICC values of all clusters, showing positive correlations (left) and negative correlations (right) with flight hours. Source: Frontiers in Physiology
ANTWERP, BELGIUM — A new international study is raising concerns about neurologic effects on U.S. airborne warfighters and Space Force guardians alike.
The study published in the journal Frontiers in Physiology found that the brains of F16 fighter pilots show a variety of functional brain connectivity changes and sheds light on the effects of space travel on astronauts.
Belgian researchers sought to detect functional brain connectivity differences in fighter pilots compared to nonpilots. The study’s goal was to provide insights into how exposure to altered gravity levels affects neuroplasticity, a process in which the brain alters its function and structure to adapt to changing environments. It was touted as the first study to investigate functional brain connectivity in fighter pilots.1
Using resting-state functional magnetic resonance imaging (MRI) data, the researchers examined the brains of F16 fighter pilots and assessed functional brain connectivity changes with increasing flight experience.
Participants in the study were Belgian F16 fighter pilots, ages 18 to 65, who were recruited from the Belgian Air Force. Ten male fighter pilots were included (mean age 29) who had an average of 1,025 hours of flight experience in an F16 fighter jet. A control group of 10 adults with no experience in flying was included and matched for age, gender and educational level.
Pilots were excluded from the study if they had neurological disease, medication with effects on the central nervous system, excessive alcohol and/or drug use, vestibular problems, jetlag (at least one week after transcontinental flight/mission) and at least 24 hours since last exposure to high g-levels.
The researchers have been studying the effect of space flight and microgravity on the human brain and equilibrium system for many years and were the first to publish on this topic in 2016. F16 fighter pilots experience frequent alterations of G-forces, somewhat similar to astronauts.
“We therefore studied F16 fighter pilots as one of the few populations who experience altered g-levels to investigate its effect on the brain in parallel to our research in astronauts,” Steven Jillings, PhD, a senior researcher in the Lab for Equilibrium Investigations and Aerospace at the University of Antwerp in Antwerp, Belgium, told U.S. Medicine.
The study’s results reveal how the brain can adapt to altered G-levels.
“We found various connectivity changes,” Jillings explained in an email. “We found that the functional connectivity increased between a region that deals with equilibrium information and a region that deals with visual information. The equilibrium and visual systems are known to interact closely in order to provide a sense of your body movements with respect to the environment, as well as to maintain gaze stabilization.”
These brain regions play a role in gravity-dependent functions. Therefore, experiencing altered G-levels triggers adaptation in regions related to processing gravity-related information, Jillings added.
The researchers also found connectivity changes in relation to flight time, meaning that pilots acquire brain adaptations by experience. Various regions in the brain showed altered functional connectivity changes based on the amount of time the pilot has flown in a F16 jet. The more a pilot has flown, the higher or lower the connectivity between these regions and the rest of the brain.
In addition, the study discovered that functional connectivity increased between the left and right angular gyrus. The angular gyrus is known to play a role in verticality perception, Jillings explained in an email.
There are very few papers on the brains of fighter pilots, Floris L. Wuyts, PhD, head of the Lab for Equilibrium Investigations and Aerospace at the University of Antwerp in Antwerp, Belgium, told U.S. Medicine. The study’s findings suggest altered motor, vestibular and multisensory processing in the brains of fighter pilots, possibly reflecting coping strategies to altered sensorimotor demands during flight.
“We hope that this research adds to the general understanding of brain neuroplasticity and that studies in these rather unique populations like pilots and astronauts may improve the quality of life of patients suffering from lacking neuroplasticity,” Wuyts wrote in an email.
Understanding how adaptations in the brain occur under changing gravitational conditions is increasingly important with the surge in plans for future space missions to the moon, Mars and eventually beyond. This study’s results, which are applicable to humans traveling to space, are relevant for future long-duration missions, such as to the moon with 0.16 g or to Mars with 0.38 g, where the space crew will be exposed to varying levels of gravitational force across the span of the mission, according to the study.
Pilots offer a good model on Earth to investigate how challenging gravitational environments lead to sensory adaptations. For instance, during in-flight coordinated turns, fighter pilots undergo a body tilt in the roll plane and simultaneously experience centrifugal forces.
“Knowing if and how the brain adapts to altered g-levels will be important in light of space travel, during which gravity level changes occur as well,” Jillings wrote in an email. “It may also be helpful in understanding adaptation to disorders of the equilibrium system. There are several chronic equilibrium disorders in which patients suffer from various types of dizziness. These same regions may also play a key role in understanding these disorders.”
“The clinical evidence that vertigo originates in the brain is growing,” Wuyts added. “Hence, these same regions may also play a key role in understanding these disorders. Once we can identify biomarkers of neuroplasticity, we have tools to search for solutions to alter or enhance connectivity in cases where it is not evolving the way it should be.”
This study could aid in providing better training programs for pilots or astronauts. Further research is needed to understand how the brain adapts to overcome various sensory and sensorimotor challenges during (space) flight. However, this research is restricted because the populations that can be tested in this setting, such as space crew, parabolic flight participants and fighter pilots, are rare.
- Radstake WE, Jillings S, Laureys S, Demertzi A, Sunaert S, Van Ombergen A, Wuyts FL. Neuroplasticity in F16 fighter jet pilots. Front Physiol. 2023 Feb 15;14:1082166. doi: 10.3389/fphys.2023.1082166. PMID: 36875024; PMCID: PMC9974643.
