Brain Connectometry Changes in Space Travelers After Long-Duration Spaceflight

Abstract

Humans undergo extreme physiological changes when subjected to long periods of weightlessness, and as we continue to become a space-faring species, it is imperative that we fully understand the physiological changes that occur in the human body, including the brain. In this study, we present findings of brain structural changes associated with long-duration spaceflight based on diffusion magnetic resonance imaging (dMRI) data. Twelve cosmonauts who spent an average of six months aboard the International Space Station (ISS) were scanned in an MRI scanner pre-flight, ten days after flight, and at a follow-up time point seven months after flight. We performed differential tractography, a technique that confines white matter fiber tracking to voxels showing microstructural changes. We found significant microstructural changes in several large white matter tracts, such as the corpus callosum, arcuate fasciculus, corticospinal, corticostriatal, and cerebellar tracts. This is the first paper to use fiber tractography to investigate which specific tracts exhibit structural changes after long-duration spaceflight and may direct future research to investigate brain functional and behavioral changes associated with these white matter pathways.

Monitoring the Impact of Spaceflight on the Human Brain

“…Microstructural changes and damage in white matter have been associated with neurocognitive deficits in high-altitude pilot populations [ 5 , 16 ]. Long-term isolation in deep space can lead to a whole suite of long-lasting changes from a reduction in performance in the brain areas such as the sensorimotor network where microstructural changes are observed post-flight [ 17 ].…”

“…In-flight monitoring technologies would enable investigators to measure changes in the CNS while in the deep space environment and reduce the possibility for bias or influence by other factors (i.e., changes associated with orthostatic intolerance) upon leaving the deep space environment [ 19 , 20 ]. In addition, a delay in the imaging of the brain post-exposure can have a significant impact on the estimation of the true effect of deep space on the brain [ 17 ]. Several candidates for technologies for brain function monitoring applicable to spaceflight are described below.…”

“…Spaceflight studies have revealed significant microstructural changes in several large white matter tracts, including the corpus callosum, arcuate fasciculus, corticospinal, corticostriatal, and cerebellar tracts [ 17 ]. In microgravity analog environments, the decrease in extracellular free water in the post-central gyrus and precuneus was negatively correlated with balance changes.…”

Future research directions to identify risks and mitigation strategies for neurostructural, ocular, and behavioral changes induced by human spaceflight: A NASA-ESA expert group consensus report

“…In the past 6 years, substantial evidence has accumulated that spaceflight affects human brain structure ( Koppelmans et al, 2016 ; Roberts et al, 2017 ; Van Ombergen et al, 2018 , 2019 ; Lee et al, 2019b ; Riascos et al, 2019 ; Hupfeld et al, 2020 , 2022 ; Jillings et al, 2020 ; Kramer et al, 2020 ; Roy-O’Reilly et al, 2021 ; Barisano et al, 2022 ; Doroshin et al, 2022 ). These changes include an upward shift of the brain within the cranial compartment, ventricular expansion, perivascular space changes and white matter alterations.…”

Does heart rate variability reflect brain plasticity as a likely mechanism of adaptation to space mission?

“…In addition, microstructural changes occurring during a space mission in sensorimotor pathways, including tracts connecting the cerebellum, as well as within the corpus callosum, inferior fronto-occipital, and arcuate fascicles, may reflect various sources of space flight effects on the brain, including fluid displacement effects, structural brain changes and neuroplasticity (Doroshin et al, 2022).…”