Research ArticleNEUROSCIENCE

Macro- and microstructural changes in cosmonauts’ brains after long-duration spaceflight

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Science Advances  04 Sep 2020:
Vol. 6, no. 36, eaaz9488
DOI: 10.1126/sciadv.aaz9488

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  • RE: Investigating spaceflight-induced neuroplasticity through state-of-the-art diffusion MRI
    • Steven Jillings, doctoral student, Lab for Equilibrium Investigations and Aerospace, University of Antwerp, Antwerp, Belgium
    • Other Contributors:
      • Angelique Van Ombergen, Post doctoral researcher, Department of Translational Neuroscience, University of Antwerp, Antwerp, Belgium
      • Ekaterina Pechenkova, Post doctoral researcher, Laboratory for Cognitive Research, National Research University Higher School of Economics, Moscow, Russia
      • Elena Tomilovskaya, Lab Director, Institute for Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
      • Floris Wuyts, Professor, Lab for Equilibrium Investigations and Aerospace, University of Antwerp, Antwerp, Belgium
      • Ben Jeurissen, Post doctoral researcher, imec-Vision Lab, University of Antwerp, Antwerp, Belgium

    We thank K. Hupfeld for highlighting some important aspects of studying the effect of spaceflight on the human brain. The author points toward the importance of behavioural data to complement neuroimaging findings in aiding their interpretation, as well as the delayed time of scanning after cosmonauts landed back on Earth. The author also describes previous literature that addresses neuroplasticity in response to spaceflight.

    We agree that behavioural data is very important to further characterize the neuroplastic events that occur as a result of spaceflight. Based on previous work and the current findings, the next steps comprise inclusion of specific behavioural and vestibular function biomarkers obtained in the same crew (1,2). Furthermore, in aiming to achieve a standardized protocol across different space agencies, we fully concur that combining MRI and behavioural measures is an important way to advance our knowledge in this field, as recently formulated in the 2020 Lancet Neurology opinion paper, with F. Wuyts as senior author (3).

    The concern was raised that our observation of cerebellar WM increase would result from cerebellar uplifting rather than neuroplasticity. Compression and stretching induced by a shift of the brain would result in voxel fraction (VF) changes in one direction (e.g. increases) and volume changes in the opposite direction (e.g. decreases). E.g., we attribute the gray matter VF increase and volume decrease along the superior su...

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    Competing Interests: None declared.
  • RE: Macro- and microstructural changes in cosmonauts’ brains after long duration spaceflight
    • Kathleen E. Hupfeld, doctoral student, University of Florida
    • Other Contributors:
      • Heather R. McGregor, Postdoctoral scholar, University of Florida
      • Patricia A. Reuter-Lorenz, Professor, University of Michigan
      • Rchael D. Seidler, Professor, University of Florida

    Jillings and colleagues report widespread brain structural changes among 11 cosmonauts after six-month International Space Station missions (data from two cosmonauts were acquired before and following two different flights). Their primary findings include increased cerebellar white matter (WM) volume, cerebrospinal fluid (CSF) redistribution, and altered gray matter (GM) fractions. Many of these changes approached preflight levels by seven months postflight. Strengths of this work include a seven-month follow-up MRI for 8 of the 11 cosmonauts, a well-matched control group, and correlations between CSF changes and visual acuity.

    These contributions to the spaceflight neuroimaging literature notwithstanding, several aspects of this report warrant critique. As exposure to novel environments and practicing a skill can result in WM plasticity, the reported cerebellar WM changes may reflect spaceflight-induced plasticity, as claimed by the authors. However, the absence of corresponding behavioral measures calls this interpretation into question. The authors’ interpretation is predicated on their observed post-flight WM increases in the cerebellum, a brain structure that contributes to sensorimotor function and adaptation. However, the WM increase alone is ambiguous: adjudicating whether brain changes are adaptive or dysfunctional requires examination of brain-behavior associations (1). As an illustrative example, in our past work we leveraged balance performance data to a...

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    Competing Interests: None declared.

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