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Front Physiol. 2019 Jul 4;10:761. doi: 10.3389/fphys.2019.00761. eCollection 2019.

Alterations of Functional Brain Connectivity After Long-Duration Spaceflight as Revealed by fMRI.

Author information

1
Laboratory for Cognitive Research, Higher School of Economics, Moscow, Russia.
2
Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.
3
Radiology Department, Federal Center of Treatment and Rehabilitation, Moscow, Russia.
4
Medical Research and Educational Center, Lomonosov Moscow State University, Moscow, Russia.
5
Lab for Equilibrium Investigations and Aerospace, Faculty of Science, University of Antwerp, Antwerp, Belgium.
6
iMec/Vision Lab, Faculty of Science, University of Antwerp, Antwerp, Belgium.
7
Coma Science Group, GIGA Consciousness Research Centre, Neurology Department, University Hospital of Liège, Liège, Belgium.
8
Gagarin Cosmonauts Training Center, Star City, Russia.

Abstract

The present study reports alterations of task-based functional brain connectivity in a group of 11 cosmonauts after a long-duration spaceflight, compared to a healthy control group not involved in the space program. To elicit the postural and locomotor sensorimotor mechanisms that are usually most significantly impaired when space travelers return to Earth, a plantar stimulation paradigm was used in a block design fMRI study. The motor control system activated by the plantar stimulation involved the pre-central and post-central gyri, SMA, SII/operculum, and, to a lesser degree, the insular cortex and cerebellum. While no post-flight alterations were observed in terms of activation, the network-based statistics approach revealed task-specific functional connectivity modifications within a broader set of regions involving the activation sites along with other parts of the sensorimotor neural network and the visual, proprioceptive, and vestibular systems. The most notable findings included a post-flight increase in the stimulation-specific connectivity of the right posterior supramarginal gyrus with the rest of the brain; a strengthening of connections between the left and right insulae; decreased connectivity of the vestibular nuclei, right inferior parietal cortex (BA40) and cerebellum with areas associated with motor, visual, vestibular, and proprioception functions; and decreased coupling of the cerebellum with the visual cortex and the right inferior parietal cortex. The severity of space motion sickness symptoms was found to correlate with a post- to pre-flight difference in connectivity between the right supramarginal gyrus and the left anterior insula. Due to the complex nature and rapid dynamics of adaptation to gravity alterations, the post-flight findings might be attributed to both the long-term microgravity exposure and to the readaptation to Earth's gravity that took place between the landing and post-flight MRI session. Nevertheless, the results have implications for the multisensory reweighting and gravitational motor system theories, generating hypotheses to be tested in future research.

KEYWORDS:

brain plasticity; cosmonauts; fMRI; functional connectivity; microgravity; spaceflight; support stimulation; vestibular function

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