Resilience of otolithic reflex to gravitational changes

Tess Bonnard, Anoa Morello, Emilie Doat, Jean-René Cazalets, Dominique Guehl, Etienne Guillaud
npj Microgravity. 2026-04-27; 12(1):
DOI: 10.1038/s41526-026-00599-9

Bonnard T(1), Morello A(1), Doat E(1), Cazalets JR(1), Guehl D(2), Guillaud E(3).

Author information:
(1)Univ. Bordeaux, CNRS, INCIA, UMR 5287, Bordeaux, France.
(2)Univ. Bordeaux, CNRS, IMN, UMR 5293, Bordeaux, France.
(3)Univ. Bordeaux, CNRS, INCIA, UMR 5287, Bordeaux, France.
.

Otoliths within the vestibular system detect the magnitude and orientation of
gravity and provide a reference frame for spatial orientation. Although
vestibular processing has been studied in altered gravity, little is known about
the initial minutes of exposure, when space motion sickness emerges. This study
investigated whether otolithic detection is modified in different gravities or
by sensory conflicts. Otolithic function was assessed using vestibular-evoked
myogenic potentials (VEMPs) recorded from three muscles, reflecting utricular
and saccular activity. VEMPs were measured during parabolic flight to assess
modified gravity and longitudinal effects associated with otolitho-canalar
conflict, and before and after a virtual reality exposure inducing
visuo-vestibular conflict. Otolithic reflexes were largely resistant to gravity
changes, sensory conflicts, and motion sickness. VEMP amplitudes remained
stable, while oVEMP latencies increased ( ~ 1 ms in microgravity; ~0.4 ms
post-flight). No differences were observed between motion-susceptible and
non-susceptible participants. Baseline otolithic sensitivity predicted
cyber-sickness susceptibility but not space-sickness.