Vestibular evoked potentials from the vertical semicircular canals in humans evoked by roll-axis rotation in microgravity and under 1-G.

Vestibular evoked potentials during rotation of human subjects around their naso-occipital roll-axis were recorded. The effect of stimulating the vertical semicircular canals and otolithic stimulation was investigated by comparing the evoked potentials obtained under the 1-G condition with those recorded in microgravity conditions. Subjects lay on their side with the head in the center of rotation and were tilted feet upward (roll up) and back into the lying position (roll down). The microgravity environment was created by parabolic flight maneuvers. In microgravity, transient bell-shaped negativity was recorded for roll up and down motion. In the 1-G condition the potentials were superimposed on sustained components, probably due to additional otolithic stimulation. It seems to be possible to separate the evoked responses in a transient canal response and a sustained otolithic response. The results are encouraging with respect to the goal of developing a tool for the selective assessment of canal and otolithic responses of the vestibular system. Copyright 2002 Elsevier Science B.V.