Perceived radial translation during centrifugation.

BACKGROUND Linear acceleration generally gives rise to translation perception. Centripetal acceleration during centrifugation, however, has never been reported giving rise to a radial, inward translation perception. OBJECTIVE To study whether centrifugation can induce a radial translation perception in the absence of visual cues. METHODS To that end, we exposed 12 subjects to a centripetal acceleration with eyes closed. To avoid confounding with angular motion perception, subjects were fist rotated on-axis, and were shifted out fast and slow only after rotation sensation had vanished. They were asked for translation direction and velocity right after the shift-out, as well as after about 60 seconds of constant centrifugation. RESULTS Independent of fast or slow shift-out, the vast statistically significant majority of trials yielded an inward radial translation perception, which velocity was constant after 60 seconds of constant centrifugation. CONCLUSIONS We therefore conclude that during centrifugation, an inward radial translation perception does exist in humans, which perception reaches a constant, non-zero value during constant rotation, lasting for at least one minute. These results can be understood by high-pass filtering of otolith afferents to make a distinction between inertial and gravitational acceleration, followed by a mere integration over time to reach a constant velocity perception.