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.
