Artificial gravity: Head movements during short-radius centrifugation

Short-radius centrifugation is a potential countermeasure to long-term weig htlessness. Unfortunately, head movements in a rotating environment induce serious discomfort, non-compensatory vestibulo-ocular reflexes, and subject ive illusions of body tilt. In two experiments we investigated the effects of pitch and yaw head movements in participants placed supine on a rotating bed with their head at the center of rotation, feet at the rim. The vast m ajority of participants experienced motion sickness, inappropriate vertical nystagmus and illusory tilt and roll as predicted by a semicircular canal model. However, a small but significant number of the 28 participants exper ienced tilt in the predicted plane but in the opposite direction. Heart rat e was elevated following one-second duration head turns. Significant adapta tion occurred following a series of head turns in the light. Vertical nysta gmus, motion sickness and illusory tilt all decreased with adaptation. Cons equences for artificial gravity produced by short-radius centrifuges as a c ountermeasure are discussed. (C) 2001 Published by Elsevier Science Ltd.