Artificial gravity—head movements during short-radius centrifugation: Influence of cognitive effects

Short-ra dius centrifugation is a potential countermeasure against the effects of prolonge dweightlessness. Hea dmovementsin a rotating environment, however, induce serious side effects: inappropriate vestibular ocular reflexes (VOR), body-tiltillusions an dmotion sickness in duce dby cross-couple daccelerations on a rotating platform. These are well pre dicte dby asemicircular canal model. The present study investigates cognitive effects on the inappropriate VOR and the illusory sensationsexperience dby subjects rotating on a short-ra dius centrifuge (SRC). Subjects(N=19)were place dsupine on a rotatinghorizontal be dwith their hea dat the center of rotation. To investigate the extent to which they coul dcontrol their sensationsvoluntarily, subjects were aske dalternatively to “fight” (i.e. to try to resist an dsuppress) those sensations, or to “go” with(i.e. try to enhance or, at least, acquiesce in) them. The only significant effect on the VOR of this cognitive intervention wasto diminish the time constant characterizing the decay of the nystagmus in subjects who had performed the “go” (rather thanthe “fight”) trials. However, illusory sensations, as measure dby reporte dsubjective intensities, were significantly less intenseduring the “fight” than during the “go” trials. These measurements also verified an asymmetry in illusory sensation knownfrom earlier experiments: the illusory sensations are greater when the hea dis rotate dfrom right ear down (RED) to noseup (NU) posture than from NU to RED. The subjects habituated, modestly, to the rotation between their first and secondsequences of trials, but showe dno better (or worse) suppression of illusory sensations thereafter. No significant difference inhabituation was observe dbetween the “fight” an d“go” trials