The effect of head turn velocity on Cross-coupled Stimulation during centrifugation

Abstract

Artificial Gravity (AG) has been suggested as a potential countermeasure to the deleterious physiologic effects of long-duration space flight. Short-radius centrifugation (SRC) provides a practical means of producing AG, though perceptual side-effects may potentially limit its operational feasibility. Head-turns in the rotating environment of SRC produce Cross-coupled Stimulation (CCS), which the subject perceives as a tumbling sensation. Acutely, the CCS tumbling sensation is nauseagenic, though adaptation has been shown to diminish this detriment over time. The force environment of CCS suggests that the head-turn velocity plays a role in determining the stimulus magnitude, though the degree to which has not been characterized. In order for SRC to be an operationally viable alternative for AG, it must be shown that the motion sickness symptoms can be controlled without sacrificing adaptation. Modulation of head turn velocity has been suggested as a means to that end. A total of 23 subjects were subjected to right quadrant head-turns of 8 different velocities while spinning at 19 and 23 RPMs in the rotating environment of SRC.

(cont.) The perceptual effects were characterized with subjective and objective metrics, investigating the acute differences between velocities as well as the chronic effects on adaptation. The following key results were obtained: 1. A threshold of HT Velocity exists above which an asymptotic perceptual response is observed, and below which the resulting perceptual response diminishes at a logarithmically increasing rate. 2. The effects of HT Velocity are independent of HT direction, with differing head-turn directions produce contextually specific stimuli. 3. HT velocity modulation could provide a practical means of incremental adaptation.