Three-dimensional analysis of the vestibulo-ocular reflex and the ability to distinguish the direction of centripetal acceleration in humans during eccentric rotation with the right ear facing downwards

Abstract

This study was conducted to evaluate the linear vestibulo-ocular reflex (lVOR) mediated by the saccule, and to investigate the relationship between the lVOR and the ability to distinguish the direction of centripetal acceleration during centric and eccentric rotation. Participants sat on a chair in darkness, with the right ear facing downwards, either directly above the center of rotation, or with their nose out, nose in, right shoulder out, or left shoulder out against the center of rotation (eccentric rotation). Participants were given no information about the chair position, and were rotated sinusoidally at 0.1–0.7 Hz. Three-dimensional eye movements during rotation were analyzed. Participants were asked to describe the position of the chair after rotation. Correctly reporting the five possible chair positions requires recognition of the direction of centripetal acceleration. We analyzed the rate of correct answers to assess participants’ ability to identify the direction of centripetal acceleration. lVOR mediated by the saccule was observed only at high rotational frequencies. The rate of correct answers was higher at high rotational frequencies than that at low rotational frequencies. These results indicate that high rotational frequency is important for both lVOR mediated by the saccule and distinguishing the direction of centripetal acceleration.