The effects of dynamic arm movements during prolonged whole-body tilt on the perception of gravitational direction

Do body movements contribute to the perception of the gravitational space? To answer this question, we investigated the influence of arm movements against gravity on the estimation of the gravitational direction or body tilt orientation. In Experiment 1, we asked the participants to perform static or dynamic arm movements during prolonged whole-body tilt and evaluated their effect on subjective visual vertical (SVV) at the tilt position (during-tilt session) and after tilting back to upright position (post-tilt session). In Experiment 2, we assessed how these arm movements at the tilt position affected subjective postural vertical (SPV). We observed that shifts of SVV induced by prolonged tilt were suppressed only by dynamic arm movements. On the other hand, SPV also shifted after prolonged tilt but was not influenced by either static or dynamic arm movements. The present results suggest that the central nervous system (CNS) utilises not only vestibular or static body somatosensory signals, but also additional cues generated by dynamic body movements for the perception of the gravitational direction.