Self-motion reproduction can be affected by associated auditory cues.

Successful locomotion through space requires precise estimation of the direction and distance travelled. Previous studies have shown that humans can use velocity information arising from visual, vestibular and somatosensory signals to reproduce passive linear displacements. In the present study we investigated whether also associated auditory velocity cues are used for distance estimation. Subjects had to reproduce (active condition) the distance of a previously seen sequence of simulated linear motion (passive condition) across a ground plane. During both, the passive and active displacement, they heard a tone with a frequency being proportional to the simulated speed (test trials). In some trials the relationship between optical velocity and tone frequency was differently scaled during the active displacements, i.e., the frequency of the tone was either higher or lower than in the passive displacement (catch trials). In test trials, subjects reproduced distances quite accurately. In catch trials, however, subjects' performance was disturbed: when the frequency was lower subjects used higher speeds, resulting in a substantial overshoot of travelled distance, whereas a higher frequency resulted in an undershoot of travelled distance. Our results clearly show that during self-motion tone frequency can be used as a velocity cue and helps to update positional information over time.