Eye position determines audiovestibular integration during whole‐body rotation

Abstract

When a sound is presented in the free field at a location that remains fixed to the head during whole-body rotation in darkness, it is heard displaced in the direction opposing the rotation. This phenomenon is known as the audiogyral illusion. Consequently, the subjective auditory median plane (AMP) (the plane where the binaural difference cues for sound localization are perceived to be zero) shifts in the direction of body rotation. Recent experiments, however, have suggested opposite AMP results when using a fixation light that also moves with the head. Although in this condition the eyes remain stationary in the head, an ocular pursuit signal cancels the vestibulo-ocular reflex, which could induce an additional AMP shift. We tested whether the AMP is influenced by vestibular signals, eye position or eye velocity. We rotated subjects sinusoidally at different velocities, either in darkness or with a head-fixed fixation light, while they judged the laterality (left vs. right with respect to the midsagittal plane of the head) of broadband sounds presented over headphones. Subjects also performed the same task without vestibular stimulation while tracking a sinusoidally moving visual target, which mimicked the average eye-movement patterns of the vestibular experiments in darkness. Results show that whole-body rotation in darkness induces a shift of the AMP in the direction of body rotation. In contrast, we obtained no significant AMP change when a fixation light was used. The pursuit experiments showed a shift of the AMP in the direction of eccentric eye position but not at peak pursuit velocity. We therefore conclude that the vestibular-induced shift in average eye position underlies both the audiogyral illusion and the AMP shift.

The moving minimum audible angle is smaller during self motion than during source motion

“…Strict geometric rules govern how the position of real world acoustic signals change with respect to the position and angle of the head (Wallach, 1940), none of which are in any way affected by the position of the eyes, but eye position has been shown to affect spatial localization (Lewald and Ehrenstein, 1996; Lewald, 1997, 1998). Furthermore, eye position influences audiovestibular interaction as well (Van Barneveld and Van Opstal, 2010), arguing that on some level that the primary driver of self-motion subtraction may be the eye movement itself. Certainly the best understood auditory spatial coordinate transformation is that which is driven by eye position.…”

Distortion of auditory space during visually induced self-motion in depth

“…This is known as the “audiogyral illusion” (Münsterberg and Pierce, 1894; Clark and Graybiel, 1949; Arnoult, 1950; Lester and Morant, 1970). Several recent reports showed that the direction of displacement was reversed (i.e., in the direction of vestibular stimulation) when listeners were exposed to semicircular stimulation that was too weak to induce an illusory kinesthetic sense (i.e., explicit postural and movement information) (Lewald and Karnath, 2000, 2001; see also van Barneveld and John Van Opstal, 2006). Rapid head turns can also lead to the distortion of auditory space in the perisaccadic interval, just like visual localization during or immediately before saccadic eye movements (Cooper et al, 2008; Leung et al, 2008).…”

Absence of Spatial Updating when the Visuomotor System Is Unsure about Stimulus Motion

“…Experiments were conducted in a completely dark room. The subject was seated in a computer-controlled vestibular stimulator (Van Barneveld and Van Opstal, 2010), with the head firmly stabilized in an upright position with a padded adjustable helmet. We measured chair position with a digital position encoder at an angular resolution of 0.04°.…”