Cue weighting and vestibular mediation of temporal dynamics in sound localization via head rotation

Abstract

Our studies have quantified the salience and weighting of dynamic acoustic cues in sound localization via head rotation. Results support three key findings: 1) low-frequency interaural time-difference (ITD) is the dominant dynamic binaural difference cue; 2) dynamic cues dominate front/rear localization only when spectral cues are unavailable; and 3) the temporal dynamics of dynamic cue processing are particular to auditory-vestibular integration. ITD dominance is shown indirectly in findings that head movements are highly effective for localizing low-frequency targets but not narrow-band high-frequency targets. Direct evidence comes from manipulation of dynamic binaural cues in spherical-head simulations lacking spectral cues. If the stimulus provides access to dominant high-frequency spectral cues, location illusions involving head-coupled source motion fail. For low-frequency targets, localization performance improves with increasing head-turn angle, but decreases with increasing velocity such that performance depends primarily on stimulus duration; ~100 ms being required for accurate front/back localization. That duration threshold only applies in dynamic localization tasks, and not in auditory-only tasks involving similar stimuli. Correct spatial interpretation of dynamic acoustic cues appears to require vestibular information about head motion, thus the temporal threshold is likely a property of vestibular-auditory integration.