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Abstract

In contrast to other senses, the latency of vestibular sensation has not been well investigated. We therefore measured the perceived timing of vestibular sensation relative to visual, tactile and auditory stimuli. Three types of vestibular stimulation were used: galvanic vestibular stimulation (GVS), passive head movements (HMp) and active head movements (HMa). Temporal order (TOJ) and simultaneity judgments (SJ) and reaction times (RTs) were made relative to full-field flashes, 50ms bursts of white noise, or of vibration of the finger tip. TOJs and SJs between vestibular and other sensory stimuli required the vestibular stimulus to occur ~160ms before other sensory stimuli for GVS (Fig. 1a), ~50ms before for HMp (Fig. 1b) and ~80ms before for HMa (Fig. 1c) in order for the pairs to be perceived as simultaneous. RTs to GVS-induced illusory head movement (438ms) were significantly longer than RTs to touch (245ms), light (220ms) or sound (197ms) (Fig. 1d) but not by enough to predict the TOJ and SJ results (Fig. 1e). The largely uncompensated lag in vestibular sensation probably reflects the fact that the vestibular system rarely works alone. The short latency eye and balance motor responses traditionally associated with the vestibular system are divorced from the perceptual correlates.