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Abstract

Involuntary physical responses to vestibular stimulation are very fast. The vestibulo-ocular reflex, for example, occurs approximately 20ms after the onset of vestibular stimulation (Lorente de No, 1933, Arch Neurol Psychiat). Despite these fast responses, reaction time (RT) to the perceived onset of vestibular stimulation occurs as late as 438ms after galvanic vestibular stimulation, which is approximately 220ms later than RTs to visual, somatosensory and auditory stimuli (Barnett-Cowan Harris, 2009, Exp Brain Res). To determine whether RTs to natural vestibular stimulation are also slow, participants in the present study were passively moved forwards by .1178m (single cycle sinusoidal acceleration; 0.75m/s/s peak acceleration) using a Stewart motion platform and were asked to press a button relative to the onset of physical motion. RTs to auditory and visual stimuli were also collected. RTs to physical motion occurred significantly later (>100ms) than RTs to auditory and visual stimuli. Event related potentials (ERPs) were simultaneously recorded where the onset of the vestibular-ERP in both RT and non-RT trials occurred about 200ms or more after stimulus onset while the onset of the auditory- and visual-ERPs occurred less than 100ms after stimulus onset. All stimuli ERPs occurred approximately 135ms prior to RTs. These results provide further evidence that vestibular perception is slow compared to the other senses and that this perceptual latency may be related to latent cortical responses to physical motion.