title: The basis for using bone-conducted vibration or air-conducted sound to test otolithic function.
abstract: Extracellular single neuron recordings of primary vestibular neurons in Scarpa's ganglion in guinea pigs show that low-intensity 500 Hz bone-conducted vibration (BCV) or 500 Hz air-conducted sound (ACS) activate a high proportion of otolith irregular neurons from the utricular and saccular maculae but few semicircular canal neurons. In alert guinea pigs, and humans, 500 Hz BCV elicits otolith-evoked eye movements. In humans, it also elicits a myogenic potential on tensed sternocleidomastoid muscles. Although BCV and ACS activate both utricular and saccular maculae, it is possible to probe the functional status of these two sense organs separately because of their differential neural projections. Saccular neurons have a strong projection to neck muscles and a weak projection to the oculomotor system. Utricular afferents have a strong projection to eye muscles. So measuring oculomotor responses to ACS and BCV predominantly probes utricular function, while measuring neck muscle responses to these stimuli predominantly probes saccular function.
authors.affiliation: Vestibular Research Laboratory, School of Psychology, University of Sydney, Sydney, New South Wales, Australia. ianc@psych.usyd.edu.au
authors.forename: I S
authors.initials: IS
authors.lastname: Curthoys
authors.forename: V
authors.initials: V
authors.lastname: Vulovic
authors.forename: A M
authors.initials: AM
authors.lastname: Burgess
authors.forename: E D
authors.initials: ED
authors.lastname: Cornell
authors.forename: L E
authors.initials: LE
authors.lastname: Mezey
authors.forename: H G
authors.initials: HG
authors.lastname: Macdougall
authors.forename: L
authors.initials: L
authors.lastname: Manzari
authors.forename: L A
authors.initials: LA
authors.lastname: McGarvie
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001844:Bone Conduction / Q000502:physiology; D004576:Electromyography; D005133:Eye Movements / Q000502:physiology; D006168:Guinea Pigs; D006801:Humans; D008575:Meniere Disease / Q000503:physiopathology; D009334:Neck Muscles / Q000502:physiology; D009801:Oculomotor Muscles / Q000294:innervation / Q000502:physiology; D010037:Otolithic Membrane / Q000294:innervation* / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D012444:Saccule and Utricle / Q000502:physiology; D012665:Semicircular Canals / Q000502:physiology; D014724:Vestibular Function Tests / Q000379:methods*; D014725:Vestibular Nerve / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology / Q000503:physiopathology; D014732:Vibration