title: Effect of stimulus rise-time on the ocular vestibular-evoked myogenic potential to bone-conducted vibration.
abstract: OBJECTIVE
  The negative potential at 10 msec (called n10) of the ocular vestibular-evoked myogenic potential (oVEMP) recorded beneath the eyes in response to bone-conducted vibration (BCV) delivered to the skull at the midline in the hairline (Fz) is a new indicator of otolithic, and in particular utricular, function. Our aim is to find the optimum combination of frequency and rise-time for BCV stimulation, to improve the sensitivity of oVEMP testing in the clinic.
  
  
  METHODS
  We tested 10 healthy subjects with 6 msec tone bursts of BCV at three stimulus frequencies, 250, 500, and 750 Hz, at rise-times ranging between 0 and 2 msec. The BCV was delivered at Fz.
  
  
  RESULTS
  The n10 response was significantly larger at the shorter rise-times, being largest at zero rise-time. In addition, we examined the effect of stimulus frequency in these same subjects by delivering 6 msec tone bursts at zero rise-time at a range of frequencies from 50 to 1200 Hz. The main effect of rise-time was significant with shorter rise-times leading to larger n10 responses and the Rise-Time × Frequency interaction was significant so that at low frequencies (100 Hz) shorter rise-times had a modest effect on n10 whereas at high frequencies (750 Hz) shorter rise-times increased n10 amplitude substantially. The main effect of frequency was also significant: The n10 response tended to be larger at lower frequency, being largest between 250 and 500 Hz.
  
  
  CONCLUSIONS
  In summary, in this sample of healthy subjects, the most effective stimulus for eliciting oVEMP n10 to BCV at Fz was found to be a tone burst with a rise-time of 0 msec at low stimulus frequency (250 or 500 Hz).
authors.affiliation: 1Vestibular Research Laboratory, School of Psychology, The University of Sydney, Sydney, New South Wales, Australia; 2MSA ENT Academy Center, Cassino, Frosinone, Italy; and 3Department of Neurology, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Burgess
authors.forename: Laura E
authors.initials: LE
authors.lastname: Mezey
authors.forename: Leonardo
authors.initials: L
authors.lastname: Manzari
authors.forename: Hamish G
authors.initials: HG
authors.lastname: MacDougall
authors.forename: Leigh A
authors.initials: LA
authors.lastname: McGarvie
authors.forename: Ian S
authors.initials: IS
authors.lastname: Curthoys
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001844:Bone Conduction / Q000502:physiology*; D004576:Electromyography / Q000379:methods*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010037:Otolithic Membrane / Q000502:physiology*; D012444:Saccule and Utricle / Q000502:physiology*