title: Electrode montage and gaze effects on ocular vestibular evoked myogenic potentials (oVEMPs).
abstract: To investigate the properties of lateral electrode locations compared to the conventional ones and to bipolar compared to chin-referenced montages for recording ocular vestibular evoked myogenic potentials (oVEMPs).
  
  
  
  A total of 18 subjects were studied using 5 electrode locations around the eye, including the conventional location and more lateral ones (i.e. M, ML and L electrodes near the orbital margin, R1 and R2 electrodes below the two more medial ones). Unilateral air-conducted (AC) sound, bone-conducted (BC) impulses at the mastoid and BC vibration (500Hz) at the forehead were used. These were applied while the subjects looked in neutral gaze and with 4 levels of increasing elevation. A subset of 10 subjects were also studied when looking downwards at 4 levels. Five bipolar montages were created offline by subtraction.
  
  
  
  The M and ML electrodes had the largest responses but responses were seen for all 5 electrodes. The chin reference was associated with substantial pickup from the contralateral side (as judged using unilateral AC stimulation). The M-R1 (conventional) montage showed a significantly non-linear response to gaze angle, unlike the ML montages. The ML-R1 montage gave the largest responses. There was a clear change in latency for the conventional montage with downgaze for the AC and BC impulsive stimuli.
  
  
  
  The ML active electrode has a more stable n1 latency, a larger and a more linear response to gaze angle than the conventional recording site, probably due to contamination by pickup of inferior rectus activity when using the conventional site.
  
  
  
  The ML location is a better site for the active pickup for recording oVEMPs if the main object of study is the inferior oblique muscle and particularly if subjects have difficulty with upgaze.
authors.affiliation: Prince of Wales Clinical School and Neuroscience Research Australia, University of New South Wales, Randwick, Sydney, NSW 2031, Australia.
authors.forename: Sendhil
authors.initials: S
authors.lastname: Govender
authors.affiliation: Prince of Wales Clinical School, University of New South Wales, Randwick, Sydney, NSW 2031, Australia.
authors.forename: Petrina Y
authors.initials: PY
authors.lastname: Cheng
authors.affiliation: Prince of Wales Clinical School and Neuroscience Research Australia, University of New South Wales, Randwick, Sydney, NSW 2031, Australia.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Dennis
authors.affiliation: Prince of Wales Clinical School and Neuroscience Research Australia, University of New South Wales, Randwick, Sydney, NSW 2031, Australia. Electronic address: j.colebatch@unsw.edu.au.
authors.forename: James G
authors.initials: JG
authors.lastname: Colebatch
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D004566:Electrodes; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology; D055815:Young Adult
keywords: Electrode; Gaze; Montage; oVEMP