Ocular vestibular evoked myogenic potentials (OVEMPs) produced by impulsive transmastoid accelerations.
OBJECTIVE
Recent work has demonstrated the existence of ocular vestibular evoked myogenic potentials (OVEMPs), which likely reflect projections underlying the translational vestibular ocular reflex (TVOR). We examined extraocular muscle activity associated with impulsive acceleration of the head in the transmastoid plane.


METHODS
Accelerometry was measured in 4 subjects in response to acceleration impulses produced by a gamma function delivered with a Minishaker (4810, Bruel & Kjaer). This stimulus produced peak head accelerations of 0.13-0.14 g occurring at between 3.1 and 4.0 ms at the mastoids for both right and left head movement. OVEMPs were recorded in 10 normal subjects with 5 directions of gaze, using electrode pairs placed lateral to, above and below the eyes.


RESULTS
OVEMPs occurred at short latency, with initial peaks between 10.3 ms (p10) and 15.3 ms (n15). For a given recording site and gaze direction, the responses were determined solely by the direction of imposed acceleration.


CONCLUSIONS
We propose that, given the transtemporal nature of the stimuli, utricular afferents are likely to be powerfully activated. The OVEMPs evoked may be generated by the lateral recti and oblique muscles.


CONCLUSIONS
Sudden lateral accelerations of the head evoke the translational VOR and ocular counter rolling reflex and the pattern of muscle activations indicated by the OVEMPs appear to be a manifestation of these reflexes.
Todd
Neil P M
NP
Faculty of Life Science, University of Manchester, Moffat Building, Manchester, UK. neil.todd@manchester.ac.uk
Rosengren
Sally M
SM
Colebatch
James G
JG
D000054:Acceleration; D000328:Adult; D004569:Electroencephalography; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006257:Head; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008297:Male; D008416:Mastoid / Q000502:physiology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D010812:Physical Stimulation; D025341:Principal Component Analysis; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012444:Saccule and Utricle / Q000502:physiology; D014732:Vibration