The human sound-evoked vestibulo-ocular reflex and its electromyographic correlate.
OBJECTIVE
Sound and vibration evoke a short-latency eye movement or "sound-evoked vestibulo-ocular reflex" (VOR) and an infraorbital surface potential: the "ocular vestibular-evoked myogenic potential" (OVEMP). We examined their relationship by measuring the modulation of both responses by gaze and stimulus parameters.


METHODS
In seven subjects with superior semicircular-canal dehiscence (SCD) and six controls, the sound-evoked VOR was measured in 3D using scleral search coils. OVEMPs were recorded simultaneously, using surface electromyography.


RESULTS
Eye movement onset (11.6+/-0.8ms) coincided with the OVEMP peak (12.1+/-0.35ms). OVEMP and VOR magnitudes were 5-15 times larger in SCD compared with controls. OVEMP amplitudes were maximal on upgaze and abolished on downgaze; VOR magnitudes were unaffected. When stimulus type was changed from sound to vibration, OVEMP and VOR changed concordantly: increasing in controls and decreasing in SCD. OVEMP and VOR tuned to identical stimulus frequencies. OVEMP and VOR magnitudes on upgaze were significantly correlated (R=0.83-0.97).


CONCLUSIONS
Selective decrease of the OVEMP upon downgaze is consistent with relaxation or retraction of the inferior oblique muscles. The temporal relationship of OVEMP and VOR and their identical modulation by external factors confirms a common origin.


CONCLUSIONS
Sound-evoked OVEMP and VOR represent the electrical and mechanical correlates of the same vestibulo-ocular response.
Welgampola
Miriam S
MS
Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Missenden Road, Camperdown, Sydney, NSW 2050, Australia. miriam@icn.usyd.edu.au
Migliaccio
Americo A
AA
Myrie
Oluwaseun A
OA
Minor
Lloyd B
LB
Carey
John P
JP
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000368:Aged; D004576:Electromyography; D004585:Electrooculography; D005071:Evoked Potentials / Q000502:physiology; D005403:Fixation, Ocular / Q000502:physiology; D007839:Functional Laterality; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D011571:Psychoacoustics; D011930:Reaction Time / Q000502:physiology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D013016:Sound; D013223:Statistics as Topic; D015837:Vestibular Diseases / Q000175:diagnosis / Q000503:physiopathology