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Why do oVEMPs become larger when you look up? Explaining the effect of gaze elevation on the ocular vestibular evoked myogenic potential


Rosengren, S M; Colebatch, Js G; Straumann, D; Weber, K P (2013). Why do oVEMPs become larger when you look up? Explaining the effect of gaze elevation on the ocular vestibular evoked myogenic potential. Clinical Neurophysiology, 124(4):785-791.

Abstract

OBJECTIVES: The ocular vestibular evoked myogenic potential (oVEMP) is a vestibular reflex recorded from the inferior oblique (IO) muscles, which increases in amplitude during eye elevation. We investigated whether this effect of gaze elevation could be explained by movement of the IO closer to the recording electrode. METHODS: We compared oVEMPs recorded with different gaze elevations to those recorded with constant gaze position but electrodes placed at increasing distance from the eyes. oVEMPs were recorded in ten healthy subjects using bursts of skull vibration. RESULTS: oVEMP amplitude decreased more with decreasing gaze elevation (9μV from 24° up to neutral) than with increasing electrode distance (2.7μV from baseline to 6.4mm; P<0.005). The oVEMP recorded with gaze 24° down had delayed latency (by 4.5ms). CONCLUSION: The effect of gaze elevation on the oVEMP cannot be explained by changes in position of the muscle alone and is likely mainly due to increased tonic contraction of the IO muscle in up-gaze. The oVEMP recorded in down-gaze (when the IO is inactivated, but the IR activated) likely originates in the adjacent IR muscle. SIGNIFICANCE: Our results suggest that oVEMP amplitudes in extraocular muscles scale in response to changing tonic muscle activity.

Abstract

OBJECTIVES: The ocular vestibular evoked myogenic potential (oVEMP) is a vestibular reflex recorded from the inferior oblique (IO) muscles, which increases in amplitude during eye elevation. We investigated whether this effect of gaze elevation could be explained by movement of the IO closer to the recording electrode. METHODS: We compared oVEMPs recorded with different gaze elevations to those recorded with constant gaze position but electrodes placed at increasing distance from the eyes. oVEMPs were recorded in ten healthy subjects using bursts of skull vibration. RESULTS: oVEMP amplitude decreased more with decreasing gaze elevation (9μV from 24° up to neutral) than with increasing electrode distance (2.7μV from baseline to 6.4mm; P<0.005). The oVEMP recorded with gaze 24° down had delayed latency (by 4.5ms). CONCLUSION: The effect of gaze elevation on the oVEMP cannot be explained by changes in position of the muscle alone and is likely mainly due to increased tonic contraction of the IO muscle in up-gaze. The oVEMP recorded in down-gaze (when the IO is inactivated, but the IR activated) likely originates in the adjacent IR muscle. SIGNIFICANCE: Our results suggest that oVEMP amplitudes in extraocular muscles scale in response to changing tonic muscle activity.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Ophthalmology Clinic
04 Faculty of Medicine > University Hospital Zurich > Clinic for Neurology
04 Faculty of Medicine > Neuroscience Center Zurich
04 Faculty of Medicine > Center for Integrative Human Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2013
Deposited On:24 Jan 2013 13:59
Last Modified:05 Apr 2016 16:15
Publisher:Elsevier
ISSN:1388-2457
Publisher DOI:https://doi.org/10.1016/j.clinph.2012.10.012
PubMed ID:23177454

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