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Alexander's law and the oculomotor neural integrator: three-dimensional eye velocity in patients with an acute vestibular asymmetry


Bockisch, C J; Hegemann, S (2008). Alexander's law and the oculomotor neural integrator: three-dimensional eye velocity in patients with an acute vestibular asymmetry. Journal of Neurophysiology, 100(6):3105-3116.

Abstract

According to Alexander's law (AL), the slow phase velocity of nystagmus of vestibular origin is dependent on horizontal position, with lower velocity when gaze is directed in the slow compared to the fast phase direction. Adaptive changes in the velocity-to-position neural integrator are thought to cause AL. While these changes have been described for the horizontal neural integrator, nystagmus often includes vertical and torsional components, but the adaptive abilities of the vertical and torsional integrators have not been investigated. We measured 11 patients with a peripheral vestibular asymmetry, and used second order equations to describe how velocity varied with position. Horizontal velocity changed with horizontal position in accordance with AL, and the second order term for horizontal position was also significant. While velocity decreased in the slow phase direction, it was relatively unchanged more than 10 degrees into the fast phase direction. Vertical velocity was also highest in the vertical fast phase direction, and the second order term for vertical position was also significant, as vertical velocity increased in the vertical fast phase direction, but was unchanging in the slow phase direction. Torsional velocity varied linearly with horizontal, but not vertical, position. These results show that the horizontal and vertical oculomotor neural integrators react to altered vestibular input by maintaining different integrating time constants depending upon gaze direction.

According to Alexander's law (AL), the slow phase velocity of nystagmus of vestibular origin is dependent on horizontal position, with lower velocity when gaze is directed in the slow compared to the fast phase direction. Adaptive changes in the velocity-to-position neural integrator are thought to cause AL. While these changes have been described for the horizontal neural integrator, nystagmus often includes vertical and torsional components, but the adaptive abilities of the vertical and torsional integrators have not been investigated. We measured 11 patients with a peripheral vestibular asymmetry, and used second order equations to describe how velocity varied with position. Horizontal velocity changed with horizontal position in accordance with AL, and the second order term for horizontal position was also significant. While velocity decreased in the slow phase direction, it was relatively unchanged more than 10 degrees into the fast phase direction. Vertical velocity was also highest in the vertical fast phase direction, and the second order term for vertical position was also significant, as vertical velocity increased in the vertical fast phase direction, but was unchanging in the slow phase direction. Torsional velocity varied linearly with horizontal, but not vertical, position. These results show that the horizontal and vertical oculomotor neural integrators react to altered vestibular input by maintaining different integrating time constants depending upon gaze direction.

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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 Otorhinolaryngology
04 Faculty of Medicine > Center for Integrative Human Physiology
04 Faculty of Medicine > University Hospital Zurich > Clinic for Neurology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:17 September 2008
Deposited On:27 Nov 2008 08:25
Last Modified:05 Apr 2016 12:36
Publisher:American Physiological Society
ISSN:0022-3077
Publisher DOI:10.1152/jn.90381.2008
PubMed ID:18799600
Permanent URL: http://doi.org/10.5167/uzh-6245

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