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Translational Vestibulo-Ocular Reflexes During Off-Vertical Axis RotationThe translational vestibulo-ocular reflex (tVOR) is an otolith-mediated response that stabilizes near vision during linear acceleration at higher frequencies where visually mediated reflexes are not adequate. The modulation of horizontal and vergence eye movements during Off-Vertical Axis Rotation (OVAR) are presumed to reflect the tVOR in response to the continuously varying linear acceleration in the interaural and nasooccipital axes, respectively. The purpose of this study was to examine the effect of frequency and fixation distance on the modulation of slow phase eye velocity (SPV) as further evidence that the tVOR is elicited during OVAR. Eighteen subjects were rotated about their longitudinal axis tilted by 30 deg off-vertical. Rotational velocities varied between 18 and 288 deg/sec corresponding to a frequency range of 0.05 to 0.8 Hz. Fixation distance was altered by asking subjects to imagine stationary targets that were briefly presented at 0.5, 1 and 2 m during some rotation cycles. The target flash was 40 msec in the nose-up position at eye level. Oculomotor responses were recorded in the dark using infrared binocular videography. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple rotation cycles. Consistent with previous studies, the modulation of both horizontal and vergence SPV increased with stimulus frequency. The effect of fixation distance was negligible at lower frequencies. The modulation of horizontal and vergence SPV was; however, proportional to fixation distance during OVAR at 0.8 Hz. This increasing sensitivity and dependence on fixation distance of horizontal and vergence SPV during OVAR is consistent with tVOR characteristics measured during other types of linear motion. We conclude that the modulation of horizontal and vergence SPV will be diagnostically more useful at higher stimulus frequencies where the tVOR is more robust.
Document ID
20090035723
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Wood, Scott J.
(Universities Space Research Association Houston, TX, United States)
Clement, Gilles
(International Space Univ., Inc. United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2009
Subject Category
Aerospace Medicine
Report/Patent Number
JSC-CN-19013
Meeting Information
Meeting: 33rd Association for Research in Otolaryngology Mid-Winter Meeting
Location: Anaheim, CA
Country: United States
Start Date: February 6, 2010
End Date: February 10, 2010
Distribution Limits
Public
Copyright
Other

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