DYNAMICS OF TORSIONAL OPTOKINETIC NYSTAGMUS UNDER ALTERED GRAVITOINERTIAL FORCES

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Authors
  1. Cheung, B.S.K.
  2. Money, K.E.
  3. Howard, I.P.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
The purpose of the present study was to investigate the influence of varying gravitoinertial forces on torsional optokinetic nystagmus during parabolic flights. Using the scleral search-coil technique, we measured the gain and phase lag of torsional optokinetic nystagmus (OKN) induced by a hemispherical visual display rotating about the roll axis either at constant velocity or sinusoidally at varous frequencies during level flight, hypogravity, and hypergravity. Compared with level flight, there was a significant increase in slow-phase eye velocity during hypogravity and an increase in nystagmic frequency. An absence of well-developed torsional optokinetic afternystagmus was observed in all three gravity conditions. Other characteristics included a lack of a slow rise component. These data suggest that otolith inputs do affect torsional OKN. The absence of well-developed torsional optokinetic afternystagmus suggests that the velocity storage pathways do not contribute significantly to the torsional OKN system in humans.
Keywords
Torsional optokinetic nystagmus (OKN);Parabolic flights;Hypogravity;Hyergravity
Report Number
DCIEM-93-27 — Reprint
Date of publication
08 Aug 1994
Number of Pages
8
Reprinted from
Exp Brain Res, vol 102, 1995, p 511-518
DSTKIM No
95-03845
CANDIS No
152604
Format(s):
Document Image stored on Optical Disk;Hardcopy

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