Cheung BS, Money KE, Howard IP.
Aviat Space Environ Med. 1993 May; 64: 424.
Defence and Civil Institute of Environmental Medicine, Ontario, Canada.
INTRODUCTION. When a person views a moving display, the eyes automatically execute a series of pursuit movements alternating with saccadic return movements. When this response, optokinetic nystagmus (OKN), occurs around the roll axis (x axis) it is known as torsional optokinetic nystagmus (TOKN). Under 1 G, the gain of TOKN is shown to be relatively small. In flight, during short sharp rolling movements, important consequences could arise from poor optokinetic response. It has been shown that Gz forces initiate an otolith-ocular response that manifests itself partly in modulation of the gain of vertical optokinetic nystagmus. The purpose of the present study was to investigate the influence of varying gravitoinertial (Gz) forces on torsional optokinetic nystagmus during parabolic flights. METHODS. Using the scleral search-coil technique, we measured the gain and phase lag of torsional OKN induced by a hemispherical visual display rotating about the roll axis either at constant velocity or sinusoidally at various frequencies during level flight, hypogravity, and hypergravity. RESULTS. Compared to level flight, there was a significant increase of slow phase 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. CONCLUSION. These data suggested that otolith inputs do affect TOKN. 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.
Publication Types:
Keywords:
- Acceleration
- Gravitation
- Humans
- Hypogravity
- Nystagmus, Optokinetic
- Nystagmus, Pathologic
- Otolithic Membrane
- Photic Stimulation
- NASA Discipline Neuroscience
- NASA Discipline Number 00-00
- NASA Program Flight
- Non-NASA Center
Other ID:
UI: 102212603
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