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J Vestib Res. 2000;10(3):143-50.

Characteristics of secondary phase post-rotatory nystagmus following off-vertical axis rotation in humans.

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Department of Otolaryngology, University of Pittsburgh, PA 15213, USA.


The nystagmus following yaw earth-vertical axis rotation often reverses direction, a phenomenon known as the "secondary phase". The purpose of this study was to examine the existence and the spatial and temporal properties of the secondary phase of post-rotatory nystagmus following off-vertical axis rotation (OVAR). Eleven normal human subjects were rotated at 120 or 180 degrees/s about an off-vertical axis and stopped in the left ear down or right ear down lateral position. Horizontal and vertical eye positions were recorded with a scleral search coil, and horizontal and vertical slow component eye velocities were computed. Our results indicate that (a) there is a robust secondary phase nystagmus following OVAR, and (b) the direction of the secondary phase nystagmus tends to align with earth-horizontal. These results can be explained by a minor modification of an existing VOR model that has been shown to produce secondary phase responses.

[Indexed for MEDLINE]

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