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

JM Furman, I Koizuka, RH Schor - Journal of Vestibular …, 2000 - content.iospress.com
JM Furman, I Koizuka, RH Schor
Journal of Vestibular Research, 2000content.iospress.com
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∘/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 …
Abstract
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∘/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.
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