Otolith orientation and downbeat nystagmus in the normal cat

✍ Scribed by S. A. Rude; J. F. Baker

• Publisher: Springer-Verlag
• Year: 1996
• Tongue: English
• Weight: 488 KB
• Volume: 111
• Category: Article
• ISSN: 0014-4819
• DOI: 10.1007/bf00229564

✦ Synopsis

Upward drift of the eyes in darkness, influenced by whole body orientation, was studied in 12 cats using electromagnetic search coil and electro-oculographic techniques. Animals were positioned stationary with respect to gravity with 0 degree tilt ("upright") or rolled 90 degrees ("on side"), pitched 90 degrees ("on nose" or "on tail"), or inverted 180 degrees ("upside down"). A downbeat quick-phase nystagmus (slow-phase upward in the cat's orbit) was measured, varying in magnitude with angle of tilt (0.21 degree/s at 0 degree tilt; 4.14 degrees/s at 180 degrees tilt). The drift was not present in the light. Upward eye velocities over a range of body orientations in darkness suggest a systematic drive to the eyes which increases with tilt away from upright. The relationship of this behavior to previous models of angular velocity estimation by an otolith-driven central mechanism is discussed.