Eye instability induced by vestibular stimulation in rabbits.
The slow compensatory phases of the vestibulo-ocular reflex (VOR) in the rabbit tend to drift and the drift reverses the direction. This periodic alternating drift (PAD) has two peculiar characteristics: (1) it is induced by sinusoidal vestibular stimulation in naive animals, being evoked immediately after stimulus onset and persisting after the end of stimulation; (2) the peak velocity and period of the drift are dependent on stimulus amplitude. PAD of the rabbit has strong similarities with PAN, a periodic alternating nystagmus observed in humans with cerbellar disorders and in monkeys after nodulo-uvulectomy, although its peak velocity is smaller. It is hypothesized that PAD is due to a slight instability, caused by vestibular stimulation in darkness, of the cerebellar adaptive loop, which exerts a variable gain control on the time constant of the velocity storage integrator.
Ferraresi
A
A
Institute of Human Physiology, Faculty of Medicine, Catholic University, Largo Francesco Vito, 1-00168 Roma, Italy.
Azzena
G B
GB
Troiani
D
D
D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002531:Cerebellum / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009759:Nystagmus, Pathologic / Q000503:physiopathology; D010812:Physical Stimulation; D011817:Rabbits; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D014726:Vestibular Nuclei / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*