Optokinetic-vestibular interaction in patients with increased gain of the vestibulo-ocular reflex |
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Authors: | Robert W Baloh Joseph L Demer |
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Institution: | (1) Department of Neurology, Reed Neurological Research Center, UCLA Medical Center, 90024 Los Angeles, CA, USA;(2) Department of Surgery, Division of Head and Neck Surgery, UCLA Medical Center, 90024 Los Angeles, CA, USA;(3) Department of Ophthalmology, Jules Stein Eye Institute, UCLA Medical Center, 90024 Los Angeles, CA, USA |
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Abstract: | We studied optokinetic nystagmus (OKN), optokinetic afternystagmus (OKAN) and visual-vestibular interaction in five patients with markedly elevated vestibulo-ocular reflex (VOR) gain due to cerebellar atrophy. All had impaired smooth pursuit, decreased initial slow phase velocity of OKN, and impaired ability to suppress the VOR with real or imagined targets. OKN slow phase velocity gradually built up over 25–45 s, reaching normal values for low stimulus velocities (30 deg/s). Initial velocity of OKAN was increased, but the rate of decay of OKAN was normal. These findings can be explained by models that include separate velocity storage and variable gain elements shared by the vestibular and optokinetic systems. |
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Keywords: | Cerebellum Optokinetic afternystagmus Velocity storage Human |
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