title: The cerebellar nodulus/uvula integrates otolith signals for the translational vestibulo-ocular reflex.
abstract: BACKGROUND
  The otolith-driven translational vestibulo-ocular reflex (tVOR) generates compensatory eye movements to linear head accelerations. Studies in humans indicate that the cerebellum plays a critical role in the neural control of the tVOR, but little is known about mechanisms of this control or the functions of specific cerebellar structures. Here, we chose to investigate the contribution of the nodulus and uvula, which have been shown by prior studies to be involved in the processing of otolith signals in other contexts.
  
  
  RESULTS
  We recorded eye movements in two rhesus monkeys during steps of linear motion along the interaural axis before and after surgical lesions of the cerebellar uvula and nodulus. The lesions strikingly reduced eye velocity during constant-velocity motion but had only a small effect on the response to initial head acceleration. We fit eye velocity to a linear combination of head acceleration and velocity and to a dynamic mathematical model of the tVOR that incorporated a specific integrator of head acceleration. Based on parameter optimization, the lesion decreased the gain of the pathway containing this new integrator by 62%. The component of eye velocity that depended directly on head acceleration changed little (gain decrease of 13%). In a final set of simulations, we compared our data to the predictions of previous models of the tVOR, none of which could account for our experimental findings.
  
  
  CONCLUSIONS
  Our results provide new and important information regarding the neural control of the tVOR. Specifically, they point to a key role for the cerebellar nodulus and uvula in the mathematical integration of afferent linear head acceleration signals. This function is likely to be critical not only for the tVOR but also for the otolith-mediated reflexes that control posture and balance.
authors.affiliation: Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America. mark.walker@case.edu
authors.forename: Mark F
authors.initials: MF
authors.lastname: Walker
authors.forename: Jing
authors.initials: J
authors.lastname: Tian
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Shan
authors.forename: Rafael J
authors.initials: RJ
authors.lastname: Tamargo
authors.forename: Howard
authors.initials: H
authors.lastname: Ying
authors.forename: David S
authors.initials: DS
authors.lastname: Zee
mesh_terms: D000818:Animals; D002531:Cerebellum / Q000502:physiology* / Q000503:physiopathology; D005133:Eye Movements / Q000502:physiology; D005260:Female; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology; D010037:Otolithic Membrane / Q000502:physiology* / Q000503:physiopathology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology