title: Oscillatory eye movements resembling pendular nystagmus in normal juvenile macaques.
abstract: OBJECTIVE
  Juvenile monkeys being trained on smooth-pursuit tasks exhibit ocular oscillations resembling pendular nystagmus. The purpose of this study was to analyze these oscillations, the effects of gabapentin on them, and responses of cerebellar floccular neurons to understand possible neuronal mechanisms.
  
  
  METHODS
  Four monkeys were trained for horizontal and vertical smooth pursuit; in two, saccades were also tested. Frequency, peak-to-peak eye velocity, and amplitude of the ocular oscillations were measured. In one monkey, the effect of gabapentin on the oscillations was measured, and oscillation-related neuronal discharge was recorded in the cerebellar floccular region.
  
  
  RESULTS
  Ocular oscillations, with features of pendular nystagmus, appeared early during training of both horizontal and vertical pursuit in all four monkeys. Although these oscillations were observed both in the direction of pursuit and orthogonally, the velocity and amplitude of oscillation were larger in the direction of pursuit, implicating pursuit mechanisms in their generation. Corrective saccades were often superimposed on the oscillations during pursuit and fixation. Gabapentin suppressed oscillations in the monkey tested. Recordings in the floccular region revealed a subset of neurons discharged during both the oscillations and corrective saccades. Many of them exhibited burst-tonic discharge during visually guided saccades, similar to discharge of brain stem burst-tonic neurons, suggesting contributions of the neural integrator to the oscillations.
  
  
  CONCLUSIONS
  The developmentally transient ocular oscillations occurring in monkeys during pursuit training has properties resembling pendular nystagmus. Both smooth pursuit and a neural integrator may contribute to these ocular oscillations. Analysis using an efference-copy pursuit model supports the interpretation herein.
authors.affiliation: Department of Physiology, School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Shichinohe
authors.forename: Graham
authors.initials: G
authors.lastname: Barnes
authors.forename: Teppei
authors.initials: T
authors.lastname: Akao
authors.forename: Sergei
authors.initials: S
authors.lastname: Kurkin
authors.forename: Junko
authors.initials: J
authors.lastname: Fukushima
authors.forename: Manabu
authors.initials: M
authors.lastname: Kase
authors.forename: R John
authors.initials: RJ
authors.lastname: Leigh
authors.forename: Tim
authors.initials: T
authors.lastname: Belton
authors.forename: Kikuro
authors.initials: K
authors.lastname: Fukushima
mesh_terms: D000588:Amines / Q000494:pharmacology; D000818:Animals; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D000077206:Gabapentin; D008251:Macaca; D009759:Nystagmus, Pathologic / Q000503:physiopathology*; D011698:Pursuit, Smooth / Q000187:drug effects / Q000502:physiology*; D012438:Saccades / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D000588:Amines; D003509:Cyclohexanecarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin