title: Stimulation of pontine reticular formation in monkeys with strabismus.
abstract: OBJECTIVE
  Saccade disconjugacy in strabismus could result from any of a number of factors, including abnormalities of eye muscles, the plant, motoneurons, near response cells, or atypical tuning of neurons in saccade-related areas of the brain. This study was designed to investigate the possibility that saccade disconjugacy in strabismus is associated with abnormalities in paramedian pontine reticular formation (PPRF).
  
  
  METHODS
  We applied microstimulation to 22 sites in PPRF and 20 sites in abducens nucleus in three rhesus macaque monkeys (one normal, one esotrope, and one exotrope).
  
  
  RESULTS
  When mean velocity was compared between the two eyes, a slight difference was found for 1/5 sites in the normal animal. Significant differences were found for 5/6 sites in an esotrope and 10/11 sites in an exotrope. For five sites in the strabismic monkeys, the directions of evoked movements differed by more than 40° between the two eyes. When stimulation was applied to abducens nucleus (20 sites), the ipsilateral eye moved faster for 4/6 sites in the normal animal and all nine sites in the esotrope. For the exotrope, however, the left eye always moved faster, even for three sites on the right side. For the strabismic animals, stimulation of abducens nucleus often caused a different eye to move faster than stimulation of PPRF.
  
  
  CONCLUSIONS
  These data suggest that PPRF is organized at least partly monocularly in strabismus and that disconjugate saccades are at least partly a consequence of unbalanced saccadic commands being sent to the two eyes.
authors.affiliation: Washington National Primate Research Center, University of Washington, Seattle, Washington.
authors.forename: Mark M G
authors.initials: MM
authors.lastname: Walton
authors.forename: Seiji
authors.initials: S
authors.lastname: Ono
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mustari
mesh_terms: D000010:Abducens Nerve / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004948:Esotropia / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005099:Exotropia / Q000503:physiopathology*; D005260:Female; D008253:Macaca mulatta; D012154:Reticular Formation / Q000502:physiology*; D012438:Saccades / Q000502:physiology*
keywords: PPRF; esotropia; exotropia; saccadic eye movements; strabismus