Coordination of eye and head components of movements evoked by stimulation of the paramedian pontine reticular formation

Exp Brain Res. 2008 Jul;189(1):35-47. doi: 10.1007/s00221-008-1401-1. Epub 2008 May 6.

Abstract

Constant frequency microstimulation of the paramedian pontine reticular formation (PPRF) in head-restrained monkeys evokes a constant velocity eye movement. Since the PPRF receives significant projections from structures that control coordinated eye-head movements, we asked whether stimulation of the pontine reticular formation in the head-unrestrained animal generates a combined eye-head movement or only an eye movement. Microstimulation of most sites yielded a constant-velocity gaze shift executed as a coordinated eye-head movement, although eye-only movements were evoked from some sites. The eye and head contributions to the stimulation-evoked movements varied across stimulation sites and were drastically different from the lawful relationship observed for visually-guided gaze shifts. These results indicate that the microstimulation activated elements that issued movement commands to the extraocular and, for most sites, neck motoneurons. In addition, the stimulation-evoked changes in gaze were similar in the head-restrained and head-unrestrained conditions despite the assortment of eye and head contributions, suggesting that the vestibulo-ocular reflex (VOR) gain must be near unity during the coordinated eye-head movements evoked by stimulation of the PPRF. These findings contrast the attenuation of VOR gain associated with visually-guided gaze shifts and suggest that the vestibulo-ocular pathway processes volitional and PPRF stimulation-evoked gaze shifts differently.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Attention / physiology
  • Dose-Response Relationship, Radiation
  • Electric Stimulation / methods
  • Eye Movements / physiology*
  • Functional Laterality
  • Head Movements / physiology*
  • Macaca mulatta
  • Motor Neurons / radiation effects
  • Psychomotor Performance / physiology*
  • Reticular Formation / physiology*
  • Reticular Formation / radiation effects