Electrical stimulation of rhesus monkey nucleus reticularis gigantocellularis. I. Characteristics of evoked head movements

Exp Brain Res. 2004 Jun;156(3):342-56. doi: 10.1007/s00221-003-1787-8. Epub 2004 Feb 21.

Abstract

The nucleus reticularis gigantocellularis (NRG) receives monosynaptic input from the superior colliculus (SC) and projects directly to neck motor neuron pools. Neurons in NRG are well situated to play a critical role in transforming SC signals into head movement commands. A previous study of movements evoked by NRG stimulation in the primate reported a variety of ipsilateral and contralateral head movements with horizontal, vertical and torsional components. In addition to head movements, it was reported that NRG stimulation could evoke movements of the pinnae, face, upper torso, and co-contraction of neck muscles. In this report, the role of the rhesus monkey NRG in head movement control was investigated using electrical stimulation of the rostral portion of the NRG. The goal was to characterize head movements evoked by NRG stimulation, describe the effects of altering stimulation parameters, and assess the relative movements of the eyes and head. Results indicate that electrical stimulation in the rostral portion of the NRG of the primate can consistently evoke ipsilateral head rotations in the horizontal plane. Head movement amplitude and peak velocity depend upon stimulation parameters (primarily frequency and duration of stimulation trains). During stimulation-induced head movements the eyes counter-rotate (presumably a result of the vestibulo-ocular reflex: VOR). At 46 stimulation sites from two subjects the average gain of this counter-rotation was -0.38 (+/-0.18). After the end of the stimulation train the head generally continued to move. During this epoch, after electrical stimulation ceased, VOR gain remained at this reduced level. In addition, VOR gain was similarly low when electrical stimulation was carried out during active fixation of a visual target. These data extend existing descriptions of head movements evoked by electrical stimulation of the NRG, and add to the understanding of the role of this structure in producing head movements.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / physiology
  • Axons / ultrastructure
  • Efferent Pathways / cytology
  • Efferent Pathways / physiology*
  • Electric Stimulation
  • Eye Movements / physiology
  • Female
  • Functional Laterality / physiology
  • Head Movements / physiology*
  • Macaca mulatta
  • Medulla Oblongata / cytology
  • Medulla Oblongata / physiology*
  • Motor Neurons / cytology
  • Motor Neurons / physiology
  • Neck Muscles / innervation*
  • Neck Muscles / physiology
  • Neural Conduction / physiology
  • Psychomotor Performance / physiology
  • Reaction Time / physiology
  • Reflex, Vestibulo-Ocular / physiology
  • Reticular Formation / cytology
  • Reticular Formation / physiology*
  • Spinal Cord / cytology
  • Spinal Cord / physiology