Neck Muscle Responses to Stimulation of Monkey Superior Colliculus. I. Topography and Manipulation of Stimulation Parameters

• Published in: Journal of neurophysiology 2002-10, Vol.88 (4), p.1980-1999
• Main Authors: Corneil, Brian D, Olivier, Etienne, Munoz, Douglas P
• Format: Article
• Language: English
• Subjects: Animals; Brain Mapping; Electric Stimulation; Electromyography; Evoked Potentials - physiology; Fixation, Ocular - physiology; Head Movements - physiology; Macaca mulatta; Male; Motor Neurons - physiology; Neck Muscles - innervation; Neck Muscles - physiology; Psychomotor Performance - physiology; Restraint, Physical; Space life sciences; Superior Colliculi - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2002.88.4.1980

  1 Canadian Institutes of Health Research Group in Sensory-Motor Systems, Centre for Neuroscience Studies, Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada; and   2 Laboratory of Neurophysiology, School of Medicine, University of Louvain, 1200 Brussels, Belgium Corneil, Brian D., Etienne Olivier, and Douglas P. Munoz. Neck Muscle Responses to Stimulation of Monkey Superior Colliculus. I. Topography and Manipulation of Stimulation Parameters. J. Neurophysiol. 88: 1980-1999, 2002. The role of the primate superior colliculus (SC) in orienting head movements was studied by recording electromyographic (EMG) activity from multiple neck muscles following electrical stimulation of the SC. Combining SC stimulation with neck EMG recordings provides an objective and sensitive measure of the SC drive onto neck muscle motoneurons, particularly in relation to evoked gaze shifts. In this paper, we address how neck EMG responses to SC stimulation in head-restrained monkeys depend on the rostrocaudal, mediolateral, and dorsoventral location of the stimulating electrode within the SC and vary with manipulations of the eye position prior to stimulation onset and changes in stimulation current and duration. Stimulation predominantly evoked EMG responses on the muscles obliquus capitis inferior, rectus capitis posterior major, and splenius capitis. These responses became larger in magnitude and shorter in onset latency for progressively more caudal stimulation locations, consistent with turning the head. However, evoked responses persisted even for more rostral stimulation locations usually not associated with head movements. Manipulating initial eye position revealed that the magnitude of evoked responses became stronger as the eyes attained positions contralateral to the side of stimulation, consistent with a summation between a generic command evoked by SC stimulation and the influence of eye position on tonic neck EMG. Manipulating stimulation current and duration revealed that the relationship between gaze shifts and evoked EMG responses is not obligatory: short-duration (150 ms) occasionally revealed a transient neck EMG response aligned on the onset of sequential gaze shifts. We conclude that the SC drive to neck muscle motoneurons is far more widespread than traditionally supposed and is relayed through interve