Comparing Extraocular Motoneuron Discharges During Head-Restrained Saccades and Head-Unrestrained Gaze Shifts. Kathleen E. Cullen1, Henrietta L. Galiana2 and Pierre A. Sylvestre1. Aerospace Medical Research Unit, Departments of Physiology1 and Biomedical Engineering2, McGill University, Montreal, Quebec, Canada.
APStracts 6:0481N, 1999.
Burst neurons (BNs) in the paramedian pontine reticular formation provide the primary input to the extraocular motoneurons (MNs) during head-restrained saccades and combined eye-head gaze shifts. Prior studies have shown that BNs carry eye movement-related signals during saccades, and carry head as well as eye movement-related signals during gaze shifts. Therefore, MNs receive signals related to head motion during gaze shifts, yet they solely drive eye motion. Here we addressed whether the relationship between MN firing rates and eye movements is influenced by the additional premotor signals present during gaze shifts. Neurons in the abducens nucleus of monkeys were first studied during saccades made with the head stationary. We then recorded from the same neurons during voluntary combined eye-head gaze shifts. We conclude that the activity of MNs, in contrast to that of BNs, is related to eye motion by the same dynamic relationship during head-restrained saccades and head-unrestrained gaze shifts. In addition, we show that a standard metric-based analysis (i.e. counting the number of spikes (NOS) in a burst) yields misleading results when applied to the same data set. We argue that this latter approach fails because it does not properly consider the system's dynamics or the strong interactions between eye and head motion.
Received 24 June 1999; accepted in final form 8 September 1999.
APS Manuscript Number J516-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999