HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 98/6/3581    most recent 00992.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ling, L. Articles by Dean, P. Search for Related Content PubMed PubMed Citation Articles by Ling, L. Articles by Dean, P.

Effects of Initial Eye Position on Saccade-Related Behavior of Abducens Nucleus Neurons in the Primate

¹Department of Physiology and Biophysics and ²Washington National Primate Research Center, University of Washington, Seattle, Washington; and ³Department of Psychology, University of Sheffield, Sheffield, United Kingdom

Submitted 4 September 2007; accepted in final form 2 October 2007

Previous work suggests that when the eye starts at different orbital initial positions (IPs), the saccade control system is faced with significant nonlinearities. Here we studied the effects of IP on saccade-related firing of monkey abducens neurons by either isolating saccade variables behaviorally or applying a multiple linear regression analysis. Over a 50° range of IPs, we could select 10° horizontal saccades with identical velocity profiles, which would require identical control signals in a linear system. The bursts accompanying ipsiversive saccades for IPs above the threshold for steady firing were quite similar. The excess burst rate above steady firing was either constant or decreased with ipsiversive IP, and both the number of excess spikes in the burst and burst duration were nearly constant. However, for ipsiversive saccades from IPs below threshold, both peak burst rate (6.82 ± 1.38 spikes·s^–1·deg^–1) and burst duration (0.67 ± 0.28 ms/deg) increased substantially with ipsiversive IPs. Moreover, the pause associated with contraversive saccades shortened considerably with ipsiversive IPs (mean 1.2 ms/deg). This pattern of results for pauses and for bursts below threshold suggests the presence of a significant nonlinearity. Abducting saccades are produced by the net force of agonist lateral rectus (LR) and antagonist medial rectus (MR) muscles. We suggest that the decreasing force in the MR muscle with IPs in the abducting direction requires a more vigorous burst in LR motoneurons, which appears to be generated by a combination of saturating and nonsaturating burst commands and the recruitment of additional abducens neurons.

This article has been cited by other articles:

				S. R. Anderson, J. Porrill, S. Sklavos, N. J. Gandhi, D. L. Sparks, and P. Dean Dynamics of Primate Oculomotor Plant Revealed by Effects of Abducens Microstimulation J Neurophysiol, June 1, 2009; 101(6): 2907 - 2923. [Abstract] [Full Text] [PDF]