Effect of Ibotenic Acid Lesions of the Omnipause Neurons on Saccadic Eye
Movements in Rhesus Macaques.
Kaneko, Chris R. S.
Department of Physiology & Biophysics and Regional Primate Research Center,
University of Washington, Seattle, Washington 98195.
APStracts 2:0367N, 1995.
SUMMARY AND CONCLUSIONS
1 . Although much is known about the neurons that control saccadic eye
movements, the precise manner in which they interact is still uncertain. To
test the validity of competing models of the pontine saccade generator,
neurotoxic lesions were made in the nucleus raphe interpositus (rip), which
contains one of the principal types of saccade-related neurons, the omnipause
neurons (OPNs). The correlated changes in eye movement were quantified in
three juvenile rhesus macaques and compared with the results predicted by
different models. 2. After the location of the OPNs was mapped, the rip was
subjected to sequential, punctate pressure injections of ibotenic acid. The
resulting progressive damage was correlated with changes in saccade metrics,
including a decrease in peak saccadic velocity and an increase in saccade
duration. 3 . The damage to rip and presumably to the OPNs was not associated
with a change in the animals' ability to maintain steady fixation of a
stationary target. 4 . The results suggest that Robinson's original local
feedback model of saccade generation should be modified. Either a second
integrator should be added or the concept of local feedback should be
abandoned entirely. 5 . The suggestion that the OPNs are primarily responsible
for fixation is probably incorrect. OPNs may contribute to fixation stability
along with a number of other sources.
Received 4 May 1995; accepted in final form 30 November 1995.
APS Manuscript Number J303-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95