Difference Between Visually And Electrically Evoked Gaze Saccades Disclosed By Altering The Head Moment Of Inertia. Alexandre J. F. Coimbra1,2, Philippe Lefèvre1,2, Marcus Missal1 and Etienne Olivier1. 1Laboratory of Neurophysiology, Université Catholique de Louvain, Brussels, Belgium and 2CESAME, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
APStracts 6:0538N, 1999.
Differences between gaze shifts evoked by collicular electrical stimulation and those triggered by the presentation of a visual stimulus were studied in head-free cats by increasing the head moment of inertia. This maneuver modified the dynamics of these two types of gaze shifts by slowing down head movements. Such an increase in the head moment of inertia did not affect the metrics of visually evoked gaze saccades because their duration was precisely adjusted to compensate for these changes in movement dynamics. In contrast, the duration of electrically evoked gaze shifts remained constant irrespective of the head moment of inertia and therefore their amplitude was significantly reduced. These results suggest that visually and electrically evoked gaze saccades are controlled by different mechanisms. Whereas the accuracy of visually evoked saccades is likely to be assured by on-line feedback information, the absence of duration adjustment in electrically evoked gaze shifts suggests that feedback information necessary to maintain their metrics is not accessible or is corrupted during collicular stimulation. This is of great importance when these two types of movements are compared to infer the role of the superior colliculus in the control of orienting gaze shifts.
Received 19 July 1999; accepted in final form 20 October 1999.
APS Manuscript Number J600-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999