Modified saccades evoked by stimulation of the macaque superior colliculus account for properties of the resettable integrator. Kustov, Alexander A., a nd David Lee Robinson. Section on Visual Behavior, Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892.
APStracts 2:0054N, 1995.
SUMMARY AND CONCLUSIONS
1. Models of the saccadic system propose that there is an integration of the pulse signal, although the process of resetting has been unclear. Other studies of the superior collicular contribution to the saccadic system have proposed a sensory, not motor, nature for its signal. 2. To test experimentally the resetting of the integrator and the nature of the collicular signal, we electrically stimulated the superior colliculus during periods of fixation and during the course of visually guided saccades. Trains of stimuli which were presented during periods of fixation evoked saccades with fixed vectors. Identical stimulation at the beginning of a visually guided saccade evoked saccades whose direction was rotated and amplitude extended from the fixed vector. The direction of the rotation was opposite to that of the visually guided saccade, and the magnitude of this rotation could be as large as 80o. 3. Stimulation which was applied at progressively later times during the visually guided saccade, evoked saccades with progressively smaller rotations and progressively less elongations. The time period during which saccades were modified persisted beyond the end of the visually guided saccade, when the eyes were stationary. Thus, the end of the saccade is not a period of quiescence within the oculomotor pathways. 4. Our results suggest that the resetting of the integration of -2- the saccade signal is gradual rather than abrupt. Furthermore, these data suggest that the superior colliculus signals a motor error. 

Received 19 December 1994; accepted in final form 19 January 1995.
APS Manuscript Number J790-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  3 April 1995.