Abstract
Focal electrical stimulation through the recording microelectrode was performed in the superior colliculus of spinally anesthetized and of unanesthetized cats. Eye movements were recorded by conventional EOG methods and by a light beam reflected from a corneal mirror. Spontaneous and evoked saccades have a similar amplitude-duration relation, peak velocities of about 300°/sec and maximal amplitudes of 30°. Amplitude, speed and latency of evoked eye movements depend strongly upon strength of stimulating current. With increasing penetration depth, the threshold intensity of the electrical stimulus decreases abruptly when the electrode approaches the intermediate tectal layer, to decrease only slightly with further downward penetration. Some of the characteristics of oculomotor output of a tectal subarea parallel those of the visual response characteristics of single neurons of the same region. Receptive field position and evoked eye position, preferred direction of single neurons, and direction of saccades are in good agreement when the eyes are in primary position at the onset of stimulation. But direction and amplitude of electrically induced saccades change with changing initial eye position to bring the eyes to a constant position. This indicates that the stimulation point determines eye position with reference to the cat's head or body. In a few instances, electrical stimulation elicited nystagmus or suppressed spontaneous nystagmus.
Published Version
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