FACILITATION AND ADDITION OF ELECTRICALLY EVOKED EYE MOVEMENTS IN CATS

Abstract

Eye movements obtained from simultaneous and separate stimulation of pairs of brain stem or cortical sites, each individually yielding a conjugate ocular movement to the right, have been analyzed cinematographically. The effect of combined stimulation was considered to be (a) facilitation, indicative of spatial summation; (b) addition, suggesting separate paths to the eye motor nuclei; or (c) occlusion, suggestive of shared paths from the two stimulated sites. Facilitation of evoked eye movement was obtained on simultaneous stimulation of a site in the left dorsal midbrain tegmentum with one in the right medulla, the left superior colliculus, or the left zona incerta. Addition was seen with stimulation of the left superior colliculus with either the right medulla or the left zona incerta. More than one pattern of response was found with each of the following pairings: left zona incerta and right medulla; left occipital cortex and any brain stem area (left dorsal midbrain tegmentum, right medulla, left zona incerta or left superior colliculus.).