PATTERNS OF COMPETITIVE INTERACTION OF ELECTRICALLY EVOKED EYE MOVEMENTS IN CATS

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Abstract
Eye movements of ence''phale isole cats, evoked by simultaneous stimulation of 2 opposing sites, have been analyzed from cinematographic recordings. Algebraic summation, evidenced by ocular movement to an intermediate position, resulted from bilateral stimulation of homotopic sites in 3 brain stem areas and occipital cortex, and from simultaneous stimulation of one zona incerta with either the opposite superior colliculus or the ipsilateral medulla. Ocular positions could be graded by varying the relative intensity of stimulation to the 2 sites. Simul taneous stimulation of one dorsal midbrain tegmentum with the opposite superior colliculus resulted in algebraic summation, but with a tendency toward tegmental dominance. Oscillation resulted from simultaneous stimulation of medulla and dorsal midbrain tegmentum, with a tendency toward dominance by the medulla. With simultaneous stimulation of one zona incerta and the opposite dorsal midbrain tegmentum, the eye moved first to one side, then to the other. All 4 brain stem areas dominated the opposing occipital cortex. Results are discussed in terms of implications of gradation of evoked eye movements, and of degrees of relative functional dominance among the areas tested.