EFFECT OF CORTICAL LESIONS ON AFFECTIVE PUPILLARY REACTIONS

Abstract

The threshold necessary to elicit the reflex dilation of the pupil, effected by oculomotor inhibition, was studied in 8 trained unanesthetized cats with unilateral lesions of the sensory or sensori-motor cortex representing the hind leg. This cortical deficit caused no significant difference in comparison with the normal side. The threshold was detd. by alternate unipolar stimulation of the right and left hind toe pads. Of 26 expts. done on 2 animals with massive unilateral cortical lesions, 19 showed the ablated side significantly hyperactive. Since the sensory level determining the indicator reaction is subcortical, probably thalamic, while the hypothalamus gives this reaction by direct stimulation, its significance as a diencephalic indicator is discussed. Direct cortical stimulation in cats without narcosis gave 3 fields yielding the inhibitory pupillary reaction; a frontal, temporal and occipital. These are identical with fields giving inhibition of extra-pyramidal movement. No sympathetic pupillary reaction was cortically elicited. A scheme for pupillary reactions is outlined, in which nuclear events, excitatory and inhibitory, occurring at the Edinger-Westphal nucleus, determine pupillary variability. In addition, a non-reflexly activated component of pupillary constriction is indicated. Histological studies of representative exptl. animals are included.