EFFECTS OF HYPOTHALAMIC AND RETICULAR STIMULATION ON EVOKED RESPONSES IN VISUAL SYSTEM OF CAT

The purpose of this experiment was to compare the changes induced by reticular stimulation in the magnitude of evoked responses of the visual system of the cat with the changes occurring during stimulation of two areas in the hypothalamus, each of which directed the cat's attention to specific visual stimuli. The responses of the lateral geniculate body, optic radiation, superior colliculus, and visual cortex evoked by a shock to the optic tract and the response of the visual cortex evoked by an optic radiation shock were recorded in the absence of any other electrical stimulation of the brain and when preceded by 100 msec trains of either reticular stimulation, stimulation of the lateral hypothalamus, or stimulation of the medial hypothalamus. In some subjects large bilateral reticular lesions were made so that the effects of loss of reticular function on the changes in evoked potential amplitude induced by hypothalamic stimulation could be assessed. It was found that: 1. 1. Hypothalamic and reticular stimulation significantly increased the amplitude of evoked responses recorded from the lateral geniculate body, optic radiation, and superior colliculus. 2. 2. The cortical response evoked by stimulating the optic radiation was depressed by hypothalamic stimulation and facilitated by reticular stimulation. 3. 3. The cortical response evoked by stimulating the optic tract was facilitated by low intensities and depressed by high intensities of hypothalamic stimulation. Reticular stimulation facilitated the cortical evoked response at all intensities. 4. 4. Lesions of the reticular formation did not alter either the facilitatory effect of hypothalamic stimulation at the subcortical level or its depressive effect at the cortex. 5. 5. Stimulation of the lateral hypothalamus which elicited quiet attack directed at a rat and stimulation of the medial hypothalamus which elicited affective attack directed at the experimenter or at the rat had the same effects on visual evoked potentials. © 1968.