Effects of brain-stem stimulation upon hippocampal electrical activity, somatomotor reflexes and autonomic functions

Abstract

In order to understand better the functional significance of hippocampal electrical activity, an attempt has been made to relate its changes with those of somatomotor, sudomotor and vasomotor activities. Experiments were conducted with locally anesthetized cats under Flaxedil. The animals were bilaterally vagotomized in the study of blood pressure. Four types of hippocampal electrical responses to the stimulation of various subcortical brain structures were observed. 1. 1. “Synchronization” (produced by the stimulation of the medial preoptic area, the medial hypothalamic region and the dorsolateral part of the midbrain tegmentum) was associated with facilitation of the monosynaptic gastrocnemius and mono- as well as polysynaptic peroneal reflexes, elevation of blood pressure and facilitation of skin potentials. 2. 2. “Desynchronization A” (elicited by the stimulation of the amygdala and the lateral preoptic area) was associated with inhibition of the gastrocnemius and peroneal reflexes, and depression of blood pressure. The skin potentials could be facilitated with strong stimulation. 3. 3. “Desynchronization B” (elicited by the stimulation of the bulbar ventromedial reticular formation) was associated with inhibition of the gastrocnemius and peroneal reflexes, skin potentials and elevation of blood pressure. However, depression of the latter was obtained after Nembutal administration. 4. 4. “Intermediate response” (elicited by the stimulation of the posterolateral hypothalamic region and the preoptic area) was associated with facilitation of the peroneal reflexes and of the skin potential, and with inhibition of the gastrocnemius reflex. Blood pressure, elevated in the absence of anesthesia, was depressed after Nembutal administration. In view of these experimental results, it is suggested that the slow wave components of hippocampal electrical activity might have a close relationship with somatomotor and vasomotor activities.