CEREBRAL STRUCTURES INVOLVED IN TRANSMISSION AND ELABORATION OF NOXIOUS STIMULATION

Abstract

A peripheral noxious stimulus evoked in the monkey a typical pattern of response which includes defensive and offensive movements, vocalization, and autonomic manifestations. Conditioning is possible with such stimulation. The aim of this investigation was to study which areas of the brain could produce a similar pattern. Monkeys and a smaller number of cats were studied for about a 2 month period each by means of permanently implanted multilead electrodes. Electrical stimulation of the lateral part of the tegmentum, the central gray, the posteroventral nucleus of the thalamus, the cms of the fornix and the posterior part of the hippocampus elicited the typical pattern. Stimulation of other brain areas, including the sensorimotor cortex, did not evoke these reactions. A technique for chemical stimulation of the brain by remote control is described. Injection of acetylcholine into the tegmental part of the pons did not evoke the typical pattern. In the cat, electrical stimulation of the tectal area induced fighting against control animals, showing that the offensive reaction was purposive and well oriented. The fact that a similar pattern was induced by stimulation of the above mentioned structures suggests a close functional relationship. The so-called sensory cortex would have a less important role than the thalamus and hippocampus in nociceptive sensory integrations.