Interaction of visceral and somatic afferent systems in the cerebral cortex

Using the method of evoked potentials on chloralose-anesthetized and suxamethonium-immobilized cats, a comparative study was made of the effects of interaction of somatic and visceral afferent systems in the second somatosensory area and in the parietal cortex of the brain. It was found that a common property of the interaction of the two afferent systems is an inhibition of the second response irrespective of which of the systems is activated first. Fairly prolonged inhibition was noted in the association region of the parietal cortex. Preliminary stimulation of visceral nerves caused less prolonged depression on subsequent stimulation of somatic nerves both in the second somatosensory and in the association regions of the cortex. It was demonstrated that the anatomic coincidence of visceral and somatic afferent projections both in the second somatosensory and in the parietal regions of the cortex is evidently responsible for the interaction of these afferent systems.