Corticovisceral Relations

the natural functional interaction between the cerebral cortex and the internal organs, or viscera, which can also be induced under experimental conditions.

Electric excitation of the cerebral cortex carried out at the end of the 19th century (V. la. Danilevskii, N. A. Mislavskii, V. M. Bekhterev) was shown to affect the viscera. It was also found that stimulation of certain cortical zones alters respiration, cardiac activity, and motility of the intestine and urinary bladder. The use of I. P. Pavlov’s method of conditioned reflexes to study the central regulation of visceral activity enabled Pavlov’s students (K. M. Bykov and co-workers) to demonstrate that the cerebral cortex can affect the functioning of all of the internal organs or their systems (blood circulation, respiration, and so forth) and that visceral activity can alter cortical functioning. Thus, the repeated introduction of water into the rectum of dogs increases the amount of urine excreted by the kidneys. This effect can be elicited by the experimental circumstances themselves—for ex-ample, placing the dog in the room where the experiments were performed, introducing and immediately removing the water from the rectum, or having experimenters present (K. M. Bykov et al., 1926). Thus, the experimental circumstances become a conditioned stimulus for the animal. The activity of any internal organ can be modified by creating similar conditioned reflexes (which differ in no way from the classical reflexes discovered by Pavlov). The cerebral cortex is an indispensable participant in the creation of conditioned reflexes—proof that the cortex can affect the functioning of the viscera and their systems.

It was subsequently shown that the conditioned-reflex activity of the cerebral cortex can be changed by affecting a given visceral organ. If such an action is preceded several times by the presentation of a given indifferent stimulus, then that stimulus, when used by itself, can change conditioned-reflex activity—that is, it can become a conditioned stimulus. Thus, it was found that the cortex can influence the activity of the viscera and that signals from the viscera, on reaching the cortex under certain conditions, can change the activity of the highest division of the central nervous system.

K. M. Bykov believed that the cerebral cortex can either change the ongoing activity of the viscera (corrective influences) or stimulate a physiologically dormant organ to activity (triggering influences).

The concept of corticovisceral relations made it possible to explain, from a strictly scientific standpoint, many unexplained facts long known to physiologists and physicians. It helped to elucidate the role of mental influences on the course of certain diseases. It stimulated research by neuromorphologists, who discovered and described visceral sensory nerve endings, or interceptors—the first link in the chain of processes that enables the viscera to affect cortical activity. The theory of visceral interoception and sensitivity was based on the concept of corticovisceral relations. Proof that the visceral organs are represented in the cerebral cortex (projection zones) was an important stage in the elaboration of the theory of corticovisceral relations. All this was the basis of the idea that certain diseases are corticovisceral in nature. This idea has been confirmed by a number of clinical studies (corticovisceral pathology).

The concept of corticovisceral relations marked a further development of Pavlov’s theory of higher nervous activity. However, in the light of recent studies, the concept of corticovisceral relations needs to be considerably supplemented. The cerebral cortex was once believed to regulate the activity of the viscera at all levels of their organization. Modern thinking, based on control theory, is less certain that all of the processes in the body are directly controlled by the cortex. Many diseases (especially infections) cannot be satisfactorily explained as disruptions of normal corticovisceral relations. Moreover, a more important place in current concepts is given to the endocrine system, a powerful factor regulating the physiological systems of animals and man. The role of the other divisions of the central nervous system (notably, the hypothalamus), which constitute the inter-mediate link between the cerebral cortex and the viscera, also demands more thorough study.