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limbic system[′lim·bik ‚sis·təm]
rhinencephalon, a group of sections of the brain that are unified by anatomic (spatial intercommunication) and functional (physiological) characteristics. The major part of the system consists of structures of the hippocampal gyrus, a series of successively connected brain formations that form a closed cycle and are connected to the paleopallium, archipallium, and neopallium (all located predominantly on the inner surface of the hemispheres) and to subcortical formations.
The limbic system participates in olfactory function and in regulating the activity of the body’s visceral systems; when different areas of the limbic system are stimulated electrically, changes can be observed in the operation of the various internal organs, such as the heart, the vessels, and the gastrointestinal tract. However, the principal function of the limbic system is associated with autoregulatory processes in the organization of behavior and mental activity. The system is responsible for the instinctual behavior associated with the satisfaction of innate organic requirements, such as self-preservation, food gathering, eating and drinking, sexual behavior, and the rearing of offspring.
The limbic system also has an important role in the organization of acquired forms of behavior; this is associated with the system’s special role in emotional reaction, the processes of memory, and the regulation of the states of wakefulness and sleeping. By stimulating or destroying various areas of the limbic system, one can produce or eliminate emotions, such as fear or rage. In experiments with autostimulation, in which an animal can, by pressing a pedal, repeatedly (up to 8,000 times an hour) stimulate certain structures of the limbic system through implanted electrodes, there arises an expressed sensation of satisfaction (the positive reinforcement of an action). Upon the introduction of electrodes to other structures, the animal is observed to avoid such autostimulation, because of the appearance of a feeling of dissatisfaction (negative reinforcement).
The role of the limbic system has been elucidated in the processes of memory in which there is a transfer of traces of acquired experience from short-term to long-term memory. In man, bilateral damage to the limbic system (for example, by brain tumors and certain intoxications, such as with alcohol) leads to an impairment of the function and a loss of memory for new occurrences (called Korsakoff’s syndrome). Such damage may also result in emotional disturbances.
Different parts of the limbic system participate to different degrees in various brain functions. However, all of the basic functions and structures are closely interconnected, and, taken together, they ensure in integral brain activity (motor, perceptive, cognitive) the active, purposeful character of a given action.
REFERENCESStruktura i funktsiia arkhipaleokorteksa. Moscow, 1968. (Gagrskie besedy, vol. 5.)
Fiziologiia i patofiziologiia limbiko-retikuliarnoi sistemy. Moscow, 1971.
Structure and Function of the Limbic System. Amsterdam-London-New York, 1967. (Progress in Brain Research, vol. 27.)
Karli, P. “Système limbique et processus de motivation.” In Association des physiologistes. Paris, 1968. (Journal de physiologic vol. 60, supplement 1.)
L. P. LATASH