limbic system: the old cortex or paleocortex, as contrasted with the neocortex, of the brain. Its functions pertain to those aspects of the human mind and behavior that are shared by lower, especially mammalian species.

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The limbic system is a collection of interrelated structures that have been found to play a major role in human drives and emotions, such as homeostasis, eating, sleeping, sexual behavior, endocrine control, motivation, memory, and many other functions. It consists of of a network of neurons that form a ring around the upper part of the diencephalon, and includes parts of the thalamus, hypothalamus, hippocampus, amygdala, caudate nucleus, septum, and midbrain.

The "emotional center" of the brain, the limbic system, is a set of midbrain structures involved with emotions, sexual behavior, eating behavior, memory and other functions.


In 1937 J. Papez theorized that emotions are controlled by a set of brain structures (the Papez Circuit). The Papez Circuit includes the thalamus, hypothalamus, cingulate gyrus and hippocampus.

In 1949, Paul MacLean expanded upon Papez Circuit, calling it the limbic system. He discovered that in mammals, the relative size of the limbic system was the same. From these findings he concluded that the limbic system (the Papez-MacLean Circuit) controlled all primitive functions shared by mammals.

Circuits of the Limbic System

MacLean proposed that there are three main "sub circuits" of the limbic system.

  1. Survival Circuit: amygdala and hippocampus
  2. Pleasure Circuit: cingulate gyrus, septum and part of hypothalamus
  3. Social Circuit: thalamus and hypothalamus
The limbic system is also associated with memory function, as it provides the emotional association with a memory.

Klein, Stephen B. Biological Psychology New Jersey, Prentice Hall, 2000.

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