Limbic system description

From this brief description, it is apparent that the brain is really an assembly of organs all of which are structurally and functionally interconnected. Undoubtedly one of the most important areas for the psychopharmacologist is the so-called limbic system which is concerned with emotion. This region consists of the hippocampus (concerned with memory... 

This data, coupled with numerous positive outcome studies of the effectiveness of antidepressants, has led to the development of the monoamine (or biogenic amine) hypothesis of depression. The theory holds that depressive symptoms are ushered in by a malfunction of either norepinephrine (NE) or serotonin (5-HT) neurons, which play critical roles in the functioning of the limbic system and the adjacent hypothalamus. The basic neuronal malfunction is felt to be identical for either NE or 5-HT neurons, thus what follows (a description of the pathophysiology of NE neurons) can also be seen to occur in individuals in whom 5-HT neurons are affected. For reasons that are not well understood, patients with major depression (with vegetative symptoms) appear to suffer from either NE or 5-HT dysfunction, but probably not both simultaneously (although some exceptions exist). 

A mathematical relationship between the components of brain limbic system was proposed by Moren and Balkenius (2000) from the descriptive physical model of the limbic system that provides a qualitative sense of the overall functioning of the system. Figure 2 shows the structure of the Moren-Balkenius computational BEL model. As depicted in the figure, the BEL model has four components of the so-called limbic system of the brain amygdala, orbitofrontal cortex, sensory cortex and thalamus. Of them, amygdala and orbitofrontal cortex perform an important function in emotional processing (Moren and Balkenius 2000). 

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