The Triune Brain Theory

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Paul Pierre Broca talked about ‘le grand lobe limbique’ in 1878 or the great limbic lobe and used the term “limbic” (from the Latin limbus for border) to the rounded rim of the cortex which also has the cingulate and the parahippocampalgyri. However, its supposed role in emotion was elaborated by the American physician, James Papez in 1937 in the influential paper titled ‘A proposed mechanism of emotion’. This anatomical model is called the Papez circuit.[2] In the year of 1948 scientist Yakovlev proposed Yakovlev's circuit in the command of emotions involving the anterior, insular, , temporal , orbitofrontal and lobe cortex, the dorsomedial nucleus of thalamus and amygdala.[3] In 1952, Paul D. MacLean used the name “limbic system” to describe Broca's limbic lobe and related subcortical nuclei as the combined neural substrate for emotion.[1] He was also pivotal in the proposal and definition of the Triune concept of the brain. MacLean's evolutionary “Triune brain theory” proposed that the in reality what we believe to be one brain was in fact three brains encased in one.: limbic system, R-complex (reptilian complex), and the neocortex.[4] The idea of the limbic system has since been further extended and evolved by Nauta, Heimer and others.
FUNCTIONAL CIRCUITRY
Papez circuit
James Papez's description of a circuit after the injection of the rabies
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It is located in the temporal lobe’s medial aspect, forming the medial wall of the lateral ventricle in this region. The hippocampus has many parts. The dentate gyrus has granule cells which are thickly packed cells. Then we have a rounded area of cortex called the CornuAmmonis (CA) that is separated into four areas called the CA fields. These are called CA1 to CA4. They have prominent pyramidal cells. The CA fields merge into the neighboring subiculum, which, in turn, is linked to the entorhinal cortex on the parahippocampalgyrus of the temporal

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