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It has been suggested that Reptilian complex be merged into this article or section. (Discuss) |
The triune brain is a model proposed by Paul D. MacLean to explain the function of traces of evolution existing in the structure of the human brain. In this model, the brain is broken down into three separate brains that have their own special intelligence, subjectivity, sense of time and space, and memory[1]. The triune brain consists of the R-complex, the limbic system, and the neocortex. Though still popular among some psychiatrists, the triune brain model is not accepted by researchers in comparative, evolutionary neuroanatomy[2]
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The R-complex
The R-complex, also known as the "Reptilian brain", includes the brain stem and cerebellum. The term "Reptilian brain" comes from the fact that a reptile's brain is dominated by the brain stem and cerebellum which controls instinctual survival behaviors and thinking. This brain controls the muscles, balance and autonomic functions (e.g. breathing and heartbeat).[1] It is, thus, primarily reactive to direct stimuli.
The limbic system
MacLean first introduced the term "limbic system" in a paper in 1952. This portion of the brain derives from "the old mammalian brain"[1]. The limbic system is the source of emotions and instincts (e.g.. feeding, fighting, fleeing, and sexual behaviour). When this part of the brain is stimulated, such as by mild electric current, emotions are produced.
MacLean observed that everything in the limbic system is either "agreeable or disagreeable." Survival is based upon the avoidance of pain (disagreeable) and the recurrence of pleasure (agreeable)[1].
The limbic system comprises the amygdala, the hypothalamus, and the hippocampus. The limbic system must interact with the neocortex in some way. The limbic system cannot function entirely on its own. It needs to interact with the neocortex to process the emotions.[dubious ][citation needed]
The neocortex
The neocortex, also known as the cerebral cortex, is found in the brain of higher mammals, and is responsible for higher-order thinking skills, reason, speech, and sapience.
See also
References
- ^ a b c d Kazlev, et al., M. Alan (2003-10-19). "The Triune Brain.". KHEPER. http://www.kheper.net/topics/intelligence/MacLean.htm. Retrieved on 2007-05-25.
- ^ Patton, Paul (December, 2008). "One World, Many Minds: Intelligence in the Animal Kingdom". Scientific American. http://www.sciam.com/article.cfm?id=one-world-many-minds. Retrieved on 29 December 2008. "The traditional ideas about sequential brain evolution appeared, for example, in the late neuroscientist and psychiatrist Paul D. MacLean’s triune brain model, formulated in the 1960s. MacLean’s model promoted the belief that the human brain contains a “reptilian complex” inherited from reptilian ancestors. Beginning in the 1980s, the field of comparative neuroanatomy experienced a renaissance. In the intervening decades evolutionary biologists had learned a great deal about vertebrate evolutionary history, and they developed new and effective methods of applying Darwin’s concept of the tree of life to analyze and interpret their findings. It is now apparent that a simple linear hierarchy cannot adequately account for the evolution of brains or of intelligence."
Further reading
- Gardner, Russell; Cory, Gerald A. (2002). The evolutionary neuroethology of Paul MacLean: convergences and frontiers. New York: Praeger. ISBN 0-275-97219-4. OCLC 49649452.
- Kral, V. A.; MacLean, Paul D. (1973). A Triune concept of the brain and behaviour, by Paul D. MacLean. Including Psychology of memory, and Sleep and dreaming; papers presented at Queen's University, Kingston, Ontario, February 1969, by V. A. Kral [et al.. Toronto]: Published for the Ontario Mental Health Foundation by Univ. of Toronto Press. ISBN 0-8020-3299-0. OCLC 704665.
- MacLean, Paul D. (1990). The triune brain in evolution: role in paleocerebral functions. New York: Plenum Press. ISBN 0-306-43168-8. OCLC 20295730.
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