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MacLean's Triune Brain Nonsense?

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Unknown

Jun 27, 2004, 03:55 PM

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Is MacLean's Triune Brain concept utter nonsense with no basis in neuroscience? I'm inclined to think it is, and have been told as much from many neuroscientists. Yet, the triune brain concept remains popular with laymen and the general public. Why is this? Here's an excerpt from a pro-MacLean site over his Triune Brain theory, to give you an idea of what his theory is all about.

QUOTE

The neurologist Paul MacLean has proposed that our skull holds not one brain, but three, each representing a distinct evolutionary stratum that has formed upon the older layer before it, like an archaeological site :He calls it the "triune brain." MacLean, now the director of the Laboratory of Brain Evolution and Behaviour in Poolesville, Maryland, says that three brains operate like "three interconnected biological computers, [each] with its own special intelligence, its own subjectivity, its own sense of time and space and its own memory". He refers to these three brains as the neocortex or neo-mammalian brain, the limbic or paleo-mammalian system, and the reptilian brain, the brainstem and cerebellum (see above diagram). Each of the three brains is connected by nerves to the other two, but each seems to operate as its own brain system with distinct capacities.

This hypothesis has become a very influential paradigm, which has forced a rethink of how the brain functions. It had previously been assumed that the highest level of the brain, the neocortex, dominates the other, lower levels. MacLean has shown that this is not the case, and that the physically lower limbic system, which rules emotions, can hijack the higher mental functions when it needs to.

It is interesting that many esoteric spiritual traditions taught the same idea of three planes of consciousness and even three different brains. Gurdjieff for example referred to Man as a "three-brained being". There was one brain for the spirit, one for the soul, and one for the body. Similar ideas can be found in Kabbalah, in Platonism, and elsewhere, with the association spirit - head (the actual brain), soul - heart, and body in the belly. Here we enter also upon the chakra paradigm - the idea that points along the body or the spine correspond to nodes of consciousness, related in an ascending manner, from gross to subtle.

The Reptilian Brain. The archipallium or primitive (reptilian) brain, or "Basal Brian", called by MacLean the "R-complex", includes the brain stem and the cerebellum, is the oldest brain. It consists of the structures of the brain stem - medulla, pons, cerebellum, mesencephalon, the oldest basal nuclei - the globus pallidus and the olfactory bulbs. In animals such as reptiles, the brain stem and cerebellum dominate. For this reason it is commonly referred to as the "reptilian brain". It has the same type of archaic behavioural programs as snakes and lizards. It is rigid, obsessive, compulsive, ritualistic and paranoid, it is "filled with ancestral memories". It keeps repeating the same behaviours over and over again, never learning from past mistakes (corresponding to what Sri Aurobindo calls the mechanical Mind). This brain controls muscles, balance and autonomic functions, such as breathing and heartbeat. This part of the brain is active, even in deep sleep.

The Limbic System (Paleomammalian brain). In 1952 MacLean first coined the name "limbic system" for the middle part of the brain. It can also be termed the paleopallium or intermediate (old mammalian) brain. It corresponds to the brain of the most mammals, and especially the earlier ones. The old mammalian brain residing in the limbic system is concerned with emotions and instincts, feeding, fighting, fleeing, and sexual behaviour. As MacLean observes, everything in this emotional system is either "agreeable or disagreeable". Survival depends on avoidance of pain and repetition of pleasure.

When this part of the brain is stimulated with a mild electrical current various emotions (fear, joy, rage, pleasure and pain etc) are produced. No emotion has been found to reside in one place for very long. But the Limbic system as a whole appears to be the primary seat of emotion, attention, and affective (emotion-charged) memories. Physiologically, it includes the the hypothalamus, hippocampus, and amygdala. It helps determine valence (e.g., whether you feel positive or negative toward something, in Buddhism referred to as vedena - "feeling") and salience (e.g., what gets your attention); unpredictability, and creative behaviour. It has vast interconnections with the neocortex, so that brain functions are not either purely limbic or purely cortical but a mixture of both.

MacLean claims to have found in the Limbic system a physical basis for the dogmatic and paranoid tendency, the biological basis for the tendency of thinking to be subordinate feeling, to rationalize desires. He sees a great danger in all this limbic system power. As he understands it, this lowly mammalian brain of the limbic system tends to be the seat of our value judgements, instead of the more advanced neocortex. It decides whether our higher brain has a "good" idea or not, whether it feels true and right.

The Neocortex, cerebrum, the cortex , or an alternative term, neopallium, also known as the superior or rational (neomammalian) brain, comprises almost the whole of the hemispheres (made up of a more recent type of cortex, called neocortex) and some subcortical neuronal groups. It corresponds to the brain of the primate mammals and, consequently, the human species. The higher cognitive functions which distinguish Man from the animals are in the cortex. MacLean refers to the cortex as "the mother of invention and father of abstract thought". In Man the neocortex takes up two thirds of the total brain mass. Although all animals also have a neocortex, it is relatively small, with few or no folds (indicating surface area and complexity and development). A mouse without a cortex can act in fairly normal way (at least to superficial appearance), whereas a human without a cortex is a vegetable.

The cortex is divided into left and right hemispheres, the famous left and right brain. The left half of the cortex controls the right side of the body and the right side of the brain the left side of the body. Also, the right brain is more spatial, abstract, musical and artistic, while the left brain more linear, rational, and verbal.

Replies

Jakare	Mar 16, 2012, 11:47 AM Post #2
Demi-God Group: Basic Member Posts: 581 Joined: Feb 24, 2010 Member No.: 32635	If we are going to split the brain appart we should say there are 5 two 7 different brains depending upon if we want to think of the limbic system as divided in hemispheres or not like the neocortex is and counting the cerebellum aswell. The cerebellum itself is a really complex structure and is divided in two aswell. But the more relevant division between brain structures is right and left hemispheres IMO hands down. The studies about corpus callosotomy are deeply amazing about how differently those two little fellas inside us can have a very different point of view. http://www.intropsych.com/ch02_human_nervo..._operation.html

Posts in this topic

Unknown MacLean's Triune Brain Nonsense? Jun 27, 2004, 03:55 PM

rhymer I hadn't realised Mclean was the source of thi... Jun 27, 2004, 04:03 PM

Unknown MacLean makes appeals to evolutionary theory too... Jun 27, 2004, 04:18 PM

Paul King Actually, I believe there is a lot to this idea. ... Oct 09, 2005, 10:32 PM

Rick Perhaps if we think we understand the brain we hav... Oct 10, 2005, 10:40 AM

Hey Hey Is there any palaeontological record to support t... Oct 10, 2005, 02:55 PM

Rick The crocodilians have had similar body form for 30... Oct 11, 2005, 09:47 AM

Hey Hey Agreed. This is a job for Shawn!? Oct 13, 2005, 06:57 PM

rhymer There is a lot of possibly relevant (at least rela... Oct 14, 2005, 12:00 PM

Unknown good link! Oct 14, 2005, 03:24 PM

Hey Hey thanks rhymer. certainly a good start. Oct 15, 2005, 12:39 PM

Paul King Certainly! Although while the older parts h... Oct 17, 2005, 12:59 AM

Enki Oho! Oct 29, 2005, 03:30 PM

Unknown Hi Enki, are these the three layers? Obsolete. H... Oct 29, 2005, 04:03 PM

Enki Hi Unknown, Oho means oho my dear. ;) Bests, Enk... Oct 30, 2005, 01:51 AM

rhymer Thanks Enki, but I must admit, I thought that was ... Oct 30, 2005, 04:15 PM

Enki You are welcomed! Keep in secret that you ha... Nov 06, 2005, 12:40 PM

Unknown Actually, I believe there is a lot to this idea. ... Nov 24, 2005, 12:08 PM

avisolo Read what Maclean himself said about it here: http... Jan 14, 2006, 10:54 PM

Unknown It's a good link and makes for an interestin... Jan 15, 2006, 01:11 AM

Paul King It's a good link and makes for an interesti... Mar 15, 2006, 02:03 PM

lucid_dream Paul MacLean should have recanted his utterly ridi... Sep 19, 2006, 07:38 PM

TaylorS IMO the Triune Brain hypothesis is at most, a prof... Jan 31, 2008, 06:54 PM

Robert B. Mounts Let's examine the question from a different po... May 16, 2011, 11:29 AM

dtubin Let's examine the question from a different p... Mar 16, 2012, 06:14 AM

Flex IMO the only thing of importance to take away from... Mar 16, 2012, 06:57 AM

Jakare If we are going to split the brain appart we shoul... Mar 16, 2012, 11:47 AM

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