Motivation and emotion/Book/2020/Triune brain theory and emotion

Triune brain theory and emotion:
What is the triune brain theory and what are its implications for human emotion?

Multimedia presentation (3 min)

Overview

Triune Brain Theory is one of the underpinning theories for modern neuropsychology. It attempts to explain evolution and reconcile human behaviour with a more primal and violent side (Pearce, 2008). It attempts to explain why is there a human tendency to shed tears in connection with acts of altruism or why humans are the only animals able to cry. The mind will rarely perceive anything as neutral, every action, object or experience has some perception of pleasant or unpleasant (Loye, 2002). These affects allow for subjective experience of emotional feelings. So what is the Triune Brain process behind our perceptions and behaviours? Where did these historically originate? And how is this relevant in our current society? This chapter explores how the Triune Brain interprets every affect from subjective experiences and thereby impacting our behaviour and emotion.

Focus questions: What is the Triune brain theory? What is emotion? What is the implication of the brain injury on emotion? What is the emotional involvement underpinning religion? How does this relate to Triune brain theory?

What is the Triune brain theory?

Reptilian Brain

Shared among all creatures, the reptilian brain is the survival brain (Bath, 2005). Also known as the R-Complex, the reptilian brain is the fundamental core of the nervous system based on the evolution of a mammalian-like reptile that once populated the earth. It develops first, consisting of the spinal cord and cerebellum; controlling motor behaviour, emotional calming and automatic functions such as fight or flight, heart rate and other reflexive and instinctive behaviours (Bath, 2005). This area of the brain is responsible for innate behaviours such as selecting homesites, establishing territories and engaging in hunting, mating and forming social hierarchies (Ernandes & Giammanco, 1998).

Old Mammalian Brain

This area of the Triune Brain is comprised of the olfactory bulb, hippocampus, amygdala, cingulate gyrus and other areas commonly associated with the limbic system (Ernandes & Giammanco, 1998). The old mammalian brain serves as a regulator for the R-Complex by suppressing the innate survival behaviour, coining the term the emotional brain. The limbic system adds emotion to activities; such as fear, anger and love (Ernandes & Giammanco, 1998; Bath, 2005). It categorises pleasurable from threatening stimuli through the amygdala (or danger detector) which is situated above the hippocampus which stores emotionally charged events in our memories. The purpose being to motivate action; to avoid, attack or approach (Bath, 2005).

New Mammalian Brain

The final component of the Triune Brain theory is the New Mammalian brain, concerned with the neocortex and connected brainstem structures. Current research extensively covers these nervous structures, yet the amount known does not equate (Ernandes & Giammanco, 1998). What is known is that the neocortex allows individuals to predict the future, assisting individuals in tackling new and unexpected situations. A capacity of induction to phenomena allows for causal and rational connections to be made, drawing from an individual’s knowledge. Essentially, conscious thought unique to humans; self-consciousness, space and time conceptions and connections of causality and constancy (Ernandes & Giammanco, 1998).

Both the R-Complex and limbic system have mutual influence on New Mammalian brain activity (Ernandes & Giammanco, 1998). Magical thought is described as ideas that are not verifiable, characterised by illogicality and held by faith. The Triune Brain explains how magical thought begins in the R-Complex in unconscious origins, made conscious and rational by the Neocortex, and finally emotional by the limbic system (Ernandes & Giammanco, 1998). It’s clear to see how the entire Triune Brain can establish causal connections and explain phenomena, such as magical thought.

"In describing the functions of the triune brain metaphorically, one might imagine that the reptilian brain provides the basic plots and actions; that the limbic brain influences emotionally the developments of the plots; while the neomammalian brain has the capacity to expound the plots and emotions in as many ways as there are authors" (MacLean, 1977, 218)

Historical Origins

Paul MacLean

The origins of this theory come from neuroscientist and psychiatrist Paul Maclean. In the late 1940’s, Maclean developed an interest with the brain’s control over emotions and behaviour (Pearce, 2008). He began to search for the psychological source of behaviours such as aggression and sexual arousal, by doing so he termed the brain’s centre of emotions as the limbic system.

By the 1960’s, Maclean’s theory grew to describe the overall structure of the brain, completing the theory of the Triune Brain: The limbic system, the R-complex and the Neocortex (Pearce, 2008). The theory was popularised during the 1970-80’s by astronomers and novelists; although still controversial to many, much of the research in neuroscience has been enabled by Maclean’s theory.

Antiquity influence

Throughout Western culture history, the numbers three and seven have been favoured. The Pythagoreans’ obsession with numerology led them to believe that seven was a significant number throughout life; second set of teeth at age 7, hit puberty at age 14; man’s beard at 21. Furthermore, there are seven heavenly objects (Smith, 2010). Evidence throughout history suggests that the number three, or tripartite classifications, is natural. Have you ever heard the story of the three blind mice or the three little piglets?

Even throughout neuropsychology this classification can be identified. Freud defined the superego, ego and id; Mendelssohn divided the human psych into cognition, affection and conation; Pavlov determined signalling systems, conditioned reflexes and unconditioned reflexes. Neuropsychology has notably been divided into triune across a multitude of key figures. But how far back can this trend be traced?

Plato

Plato’s later work of Timaeus in 360s BCE stratifies society into three levels: The Guardians, which possess wisdom and cool reason; the Warriors, which have passionate, courageous but also short-tempered warlike virtues; and the Proletariats, which display the low-grade characteristics of avarice and greed (Smith, 2010). The Proletariats are protected by the Guardians and Warriors, requiring the two to cooperate and communicate. Plato infers that the societal organisation he proposed can be applied to the structure of the soul (Smith, 2010). Was this the origins of the tripartite neuro-psychologies that structured the Western mindset?

Aristotle

Aristotle took a different approach to Plato, exploring the tripartite division of the soul from his extensive knowledge of biology rather than from politics or society. Aristotle recognised the complexity and high organisation of all living things. His dedication to life sciences coloured his whole philosophy and, unlike contemporary scientists, did not seek to reduce life science to mechanistic physics (Smith, 2010). Instead, he attempted to understand physics as a quasi-biology, particularly through using embryology as his metaphor. He comprehensive studies of the development of chicken eggs allowed him to conclude that the soul is not separate from the body; the soul is the actuality of the body or the matter that merely possessed the potentiality of being a body (Smith, 2010).

Erasistratus

Named the father of physiology, Erasistratus contribution is immense. He believed the body was constructed of the arteries, veins and nerves; all inter-braided deep within every individual. Each vessel contained a fluid:

• Veins contained blood; a nutritive fluid manufactured by the liver from digestive processes
• Arteries contained pneuma zotikon, or vital spirit; a rarefied fluid derived from the environing pneuma
  • Respiration, or the process of taking air into the lungs, creates pneuma
• Nerves contained an even more rarefied fluid named pneuma psychikon, or animal spirit which was refined from pneuma zotikon in the brain (Smith, 2010)

Although much more complex and vast knowledge about the body is now known, the origins behind neuro-psychologies present triune compositions. Each antiquity influence is uniquely different, yet share an underlying similarity (Smith, 2010). It is no surprise that the tripartite classifications carried through to Maclean’s theory, refining the Antiquity’s influence and work.

Consider this case study! A study conducted in the 90’s explored the effects of a seizure-inducing injection of lithium and pilocarpine on the maternal behaviour of rats, both with and without direct maternal experience (Peredery, Persinger, Blomme & Parker, 1992). They found that all maternal behaviour was ceased with the subsequent birthing of rats and regular behaviour continued with rats who did not display seizures. Furthermore, other factors such as litter size and mammary function remained unchanged, suggesting that damage to the limbic system and thalamocingulate hinders normal mother-offspring interaction (Peredery et al., 1992). The thalamocingulate is essential for maternal behaviours in mammals. Loye (2002) describes the relevance for behaviours such as lactation, nest building and the entire process of pregnancy. The limbic system is the emotional component to activities; supporting the findings of Peredery et al. (1992) that the innate maternal activities are sustained in the absence of maternal emotions (Ernandes & Giammanco, 1998). These family related behaviours allow us to examine the effects of damage to the thalamocingulate and limbic system. The rats allow us to gain understanding into the emotional element of mammals; damage to these brain areas does not cease activities, rather removes the emotional system surrounding them.

Test your knowledge

1 Which area of the brains is unique to all humans?

	R-complex
	Neocortex
	Amygdala
	Limbic System
	Midbrain

2 The Triune Brain is split into 3 sections. Which section is responsible for adding emotional components to activities?

	Frontal lobe
	Limbic System
	Basal ganglia
	Neocortex
	R-complex

Emotion as a result of Triune Brain Theory

The limbic system, or emotional brain, consists of three overlapping subdivisions (Loye, 2002). The amygdala and septum are the two older subdivisions: the amygdala division is concerned with self-preservation (feeding, attacking, defending) and the septal division is involved in primitive sexual behaviours. The third subdivision, which we will be focusing on, is the thalamocingulate division (Loye, 2002). The development of the pathway of the thalamocingulate progressively increases in primates, and peaks in humans (MacLean, 1977) Emotional behaviour in mammals can be explained by this subdivision in the limbic system, as seen in the Mother Rats case study above! MacLean (1977) attributes 24 prototypical behaviours in mammals with which the Triune Brain supports.

First function of third subdivision

The first function of the thalamocingulate is mother-offspring interactions and behaviours, more commonly known as nursing (Loye, 2002). As seen in Peredery et al. (1992) experiment on mother rats, clusters of maternal behaviour such as lactation, nest building and the process of pregnancy ceased when damage was caused to the limbic system, and more importantly, the thalamocingulate.

Second function of third subdivision

Observing clusters of family-related behaviour in mammals allowed the second function of the third subdivision to be determined: Audio-vocal communication. Unique to mammals, the separation cry is an audio-vocal communication used for maintaining mother-offspring connection (Loye, 2002). Squirrel monkeys even extend this connection to use separation cries to maintain contact with individuals within a group!

Third function of third subdivision

Behavioural play is unique to mammals, no evidence is found at a reptilian level. However, at the mammalian level, behavioural play is exhibited by chasing, mock biting, wrestling and grabbing (Loye, 2002). The thalamocingulate serves behavioural play in mammals as the final function of the third subdivision; developing strength and skills, excreting excess energy, or reflecting acting out of instincts.  

These functions of the third subdivision of the limbic system provide evidence of the emotional behaviour in mammals, from mother-offspring connections to behavioural play. As seen in the mother rats, damage to this area reduces the emotional behaviour, however the reproductive functions such as litter size remained unchanged. The first two subdivisions of the limbic system (amygdala and septum) continued to provide emotionally charged behaviour to the rats (Peredery et al., 1992). The limbic system is a complex division of areas which work collaboratively to produce the emotional brain for mammals.  

Psychosurgery

As an effort to control mental illnesses and other high anxiety states, psychosurgery was developed. The knowledge gained from psychosurgery is unlike any other, however it is now morally and medically deplored (Ernandes & Giammanco, 1998).

Clinically studying patients with frontal lobe injuries has indicated that the prefrontal cortex is responsible for providing foresight into planning for ourselves and others; the what, how and when (Loye, 2002). This function further provides insight into the feelings of others through the neighbouring connection to the limbic system. Therefore, it has been proposed that humans have a ‘neural ladder’, beginning with primitive feelings stemming from the R-Complex, extending to emotional competence and altruistic sentiments from the limbic system and neocortex (Loye, 2002; Ernandes & Giammanco, 1998).

Frontal lobotomies

Our brains work as a whole, all the areas of the Triune Brain combine to create the you that functions from day to day life. So, what would happen if your brain was split in two? Frontal lobotomy was a psychosurgical procedure that separated the frontal brain lobes from the underlying connecting structures (Ernandes & Giammanco, 1998).

Within these underlying structures is the limbic system, which is the emotional brain. It doesn’t come as a shock that these psychosurgeries then led to massive behavioural changes in patients such as post-surgery tactlessness and a tendency to outburst (Loye, 2002). Ongoing behaviour can be suppressed by stimulation of the limbic system; patients who had undergone frontal lobotomies were experiencing these outbursts and tactlessness, as the emotional brain could not suppress the urges of the R-Complex (Ernandes & Giammanco, 1998).

Findings of lobotomies

So, what really happened to these patients post-surgery? Some patients reported feeling unable to feel as before, or that something had died within them (Loye, 2002). Others stated that neither real happiness nor deep sorrow could be experienced, or that they had lost the ability to dream. Commonly, patients experienced forgetfulness, indolence (more commonly known as laziness) and loss of interests or ambitions (Loye, 2002). The mother of a patient reported, “She is my daughter but yet a different person. She is with me in body but her soul is in some way lost. Those deep feelings, the tenderness are gone. She is hard, somehow.” (Loye, 2002, p. 142). In a sense, patients had lost their capacity for inner guidance; through guided thoughts, feelings or behaviours.

An explanation behind the inner guidance loss is the Guidance System for Higher Mind (GSHM) Model, for when sensitivities have been ‘turned off’ (Loye, 2002). The inter-related sensitivities include moral, dialectical or evolutionary, social, systems and managerial. Systems sensitivity and social sensitivity allow an individual to feel grounded in the nature of what presently exists and perceive the world “as it is”. The GSHM model credits the rapid development of cerebrum and frontal brain in humans to develop higher level sensitivities (Loye, 2002). After a frontal lobotomy, where the frontal brain is severed, this ‘neural ladder’ cannot be fulfilled, and sensitivities such as social and systems are ‘turned off’ explaining the feeling of inner guidance loss.

Consider this case study! Figure 1. Illustration of Phineas Gage's head and brain wounds At this point, we’ve covered many areas and functions of the brain. We’ve explored their importance and relevance to both humans and mammals. But what about if your brain is punctured by a steel bar? Are you able to function? Will you still be you? Meet Phineas Gage! The young railroad foreman who has a steel bar puncture right through his frontal lobe as a result of an explosion, from the top front part of his skull to below his left eye (See figure 1). Now using our knowledge from before of frontal lobotomies, and how surgical separation disconnects the “emotionality” of the limbic system, what do you think might happen to Phineas Gage? (Loye, 2002) Frontal areas of the brain, similar to where Phineas was injured, are involved in the what, how and why of everyday scenarios; Phineas’ ability to plan ahead was gone. Further aligning with our previous knowledge of frontal lobotomies and the limbic systems role in emotionality, Phineas also became foul-mouthed and untrustworthy (Loye, 2002). What does this tell us? Well, firstly that we can function after such a traumatic brain injury. Secondly, that the components that makes an individual unique is flexible, Phineas Gage serves as historical proof of that.

Religion: The emotional basis

Religion is a near universal experience, almost every culture has some form that they hold faith to (Ernandes, & Giammanco, 1998). Whether the faith be in a single Divine Being or an entire religion, is it such a stretch to suppose that there is a biological basis underpinning religion? What is there is a genetic predisposition for humans to hold faith? How does this originate? Triune Brain attempts to explain the process of holding faith, how it develops in a universal pattern yet is unique to every individual.

Immense Power Being

The triune brain gives ability for magical thought: ideas that are not verifiable and held by faith (Ernandes & Giammanco, 1998). Similarly to magical thought, an immense power being, or religion begins in unconscious origins in the R-Complex and continues through to the projection and rationalisation executed by the Neocortex (Ernandes & Giammanco, 1998). An immense power being is not thought to be innate in every mind. However, a specific genetic predisposition may support perceiving a Divine Being naturally in human minds Ernandes & Giammanco (1998). Anatomical and physiological structures favour the birth of religious ideas which can become ingrained in a culture and heightened in certain environmental circumstances.

The R-Complex preserves hierarchy-forming structures, which is regularly inhibited by the limbic system. The thought of death is the one unifying and equalling experience of all humans, it allows one to be conscious of their morality. Psychic trauma, such as the thought of death, allows a production of a doctrine of the soul (Ernandes & Giammanco, 1998). Weakening the inhibitory action of the limbic system with psychic trauma causes the hierarchic behaviour of the R-Complex to rise to the Neocortical level; adding consciousness to the thought. Humans are the only animals that have acquired a consciousness that they are mortal, death is felt as a violence that they must suffer (Ernandes & Giammanco, 1998). Any psychic trauma allows for the R-Complex thoughts to be ascended to the Neocortex consciousness; following on the 'neural ladder' spoken of earlier (Loye, 2002). Trying to consciously understand death has created the concept of a Divine Being.

Ask yourself this Given the GSHM Model, how would a Divine Being or religion be continued after a frontal lobotomy, such that the limbic system is severed?

Limitations

Every theory has its limitations, that’s why it’s a theory! As such, Maclean’s Triune Brain theory doesn’t quite please everyone, especially as modern research and experiments explore more extensively into the brain. Reinert (1990) criticises Maclean's Triune Brain theory by stating that it is too loose to be considered a hypothesis with falsifiable predictions that could be derived from it. Furthermore, as our knowledge and research surrounding the brain increases, the developmental process presented by Maclean is inconsistent.

The limbic system did not appear first in early mammals, nor did the neocortex appear first in modern mammals, instead in primitive mammals (Reinert, 1990). This discredits the idea that the neocortex was the last to develop, allowing us conscious thought. If early mammals did not possess the limbic system, then the R-Complex would have no regulator; innate sexual behaviours would be uncontrolled yet with the consciousness of a neocortex (Ernandes & Giammanco, 1998; Reinert, 1990). All in all, the developmental process doesn’t make sense.

Conclusion

Maclean’s theory of the Triune Brain might be nothing more than a theory, but it provides a perspective that created opportunities and avenues for further research. Although modern research may discredit the reptilian influence on current humans, the findings and ideas presented contributes to the underlying structure of understanding behaviour and emotion; much like the limbic system.

See also

• Triune brain (Wikipedia)
• Emotion (Wikipedia)
• Autonomic nervous system and emotion (Book chapter, 2018)
• Biological factors in emotional reactivity (Book chapter, 2017)
• Limbic system and emotion (Book chapter, 2020)

References

Bath, H. (2005). Our Amazing Brains, Reclaiming Children and Youth, 14(3), 146 - 147.

Ernandes, M., Giammanco, S. (1998). MacLean’s Triune Brain and the Origin of the “Immense Power Being” Idea, Mankind Quarterly, 39(2), 173 - 201. http://doi.org/10.46469/mq.1998.39.2.3

Loye, D. (2002). The Moral Brain, Brain and Mind, 3(1), 133 - 150. https://doi.org/10.1023/A:1016561925565

MacLean, P. D. (1977). The Triune Brain in conflict, Psychotherapy and Psychosomatics, 28(1), 207 - 220.

Pearce, J. (2008). Paul MacLean, 94, Neuroscientist Who Devised ‘Triune Brain’ Theory, Dies, The New York Times. https://www.nytimes.com/

Peredery, O., Persinger, M. A., Blomme, C., Parker, G. (1992). Absence of maternal behavior in rats with lithium/pilocarpine seizure-induced brain damage: Support of MacLean's triune brain theory, Physiology & Behaviour, 52(4), 665 – 671. https://doi.org/10.1016/0031-9384(92)90395-I.

Reinert, A. (1990). An explanation of behaviour [Review of the book Triune Brain in Evolution. Role in Paleocerebral Function, by P. D. MacLean]. Science, 250(4978), p 303-305. https://doi.org/10.1126/science.250.4978.303-a

Smith, C. U. M. (2010). The Triune Brain in Antiquity: Plate, Aristotle, Erasistratus. Journal of the History of Neuroscience, 19(1), 1 – 14. https://doi.org/10.1080/09647040802601605

External links

• The Triune Brain (Therapy in a Nutshell, YouTube)
• What Really Happened to Phineas Gage? (SciShow Psych, YouTube)