Triune brain: three brains, one person

The triune or triune brain is a concept developed by neuroscientist Paul MacLean to refer to the three specialized parts or brains in human beings. These parts develop at different times in the evolutionary cycle, which is why they are said to be created from the bottom up. That is, the oldest and most primitive part of the brain develops in the womb, while the emotional brain is organized in the first 6 years of life and the prefrontal cortex develops last.

Advanced physics and technology have made neuroscience one of the most popular fields of research and have led to a better understanding of how our triune brain works. The differences and characteristics of each of the parts are described below.

The reptilian brain

This part is known as the ancient animal brain. It is located in the brain stem, just above the place where the spinal cord enters the skull. It is the most primitive part of the human being and begins to develop in the womb, so It influences everything newborns can do (breathe, eat, sleep, wake up, cry, urinate, etc.).

The brain stem, along with the hypothalamus, controls the body’s energy levels and automatic processes, something known as homeostasis, a term that refers to the maintenance of internal balance. The functions controlled by the reptilian brain are fundamental, although its importance is forgotten or somewhat relegated if we start to think about the most advanced functions of our mind, such as abstract thinking.

Many psychological problems are related to difficulties in these basic functions. that maintains the reptilian brain. For example, in any trauma treatment this must be taken into account or, if not, the entire organism will be thrown into imbalance.

The emotional brain

The emotional brain or limbic area is located just above the reptilian brain, in the center of the Central Nervous System (CNS) and begins to develop from the moment the baby is born. Depending on the experience, genetic composition and innate temperament of the infant, this emotional brain or limbic system is formed.

Some authors call the group formed by the reptilian brain and the limbic system the emotional brain. It is the center of emotions, the monitor of danger, the judge of well-being or the arbiter of survival.

Intense emotions activate the limbic system, specifically the amygdala area.. The amygdala is responsible for warning us of dangers (fear center) and launching different responses:

Triggers the cascade of stress hormones. Triggers nervous impulses. Elevates heart rate. Increases oxygen consumption. Prepares the body to fight or escape.

Gray demonstrated in his animal studies that, The lower the level of serotonin, the greater the hyperactivity to stressful stimuli and vice versa. For example, in male monkeys it was observed how dominance hierarchy position influenced serotonin levels.

Some people who have faced a traumatic situation register the threat, but their conscious mind continues as if nothing had happened. Although the mind can learn to ignore messages from the emotional brain, The body’s alarm signals do not stop, and the emotional brain continues to function.

The two parts of the triune brain (reptilian and emotional), evolutionarily older, are responsible for recording experiences, managing our physiology and identifying internal states and emotions. Some examples are comfort, security, threat, hunger, fatigue, desire, desire, activation, pleasure or pain.

The rational brain

The youngest part of our triune brain is the rational brain, also known as the neocortex. Here is the prefrontal cortex, which is responsible for planning, anticipation, perception of time and context, inhibition of inappropriate actions, empathic understanding, etc.

Many times, The rational brain cannot free the emotional brain simply through knowing and understanding what has happened to it., for example, in a trauma. For many people it is easier to tell what has been done to them than to realize, feel and put words to the reality of their internal experience.

The frontal lobes are part of the rational brain and balance the boundary between impulses and acceptable behavior in a given situation. The proper functioning of the frontal lobes is crucial for the following functions:

Maintain harmonious relationships with human beings.Prevent us from doing things that will put us in a bind or that may harm others, that is, behavioral inhibition.Regulate our impulses: hunger, sex, anger…

Actually, The rational brain occupies only 30% of the cranial space, and is basically concerned with the outside world.. Its main functions are understanding operations, meeting objectives, managing time, sequencing actions… Compared to the emotional brain, the cellular and biochemical organization of the neocortex of the rational brain is more complex.

Applications of this theory

This theory was dominant for years after its release, although it was later refuted. However, it leaves some applicable and useful lessons:

It opened the doors to new theories about the evolution of the brain. Each aspect of the mind can be developed, since it has a neurological correlate that makes it real and modifiable. Emotions do matter, as they play a fundamental role in the survival of the individual, its development and its relationship with others. The brain learns in a comprehensive way. According to this theory, all parts of the triune brain work together, developing with each new learning.

Criticisms of the triune brain theory

According to MacLean’s presentation of this theory, it seems that the brain has been built floor by floor throughout evolution, with independent functions linked directly to the neurological structures of each layer. However, this conception has received numerous criticisms.

Nature has more than one way to build the brain. Birds, for example, harbor the same intelligence as some mammals, such as primates, in much smaller brains.. They show complex cognitive processes, such as self-awareness or a sense of justice, with a neocortex supposedly less developed than the human one.

Furthermore, the cerebral cortex was not the last to appear in the history of evolution. The first signs of gray matter in the superficial layer of the brain have been found in primitive mammals, known as the paleocortex.

The set of criticisms demonstrates that brain structures did not emerge in an ascending manner, but rather that all functional areas existed from the beginning and were developed selectively depending on the needs of each species.

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