“Reptilian brain” is a term often associated with that part of the nervous system that regulates the more primitive instincts and automatic reactions, such as fear, aggression or survival. It is a fascinating definition, theorized in the 1960s by the neurologist McLean, which recalls the image of a nucleus “ancestral” hidden within us, but it is also a simplification that does not reflect the complexity of the human brain. Although some vital functions are actually located in deep brain structures, the idea of a “reptilian autopilot” is now overcome by modern science. MacLean’s theory is good to understand in broad terms the concept of evolution applied to the brain, but in reality all our emotions and behaviors, even the most instinctive ones, are the result of intricate interactions between different brain areas.
The origin of the concept: the triune brain theory
The term “reptilian brain” is due to the neurologist Paul MacLeanwho in the 1960s proposed the theory of the triune brain (i.e. divided into three parts). According to this hypothesis, our brain evolved in three main layers:
- Reptilian brain: the oldest nucleus, responsible for vital functions (breathing, reflexes) and basic instincts, such as survival and reproduction.
- Limbic system: an evolutionarily subsequent structure, linked to emotions and to memory. It is not included in the “reptilian brain” because, although some homologous regions are present in reptiles, it is in mammals that the emotion areas become prominent in terms of volume and connections.
- Neocortex: the most recent part, which presides over the rational thinkingto language and to planninghas its maximum volumetric expansion in us, Homo sapiens
This theory has been appreciated for its simplicity and ability to explain brain evolution in an intuitive way. It is indeed a lot effective on a dissemination level. However, as neuroscience has advanced, it has emerged that the brain does not function as a hierarchical stratification: its structures they are highly integrated and interdependent.
The reptilian brain handles basic survival functions
Structures associated with the so-called reptilian brain include the brainstem hey basal ganglia. These areas, which we share with many animals, regulate automatic functions essential for life, such as breathing And heartbeat, survival reflexes (such as the fight or flight mechanism) and cmotor coordination basic, useful for simple and automatic movements.
As you might guess, they are basic functions for our survival, and that’s why I’m basically universal in the animal kingdom from reptiles onwards. Yet, they do not operate in isolation. Even behaviors apparently “primitive” are influenced by other areas of the brain, such as the limbic system (which manages emotions) and the neocortex (which analyzes and plans, acting with inhibitory or excitatory connections on limbic areas and, to a lesser extent, on deep areas).
The myth of the reptilian brain: the implications
The idea of the reptilian brain is often used in popular psychology and marketing to explain impulsive or impulsive reactions gut decisions. But this is actually a simplification that can distort the understanding of our behavior, reducing the complexity of emotions and decisions to mere primordial instincts. The theory then leads to suggesting an approach to mental disorders that seeks to identify dysfunctions in specific areas of the brain. For example, emotional disorders could be traced back to malfunctions of the limbic system.
On the contrary, today we know that our behaviors are the result of the functioning of network which expand into large portions of our brain, sometimes passing from deep structures to the neocortex and vice versa. In reality, as we have seen, our brain is the result of millions of years of evolutiona sophisticated system in which even the most basic functions are connected to higher processes.
Our brain is actually much more complex
The image of an “inner reptile” that takes control in dangerous situations is suggestive, but it does not reflect scientific reality. Modern neuroscience and the advancement of techniques for observing the functioning of the brain demonstrate that the theory of the triune brain is captivating, but not very precise. Here’s why:
- It is not an autonomous system: Even the most instinctive reactions involve other parts of the brain. In reality emotions and rationality they work togetherare activated simultaneously and regulate each other, and the brain areas that regulate them are not such clearly specialized circuits. For example, fear is processed byamygdalabut also from prefrontal cortexwhich evaluates and modulates the response.
- The evolution of the brain is integrated: the brain did not develop by “adding layers” like in a cake, but by modifying and reorganizing existing structures continuously. As well explained by the neurologist Georg Striedter in his book “Principles of Brain Evolution”, the evolution of the brain was not so clear and linearunlike McLean’s theory suggests.
- Behaviors complex: functions such as aggression are not only the result of primitive impulses, but also depend on experiences, culture and cognitive processes.
So, although thinking of the brain as a layered entity can be useful for explaining evolution, it does not reflect its true complexity. There is no separate “reptilian brain”.: Each function is part of an integrated system that combines instincts, emotions and reasoning to adapt to life’s challenges. So, the next time you hear about your “inner reptile”, remember that it is just a metaphor: your brain is much more complex, and its strength lies precisely in the collaboration between its parts.
