Our brain: three in one
Posted by Pilar
What have we got in common with a snake or a donkey (without thinking of anyone in particular)? Paul MacLean gave us the answer to this riddle with his theory of the “triune brain”, popularly known as “three in one”. According to this theory, the brain comprises three interconnected neural systems which are the product of different evolutionary processes. These systems are the reptilian, the limbic and the neocortex.
It appears that we’ve all got some connection to reptiles, whether we like it or not. Our affinity is located in the oldest area of the brain, which is found in the upper part of the spinal cord at the base of the neck. The reptilian system is focused on action. It doesn’t think or analyze, but leads to action when prompted by the body. It thus forms the basis for instinctive modes of behaviour, such as certain types of aggression, the sexual instinct or the defence of our own territory. Looked at in this light, perhaps warmongers are closer to snakes than philosophers.
The second cerebral system is the limbic or the paleomammalian system. In evolutionary terms, it is younger than the reptilian system. It is located behind the face and envelops the reptilian system. According to MacLean, we share this system with all other mammals, hence its name. From the point of view of fear, the most interesting aspect of the limbic area is that it controls our emotions. So happiness, anger, love and fear, amongst other emotions, are processed in the part of our brain which most closely resembles the brains of dogs, elephants or donkeys. The limbic system can therefore justly be considered the affective part of our brain. It follows, then, that love is not the exclusive prerogative of humans, although we are the only ones who write poetry about it. Any imbalance in the limbic system leads to negative emotional conditions such as depression, loss of memory and morbid states of fear, among others.
Finally we come to the neocortex system, which is the exclusive prerogative of homo sapiens. This system enables higher-level thinking processes, such as the solution of problems or critical and artistic faculties. This neocortex contains a series of nerve cells which facilitate the production of symbolic language, which gives rise to abilities such as reading, writing and arithmetic. This explains why poetry can only be written by humans, even though many of its underlying emotions are shared by all other mammals.
