-Why does the limbic system theory still persist?
While the concept of the “triune brain” is, as a whole, wrong, MacLean in 1970 did propose some interesting ideas about the evolution of the brain. He proposed that there are three main layers of evolutionary progress in the human brain. It starts in the middle with the most basic, the reptilian brain. The reptilian brain is the brainstem itself, and is responsible for the most basic of survival behaviors. The next layer out is what he called the paleomammilian brain, which is where MacLean says we find the limbic system. This part of the brain deals with social and emotions, and MacLean argues that most mammals have this. The third and most complex layer is the neomammilian or neocortex that deals with the highest of cognitive functions. LeDoux argues that while MacLean was fundamentally wrong about the physical layers of the brain, he was not far from the truth about the evolutionary brain. Emotions at the core are in part for survival, and so therefore the more complex the emotion, the more complex the functions needed.
-What remains relevant in limbic system theory?
Emotions are (in part) for survival, and the more complex the emotion, the more complex the system to process it must be (both in theory and in context). If an emotion or mood is as simple as fight or flight, then this is something that is instilled in reptiles, mammals, and humans alike. These emotions are more easily figured out in the human brain, and seem to be easier to experiment with as well as find out about. There has been a large amount of research on the amygdala and fight or flight response, which as was stated above, is a basic emotion that reptiles, mammals, and humans all seem to have alike. The more complex emotions that not all animals would have seem to be harder to research, harder to find the root of, and also seem to be the most complex emotions in terms of processing and regulating. While MacLean’s triune brain theory was mainly thought to be because of the size of animals’ brains, it is ultimately too simplistic of a theory to be correct.
-What is wrong with limbic system theory?
There are many things wrong with MacLean’s theory that have led most people to believing that there is no such thing as a limbic system, with some professionals even wanting the term to be banned altogether from textbooks and from the biological world. One of the main pieces of evidence against MacLean is that he was much too simplistic in his theories. MacLean believed that there was only one system for regulating emotions, while it is clear that it is much more complex than that. There has been very little evidence and findings to suggest that all of the parts of his limbic system work together, and over the years there has been so much disagreement on what structures should even be included in the limbic system.
Many of the various structures that MacLean originally proposed to be a part of the limbic system do in fact deal...