Let’s start with the mid brain. The midbrain is the emotional brain called the limbic system. It sits in the middle of the brain bordered by the other two parts of the brain. In the center of the limbic system, is the amygdala. This part of the brain is the emotional switching station of the brain. It receives emotional signals from the body and sends them to the other parts of the brain.
If the amygdala receives a signal that is a highly emotionally charged signal, it may light up the reptile brain. The reptile brain sits in the back of the brain. It’s referred to as the reptile brain because it dates back to the time when we were reptiles and needed to respond to the world as animals. It holds all our automatic functions related to danger. In times of danger, it automatically shuts down digestion and thinking in preparation to respond. It speeds up the heartbeat, speeds up breathing and readies the muscles to react. If there has been abuse in the past of a person’s life, it will interpret most highly charged issues as danger and will get the reptile brain on line and ready for action. So what does that mean? It means that if the brain thinks something threatening has happened the reptile brain gets the body ready for a huge reaction to what happened. When we were animals, we needed to quickly respond this way. After all, if there were a tiger stalking us, we would need to have this fast automatic preparation for defense. However, in the modern world we don’t have many tigers hiding behind bushes. In the modern word, there aren’t very many dangers, But our brains have only been human brains for about 5 minutes of the time that animals have been on this earth. Because of this, we have a tendency to have this automatic reaction to an emotional situation, not interpreting the situation as something that does not need us to go into such a defensive position.
This is where the third part of the brain comes in. The third part of the brain is the Prefrontal cortex. Humans have it and animals don’t. It’s in the front of the head just behind the forehead. It has many functions, but the function we’re talking about in this instance, is the executive function that happens in the mid left prefrontal lobe of the cortex. This is the part of the brain that sits back and says, “This is what is going on here and it is not dangerous and I do not need to respond to it with hypervigilance.” With that thought, the body calms down, stops preparing for danger and the left frontal lobe is able to make a sensible decision about a reasonable response.
All of us have a tendency to react at times with the reptile brain in control. We do this subconsciously, and it takes time to learn to use the left prefrontal lobe to make executive decisions about what is called for under the circumstances. That’s a lot of what therapy is about. In therapy we’re spending time learning how our past has created certain automatic reactions that don’t fit the current situation, and how to engage the executive function to change our reactions.