The Reptilian Brain of Survival
The base of the brain contains the cerebellum, and it directly connects to the spinal cord (or brainstem). It is sometimes referred to as the reptilian complex, or the "lizard brain." You might be wondering, "What do I have in common with a lizard?" Well, all living creatures have basic functions that must be performed in order to sustain life. Those functions originate in this lowest, most primitive part of the brain such as: reflexive behaviors, muscle control, balance, breathing, heartbeat, feeding/digestion, and reproduction.
Trauma and the Mammalian Brain (the Limbic System)
Next is the limbic system, also called the paleomammalian complex; the mammalian brain; or the midbrain. This part of the brain is unique to mammals. According to MacLean (1990), the limbic system of this mammalian brain is the center of emotion and learning. It developed very early in mammalian evolution to regulate the motivations and emotions that we now associate with feeding, reproduction, and attachment behaviors. In MacLean's explanation, the limbic system evaluates everything as either agreeable (pleasure) or disagreeable (pain/distress). Survival is predicated on the avoidance of pain and the repetition of pleasure.
The limbic brain contains the amygdala and hypothalamus. This part of the brain does not register concepts of time, nor does it apply logic. As Dr. Earl Grey (2010), author of the very user-friendly guide Unify Your Mind: Connecting the Feelers, Thinkers, and Doers of Your Brain explains, the amygdala is a filter. Metaphorically, it is like a security checkpoint at the airport. The amygdala scans for any threat or danger. If the amygdala identifies the data as safe and non-threatening, it authorizes admittance to the neocortex. It is then integrated into other existing data acquired over the years. In essence, the information integrates into our existing experience without fallout. As we will discuss in the next chapter on treatment, early intervention soon after a threat or danger is signaled, facilitates this process of integration. Intervention can be as simple as validation of a traumatizing experience, and the comfort of social support.
So, what happens when the amygdala signals danger? Other parts of the brain become activated; specifically the thalamus which is also in the limbic brain. This activation can incite one of three alarm responses, driven by the lower reptilian brain: 1) the fight response, 2) the flight response, or the 3) freeze response. When these alarm responses are activated, the body will protectively and automatically respond according to the instructions of the brain. Even after the danger has passed, the thalamus remains on high alert, activating the same responses if anything reminiscent of the original danger passes through again. This makes perfect sense from a survival perspective. In the wild, predators often return with reinforcements!
The limbic/mammalian brain does not have any concept of time. Past, present, and future are all one and the same. This might explain why your dog (a mammal) may greet you as though you've been gone for 30 years, instead of 30 minutes. This phenomenon also helps to explain why traumatized people can seem stuck in the past. For them, something that happened 50 years ago feels as though it is happening right now. To the mammalian brain, where these crossed wires and balls of tangle are housed, 50 years ago is today. When we talk about traumatized people being "stuck," it's as though wires got all tangled up and stuck in the limbic brain. Getting stuck in the limbic brain is problematic because material was never meant to be stored here long-term.
A student of mine, herself a trauma survivor, once shared with me: "This part of the brain was designed to keep us safe from saber-toothed tigers … but it wasn't designed to keep us safe from saber-toothed tigers every day." When the protective capacities of the brain are overburdened, the brain's natural functions described in this section must work longer and harder than were ever intended to do for survival purposes. Because we were not designed to sustain this degree of heightened response, we develop the symptoms we associate with traumatic stress.
There is a fantastic clip from a CBS news story in which world-renowned psychiatrist Daniel Amen, MD is speaking with a survivor of complex trauma shortly after he completes a brain scan. The patient is young man who grew up in an alcoholic home; a veteran of the first Gulf War; and recent survivor of a severe accident. Dr. Amen explained to the young man, "Your brain's working too hard." That statement resonated with me because the simple and elegant explanation beautifully captures how the brain (particularly the limbic brain) is affected by unresolved trauma.