The Limbic System
According to Bessel Van Der Kolk, M.D. in The Body Keeps the Score, the limbic system is the seat of the emotions, the monitor of danger, the judge of what is pleasurable or scary, the arbiter of what is or is not important for survival purposes.
There are several components to the limbic system, but for our conversations, we are going to focus on two; the amygdala and the hippocampus.
The amygdala is known as the guard dog of the brain. It is constantly observing our surroundings and working to identify if we are encountering danger. When it does sense danger, it activates appropriate responses.
The hippocampus is where our memories are stored. I often think of that scene in Bruce Almighty where the file cabinet opens up and it shoots across the room as the hippocampus.
Part of the process in the amygdala determining if something is a threat is that it “converses” with the hippocampus to determine what our past experiences tell us. For example, if we hear a loud bang in the school hallway, we may jump for a second and feel fear, but when our amygdala checks in with the hippocampus, the hippocampus may determine that past experiences with that sound have been when a person slammed their locker, so our body starts to relax and reestablish equilibrium.
The hippocampus doesn’t always differentiate minute differences though. This is why you may jump when you are walking in your yard because you thought you saw a snake but it’s actually just a stick. Or when you pass somebody in the mall and you’re convinced you know them but upon confrontation, they aren’t who you thought they were. While the hippocampus may be similar to that file cabinet in Bruce Almighty the file cabinet space isn’t limitless so it does need to do some consolidation which causes similar things to end up getting grouped together.
The hippocampus also does not bring back memories with a “timestamp.” Meaning, if we step into your childhood home your hippocampus may bring forth memories of your mom baking fresh cookies. As the memory comes forth, you may feel as though you can actually smell the cookies and feel the excitement that you felt back then. That’s because the hippocampus doesn’t say “hey, this is a memory from your childhood.” It says “hey, this occurred in this place before so there’s a chance that it could be occurring now, too.”
This becomes particularly relevant when discussing PTSD. People with PTSD may experience intrusive flashbacks that appear to be unprompted. Based upon these various parts of the brain, though, what we can gather is that the person likely encountered something that the hippocampus labeled as the threat. Perhaps a person who looked similar to an abuser, passing a building that looks similar to a place a traumatic experience happened, hearing a sound that was similar to what occurred during a traumatic experience. And then the amygdala goes into action of activating survival responses so the person may start engaging in fight, flight, or freeze.
Which is why there is a huge push for mindfulness in mental health. Working to keep your mind focused and attuned to the present can help because while the present moment may have similarities to past traumatic experiences, the present is not the exact same experience. Being able to remain attuned to the present moment can eventually signal to the hippocampus that this is not the same experience and that this is a new, different experience.
Bessel Van Der Kolk labels the brain stem and the limbic system as the emotional brain. The components within these two parts are vital and necessary for survival, which is why most animals share these two parts with us. Next up, we will move up to the rational brain.
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