The three main parts of the brain
So, to begin to understand trauma and the brain, first we need to get a bit more understanding about the brain itself.
Much like how the nervous system ladder has three main zones — so does our brain. We actually have what’s known as a triune brain, which is made up of three parts which developed in layers over the course of evolution. In fact, the three main parts of our brain developed in the same evolutionary order as each of the three zones of the nervous system.
The oldest part of our brain is the brainstem — sometimes called our reptilian brain. If we connect this to the oldest zone of our nervous system — the red zone — this is the part of the brain that is responsible for our most basic survival. It controls our breathing, our heartbeat, our digestion, our reproductive drives, and our primitive reflexes that help us survive in the first year of life.
The next part of our brain that evolved is the limbic system — sometimes called our mammalian brain. If we connect this to the second oldest zone of our nervous system — the yellow zone — this is the part of the brain that is responsible for monitoring and responding to danger. The limbic system judges what is important or not important for our survival, and controls our emotional and sensory experiences. We’ll touch more on this in a sec.
The most recent part of our brain to evolve is the cortex — sometimes called our “thinking brain”. If we connect this to the newest zone of our nervous system — the green zone — this is the part of our brain that is responsible for our ability to stay regulated. The cortex controls our conscious thoughts, our sense of time and context, our ability to problem solve, and allows us to think rationally with logic and self-awareness.
Our emotional brain
When combined together, the two older parts of our brain — the brainstem and the limbic system — is what neuroscientists often call the emotional brain, or our ‘survival’ brain. Our emotional brain is closely connected to our autonomic nervous system, which, as we know, is always scanning for signs of safety or danger. It does this through a small alarm centre in the brain known as the amygdala, which assesses for threats and puts our nervous system into a danger response before our thinking brain can even keep up.
Emotions as programs in the brain
But why then are these two main parts of the brain that are focussed on danger and survival, known as the emotional brain?
This is because our core emotions — sadness, fear, anger, disgust, joy, and excitement — are survival emotions. Emotions are actually physiologically wired-in programs in our brains that are designed to help us survive in a moment-to-moment basis.
What this means is that as our nervous system scans our environment, our emotional brain is constantly assigning meaning to situations — labelling them as either “good” or “bad”, and then will use an emotion to let us know what it decided — it will alert us to a danger, or alter us to an opportunity. The way emotions alert us is by creating physical sensations in the body, as well as physical impulses that prepare our bodies to take certain actions.
Think of when you take a swig of milk that’s off in the fridge — within a millisecond your emotional brain labels this situation as “bad” and will use an emotion, disgust, to make you feel uncomfortable sensations in the body such as nausea as well as the impulse to recoil and spit the milk out.
Because these programs are hardwired into the survival part of the brain, core emotions are involuntary and happen automatically below our conscious awareness, just like the responses in our nervous system. This is why it can be so hard to just “think” your way out of a feeling — our emotions were designed to be used as immediate signals that notify us of what’s happening around us and how we should react.
Why the brain experiences trauma
So where does trauma come into this?
If we look at an “optimal” adult human brain — someone who is predominately in the green zone, has a wide window of tolerance, and doesn’t regularly experience traumatic stress — while their emotional brain is always running in the background like it should, they also have constant access to their thinking brain, particularly their prefrontal cortex.
drawing = adult brain cortex online
When we have access to our prefrontal cortex, even if the amygdala or that emotional brain sends a signal, our thinking brain is able to pause and calmly observe what is going on before reacting, to see if a stress response is actually warranted in this particular moment. The prefrontal cortex is what we use to regulate our emotions and impulses, and in an “optimal brain” we are able to keep a balance between these two parts of the brain — we’re able to fully notice and experience these core human emotions and stay regulated.
Now if we think about the big T and small t traumas that we talked about in the last lesson — I mentioned that infants and children are particularly susceptible. This is because our cortex isn’t fully developed when we’re born. Children actually don’t begin to have full access to things like their prefrontal cortex until the age of seven, and even then it still needs to continue to develop and mature well into our late teens and even our twenties.
What this means is that as children, we don’t really have access to the self-regulating parts of our brains. When our nervous systems detect danger, whether real or perceived, the automatic programs of our survival emotions are in charge, and we don’t have the rational parts of our thinking brain to help us assess the situation, tolerate the emotions, and find ways to cope or calm back down.
This is why we rely so heavily as infants on our caregivers to help soothe us. We don’t yet have the capacity for self-regulation, and so we need a caregiver there to co-regulate with us. We’ll talk more about co-regulation in the ‘Connect’ part of the course.
But for now, what’s important to know is that when we’re feeling a danger response, if our cries for help or attempts at taking action don’t work, and we don’t have the help of a caregiver to help us make sense of our experience or let us know that we’re safe, our brains and bodies can become overwhelmed beyond our capacity to cope. This is because our amygdala hasn’t received a signal to turn off the alarm, and we don’t yet have access to our own prefrontal cortex to control our emotions or impulses, so instead we get “flooded” with strong emotions and physical sensations that were originally just meant to be a temporary alert to a possible danger, but instead now feel intolerable in and of themselves and just add to our distress. That’s when stress becomes traumatic.
Learning to find balance
This is why a lot of the tools and techniques I teach in the ‘Cope’ part of the course are centred around learning to gently notice our experience and find ways to slowly increase our tolerance with awareness and compassion, because these are fundamental ways that we can find some connection again between the prefrontal cortex and the amygdala, so that the amygdala isn’t stuck having to run the show on its own.
What I’ve covered in this lesson are the building blocks to understanding trauma and the brain. There are so many more facets to the brain that are involved in this experience, far too many for me to cover without completely overloading you, but in the next few lessons we’re gonna go a little further into how the brain is affected by traumatic stress and how this can affect people in their present-day lives.