Understanding the brain and stress response
The brain has three main parts:
o the brain stem is the `oldest’ part. It developed first. The brain stem controls arousal and automatic responses e.g. `survival’
o the limbic region evolved next. It includes the amygdala or ‘the brain’s smoke detector’ and the hippocampus. It evolved next. It connects the high and low parts of the brain. It is responsible for the experience and expression of emotion, and for memory.
o the cortex developed last. It allows a person to reflect i.e. it is the area for cognition and thinking. The pre-frontal cortex is part of the cortex involved with concentration and higher brain functions.
It is important for these three brain areas to work together. It is also important for the right brain and the left brain to work together. Any real or percevied threat is registered in the primitive parts of the brain. These are closely connected to the brainsteam. A threat of danger sets off the amygdala. This triggers the fear-based survival response of fight/flight/freeze.
The hippocampus processes information about the threat (Cozolino, 2006). Supported by the amygdala, it helps store the memory of where and when significant events occurred. The hippocampus helps process information. It also adds time and spatial context to memories and events, and consolidates and codes memory.
We can only consciously assess and process a threat after our fight/flight/freeze response has been triggered. The pre-frontal cortex helps us do this. It helps us manage our feelings, control out impulses, and plan how we will respond. The pre-frontal cortex can 'switch off' the fight/flight/freeze response (Wilson et al., 2011) after we assess there is no danger. The hippocampus also helps us make decisions. It helps us understand cause and effect, complete tasks and solve problems.
How does childhood trauma impact on brain development?
Our childhood brains develop from the 'bottom up’ i.e. the brain stem first. The survival functions develop before those for planning and impulse control. Our brainstem works fully when we are born. It controls basic survival functions such as heart rate, breathing, sleep and hunger.
We are also born with a functioning 'threat detection' system. In fact the amygdala can register a fear response in the final month before we’re born (Cozolino, 2006). We can develop a 'memory' of fear before we have language (i.e. this is pre-verbal), or can understand where the fear comes from. These 'memories' are stored in our body as body memories and emotions.
The hippocampus develops in response to our world into adulthood (Cozolino, 2006). Before the hippocampus develops we can’t consolidate 'autobiographical' memories. The pre-frontal cortex only matures in our mid-twenties.
Some parts of the brain grow and develop rapidly at certain ages. Overwhelming stress in childhood affects the way the brain develops (Gunnar and Quevedo, 2007; Pechtel and Pizzagalli, 2011). During critical periods of development, trauma can badly affect different areas. Positive experiences can help development. Negative experiences impair development (Wilson et al., 2011).
What changes occur in the brain in childhood trauma? What are their effects?
Childhood trauma can affect different parts of the brain. This helps explain many of the challenges survivors experience.
• Reduced activity in Broca's area (this is the area for speech). This can make it difficult to talk about trauma and describe it with detail (Hull, 2002). This is additional to trauma which is pre-verbal.
• The hippocampus becomes smaller and its structure is interrupted (Wilson et al., 2011; McCrory et al, 2010). This can affect attention, learning and memory (Hedges and Woon, 2011; Pechtel and Pizzagalli, 2011).
• The corpus collosum which connects the left and right sides of the brain, is reduced. This prevents the two sides of the brain working in a coordinated way (Wilson et al., 2011)
• Changes to amygdala function (Wilson et al., 2011; Pechtel and Pizzagalli, 2011). This can make a person more likely to react to triggers, especially emotional ones. People can experience emotional extremes and struggle to regulate their emotions.
• Reduced activity in different parts of the cortex- frontal lobes (McCrory et al, 2012). This can mean a survival response/s is triggered in absence of danger (Ali, et al., 2011).
• Changes in 'reward pathways'. This can mean that survivors anticipate less pleasure from different activities, and may appear less motivated (Pechtel and Pizzagalli, 2011).
Understanding the brain and the impacts of childhood trauma
Children and adults who have experienced childhood trauma often react to minor triggers. That’s because trauma sensitises the amygdala to the perception of threat. This means that fear responses are triggered over time by less and less stress.
The pre-frontal cortex is needed for learning and problem solving. When the amygdala is activated, it goes off line. After threat we can assess a situation and establish that it is safe. This can be because we did fight or flee. Sometimes it’s because it wasn’t a threat at all. In trauma, the pre-frontal cortex is less able to switch off over time.
Extreme stress means there is more cortisol in our system (Murray-Closeet al., 2008). This can stop the hippocampus working. It also reduces its volume. This is associated with poorer declarative memory, depression and physical inflammations (Danese et al., 2006).
The prefrontal cortex and the `higher’ brain are very vulnerable to traumatic stress (Silberg, 2013). Trauma affects our ability to think. It makes us less able to learn (Courtois & Ford, 2009). This is because we are in survival mode. Under traumatic stress, the `lower’ brain stem responses predominate, and impair a person’s ability to be calm, learn, think, reflect and respond flexibly.
Trauma affects the coordination of nerve networks. In this way, adaptation to trauma, especially early in life, becomes a "state of mind, brain, and body" around which subsequent experience organises (Cozolino, 2002).