Trauma to the brain – The limbic system

Trauma that is so pervasive and severe can cause extensive damage to young people to the extent that it can literally change their physiology. These are often categorised as ‘Adverse Childhood experiences’.

Verbal abuse of young children can often result in intrinsic abuse that in turn releases harmful chemicals into the brain. This is turn can often result in a lack of growth in the part of their brain that tells good from bad, controls impulse control and a heck of a lot more; known as the Prefrontal Cortex.

For example if a child witnesses domestic violence or any act resulting in trauma, their brain goes into a high state of alert which cannot always be verbalised. This means that often they replay the trauma over and over again and actually feels the same physical effects.

Our bodies have a stress response system that governs our ‘fight or flight response’. If we are under threat our stress response system will often send messages to our adrenal gland (responsible for the production of adrenaline) which in turn releases stress hormones into the body. This effectively arms our body for combat – making our hearts beat quicker, airways open up and our pupils dilate. This happens to most of us when we are under threat and need to defend ourselves. And I’m sure you will agree that this is quite a handy defence system to have. Especially if we were under attack from another person. The issue for young people affected by trauma is that their bodies are constantly in this state of alert. And so a preventative and safety state actually becomes a problem.


The most significant neurological impact of trauma is seen in the hippocampus. PTSD patients show a considerable reduction in the volume of the hippocampus. This region of the brain is responsible for memory functions. It helps an individual to record new memories and retrieve them later in response to specific and relevant environmental stimuli. The hippocampus also helps us distinguish between past and present memories. PTSD patients with reduced hippocampal volumes lose the ability to discriminate between past and present experiences or interpret environmental contexts correctly. Their particular neural mechanisms trigger extreme stress responses when confronted with environmental situations that only remotely resemble something from their traumatic past.


Effect of trauma on the amygdala

Trauma appears to increase activity in the amygdala. This region of the brain helps us process emotions and is also linked to fear responses. PTSD patients exhibit hyperactivity in the amygdala in response to stimuli that are somehow connected to their traumatic experiences. They exhibit anxiety, panic, and extreme stress when they are shown photographs or presented with narratives of trauma victims whose experiences match theirs; or made to listen to sounds or words related to their traumatic encounters.

What is interesting is that the amygdala in PTSD patients may be so hyperactive that these people exhibit fear and stress responses even when they are confronted with stimuli not associated with their trauma, such as when they are simply shown photographs of people exhibiting fear.

The hippocampus, the ventromedial prefrontal cortex, and the amygdala complete the neural circuitry of stress. The hippocampus facilitates appropriate responses to environmental stimuli, so the amygdala does not go into stress mode. The ventromedial prefrontal cortex regulates emotional responses by controlling the functions of the amygdala. It is thus not surprising that when the hypoactive hippocampus and the functionally-challenged ventromedial prefrontal cortex stop pulling the chains, the amygdala gets into a tizzy.

Hyperactivity of the amygdala is positively related to the severity of PTSD symptoms. The aforementioned developments explain the tell-tale signs of PTSD—startle responses to the most harmless of stimuli and frequent flashbacks or intrusive recollections.