Changes in the Hippocampus
The hippocampus is the area of the brain that regulates happiness, joy, hunger, and it also regulates memories. Without the hippocampus, the brain would be unable to distinguish time frames for memories, as it aids in differentiating what memories took place in the past and what is happening in the present.
When PTSD occurs, the stress that takes place alters the hippocampus by killing cells, causing it to become less effective. In this weakened state, the hippocampus has trouble identifying what memories occurred in the past and which memories occur in the present. Because of this, flashbacks and memories that flood the brain cause the patient to believe that they are reliving their traumatic event.
Effects on the Amygdala
The amygdala is a part of the brain that processes emotions as well as registering fear and stress. It has a close relationship with the hippocampus because the hippocampus controls responses to the environment. Since the hippocampus experiences much more stress than usual, the amygdala also experiences much more stress and fear. Now that both the hippocampus and amygdala are stressed, a patient with PTSD is drastically more susceptible to triggers, stress, and fear. The amygdala repeatedly processes the stress registered by the hippocampus, causing it to be on much higher alert.
The overactive amygdala is what causes patients with PTSD to constantly see threats and danger in their environments. In addition to stress and fear, the amygdala controls survival in what the brain registers as life-threatening situations. Again, the hyperactive amygdala begins to register many situations as life-threatening, causing paranoia, fear, and an abundant amount of stress.
Impact on the Sympathetic Nervous System
Similar to the amygdala, the sympathetic nervous system is also responsible for registering stress, danger, and fear. Post-traumatic stress disorder causes for the sympathetic nervous system to be much more active than normal, as it registers many environments as dangerous, just as the amygdala is. The difference is that the sympathetic nervous system being so hyperactive causes a dramatic increase in adrenaline, as the brain is constantly registering that the individual is in a dangerous situation. The repetitive adrenaline alters the body’s ability to regulate. This is what causes the common symptom of fatigue and exhaustion. The body and brain aren’t used to being so high strung, and it becomes extremely draining very quickly.
Changes in the Ventromedial Prefrontal Cortex
The ventromedial prefrontal cortex is responsible for processing negative emotions, including fear, anxiety, and stress. It works extremely close to the amygdala and the hippocampus. The amygdala triggers emotions that it receives from the hippocampus, then the ventromedial prefrontal cortex regulates and chooses responses for these emotions. Since the brain believes that it is constantly encountering stressful and dangerous environments, the ventromedial prefrontal cortex is repeatedly experiencing and exhibiting anxiety and fear.
It very much is like a chain reaction. First, stress from the traumatic event taking place kills cells within the hippocampus. The hippocampus then has difficulty differentiating memories between the past and present, causing much more stress than is typically present in the brain. From there, the amygdala registers from the hippocampus that the traumatic event or other stressful situations are constantly taking place, making it extremely high strung. Triggers begin to take place that causes the amygdala to register stress at a much higher rate. The hyperactive amygdala processes things that may or may not have anything to do with the traumatic event and notifies the ventromedial prefrontal cortex of the supposed negative situation. The ventromedial prefrontal cortex receives this information and registers the environment as it had been passed on from the hippocampus and the amygdala, eliciting feelings of fear and anxiety.