The Body/Brain Connection in the Conditioned Fear Response (Part 2)

Brain mechanisms involved in fear and fear conditioning

At the very heart of what LeDoux calls the fear pathway of the brain is a small organ near the midbrain called the amygdala (LeDoux, 1998). Anatomically, the amygdala can best be described as an almond-shaped nucleus in the anterior temporal lobe of the brain. It is believed to be involved in emotion, especially fear and anger. How information is transferred to the amygdala from the other structures in the limbic system is through nerve pathways.

Surrounding the amygdala, and leading to and from it, is an entire network of connections within a brain region that makes up the limbic system itself. As we have mentioned in previous articles, the limbic system is central in controlling mood and outlook. It is the part of the brain that determines our mind-set, and is involved in perception of events and motivation.

When we are in danger or are under attack, the limbic system is where fear and rage also occur. Fear energizes the body so we can run (flight), and the rage response is the signal that tells the body to prepare for defensive action (fight) in order to protect others or ourselves. It responds to extreme stress or perceived threat. Research shows that stressful environmental stimuli trigger cellular and hormonal responses that stimulate the adrenal cortex, which produces cortisol. It is cortisol in the blood stream that powerfully affects the body's reaction to stress. The ANS (autonomic nervous system) then goes into a state of heightened arousal that readies the body for fight or flight. Epinephrine (adrenaline) is released into the brain, respiration and heart rate quicken, the skin pales, and the body prepares for quick movement. When neither fight nor flight are perceived as possible, the limbic system commands the parasympathetic branch of the ANS to cause the body to freeze. Evidence would suggest that the interactions between the amygdala and the body's motor systems are an important part of the transition from affective (emotional) reaction to action, but the freeze response can be just as vital a part of survival for many a species as fight and flight when the environment demands such a response.

In the situation of the conditioned fear response, the trauma survivors continue to react to certain cues, even after the dangers no longer

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