So far we have been focused on the physiological mechanisms and effects of an adrenaline surge, this post is going to take a look at how the brain deciphers the signals and activates the fight or flight response.
The entire fight or flight process is a complex one that takes place in our subconsciousness. For ease of explaining the process I will break it down into steps.
- Sensory information is taken in by the eyes, ears and body, and directed towards the brains Thalamus.
- Sitting atop of the nerve stem in the middle of our brain, the Thalamus is the brains nerve center. From here the sensory information is split and routed in two directions.
- One destination is the frontal cortex, located in the neocortex. This area of our brains is what separates us from the chimps, it is where all our higher mental functions take place.
- The second destination is the Amygdala, located just in front of the Thalamus, this is the brains threat evaluation center. As the sensory information flows into here it is evaluated for any signs of danger.
- Before a response can be initiated the Amygdala will project the information of the perceived threat to the neocortex. It is here that our higher mental capacity analyses the threat in greater detail and decides if there is threat or not. If the coast is clear it will tell the Amygdala to "stand down" and not initiate the reaction.
As well as threat perception the Amygdala is also where our brains learn emotional association. For example, being stung by a bee as a infant. Whilst consciously we may not remember the incident, the Amygdala will store the information that involved so that as an adult, the sound of a bee buzzing past your ear will illicit a fearful response.
With this system being kept in check by the neocortex it is understood that situational training can condition the mind to react to stress and fearful situations. A key skill for a soldier in combat where the difference between fight or flight can mean safety or mortal danger.
- LR Mujica-Parodi, HH Strey, B Frederick, R Savoy, D Cox, Y Botanov, D Tolkunov, D Rubin, J Weber: Chemosensory cues to conspecific emotional stress activate amygdala in humans. PLoS One 2009, 4:e6415.
- LeDoux, J. E. The Emotional Brain: the Mysterious
Underpinning of Emotional Life (Simon & Schuster, New