Amygdala

What Is the Amygdala

The amygdala is an almond-shaped structure, one on each side, located deep within the medial temporal lobes, and it is in fact a complex made up of several distinct nuclei. Its primary role is the emotional evaluation of sensory information, particularly the detection of fear and threats. Before incoming information is analyzed in detail by the cerebral cortex, the amygdala makes a snap judgment based on rough data alone - "is this dangerous or not?" - and triggers the fight-or-flight response if necessary. The moment your body freezes when something moves in a dark alley is the result of the amygdala activating a defensive response without waiting for the cerebral cortex to finish its analysis.

Amygdala Hijack

Psychologist Daniel Goleman, in his 1995 book Emotional Intelligence, coined the term "amygdala hijack" to describe the phenomenon in which the amygdala bypasses rational judgment and triggers an emotional reaction. Saying something you shouldn't in a fit of anger, going blank with fear, overreacting to trivial things - these are all described as states in which the grip of the prefrontal cortex (the region involved in deliberation and restraint) briefly slips. The evidence most often cited for that head start comes from Joseph LeDoux's work on the rat auditory system: a signal travelling directly from the thalamus reaches the amygdala as early as about 12 milliseconds after a tone begins, while the signal routed through the auditory cortex takes at least about 20 milliseconds. That is not a measurement of the human prefrontal cortex against the amygdala, so it cannot license a claim that emotion is some number of times faster than reason. What it does show is that the brain is wired so that emotional appraisal can run ahead of detailed analysis.

Trauma and Amygdala Hypersensitivity

In people who have experienced trauma, the amygdala tends to react with heightened sensitivity. Even in currently safe situations, it continues to sound the alarm in response to stimuli that bear even a slight resemblance to past threats - a sound, a smell, a facial expression. This is thought to be one of the neurological underpinnings of flashbacks and hyperarousal. Recovery from trauma can be understood as the process by which the prefrontal cortex regains the ability to regulate the amygdala's hypersensitive responses. Mindfulness and body-oriented therapies are said to help because they work on this regulatory capacity.