The Amygdala

The human brain contains many structures that seem specialized to a particular function. The occipital lobe, at the back of the brain, is specialized for processing visual information. Within the temporal lobe, the auditory cortext is specialized for processing sound. The frontal lobe coordinates the selection of appropriate behaviors. When your muscles move your body, they’re being directed by centers in your frontal lobes. The frontal lobes are a more recent evolutionary development, more rational or logical. They also function to inhibit the action of more primitive brain centers deeper within the brain.

Sometimes regarded as the fifth lobe, the limbic system is a more ancient brain structure widely believed to be responsible for the processing of emotion. Within the limbic system, the hippocampus encodes episodic memories—events that happen in your daily life. But in doing so, the hippocampus does not act alone. Instead, it needs help from an adjacent brain center, the amygdala, which is believed to attach emotional significance to memories. When subjects with damaged amygdalae are read stories with highly emotional content, they recall less of the story than normal subjects, suggesting that they no longer have the ability to attach emotional significance to events and use that significance as a cue for recall.

The amygdala is an interesting structure, because it’s clearly involved in the perception of threat. Anxiety is the product of evolution, simply because all organisms need some mechanism that senses and appraises threat. Given some threat to survival, the resources of the entire organism must be mobilized, and quickly, in order to flee or fight. This explains why anxiety can be aroused in milliseconds, why you feel anxiety simultaneously in your body and your mind, and why anxious symptoms so completely pervade your thoughts and emotions. Compare your threat response to organisms that were unable to sense or appraise threats. Whereas they were eaten, you inherited a fully featured threat detection and appraisal system. The amygdala is this system, designed by billions of years of evolution to initiate the flight or fight response, nearly instantaneously.

To function as the threat detection system, the amygdalae constantly monitor the environment for possible threats. The word “possible” is key, because the amygdala doesn’t necessarily wait for possible threats to develop into actual threats. That would be too dangerous. Think of it as your radar system, always on and operating in the background, closely tracking any number of blips, asking “What the hell is that out there?”, literally all day every day.

Like any detection system, the amygdala has the problem of detecting false positives. A false positive is detected as dangerous, when really it’s not. Imagine two cavemen emerge from their abode. Both see a field of yellow flowers waving in the breeze along with a flourish of orange in the distance, hard to make out. The first caveman says “Oh, such beautiful flowers, let’s go check out the pretty orange ones.” The second caveman’s amygdala goes into alarm mode, “Run, that’s a hungry lion!” How many times can you mistake a lion for pretty flowers and not be eaten? Probably never. If you’re wrong one time in a hundred you’re still lion food. Being wrong pays, because you’re right the one time when you really need it, when there’s really a hungry lion lurking out there.

The take-home lesson is: Your threat detection system is not aiming for accuracy. Those people were eaten. Instead, your threat detection is trying to keep you safe, and that involves detecting threats that are not really there and becoming alarmed for no reason. There’s no choice. The threat detection system housed in our amygdala is hypersensitive for good cause, because sometimes an orange flourish really is a lurking lion. That strategy was selected by evolution because it gets your genes and mine to the next generation. We live to reproduce.

That’s also why we have so much anxiety in our lives, so often, so senselessly. We imagine catastrophes (possible threats) and the alarm bells go crazy. The fact that the system is hypersensitive and not tuned for accuracy, that’s also why we have cognitive therapy. We have to turn down the sensitivity of the system by testing it against reality. We also have to accept the symptoms of the fight-or-flight response, rather than escape, in order to allow anxiety to extinguish.