Panic Attacks, the Amygdala, and the Limbic System: A Paradox of Protection

The amygdala, situated equally in both brain hemispheres, is an almond-shaped (“amygdala” is derived from the Greek for “almond-like”) grouping of nuclei approximately one-inch long, located just a few inches from each ear, inward and in a direction toward the forehead. It’s considered to be the most primitive component of the brain’s basal ganglia; a grouping of nuclei deep within the brain associated with movement, motivation, emotion, reward, and addiction.

The amygdala moves into vigorous motion in response to threatening sensory input, real or perceived. And don’t ever forget those last three words. Indeed, as the amygdala is stimulated electronically in the laboratory animals respond with aggression. Taking it to the extreme, if the amygdala is removed an animal’s rage response to agitating stimuli falls by the wayside. Fear and sexual responses go out the door as well. And how ‘bout this factoid? The amygdala has the most structural variance between the genders of any brain structure. And, oh by the way, the amygdala shrinks by some 30% when a male animal is castrated. Ouch.

The amygdala is a card-carrying member of the brain’s limbic system. The word “limbic” is derived from the Latin, “limbis,” meaning a border, edge, or fringe of an object. The term “limbic system” was coined by 19th Century French anatomist, Dr. Paul Broca, who used the term in reference to the tissue he found surrounding the brain stem and beneath a piece of brain anatomy known as the neocortal mantle. The limbic system is all about the memory and motivation components of emotion; and its star players, for our immediate purposes, are, indeed, the amygdala, the hippocampus, and the hypothalamus.

It’s fascinating that the limbic system impacts memory formation by merging assorted present emotional states with stored memories of previous experiences. As it swings into action the limbic system influences our endocrine system (hormone secreting ductless glands) and, of particular note, the autonomic nervous system (ANS); composed of two parts, the sympathetic nervous system and the parasympathetic nervous system. It also impacts the prefrontal cortex, the executive functioning/decision-making portion of the brain.

Let’s finish our journey through the limbic system by taking a look at the hippocampus; a crescent-shaped bit of anatomy that in cross-section resembles a seahorse, and curves in an upward direction toward the back of the brain from the amygdala. The word, “hippocampus,” coined by 16th century anatomist Julius Caesar Aranzi, is derived from the Greek, “hippos,” meaning horse, and “kampi,” meaning curve. The hippocampus is assigned the task of forming event-induced memories, converting them to long-term memories. Don’t ever downplay the role of the hippocampus as it relates to memory and emotional reaction because remembering threatening events, people, etc. gives us a huge leg-up on responding to future threats from the same or similar sources. Indeed, that’s memory’s foundational purpose.

Though the amygdala and our fear circuitry remain mega-mysterious, it’s commonly accepted that what we perceive as fear is produced by a very sophisticated two-way input system. And here’s how it works. Sensory input passes through a gateway in the brain, a messenger hub if you will, called the thalamus. It sits right above the amygdala in the center of the brain. The main function of the thalamus is to transmit its received sensory data to the higher-centers of the brain for reasoned response. The primary recipients of these messages are the thought and logic centers of the cerebral cortex. However, as you’re about to learn, the thalamus has other communication partners.

When environmental input from our senses of sight, sound, taste, and touch reaches the thalamus, and very specific cues are analyzed, there looms a fork in the road. One bit of pavement leads directly to the amygdala, while the other takes its sweet time and heads toward the cerebral cortex. And each of these destinations generates very different and very unique responses. You may have noticed I left out our sense of smell from the first sentence of the paragraph. That’s because input from our sense of smell forgoes all the thalamus formality and shoots straight into the amygdala, though the amygdala doesn’t facilitate perception.

Now, when the amygdala receives a message it’s engineered to react by launching an intense physical response generated by activation of the HPA axis, which, as we know, leads to the secretion of cortisol and norepinephrine. So this is the actual physical manifestation of fear that panic sufferers know all to well. See, the amygdala doesn’t care if it’s right or wrong, justified or not; it receives input and fires. By the way, the amygdala also sends messages to the brainstem to facilitate required adjustments in heart rate and respiration in response to fear and stress.

Well, after the initial onslaught of environmental boom hits home the slower sensory messages from the thalamus finally hit the cerebral cortex; specifically the prefrontal cortex, the area at the very front of the brain responsible for executive functioning - the mental ability to receive and interpret information and formulate decisions. As this occurs, conscious and rational thought regarding the events at hand is generated. Yes, it’s in the prefrontal cortex that the fear stimuli are logically analyzed in great detail, the final assessment being sent to the amygdala. The prefrontal cortex must remain on high-alert and do its best to ensure assessment accuracy because of its communication with the areas of the brain associated with pain, pleasure, anger, aggression, and panic. Indeed, there’s a lot at stake. And when it’s all said and done the amygdala ultimately takes its version of appropriate action, which if sufficiently convinced can include restoration of calm.

Think about what a miraculous system this is. I mean, the amygdala, the entire limbic system for that matter, has its fear message and is prepping the body for immediate action. It’s taking no chances as it elects to err on the side of caution. And as you consider these dynamics, always keep in mind that evolution brought us a genetic make-up that leans toward the anxious. Well, after the amygdala sends its message the prefrontal cortex takes the time to calculate the exact nature of the threat. If sufficient evidence exists that there is no threat, the amygdala is told to chill-out.

Again, what an incredible mechanism this truly is; however, as it applies to panic there’s a major drawback. In the face of fear, the amygdala is the dominant of the two structures. And once the amygdala starts beating the drums it’s really tough for the prefrontal cortex to convince it to knock it off. And without practiced intervention it really doesn’t stand much of a chance. That‘s what paves the way for misinterpretation of sensory input, leading to overreaction to truly harmless stimuli.

And that’s at the very foundation of panic.