Unlocking the Reptilian Brain: Understanding the Amygdala

(Editor’s note: This article is from the past issue of Brain World magazineIf you enjoyed this article, please support us with a print or digital subscription!)

It’s about the shape and size of an almond, nearly as old as the dinosaurs, to whose reptilian brains it bears a considerable resemblance. When you’re walking home late at night, it’s shouting out to you, bogging you down with panic as you navigate your way in the dark, ready to jump at every corner at whatever or whoever might be hiding there. It’s there again when you’ve had it with your significant other and the wet towels they’ve left carelessly on the floor, or when you need that company report but your computer crashes the night before. Unfortunately, your twin amygdalae, found deep inside your brain’s temporal lobe, are here to stay, and you’ll need to find a way to manage each time you find yourself ready to have a meltdown — however big or small it may be. The good news is that the amygdalae make up more than just your “reptilian brain” — in fact, that phrase hardly even needs to be taken as an insult.

First evolving some 200 million years ago, we share this set of organs with all of our mammalian ancestors as well as all modern day reptiles. Primarily, it is meant to regulate our primitive fight or flight response, as we size up threats like what we might see in that dark alleyway, or whether we can take on the big lead for sales next month. A key part of the limbic system, it was once believed to play an important role in mating rituals and displays of dominance, when animals stood guard over their territory. Sexual dimorphism supports this theory, with males and females showing the greatest disparity in size of the amygdala.

In fact, it is this region of the brain that may play a role in the development of autism or posttraumatic stress disorder, disorders where the brain is locked in a defensive coping mechanism against antagonistic forces. A study conducted last summer at Stanford University with MRI scans showed that children exhibiting higher levels of stress and anxiety had an amygdala “fear center” of significantly larger volume in their brains when compared to their peers, all of which showed patterns of stronger connectivity to the rest of the brain than normal.

You may be wondering why it has any social relevance today — and this hardly seems like a list of acceptable reasons. Perhaps it’s even enough to make you wonder if one day we’ll be born without one, or whether we’d be better off getting rid of it entirely — and maybe finding a way to stop all wars along the way. Alas, it’s more complicated than you might think. Being a central structure of the limbic system, it actually plays a significant role in learning and the development of memory. Not only do these bundles of neurons among the brain’s lateral nuclei remember our darkest fears — they could probably replay the events that triggered them in the first place.

However, the amygdalae are far from restricted to only negative thoughts and memories. The amygdala is often seen as being synonymous with processing fear — but it is really about processing the significance of events in relation to what the individual cares about at any particular given moment, through a biological lens. You probably have a memory of walking across a fresh cut lawn on a warm spring day and wanting to grow flowers one day like the ones that surrounded you in bloom. In fact, emotional connection can be an invaluable drive for learning, enough to lead its own burgeoning field of emotion-based learning. We all think intuitively, but it’s rarely something you wonder much about — and neither has the scientific world, until only fairly recently.

You might have an impulse to not show up to that job interview, or to not buy that car, but you probably could never explain why. In either of these cases, your amygdala is already processing the decision without your input. For these reasons, psychiatrist Antoine Bechara developed the Iowa Gambling Task — an assessment where you pick cards from one of three decks — some including rewards and others punishments. Bechara’s catch, however? Some of the decks reward higher than the others. The result is that the subject who undergoes the assessment gradually develops hunches as to how the decks are stacked — and the results are rarely what you would expect. Those who score the highest on IQ tests don’t always pass the task with flying colors. Researchers suspect it is because these people do the opposite of acting upon their intuition — they have a feel for the right cards, but go out of their way to stave it off and try to come up with a system that works, based on perhaps a method of trial and error. Meanwhile, they’re being bombarded with unconscious messages from their amygdalae to act another way.

In emotional-based learning, sensory stimuli, such as the feeling of the sun or the scent of fresh air, make contact with the basolateral complexes of the amygdalae, touching at the nuclei in between, forging our experiences. We take in new information by determining its relationship to previous experiences, and ones you will encounter in the future — your experience keeps you from having to consciously rethink the same decision processes. These memories become imprinted in the brain’s synapses, almost like a series of photo negatives. While many of our memories may deteriorate due to dementia, what is perhaps most intriguing about the amygdala is that these synapses stay intact despite whatever other damage the brain may undergo, making it very different from our other cognitive abilities, such as maintaining focus to read a book, something that may gradually dwindle with age.

You may have been in a car accident and while you remember things like headlights spinning toward you, you have trouble explaining how the damage happened in the first place. Everything just happened so fast, you might say. It’s because we don’t have a full memory of the incident when we first experience it. It takes a matter of time to add to the memories we create from these learning experiences, into a storage unit of long-term memory that is oftentimes infinite in its scope, and sometimes, leads to us not remembering everything with full accuracy. Something said around us can eventually find its way into a visual image of what happened.

So while there is the basic learning acquired through doing — taking notes, reading books, practicing a foreign language, it seems that we may have another option — controlling emotion-based learning by controlling the amygdala. What would happen if we could actually use the amygdala to learn calculus or recognize musical notes? Could it be a possibility that really isn’t that far away? A study conducted by neurobiologist James McGaugh has already explored the possibility, and the results seem to suggest that we may indeed not be too far off from tapping a whole new region of the brain for learning in the near future. Using a cortisol injection, a hormone that the brain gives off in response to stress, McGaugh activated the amygdalae of several mice shortly after they ran a maze. Two days later, those given the injections retained more knowledge of the task — a phenomenon that has also been consistent with human subjects.

For much of the last 300 or 400 years, particularly after the introduction of the scientific method into everyday life, humans have placed a significant emphasis on rational thought — valuing what we learn systematically and through reasoning, rather than trusting anything that may enter our heads intuitively without evidence. Contemporary findings, however, seem to be suggesting that our intuition may not necessarily always be wrong. Our hominid ancestors who didn’t have methodical approaches had to rely on this sort of thinking for centuries, but maybe we’ll be the ones to realize the powers our own intuition may hold.

(Editor’s note: This article is from the past issue of Brain World magazineIf you enjoyed this article, please support us with a print or digital subscription!)

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