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There’s a model called the Three-Part Brain. The idea is that the brain developed in three evolutionary stages. This concept first came about in the 1960’s, and it’s a useful way of thinking about how the brain develops. The model is that the brainstem is the oldest part, at the bottom of the brain, and developed when the reptiles evolved. Then the limbic system, in the center of our heads, developed when mammals came into being. And the prefrontal cortex, the outer layer at the front of our brain, developed last with the primates and humans. We each have all three parts of the brain, as a testament to our evolutionary past.

But not only did the three parts of the brain evolve bottom up across millions of years, they develop in us as individuals in the same order. The brainstem develops first, then the limbic system, then the prefrontal cortex, mimicking our ancestral history.

Reptilian Brain: The Brainstem

The brainstem, the part of the brain we have in common with the reptiles, is between the base of our brain and the top of our spinal cord.

It’s responsible for the basic housekeeping that keeps us alive and functioning.

This is our life support system. Our hearts beat, we breathe, we digest, we survive thanks to our brainstems. They take care of things that are mostly outside our conscious control, and often also outside our awareness. We’re never aware of our blood pressure until something goes wrong.

Things like arousal, sleep-wakefulness, hunger-fullness, and the delicate chemical balance that keeps us alive are all regulated by the brainstem. And it’s easy to recognize that we have these things in common with most of the animals, such as lizards, fish, birds, and cats.

This part of the brain develops in the womb and is functional by the time we’re born. It’s the first of the three parts of the brain to develop, and it has to be. It’s far more important that your body be able to take your first breath and circulate your blood than it is to regulate your emotions or write an email to your mother. The other two parts have plenty of time to fully develop.

Mammalian brain: The Limbic System

Millions of years after animals had fully functioning brainstems, the mammals evolved. Mammals are social creatures with an emotional life. So with mammals came a well-developed limbic system. This part of the brain sits on top of the brainstem in the center of our heads. It coordinates our emotions, social relationships, and motivation.

The limbic system, our mammalian brain, helps us make emotional relevance out of events.

Your dog gets happy when you get out the leash. He’s associated the leash with walks and has positive emotions about going on a walk around the neighborhood with you.

While other animals may have emotions (birds can definitely sound angry when you disrupt them at a birdfeeder) mammalian emotions and emotional memories are more developed and have a much broader range. And the limbic system is critically important in the formation of long-term memory. We categorize memories by their emotions. More emotionally intense memories last longer and are often more readily recalled.

Not only did it evolve after the brainstem, the limbic system develops second in humans. We are not born with fully functioning limbic systems. Just look at a newborn. He can’t control his emotions. He doesn’t even smile. Sure, he makes simple associations between feelings and events (hungry = upset, full = calm), but he certainly can’t manage all those emotions yet. The brain structures that make up the limbic system aren’t fully developed until about age six. Even then, we continue to develop this part of the brain as we use it. Trauma can have a huge impact on how the limbic system functions. Not only do survivors of trauma often find their emotions (such as fear, anger, and anxiety) are out of whack, their social relationships can suffer, memories are often all-too-present – or completely out of reach.

Human Brain: Prefrontal Cortex

The final part of the brain to evolve was the prefrontal cortex. It became fully developed with the emergence of the higher primates, and particularly with human beings. The term “cortex” literally means “bark,” and the cortex is the thin outer layer of gray matter, like the bark of a tree. “Prefrontal” just means that it’s at the very front. So this is the thin, wrinkly layer of cells on the outside of your brain, just behind your forehead.

And this is a very important part of the brain.

This is the part that is so much more complicated in humans than it is in other animals. It gives us the ability to think and reason.

It makes us rational creatures. It gives us language and empathy. Its key roles are anticipating what is about to happen and planning ahead. We wouldn’t be who we are without this part of the brain.

And as anyone who remembers being a child or teenager realizes, this part of the brain takes a long time to develop. It starts early, but it certainly takes its time. While toddlers learn language, elementary school kids understand cause-and-effect, simple logic, and empathy, the prefrontal cortex undergoes massive reconstruction during adolescence, which in brain development terms lasts from age twelve until about age twenty-four. So the prefrontal cortex isn’t done with its initial development until we’re in our early to mid-twenties.

How the Three-Part Brain Relates to Anxiety

Anxiety is trying to protect us from a very wide range of danger. These threats can loosely be seen as connected to any of the three parts of the brain: survival, emotional-social, or rational.

The survival threats of harm can be from physical sources: immediate ones such as a bookcase that’s precariously leaning over, or a chronic threat like a violent ex that just might show up at your door one day.

The brainstem is responsible for the shut-down response – the freeze response – that reptiles use as a first line of defense under threat. We carry an ancient survival skill of playing dead – either holding perfectly still or going completely limp – and often shutting down our basic awareness of what is going on around us. Under extreme duress, we go into shut-down as a last-ditch effort to survive.

Anxiety can alert us to social threats, too. Back in the early days of humanity, being part of a social group was necessary to survival. Exile from the group was certain death, so your ancestor had better find a way to fit in.

We face that threat of not belonging to our social circles in a dizzying variety of ways today. And even if we might not physically die if we are rejected, it can feel like we might. That’s partly because it isn’t just a legacy from ages past.

As babies and small children, we would die if we were rejected. First, not getting our physical needs met means starving to death. But even in orphanages, they’ve found that when workers who are overwhelmed and understaffed manage to meet babies’ physical needs but not hold, soothe, and pay attention to them, some infants will simply die, even though they had enough to eat.

Belonging to a group is truly life-or-death from the beginning of our lives, and it’s no surprise we continue to be anxious about social rejection.

We face threats on a rational or thinking brain level as well. The primary tasks of our prefrontal cortex are anticipation and interpretation. This leads directly to the human ability to worry. Your dog might tear up the trash can if you come home late to feed him, but he doesn’t worry that you’re near the bottom of the dogfood bag and don’t get paid until next week.

On the one hand, the ability to reason, plan, and anticipate are wonderful blessings that enable us to thrive and live longer. On the other hand, the ability to worry about the future is one of the doorways to much human suffering.

Recruiting the Different Parts

Each of our three brain parts has a different way of causing and responding to anxiety.

One thing that can be helpful to do when we’re anxious and can’t easily calm ourselves is to notice which part of our brain is most anxious.

If it’s mainly in our reptilian brain, you might feel it physically – either your heart is racing and you’re breathing fast or you are feeling spaced out, numb, and sluggish. Or both at the same time – like one foot on the gas and one foot on the brake. If this is the strongest part of your anxiety, try to engage another part of your brain. Connect with another person to turn on your mammalian brain, or recite boring, logical facts to yourself to engage your human rational brain. Even pull out a book and make yourself read a couple of paragraphs about anything.

If your mammalian brain is anxious – you’re overwhelmed with emotions or feeling abandoned or rejected, then engage the human brain or the reptilian brain. This is where breathing exercises, regular exercises, taking a walk or a hot bath can engage your brainstem and recruit it to calm you down.

Likewise, if your human, rational brain is worrying non-stop, it’s time to get out of your thoughts and use your mammalian or reptilian brains. Just focusing on your body, your emotions, or another person – or maybe listening to music – can bring down the intensity of the fear and worry.

The idea of learning about the three-part brain model to help with anxiety is to meet each part’s needs where it is, and to recruit other parts to help when one gets overwhelmed. It takes a little practice, but even the act of practicing can remove you from the anxiety and give you something else to do with your three-part brain.

Anxiety is an uncomfortable part of being a human being. In some measure, almost all of us experience it. We can often point to signs of anxiety in ourselves, maybe a restlessness or rumination, maybe a churning in our stomachs or sense of trying to fight off dread. Or it just may be a sense of activation that spurs us to take care of daily tasks and plan ahead.

With so many of us feeling an extra level of anxiety lately, it’s worth looking at exactly what it is before we delve further into how it operates in our brains and bodies. The Oxford Language Dictionary defines anxiety as, “a feeling of worry, nervousness, or unease, typically about an imminent event or something with an uncertain outcome.”

This describes the both the feelings of anxiety and points to the two main triggers for anxiety: imminent threat and an unknown future. As we’ll discuss, each has a different mechanism in the brain to start anxiety.

Anxiety Signals Threat or Danger

The purpose of anxiety is to prepare us mentally and physically to avoid danger, and if that’s not possible, then to face it. Anxiety’s goal is to protect us. The opposite of anxiety is feelings of safety, not necessarily calm. Anxiety and excitement can physically feel similar.

You can be excited and energized and not anxious as long as you feel safe. Calming ourselves down only works when we can also convince ourselves that we’re relatively safe.

It’s worth stressing that not all anxiety is bad and needs to be “cured.” Anxiety has saved countless lives by protecting us from harm. There are plenty of good reasons to be anxious, and it is okay to be anxious sometimes.

If the Capitol has just been breached and you’re hiding inside it, the most natural feeling in the world is anxiety. It will motivate you to keep you safe. If you have been exposed to COVID, anxiety will help you plan out your next steps to quarantine, get tested, and tell your close contacts.

Two Core Symptoms/Circuits

Neurologically speaking, the feeling we commonly call anxiety comes from two separate networks in the brain. One is called “The Fear Circuit,” and the other is the “The Worry Loop.” Since anxiety is the combination – often in different proportions – of two related but different brain circuits, it’s no wonder it’s so hard to describe. Let’s break it down.

The Fear Circuit

The Fear Circuit centers around the role of the amygdala in the brain. The amygdala is a small, primitive brain structure that is common to humans, mammals, reptiles, fish, and birds.

Evolutionarily speaking, it’s very old, and it has been doing its job as the fire alarm or smoke detector in the brain for many millions of years.

We’ll explore this further in a future post, but the Fear Circuit bypasses the thinking part of your brain when it recognizes danger.

The Fear Circuit is triggered when you face a life-and-death threat. When confronted by a bear, the amygdala registers that your life is in jeopardy and sends out the message to your brain and body to react, even before you are aware you “see” the bear.

It initiates the fight-flight-freeze response, trying to find the best course of action to ensure that you’ll survive the encounter. You don’t actually get a conscious say in which option your brain chooses. People often berate themselves for years about why they responded in a certain way, maybe freezing instead of fighting back, when you don’t get much conscious input. Your basic survival skills step in and take over.

Two of the ways we see the Fear Circuit at work when anxiety becomes dysfunctional are panic and phobia. If you’ve ever had a panic attack, you’ve felt the Fear Circuit at work. The same thing happens when we develop a phobia: an overly fearful reaction to something harmless, or a fear that is well out of proportion to the threat of harm. This is the amygdala sending out a false alarm.

The Worry Loop

Sometimes with anxiety, our conscious minds are very much involved. This is when our Worry Loop is triggered. The Worry Loop is a tract of neurons, or cells in the brain, that runs in a loop between three areas of the brain.

One of those parts of the brain is the prefrontal cortex, where our higher-level thinking happens. Our thoughts, planning, and imagination are all thanks to our prefrontal cortex. So are language and empathy. When our Worry Loop gets overactivated, signals are running in a circle, bouncing like a pinball, engrossing our prefrontal cortex.

This is the kind of anxiety that is uniquely human. It’s thanks to our ability to anticipate and interpret events.

Skills worth the cost of anxiety. And there is a purpose to our worry. Our worry is there to help us plan before we act. Only when it gets out of control and we keep on worrying does it become counterproductive.

Negative bias

Part of the reason we feel overly anxious about unlikely threats is what scientists and mental health professionals call negative bias. This is where our brains play out “better safe than sorry.” We are hard-wired to overestimate danger, threat, and risk.

This is because over thousands of years of human evolution, and in the whole animal kingdom, those of us who erred on the side of caution were more likely to survive to adulthood and pass on our anxious genes.

It is safer to assume a stick is a snake and to jump back than it is to assume a snake is a stick and get bitten.

We are all descended from the anxious survivors who ran or fought, not the easy-going ones who were slow to respond to danger.

Anxiety Exists for a Reason

I will say it again: anxiety is not always a bad thing. The Fear Circuit has probably saved your life more than once, if only by keeping you from stepping out into traffic or causing you to brake quickly when the car in front of you stops. The Worry Loop helps you plan for the future and figure out the best course of action.

Much of this kind of anxiety is the arousal of being alive. It keeps us safe and proactive in the world. We will have imminent threats, and we will need to make plans to perform at our best at times. We need anxiety to do this. Complacency isn’t a very good survival strategy.

There are times when we experience ongoing high levels of anxiety. Some of the time the anxiety makes perfect sense. When there is a chronic threat to your safety, such as living with a violent person in your home, the anxiety is not dysfunctional, the situation is.

For this kind of anxiety, what’s ultimately needed is a solution to the ongoing threat. Some kind of intervention or change of environment is needed. It won’t hurt to learn anxiety reduction skills, but they are only going to be somewhat helpful. How would it make sense to be relaxed in a tiger’s cage?

Dysfunctional Anxiety

All of this talk about different kinds of threats and the anxiety we feel is all well and good when we can identify a real and present reason that we are anxious. But a lot of times we can’t figure out why we’re anxious, or we know that our anxiety is out of proportion to the actual threat.

When it starts to mess with our ability to enjoy life, it’s time to do something about it. We call it an anxiety disorder when it starts to interfere with our ability to function.

You may be anxious to the point you are counterproductive in dealing with your stressors. Or if you can’t do your job, take care of your daily activities, socialize, or you’re spending tons of time dealing with your anxiety, it’s become dysfunctional.

Sometimes anxiety has become a way of life in adulthood. Fear and worry may have been your best chance for getting through your childhood in one piece. Now that you’re safe and there’s no reason to chronically be at red alert, you’re still wired to be overly prone to anxiety. It was very functional and helpful, but now it’s not. While we need to honor the ways you managed to survive your childhood, you deserve a better present.

Stay Tuned

In the next post we’ll be exploring the Three-Part Brain. It’s a model that simplifies the brain into three major parts: the survival-focused reptilian part, the emotional and social mammalian part, and the rational human part. Understanding these three sections of our brain helps us understand how and why we feel anxiety about different things and outlines some ideas about what to do about it.

I’m not someone who likes to be told what to do without an explanation. I refuse to follow directions I don’t understand. It’s caused me problems on more than one occasion, but I know I’m not alone. But once I learn how something works and why I ought to act, I’m likely to follow through.

That’s why I got tired of reading the same advice about anxiety: exercise. I know that’s a thing, but I didn’t feel like trying exercise to relieve anxiety until I found out why it works. It turns out that when we’re anxious, we set off the fight-flight-freeze response in our brains. If we exercise while we’re anxious, our bodies send signals back to the brain saying, “We successfully escaped the saber-toothed tiger. Good job. You can rest now.” And then we relax. That explanation made me willing to try it.

So when I’m asked about what to do about anxiety, I’m hesitant to offer advice without good explanations of the reasoning behind it.

Once we understand a bit about how our brains create anxiety, and why they do it, we’re more likely to try things that might work, and also we can come up with tailor-made answers for our unique circumstances.

But it’s hard to find new, creative solutions unless we understand the principles around what’s going on inside our heads.

My goal is to unpack a lot of the science around anxiety in an approachable way. Over the next several posts, I plan to cover information about anxiety and how it works in the brain.

Topics to Cover

The first thing to address is: What is anxiety? You may know it when you feel it, but we need to break it down, describe it and put it into words.

I’m also going to talk about the Three-Part Brain: the part of the brain we share with the reptiles, the part that we share with the mammals, and the part that is exclusive to primates. The three parts have different priorities and roles, and we need each of them for different things. It’s a great working model to use when we’re trying to figure out what is going on inside ourselves and how to get back on track.

Next is the anatomy of anxiety. There are two different circuits in the brain that create the experience of anxiety. The first is the Worry Loop, the second is the Fear Circuit. Fear and worry are the two basic components of anxiety, and I’ll explain how they each operate in the brain.

For each anxiety circuit, we’ll discuss healthy and dysfunctional anxiety. There is such a thing as healthy anxiety. Up to a point, it serves a purpose. Beyond a point, it becomes a problem. We need to both honor the anxiety that keeps us safe and know when it’s time to do something about it.

There are several different causes of anxiety, neurologically speaking. I don’t mean your ex and your car payment. I’m talking about conditioning, where we learn to be anxious about something, either over repeated exposure, or maybe one traumatic exposure. There are also genetic and environmental factors that cause one person to be more anxious than another when they’ve been through similar circumstances.

I’ll also cover treatments for anxiety. There’s a lot of diversity here. There are plenty of things you can do yourself, whether focusing on calming your body down or engaging your thinking brain to get your cognitive self back in control of the situation. We’ll also cover different types of therapy, should you need some professional help with your anxiety. And we’ll address medications. I’m not a medical doctor or a prescriber, and I can’t give medical advice, but I can cover how different types of medications work in your brain, so that you are armed with information if you decide you need to talk to your doctor.

Bite-Sized Portions

While the science behind anxiety has been rapidly progressing over the last couple of decades, and a number of great books have been written on anxiety, a lot of people prefer bite-sized pieces of information. Too much information all at once doesn’t help, and asking someone to read a book about anxiety often triggers anxiety.

Lots of people come to therapy too stressed out and with no free time or energy to read a long book. But they do want to know how their brains work. And this information will be useful to them when anxiety or panic strike, so it’s my job to educate them. But I understand that sometimes it’s hard to remember what you learned while you’re anxious. That’s a normal anxiety response. So if I put it in writing, I’ll have something to refer people to later.

One of the best books about trauma (and the anxiety that goes along with it) is The Body Keeps the Score. It’s an amazing book, and I highly recommend it. But unfortunately, eight times out of ten, if a client tells me they have tried to read it, they also say they were triggered by it and had to put it down.

I totally get it. I was triggered the first time I read it, even after years of doing my own healing work. That volume of really dense information is also highly emotionally charged, so readers get triggered, which shuts down the thinking part of the brain. Then it’s next to impossible to read, much less remember anything you’ve read.  

Conclusion

This past year has been a hard one for many of us, with global and national crises creating and compounding personal crises. And anxiety has been one of the effects of this period that has been difficult to escape. I’ve seen it everywhere, not just with clients, but in friends and family, and also in myself.

Dealing with my own anxiety in this last year involved an ongoing discussion in my head. I’ve been managing it, but it’s taken extra, conscious effort at every turn. And as I talk to people, so many who are struggling, I return to the lessons I’ve learned about myself. I know will go above and beyond when I understand why I’m doing something in the first place. And I’m know that I’m not the only one. Knowledge gives us power over anxiety. While it’s not a magic cure, it outlines a path to finding a solution to your anxiety that works best for each of us.