The Seat of the Survival Instinct
The Biology of Fear
In the previous chapter we discussed the role of agitance and discomfort as they relate to the survival instinct. Now, we’re going to turn our attention to where these reactions take place in the brain and body. As we have discussed, the mind and body are constantly seeking balance. But so often this balance, or alignment, is fleeting, and unfortunately undermined by chronic states of agitance. Although agitance can represent an incongruity between us and the outside world, more frequently it originates chiefly from a lack of balance within us—between our cells and in our biochemistry, nervous system, and even brain. In fact, it’s within the brain that most of the jockeying takes place. Once agitance levels are no longer manageable, we begin to feel discomfort both physically and emotionally. The question is, What, exactly, is going on in this subtle yet profound cascade of events? How is this all possible? That’s what we’re going to explore.
We humans are actually the proud owners of three separate brains, all reflecting different stages of development and evolution. Our first and oldest brain dates back to the time of reptiles. We continue to share this part of the brain with reptiles and birds. For us, it’s housed in the brain stem and cerebellum. Not surprisingly, this ancient part of us governs very basic but vital functions, and receives direct input from our entire body. For example, the brain stem is involved in the regulation of our heartbeat, breathing, blood pressure, circulation, digestion, and the famous fight-or-flight response. The brain stem includes the medulla, pons, tectum, reticular formation, and tegmentum. The cerebellum is involved in the orchestration of our body’s movement. This region of the brain is sometimes called the R-complex, with the R representing reptile. What stands out about this part of the brain is that it’s emotionless, and is strictly instinctual and automatic. It’s what saves us without our needing to think or feel much of anything.
It wasn’t until we evolved into mammals that the next level of brain development occurred. This part would become the limbic brain, which sits on top of the brain stem and cerebellum. The limbic brain receives input from the brain stem, attaching emotions to these impulses. This is why mammals, such as humans, primates, dogs, cats, and dolphins, all have emotional responses to their world. But like the brain stem, the limbic brain’s responses are often outside of awareness and are automatic.
In the next stage of evolution, mammals developed a new part of the brain, layered on top of the limbic brain, called the cerebral cortex. The more evolved the mammal is, the larger the cerebral cortex. And the larger the cortex, the more developed the brain function is. When you picture a human brain, for instance, you likely see lots of folds and creases on the outside. That’s the cerebral cortex, and it follows that the more folds that exist in the cerebral cortex, the greater the surface area, which translates to more advanced capabilities. It is this part of the brain that gives us the higher reasoning abilities—the ability to think analytically and logically, problem-solve, plan for the future, and think abstractly.
As you can see, the evolution of the human brain, like civilization, went from primitive to more advanced, and each new and better “layer” was simply built above the other. By virtue of this evolution, the human species was given new tools that enhanced its survival. In other words, each new layer of sophistication equipped us with a better, more agile brain that could help us live longer and better preserve our species. With the development of the cerebral cortex, we suddenly found ourselves with much better control over our limbic impulses, or our emotional reactions to the world. This is what’s called top-down brain functioning, whereby the cerebral brain regulates and attempts to control the older brains below. But it’s here where the inherent problem develops, as both structures, the cerebral brain and the limbic brain, are often innately driven to assert control over one another, each presuming that its priorities are greater than the other’s. The cerebral brain claims to be smarter than the limbic brain and is often quick to dismiss it, resorting to an overregulation of the limbic brain by lecturing it with logic and reasoning. But the limbic brain feels its needs are more pressing, and it will have nothing to do with being lectured to, so it will assert its needs in a physical manner or in an emotional manner with temper tantrums. This sets up an ongoing struggle to somehow find a balance between these two parts of our brain. Although overall the brain itself is driven to strive for balance, suffice it to say a détente is not always easily achieved. Since sustained balance is difficult to attain, we find that the cerebral and limbic brains can wax and wane in terms of their influence. And yet, the goal ultimately is to have these two separate regions work together in some sort of coordinated, harmonious way.
As I also briefly noted earlier, the limbic brain, like our reptilian brain, is very much focused on basic survival functions, providing the home ground of our more primal emotional states, particularly anger and fear. It is important to note that these primal emotions are pure; when they originate, they are without cerebral analysis, reflection, or interpretation. Put another way, they are automatic and reflexive. Since the limbic brain receives its basic impulses from the brain stem, its reactions are swift as it quickly attaches very primal emotions to these impulses that are geared toward preservation and survival. And the limbic system has a strong connection to the autonomic nervous and endocrine systems, which we’ll talk about shortly. One particular area of the limbic brain that has received a substantial amount of attention related to anger and fear is the amygdala. In studies in which scientists sever the amygdala in animals, they find that the animals lose their aggressive behavior and even their ability to react normally to fear. By the same token, when scientists stimulate this area of the brain, they achieve the opposite effect—the animals exhibit more aggressive behavior.
The limbic system’s actual anatomy includes the hypothalamus, the hippocampus, the amygdala, and the nucleus accumbens, or the so-called pleasure center of the brain. So within the limbic brain we find the actual physical and emotional basis for primal experiences such as hunger, pain, sleepiness, anger, fear, and pleasure. A central part of this limbic brain is the basal ganglia, which houses two important areas related to behavior—the nucleus accumbens and the ventral striatum. What makes these areas so critical is that they are connected to a neurotransmitter called dopamine and the brain’s natural opiates, called endorphins. Dopamine is a brain chemical that strongly influences behavior such as habits and addictions. The endorphins influence how these habits and addictions are experienced, particularly the pleasurable aspects.
When we experience something pleasurable, these brain chemicals have a significant impact on other parts of the brain and the body to urge us to continue whatever behavior or seek whatever stimulus is creating the pleasurable sensation. Let’s take an example. Many people find themselves drawn to chocolate. This has its physiological roots: Just the thought or sight of chocolate can create a dopamine surge in the limbic brain. Every time this pairing occurs—the thought or sight of chocolate and the release of dopamine—more power is established between these two things. (This can also happen in relationships, particularly during the early, infatuation phase. That rush of euphoria we feel at the mere thought or image of our new partner is made possible by a dopamine surge.) When we actually eat the chocolate, the chocolate then causes a release of opiates in the brain that stimulate our pleasure centers, which further cements our behavior of eating chocolate. What’s interesting about the dopamine surge, however, is that it actually begins to drop once we get what we want and start consuming the chocolate. So it’s more the mental anticipation of having the chocolate than the reality of eating it that creates the dopamine surge. (With relationships, we all know that those initial feelings of rapture weaken over time as those surges of dopamine fade.)
Overeaters similarly become trapped within a loop of dopamine scarcity. After a long history of bingeing on high-calorie foods, they enter a chronic state of dopamine withdrawal, which, as you can imagine, leaves them in an elevated state of discomfort. In an effort to restore their dopamine levels and feelings of comfort, they find themselves racked by compulsive cravings for the very foods that caused the problem in the first place. Of course, this pummels overeaters in two ways: Not only does the lowered dopamine make them eat more, but the actual overeating itself further reduces their dopamine levels.
On the flip side, when the limbic brain experiences fear, another process unfolds with similar outcomes. The moment we become fearful, a brain chemical called corticotrophin-releasing factor (CRF) is unleashed in different areas of the limbic region, particularly the hypothalamus and amygdala. CRF begins to drive a stress response in the body that entails a sequence of events known in scientific circles as the hypothalamic-pituitary-adrenal axis, or HPA axis, as it involves all of these components of the brain. When CRF first acts on the hypothalamus, it stimulates the release of another chemical called adrenocorticotropic hormone (ACTH) from the pituitary, which then causes the adrenal glands to release glucocorticoids, stress hormones such as cortisol. These glucocorticoids in turn increase many biological actions, affecting our blood sugar and influencing immune function. The adrenal glands respond further by launching other adrenal hormones such as epinephrine and norepinephrine, which activate the sympathetic nervous system. This is the classic fight-or-flight reaction. When it takes place, your heart rate and blood pressure increase, changing the flow of blood throughout the body. But what’s most interesting about this whole process is that the CRF activation leads to dopamine reduction. So not only is our fear reaction physically uncomfortable and emotionally upsetting, but the reduction in dopamine creates a very negative, dysphoric feeling. And, similar to dopamine surges cementing a certain behavior, this contrary reaction does the same; the discomfort and fear reactions also cement powerful responses in the body. As a result, we feel a strong urge to somehow find a way to end this discomfort and fear in the same way the pleasurable loop drives us to maintain the pleasurable sensations through certain behaviors. This compelling desire to terminate the discomfort and imbalance is wired within us as a very basic means to assure our safety and preservation. The limbic brain’s powerful wiring and undeniable need to preserve our safety at all costs is what we are calling our survival instinct.
Hence, at the heart of our rising levels of agitance and discomfort, which trigger the survival instinct, is a simple drop in our dopamine levels. Discomfort goes up, and dopamine comes down, plunging us into a vicious cycle. This explains why overeaters are driven to eat more, as I’ve described, or panic attack sufferers increasingly begin to avoid even innocuous situations that result in dopamine depletion. These intense reactions are based in the limbic response. Whether they are an addictive urge related to compulsive cravings for food, sex, drugs, or alcohol or are instead a compelling fear or anger response that’s traveling down the HPA axis, they ultimately all represent an out-of-balance state or nonalignment within the brain. These reactions can insidiously generate other imbalances in the brain and body that further create problems rather than solving them.
Simply put, the limbic brain is vigorously driven by pleasure and pain. At one time, when we were a primitive species, this certainly had some preservation value. But as we evolved and became much more complex and sophisticated, these fundamental drives didn’t evolve with us, remaining absolute rather than being attuned to subtleties. If you feel uncomfortable, for instance, then your limbic brain interprets that as a signal that your safety is being seriously threatened, which then triggers a drastic reaction to avert danger and maintain your safety. Your limbic brain by its very nature is not very effective at evaluating different degrees of discomfort and fear. Hence, being at the mercy of these primary drives severely conflicts with the needs of a more complex society and civilization, in which people cannot be constantly acting on their needs for pleasure and fear. But this is where the survival instinct poses a problem, in that it doesn’t easily make distinctions, and tends to view all discomfort and fear as an ultimate threat to our survival.
What’s more, as people find themselves enslaved by an endless cycle of dopamine deficiency—in which certain behaviors, such as overeating and addictions, develop to ease the discomfort in the short term—the likelihood of experiencing future fear reactions is increased. And the chronic release of CRF over time decreases the amount of available dopamine. This fear circuit grows all the more sensitized such that it doesn’t take much to create discomfort and provoke a survival instinct reaction. Put simply, the more discomfort we feel, the greater the likelihood we’ll experience fear. And the more fearful we become, the more uncomfortable we become. These two forces feed on each other and imprison people within a dangerous spiral.
Two-Way Street, One Busier Direction
With our limbic brain having a hard time deciphering different levels of fear, the emergence of our “new brain” provided us with an essential counterbalance, which afforded us greater survival skills. As you can probably figure out, the name “cerebral cortex” reflects what it’s designed to be—the “cerebral” part of us, our more reflective, analytical, rational, and logical part. The cerebral cortex comprises a number of important areas, including the prefrontal cortex, whose primary function is to balance out the impulses of the limbic brain. Like a CEO who orchestrates the many arms and functions of a company, the prefrontal cortex attempts to make sense out of these impulses, remove their absolute nature, and sort out whether a fear response is appropriate. Conversely, it also serves to modulate pleasure seeking. So we can see that the cerebral cortex functions became particularly important as we evolved as a species and developed civilizations and societies. By balancing out our basic drives, it allows us to function more adeptly within a world that is no longer black-and-white.
But preserving the balance between these two brains is not often easy. It turns out that this is not a two-way street, or a process in which each part of the brain gets equal billing. There are far more brain signals going from the old brain to the new brain than there are from the new brain to the old. As a result, the limbic brain is imbued with a greater power. This is likely due to the fact that this part of the brain evolved first and in a way that allows us to respond quickly to danger, without having to waste time processing danger signals. This was useful at one time, when danger was a large part of our lives. But now, as we know, it’s much more rare. The consequence of this built-in favoritism, however, is that it gives the limbic response—and the survival instinct—a great deal of leverage, and an ability to bypass our more rational, thinking brain. This is why gut responses often take precedence over more reflective processes. It also explains why it’s much more difficult for the cerebral brain to gain more control over the limbic brain. And, as you can imagine, this puts us more at the mercy of our survival instinct, which has come to be overreactive in our modern lives.
In addition, it’s important to point out that since the limbic system has more direct connections to the sympathetic nervous system, its impulses can bypass the cerebral brain. This is why we can find ourselves reacting in a strong physical way even without being aware of any thoughts. Have you ever noticed, for example, that your heart is racing or that you are getting heated up or sweating without knowing why—only later to identify the source of your concern? It could relate to something that was said or even a certain smell or an old memory that was triggered. Notice that your visceral reaction preceded your awareness. So just these gut reactions become capable of eliciting a powerful physical response in the body.
Several studies have looked at how effective humans can be in regulating this limbic input. Some of the more interesting ones have examined the hunger response, which can radiate from the nucleus accumbens or the pleasure center in the limbic system. In one particular study, women were given a piece of desirable food. They were told to use cognitive techniques to control their limbic brain’s response to the food. By forcing themselves to employ cognitive techniques, chiefly telling themselves that they should not be hungry or want the food, they were activating the prefrontal lobe of their cerebral cortex. The researchers then observed these women’s brains through a functional PET scan and noticed that in fact their prefrontal lobes were activated. But that wasn’t all that lit up on the screen. Their pleasure centers were activated as well. So even though the women were telling themselves they were not interested in the food, their limbic brains weren’t buying it.
Other studies have looked at meditators to see how effective they could be in altering the limbic input. After all, if meditators can control their minds so well, then it would seem logical to assume they are better able to control their limbic responses. Interestingly, some studies have shown that experienced meditators can indeed influence limbic structures such as the amygdala, and other brain structures, such as the insular cortex, that attach meaning to physical sensations in the body. But even so, most of these studies prove that it takes quite a bit of experience in meditation to achieve such results and be able to fully regulate the limbic input.
Extreme Cases Point to Limbic Dominance
A great way to illustrate the limbic brain’s overpowering quality is to consider post-traumatic stress disorder (PTSD), a condition we’ve heard a lot about lately with soldiers returning home from war in Iraq and Afghanistan. This disorder is the perfect example of what happens when the limbic system goes awry: The cortex becomes unable to manage and contain the limbic brain’s sensitivity and input, and the individual is at the true mercy of the survival instinct. Scientists have looked into how these regions of the brain are affected by PTSD, and have found that veterans’ cerebral brains are less effective at controlling the limbic side of things, leaving the limbic brain more firmly in charge and resulting in a lack of balance, or nonalignment.
A similar finding has been observed by a group of researchers led by Dr. Lisa Shin, of Tufts University, who noticed that people suffering from PTSD have an exaggerated amygdala response while also showing a diminished cerebral or prefrontal lobe response. Again, this means that these individuals have developed a condition in which their brains are less capable of dealing with situations that rely on the logical, rational, cerebral parts. Instead they are driven by their limbic side, which takes over the controls like a toddler behind the wheel of a car and provokes the survival instinct. The cerebral brain is practically paralyzed, unable to determine where the limbic brain is going.
Another example of limbic dominance is found in public speaking. When asked which is more frightening—public speaking or being diagnosed with cancer—many people would rather learn they have cancer than get up in front of a large group! And even though people know that their fear is irrational, they become immobilized at the idea of having to confront an audience. This may sound absurdly counterintuitive, but not when you consider that the fear of public speaking stirs up the issues of judgment, acceptance, and the possibility of rejection. Although it may not seem logical, the limbic brain interprets these types of feelings as there being a life-threatening emergency, leading the survival instinct to take action. These gut reactions are rooted strongly in the limbic brain, and this is an excellent example of how the limbic brain overrides the logical and reasoning part of the cerebral brain.
This also helps explain the odd, erratic, and often irrational behavior seen in extreme cases of PTSD. Last year, when the news reported on an American soldier who shot and killed seventeen Afghan civilians, including children, the media immediately began questioning whether PTSD was to blame. More could have been involved than just PTSD, and at this writing we still don’t know what, exactly, transpired. But if we could have seen inside Staff Sergeant Robert Bales’s brain during his shooting spree, it’s quite possible that we would have witnessed a total shutdown of his cerebral side while his limbic brain, at the mercy of his survival instinct, held the firearms.
If your cerebral cortex cannot help manage the overly dramatic messages springing from your limbic system, you cannot effectively control your sense of fear or gauge the magnitude or seriousness of that fear. And this becomes the very basis of the survival instinct. As we continue to experience a chronic state of discomfort and fear, over time we may in fact destabilize the balancing system in place within the brain. This unfortunately leaves the limbic system in an activated state, while at the same time making us less and less in control of keeping it in check. The longer we sustain this elevated level of discomfort, the greater sensitivity we develop to it, and the more often our survival instinct is pressed into action. It ultimately takes less and less discomfort to spark a fear reaction and ignite the survival instinct. Thus, the more overreactive the limbic response becomes, the greater the role that the survival instinct and discomfort play in our lives, and the more control they exert on our behavior and our chemistry.
Another very important part of all this is that when the limbic system experiences fear and then triggers the sympathetic nervous system’s fight-or-flight response, the trauma and fear that remain after the incident are even more encoded into the brain and body. This explains why traumatic experiences can lead to a dramatic change in someone’s emotions and behavior. The brain and body evolved in such a way that these life-threatening situations would be remembered so that we could avoid them and be safer in the future. Unfortunately these encoded links between the limbic system and the sympathetic nervous system make these reactions very difficult to change or modify.
To bring another example into the picture, consider that you are flying home and experience extreme turbulence, which then provokes a significant amount of fear that is also inflamed by other passengers showing signs of concern and trepidation. This then creates a sympathetic response within you, and you may find that from that point on you become fearful of flying. It’s like that old saying about getting back on the horse quickly if you fall off it: If you don’t get over your fear of falling off a horse right away, you’ll be fearful of horses and horseback riding forever. Fear reactions such as sheer panic or anxiety attacks are yet another perfect example of this. Anyone who has experienced a panic attack while driving on a busy freeway knows that it can be a challenge to get back on the highway again without fearing another panic attack in the same setting.
There is an old expression originally espoused by the late psychologist Donald Hebb: “That which fires together is that which becomes wired together.” In other words, two things that happen at the same time become embedded within the brain together. So when two sets of neurons (brain cells) are triggered at the same time, even if they are totally separate events at first, the relationship between these two neural networks is now formed and they can become wired together—forever linked to one another and controlling all future firings of this now single set of conjoined neurons. This is how panic attacks can become forever connected to freeways or a certain food becomes associated with nausea. Therefore, if one of these events occurs in the future, it then triggers the neural network of the experience that’s now been bonded with it.
Why does this happen? The fear that is experienced in such a setting can be so significant that it becomes attached to driving on the freeway in the future. In fact, it can begin to spread to other driving situations as well, from driving on a regular road to driving in your neighborhood. Even though it isn’t logical to the cerebral brain, the limbic brain’s survival instinct is now firmly in control, and as long as driving is connected to fear and danger—which to the limbic brain means potential death—it will avoid any hint of these situations in the future.
Is there a way to manipulate the conditioning of these “wired together” neural networks? A number of studies have determined that yes, it’s possible to block the damaging effects of traumatic events and change how they are encoded within the limbic brain. In essence, there’s a way to temper or even squelch the fear response. Medications such as beta blockers, which interfere with the sympathetic response, can achieve this, significantly reducing the traumatic experience, dampening the stress response, and helping the individual recover significantly quicker.
Our Genes Are at Stake
If it wasn’t enough to be racked with fear from the survival instinct, there is growing data in the field of epigenetics that suggests that strong external influences such as fear can actually alter the expression of our genes. Epigenetics is a burgeoning field of study that examines changes in how our genes behave that are not related to alterations in DNA sequences. Although our DNA remains fixed and identical in all cells for our entire lives, there is now evidence to show that our genes don’t act exactly the same in every cell. The same gene can express itself differently from one cell to the next, despite the same underlying DNA. These shifts in genetic expression can happen throughout our lives, depending on what we’re exposed to in our environment. By “environment,” I’m not referring just to classic sources of toxins and pollutants that can change our genes’ functionality, but also to other forms of external “toxins” that can indeed affect our genetic expression. Child abuse, for example, which is characterized by trauma and fear, has been found to leave a profound epigenetic mark, strongly influencing how genes control the HPA axis, leaving these regions of the brain to react differently than they would otherwise.
What makes the subject of epigenetics particularly relevant to discomfort and the survival instinct is that the HPA axis of the brain is fiercely associated with the fight-or-flight response, which is the most obvious expression of the survival instinct. Considering this, we can see how chronic fear and discomfort might lead to genetic changes that would result in the survival instinct becoming overly sensitized. In addition to child abuse changing how individuals react to fear due to changes in their genes’ expression, researchers have also discovered a potent connection between these changes and risk of suicide. As reported by phys.org, according to Canadian researchers Michael Meaney and Moshe Szyf at McGill University and the Douglas Institute in Quebec, “The function of our DNA is not as fixed as previously believed. The interaction between the environment and the DNA plays a crucial role in determining our resistance to stress thus the risk for suicide. Epigenetic marks are the product of this interaction.” Hence, our inability to manage fear and discomfort can lead to serious consequences that can result in a significant alteration of our genes.
The point at which we’re living in a chronic state of heightened limbic reactions is the point at which we’re vulnerable to developing patterns, habits, and routines that attempt to manage these reactions, which leave us feeling out of control and overwhelmed. And without healthy strategies to manage our discomfort and the subsequent survival instinct, we begin to develop unhealthful strategies that have short-term value, can cause long-term harm, and have a profound effect on our health and our lives.
What kind of habits am I talking about? Those that are much more than an inconvenience or trite behavior. I’m referring to habits that prolong our sense of imbalance and the mismanagement of the limbic brain. These types of habits are much more insidious, and much more universal. In the following chapter, we’ll discuss how we fall into unhealthy traps in our attempts to tame the ever so overreactive survival instinct.