Fear and the Brain
Fear is a state that arises when the brain and nervous system encounter clear troubles, problems, or real or potential dangers. This triggers a chain of events that leads to avoidance or hiding behaviors—in other words, attempts to escape from the source of the problem or at least hide until the danger passes. Programs related to fear (or, as physiologists say, passive-defensive behavior) are basic programs of our brain, innately embedded in our neural networks. They are responsible for our safety.
The most obvious source of fear and the most obvious stimulus that triggers defensive behavior is pain, which occurs when our cells and tissues are damaged. Damaged cells and tissues send signals through special nerve fibers to the spinal cord. From there, the signal travels to the brain, launching a variety of reactions, from simple reflexes—like pulling your hand away from a source of pain (also a passive-defensive program)—to complex emotional states that help us learn to avoid dangerous objects, like not sticking a finger in an outlet or grabbing a hot iron. Pain is the most obvious trigger for fear and fright, and biologically, this makes sense.
Besides pain, any overly strong stimulus can also trigger these states and reactions. When there is a very bright light or a very loud sound, we also try to avoid such places, hide, move away, or at least cover our ears and close our eyes.
Recognizing Danger
A more complex level is recognizing the image of an enemy. Many animals innately know what a spider, snake, or predatory bird looks like and react accordingly—by fleeing or hiding. In any case, they try to avoid contact with an innately significant dangerous signal. For the human brain, such reactions to the image of an enemy are less clear. Some people are afraid of snakes, some are not, and some even love them—otherwise, how would we have herpetologists? Some dislike spiders, while others are quite fond of them, and there is even a profession—arachnologist. Still, most people are wary of snakes and arachnids. This is genetic memory, where our visual cortex is innately able to pick out these signals.
For example, if you are alone in a dark forest and see two glowing dots at knee level approaching from afar, you will naturally feel fear and anxiety, assuming it’s a predator. You look into the bushes in fright, only to find it’s just a hedgehog, and you feel great relief. In any case, glowing dots in the dark, sudden creaks, and rustles innately reach the fear centers and defensive behavior centers in our brain. Sensory signals like these are skillfully used by thriller and horror movie creators—when a character walks alone at night in a dangerous place and nervously looks around, we experience those emotions of fear along with them because our brains are programmed that way.
The Brain Structures Behind Fear
The structures that generate fear and defensive behavior are the hypothalamus and the amygdala. The hypothalamus is the lower part of the diencephalon. In the back of the hypothalamus are nerve cells that generate either fear or aggression responses.
We are built so that we can react to real or potential danger in two ways: either by fleeing or by fighting. Fleeing is a passive-defensive reaction, while resisting or fighting is an active-defensive reaction. At the first level, our brain detects the danger, and then a decision is made to hide or fight.
In the back of the hypothalamus, there are nerve cells that, when stimulated, cause panic, and just a millimeter away are neurons that, when stimulated, cause rage. The hypothalamus largely executes defensive reactions, including their endocrine and autonomic components—like releasing adrenaline or making the heart beat faster and pupils dilate. The hypothalamus has a commander structure called the amygdala—a cluster of gray matter deep in the temporal lobes of the cerebral cortex.
We have temporal lobes, with the cortex on the outside and structures called the amygdala deep inside. Potentially or actually dangerous signals converge there. The amygdala recognizes innately significant danger signals and sends them to the hypothalamus, which then triggers either a fear or aggression response. The balance of amygdala activity with other brain regions largely determines whether we are more aggressive or more prone to panic reactions.
Temperament and Defensive Reactions
At the level of temperament, this balance is what’s called cholerism. Choleric people are more aggressive, while melancholic people are more prone to fleeing, hiding, and fear. This is a crucial part of our personality. If evolution preserved both types of reactions, it means both are necessary. Sometimes it’s better to react actively and aggressively, to attack and resist, and sometimes it’s better to avoid conflict.
If we look at animal or human behavior, we see that usually, the passive-defensive reaction—fear or hiding—is chosen first. First, it’s more energy-efficient: you don’t waste energy fighting, you just quietly sit in the bushes and hope the problem passes you by. Second, active-defensive reactions often lead to actual fights, which means a risk of injury, and injury is very bad, so if you can avoid a fight, you should. Even large predators like tigers or bears will hide in the bushes and avoid being seen. True aggression usually starts only when you suddenly surprise them—especially if it’s a mother with cubs. That’s when real aggressive attacks begin.
From a global biological perspective, passive-defensive reactions are better. They are non-traumatic and require less energy, so the brain readily chooses them. When we use them, we either hide or run away. If the danger passes safely, we experience positive emotions, and the neurotransmitter responsible for these positive emotions is norepinephrine. If there was danger and we handled it, norepinephrine is released. Most people know this feeling from childhood games of hide-and-seek—how scary and exciting it is to wait while someone looks for you, and how great it feels when you aren’t found. That’s why people go to horror movies and thrillers, where something unpleasant is clearly happening—someone loses a limb, or monsters jump out of a character’s chest.
Fear in Everyday Life and Society
People who go to thrillers want to experience fear and then return to a state of safety. You sit in a chair, watch the movie, and know it’s not happening to you. You eat some more popcorn. This jump from danger to safety is what attracts viewers to horror movies. There are many such people, and it’s a whole business sector. Marketers actively use fear to sell us all sorts of products—insurance, medical devices, car and home alarms. In all these cases, marketers appeal to the amygdala and hypothalamus, scare us, and immediately offer a solution.
Politicians use similar mechanisms to scare us. Of course, fear is also significant in religious doctrines: if you sin, bad things will happen to you. In this case, the fear response can be very important and educational, especially if instilled from childhood: “God is watching you, things will go badly, so behave.” In general, we learn a lot through fear. There’s the carrot method and the stick method. You can learn to do something to get a reward, or to avoid something bad.
Learning Through Fear: Experiments and Memory
The second component is also based on fear centers. There are two main options, which we use when working with our lab animals, like white rats.
The first option is: don’t do something, or something bad will happen. For example, you tell a child not to stick their fingers in an outlet, or something bad will happen. A good, obedient child won’t do it. A very curious child will try, get shocked, and then avoid the outlet. In rat experiments, we put a white lab rat in a box with two compartments, one light and one dark, connected by a small passage. The rat quickly moves from the light to the dark compartment—a passive-defensive reaction, since rats are burrowing animals and dislike bright light. But in the dark compartment, the rat receives a strong electric shock. After the shock, we remove the rat and put it back in the box a week later. Even after a week, 90% of rats remember the unpleasant experience and stay in the light compartment. It’s uncomfortable, but the dark part is worse. This allows us to study how memory forms based on passive-defensive behavior.
Such experiments are not done to torment rats, but to develop drugs that improve memory, since creating such medications requires adequate animal models.
So, the first level is learning not to do something, or else something bad will happen. The second option is: do something, or else something bad will happen. For example, clean your room or you’ll be put in the corner. In animal experiments, we use a method where a rat is in a chamber and must jump onto a shelf when a bell rings, or else it receives a mild electric shock (not too stressful, but significant). The bell becomes a trigger. The rat quickly learns to jump onto the shelf at the sound of the bell and then sits there looking quite happy: norepinephrine is released (“I know how the world works, I escaped danger, I did well”).
These models can be used to test new psychotropic drugs that improve memory. They are also suitable for studying chemicals that reduce anxiety and panic. All this is an important part of neuropharmacology and research on experimental animals.
When Fear Becomes Harmful
If fear happens too often, a state of chronic stress develops, which is not good. Temporary fear experiences can even stimulate our brains and make life more interesting. People sometimes deliberately put themselves in potentially dangerous situations to come out on top—or at least go to horror movies. But if fear repeats over and over, exhaustion occurs at the level of the autonomic nervous system and endocrine systems. The hypothalamus starts to function poorly. Problems can arise with the cardiovascular system and many hormones. An excess of negative emotions can develop, which is a path to depression.
Fear is an important component of our mental life—a signal that warns us of real and potential dangers. But too much fear is not good and can seriously disrupt our mental functioning.