The Emotional Brain

Find out what goes on to create human perception and experiences of emotion — and why?

Head-and-heartEmotions as they are experienced can be broken into three categories: primary emotions, secondary emotions, and background emotions. Primary emotions are experienced as a byproduct of a stimulus-response chain of events; these emotional responses have, to some degree, been hardwired in our brains over the course of evolution. Fear, anger, disgust, sadness, and joy are the “chairs of the board” of primary emotions, and whether or not other board members exist remains under debate.

Secondary and background emotions are the product of an internal feedback loop. While the emotions involved in primary emotional reactions can also play a part in secondary and even as background emotions, nonprimary emotions are more likely to be some dues-paying subsidiary of a primary emotion. For instance, fear as a secondary emotion might feel more like anxiety, stress, or shyness; secondary emotions related to joy might be experienced as ecstasy, pleasure, or amusement.

Joseph LeDoux, a professor and researcher at the Center for Neural Science at New York University, maintains that the list of basic (primary) emotions is nothing other than a list of the adaptive behaviors crucial to survival. Fear, for instance, is obviously related to survival: fear helps you react instantaneously to a stimulus you perceive as dangerous (for instance, a snake slithering toward you) and survive the event. So how does it work?

Primary Emotion: Introducing Fear
Evolution has graced us with the amygdala, an almond-shaped component of the ancient basal ganglia that is involved with aspects of emotion and memory formation. The amygdala allows an instantaneous, unthinking reaction in the face of a threat; sort of a survivo-matic autopilot. As Joseph LeDoux says, “When it comes to detecting and responding to danger, the brain just hasn’t changed much. In some ways we are emotional lizards.” A snake advances–or even wiggles around a bit–and you jump back. Only after this initial reaction do you think about what’s going on and plot a more reasoned path of hasty retreat.

Two main pathways through the brain are involved in a fear reaction. Sensory input–for instance from the visual cortex–scurries over the thalamic pathways (which are subcortical: ancient, lizard-like, and not involved in cognition) to the amygdala. The thalamic pathways to the amygdala do not differentiate among stimuli (which helps the message move as quickly as it does), so the information that reaches the amygdala is something along the lines of: “Danger! Danger!” The amygdala sends signals to other regions of the brain–including the anterior cingulate and the basal ganglia. Nerves pulsing their message of fear reach the gut, heart, blood vessels, sweat glands, and salivary glands, causing the stomach to tighten, the heart to race, blood pressure to rise, the feet and hands to turn clammy, and the mouth to go dry. The skeletal muscles react, tensing up, and the smooth muscles increase activity, contracting the blood vessels and causing pallor. The pituitary gland sends its own missives to the adrenal gland (which will eventually send hormones coursing through the blood back to the brain to help deal with the stress). You jump out of your seat.

The second pathway takes the sensory input–such as that from the visual cortex–on a relatively leisurely jog over the cortical pathways (more modern, more precise, and slower) to the cortex. The information delivered over the cortical pathways is better defined: “Snake! Slithering toward me! Flicking its tongue! At me!!” This message is time-consuming, both to send and to interpret; you wouldn’t want to depend on your cortex to save you. Once this information reaches your cortex, you can start to formulate your backup plan. Your body and brain are primed (via the thalamic pathways), and all you need is a little cognitive input, a little thought, to finesse your escape. The second pathway, after a short stopover at the cortex, continues back to the amygdala, where it meets up with the original thalamic pathway.

The amygdala continues the state of alarm by sending signals to many parts of the cortex ordering them to pay attention to the aspects of the situation that are most relevant to survival (whether the snake is still slithering and in what direction, what its beady little eyes seem to be focusing on). The amygdala also wakes up the arousal systems of the brain so that brain and body continue to focus completely on the threatening stimulus. You would have a hard time doing math at a time like this–and clearly, if you are to survive, you wouldn’t want to. The arousal systems, of course, flood the amygdala along with the other relevant parts of brain and body, and thus the amygdala becomes even more aroused and repeats the cycle of arousal and so on and so forth.

At the same time, the body is dutifully sending alarmed impulses back to the brain, reporting on the readiness of the various organs and muscles. Everything coalesces in the amygdala, that grand coordinator of fear reactivity, and you keep leaping over desks until you reach the door–and then you run.

Once the snake encounter has been survived, the emotional memory of your fear and the cognitive memory of the snake become a learned emotional response that allows–and motivates–you to plan for the snake. You might approach your next class in this room more cautiously, make sure to close the classroom door, and check that the biology teacher in the next classroom has secured the class “pets.” Because you have cognition, you can not only react to the snake to make sure you survive that first encounter, but also act on your knowledge and emotional fear of the snake by plotting future courses of action. Thus a primary emotion moves, through experience and learning, into the realm of secondary emotion.

Preparedness Theory: The Boy Scout of Fear

Each species is evolutionarily prepared to be conditioned to certain stimuli, predators being the obvious example. In the realm of fear conditioning, each species is prepared to react to and be conditioned by stimuli such as specific combinations of largeness, swiftness, loudness, and, of course, the consequences of contact with a threat, such as pain from being bitten. In a laboratory setting, it is possible to undo some fear conditioning to a degree, so that a rat conditioned to fear a buzzer can be convinced otherwise. However, buzzers are evolutionarily uninteresting (not many buzzers lurked on the plains of yore), and therefore fear of buzzers is easily extinguished. However, being conditioned to fear a more evolutionarily relevant stimulus, such as a predator, is almost impossible to extinguish because prey are evolutionarily prepared to accept this imprint.

Moreover, individuals vary in their preparedness, so some are more prone to develop phobias that may seem unreasonable in modern society. Some children develop a fear of dogs even though all a dog has ever done was barked at them. For a well-prepared survival system, this could be enough to ensure that an individual will avoid dogs forevermore.

Other primary emotions–happiness, sadness, disgust, anger–do not follow the exact path paved by fear, but the basic principles behind the fear reaction can be generalized for any of the primary emotions.

Secondary emotions, on the other hand, are not reactive but are learned emotional responses that, according to Antonio Damasio, professor and head of the Department of Neurology at University of Iowa College of Medicine, develop over the course of a lifetime. The list of secondary emotions comprises all the subtle gradations of the primary emotions: ennui, interest, irritation, euphoria, and so on. The stimuli that lead to a secondary emotional reaction are not immediately life-threatening, and so instead of prompting a swift reaction, these stimuli involve a longer, more complex reaction.

Secondary Emotion

Secondary emotion is different from primary emotion in that it begins with cognition and follows a pathway that has been created by learning; images are associated with emotions, and events triggering these images then trigger the pre-associated emotions. Neurologically, secondary emotions follow pathways slightly different from those of primary emotions: stimulus processing begins in the frontal lobe and only then travels to our friend the amygdala to complete the emotional circuit.

An experience of the secondary emotion kind would go something like the following. You’re sitting in a lecture hall, notebook open, pen in hand. After a little while, you evaluate the situation. The professor, propped up behind the lectern, is droning on. You try to pay attention, but your frank cognitive assessment is: bo-o-oring. In the process of deciding so, related images from various parts of the brain (visual, auditory, and so on) float about this particularly dull professor, other tedious lectures, or your involvement (or lack thereof) in the subject matter.

These images do not escape the notice of the prefrontal cortex; here the relation of these images to similar situations and the emotions usually evoked by these situations is recognized. The amygdala and anterior cingulate are notified. At this point, these regions signal the viscera (guts, etc.), skeletal muscles, and endocrine and peptide systems (involved in the release of hormones) that an event similar to the events that generated Response X is currently transpiring. The body amiably recreates Response X–in this case, a slide into stupor–and sends the All Systems Go signal back to the brain. The brain duly notes the fact that the body is showing signs of boredom.

The amygdala and anterior cingulate also activate the brain stem and basal forebrain to release chemicals to the basal ganglia and cerebral cortex, so that, in parallel to the bodily reaction, the style and efficiency of the cognitive process is affected. Thus not only is the body state sending a signal–”Hello, we’re having an emotional moment here!”–the very way you’re thinking adds emphasis and information about the type of emotion you’re feeling. In the lecture hall, then, your thinking begins to slow and the vines of torpor slowly twine about brain and body until you are dozing through yet another class.

The Evolution of Secondary Emotions
Secondary emotion may not seem evolutionarily adaptive, but it is. Secondary emotions help the brain associate good and bad consequences with events more subtle than, for instance, being confronted by a predator. A lizard would have no particular reaction to the presentation style of a lecturer, but a human could use the information about the lecture to make some choices: read a comic book, declare a different major, catch up on much-needed sleep. Boredom spurs you to try something new, which could lead to new and improved methods of accomplishing a task–which could lead to greater choices in–and therefore chances of–survival, which is, of course, evolutionarily adaptive.

Thus secondary emotions help us retain sophisticated information about subtle events in our complex lives. This information helps us make everyday decisions, which is most strikingly illustrated by observations of and experiments with patients with frontal lobe damage.

Egad. My Frontal Lobe Is Missing
Patients with certain types of frontal lobe damage (including surgical removal) do not experience secondary emotions. However, frontal lobe patients do react to stimuli that engage the primary emotions, as shown by studies undertaken by Damasio and Daniel Tranel, a psycho-physiologist and experimental neuropsychologist at the University of Iowa College of Medicine. First, in order to get an objective measure of reactivity, two electrodes were hooked up to subjects’ skin to measure the conductivity of a small charge over the skin’s surface. Because emotion produces a degree of moisture, the amount of interference in the electrical conductivity easily measures the occurrence of an emotional reaction. A sudden sound was then made near the subject. Frontal lobe patients had the same startled fear reaction as subjects without brain damage. Even though the frontal lobe is damaged, the rest of the brain–including the amygdala and brain stem–is undamaged; therefore there is no obstacle to primary emotion. (As you’d expect, patients with amygdala damage did not show a fear reaction in this situation.)

However, when frontal lobe patients are put in a situation requiring thought about a situation–in other words, in a situation where secondary emotions rather than primary emotions would come into play–a marked difference between frontal lobe patients and the control group appears. Frontal lobe patients and a control group, again hooked up to conductance-measuring electrodes, were given the task of watching and remembering a long series of slides, some of which contained emotion-provoking content, most of which were neutral. Viewing emotion-producing slides produced a measurable response in the control group of non-brain-damaged people, but no response in frontal-lobe patients, even though they recalled the content of the slides without a problem. Frontal-lobe patients sometimes know intellectually that they should feel a reaction, but the reaction just is not there to feel.

Although the frontal lobe patients remembered the slides clearly, the damage to (or lack of damage to) the frontal lobe rendered it incapable of calling on the amygdala et al to set to work on the body and brain; therefore these people had no reaction to refer to and interpret as emotion. This missing link drastically and negatively affects frontal lobe patients’ ability to make decisions; because their secondary emotions are not engaged in evaluating the consequences of the numerous choices available when confronted with a decision (even something simple as choosing between making a lunch date on Tuesday or Wednesday), their cognitive processes run in circles as all of the pros and cons of each choice are laboriously listed and discussed. Ultimately, no decision is made until someone–the impatient other half of the lunch date, perhaps–intervenes.

Intuition: Thinking through Your Gut
Intuition is the most subtle result of secondary emotion, and a power that frontal lobe patients lack. When secondary emotion leaves its somatic markers on your brain’s encoding of events, your body reaction can become intuitively associated with that type of situation. Thus, in a similar situation, you may not even need to think about a decision but would make the intuitive connection. For instance, when you meet someone you like, your brain encodes the look in their eyes, the way they respond to you, their energy, and their pheromones as a positive somatic marker. The next time you meet someone who feels similar, you instinctively know you are going to like this person. Your brain has sensed the somatic marker applied to this type of situation and applied your body’s knowledge without having to think about it; your gut feeling, your intuition, tells you that this person can be trusted.

Three Types of Emotion
Damasio proposes a third type of emotion: background feeling. Background feeling is your emotional resting state, your emotional homeostasis. It is what you experience most often, what you feel in between bursts of happiness and anger, interest and despondency. Made up of a general monitoring of the body, background emotion hums along quietly, like a small power generator monitoring the condition of your body and brain as you go about your business. When the generator sings out or groans, reflecting a change in your visceral and/or musculoskeletal state, you become immediately aware of the change and experience a primary or secondary emotion.

Primary and secondary emotions involve expenditure of energy in bringing you away from your usual levels of existence, your background feeling. Thus primary and secondary emotions get your attention, but by the same token, you can’t always be in a state of ecstasy; you need that energy to live your life.

A Feeling of Conclusion
If we were only emotional lizards responding to danger, our lives would be so much less complex–and much less rich. The evolutionary cultivation of secondary and background emotions has allowed us to create the sophisticated–sometimes confusing, often exhilarating–lives we lead today. Now danger can be defined as anything from a tornado to a dead-end job–and that is what motivates us to keep pushing ourselves and our horizons. Our continual striving leads, in turn, to increasingly sophisticated (and confusing and exhilarating) lives.

We pay the price, of course. Not only can we use our emotional and cognitive understanding of danger to avoid it, we are also doomed to worry about which survival plan is the correct plan, whether the plan we choose will succeed, what other dangers are out there that we haven’t planned for, and so on. Not only do we emotional sophisticates have better chances for survival and more interesting lives for which to survive, we also have worry and stress. Aren’t we lucky?

We are.

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