The feeling being Book

Brief Review
A prominent researcher who focuses on the “emotional brain,” Joseph LeDoux contends that, contrary to the belief of some experts, there is no single emotional or “limbic” system in the brain, but different systems for different emotions. He also maintains that the fear system, in which he specializes, has two components that are not always in sync. There is the “lower” system, controlled by the amygdala in the midbrain, which is oriented toward survival and thus triggers flight or freeze or fight reactions based on a gross reading of sensory perceptions; this system is more potent than the “higher,” more finely discriminating cortical system, and sometimes overpowers it—which accounts for the persistent emotional ravages of such syndromes as PTSD and the phobias. This book is written for the layman as well as the specialist, and I recommend it to anyone interested in how the brain works.

Expanded Review

Joseph LeDoux is a psychologist who specializes in investigating the emotions. He is a protégé of Michael Gazzaniga, who in turn was a protégé of the late Roger Sperry, winner of the Nobel Prize for his work with split-brain patients (people with their cerebral hemispheres surgically separated).
Until fairly recently, emotions were neglected if not ignored by most academic psychologists—emotions did not fit neatly into the worldview of the behaviorists, who for many years dominated American psychology, while their successors, the cognitive psychologists, have tended to treat the emotions as just another form of cognition. LeDoux surveys this whole history of neglect.
Recently, though, there has been quite a lot of work on the emotions, and in particular, on what happens inside the brain during emotional states. LeDoux himself has focused on the emotion fear, because it is probably the easiest to study. Mostly he discusses how the brain produces fear and anxiety, and what the implications are for pathologies like Post-Traumatic Stress Disorder (PTSD) and the phobias. One of the keys to the fear response is Pavlovian ("classical") conditioning, in which a "learned trigger" or conditioned stimulus (CS—for example, the sound of a bell), comes (through association) to produce the same fear reaction as does a "natural trigger" or unconditioned stimulus (US—for example, an electric shock).
Based on his own work and a thorough knowledge of recent studies by other investigators, LeDoux draws the following major conclusions:

*Multiple Systems—Contrary to earlier views, different emotions appear to have different systems in the brain. Fear has one system, rage another and sex still another. There is no "limbic system" that processes all emotions.

*Evolutionary Advantages—Each emotional system has evolved to confer specific advantages related to personal survival (e.g., fear) and perpetuation of the species (e.g., sex).

*Two Systems for Fear—There are two systems that control the human fear response: the "lower" system, controlled by the amygdala, a small almond-shaped structure in the midbrain, and the "higher" system, controlled by the lateral medial area of the prefrontal cortex (this area controls "working memory"—what used to be called "short-term memory").

*Lower System Built for Speed—The lower system is more primitive than the higher, and it evolved first. It is common to all mammals and to some lower orders as well. It has one purpose: to allow the person to mobilize her resources and act quickly at any sign of danger. Sensory stimuli are routed to the amygdala, which instantly queries the longterm memory in the neighboring hippocampus ("Do these stimuli correspond with anything dangerous?"); if there is danger, the amygdala releases signals to systems that will mobilize the body to flee (if it has time) or to "freeze" (if it can't flee) or to fight (as a last resort). Some major points about this system: 1) some of its responses are apparently inherited rather than learned—for example, laboratory rats will "freeze" when encountering a snake even if they've never before seen one (or, presumably, read about one); 2) because it is vital to survival, this system can learn in "one trial"—a memory can be indelibly imprinted in the hippocampus based on just one frightening experience, so the system is highly susceptible to Pavlovian conditioning; 3) it is a "quick-and-dirty" system, that does not make fine discriminations among sensory stimuli—so it may later respond not only to the original danger stimulus but also to other, similar stimuli, and also to conditioned stimuli (stimuli that happened to be present along with the dangerous stimulus—for example, a honking horn during a mugging); and 4) its processes are completely unconscious, which allows us to react to dangerous situations before we "know" (consciously) about them—thus we react before we have to think about what’s going on (in an emergency, thinking takes too long).

*Higher System Built for Discernment—The higher system evolved more recently, and is most highly developed in the human. The system's "executive" is located in the prefrontal cortex, in the area that houses the brain's "working memory." This is the seat of consciousness, where we evaluate, compare, calculate, combine—where we do our conscious thinking. When we suddenly encounter a dangerous situation, the sensory stimuli are routed to this system, though a bit more slowly than to the lower system. The sensory stimuli are followed by perceptions of our lower system's (and therefore our body's) reaction to the situation—rapid heartbeat, quickened breathing, tensed muscles, etc. We then decide what to do based on a more comprehensive, conscious review of the situation. For example, the lower system spots a "snake" on the path, and makes the body jump back—then the higher system sees that the "snake" is actually a harmless stick, and tries to turn off the alarm and calm the body down. Points about the higher system: 1) it involves consciousness and can therefore evaluate context—the overall situation; 2) it reacts more slowly than the lower system; 3) it discriminates much more finely than the lower system; and 4) it is less powerful than the lower system (there are many more circuits leading from the amygdala to the "working memory" system than vice versa).

*Serious Problem: Decoupling of the Two Systems—The lower and higher systems do not always "talk" to each other. 1) The lower system may remember things that were below the perceptual threshold of the higher system. For example, the lower system may pick up a conditioned stimulus that the higher system is not even aware of (e.g., the honking horn during the mugging), and mobilize the body's defenses for no apparent (to consciousness) reason. Also, during very stressful situations, when the hippocampus is flooded with steroids, the higher system may fail to convert working memories into long-term memories, so that a traumatic event may be forgotten by the higher system but remembered by the lower system. The higher system may know from the body's responses (racing heart, etc.) that there's something wrong, but has no idea what. It may simply experience an anxiety attack. 2) The higher system may remember a traumatic event (for example, a bad fall), but it may also know that it is powerless to calm down the lower system's overreaction to all heights (acrophobia). This usually leads to avoidance behavior—the higher system habitually steers the person away from high places.

*Anxiety Disorders Caused by Decoupling—LeDoux makes the case that the anxiety disorders—post-traumatic stress disorder (PTSD), phobias, anxiety attacks, generalized ("free-floating") anxiety, and obsessive-compulsive disorder (OCD)—are caused by the decoupling discussed in the last paragraph, and by the consequent inability of the higher system to keep the lower system under control. The lower system hears a car backfire—this turns on a Vietnam combat memory—DANGER!—and mobilizes the body to flee, freeze or fight. The higher system remembers the Vietnam incident but can't subdue the lower system, which persists for a long time in flooding the body with danger signals. Alternatively, the lower system sees a flashbulb pop and mobilizes the body to flee, freeze or fight, but this time the higher system is unaware of the connection between the flashbulb and Vietnam—it knows only that the body and mind are beset by an all-out anxiety attack. So from the standpoint of the human being, the lower system has an upside and a downside: the upside is that it allows us to react very quickly to real dangers and to remember those dangers forever; the downside is that it tends to react too readily to similar and conditioned stimuli, to generalize to other related stimuli, to resist relearning, to fail to distinguish between the situation "back then" and the situation now—and of course it never forgets (even if the memory is "extinguished," it can be retriggered at any time by stress, even stress totally unrelated to the original trauma: for example, acrophobia “irrationally” revived by the death of a beloved grandparent).

This is an excellent book for anyone who wants to know how the brain and emotions work, or who's particularly interested in the anxiety disorders. There may be more history than you care for (the book aims at neuroscientists as well as laypeople), but the presentation is simple, with many good examples and some very useful diagrams.

Key concepts and brain areas:

Amygdala
Conditioned Response (CR)—e.g., salivation
Conditioned Stimulus (CS)—e.g., bell
Frontal Cortex—the location of the “higher” brain
Hippocampus—brain area that consolidates long-term memory
Lateral Medial Prefrontal Cortex—seat of the brain’s “executive” and “working memory”
Learned Trigger—e.g., bell
Natural Trigger—e.g., food
Unconditioned Response—e.g., salivation
Unconditioned Stimulus (US)—e.g., food