Emotion

 

Learning Objectives

 

  1. Discuss the behavioral, autonomic, and hormonal components of an emotional response and the role of the amygdala in controlling them.
  2. Discuss the role of the orbitofrontal cortex in the analysis of social situations and the effects of damage to this region , including those produced by psychosurgery.
  3. Discuss cross-cultural studies on the expression and comprehension of emotions.
  4. Discuss the neural control of the recognition of emotional expression and comprehension of emotions.
  5. Discuss the neural control of emotional expression in normal people and people with brain damage.
  6. Discuss the James-Lange theory of feelings of emotion and evaluate relevant research.
  7. Discuss the nature, functions, and neural control of aggressive behavior.
  8. Discuss the hormonal control of intermale aggression, interfemale aggression, and maternal aggression.
  9. Discuss the effects of androgens on human aggressive behavior.

 

 

 

The word emotion can mean several things. Most of the time, it refers to positive or negative feelings that are produced by particular situations. Emotions consist of patterns of physiological responses and species-typical behaviors. Most of us use the word emotion to refer to the feelings, not to the behaviors. It is behavior, that has consequences for survival and reproduction.

 

This chapter is divided into four major sections:

  1. The patterns of behavioral and physiological responses that constitute emotions. The nature of the response patterns, their neural control, and the perception of situations that give rise to emotions; it includes a discussion of prefrontal lobotomy and other types of psychosurgery.
  2. The communication of emotions-their expression and recognition
  3. The nature of the feelings that accompany emotions.
  4. The neural and hormonal control of aggressive and defensive behaviors.

 

Emotions As Response Patterns

An emotional response consists of three types of components: behavioral, autonomic, and hormonal. The behavioral component consists of muscular movements that are appropriate to the situation that elicits them. Autonomic responses facilitate the behaviors and provide quick mobilization of energy for vigorous movement. The activity of the sympathetic branch of the autonomic nervous system increases while that of the parasympathetic branch decreases. As a consequence, heart rate increases, and changes in the size of blood vessels shunt the circulation of blood away form the digestive organs toward the muscles. Hormonal responses reinforce the autonomic responses. The hormones secreted by the adrenal medulla-epinephrine and norepinephrine-further increase blood flow to the muscles and cause nutrients stored in the muscles to be converted into glucose. In addition, the adrenal cortex secretes steroid hormones, which also help to make glucose available to the muscles.

Special behaviors that serve to communicate emotional states to other animals, such as the threat gestures that precede an actual attack and the smiles and frowns used by humans. Negative emotions receive much more attention than positive ones. Most of the research on the physiology of emotions has been confined to fear and anxiety.

 

Neural Control of Emotional Response Patterns: Role of the Amygdala

Stimulation of various parts of the brain can induce an animal to attack another one or can cause it to make vigorous attempts to escape. In other words, the stimulation can produce the behaviors associated with anger or fear. The overt behaviors, the autonomic responses, and the hormonal secretions associated with these emotional reactions are controlled by separate neural systems. The integration of these responses appears to be controlled by the amygdala.

 

Anatomy of the Amygdala

Researchers in several different laboratories have shown that single neurons in various nuclei of the amygdala become active when emotionally relevant stimuli are presented. The amygdala is involved in the effects of pheromones on reproductive physiological and behavior.

The amygdala ( or more precisely, the amygdala complex) is located within the temporal lobes. It consists of several groups of nuclei, each with different inputs and outputs-and with different functions. The major parts of the amygdala are the medial nucleus, the lateral/basolateral nuclei, the central nucleus, and the basal nucleus.

 

The medial nucleus consists of several subnuclei that receive sensory input (including information about the presence of odors and pheromones from the main and accessory olfactory bulbs) and relay the information to the medial basal forebrain and to the hypothalamus.

 

The lateral/basolateral nuclei receive sensory information from the primary sensory cortex, association cortex, thalamus, and hippocampal formation. Theses nuclei project to the ventral striatum ( a region involved in the effects of reinforcing stimuli on learning) and to the dorsomedial nucleus of the thalamus, whose projection region is the prefrontal cortex. They also provide sensory input to the central nucleus, which is the part to the amygdala that will most concern us.

 

The central nucleus projects to regions of the hypothalamus, midbrain, pons, and medulla that are responsible for the expression of the various components of emotional responses.

 

The basal nucleus consists of several subnuclei that, like the central nucleus, receive sensory input form the lateral and basolateral nuclei and relay information to other amygdala nuclei and to the periaqueductal gray matter of the midbrain.

 

The central nucleus of the amygdala is the single most important part of the brain for the expression of emotional responses provoked by aversive stimuli. When threatening stimuli are presented, both the neural activity of the central nucleus and the production of Fos protein increase. Damage to the central nucleus (or to the lateral/basolateral nuclei, which provide it with sensory information) reduces or abolishes a wide range of emotional behaviors and physiological responses. After the central nucleus id destroyed, animals no longer show signs of fear when confronted with stimuli that have been paired with aversive events. The animals blood levels of stress hormones are lower. In contrast, when the central amygdala is stimulated by means of electricity or by an injection of an excitatory amino acid, the animal shows physiological and behavioral signs of fear and agitation, and long –term stimulation of the central nucleus produces stress-induced illnesses such as gastric ulcers. These observations suggest that the autonomic and endocrine responses controlled by the central nucleus are among those responsible for the harmful effects of long-term stress.

 

Conditioned Emotional Responses

The central amygdala is particularly important for aversive emotional learning. A few stimuli automatically produce fear reactions-for example, loud unexpected noises, the approach of large animals, heights, or (for some species) specific sounds or odors. Even more important, however, is the fact that we can learn that a particular situation is dangerous or threatening.

A conditioned emotional response is produced by a neutral stimulus that has been paired with an emotion-producing stimulus.

Briefly, classical conditioning occurs when a neutral stimulus is regularly followed by a stimulus that automatically evokes a response.

If an organism learns to make a specific response that avoids contact with the aversive stimulus (or at least minimizes its painful effect), most of the nonspecific "emotional" responses will eventually disappear. If the organism learns a successful coping response- a response that terminates, avoids, or minimizes an aversive stimulus-the emotional responses will no longer occur.

 

Behavioral arrest- a species-typical defensive response called freezing.

 

They found that lesions of the lateral hypothalamus interfered with the change in blood pressure, whereas lesions of the periaqueductal gray matter interfered with the freezing response. Thus, two different mechanisms, both under the control of the central nucleus of the amygdala, are responsible for the autonomic and behavioral components of conditioned emotional responses.

Some of the effects of anxiolytic (anxiety-reducing) drugs appear to be produced through the central nucleus. The amygdala contains a high concentration of benzodiazepine receptors- especially the basolateral nucleus, which projects to the central nucleus-and the central nucleus itself contains a high concentration of opiate receptors. The infusion of either opiates or benzodiazepine tranquilizers into the amygdala decreases both the learning and the expression of conditioned emotional responses (Kapp et al., 1982; Davis, 1992a). In addition , Sanders and Shekhar found that an injection of a benzodiazepine antagonist into the basolateral nucleus blocked the anxiolytic effects of an intraperitoneal injection of chlorodiazepoxide(Librium). Thus, tranquilizers appear to exert their anxiolytic effect in the basolateral amygdala. Even after their amygdala is destroyed, benzodiazepines still have some anxiolytic effect.

Some investigators have suggested that anxiety disorders are caused by hyperactivity of the central nucleus of the amygdala, perhaps as a result of increased secretion of endogenous anxiety-producing ligands for the GABA receptor, of which the benzodiazepine receptor is a part. Whether the primary cause of the increased anxiety lies within thesecircuits or elsewhere in the brain (or in people’s environments and past histories) has yet to be determined.

The amygdala is involved in behaviors associated with another negative emotion-disgust. When an animal becomes nauseated as a result of eating tainted food the animal develops an aversion to the flavor of the last thing it ate or drank before the nausea. This form of learning is abolished by lesions of the basolateral amygdala.

 

Research with Humans

A considerable amount of evidence indicates that the amygdala is involved in emotional responses in humans. These studies found that stimulation of parts of the brain produced autonomic responses that are often associated with fear and anxiety but that only when the amygdala was stimulated did people also report that they actually felt afraid (White, 1940; Halgren et al., 1978; Gloor et al., 1982).

Lesions of the amygdala decrease people’s emotional responses. People with lesions of the amygdala showed impaired acquisition of a conditioned emotional response, just as rats do. Startle response of a man with a localized lesion of the right amygdala was not increased by the presence of an unpleasant emotion.

Damage to the amygdala interferes with the effects of emotions on memory. Normally, when people encounter events that produce a strong emotional response, they are more likely to remember these events. A patient with amygdala damage showed no such increase in memory.

Several imaging studies have shown that the human amygdala participates in emotional responses. The activity of the right amygdala increased while the subjects recalled the neutral ones. When well motivated people work on such tasks, they tend to become tense and unhappy and usually report feelings of frustration. A PET scanner showed that the blood flow in the amygdala increased while the subjects were working on the unsolvable anagrams but now when working on the solvable ones.

 

Social Judgments and Emotions: Role of the Orbitofrontal Cortex

The analysis of social situations involves much more than sensory analysis; it involves experiences and memories, inferences and judgments. But one region of the brain-the orbitofrontal cortex-plays a special role.

The orbitofrontal cortex is located at the base of the frontal lobes. It covers the part of the brain just above the orbits-the bones that form the eye sockets-hence the term orbitofrontal. The orbitofrontal cortex receives direct inputs from the dorsomedial thalamus, temporal cortex, ventral tegmental area, olfactory system, and amygdala. Its outputs go to several brain regions, including the Cingulate cortex, hippocampal formation, temporal cortex, lateral hypothalamus, and amygdala. Finally, it communicates with other regions of the frontal cortex. Thus, its inputs provide it with information about what is happening in the environment and what plans are being made by the rest of the frontal lobes, and its outputs permit it to affect a variety of behaviors and physiological responses, including emotional responses organized by the amygdala.

The fact that the orbitofrontal cortex plays an important role in emotional behavior is shown by the effects of damage to this region. Before Phineas Gage’s injury he was serious, industrious, and energetic. Afterward, he became childish, irresponsible, and thoughtless of others. He was unable to make or carry out plans, and his actions appeared to be capricious and whimsical. His accident largely destroyed the orbitofrontal cortex (Damasio et al ., 1994).

In general, damage to the orbitofrontal cortex reduced people’s inhibitions and self-concern; they became indifferent to the consequences or their actions. In addition, although they remained sensitive to noxious stimuli, the pain no longer bothered them-it no longer produced an emotional reaction.

Radical removal of the frontal loves in a human patient (performed because of a tumor) did not appear to produce intellectual impairment-thus, people could presumably get along without their frontal lobes. These two reports suggested to Moniz that "if frontal-love removal…eliminates frustrational behavior, why would it not be feasible to relieve anxiety states in man by surgical means?" in fact, Moniz persuaded a neurosurgeon to do so, and approximately one hundred operations were eventually performed under his supervision. (In 1949 Moniz received the Nobel Prize for the development of this procedure.)

Since that time, tens of thousands of people have received prefrontal lobotomies, primarily to reduce symptoms of emotional distress, and many of these people are still alive. Although patients did perform well on standard tests of intellectual ability, they showed serious changes in personality, becoming irresponsible and childish. They also lost the ability to carry out plans, and most were unemployable. And although pathological emotional reactions were eliminated, so were normal ones. Because of these findings, and because of the discovery of drugs and therapeutic methods that relieve the patients symptoms without producing such drastic side effects, neurosurgeons eventually abandoned the prefrontal lobotomy procedure (Valenstein, 1986).

A transorbital leucotome, shaped like an ice pick, was introduced into the brain by passing it beneath the upper eyelid until the point reached the orbital bone above the eye. The instrument was hit with a mallet, driving it through the bone into the brain. The end was then swept back and forth so that it cut through the white matter.

The fact that it was so easy and left no external signs other than a pair of black eyes may have tempted its practitioners to perform it too casually.

But the fact remains that the surgery did reduce people’s emotional suffering, or it would never have become so popular. Primarily, the surgery reduced anxiety, observations, and compulsions. People’s groundless fears disappeared, and they no longer felt compelled to perform rituals to ward off some (imaginary) disastrous events.

Some procedures approached the frontal lobes from the base of the brain, primarily cumin their connections with the diencephalon and temporal lobes. Other procedure approached the frontal lobes form above and disconnected the orbitofrontal cortex from the Cingulate gyrus. In either case the patients’ emotional distress was usually reduced.

What, exactly, does the orbitofrontal cortex do? One possibility is that it is involved in assessing the personal consequences of what is currently happening. People whose orbitofrontal cortex has been damaged by disease or accident are still able to accurately assess the significance of particular situations, but only in a theoretical sense. For example, Eslinger became unable to distinguish between trivial decisions and important ones, spending hours trying to decide where to have dinner but failing to use good judgment in situations that concerned his occupation and family life. Thus, it appears that the orbitofrontal cortex is not directly involved in making judgments and conclusion about events but has a role in translating these judgments not appropriate feelings and behaviors.

 

SUMMARY

The word emotion refers to behaviors, physiological responses, and feelings. This section has discussed emotional response patterns, which consist of behaviors that deal with particular situations and physiological responses (both autonomic and hormonal) that support the behaviors. The amygdala organizes behavioral, autonomic, and hormonal responses to a variety of situations, including those that produce fear, anger, or disgust. In addition, it is involved in the effects of odors and pheromones on sexual and maternal behavior. It receives inputs from the ol-factory system, the association cortex of the temporal lobe, the frontal cortex, and the rest of the limbic system. Its outputs go to the frontal cortex, hypothalamus, hippocampal formation, and brain stem nuclei that control autonomic functions and some species-typical behaviors. Damage to specific brain regions that receive these outputs will abolish particular components of emotional response patterns. Electrical recordings of single neurons in the amygdala indicate that some of them respond when the animal perceives particular stimuli with emotional significance. Stimulation of the amygdala leads to emotional responses, and it destruction disrupts them. Receptors in the amygdala are largely responsible for the anxiolytic effects of the benzodiaaepine tranquilizers and the opiates. Studies of people with amygdala lesions and PET and functional MRI studies with humans indicate that the amygdala is involved in emotional reactions in our species, too.

The orbitofrontal cortex plays an important role in emotional reactions. People with orbitofrontal lesions are able to explain the implications of complex social situations but are unable to respond appropriately when these situations concern them. Thus, this region does not appear to be necessary for making judgments about the personal significance of social situations, but it does appear to be necessary for transpersonal significance of social situations, but it does appear to be necessary for translating these judgments into actions and emotional responses. The orbitofrontal cortex, receives information from other regions of the frontal lobes, from the temporal pole, and form the amygdala and other parts of the limbic system via the mediodorsal nucleus of the thalamus. It produces emotional reactions through its connections with the amygdala and the cingulate gyrus.

Between the late 1930’s and the late 1950’s many

people received prefrontal lobotomies, which involved cutting the white matter in the ventromedial frontal lobes. Although the operations affected many parts of the frontal lobes the most important region was probably the orbitofrontal cortex. The surgery did often relieve emotional anguish and the suffering caused by pain, but it also mad people become largely indifferent to the social consequences of their own behavior and to the feelings of others, and it interfered with their ability to make and execute plans. Prefrontal lobotomies are not longer performed.

 

 

EXPRESSION AND ROCOGNITION OF EMOTIONS

Facial Expression of Emotions: Innate Responses

 

Charles Darwin (1872/1965) suggested that human expressions of emotion have evolved form similar expressions in other animals. He said that emotional expressions are innate, unlearned responses consisting of a complex set of movements, principally of the facial muscles. Thus, a human’s sneer and a wolf’s snarl are biologically determined response patterns, both controlled by innate brain mechanisms, just as coughing and sneezing are.

No matter how isolated people are, they show the same facial expressions of emotion, then these expressions must be inherited instead of learned.

Because the same facial expressions were used by people who had not previously been exposed to each other, Ekman and Friesen concluded that the expressions were unlearned behavior patterns. In contrast, different cultures use different words to express particular concepts; production of these words dos not involve innate responses but must be learned.

Thus, both the cross-cultural studies and the investigations with blind children confirm the naturalness of these expressions. Researchers have not yet determined whether other means of communicating emotions, such as tone of voice or changes in body posture, are learned or are at least partly innate.

 

Neural Basis of the Communication of Emotions: Recognition

 

 

Neural Basis of the Communication of Emotions: Expression

 

 

Summary

 

 

 

Feelings Of Emotions

 

 

The James-Lange Theory

 

 

Summary

 

 

 

AGGRESSIVE BEHAVIOR

 

 

Neural Control of Aggressive Behavior

 

 

 

Hormonal Control of Aggressive Behavior

 

Aggression in Males