Chapter 12Chapter 12

The Biology of Emotion and Stress

Defining EmotionDefining Emotion

Emotion - A feeling that differs from a person’s normal affective state; a biological function of the nervous system.

Emotions have three central attributes:• A change in physiological arousal, ranging

from slight to intense.• An affective response, which may be

pleasant or unpleasant.• The capacity to motivate a specific behavior

FBI: Universal Facial FBI: Universal Facial ExpressionsExpressions

FacialFacialExpressionsExpressions

Say “Cheese”Say “Cheese”

Experiencing an Experiencing an Emotion: Emotion: James-Lange TheoryThe view that the physiological changes

that occur in response to an event determine the experience of an emotion.• Physiological changes occur before the

emotional feeling• We interpret physiological changes to

determine how we feel, or how we experience an emotion.

• The different visceral and somatic responses allow us to experience different emotions.

Experiencing an Experiencing an Emotion: Emotion: Cannon-Bard TheoryThe view that an event activates the

thalamus, which stimulates the cerebral cortex to produce the feeling component of the emotion and, at the same time, the rest of the body to produce the expression of the emotion.• The emotional expression and experience

take place simultaneously by way of thalamic stimulation.

• Visceral changes, somatic changes, and the emotional experience occur at the same time.

Experiencing an Emotion: Experiencing an Emotion: Papez & MacLean -The Limbic System Emotional expression and experience are

mediated by a system of interconnected forebrain structures known as the Papez circuit

Emotional expression occurs through the hypothalamus.

The cingulate gyrus - the neural area responsible for emotional experience.

Three separate circuits in the limbic system; include the amygdala, hippocampus, cingulate gyrus, septum, hypothalamus, and thalamus.

Experiencing an Emotion: Experiencing an Emotion: Schachter’s Cognitive ModelThe view that if unable to identify the

cause of physiological arousal, a person will attribute it to environmental conditions.

It is possible to misattribute arousal to the environment when, in reality, something else is responsible.

A stimulus causes arousal, and our emotional feeling depends on how we label the stimulus.

Primary and Secondary Primary and Secondary EmotionsEmotionsAntonio Damasio

• Primary emotions - Innate, built-in, hardwired emotions; processed by the limbic system, particularly the amygdala.

• Secondary emotions -The experience of an emotion, the feeling of it, and learning is involved; processed not only by the limbic system, but also the prefrontal areas and somatosensory cortices.

Robert Plutchik

Emotions and Aggressive Emotions and Aggressive BehaviorBehaviorAggression - A behavior motivated by

the intent to harm a living being or an inanimate object.• Determining intent can be difficult.• Many different behaviors can be

considered aggressive and aggression can occur in a variety of situations.

• Therefore, there seem to be different types of aggression with different neurological bases.

Moyer identified eight types of aggression:

Irritable AggressionIrritable Aggression

An attack on almost anything without making attempts to escape.

• Most prevalent, and most studied, form of human aggression.

• Includes pain-elicited aggression - aggression triggered by a physically or psychologically painful injury.

• In its mild form, irritable aggression may involve an overt display of annoyance.

• In extreme cases, it may involve destructive, uncontrollable rage.

Irritable Aggression:Irritable Aggression:Neural Influences

Klüver-Bucy syndrome - A disorder produced by bilateral temporal lobectomy

In research, aggression has been associated with:

Intense temporal lobe activity Decreased activity in the prefrontal cortex Atrophy of the amygdala

Abnormal EEG activity has been associated with violence, particularly in the temporal lobes.

Irritable Aggression and Irritable Aggression and DiseaseDiseaseSome diseases have been

associated with aggressive behavior:• Brain tumors, particularly in the

temporal lobes• Epilepsy• Huntington’s• Viral encephalitis

Charles Whitman

Hormonal Influences on Hormonal Influences on Irritable AggressionIrritable Aggression

• Testosterone level is high in groups with heightened aggression.

• The elimination of testosterone reduces displays of aggression.

• Testosterone administration reinstates the antisocial behavior of castrated males.

• Lower progesterone may increase irritable aggression in women

• Evidence has shown that testosterone affects aggression:

Serotonin and Irritable Serotonin and Irritable AggressionAggression

Research indicates that low serotonin levels are associated with male aggression in both humans and nonhuman primates.

Fear-Induced AggressionFear-Induced AggressionAn aggressive behavior that is a

defensive reaction occurring only when the organism feels threatened and perceives escape to be impossible.• Fear motivates attempts to escape and, if

escape fails, aggression often arises. • This aggressive behavior continues until

the aversive event ends or the animal is no longer able to fight.

Fear-Induced Aggression: Fear-Induced Aggression: Neural Influences Brain abnormalities associated with fear-

induced aggression include:• Lesions of either the anterior third of the

temporal lobe or the prefrontal cortex severely disrupts fear-induced aggression in rhesus monkeys.

• Destruction of the amygdala in rats made them fearless.

• Humans with bilateral damage to the amygdala have difficulty in recognizing fear from facial expressions. However, they can recognize emotional components of speech.

What was that bang?

Smells like gunpowder. Oh look – fireworks!

Startled

AcetylcholineCortisol

The Genetics of The Genetics of AggressionAggression

Researchers can breed mice that are either extremely aggressive or unaggressive.

They have bred mice that lack the gene that codes for one type of MAO, resulting in the animals having elevated brain levels of serotonin, norepinephrine, and dopamine.

Such knock-out mice exhibit aggressive behavior similar to that seen in human males lacking the same form of MAO

The Genetics of The Genetics of AggressionAggressionConversely, mice lacking the serotonin

transporter mechanism showed a reduction in aggressive behavior relative to normal mice.

Nitric oxide (NO) has also been implicated in aggressive behavior in mice. Mice lacking a form of the enzyme nitric oxide synthase, necessary for the synthesis of NO, exhibit extremely aggressive behavior relative to wild-type mice.