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Chapter 11

Chapter 11 - Emotion.pdf

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University of Waterloo
Britt Anderson

Chapter 11 EmotionEmotion refers to positive or negative reactions to a particular situation Emotions consist of patterns of physiological changes and accompanying behaviorsor at least urges to perform these behaviors These responses are accompanied by feelings It is behavior not private experience that has consequences for survival and reproductionEmotions as Response Patternsemotional responses consists of three types of components behavioral autonomic and hormonalBehavioral component consists of muscular movements that are appropriate to the situation that elicits them Eg a dog defending its territory against an intruder first adopts an aggressive posture growls and shows its teethAutonomic responses facilitate the behaviors and provide quick mobilization of energy for vigorous movementEg the activity of the sympathetic branch increases while that of the parasympathetic branch decreases the dogs heart rate increases and changes in the size of blood vessels shunt the circulation of blood away from the digestive organs toward the muscles Hormonal responses reinforce the autonomic responses The hormones secreted by the adrenal medulla epinephrine and norepinephrinefurther 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 FearComponents are controlled by separate neural systemThe integration of the components of fear appears to be controlled by the amygdala Research With Laboratory AnimalsAmygdala plays a special role in physiological and behavioral reactions to objects and situations that have biological significanceResearchers shows that single neurons in various nuclei of the amygdala become active when emotionally relevant stimuli are presented For eg these neurons are excited by such stimuli as the sight of a device that has been used to squirt either a badtasting solution or a sweet solution into the animals mouth the sound of another animals vocalization etc The amygdala is involved in the effects of olfactory stimuli on reproductive physiology and behavior Amygdala The amygdala is located within the temporal lobes It consists of several groups of nuclei each with different inputs and outputsand with different functions The amygdala has been subdivided into approximately twelve regions each containing several subregions Focusing on three major regions the lateral nucleus the basal nucleus and the central nucleus Lateral nucleus LA a nucleus of the amygdala that receives sensory information from the neocortex thalamus and hippocampus and sends projections to the basal accessory basal and central nucleus of the amygdalareceives information from all regions of the neocortex including the ventromedial prefrontal cortex the thalamus and the hippocampal formation The lateral nucleus sends information to the basal nucleus B and to other parts of the brain including the ventral striatum and the dorsomedial nucleus of the thalamus whose projection region is the prefrontal cortex Basal nucleus B a nucleus of the amygdala that receives information from the lateral nucleus and sends projections to the ventromedial prefrontal cortex and the central nucleusThe LA and B nuclei send information to the ventromedial prefrontal cortex and the central nucleus CE which projects to regions of the hypothalamus midbrain pons and medulla that are responsible for the expression of the various components of emotional responsesCentral nucleus CE The region of the amygdala that receives information from the basal lateral and accessory basal nuclei and sends projections to a wide variety of regions in the brain involved in emotional responsesthe central nucleus elicits a variety of emotional responses behavioral autonomic and hormonal See Figure 111The 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 perceived neurons in the central nucleus become activated Damage to the central nucleus reduces or abolishes a wide range of emotional behaviors and physiological responses Animals no longer show signs of fear when confronted with stimuli that have been paired with aversive events Also act more tamely when handled by humans their blood levels of stress hormones are lower and they are less likely to develop ulcers or other forms of stressinduced illnessesNormal monkeys show signs of fear when they see a snake but those with amygdala lesions do notwhen the central amygdala is stimulated by electricity or by an injection of an excitatory amino acid the animal shows physiological and behavioral signs of fear and agitationand longterm stimulation of the central nucleus produces stressinduced illnesses such as gastric ulcers autonomic and endocrine responses controlled by the central nucleus are among those responsible for the harmful effects of longterm stress Outputs of the Central Nucleus of the Amygdala See Figure 112A few stimuli automatically activate the central nucleus of the amygdala and produce fear reactions eg loud unexpected noises the ability to learn that a particular stimulus or situation is dangerous or threatening is important Once the learning has taken place that stimulus or situation will evoke fear heart rate and blood pressure will increase the muscles will become more tense the adrenal glands will secrete epinephrine and the animal will proceed cautiously alert and ready to respondmost basic form of emotional learning is a conditioned emotional response which is produced by a neutral stimulus that has been paired with an emotion producing stimulusConditioned emotional response A classically conditioned response that occurs when a neutral stimulus is followed by an aversive stimulus usually includes autonomic behavioral and endocrine components such as changes in heart rate freezing and secretion of stressrelated hormonesClassical conditioning occurs when a neutral stimulus is regularly followed by a stimulus that automatically evokes a responseEg if a dog regularly hears a bell ring just before it receives some food that makes it salivate it will begin salivating as soon as it hears the sound of the bell
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