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The Modern Search for the Emotional Brain Began in the Late 19th Century
The Amygdala Emerged as a Critical Regulatory Site in Circuits of Emotions
Studies of Avoidance Conditioning First Implicated the Amygdala in Fear Responses
Pavlovian Conditioning Is Used Extensively to Study the Contribution of the Amygdala to Learned Fear
The Amygdala Has Been Implicated in Unconditioned (Innate) Fear in Animals
The Amygdala Is Also Important for Fear in Humans
The Amygdala Is Involved in Positive Emotions in Animals and Humans
Other Brain Areas Contribute to Emotional Processing
The Neural Correlates of Feeling Are Beginning to Be Understood
An Overall View
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Elation, compassion, sadness, fear, and anger are examples of emotions. These states have an enormous impact on our behavior. But what exactly is an emotion? Unfortunately, the term emotion is commonly and confusingly used in two ways. Sometimes it refers to physiological responses to certain kinds of stimuli; when in danger, your muscles tense and your heart pounds, and you may also feel afraid. But it also refers to conscious experiences, called feelings, that often (but not always) accompany these bodily responses. We need to consistently distinguish between these two states.
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In this chapter we use the term emotion to refer to the first of the two states: The set of physiological responses that occur more or less unconsciously when the brain detects certain challenging situations. These automatic physiological responses occur within both the brain and the body proper. In the brain they involve changes in arousal levels and in cognitive functions such as attention, memory processing, and decision strategy. In the body proper they involve endocrine, autonomic, and musculoskeletal responses (see Chapter 47). We use the term feeling to refer to the conscious experience of these somatic and cognitive changes. In a certain sense feelings are accounts our brain creates to represent the physiological phenomena generated by the emotional state.
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In sum, emotions are automatic, largely unconscious behavioral and cognitive responses triggered when the brain detects a positively or negatively charged significant stimulus. Feelings are the conscious perceptions of emotional responses.
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Emotional reactions have been conserved throughout the evolution of species. Behavioral responses that we typically call emotional responses are found in very simple organisms that may not have consciousness and thus not have feelings. A bacterial cell can detect harmful and useful chemicals and respond to these in adaptive ways. Indeed, all organisms must have such capacities to survive and thrive.
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Some stimuli—objects, animals, or situations—trigger emotions automatically, even in the absence of experience. These stimuli are said to have emotional competence. In addition, some otherwise insignificant objects and events that occur in conjunction with emotionally competent stimuli can acquire emotional significance through associative learning. Thus, whereas emotionally competent stimuli are naturally significant (eg, painful or delicious), other objects and events acquire emotional competence by their association with ...