Biopsychology of Emotion
Biopsychology of Emotion
Pinel, J. P. (2010). Biopsychology, 8th Edition [VitalSource Bookshelf version]. Retrieved from http://online.vitalsource.com/books/9781269533744
7 Biopsychology of Emotion, Stress, and Health Fear, the Dark Side of Emotion
17.1 Biopsychology of Emotion: Introduction
17.2 Fear, Defense, and Aggression
17.3 Neural Mechanisms of Fear Conditioning
17.4 Stress and Health Biopsychology of Emotion
17.5 Brain Mechanisms of Human Emotion
This chapter about the biopsychology of emotion, stress, and health begins with a historical introduction to the biopsychology of emotion and then focuses in the next two sections on the dark end of the emotional spectrum: fear. Biopsychological research on emotions has concentrated on fear not because biopsy-chologists are a scary bunch, but because fear has three important qualities: It is the easiest emotion to infer from behavior in various species; it plays an important adaptive function in motivating the avoidance of threatening situations; and chronic fear induces stress. In the final two sections of the chapter, you will learn how stress increases susceptibility to illness and how some brain structures have been implicated in human emotion.
17.1 Biopsychology of Emotion: Introduction
To introduce the biopsychology of emotion, this section reviews several classic early discoveries and then discusses the role of the autonomic nervous system in emotional experience and the facial expression of emotion.
Early Landmarks in the Biopsychological Investigation of Emotion
This subsection describes, in chronological sequence, six early landmarks in the biopsychological investigation of emotion. It begins with the 1848 case of Phineas Gage.
The Mind-Blowing Case of Phineas Gage
In 1848, Phineas Gage, a 25-year-old construction foreman for the Rutland and Burlington Railroad, was the victim of a tragic accident. In order to lay new tracks, the terrain had to be leveled, and Gage was in charge of the blasting. His task involved drilling holes in the rock, pouring some gun powder into each hole, covering it with sand, and tamping the material down with a large tamping iron before detonating it with a fuse. On the fateful day, the gunpowder exploded while Gage was tamping it, launching the 3-cm-thick, 90-cm-long tamping iron through his face, skull, and brain and out the other side.
Amazingly, Gage survived his accident, but he survived it a changed man. Before the accident, Gage had been a responsible, intelligent, socially well-adapted person, who was well liked by his friends and fellow workers. Once recovered, he appeared to be as able-bodied and intellectually capable as before, but his personality and emotional life had totally changed. Formerly a religious, respectful, reliable man, Gage became irreverent and impulsive. In particular, his abundant profanity offended many. He became so unreliable and undependable that he soon lost his job, and was never again able to hold a responsible position.
Gage became itinerant, roaming the country for a dozen years until his death in San Francisco. His bizarre accident and apparently successful recovery made headlines around the world, but his death went largely unnoticed and unacknowledged.
Gage was buried next to the offending tamping iron. Five years later, neurologist John Harlow was granted permission from Gage’s family to exhume the body and tamping iron to study them. Since then, Gage’s skull and the tamping iron have been on display in the Warren Anatomical Medical Museum at Harvard University.
FIGURE 17.1 A reconstruction of the brain injury of Phineas Gage. The damage focused on the medial prefrontal lobes. (Based on Damasio et al., 1994.)
In 1994, Damasio and her colleagues brought the power of computerized reconstruction to bear on Gage’s classic case. They began by taking an X-ray of the skull and measuring it precisely, paying particular attention to the position of the entry and exit holes. From these measurements, they reconstructed the accident and determined the likely region of Gage’s brain damage (see Figure 17.1). It was apparent that the damage to Gage’s brain affected both medial prefrontal lobes, which we now know are involved in planning and emotion (see Machado & Bachevalier, 2006; Vogt, 2005).
Darwin’s Theory of the Evolution of Emotion
The first major event in the study of the biopsychology of emotion was the publication in 1872 of Darwin’s book The Expression of Emotions in Man and Animals. In it, Darwin argued, largely on the basis of anecdotal evidence, that particular emotional responses, such as human facial expressions, tend to accompany the same emotional states in all members of a species.
Darwin believed that expressions of emotion, like other behaviors, are products of evolution; he therefore tried to understand them by comparing them in different species. From such interspecies comparisons, Darwin developed a theory of the evolution of emotional expression that was composed of three main ideas:
• Expressions of emotion evolve from behaviors that indicate what an animal is likely to do next.
• If the signals provided by such behaviors benefit the animal that displays them, they will evolve in ways that enhance their communicative function, and their original function may be lost.
• Opposite messages are often signaled by opposite movements and postures, an idea called the principle of antithesis.
Consider how Darwin’s theory accounts for the evolution of threat displays. Originally, facing one’s enemies, rising up, and exposing one’s weapons were the components of the early stages of combat. But once enemies began to recognize these behaviors as signals of impending aggression, a survival advantage accrued to attackers that could communicate their aggression most effectively and intimidate their victims without actually fighting. As a result, elaborate threat displays evolved, and actual combat declined.
To be most effective, signals of aggression and submission must be clearly distinguishable; thus, they tended to evolve in opposite directions. For example, gulls signal aggression by pointing their beaks at one another and submission by pointing their beaks away from one another; primates signal aggression by staring and submission by averting their gaze. Figure 17.2 reproduces the woodcuts Darwin used in his 1872 book to illustrate this principle of antithesis in dogs.
James-Lange and Cannon-Bard Theories
The first physiological theory of emotion was proposed independently by James and Lange in 1884. According to the James-Lange theory , emotion-inducing sensory stimuli are received and interpreted by the cortex, which triggers changes in the visceral organs via the autonomic nervous system and in the skeletal muscles via the somatic nervous system. Then, the autonomic and somatic responses trigger the experience of emotion in the brain. In effect, what the James-Lange theory did was to reverse the usual common-sense way of thinking about the causal relation between the experience of emotion and its expression. James and Lange argued that the autonomic activity and behavior that are triggered by the emotional event (e.g., rapid heartbeat and running away) produce the feeling of emotion, not vice versa.
FIGURE 17.2 Two woodcuts from Darwin’s 1872 book, The Expression of Emotions in Man and Animals, that he used to illustrate the principle of antithesis. The aggressive posture of dogs features ears forward, back up, hair up, and tail up; the submissive posture features ears back, back down, hair down, and tail down.
Around 1915, Cannon proposed an alternative to the James-Lange theory of emotion, and it was subsequently extended and promoted by Bard. According to the Cannon-Bard theory , emotional stimuli have two independent excitatory effects: They excite both the feeling of emotion in the brain and the expression of emotion in the autonomic and somatic nervous systems. That is, the Cannon-Bard theory, in contrast to the James-Lange theory, views emotional experience and emotional expression as parallel processes that have no direct causal relation.
The James-Lange and Cannon-Bard theories make different predictions about the role of feedback from autonomic and somatic nervous system activity in emotional experience. According to the James-Lange theory, emotional experience depends entirely on feedback from autonomic and somatic nervous system activity; according to the Cannon-Bard theory, emotional experience is totally independent of such feedback. Both extreme positions have proved to be incorrect. On the one hand, it seems that the autonomic and somatic feedback is not necessary for the experience of emotion: Human patients whose autonomic and somatic feedback has been largely eliminated by a broken neck are capable of a full range of emotional experiences (e.g., Lowe & Carroll, 1985). On the other hand, there have been numerous reports—some of which you will soon encounter—that autonomic and somatic responses to emotional stimuli can influence emotional experience.