Emotions

Can anyone tell me what emotions are?

Discussion: Do you think it is important to be able to recognize other people’s emotions? Why? Suppose that you could no longer recognize people’s facial expressions of emotions. What consequences would that loss have for you?

I. General Overview

An emotional response consists of three types of components: behavioral, autonomic, and hormonal (controlled by the amygdala).

1. The behavioral component consists of muscular movements that are appropriate to the situation that elicits them.

2. Autonomic responses facilitate the behaviors and provide quick mobilization of energy for vigorous movement.

3. 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.

FEARThe amygdala plays a special role in physiological and behavioral reactions to objects and

situations that have biological significance, such as those that warn of pain or other unpleasant consequences or signify the presence of food, water, salt, potential mates or rivals, or infants in need of care.

We need concern ourselves with just three major regions: the lateral nucleus, the basal nucleus, and the central nucleus.

The lateral nucleus (LA) receives 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 (a brain region involved in the effects of reinforcing stimuli on learning) and the dorsomedial nucleus of the thalamus, whose projection region is the prefrontal cortex. The LA and B nuclei send information to the ventromedial prefrontal cortex and the central nucleus (CE), which projects to regions of the hypothalamus, midbrain,

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pons, and medulla that are responsible for the expression of the various components of emotional responses.

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.

Animals:After the central nucleus has been destroyed, animals no longer show signs of fear when

confronted with stimuli that have been paired with aversive events. They 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 stress-induced illnesses (Coover, Murison, and Jellestad, 1992; Davis, 1992; LeDoux, 1992).

Normal monkeys show signs of fear when they see a snake, but those with amygdala lesions do not (Amaral, 2003). 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 (Davis, 1992), and long-term stimulation of the central nucleus produces stress-induced illnesses such as gastric ulcers (Henke, 1982).

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Humans: White, 1940; Halgren et al.,1978; Gloor et al., 1982: stimulation of parts of the brain

(the hypothalamus) produced autonomic responses that are often associated with fear and anxiety but only when the amygdala was stimulated did people also report that they actually felt afraid.

Bechara et al. (1995) and LaBar et al. (1995): people with lesions of the amygdala showed impaired acquisition of a conditioned emotional response.

Gosselin et al. (2005): patients with damage to the amygdala showed no trouble with musical perception but were unable to recognize scary music.

ANGER, AGGRESSION, AND IMPULSE CONTROLAggressive behavior: threat behaviors, which consist of postures or gestures that warn the

adversary to leave or it will become the target of an attack.The threatened animal might show defensive behaviors—threat behaviors or an actual

attack against the animal that is threatening it—or it might show submissive behaviors—behaviors that indicate that it accepts defeat and will not challenge the other animal.

Predation is the attack of a member of one species on a member of another, usually because the latter serves as food for the former.

But what actually triggers aggression in humans?What are the factors to be considered?

a) Heredity: Viding studied a group of same-sex twins at the ages of 7 years and 9 years and found a higher correlation between monozygotic twins than dizygotic twins on measures of antisocial behavior and levels of callous, unemotional behavior.

b) Serotonin: Lidberg et al., 1984, 1985; Virkkunen et al.,1989 - a depressed rate of serotonin release (indicated by low levels of 5-HIAA in the CSF) is associated with aggression and other forms of antisocial behavior (including assault, arson, murder, and child beating).

c) Ventromedial Prefrontal Cortex : i. Bechara (2000) – patients with bilateral lesions of the vmPFC: severe impairments in personal and social decision-making.

i. patients with vmPFC lesions: defects both in emotional response and emotion regulation (emotional responsivity diminished, reduced social emotions such as compassion, shame and guilt).

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ii. patients with focal lesions in the vmPFC: personality changes such as lack of empathy, irresponsibility, and poor decision making.

II. Communication of Emotions Facial Expression of Emotions: Innate ResponsesCharles Darwin (1872/1965) suggested that human expressions of emotion have evolved from 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. Research by Ekman and his colleagues (Ekman and Friesen, 1971; Ekman, 1980) tends to confirm Darwin’s hypothesis that facial expression of emotion uses an innate, species-typical repertoire of movements of facial muscles (Darwin, 1872/1965). For example, Ekman and Friesen (1971) studied the ability of members of an isolated tribe in New Guinea to recognize facial expressions of emotion produced by Westerners.

Neural Basis of the Communication of Emotions: RecognitionLATERALITY

We recognize other people’s feelings by means of vision and audition—seeing their facial expressions and hearing their tone of voice and choice of words. Many studies have found that the right hemisphere plays a more important role than the left hemisphere in comprehension of emotion.

Several functional-imaging studies have confirmed these results. For example, George et al. (1996) had subjects listen to some sentences and identify their emotional content. In one condition the subjects listened to the meaning of the words and said whether they described a situation in which someone would be happy, sad, angry, or neutral. In another condition the subjects judged the emotional state from the tone of the voice. The investigators found that comprehension of emotion from word meaning increased the activity of the prefrontal cortex bilaterally, the left more than the right. Comprehension of emotion from tone of voice increased the activity of only the right prefrontal cortex.

Role of The Amygdala And Prefrontal Cortex

Lesions of the amygdala impair people’s ability to recognize facial expressions of emotion, especially expressions of fear.

By taking out all low spatial frequency information from the faces, you end up with the pictures in the middle column below. These faces would be detected easily by

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the parvocellular pathway, but not by the magnocellular or the retinotectal pathways. Conversely, the low spatial frequency faces in the right column contain less information than the normal faces in the left column – and this is entirely the parvocellular pathway’s loss. The magnocellular and retinotectal pathways are presumably coded in such coarse resolution that they cannot discriminate between the faces in the left and right columns.

Vuilleumier et al (2003) used fMRI to investigate the neural responses to the three types of faces (normal, high spatial frequency, low spatial frequency), which were either neutral or fearful. The participants were asked to judge the gender of the faces, but this was mainly to keep their attention on the faces, which were presented in random order. The researcher hypothesised that areas in the ventral visual cortex (ie the fusiform face area) would be sensitive to the high spatial frequency faces, while the amygdala would be sensitive to the low spatial frequency faces.

This latter hypothesis is based on the idea that there is a kind of shortcut in the brain to enable potentially dangerous stimuli such as fearful faces to get to the amygdala as quickly as possible, where the fear response is produced that then guides the response (fight/flee etc).

Vuilleumier et al (2003) found ample support for both hypotheses – across neutral and fearful expressions, the fusiform face area responded more strongly to the high spatial frequency faces than the low spatial frequency faces, while the opposite was true of the amygdala.

To further the evidence for low spatial frequency coding in the amygdala, Vuilleumier et al (2003) also showed that the amygdala only responded to fearful faces (as compared to neutral faces) when the faces were presented at low spatial frequency. No significant difference appeared for the high spatial frequency comparison between fearful and neutral faces. Better yet, the same activation patterns appeared for a part of the thalamus corresponding to the pulvinar and the superior colliculus, which, as you may recall, was hypothesised to be part of the retinotectal pathway that enables the amygdala response. The figure below gives the mean activity across the conditions for the amygdala (d), and the pulvinar-colliculus area (e).

III. Feelings of Emotions1.1. The James-Lange Theory

William James (1842–1910), an American psychologist, and Carl Lange (1834–1900), a Danish physiologist, independently suggested similar explanations for emotion, which most people refer to collectively as the James-Lange theory ( James, 1884; Lange, 1887).

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Basically, the theory states that emotion-producing situations elicit an appropriate set of physiological responses, such as trembling, sweating, and increased heart rate. The situations also elicit behaviors, such as clenching of the fists or fighting. The brain receives sensory feedback from the muscles and from the organs that produce these responses, and it is this feedback that constitutes our feeling of emotion.

James said that our own emotional feelings are based on what we find ourselves doing and on the sensory feedback we receive from the activity of our muscles and internal organs. For example, when we find ourselves trembling and feel queasy, we experience fear. Where feelings of emotions are concerned, we are selfobservers. Thus, the two aspects of emotions reported in the first two sections of this chapter give rise to the third: feelings.

James’s theory is difficult to verify experimentally because it attempts to explain feelings of emotion, not the causes of emotional responses, and feelings are private events. Some anecdotal evidence supports the theory. For example, Sweet (1966) reported the case of a man in whom some sympathetic nerves were severed on one side of the body to treat a cardiovascular disorder. The man— a music lover—reported that the shivering sensation he felt while listening to music now occurred only on the unoperated side of his body. He still enjoyed listening to music, but the surgery had altered his emotional reaction.

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