+ biopsychology of stress- part1

   This text is a summary of 17th part of the book "biopsychology" writen by John P. J. Pinel and translated into persian (Farsi) By A.R Fazeli, student of psychology courses in Imam Qomeini institute for education and research as a work of phsiologic psychology class by M.K Khoda Panahi PhD


     1.     Early Research on the Biopsychology of Emotion
          a.  Darwin
          b.  James-Lange and Cannon-Bard Theories
          c.  Sham Rage, the Limbic System, and Kulver-Bucy Syndrome
     2.     Human Facial Expressions of Emotion
          a.     The Primary Facial Expressions
          b.     Facial Feedback Hypothesis
          c.     Deceptive Facial Expressions
     3.     Cortical Mechanisms of Emotion
     4.     Fear, Defense, and Aggression
     5.     Neural Mechanisms of Fear and Conditioned Fear

1.     Early Research on the Biopsychology of Emotion

a.  Darwin

-     Darwin's The Expression of Emotions in Man and Animals was the first major event in the study of the biopsychological bases of emotion.

-     Darwin believed that emotions evolved from behaviors that indicated what an animal would do next in a given situation; that when these behaviors were advantageous to the animal (e.g., allowed it to avoid a fight), they evolved in a way that would enhance their communicative value, to the extent that the original behavior was lost; and that opposite messages are signalled by opposite types of behaviors (the principle of antithesis, use Digital Image Archive Figure CH17F01.BMP)

b. James-Lange and Cannon-Bard Theories of Emotion (use Digital Image Archive Figure CH17F02.BMP)

-     the James-Lange theory was the first attempt to explain the physiological bases of emotion; in their theory, James and Lange suggested that emotion-inducing stimuli are received and interpreted by the brain, which triggers visceral changes that subsequently trigger the experience of emotion.

-     Cannon, and subsequently Bard, proposed an alternative theory based on the idea that emotional stimuli evoke a viseral and an emotional response response that were independent of one another

-     it appears that neither theory was entirely correct; emotions can be induced by stimuli that cannot elicit a peripheral, visceral response (e.g., in patients suffering from a spinal cord transection), but visceral responses can often induce an emotional state in the absence of any obvious eliciting stimuli (e.g., a racing heartbeat and increased respiration can produce a feeling of fear in the absence of an eliciting stimuli).

c.  Sham Rage, the Limbic System, and the Kulver-Bucy Syndrome

-     in 1929, Bard reported that cats that had been decorticated (their cerebral cortex was removed) responded with unusual aggression to the slightest provocation; often, this behavior was not even directed at any specific topic.  Bard concluded that the hypothalamus is critical for the performance of aggressive behaviors, and that the cortex normally inhibited and directed these aggressive displays.

-     this theory of hypothalamic function was followed by Papez's proposal of a limbic system (use Digital Image Archive Figure CH17F03.BMP) that controlled the expression of emotions by connections with the hypothalamus and mediated the perception of emotions by connections with the cortex.

-     this idea was supported in part by the observation that damage to a part of the limbic system…specifically, to the amygdala, would produce a syndrome in which a subject was fearless, hypersexual, and inclined to explore objects with their mouths.  This was called the Kluver-Bucy syndrome, after the investigators who first reported it

2.     Human Facial Expressions of Emotion

a.     The Primary Facial Expressions

-     much of the classic research on human facial expressions has been conducted by Ekman and Friesen beginning in the 1970s; they began by analyzing hundreds of films and photographs of people experiencing various emotions; they concluded that there are six primary facial expressions of emotion and that all other expressions were mixtures of these; the six primary expressions were expressions of: (1) anger, (2) fear, (3) happiness, (4) surprise, (5) sadness, and (6) disgust

-     Darwin had earlier proposed that facial expressions are universal to the human species; this hypothesis was tested by showing people from 12 different cultures facial expressions from Ekman and Friesen's atlas; the photographs were of people who had been instructed to contract specific facial muscles (e.g., to make a surprised expression, the models were instructed to pull their eyebrows upward so as to wrinkle their forehead, to open their eyes wide to reveal white above the iris, to slacken the muscles around the mouth, and to drop the jaw)

-     the people from all 12 cultures linked the same emotions to the facial expressions, thus supporting Darwin's hypothesis.  In addition, Ekman and Friesen found that isolated New Guinea tribe members could correctly identify Western facial expressions and that Westerners could correctly identify New Guinean expressions, further supporting the idea of the universality of emotions
b.     Facial Feedback Hypothesis of Emotions

-     recall that, according to the James-Lange theory of emotion, the body first produces a visceral, peripheral response to emotional stimuli, and then the feeling of emotion comes from the body's perception of its own reactions; although it is now clear that feedback from the body's reactions is not necessary to feel emotion, the question remains, "Can the expression of emotion influence the feeling of emotion?"

-     one version of this hypothesis focuses on the idea that facial expression can influence emotional experience.  This is called the facial feedback hypothesis; Can putting on a happy face make you feel better?

-     the answer seems to be yes; Rutledge and Hupka (1985) asked subjects to hold various facial poses while they viewed slides; the subjects reported slightly more happy when making happy faces, and slightly more angry when making angry faces

-     try this: pull your eyebrows down and together, raise your upper eyelids, tighten your lower eyelids, narrow your lips and press them together; if holding this expression of anger makes you feel slightly uneasy you have experienced the facial feedback hypothesis

c.     Deceptive Facial Expressions

-     because we can exert voluntary control over the facial muscles, we can inhibit true facial expressions and substitute false ones; there are positive and negative reasons for this

-     it is difficult to fool an expert because microexpressions of the genuine emotion often break through the false one; although they are usually very short (about .05 seconds), they can often be spotted by an expert even without slow-motion analysis

-     also, there tend to be subtle differences between genuine and false expressions that can be recognized by an expert; for example, Duchenne a French neuroanatomist pointed out in 1862 that genuine smiles (which have been known as Duchenne smiles) involve contraction of both the zygomaticus major and orbicularis oculi, whereas false smiles involve only the zygomaticus major

3.     Cortical Mechanisms of Emotion

-     in general, the prefrontal cortex is associated with emotions; recall that prefrontal lobotomy produced a general emotional blunting.  In addition, the right hemisphere seems to be more involved with emotion than the left hemisphere: right hemisphere lesions tend to disrupt the perception of facial expression and the emotional tone of speech (prosody) more than left hemisphere lesions

-     Kolb and his colleagues (1988) found that frontal lobe lesions, regardless of side, resulted in fewer facial expressions

4.     Fear, Defense and Aggression

-     fear is the emotional reaction to threat; defensive behaviors are intended to protect an animal from threat, while aggressive behaviors are intended to threaten or harm.

-     ethoexperimental research on emotional expression in nonhuman species has focused on aggression and defense, primarily in rats

-     two important concepts have emerged from this study:
               (1) neither aggression or defense are unitary concepts; there are different kinds of aggression and defense, which occur in different situations, have a different topography, and have a different neural basis;
               (2) many of the complexities of aggressive and defensive behavior can be understood in terms of the concept of target sites, the idea that different kinds of aggression tend to be directed at particular sites on the defender's body and that various defensive maneuvers appear to be specifically designed to protect these sites

-     social aggression is unprovoked aggression against a conspecific for the purpose of establishing, maintaining, or altering a social hierarchy; in many mammals it occurs only among males; unlike other forms of aggression, it is dependent on testosterone in many species

-     the Blanchard's have fruitfully studied social aggression using the colony-intruder model; a small male intruder is placed in an established colony, and the interaction between the intruder and the alpha male is studied

-      social aggression by the alpha male is characterized by piloerection, lateral attack, bites directed at the back near the base of the tail, and movements that get the alpha male in position to deliver such bites; the alpha male will not bite any other part of the intruder

-     the defensive behavior that is displayed by the intruder includes flight, freezing when cornered, boxing and pivoting to keep the alpha male away from its back, lying on its back, and, when pressed, defensive attack (a lunging biting attack directed at the alpha male's head)

-     the discovery that aggressive and defensive behaviors occur in a variety of stereotypical, species-specific  forms allowed a more clear understanding of the neural bases for these behaviors; for example, the lateral septum was once thought to inhibit all aggression because lesions there rendered laboratory rats very difficult to handle; we now know that these lesions actually increase defensive reactivity and predatory aggression while they decrease social aggression.

5.     Neural Mechanisms of Fear and Conditioned Fear

-     three lines of evidence implicate the amygdala as playing a key role in the experience and expression of fear.  This evidence has all arisen out of the study of conditioned fear.  In one example of this type of study, the subject (usually a rat) hears a tone that signals a mild electric shock.  After several pairings, the tone elicits defensive behaviors and autonomic responses associated with the shock itself.  LeDoux and his colleagues have mapped the neural systems that underlie this form of auditory fear conditioning

-     LeDoux found that lesions to the medial geniculate nucleus of the thalamus blocked fear conditioning, but lesions to primary auditory cortex did not.  This suggested that an alternate neural structure was involved in the fear conditioning; this turned out to be the amygdala, as lesions there also blocked the auditory fear conditioning.  Pathways from the amygdala to the periaqueductal gray have been found to mediate many defensive behaviors; pathways to the lateral hypothalamus elicit the appropriate sympathetic responses.

-      interestingly, there is a second pathway from the medial geniculate nucleus of the thalamus to the amygdala that passes through primary auditory cortex; if either the direct or the indirect route is intact, fear conditioning can occur.
Suggested Websites for Lecture 17a:

The Emotional Brain:

          From the Los Angeles Times's The Brain site, a review on new imaging techniques and the neural substrates of emotion; good text, though sadly no figures.

     The Limbic System:

          From the Brain and Mind site, a review of the limbic system and its role in emotion.

Neural Bases of Fear:

          Fear and the limbic system, from Washington University's Neuroscience tutorial page.  You will have to scroll down the page to find this section; brief text, good figures.



نویسنده : S.Hani M.M ; ساعت ۱٢:٥۸ ‎ق.ظ ; دوشنبه ٩ خرداد ،۱۳۸٤
تگ ها: biopsychology و stress
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