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Lec #18 emotion

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  • 1. Neuroscience: Exploring the Brain, 3e Chapter 18: Brain Mechanisms of Emotion Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 2. Introduction• Significance of Emotions – Emotional experience; Emotional expression – Study behavioral manifestations • Animal models, brain lesions – Human brain imaging techniques • Renaissance in the study of emotion • Affective neuroscience • Neural basis of emotion and mood Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 3. What Is Emotion?• Theories of Emotion – The James-Lange Theory: Emotion = Response to physiological changes in the body – The Cannon-Bard Theory: Emotions independent of emotional expression Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 4. What Is Emotion?• Unconscious Emotions – Stimulus can have emotional impact without conscious awareness • Aversive conditioning to masked stimulus results in increased skin conductance • Increased activity in the amygdala – Many ways to process emotional information Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 5. The Limbic System Concept• Broca’s Limbic Lobe – Cortex forming a ring around corpus callosum: Cingulate gyrus, medial surface temporal lobe, hippocampus Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 6. The Limbic System Concept• The Papez Circuit – Limbic structures, including cortex, are involved in emotion. – Emotional system on the medial wall of the brain linking cortex with hypothalamus Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 7. The Limbic System Concept• The Papez Circuit – Cortex: Emotional experience – Hippocampus: Hypothesized to mediate behavioral expression of emotion • Rabies infection: Hyperemotional responses -cytological changes in hippocampal neurons - Anterior thalamus • Lesions lead to spontaneous laughing, crying – Paul MacLean popularized term “limbic system” • Evolution of limbic system allows animals to experience and express emotions beyond stereotyped brain stem behaviors Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 8. The Limbic System Concept• Difficulties with the Single Emotion System Concept – Diverse emotions – Many structures involved in emotion • No one-to-one relationship between structure and function – Limbic system: Utility of single, discrete emotion system questionable Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 9. The Limbic System Concept• The Klüver-Bucy Syndrome – Temporal lobectomy in rhesus monkeys • Decreased fear and aggression • Decreased vocalizations and facial expressions – Temporal lobectomy in humans • Exhibit symptoms of Klüver-Bucy syndrome • Flattened emotions – Probably related to destruction of the amygdala Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 10. The Amygdala and AssociatedBrain Circuits• Anatomy of the Amygdala Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 11. The Amygdala and AssociatedBrain Circuits• The Amygdala and Fear – Bilateral amygdalectomy reduces fear and aggression in all animals tested – Anger, sadness, and disgust may also be affected – S.M. case study: Inability to recognize fear in facial expressions – Electrical stimulation of amygdala -> Increased vigilance or attention – Fearful faces produce greater amygdala activity than happy/neutral faces Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 12. The Amygdala and Associated Brain Circuits• Learned Fear – Amygdala involved in forming memories of emotional events – Confirmed by fMRI images and PET imaging Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 13. The Amygdala and AssociatedBrain Circuits• The Amygdala and Aggression – Predatory Aggression—Attacks • Against different species for food • Few vocalizations; Attack head or neck • No activity in sympathetic division of ANS – Affective aggression-For show • Used for show, not kill for food • High levels of sympathetic activity • Makes vocalizations; Threatening posture Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 14. The Amygdala and AssociatedBrain Circuits• The Amygdala and Aggression (Cont’d) – Surgery to Reduce Human Aggression • Amygdalactomy • Psychosurgery – last resort – Symptoms • Reduced aggressive asocial behavior • Increased ability to concentrate • Decreased hyperactivity Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 15. Neural Components of Aggression Beyondthe Amygdala• The Hypothalamus and Aggression – Removal of cerebral hemispheres but not hypothalamus -> sham rage – Behavior reversed with small lesions in hypothalamus – Hypothalamus may normally be inhibited by telencephalon. Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 16. Neural Components of Aggression Beyondthe Amygdala• The Hypothalamus and Aggression (Cont’d) – Flynn, 1960s • Elicited affective aggression by stimulation medial hypothalamus • Predatory aggression elicited by stimulating lateral hypothalamus Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 17. Neural Components of Aggression Beyond the Amygdala• The Midbrain and Aggression – Two hypothalamic pathways to brain stem involving autonomic function • Medial forebrain bundle -> ventral tegmental area; predatory aggression • Dorsal longitudinal fasciculus -> periaqueductal grey; affective aggression Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 18. Serotonin and Aggression• Neurotransmitter Serotonin – Serotonergic raphe neurons project to the hypothalamus and limbic structures via the medial forebrain bundle ↓Serotonin turn-over ↑aggression in rodents – Drug PCPA blocks serotonin synthesis ↑aggression Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 19. Serotonin and Aggression• Serotonin Receptor Knockout Mice – 14 serotonin receptor subtypes – Knockout Mice (recombinant DNA techniques) – 5-HT1A and 5-HT1B – 5-HT1A and 5-HT1B autoreceptors—global regulatory role – 5-HT1B High concentrations in raphe nuclei, amygdala, PAG, basal ganglia – Agonists: Decrease anxiety, aggressiveness Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 20. Concluding Remarks• Neural Pathways – Experience, expression of emotion involves widespread activity in the nervous system from cortex to ANS as well as: limbic structures, hypothalamus, amygdala – Structures involved in emotions have other functions, including learning and memory Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
  • 21. End of PresentationCopyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins