Emotion

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Emotion

  1. 1. Emotion Expression & Experience
  2. 2. What is emotion? <ul><li>No scientific definition </li></ul><ul><li>Controlled by distinct neuronal circuits within the brain </li></ul><ul><li>We experience emotion consciously </li></ul><ul><ul><li>therefore there is a cognitive element, most likely involving the cerebral cortex </li></ul></ul><ul><li>Emotion can be viewed as an outcome of the interaction of peripheral & central factors </li></ul>
  3. 3. Responses to Emotion <ul><li>Emotion is accompanied by autonomic, endocrine & skeletomotor responses </li></ul><ul><li>Thus it also depends on sub-cortical parts, including: </li></ul><ul><ul><li>amygdala </li></ul></ul><ul><ul><li>hypothalamus </li></ul></ul><ul><ul><li>brain stem </li></ul></ul>
  4. 4. Peripheral Responses <ul><li>Peripheral responses prepare the body for action </li></ul><ul><li>Communicate emotions to other people </li></ul><ul><li>Example – fear: </li></ul><ul><ul><li>increased heart rate & respiration </li></ul></ul><ul><ul><li>dry mouth </li></ul></ul><ul><ul><li>tense muscles </li></ul></ul><ul><ul><li>sweaty palms </li></ul></ul>
  5. 5. The Autonomic Nervous System & Emotion <ul><li>Most changes that accompany emotional states are mediated by autonomic nervous system </li></ul><ul><li>The autonomic system is primarily an effector system </li></ul><ul><ul><li>controls smooth muscles, heart, exocrine glands </li></ul></ul><ul><ul><li>autonomic is involuntary </li></ul></ul>
  6. 6. Three Divisions of the ANS <ul><li>Sympathetic </li></ul><ul><ul><li>governs fight or flight response </li></ul></ul><ul><ul><li>response to stress </li></ul></ul><ul><li>Parasympathetic </li></ul><ul><ul><li>rest and digest </li></ul></ul><ul><ul><li>Normal conditions </li></ul></ul><ul><li>Enteric </li></ul>
  7. 8. Role of the Hypothalamus <ul><li>Contains many of the neuronal circuits that regulate functions that vary with emotion: </li></ul><ul><ul><li>Temperature </li></ul></ul><ul><ul><li>heart rate </li></ul></ul><ul><ul><li>blood pressure </li></ul></ul><ul><ul><li>water and food intake </li></ul></ul><ul><li>also controls pituitary gland & thereby the endocrine system </li></ul><ul><li>controls output of autonomic nervous system </li></ul><ul><li>  </li></ul>
  8. 9. Hypothalamic Control of the ANS <ul><li>The hypothalamus acts on ANS in 2 ways: </li></ul><ul><li>Projects to 3 important regions in the brain stem & spinal cord: </li></ul><ul><ul><li>to the nucleus of the solitary tract </li></ul></ul><ul><ul><li>receives sensory input from viscera </li></ul></ul><ul><ul><li>to the brain stem in the rostral ventral medulla </li></ul></ul><ul><ul><li>leads to general sympathetic activation </li></ul></ul><ul><ul><li>directly to the autonomic outflow of the spinal cord </li></ul></ul><ul><li>The hypothalamus acts on endocrine system to release hormones that influence autonomic function </li></ul>
  9. 11. Experimental Evidence <ul><li>Emotional states are elicited by stimulating the hypothalamus </li></ul><ul><li>Stephen Ranson - 1932 </li></ul><ul><ul><li>stimulated different regions of the hypothalamus in anesthetized animals </li></ul></ul><ul><ul><li>Evoked autonomic reactions including changes of heart rate, blood pressure, etc. </li></ul></ul><ul><li>Walter Hess - 1940’s </li></ul><ul><ul><li>used awake animals </li></ul></ul><ul><ul><li>produced behaviors and physiologic changes characteristic of particular emotions e.g. fear </li></ul></ul>
  10. 12. Cortical Centers of Emotion <ul><li>Physiological inputs to the hypothalamus act on the brain stem & autonomic nervous system. </li></ul><ul><li>This information reaches the cerebral cortex from the peripheral organs. </li></ul><ul><li>This gives rise to the conscious perception of emotion </li></ul><ul><li>So where is the cortical representation of emotion? </li></ul>
  11. 13. The Limbic System Concept <ul><li>Is there a “system” ( a group of structures that function together) responsible for emotion? </li></ul><ul><li>Scientists identified the limbic system as the key pathway in emotion – 1930’s </li></ul><ul><ul><li>Paul Broca </li></ul></ul><ul><ul><li>James Papez </li></ul></ul>
  12. 14. Broca’s Limbic Lobe <ul><li>Paul Broca – 1878 </li></ul><ul><li>Identified a portion of cortex present in all mammals which is different from surrounding cortical tissue </li></ul><ul><ul><li>These areas form a ring or border around the brainstem </li></ul></ul><ul><ul><li>Limbus = border , thus limbic lobe </li></ul></ul><ul><li>Includes: </li></ul><ul><ul><li>cortex around the corpus callosum, especially in the cingulate gyrus </li></ul></ul><ul><ul><li>Cortex on the medial surface of the temporal lobe, including the hippocampus </li></ul></ul><ul><li>Broca did not relate these structures to emotion </li></ul>
  13. 16. The Papez Circuit <ul><li>James Papez- 1930’s </li></ul><ul><li>Proposed that there is an emotion system that links the cortex to the hypothalamus </li></ul><ul><ul><li>Emotion is determined by the activity of the cingualte cortex </li></ul></ul><ul><ul><li>Emotional expression is governed by the hypothalamus </li></ul></ul><ul><li>The Papez Circuit </li></ul><ul><ul><li>A group of structures, each connected to the next by a major fiber tract </li></ul></ul><ul><ul><li>The cingulate cortex projects to the hippocampus, which projects to the hypothalamus through the fornix; the hypothalamus projects to the anterior nuclei of the thalamus, which reach back to the cortex </li></ul></ul>
  14. 17. Papez Circuit
  15. 18. Studying Emotion <ul><li>Emotional expression </li></ul><ul><ul><li>behavioral manifestations of internal emotion </li></ul></ul><ul><li>Emotional experience </li></ul><ul><ul><li>subjective feelings of emotion </li></ul></ul><ul><li>Limitations of animal models </li></ul><ul><ul><li>can study emotional expression but cannot investigate emotional experience </li></ul></ul><ul><li>Limitations of human experiments </li></ul><ul><ul><li>very often the medical situation which provides information involves damage to or compromise of other neural structures and functions in an uncontrolled way </li></ul></ul>
  16. 19. Theories of Emotion- James & Lange <ul><li>William James & Karl Lange - 1884 </li></ul><ul><li>Proposed that the experience we call emotion occurs after the cortex receives signals about physiologic changes </li></ul><ul><ul><li>Emotional expression precedes emotional experience </li></ul></ul><ul><ul><li>Physiological changes occur in response to stimuli, then we feel emotions </li></ul></ul><ul><li>Emotion is the consequence of information from the periphery </li></ul><ul><ul><li>We feel sorry because we cry </li></ul></ul><ul><li>The physiological changes are the emotion </li></ul>
  17. 20. Critique of James & Lange <ul><li>Emotions are experienced even if physiological changes aren’t sensed </li></ul><ul><ul><li>Patients & animals with transected spinal cords do not have lessened emotions </li></ul></ul><ul><li>The same physiological changes accompany different emotions and can have other causes </li></ul><ul><ul><li>e.g. fear, anger & disease can all increase heart rate & cause sweating </li></ul></ul>
  18. 21. Theories of Emotion – Cannon & Bard <ul><li>Walter Cannon and Phillip Bard - 1927 </li></ul><ul><li>Stimuli cause emotional experience </li></ul><ul><li>Emotional experience can occur independently of emotional expression </li></ul><ul><li>The thalamus plays a pivotal role in emotional sensations </li></ul><ul><li>Emotions are produced when signals reach the thalamus directly from sensory receptors or by descending cortical input </li></ul><ul><li>The emotion is determined by the pattern of activation of the thalamus </li></ul>
  19. 22. The Somatic Marker Hypothesis <ul><li>Stanley Schacter: </li></ul><ul><li>The cortex constructs emotion out of signals received from the periphery </li></ul><ul><li>This is called the somatic marker hypothesis: </li></ul><ul><li>Emotion is a story the brain concocts to explain bodily reactions </li></ul><ul><ul><li>Depends expectations, experience, social context </li></ul></ul><ul><ul><li>Thus the same responses can accompany different emotions </li></ul></ul>
  20. 23. Current Theories <ul><li>Antonio Damasio - </li></ul><ul><li>Expanded somatic marker hypothesis </li></ul><ul><li>Draws a close connection between emotion and cognition. </li></ul><ul><li>Emotions are biologically indispensable to decisions. </li></ul><ul><li>Studied patients with damage to the amygdala or prefrontal cortex </li></ul><ul><ul><li>Research on patients with frontal lobe damage indicates that feelings normally accompany response options </li></ul></ul><ul><ul><li>Operate as a biasing device to dictate choice. </li></ul></ul><ul><li>“ Descartes error” – separating mind & body </li></ul>
  21. 24. The Current View <ul><li>No single neural system produces emotions </li></ul><ul><li>Different emotions may depend on different neural circuits, but many of these circuits converge in the same parts of the brain </li></ul><ul><li>The limbic system may be involved in some emotional experiences, but it is not the sole neural system underlying emotion </li></ul><ul><li>Feelings (emotion) result from the interplay between: </li></ul><ul><ul><li>The amygdala, hypothalamus, brain stem & autonomic nervous system and . . . </li></ul></ul><ul><ul><li>between amygdala and frontal & limbic cortex </li></ul></ul>
  22. 25. Fear & Anxiety <ul><li>The amygdala is the critical structure </li></ul><ul><li>Also involves the hypothalamus & ANS </li></ul><ul><li>Demonstrated by: </li></ul><ul><li>Kluver-Bucy Syndrome </li></ul><ul><li>Electrical stimulation experiments </li></ul><ul><li>Patients with damage to the amygdala </li></ul>
  23. 26. Klüver-Bucy Syndrome <ul><li>Heinrich Kluver & Paul Bucy - 1939 </li></ul><ul><ul><li>bilateral removal of the temporal lobes in monkeys (which contains the amygdala & hippocampal formation)  </li></ul></ul><ul><li>Radical changes in emotional behavior </li></ul><ul><ul><li>increased and bizarre sexual behavior </li></ul></ul><ul><ul><li>highly oral </li></ul></ul><ul><ul><li>failed to recognize familiar objects ( psychic blindness) </li></ul></ul><ul><ul><ul><li>temporal lobe destruction of visual cortices </li></ul></ul></ul><ul><ul><li>emotionally flat </li></ul></ul><ul><ul><ul><li>absence of fear - amygdala missing </li></ul></ul></ul>
  24. 27. Kluver-Bucy Syndrome
  25. 28. The Amygdala <ul><li>Structure critical to emotional part of Kluver-Bucy syndrome is the amygdala </li></ul><ul><li>The amygdala is part of the limbic system </li></ul><ul><li>Human patients with damaged amygdalas have reduced ability to recognize fear in others </li></ul><ul><li>Electrical stimulation leads to fear and anxiety </li></ul><ul><li>A learned fear response, where pain is associated with a sensory input, may involve a circuit through the basolateral nuclei & central nucleus of the amygdala </li></ul><ul><li>These effects are mediated through the hypothalamus & autonomic nervous system. </li></ul>
  26. 29. The Amygdala
  27. 30. Anger and Aggression <ul><li>Definitions: </li></ul><ul><li>Predatory aggression </li></ul><ul><ul><li>leads to an attack for food </li></ul></ul><ul><ul><li>motive is to kill other animal </li></ul></ul><ul><li>Affective aggression </li></ul><ul><ul><li>behavior for show to scare other animal </li></ul></ul><ul><ul><li>lots of sympathetic ANS activity </li></ul></ul><ul><li>Mediated by the hypothalamus, midbrain & amygdala </li></ul><ul><li>May also involve serotonin </li></ul>
  28. 31. The Role of the Hypothalamus <ul><li>When the entire cerebral hemispheres are removed, sham rage results </li></ul><ul><ul><li>Small stimuli provoke violent responses </li></ul></ul><ul><ul><li>Difficult to interpret because the entire neocortex is missing </li></ul></ul><ul><ul><li>Removal of anterior hypothalamus, sham rage still occurs </li></ul></ul><ul><ul><li>Removal of the posterior hypothalamus, sham rage vanishes </li></ul></ul><ul><ul><li>Conclusion: posterior hypothalamus is important for aggression and is normally inhibited by neocortex </li></ul></ul><ul><li>Electrical stimulation of the hypothalamus </li></ul><ul><ul><li>Stimulation of medial hypothalamus leads to affective aggression - hiss and spit at mouse </li></ul></ul><ul><ul><li>Stimulation of lateral hypothalamus leads to predatory aggression </li></ul></ul>
  29. 32. Possible Role of the Midbrain <ul><li>Major outputs of hypothalamus to brain stem are </li></ul><ul><li>Medial forebrain bundle (mfb) </li></ul><ul><ul><li>project to ventral tegmental area </li></ul></ul><ul><ul><li>Electrical stimulation of ventral tegmental area can cause predatory aggression </li></ul></ul><ul><ul><li>Lesions in ventral tegmental area can abolish affective aggression </li></ul></ul><ul><li>Dorsal longitudinal fasciculus (dlf) </li></ul><ul><ul><li>project to periaqueductal gray matter </li></ul></ul><ul><ul><li>Electrical stimulation of PAG can elicit affective aggression and lesions can abolish affective aggression </li></ul></ul>
  30. 33. Possible Role of the Amygdala <ul><li>Ablation experiments indicate that the amygdala is also involved in aggression </li></ul><ul><ul><li>amygdalectomy reduces aggression </li></ul></ul><ul><li>Two pathways for aggression: </li></ul><ul><li>Predatory aggression - cortex > amygdala > lateral hypothalamus > mfb > ventral tegmental area </li></ul><ul><li>Affective aggression - cortex > amygdala > medial hypothalamus > dlf > periaqueductal gray matter </li></ul><ul><li>Led to psychosurgical procedures to destroy amygdala in humans </li></ul><ul><ul><li>Frontal lobotomy is another example of psychosurgery </li></ul></ul>
  31. 34. Possible Role of Serotonin <ul><li>Experimental evidence suggests that blocking or reducing the synthesis or release of serotonin may increase aggressive behavior </li></ul><ul><li>When the gene for serotonin receptors are removed in mice, they become more aggressive </li></ul><ul><li>The type of receptor that is most effective when deleted is normally found in the amygdala, periaqueductal gray matter, and basal ganglia, as well as the raphe nuclei </li></ul>
  32. 35. Summary <ul><li>No single neural system produces emotions </li></ul><ul><li>Brain structures involved in emotion are multi functional </li></ul><ul><ul><li>there are interesting relationships among emotion, memory, and olfaction </li></ul></ul><ul><li>Emotion results from the interplay between: </li></ul><ul><ul><li>The amygdala, hypothalamus, brain stem & autonomic nervous system and . . . </li></ul></ul><ul><ul><li>between amygdala and frontal & limbic cortex </li></ul></ul>

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