Emotion

1. Emotion Expression & Experience

2. What is emotion? • No scientific definition • Controlled by distinct neuronal circuits within the brain • We experience emotion consciously • therefore there is a cognitive element, most likely involving the cerebral cortex • Emotion can be viewed as an outcome of the interaction of peripheral & central factors

3. Responses to Emotion • Emotion is accompanied by autonomic, endocrine & skeletomotor responses • Thus it also depends on sub-cortical parts, including: • amygdala • hypothalamus • brain stem

4. Peripheral Responses • Peripheral responses prepare the body for action • Communicate emotions to other people • Example – fear: • increased heart rate & respiration • dry mouth • tense muscles • sweaty palms

5. The Autonomic Nervous System & Emotion • Most changes that accompany emotional states are mediated by autonomic nervous system • The autonomic system is primarily an effector system • controls smooth muscles, heart, exocrine glands • autonomic is involuntary

6. Three Divisions of the ANS • Sympathetic • governs fight or flight response • response to stress • Parasympathetic • rest and digest • Normal conditions • Enteric

8. Role of the Hypothalamus • Contains many of the neuronal circuits that regulate functions that vary with emotion: • Temperature • heart rate • blood pressure • water and food intake • also controls pituitary gland & thereby the endocrine system • controls output of autonomic nervous system

9. Hypothalamic Control of the ANS • The hypothalamus acts on ANS in 2 ways: • Projects to 3 important regions in the brain stem & spinal cord: • to the nucleus of the solitary tract • receives sensory input from viscera • to the brain stem in the rostral ventral medulla • leads to general sympathetic activation • directly to the autonomic outflow of the spinal cord • The hypothalamus acts on endocrine system to release hormones that influence autonomic function

11. Experimental Evidence • Emotional states are elicited by stimulating the hypothalamus • Stephen Ranson - 1932 • stimulated different regions of the hypothalamus in anesthetized animals • Evoked autonomic reactions including changes of heart rate, blood pressure, etc. • Walter Hess - 1940’s • used awake animals • produced behaviors and physiologic changes characteristic of particular emotions e.g. fear

12. Cortical Centers of Emotion • Physiological inputs to the hypothalamus act on the brain stem & autonomic nervous system. • This information reaches the cerebral cortex from the peripheral organs. • This gives rise to the conscious perception of emotion • So where is the cortical representation of emotion?

13. The Limbic System Concept • Is there a “system” ( a group of structures that function together) responsible for emotion? • Scientists identified the limbic system as the key pathway in emotion – 1930’s • Paul Broca • James Papez

14. Broca’s Limbic Lobe • Paul Broca – 1878 • Identified a portion of cortex present in all mammals which is different from surrounding cortical tissue • These areas form a ring or border around the brainstem • Limbus = border , thus limbic lobe • Includes: • cortex around the corpus callosum, especially in the cingulate gyrus • Cortex on the medial surface of the temporal lobe, including the hippocampus • Broca did not relate these structures to emotion

16. The Papez Circuit • James Papez- 1930’s • Proposed that there is an emotion system that links the cortex to the hypothalamus • Emotion is determined by the activity of the cingualte cortex • Emotional expression is governed by the hypothalamus • The Papez Circuit • A group of structures, each connected to the next by a major fiber tract • 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

17. Papez Circuit

18. Studying Emotion • Emotional expression • behavioral manifestations of internal emotion • Emotional experience • subjective feelings of emotion • Limitations of animal models • can study emotional expression but cannot investigate emotional experience • Limitations of human experiments • very often the medical situation which provides information involves damage to or compromise of other neural structures and functions in an uncontrolled way

19. Theories of Emotion- James & Lange • William James & Karl Lange - 1884 • Proposed that the experience we call emotion occurs after the cortex receives signals about physiologic changes • Emotional expression precedes emotional experience • Physiological changes occur in response to stimuli, then we feel emotions • Emotion is the consequence of information from the periphery • We feel sorry because we cry • The physiological changes are the emotion

20. Critique of James & Lange • Emotions are experienced even if physiological changes aren’t sensed • Patients & animals with transected spinal cords do not have lessened emotions • The same physiological changes accompany different emotions and can have other causes • e.g. fear, anger & disease can all increase heart rate & cause sweating

21. Theories of Emotion – Cannon & Bard • Walter Cannon and Phillip Bard - 1927 • Stimuli cause emotional experience • Emotional experience can occur independently of emotional expression • The thalamus plays a pivotal role in emotional sensations • Emotions are produced when signals reach the thalamus directly from sensory receptors or by descending cortical input • The emotion is determined by the pattern of activation of the thalamus

22. The Somatic Marker Hypothesis • Stanley Schacter: • The cortex constructs emotion out of signals received from the periphery • This is called the somatic marker hypothesis: • Emotion is a story the brain concocts to explain bodily reactions • Depends expectations, experience, social context • Thus the same responses can accompany different emotions

23. Current Theories • Antonio Damasio - • Expanded somatic marker hypothesis • Draws a close connection between emotion and cognition. • Emotions are biologically indispensable to decisions. • Studied patients with damage to the amygdala or prefrontal cortex • Research on patients with frontal lobe damage indicates that feelings normally accompany response options • Operate as a biasing device to dictate choice. • “Descartes error” – separating mind & body

24. The Current View • No single neural system produces emotions • Different emotions may depend on different neural circuits, but many of these circuits converge in the same parts of the brain • The limbic system may be involved in some emotional experiences, but it is not the sole neural system underlying emotion • Feelings (emotion) result from the interplay between: • The amygdala, hypothalamus, brain stem & autonomic nervous system and . . . • between amygdala and frontal & limbic cortex

25. Fear & Anxiety • The amygdala is the critical structure • Also involves the hypothalamus & ANS • Demonstrated by: • Kluver-Bucy Syndrome • Electrical stimulation experiments • Patients with damage to the amygdala

26. Klüver-Bucy Syndrome • Heinrich Kluver & Paul Bucy - 1939 • bilateral removal of the temporal lobes in monkeys (which contains the amygdala & hippocampal formation)  • Radical changes in emotional behavior • increased and bizarre sexual behavior • highly oral • failed to recognize familiar objects (psychic blindness) • temporal lobe destruction of visual cortices • emotionally flat • absence of fear - amygdala missing

27. Kluver-Bucy Syndrome

28. The Amygdala • Structure critical to emotional part of Kluver-Bucy syndrome is the amygdala • The amygdala is part of the limbic system • Human patients with damaged amygdalas have reduced ability to recognize fear in others • Electrical stimulation leads to fear and anxiety • 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 • These effects are mediated through the hypothalamus & autonomic nervous system.

29. The Amygdala

30. Anger and Aggression • Definitions: • Predatory aggression • leads to an attack for food • motive is to kill other animal • Affective aggression • behavior for show to scare other animal • lots of sympathetic ANS activity • Mediated by the hypothalamus, midbrain & amygdala • May also involve serotonin

31. The Role of the Hypothalamus • When the entire cerebral hemispheres are removed, sham rage results • Small stimuli provoke violent responses • Difficult to interpret because the entire neocortex is missing • Removal of anterior hypothalamus, sham rage still occurs • Removal of the posterior hypothalamus, sham rage vanishes • Conclusion: posterior hypothalamus is important for aggression and is normally inhibited by neocortex • Electrical stimulation of the hypothalamus • Stimulation of medial hypothalamus leads to affective aggression - hiss and spit at mouse • Stimulation of lateral hypothalamus leads to predatory aggression

32. Possible Role of the Midbrain • Major outputs of hypothalamus to brain stem are • Medial forebrain bundle (mfb) • project to ventral tegmental area • Electrical stimulation of ventral tegmental area can cause predatory aggression • Lesions in ventral tegmental area can abolish affective aggression • Dorsal longitudinal fasciculus (dlf) • project to periaqueductal gray matter • Electrical stimulation of PAG can elicit affective aggression and lesions can abolish affective aggression

33. Possible Role of the Amygdala • Ablation experiments indicate that the amygdala is also involved in aggression • amygdalectomy reduces aggression • Two pathways for aggression: • Predatory aggression - cortex > amygdala > lateral hypothalamus > mfb > ventral tegmental area • Affective aggression - cortex > amygdala > medial hypothalamus > dlf > periaqueductal gray matter • Led to psychosurgical procedures to destroy amygdala in humans • Frontal lobotomy is another example of psychosurgery

34. Possible Role of Serotonin • Experimental evidence suggests that blocking or reducing the synthesis or release of serotonin may increase aggressive behavior • When the gene for serotonin receptors are removed in mice, they become more aggressive • 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

35. Summary • No single neural system produces emotions • Brain structures involved in emotion are multi functional • there are interesting relationships among emotion, memory, and olfaction • Emotion results from the interplay between: • The amygdala, hypothalamus, brain stem & autonomic nervous system and . . . • between amygdala and frontal & limbic cortex