Hypothalamus & Limbic System

1. Hypothalamus & Limbic System Chapter 12 Excluding pages pg263-278

2. Hypothalamus Regulates Homeostasis Hunger Thirst Body Temp, Blood Pressure Sex Drives & Behavior Emotions Via Limbic System Pituitary Gland Circadian Rhythms

3. Neuroanatomy of Hypothalamus • Know the names of the nuclei on both sections • Periventricular, medial and lateral • Preoptic anterior, middle and posterior

4. Neural Basis of Emotion Fear, Anxiety, & Envy& Love, Joy Role of Cingulate Gyrus, Amygdala, Hypothalamus, Hippocampus

6. Emotional Experience Input from senses Processed by cerebral cortex Emotional Expression Behavioral output from somatic motor, autonomic and hypothalamus Emotions

8. Theories of Emotion • James Lange Theory 1884 • Experience emotions IN RESPONSE to physiological changes in our body • Feel sad because we cry NOT cry because we feel sad • The emotion is the physiology

9. Cannon-Bard Theory • 1927: Emotional experience can occur independently of emotion expression • Transect animal spinal cord and emotional expression observed. • Removal or damage to somatic sensory system does not diminish emotion experience.

11. Discrepency for James-Lange • The same physiological characteristics can occur without the emotion such as in illness fever etc. • Difference according to Cannon is the activation of the thalamus (hypothalamus) for the emotional response

12. Limbic Lobe 1878 Paul Broca • identified medial surface of cerebrum that are different from the rest of cortex—called it border=limbic lobe • Cortex surrounding corpus callosum • Thought to be involved in olfaction

13. Papez Circuit • James Papez 1930s identified limbic structures involved in emotion (added the thalamic structures to the limbic lobe) • Cingulate cortex to hippocampus to hypothalamus via the fornix and from hypothalamus to anterior nuclei of thalamus • Neocortex connects to cingulate cortex • Allows one to experience emotion

16. Limbic System • Limbic Lobe and Papez Circuit together • This distinguishes human emotions and responses to situations from the stereotypical response of animals due to reflexive systems involving brainstem

17. Frontal Lobes of Cortex • Provides Rationale Control of emotional disposition & involved in personality • Injury to frontal lobes causes change in personality • Control of emotions and impulse control • Example of Phineas Gage

19. Pathologies • Tumors and injury to areas of the brain lead to emotional changes. • Damage to cingulate cortex lead to emotional disturbances: fear, depression, irritability

20. Fear, Agression & Anxiety Learned Fear, Anxiety & Temporal Lobes and AMYGDALA

22. Kluver & Bucy Neuroscientist • Remove bilateral temporal lobes and monkeys cannot experience fear, approach humans other monkeys and dangerous situtations • Cannot recognize objects by vision; called psychic blindness-use mouth to identify objects seen • striking increase in sexual activity

23. Kluver-Bucy Syndrome • Humans with temporal lobe lesions show similar behavior as monkeys with temporal lobectomy • Have flattened emotions, don’t feel happy, sad etc

24. Amygdala • Neurons at the pole of the temporal lobe below the cortex on the medial side • Greek name for almond shape • Has 3 nuclei, basolateral, corticomedial and central • Afferents from all lobes of neocortex & hippocampus and cingulate gyrus

26. Input to Amygdala • Basolateral nuclei receive sensory input (visual, gustatory, auditory and tactile); also projects to cortex for perception of emotion • Corticomedial nuclei receive olfactory inputs • Central nuclei contain output neurons to hypothalamus and periaqueductal grey in brainstem for physiological responses

28. Damage to Amygdala • Decreases emotional response • Kluver-Bucy Syndrome=reduced emotionality • Fearlessness • SM human cannot recognize emotional expressions on faces that are fearful, anxious & angry but recognize happy & disgust • Bilateral amygdala removal reduces memory

29. Electrical Stimulation of Amygdala • Cause affective rage when basalateral nuclei is stimulated • Corticomedial stimulation reduces aggression

30. Learned Behaviors • Require the amygdala and work through 2 pathways. Integrate information from all sensory systems and orchestrate the physiological and physchological response • Ventral amygdofugal pathway • Stria terminalis

31. Do Not learnPathway Names

32. Hypothalamus-brainstem • Autonomic nuclei in the brainstem receive synaptic input from hypothalamus via • Medial forebrain bundle • Dorsal longitudinal fasciculus

33. Aggressive Behaviors • Androgen levels in males can alter aggressive behaviors • Predatory aggression: purpose is getting food, little sympathetic NS activity • Medial hypothalamus • Affective aggresion: purpose is scare off enemies/protection • Lateral hypothalamus

34. Hypothalamus and Rabies • Rabies causes excess rage and aggression • Rabies virus damages hypothalamic neurons • Led identification of hypothalamus as critical brain area involved in anger

35. Electrical Stimulation of Hypothalamus • Depending on area, animal shows different behaviors • Associated with eating, sniff & eat • Associated with fear or anger • Demonstrates 2 functions of hypothalamus • Metabolic regulation; homeostasis • Coordinated somatic & visceral responses

36. Serotonin • Serotonin containing neurons located in Raphe nucleus in brainstem that project via medial forebrain bundle to hypothalamus & other limbic structures • Aggressive mice have decreased serotonin turnover • Drugs that block serotonin release or synthesis cause increase in aggression

37. Serotonin Receptors • 14 5HT receptor subtypes • Mice with no (knock-out) gene for 1A and 1B isoform, the type found in Raphe Nucleus are more aggressive & anxious when stressed otherwise act normally • Specific agonist of 1A and 1B reduce anxiety

38. Memory Systems Hippocampus

41. Hippocampus & Relational Memory • Highly processed information from association cortex areas enter hippocampus • Hippocampus integrates them—ties them together and then output is stored in other cortical areas • Allows you to retrieve all the information about an event

42. Patients & Syndromes • HM-mediotemporal lobe • NA--thalamus • Korsakoffs-thalamus & hypothalamus

43. Amnesia • Anterograde • Cannot form any new types of memories so always live at time of injury • Retrograde • Cannot recall stored memories for a specific time period

44. Declarative: Explicit Facts & Events Easy to form, easy to lose Medial Temporal Lobe & Thalamus Non-Declarative: Implicit Takes repetition, hard to lose Procedural Skills & Habits Striatum Classical Conditioning Skeletal Muscles Cerebellum Emotional Responses Amygdala Memory

46. Conscious Recollection • Only declarative memories & not non-declarative memories

47. Declarative Memory • Essential Anatomy • Medial Temporal Lobe • Entorhinal and Perirhinal, Parahippocampal Cx • Hippocampus • Fornix to Mammilary Body of Hypothalamus • Anterior & Dorsomedial Thalamus that project to cingulate cx (limbic system)

48. HM • Had bilateral mediotemporal lobes removed due to epilepsy • Removed amygdala, anterior 2/3 of hippocampus, temporal cortex • Had anterograde amnesia • Studied by Brenda Milner • Could learn by procedural memory but had no recollection of having learned task

50. Squire & Mishkin • Neuroscientists create an animal model for HM symptoms • Lesioned amygdala, hippocampus and perirhinal cortex in temporal lobe of monkeys and found that they could no longer perform in recognition memory tests • Later showed that perirhinal cortex is most important for new memory; temporary storage? Memory consolidation?