3_Neuroanatomy_and_Neurolocalization_of_the_Limbic_system_and_Hypothalamus.pptx

3_Neuroanatomy_and_Neurolocalization_of_the_Limbic_system_and_Hypothalamus.pptx

1. Neuroanatomy and Neurolocalization of the Limbic system and Hypothalamus Moderator : Dr. Yohannes (Neurologist) By: Keberte (NR2) FEB 10, 2020

2. Outlines Introduction Components of Limbic system Neuroanatomy and Neurophysiology of Limbic system Functions of Limbic system Clinical correlates of the limbic system Hypothalamus N euroanatomy , function and clinical correlate

3. Limbic system

4. Limbic system Limbus (Latin)- border or margin 1878- Paul Broca - ‘le grand lobe limbique ’ 1937- James papez - Described anatomical model of emotion the Papez Circuit. 1939- Heinrich Kluver & Paul Bucy First evidence that limbic system was responsible for cortical representation of emotions

5. Introduction These structures have evolved Olfaction in simpler animals  diverse functions including the regulation of emotions , memory , appetitive drives , and autonomic and neuroendocrine control .

6. Limbic system components Limbic cortex Parahippocampal gyrus Anterior Insula Cingulate gyrus Temporal lobe Medial orbitofrontal cortex Amygdala Hippocampal formation Dentate gyrus Hippocampus subiculum Olfactory cortex Several nuclei in the medial Thalamus Hypothalamus Basal Ganglia Ventral striatum Ventral pallidum Septal area Brainstem

7. Connecting pathways Alveus Fimbria Fornix Mammillothalamic tract Stria Terminalis

8. Limbic Cortex Contains Parahippocampal gyrus Cingulate Gyrus Medial orbitofrontal cortex Temporal lobe Anterior Insula

9. The limbic system :- two main circuits Anterior limbic circuit involves the amygdala and its connections,  important in the control of emotion and affective Posterior limbic circuit involves the hippocampal formation  F or learning and declarative memory

10. Circuits of the limbic circuit

11. Blood supply of the limbic system ACA- pericallosal artery- most of cingulate gyrus and its isthmus PCA-temporal branches parahippocampal gyrus Choroid plexus of temporal horn, hippocampal formation, parts of amygdaloid complex Circle of willis Hypothalamic nuclei functionally associated with the limbic system

12. Amygdala The amygdala (Greek word for Almond ) Just anterior to the hippocampus , G roup of nuclei located in the anteromedial temporal lobe. Three main nuclei B asolateral , Centromedial , C entral Nuclei

13. Main connections of Amygdala

14. Modulates somatic and visceral components of PNS These responses include Sympatho excitation -tachycardia, sweating , mydriasis . secretion of cortisol and epinephrine Projections to the hippocampus may explain why emotionally charged events are more likely to be remembered than emotionally neutral ones

15. Input  anterior cingulate cortex may be important for driving motor responses P rojection from orbitomedial prefrontal cortex  amygdala is important in inhibiting emotional responses when inappropriate for the social or behavioral context.

16. Clinical correlates Bilateral lesions of the amygdala typically affect the ability to recognize the affective meaning of facial expressions , particularly the expression of fear Klüver-Bucy syndrome Bila teral removal of Temporal lobe Inability to recognize the significance of visual objects, emotional blunting, inappropriate eating behaviour, and hyper sexuality

17. - Seizures Medial temporal lobe seizures that involve the amygdala may cause powerful emotions of fear and panic . Anxiety disorder : abnormal activation of the amygdala in posttraumatic stress disorder(PTSD)

18. Activity in the septal area appears to be important in pleasurable states . C onnections b/n amygdala and hypothalamic and brainstem centers for autonomic control mediate changes in Heart rate, peristalsis, gastric secretion, piloerection , sweating, and other changes commonly seen with strong emotions

19. connections b/n the limbic cortex, amygdala, and the hypothalamus are N euroendocrinological changes seen in different emotional states.

20. Bilateral lesions of the orbitomedial prefrontal cortex result in socially inappropriate behavior impulsivity emotional disinhibition

21. Hippocampus The hippocampal formation consists of the Dentate gyrus (CA3) Hippocampus Cornu Ammonis (CA1-CA4 areas ) Subiculum Three layered- Archicortex “First “ or “original” cortex

22. Hippocampus Named because it resembles seahorse Curved elevation of grey matter Extends through entire floor inferior horn of lateral Ventricle Anterior end- pes hippocampus/ hippocampal head

23. Beneath Ependyma layer  Alveus Fimbria continous with the crus of fornix terminates at splenium of the corpus callosum

24. Dentate gyrus – between fimbria of the hippocampus and parahippocampal gyrus Post- continous with Indusium griseum Ant- continued into the Uncus Principal neurons- Granular cells

25. Parahippocampal gyri Lies between the hippocampal fissure and the collateral sulcus Continous with hippocampus The Entorhinal cortex ( Brodmann’s area 28) lies in the anterior portions of the parahippocampal gyrus , adjacent to the subiculum , the major input and output relay between association cortex and the hippocampal formation.

26. Components of perihippocampal gyrus Perirhinal cortex Parahippocampal cortex Piriform cortex Periamygdaloid cortex Presubicular cortex Parasubicular cortex Entorhinal cortex Prorhinal cortex

27. Medial temporal memory system

28. Papez circuit Processed information in the Hippocampus  fornix mammilary body of hypothalamusanterior nucleus of thalamus  cingulate cortex parahippocampal formation

29. Patient H.M.: A Landmark Case of Amnesia Henry Gustav Molaison Medically Intractible seizure 1953 – Underwent bilateral medial temporal lobectomy Seizure was controlled Developed severe Anterograde Amnesia H.M .’s personality and general intelligence assessed by IQ testing were normal H e retained the ability to learn certain tasks that did not require conscious recall.

30. Declarative(explicit memory) A bility to learn , store, and retrieve information A utobiographical events ( episodic memory ), Facts and name ( semantic memory ), Places ( spatial memory ).

31. Amnesia - Loss of declarative memory B ilateral damage of the medial temporal cortex impairs the ability to learn and store new information. T his disorder reflects involvement of the entorhinal and perirhinal cortices, followed by that of the hippocampus and the loss of the cholinergic neurons in the basal forebrain

32. Lesions of the lateral temporal lobe interfere with the ability to recall remote events or previously learned facts.

33. Anterograde amnesia is the deficit in forming new memories, Retrograde amnesia is the loss of memories from a period of time before the brain injury combination of retrograde and anterograde amnesia for declarative memories is typical of lesions of the medial temporal lobe or medial diencephalic memory systems

34. Korsakoff syndrome Midline lesion, diancephalic amnesia Learning and declarative memory also are selectively impaired by head injury , herpes simplex encephalitis paraneoplastic limbic encephalitis .

35. Olfactory system The rapid access to the amygdala and hippocampal circuit may explain the tendency of some odors to rapidly evoke emotions and memories

36. Complex partial seizure – Focal lesion in the medial temporal lobe Olfactory hallucination Involv’t of olfactory cortex at the level of the uncus or amygdala ( uncinate seizures).-> uncinate bundle oromandibular automatism , complex motor behaviors, fear & affective symptoms associated with autonomic effects déjà-vu or jamais vu that reflect disturbances of episodic memory involvement of the hippocampus & parahippocampal cortex).

37. Alzheimer’s disease memory loss for recent events is often prominent, with no other obvious abnormalities. bilateral hippocampal, temporal, and basal forebrain structures affected.

38. Selective affection of the limbic system Rabies Herpes simplex encephalitis Paraneoplastic limbic encephalitis

39. Hypothalamus Part of ventral diencephalon Area measures 14*18*20mm, weighs 4g Boundaries are not well defined Anteriorly - merges with basal olefactory and preoptic area Caudally- continous with central grey matter and tegmentem of the midbrain Laterally- subthalamic region Superiorly- Thalamus

40. Inferiorly- pitutary gland via pitutary stalk & Infandibulum Lateropost . – borders GP, basal forebrain nuclei, IC,subthalamic region , crus cerebri Has numerous nerve cells

41. The tuber cinereum , bulge located between the optic chiasm and the mammillary bodies Mammilary bodies are paired structures that form the posterior portion of the hypothalamus

42. Hypothalamic nuclei Paraventricular area Medial lateral

43. Afferent fibers of Hypothalamus

44. Main efferent fibers Descending fibers to the brainstem and spinal cord M ammillothalamic tract M ammillotegmental tract Multiple pathways to the limbic system.

45. Connection to the pitutary T wo pathways : 1. nerve fibers that travel from the supraoptic and paraventricularnuclei to the posterior lobe of the hypophysis Hypothalamohypophyseal tract Oxytocin & Vasopressin S upraoptic nucleus, which produces vasopressin, acts as an osmoreceptor

46. 2. Hypophyseal portal system R eleasing hormones and the release-inhibiting hormones to the secretory cells of the anterior lobe of the hypophysis ACTH, FSH, LH,TSH, and CH Melanocyte- stimulating hormone (MSH) and luteotropic hormone ( LTH)

47. Main function of the hypothalamus 1 . H omeostatic mechanisms controlling hunger, thirst, sexual desire, sleep–wake cycles, etc. 2. E ndocrine control, via the pituitary 3. A utonomic control 4. L imbic mechanisms Mneumonic : HEAL

48. Main hypothalamic nuclei function

49. Functions of hypothalamus Autonomic control Anterior hypothalamic area & preoptic area influence parasympathetic responses ; ↓B.P, ↓H.R contraction of the bladder,↑ GI mobility, ↑ gastric acidity, salivation, pupillary constriction . Stimulation of the posterior and lateral nuclei  sympathetic responses , which include ↑ B.P, ↑ H.R, ↓ GI peristalisis , Pupillary dilation , and hyperglycemia

50. Temprature regulation The anterior portion of the hypothalamus controls mechanisms that dissipate heat loss Dilatation of skin blood vessels and sweating, which lower the body temperature . Stimulation of the posterior portion of the hypothalamus  vasoconstriction of the skin blood vessels and inhibition of sweating

51. Regulation of Food and Water Intake Stimulation of the lateral region of the hypothalamus  feeling of hunger  increase in food intake .( hunger center ) Bilateral destruction of this center results in anorexia, with weight loss L ateral region of the hypothalamus  thirst center. Lesion  Decreased water intake

52. Stimulation of the medial region of the hypothalamus inhibits eating and reduces food intake( satiety center ) Bilateral destruction of the satiety center  uncontrolled voracious appetite, causing extreme obesity .

53. Emotion and behavior H ypothalamus is the integrator of afferent information received from other areas of the nervous system and brings about the physical expression of emotion ; L ateral hypothalamic nuclei stimulation may cause the symptoms and signs of rage, lesions may lead to passivity. V entromedial nucleus stimulation may cause passivity , lesions of this nucleus may lead to rage.

54. The hypothalamus probably also participates in circuitry involved in sexual desire and other complex motivational states.

55. Control of circadian rhythm The hypothalamus controls many circadian rhythms, including body temperature, adrenocortical activity eosinophil count, and renal secretion Disturbance of Alertness and sleep Suprachiasmatic nucleus – Ant. Hypothalamus Hypocretin / orexin nucleus in posterolateral hypothalamus

56. Alzheimers - Loss of neuron in the suprachiasmatic nucleus can they will have increased variability and decreased stability of the rhythm Optic glioma - in the region of suprachiasmatic nucleus- loss of circardian rhythmicity.

57. Clinical correlates hypothalamic hamartoma . unusual seizures consisting of laughing episodes ( gelastic epilepsy ), associated with disturbances in emotional behavior including irritability and aggression, and with cognitive impairment .

58. Sleep disturbance Lesions of the anterior hypothalamus- Insomnia Lesions of the posterior hypothalamus- Hypersomnia , Obesity and wasting Severe obesity can occur as the result of hypothalamic lesions . A ssociated with genital hypoplasia or atrophy.

59. Sexual disorders In children, sexual retardation may result from hypothalamic lesions . After puberty, the patient with hypothalamic disease may have impotence or amenorrhea .

60. Hyperthermia lesions of the hypothalamus Craniotomy, trauma, bleeding Hypothermia Post . hypothalamic lesion Causes :- Wernickes Encephalopathy, HI, Craniopharyngoma , glioblastoma multiform, surgery, hydrocephalus, Infarction and sarcoidosis

61. Diabetes insipidus results from a lesion of the supraoptic nucleus or Interruption of the nervous pathway to the posterior lobe of the hypophysis . Patient passes large volumes of urine of low specific gravity .

62. References Brazis localization in clinical neurology, 6 th edition, Dejong’s the neurologic examination, 8 th edition . Mayo Clinic Medical Neurosciences, 5 th edition Blumenfield , Neuroanatomy through clinical cases, 2 nd edition Snell’s clinical Neuroanatomy , 8 th edition

63. Thank you!