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3_Neuroanatomy_and_Neurolocalization_of_the_Limbic_system_and_Hypothalamus.pptx
- 1. NEUROANATOMYAND NEUROLOCALIZATION OF THELIMBIC SYSTEM AND HYPOTHALAMUS Moderator : Dr. Yohannes (Neurologist) By: Keberte(NR2) FEB 10, 2020
- 2. Outlines • Introduction • Componentsof Limbic system • Neuroanatomy and Neurophysiology of Limbic system • Functions of Limbic system • Clinical correlates of the limbic system • Hypothalamus Neuroanatomy , function and clinical correlate
- 3.
- 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 structureshave 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
- 13. • The limbicsystem :- 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 For learning and declarative memory
- 14. Circuits of thelimbic circuit
- 15. Blood supply ofthe 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
- 17. Amygdala • The amygdala(Greek word for Almond) • Just anterior to the hippocampus, • Group of nuclei located in the anteromedial temporal lobe. • Three main nuclei • Basolateral , • Centromedial, • Central Nuclei
- 18. Main connections ofAmygdala
- 19. • Modulates somaticand 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
- 20. • Input anteriorcingulate cortex may be important for driving motor responses • Projection from orbitomedial prefrontal cortex amygdala is important in inhibiting emotional responses when inappropriate for the social or behavioral context.
- 21. • 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 • Bilateral removal of Temporal lobe • Inability to recognize the significance of visual objects, emotional blunting, inappropriate eating behaviour, and hyper sexuality
- 22. -Seizures Medial temporal lobeseizures that involve the amygdala may cause powerful emotions of fear and panic. • Anxiety disorder: • abnormal activation of the amygdala in posttraumatic stress disorder(PTSD)
- 23. • Activity inthe septal area appears to be important in pleasurable states. • Connections 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
- 24. • connections b/nthe limbic cortex, amygdala, and the hypothalamus are • Neuroendocrinological changes seen in different emotional states.
- 25. • Bilateral lesionsof the orbitomedial prefrontal cortex result in • socially inappropriate behavior • impulsivity • emotional disinhibition
- 26. Hippocampus • The hippocampalformation consists of the • Dentate gyrus (CA3) • Hippocampus Cornu Ammonis (CA1-CA4 areas) • Subiculum • Three layered- Archicortex “First “ or “original” cortex
- 27. • Hippocampus • Namedbecause it resembles seahorse • Curved elevation of grey matter • Extends through entire floor inferior horn of lateral Ventricle • Anterior end- pes hippocampus/ hippocampal head
- 28. • Beneath Ependymalayer Alveus Fimbria continous with the crus of fornix terminates at splenium of the corpus callosum
- 29. • Dentate gyrus– • between fimbria of the hippocampus and parahippocampal gyrus • Post- continous with Indusium griseum • Ant- continued into the Uncus • Principal neurons- Granular cells
- 30. • 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.
- 31. • Components ofperihippocampal gyrus • Perirhinal cortex • Parahippocampal cortex • Piriform cortex • Periamygdaloid cortex • Presubicular cortex • Parasubicular cortex • Entorhinal cortex • Prorhinal cortex
- 32. Medial temporal memorysystem
- 33. Papez circuit • Processedinformation in the Hippocampus fornix mammilary body of hypothalamusanterior nucleus of thalamus cingulate cortex parahippocampal formation
- 34. Patient H.M.: ALandmark 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 • He retained the ability to learn certain tasks that did not require conscious recall.
- 36. • Declarative(explicit memory) •Ability to learn, store, and retrieve information • Autobiographical events (episodic memory), • Facts and name (semantic memory), • Places (spatial memory).
- 37. • Amnesia- Lossof declarative memory • Bilateral damage of the medial temporal cortex • impairs the ability to learn and store new information. • This 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
- 38. • Lesions ofthe lateral temporal lobe interfere with the ability to recall remote events or previously learned facts.
- 39. • Anterograde amnesiais 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
- 41. • Korsakoff syndrome •Midline lesion, diancephalic amnesia • Learning and declarative memory also are selectively impaired by • head injury, • herpes simplex encephalitis • paraneoplastic limbic encephalitis.
- 42. • Olfactory system •The rapid access to the amygdala and hippocampal circuit may explain the tendency of some odors to rapidly evoke emotions and memories
- 43. • Complex partialseizure – 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).
- 44. • Alzheimer’s disease •memory loss for recent events is often prominent, with no other obvious abnormalities. • bilateral hippocampal, temporal, and basal forebrain structures affected.
- 45. • Selective affectionof the limbic system • Rabies • Herpes simplex encephalitis • Paraneoplastic limbic encephalitis
- 46. Hypothalamus • Part ofventral 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
- 47. • Inferiorly- pitutarygland via pitutary stalk & Infandibulum • Lateropost. – borders GP, basal forebrain nuclei, IC,subthalamic region , crus cerebri • Has numerous nerve cells
- 48. • The tubercinereum, bulge located between the optic chiasm and the mammillary bodies • Mammilary bodies are paired structures that form the posterior portion of the hypothalamus
- 49. • Hypothalamic nuclei •Paraventricular area • Medial • lateral
- 51. Afferent fibers ofHypothalamus
- 52. Main efferent fibers •Descending fibers to the brainstem and spinal cord • Mammillothalamic tract • Mammillotegmental tract • Multiple pathways to the limbic system.
- 54. Connection to thepitutary • Two pathways: 1. nerve fibers that travel from the supraoptic and paraventricularnuclei to the posterior lobe of the hypophysis • Hypothalamohypophyseal tract • Oxytocin & Vasopressin • Supraoptic nucleus, which produces vasopressin, acts as an osmoreceptor
- 55. 2. Hypophyseal portalsystem • Releasing 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)
- 56. Main function ofthe hypothalamus 1. Homeostatic mechanisms controlling hunger, thirst, sexual desire, sleep–wake cycles, etc. 2. Endocrine control, via the pituitary 3. Autonomic control 4. Limbic mechanisms • Mneumonic: HEAL
- 57. Main hypothalamic nucleifunction
- 58. 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
- 59. • 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
- 60. • Regulation ofFood 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 • Lateral region of the hypothalamus thirst center. • Lesion Decreased water intake
- 61. • Stimulation ofthe 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.
- 62. • Emotion andbehavior • Hypothalamus is the integrator of afferent information received from other areas of the nervous system and brings about the physical expression of emotion; • Lateral hypothalamic nuclei • stimulation may cause the symptoms and signs of rage, • lesions may lead to passivity. • Ventromedial nucleus • stimulation may cause passivity, • lesions of this nucleus may lead to rage.
- 63. • The hypothalamusprobably also participates in circuitry involved in sexual desire and other complex motivational states.
- 64. • Control ofcircadian 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
- 65. - Alzheimers- Lossof 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.
- 66. Clinical correlates • hypothalamichamartoma. • unusual seizures consisting of laughing episodes (gelastic epilepsy), • associated with disturbances in emotional behavior including irritability and aggression, and with cognitive impairment.
- 67. • 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. • Associated with genital hypoplasia or atrophy.
- 68. • Sexual disorders •In children, sexual retardation may result from hypothalamic lesions. • After puberty, the patient with hypothalamic disease may have impotence or amenorrhea.
- 69. • Hyperthermia • lesionsof the hypothalamus • Craniotomy, trauma, bleeding • Hypothermia • Post. hypothalamic lesion • Causes:- Wernickes Encephalopathy, HI, Craniopharyngoma, glioblastoma multiform, surgery, hydrocephalus, Infarction and sarcoidosis
- 70. • Diabetes insipidusresults 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.
- 71. References • Brazis localizationin clinical neurology, 6th edition, • Dejong’s the neurologic examination, 8th edition. • Mayo Clinic Medical Neurosciences, 5th edition • Blumenfield, Neuroanatomy through clinical cases, 2nd edition • Snell’s clinical Neuroanatomy, 8th edition
- 72.
Editor's Notes
- #4 Describe a group of structures that lie in the border zone between cerebral cortex and the hypothalamus
- #6 Temporal lobe the anterior and medial lobe
- #7 Alveus fibers intitiated in the hippocampus cortex, which converges on the medial side of the hippocampus to form fimbria, the fimbria leaves the posterior end of the hippocampus as the crus of the fornix, the 2 crura converge to form the body of the fornix. As the 2 crura come together they are connected by the transverse fibers called the commisure of the fornix Through septum pellucidum the fornix is connected to the CC. body of fornix divides anteriorly in to 2 anterior column of fornix. Each column dissapears in to the lateral wall of the 3rd ventricle to reach mamillary body Mamillary body which gives important connection between mamillary bodies and the anterior nuclear group of the thalamus Strai terminalis- from the posterior aspect of the amygdaloid nucleusfollows the curve of the caudate nucleus and comes to lie on the floor of the lateral ventricle
- #10 Blue regions represent limbic cortex, also known as paralimbic cortex or limbic association cortex. The limbic system includes certain cortical areas located in the medial and anterior temporal lobes , anterior insula , inferior medial frontal lobes, and cingulate gyri. It also includes deeper structures, such as the hippocampal formation and the amygdala, located within the medial temporal lobes. several nuclei in the medial thalamus, hypothalamus, basal ganglia, septal area, and brainstem. These areas are interconnected by a variety of pathways, including the fornix—a paired, arch-shaped white matter structure that connects the hippocampal formation to the hypothalamus and septal nuclei.
- #14 Telencephalic components of the anterior (salmon) and posterior (red and yellow) limbic circuits. The anterior limbic circuit is centered on the amygdala and includes the orbitofrontal and anterior cingulate cortices. These structures are interconnected with each other and the limbic striatum either directly or through the mediodorsal and midline thalamic nuclei. The anterior limbic circuit is involved in emotion. The posterior limbic circuit is centered on the hippocampus and includes the entorhinal cortex, parahippocampal gyrus, and the posterior cingulate cortex. These structures are interconnected with each other either directly or through the fornix, with a relay in the mammillary bodies and anterior thalamic nucleus. The posterior limbic circuit is involved in declarative (explicit) memory, including autobiographic memory (episodic memory), learning of facts (semantic memory), and spatial memory
- #17 Found in the anteromedial temporal lobe
- #18 The basolateral group interconnects the amygdala with the cerebral cortex, thalamus, and basal forebrain The amygdala consists of several nuclei that are grouped into a basolateral complex, centromedial complex, and olfactory complex (not shown). Nuclei of the basolateral complex receive input from the cerebral cortex and thalamus and are reciprocally connected with these structures as well as with the basal forebrain and limbic striatum, both directly and by relay in the thalamic mediodorsal nucleus. Sensory information is processed in the basolateral complex and tagged with emotional significance. The basolateral complex projects to the central nucleus,which projects to hypothalamic and brainstem nuclei that mediate endocrine,autonomic, and motor responses to emotion, particularly conditioned fear.
- #19 …… thus response to a particular situation
- #22 Seizures involving the amygdala and adjacent cortex Functional neuroimaging studies have shown abnormal activation of the amygdala in PTSD
- #25 likely by interrupting inhibitory control the prefrontal cortex exerts on the amygdala.
- #28 Alveus- A thin layer of white matter, contain nerve fibers which originated in the hippocampus and coverge medially to form a bundle called fimbria
- #29 Dentate gyrus is a narrow nothced band of grey matter that lies between…. Posteriorly it accompanies the fimbria almost to the splenium of CC and becomes continous with IG which is a thin layer of grey matter which covers the superior part of the CC While the principal cells of the Hippocampus and subiculum is pyramidal cells
- #31 About two-thirds of the input from association cortex reaches the entorhinal cortex via relays in the adjacent perirhinal cortex and parahippocampal cortex
- #32 The medial temporal memory system includes the hippocampal formation, entorhinal cortex, and parahippocampal region. A, Association areas of neocortex project to the parahippocampal cortex, which projects to entorhinal cortex. The entorhinal cortex is the gateway for entry of highly elaborated information into the hippocampus. The hippocampal formation comprises the dentate gyrus, hippocampus proper (CA1-CA3 regions), and subiculum. The intrinsic circuit of the hippocampal formation involves feed-forward excitatory connections. Granule cells of the dentate gyrus send excitatory axons (called mossy fibers) to CA3 pyramidal neurons. CA3 pyramidal cells project via Schaffer collaterals to CA1 pyramidal neurons, which project to the subiculum. B, There are reciprocal feed-forward and feedback connections among the neocortex, parahippocampal gyrus, and hippocampal formation. Association areas of the neocortex project to the perirhinal and parahippocampal cortices. These, in turn, project to the entorhinal cortex. Neurons of CA1 and subiculum project back to the entorhinal cortex, which relays this input to the parahippocampal cortex, which projects to neocortex.
- #34 Including amygdala, hippocampus and enterohinal cortex
- #35 declarative (or explicit) memory, which involves conscious recollection of facts or experiences, and nondeclarative (or implicit) memory, which involves nonconscious learning of skills, habits, and other acquired behaviors
- #37 In early stages, remote memory is spared b/c they are stored in the association area of lateral temporal neocortex, but eventually the remote memory will be affected Unilateral lesions do not usually produce severe memory loss. However, unilateral lesions of the dominant (usually left) medial temporal or diencephalic structures can cause some deficits in verbal memory, while unilateral lesions of the nondominant (usually right) hemisphere can cause deficits in visual-spatial memory.
- #41 By acute or subacute lesion that affect the medial temporal lobe or its connections Korsakoff syndrome caused by thiamine deficiency The lesions primarily involve the anterior and dorsomedial thalamic nuclei and the mammillary bodies.
- #42 They have transient loss of awareness and this may be preceded by olefactory halucination ( olefactory cortex involvement at the level of the uncus or amygdala)
- #45 Subacute course of change in emotional behavioral, memory loss, complex partial seizures
- #47 Numerous nerve cells not uniformly distributed but arranged in definite groups or nuclear groups … all 3 zones have descending fibers to the Brainsstem and SC
- #48 Tubur cinereum- grau protuberence
- #50 In the medial zone, the following hypothalamic nuclei can be recognized, from anterior to posterior: (1) part of the preoptic nucleus; (2) the anterior nucleus, which merges with the preoptic nucleus; (3) part of the suprachiasmatic nucleus; (4) the paraventricular nucleus;
- #51 Somatic and visceral afferents. through collateral branches of the lemniscal afferent fibers and the tractus solitarius and through the reticular formation. Visual afferents leave the optic chiasma and pass to the suprachiasmatic nucleus Olfaction travels through the medial forebrain bundle. Corticohypothalamic fibers arise from the frontallobe of the cerebral cortex and pass directly to the hypothalamus. Hippocampohypothalamic fibers pass from the hippocampus through the fornix to the mammillary body. Amygdalohypothalamic fibers pass from the amygdaloid complex to the hypothalamus through the stria terminalis and by a route that passes inferior to the lentiform nucleus. Thalamohypothalamic fibers arise from the dorsomedial and midline thalamic nuclei. Tegmental fibers arise from the midbrain.
- #52 The mammillothalamic tract arises in the mammillary body and terminates in the anterior nucleus of the thalamus. Here, the pathway is relayed to the cingulate gyrus. The mammillotegmental tract arises from the mammillary body and terminates in the cells of the reticular formation in the tegmentum of the midbrain. 4. Multiple pathways to the limbic system.
- #54 The hypothalamus is connected to the hypophysis cerebri (pituitary gland) by two pathways: nerve fibers that travel from the supraoptic and paraventricular nuclei to the posterior lobe of the hypophysis and (2)long and short portal blood vessels that connect sinusoids in the median eminence and infundibulum with capillary plexuses in the anterior lobe of the hypophysis The hormones are passed along the axons together with carrier proteins called neurophysins and are released at the axon terminals (). Here, the hormones are absorbed into the bloodstream in fenestrated capillaries of the posterior lobe of the hypophysis.
- #55 Neurosecretory cells situated mainly in the medial zone of the hypothalamus are responsible for the production of the releasing hormones and release-inhibitory hormones. The hormones are packaged into granules andare transported along the axons of these cells into the median eminence and infundibulum. Here, the granules are released by exocytosis onto fenestrated capillaries at the upper end of the hypophyseal portal system.
- #58 Electrical stimulation of the hypothalamus in animal experiments shows that has been shown that considerable overlap of function occurs in these
- #59 Hyperthermia causes are Acute- Craniotomy, trauma, bleeding Hypothermia and Poikilothermia- Post. hypothalamic lesion Causes:- Wernickes Encephalopathy, HI, Craniopharyngoma, glioblastoma multiform, surgery, hydrocephalus, Infarction and sarcoidosis Physiologic rhythm Diurnal variation of Temprature- Median eminence lesion
- #60 Thirst appears to result from the activation of osmoreceptors in the anterior regions of the hypothalamus. Hypovolemia or elevated body temperature can also activate thirst. Lesions of the lateral hypothalamus decrease water intake.
- #64 -Suprachiasmatic nucleus recieves afferent from retina and possibly from the lateral geniculate body and project mainly to other hypothalamic nuclei but also to the basal forebrain, thalamus, periaquedectal gray Loss of neuron in the suprachiasmatic neucleus can occur in Alzheimers( they will have increased variability and decreased stability of the rhythm - Optic glioma- in the region of suprachiasmatic nucleus- loss of circardian rhythmicity.
- #67 Obesity Most frequent lesions:- craniopharyngeoma, pitutary adenoma, surgery for the removal of these tumors, trauma, encephalitis, vascular lesion on the base of the brain.
- #70 When Intracellular DHN Inc intracellular Na+ conc, Extracellular DHN inc Angiotensin 2 conc in the hypothalamic blood stimulate this osmoreceptors release of ADH by large cells of supraoptic and paraventricular nuclei In experimental animals destructive lesion of the lateral hypothalamus causes Adipsia( reduced water intake) and destructive lesion in the ventromedial nuclei causes Hyperdipsia. - DI results from at least 90% of damage of the supraoptic and paraventricular nuclei, it involves supraoptic- hypophyseal tract rather than the neuronal bodies themselves, transient DI can also be familal or caused by granuloms ( sarcoidosis, meningovascular syphillis, histocytosis), vascular lesion, trauma, meningoencephalitis