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Limbic system by dr m.hemalatha svs medical college, mahaboob nagar


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Limbic system by dr m.hemalatha svs medical college, mahaboob nagar

  1. 1. T h e L imb i c S y s t em Presenter: Dr. M. Hemalatha Moderater: Dr.V. Sharbandhraj
  2. 2. Over view of presentation • History • Anatomy • Histology • Functional circuitry • Functions of the limbic system • Clinical implications
  3. 3. History • Paul broca applied the term limbic(latin-border)to the curved rim of cortex includes CG,PHG-b/n-diencephalon and cerebral hemespheres • James papez postulated on basis-anatomical data cortical regions linked hippocampus mammilary body and thalamus. • This concept supported by kluver & brucy who showed temporal lobe lesion which disrupts components of the circuit. • Paul maclean coined term LYMBIC SYSTEM to describe brocas lmbic lobe and related sub cortical structures in relation to emotions
  4. 4. Components of limbic system
  5. 5. Components of limbic system 1. Limbic lobe a) cingulate gyrus b) parahippocampal gyurs 2. Hippocampal formation a) dentate gyrus b) hippocampus c) sibicular complex 3. Amygdala 4. Septal area 5. Hypothalamas Others - cortex and insula,uncus,sriaterminalis It is functional anatomical system interconnecting - cortical and sub cortical structures.
  6. 6. ANATOMY & HISTOLO The Cingulate gyrus • Located dorsal to corpus callosum • Includes several cortical regions that are heavily interconnected with the association areas of the cerebral cortex • Posteriorly, it becomes continuous (via bundle of fibres in the white matter-cingulum) with the parahippocapal gyrus.
  7. 7. The Parahippocampal gyrus • Located in medial temporal lobe • Lies between the hippocampal fissure and the collateral sulcus • Continuous with the hippocampus along with the medial edge of the temporal lobe • Cortical structure of parahippocampal gyrus is six layered.
  8. 8. The Dentate gyrus • -Narrow notched band of gray matter • -Lies between fimbria of the hippocampus and the parahippocampal gyrus • -Anteriorly– contunued into the uncus • -Posteriorly– continuous with indusium griseum -three layers– outer acellular molecular, middle granular inner polymorphic layer.
  9. 9. The hippocampus • Curved elevation of gray matter • Extends entire length of the floor of the inferior horn of the lateral ventricle • anterior end --- pes hippocampus • Terminates posteriorly– beneath the splenium of corpus callosum It is divided into FOUR distinct fields– CA1, CA2 and CA3 ,CA4(CA=Cornu ammonis) Alveus– thin layer of white matter adjacent to the poly morphic layr of hippocampus
  10. 10. • The hippocampus has- • outer molecular- • middle pyramidal- • Inner polymorphic subicular complex Includes pre, para, and subicular parts The transition region b/n hippocampus and parahippocampal gyrus
  11. 11. The amygdala • Located in medial temporal lobe • Just anterior to the hippocampal formation • It is fused with the tip of the tail of the caudate nucleus • Stria terminalis emerges from its post aspect • It is a group of nuclei larger basolater, smaller centromedial • Centromedial amygdala appears to be part of a larger structure that is continuous through the sublenticular innominate with bed nucleus of stria terminalis(extended amygdala)
  12. 12. septal area • Gray matter structure located immediately above the anterior commissure-projects to habenular nucei via stria medullaris thalami and ant hypothalamus. Insula Medial cortical gyrus located between the amygdala and the frontal lobe Uncus Formed by the amygdala and the rostral hippocampus
  13. 13. The entorhinal cortex • Located in the anterior part of the parahippocampal gyrus, on medial surface of temporal lobe • Transition zone between hippocampus and temporal neocortex
  14. 14. The hypothalamus • Lies at the centre of the limbicsystem • It is a confluence of many neural pathways • Devided-anterior to posterior 3 zones Supraoptic region Tuberal region Mammillary region 3 zones devided by fornix in to medial and lateral areas The lateral and medial mamillary nuclei receive hippocampal input through fornix and project to the anterior nucleus of thlamus
  15. 15. Limbic spindle cells(Von Economo)–20 times more in humans than apes--- concentrated in ant cingulate gyrus, prefrontal cortex, the insula - central to governance of social emotion and moral judgement Mirror cells– more developed in humans than in primates-reside in insula, ant cingualte - mediate empathy– the experience of feeling the emotions of another
  16. 16. Connections of the limbic system • The major structures of limbic system are interconnected with each other and with other components of nervous system in various ways. In generel, it is area of intimate processing between hypothalamus and cortical information processing The connecting pathways of limbic system are– the alveus, the fimbriae, the fornix, the mamillothalamic tract, and the stria terminalis Neurotransmitter system in limbic system include– dopamine, serotonin, noradrenergic, and cholinergic systems
  18. 18. Hippocampus conections major inputs---layers 2 &3 of ERC septal & hypothalamic fibers via fornix few from c/L hippo campal formation glutaminergic fibers frm – fimbria
  19. 19. Hippocapal efferents
  20. 20. Circuits of amygdala
  21. 21. Functions of the limbic system • The Ls is involved in behaviour required for self-preservation and the preservation of species control over behaviour regulated by hypothalamus and brainstem, Plays a role is sexual behaviour, Has special role in memory Part Function Amygdala AGGRESSION and FEAR Cingulate gyrus AUTONOMIC FUNCTION Hippocampus RECENT MEMORY Hypothalamus ENDOCRINE FUNCTION Mammillary body LONG MEMORY Nucleus accumbens ADDICTION Prefrontal area PERSONALITY Parahippocampus SPATIAL MEMORY
  22. 22. Olfaction: Amygdala and ERC are closely related olfactory cortex-role in processing of olfactory sensations. Amygdala-involves in emotional response to smell ERC- concerns with olfactory memories
  23. 23. Appetite and eating behaviors: Amygdala –food choice and emotional modulation of food intake Hypothalamus:LN-centre for control of feeding VMN-functions satiety centre EMOTIONAL RESPONSES FEAR: - response- produced by stimulation- amygdala and hypothalamus - amygdala involves in fear learning - imaging studies -viewing fearful faces stimulates leftamygdala damage-abolishes fear
  24. 24. Autonomic endocrine responses stimulation of the anterior cingulate & hypothalamus triggers -ANS Excessive stimulation- amplification of emotions and motor responses and may lead to anxiety, tics, impulsivity, and OCD. Inhibition leads to akinetic mutism, Post cingulate is important for visual spatial memory functions
  25. 25. Rage and placidity: - feeing of intense,violent or growing anger,associated with fright or flight response. - when faced with thretening situations hypotalamus releases harmones rapidly-rage - destruction of VM hypothalamic and septal nuclei intact cerebral cortices –rage - B/L damage amygdala-placidity - VM is destroyed after amgdala-placidity converted to rage
  26. 26. Sleep and dreams • PET,fMRI-shown LS is most active brain area in processing of dreaming. • LS-ties emotions and memory during REM to form content of dreams. • SCN Hypothalamus - cercadian rhythem generation-controls sleep-wake cycle • -GABAnergic,glutaminergic neurons- -VLPO-inhibits major arousal meconsms-promotes sleep • Lateral hypohalamic area-Orexinergic neurons –that promotes-wakefulness by inhibting VLPO,REM promoting thalamic nuclei- PPT-LDT.
  27. 27. Social cognition: - cingulate gyrus , basolateral amygdala are involved -- involves unerstandng and dealing with other people -- involves functioning regions that mediates-face perception, emotional processing ,self referense and working memory-support the complex behaviors for social interactions
  28. 28. Sexual behavior
  29. 29. Sexual behavior • MPOA- hypothalamus –key stucture in control of male sexual behavior, • Dopamin triggers penile erection by acting on oxytocenergic neurons in the PVN of hypothalamus • The inhibition of these neurons by GABA and its agonists,opioid like drugs inhibits sexual response • Glutaminergic inputs from Medial amygdala and bed nucleus stria terminalis - MPOA-mediates female stimulated increased dopamin –enhances copulatory ability,^ glutamate –MPOA- facilitate copulation and genital reflexes during ejaculation
  30. 30. memory Emotional memory:emotion has power ful influence on learning and memory Amygdala ,prefrontal cortex, medial temporl lobe-consolidation, retrival of emotional memories Amygdala,prefrotal cortex, and hippocampus-acuisition, extinction and recovery of fears to cues Hippocampus –critical for recent , declaratie memory Medial temporal lobe memory system: hippocampus ,adjecent cortex,para hppocampal region and enterorhinal perirhinal regions--storage of new memories Diencephalic memory system:hypothalamus,mammilary body,DM neucleus of thalamus-storage of recent memory --dysfunction of circuit-korsakoffs syndrome
  31. 31. Addiction and motivation • Reward circuitry under lying addictive behavior includes amygdala and nucleus accumbens • Amygdala plays acentral role in cue induced relapse.relapse is associated with cues, stress and single dose of drug abuse results in release of excitatory neuro transmitters in hippocampus and amygdala • The pathway of motivated behavior involves the prefrontal cortex,ventral tegmental area,amygdala,nucleus accumbense involved in motivation to take drugs of abuse and compulsive nature of drug taking.
  32. 32. CLINICAL IMPLICATIONS • TEMPORAL LOBE EPILEPSY—mc-hippocampal sclerosis hippocampal sclerosis+amygdala+parahppocampal gyrus termed –MTS-its not limited to medial temporal lobe also a LS-disorder • Limbic encephalitis-paraneoplastic syndrome – with Ca lung,breast. - mecnsm of disease not known-involves hippo,amygdala,cingulate gyrus,insula OFC -pts develops subacute memory loss,dementia,invluntory movements and ataxia
  33. 33. Alzhiemers dementia • Gross– medial temporal lobe atrophy and hippocampal atrophy most common • Plaques and tangles most frequently present in hippocampal and entorhinal cortex • Hippocampal damage-antegrade amnesia Hypofunction and hyperfunction of some anterior limbic areas---prefrontal regions and sub cortical structures-thalamus, striatum,amygdala BPAD
  34. 34. Korsakoffs psycosis • Caused by B1 deficiency-damage periventricular areas: medial thalamus, hypothalamus, mamillary bodies,reticular formation • Lesions show petechial hemorrhages, edema, myelin loss, and reactive gliosis. Neurons generally preserved. • Recent memory is more disturbed than remote memory,immediate recall is preserved. Limbic epilepsy-amygdala, hippocampus, ERC, cingulate or OFC • fear, déjà vu, jamais vu, elementary and complex visual hallucinations, illusions, forced thinking, or emotional distress.
  35. 35. • Anxiety disorders-may be result -failure of ant cingulate, hippocampus to modulate amygdala Kluver-bucy syndrome • Bilateral destruction of amygdala and inferior temporal cortex agnosia,placidity,hyperorality,hypersexuality • Causes: cerebraltruma,herpis encephalitis, infections alziemers dementias and other dementias,neimanpicks disease &CVdiseases
  36. 36. schizophrenia • Various addictive compounds affect the dopamine transmission in nucleus accumbens ( ventral striatum or (mesolimbic) and frontal cortical (mesocortical) systems. • these pathways functionally unbalanced in patients with schizophrenia. • pts - schizophrenia -diminished dopamine effects through mesocortical systems to the prefrontal cortex. Produce negetive symptoms . • increase in dopamine effects via the mesolimbic system to the ventral striatal system, resulting in positive symptoms
  37. 37. Autism and aspergers syndrome-cingulategyrus, and affective processing-dysfunction leads -ASD ADHD amygdala (BLcircuit) mediates cognitive • Enlarged hippocampus - children and adolecents in response to disturbances in perception of time,temporal proccessing and stimulus seeking associated with ADHD. • Disrupted connections b/n amygdala & orbitofrontal cortex may contribute behavioral disinhibition in people with ADHD
  38. 38. References • Kaplan and saddock’s comprehensinve textbook of psychiatry • Lishman, organic psychiatry • Adams & victor neuroanatomy • Lymbic system by E. Mohan das • Internet