Limbic system by dr ali


Published on

Published in: Health & Medicine, Technology
1 Comment
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Limbic system by dr ali

  1. 1. The Limbic System PRESENTER: DR. MD. OSMAN ALI
  2. 2. Scheme of presentation  Introduction  Anatomy  Physiology  Applied aspects
  3. 3. Case of Arthur Shawcross
  4. 4. What is limbic system?  It includes structures forming a border between hypothalamus and cerebral cortex.  It is simply functional anatomic system of interconnected cortical and subcortical structures.
  5. 5. Parts of limbic system Parts mostly listed are  Limbic cortex—the cingulate and the parahippocampal gyri  The hippocampal formation– the dentate gyrus, the hippocampus, the subicular complex.  The amygdala  The septal area  The hypothalamus, the related thalamic(ant) and cortical areas Other parts included are--- insula, entorhinal cortex, nucleus accumbens No unanimity exists on brain structures that constitute the LS 
  6. 6. History of concept of the limbic system 1  Paul Broca– coined the term limbic(Le Grand Lobe Limbique)-- to include curved rim of cortex including cingulate and parahippocampal gyrus which was different from the rest of the cerebral mantle(appeared paler)(Broca’s cortex/lobe). This cortex later shown to be composed of only three layers– labelled allocortex to distinguish it from the six layered eucortex that make up most of the cerebral mantle
  7. 7. History of concept of the limbic system 2  James Papez(1937)– postulated these cortical regions(the cingulate gyrus and the parahippocampal gyrus ) are linked to hippocampus, mamillary body and anterior thalamus in circuit that mediated emotional behaviour(Papez circuit)  Emotions tend to go round and round in this circuit
  8. 8. History of concept of the LS 3  Heinrich Kluver and Paul Bucy(1939)—by removing temporal lobes in monkeys they found that amygdala of temporal lobe has role in taming and other basic instincts– fighting, fleeing, feeding and sex  Kluver Bucy syndrome
  9. 9. History of concept of the LS 4  Paul Maclean(1952)--- coined the term limbic system to describe broca’s lobe and related subcortical nuclei as the neural substitute for emotion
  10. 10. History of concept of limbic system 5  Originally term limbic system encompassed only Broca’s cortex and Papez’s circuitry and later amygdala is included  Further, the functions of amygdala and hippocampal system proved to have more to do with attention and formation of specific memories than with emotions
  11. 11. 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 cingulate bundle of fibres in the white matter) with the parahippocapal gyrus.
  12. 12. 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
  13. 13. 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
  14. 14. The hippocampus  Curved elevation of gray matter  Extends throughout the entire lenghth of the floor of the inferior horn of the lateral ventricle  Expanded anterior end --- pes hippocampus  Terminates posteriorly– beneath the splenium of corpus callosum  Alveus– thin layer of white matter beneath the convex ventricular surface  Fimbria– bundle formed by nerve fibres originated in hippocampus--- becomes continuous with the crus of fornix – passes anteriorly and inferiorly--coloumn of fornix pass through hypothalamus into the mamillary bodies
  15. 15. The Subicular complex  Includes pre, para, and the subicular parts  The transition region ) between the hippocampus and parahippocampal gyrus
  16. 16. 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)
  17. 17. The septal area  Gray matter structure located immediately above the anterior commissure
  18. 18. The insula  Medial cortical gyrus located between the amygdala and the frontal lobe )
  19. 19. The uncus  Formed by the amygdala and the rostral hippocampus
  20. 20. 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
  21. 21. The hypothalamus, the thalamus and cortical areas  The lateral and medial mamillary nuclei receive hippocampal input through fornix and project to the anterior nuclei of hypothlamus
  22. 22. Histology of the limbic system 1  Cortical structure of parahippocampal gyrus is six layered. As the cortex is traced into the hippocampus,there is gradual trasnition from a six to a three layered arrangement  The hippocampus has-- outer molecular, middle pyramidal and inner polymorphic layer. It is divided into three distinct fields– CA1, CA2 and CA3 (CA=Cornu Ammonis) --Molecular layer-- consist of nerve fibres and scattered small neurons --Pyramidal layer-- consist of many large pyramid shaped neurons ---Polymorphic layer-- is similar to the polymorphic layer of the cortex seen else where
  23. 23. Histology of limbic system 2  The dentate gyrus comprises three layers– outer acellular molecular, middle granular and inner polymorphic layer. Pyramidal layer is replaced by the granular layer ---Granular layer is composed of densely arranged rounded or oval neurons that give rise to axons that terminate upon the dendrites of the pyramidal cells in hippocampus  Basolateral nuclei of amygdala– have connectivity and some other anatomical characteristics similar to cortical region
  24. 24. Histology of limbic system 3  John Allman and Giacomo Rizzolatti identified the limbic spindle cells and mirror cells the undergrid prosocial mentation  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
  25. 25. Histology of limbic system 4  Mirror cells– more developed in humans than in primates--reside in insula, ant cingualte—  - mediate empathy– the experience of feeling the emotions of another
  26. 26. Connections of the limbic system 1  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
  27. 27. Connections of limbic system 2  Entorhinal cortex funnesl highly processed cortical information to the hippocampal formation and dentate gyrus  The layers of dentate gyrus connected each other and finally project to the hippocampus  The fields CA3 and CA1 of hippocampus are connected each other and finally project to subicular complex
  28. 28. Connections of limbic system 3  Basolateral nuclei of amygdala directly and reciprocally connected with the temporal, insular and prefrontal cortices---- n shares bidirectional connctions with the medial dorsal thalamic nuclei  Medial amygdaloid nucleus has reciprocal connections with endocrine portion of hypothalamus  Lateral part of extended amygdala connected with brainstem and lateral hypothalamus and receives cortical limbic region and the basolateral amygdaloid complex
  29. 29. Connections of the LS 4  The septal area reciprocally connected with the hippocampus, the amygdala, and the hypothalamus and projects to numerous structures in the brainstem  Posterior nuclei of hypothalamus shares reciprocal connections with extended amygdala  LS also interacts with components of the basal ganglial system. Thus functions of basal ganglia extens beyond the regulation of motor activities  Limbic system recieves inputs from the smell receptors in the nose
  30. 30. Functions of the limbic system 1  The Ls is involved in behaviour required for self- preservation and the preservation of species  control over instinctual behaviour regulated by hypothalamus and brainstem  Critical in emotions such as fear  Plays a role is sexual behaviour  Has special role in memory
  31. 31. Functions of limbic system(ant, post cingulate) 2  Ant cingulate -- for integrating affective and motor behaviour– stimulation of the anterior cingulate triggers autonomic nervous system  Excessive stimulation leads to 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 and memory functions
  32. 32. Functions of limbic system(amygdala vs adrenal gland)3  Anatomy and physiology of the adrenal gland are reflected in the anatomy and physiology of the amygdala circuit and hippocampal circuit  Adrenaline secreted by the adrenal core is processed by the amygdala system  Cortisone secreted by adrenal cortex is processed by the hippocampal formation
  33. 33. Functions of limbic system (functional divisions) 4  Rostral limbic system— amygdala, septum, orbitofrontal cortex, anterior insula, and anterior cingulate --important for emotions  Caudal system– hippocampus, posterior parahippocampal cortex and posterior cingulate -important for memory and visual spatial functions
  34. 34. The functions of limbic system(neurotransmitters) 5  Neurotransmitter system in limbic system include– dopamine, serotonin, noradrenergic, and cholinergic systems
  35. 35. The LS (amygdala) in emotions 1  In generel, amygdala assign emotional significance to sensory experiences  Ls directs the hypothalamus to express the motor and endocrine components of emotional states
  36. 36. The LS (amygdala) in emotions 2  Emotional experiences and expressions per se are accompanied and even initiated by body responses (change in heart and respiratory rate and blood pressure). The responses waned with repitition as they become familiar(habituation)  The amygdala was shown to be important to processing these experiences.(selective activation of amygdala=framing effect)
  37. 37. The LS(amygdala) in emotions 3  The body responses help a person to attain via the amygdala, a certain kind of memory and that emotions is due to a challenge to the pattern of that memory, not the body responses themselves  Fear is not an expression of an experience per se, but of a memory based anticipation of pain that may be realistic and imagined
  38. 38. The LS (hippocampus) in memory 1  Hippocampus is concerned with recent memory converting it to long term memory– memory of the remote past events before the lesion developed is unaffected.  Anterograde amnesia is present  Hippocampal circuit places bounds, boundaries on experience and behaviour
  39. 39. The LS (hippocamppus) in memory 2  The hippocampus is important to an organism’s ability to reset an internal co-ordinate system. This process is critical to navigation and episodic memory  While the amygdala is processing what is novel during habituation, the hippocampus is processing the context within which habituation is happening: the hippocampus is processing what is already familiar  The co-ordinates are constructed by attending to what is not, at the moment, the focus of navigating our world. Eg: to walk through a door we must process the walls so as not to bump into them
  40. 40. The LS (hippocampus) in memory 3  In damage to hippocampus– the memory of what is happening to the patient personally fails to become familiar
  41. 41. The LS(hippocampus) in motivation and attidude 1  The hippocampal circuit brings together emotion and motivation ---The emotion—the processing of familiarty ---The Motivation– the processing of readiness to engage the world in practical manner  Attitudes (emotions plus motivation) are dispositional states that embody the experience of the individual
  42. 42. The LS(hippocampus) in motivation and attitude 2  Freud’s project for a scientific psychology developed a theory of motivation based on memory rather than on drive. Freud noted that motivation are the prospective aspects of memories  Papez simply stated that the circuit could account for attitudes without saying how
  43. 43. The LS in sexual behaviour  Directly involved in elements of sexual functioning  Stimulation of various sites of the limbic system have elicited penile erection.  Hippocampus– genital tumescence, regulation of release of gonadotropins.  Amagdala– in oral and then in genital benaviour  Olfactory sense is strongly involved in both feeding and mating  Those areas activated by emotions of fear and anxiety are notably quiescent when the woman experience an orgasm
  44. 44. The LS in violence behaviour  The fear is processed in amygdala – stimulation of it elicits defensive and aggressive responses  Other parts involved are– hypothalamus and septal area  The prefrontal cortex allows humans to exercise some control over their resposes  Aggressive behaviour have been noted individual with damage to the medial temporal lobe and with developing brain tumor in the limbic system  Frontal lobe injury commonest type in infancy and early childhood have lifelong consequences  Case of serial killer Arthur Shawcross
  45. 45. The LS in positive mental health(ant cingulate and insula) 1  Both the limbic anterior cingulate and insula appears to be active in the positive emotions of humor, trust and empathy  The prosocial biological activity of the anterior cingulate cortex and insula was highest in individiuals with highest level of social awareness--the biological differences for positive mental health
  46. 46. The LS(ant cingulate gyrus) in positive mental health 2  Anterior cingulate gyrus links valence and memory to create attachment  Along with the hippocampus, the anterior cingulate is the brain region most responsible for making the past meaningful  Anterior cingulate fMRI images light up when a lover gazes at a pictures of a partner’s face or when a new mother hear her infant’s cry
  47. 47. The LD(insula) in positive mental health 3  Helps to bring visceral feelings into consciousness  The pain in one’s heart of grief , the warmth in one’s heart of love, and the tightness in one’s gut from fear all make their way into consciousness through the insula
  48. 48. The LS in positive mental health(hippocampus and amygdala) 4  fMRI studies of kundalini yoga practitioners demonstrates-- the meditation activates the activity of the hippocampus and right lateral amygdala which in turn leads to parasympathetic stimulation and sensation of deep peacefulness
  49. 49. The LS in positive mental health(frontal lobe) 5  Frontal lobe connectivity to the limbic system underscores its executive function which includes the ability to delay gratification, comprehend symbolic language, and most important, to establish temporal sequencing  Frontal lobes through their connection to the amygdala, hippocampus and other limbic structures encode emotional learning quite distinct from both conventional conditioning and declarative memory
  50. 50. The LS in schizophrenia 1  Because of its role in controlling emotions, the LS has been hypothesized to be involved in pathophysiology of schizophrenia  Limbic activation is diminished  Abnormally increased limbic activation time(threat related fascial emotions of anger and fear)  Antipsychotics block limbic receptors to dopamine as well as receptors of the extrapyramidal system
  51. 51. The LS in schizophrenia 2  Neuropathology findings—decrease in size of regions including the amygdala the hippocampus and parahippocmapal gyrus  Hippocampus is not only smaller, but is functionally abnormal as indicated by disturbances in glutamate transmission  Disorganisaion of neurons within the hippocampus has also been reported
  52. 52. The LS in BPAD  Hyperactivity and hyperfunction of some limbic and para limbic areas---including amygdala and ventrial striation as well as in the cerebellum
  53. 53. The LS is anxiety and OCD  In addition to receiving noradrenergic and serotonergic innervation the LS contains highest concentration of GABA A receptors  Increased activity of the septohippocampal pathway—leads to anxiety  Cingulate gyrus has been particulary implicated in pathophysiology of OCD
  54. 54. The LS in dementia Involved in  Alzheimers disease  Limbic encephalitis  Wernick/Korsakoff  Anoxic encephalopathy  HSV encephalitis  Post traumatic amnesia  Strokes involving PCA or thalamoperforators  ACOM aneursyms
  55. 55. The LS in Alzhiemers  Gross– medial temporal lobe atrophy and hippocampal atrophy most common  Plaques and tangles most frequently present in hippocampal and entorhinal cortex
  56. 56. Limbic encephalopathy  Usually due to metastatic ca of lung  Marked disturbance of memory for recent events  Affective disturbance– severe anxiety and depression  Pathology– combination of degeneration and inflammation on the medial temporal lobe structures— the hippocampus, uncus, amygdaloid nucleus, dentate gyrus, insular and posterior orbital cortex  Where memory failure is predominat feature the possibity of limbic encephalopathy should be considered
  57. 57. The LS in Wernicke and Korsakoff  Caused by B1 deficiency  Changes involve periventricular areas: medial thalamus, hypothalamus, mamillary bodies, PAG, reticular formation  Lesions show petechial hemorrhages, edema, myelin loss, and reactive gliosis. Neurons generally preserved.
  58. 58. The LS in epilepsy n hippocampal sclerosis  Hippocampal cell loss can be considered a cause and consequence of repeated seizures  Hippocampal sclerosis—seen in 47—70% of all TLE
  59. 59. Limbic epilepsy  Limbic epilepsy can originate in the amygdala, hippocampus, entorhinal cortex, cingulate or orbital frontal cortex  Pts classically describe fear, déjà vu, jamais vu, elementary and complex visual hallucinations, illusions, forced thinking, or emotional distress.
  60. 60. Kluver Bucy syndrome  Bilateral removal of temporal lobe– amygdala, para amygdala area  Features– no evidence of fear or anger, unable to appreciate object visually, increased appetite, increased sexual activity- indscriminatly seek partnership with male, female animals
  61. 61. Herpes simplex encephalitis
  62. 62. The LS in psychosurgery  Stereotactic operations on the amygdaloid nuclei: decreased emotional excitability  OCD: cingulotomy, anterior cingulotomy, and limbic leucotomy may be effective  Pain: cingulotomy  Epilepsy:TLE  Tourette: disconnection of the anterior cingulate from the thalamus results in improvement of symptoms
  63. 63. References  Kaplan and saddock’s comprehensinve textbook of psychiatry 9th ed (2009), lippincott w&w  Lishman, organic psychiatry  Snell’s clinical neuroanatomy for medical students  Ganong’s review of physiology,Lange  Internet
  64. 64. Thank you