Limbic System By Dr. Rabia Inam Gandapore.pptx

Neuroanatomy

1. Limbic System Dr. Rabia Inam Gandapore Assistant Professor Head of Department Anatomy (Dentistry-BKCD) B.D.S (SBDC), M.Phil. Anatomy (KMU), Dip. Implant (Sharjah, Bangkok, ACHERS) , CHPE (KMU),CHR (KMU), Dip. Arts (Florence, Italy )

2. Teaching Methodology LGF (Long Group Format) SGF (Short Group Format) LGD (Long Group Discussion, Interactive discussion with the use of models or diagrams) SGD (Short Group) SDL (Self-Directed Learning) DSL (Directed-Self Learning) PBL (Problem- Based Learning) Online Teaching Method Role Play Demonstrations Laboratory Museum Library (Computed Assisted Learning or E-Learning) Assignments Video tutorial method

3. Goal/Aim (main objective) To help/facilitate/augment the students about the: Describe components of limbic system .

4. Specific Learning Objectives (cognitive) At the end of the lecture the student will able to: Describe components of limbic system .

5. Psychomotor Objective: (Guided response) A student to draw labelled diagram of limbic system .

6. Affective domain To be able to display a good code of conduct and moral values in the class. To cooperate with the teacher and in groups with the colleagues. To demonstrate a responsible behavior in the class and be punctual, regular, attentive and on time in the class. To be able to perform well in the class under the guidance and supervision of the teacher. Study the topic before entering the class. Discuss among colleagues the topic under discussion in SGDs. Participate in group activities and museum classes and follow the rules. Volunteer to participate in psychomotor activities. Listen to the teacher's instructions carefully and follow the guidelines. Ask questions in the class by raising hand and avoid creating a disturbance. To be able to submit all assignments on time and get your sketch logbooks checked.

7. Lesson contents Clinical chair side question: Students will be asked if they know what is the function of Outline: Activity 1 Describe structure and pathway of limbic system .

8. Recommendations Students assessment: MCQs, Flashcards, Diagrams labeling. Learning resources: Langman’s T.W. Sadler, Laiq Hussain Siddiqui, Snell Clinical Anatomy , Netter’s Atlas , BD Chaurasia’s Human anatomy, Internet sources links.

9. Limbic System L imbic ( limbus , border ) system includes nuclei & tracts along border between cerebrum and diencephalon Its a functional grouping rather than anatomical G rey & White mattar structures lodged deep in cerebrum involved in 4 functions; Smell, memory, emotional & behavioral responses and ANS regulation Includes components of cerebrum , diencephalon & mesencephalon (mid-brain) Functional anatomic system of interconnected cortical and sub cortical structures

10. Grey Mattar Structures of Limbic System Limbic Lobe - 2 components 1 . Cingulate Gyrus ( memory, emotional processing & ANS ) 2. Para-Hippocampal Gyrus -Temporal Lobe ( memory processing ) Hippocampus/ Hippocampal formation - Memory (Medial to Para-hippocampal gyrus )- 3 Parts 1. Dentate Gyrus ( afferent information ) 2. Subiculum ( efferent information ) 3. Hippocampus Proper / Cornu amonus ( efferent information ) Amygdala/ amygdaloid body ( emotions, behavior & emotional response to smell ), 2 nuclei 1. Corticomedial nuclear group ( olfaction ) 2. Basolateral nuclear group (all rest except olfaction ) Hypothalamus (diencephalon) 1. Mammillary bodies 2. ANS nuclei (posterior= sympathetic & anterior= parasympathetic ) Thalamus (Diencephalon) 1. Anterior nucleus ( papez circit -Memory ) 2. D orsal medial nucleus (Amygdala to DMN to Prefrontal cortex hence emotions & behaviours ) Epithalamus -Habenula Septal Area (found in the septum pelucidum & para-terminal gyrus ) Connected via Stria Medullaris (reward pathway & emotional response)

11. White Mattar Structures of Limbic System Connects limbic nuclei with each other Fornix= c onnects Hippocampus to Septal area & Mammilary bodies (Hypothalamus) - ( efferent & afferent) MEMORY PATHWAY Stria terminalis & Ventral amygdalofuga l pathway = connects Amygdala with septal area and hypothalamus via stria terminalis (dorsally & underneath corpus callosum= Pathway 1 ) and VAP (ventrally= Pathway-2 )connects with septal area, Hypothalamus & thalamus (dorsal medial nucleus) Stria Medullaris thalami= Connects septal area & habenula ( epithalamus ) Mammalothalamic tract = Mammilary bodies (hypothalamus) to anterior nucleus (thalamus) Medial Forebrain Bundle= 2way connection from prefrontal cortex ( behavior,emotions & memory), runs through hypothalamus (lateral) & connects with reticular formation in brainstem Mammalotegmental Tract & Mamillary peduncles= connects mammillary body with ventral tegmental area (Dopamine area of midbrain) called Mammalotegmental tract & from VTA to MB (mammillary peduncles)

12. Fornix= Hippocampus to Septal area + Mammilary bodies Stria Terminalis : Amygdala with septal area and hypothalamus

13. septal area, Hypothalamus & thalamus

14. Connects septal area & habenula

15. Mammilary bodies (hypothalamus) to anterior nucleus (thalamus)

16. 2way connection from prefrontal cortex (behavior, emotions & memory), runs through hypothalamus (lateral) & connects with reticular formation in brainstem connects mammillary body with ventral tegmental area ( Dopamine) called Mammalotegmental tract & from VTA to MB (mammillary peduncles)

17. Functions of Limbic System Olfaction : Smell activates olfactory epithelial cells in nasal cavity, then olfactory nerves (cribriform plate of ethmoid bone) to olfactory bulb . The action potential send down to the olfactory tracts & it bifurcates and one goes towards medial olfactory striae and other goes laterally called Lateral olfactory striae . Lateral olfactory striae takes olfaction information to two area of limbic system in temporal lobe i.e 1. Parahippocampal gyrus ( Memory of smells ) 2. Amygdala ( emotions related with smell ) Medial Olfactory striae : goes to the orbital frontal cortex

18. 2. Memory & Learning Papez Circuit: Starts at hippocampus i.e Subiculum ( efferent information )goes to fornix (white matter tracts) and then to mammillary bodies(hypothalamus ). From here goes to anterior nucleus (Thalamus ) via mammillothalamic tract . The information then acends to cingulate gyrus Cingulate gyrus then sends information in 2 directions 1. descends down in limbic lobe to para hippocampal gyrus & from here ascends back in the hippocampus i.e. dentate gyrus via the rinocortex and finally once again in Subiculum . 2. goes to Pre-frontal cortex (frontal lobe)- helps for memory to be involved with thoughts and decision making processing.

19. 3. Behaviors Amygdala (epicenter of limbic system ), limbic system is in coordination with cerebral cortex 3 . Behaviors : a. Feeding: Amygdala send information to hypothalamus i.e. Ventomedial Nucleus = Satiety & Lateral Hypothalamic Nucleus= Hunger b. Sexual: Amygdala send information to hypothalamus i.e. Periventricular Nucleus = oxytocin (Female= uterine contraction & breast milk ejection, Male= sexual Orgasm, blood flow to sex organ & sex drive) & Medial pre-optic nucleus (gonadotropin releasing hormone stimulates in male= testosterone-increase sex drive c. Motivation (goal): (Drug abusers =euphoria/ sense of reward) Amygdala send information to septal area ( septum pelucidum & paraterminal gyrus ) and also connects with hypothalamus via Stria terminalis & Ventral amygdalofugal pathway. From septal area & hypothalamus both can communicate with ventral tegmental area (dopamine) in brainstem. From the Ventral tegmental area the dopamine released and information is sent to the Nucleus accumbens & Prefrontal cortex via Mesolimbic pathway & Mesocortical pathway respectively. Hence emotional component is Sense of reward

20. Amygdaloid circuit; VAFP (Ventral Amygdalofugal pathway); VAPP (Ventral Amygdalopetal pathway

21. 4. Emotions Fear, Anger, Rage & Sadness : Amygdala send information (via Stria terminalis & Ventral amygdalofugal pathway ) to hypothalamus . The 2 nuclei involved are posterior hypothalamic nucleus ( descending axon downward via hypothalamicspinal tract & innervates the preganglionic neurons located in the thoracolumbar region of spinal cord , sympathetic nerves will than go to particular organs i.e. Liver (Increase glucose production), heart (increase blood circulation), increase BP & lungs (increase breathing)). Paraventricular nucleus ( corticotropin releasing hormone stimulate anterior pituitary to make hormone called Adrenocorticotropic hormone ( A cth ) which stimulates the adrenal gland to make cortisol-stress response )

22. Rostral (Front) limbic system: • Amygdala, septum, orbitofrontal cortex, anterior insula, and anterior cingulate – Important for emotion Caudal (Back) system: • Hippocampus, posterior parahippocampal cortex and posterior cingulate – Important for memory and visual-spatial functions

23. Hippo wearing a HAT Hippocampus Hypothalamus Amygdala Thalamus (anterior nucleus)

24. Functions Emotional states & related behavioural drives Linking conscious , intellectual functions of cerebral cortex with unconscious & autonomic functions of other portions of brain F acilitating memory storage & retrieval It appears important to : Intellectual ; judgmental; predictive functions & planning ( regulation behavior ) Memory , emotional aspects of behaviour & stereognosis ( size; form & texture ) an appreciation of body image & perceptuospatial function & drive S torage of previous sensory experiences Recall objects seen or music heard in past

25. 1. Amygdala Almond shaped collection of nuclei Lies above inferior horn of lateral ventricle Embedded in uncus Lies near anterior temporal pole, between inferior horn of lateral ventricle & lentiform nucleus Window of limbic system: wide afferent connections with visual , auditory association areas Appears to act as an integration center between the limbic system , the cerebrum & sensory systems

26. Provides an affective connotation to experience and social stimuli Receives afferents from I nferior temporal association cortex ; olfactory tract & septum Catecholamine & serotonin -containing projections from brainstem in medial forebrain bundle A ggression center

27. Functions of Amygdala Behavioural awareness areas Project into limbic system one’s current status in relation to both surroundings & thoughts Make person behavioural response appropriate for each occasion Relate environmental stimuli to coordinated behavioural autonomic & endocrine responses seen in species preservation Responses include: Feeding and drinking fighting behaviour Mating and maternal care Responses to physical or emotional stresses

28. 2. Limbic lobe Situated at infero -medial aspect of cerebral hemispheres Consists of two concentric gyri surrounding corpus callosum Broca proposed - larger outer gyrus - " limbic gyrus " smaller inner one " intralimbic gyrus ”. L imbic gyrus (limbic lobe) consists of I sthmus of cingulate gyrus P arahippocampal gyrus S ubcallosal area.

29. Gyri of the limbic system L imbic lobe of cerebral hemisphere consists of gyri & deeper structures that are adjacent to diencephalon . C ingulate (girdle or belt) gyrus sits superior to corpus callosum . D entate gyrus & parahippocampal gyrus conceal an underlying nucleus, the hippocampus

30. 3. Cingulate G yrus C ingulate gyrus & parahippocampal gyrus are in continuity with one another around the splenium of the corpus callosum

31. 4. Hippocampus lies deep in temporal lobe Role in learning & storage of long-term memories Infero -medial structure of para-hippocampal formation Hippocampus is divided into several zones of pyramidal cells:CA1 – CA 4 fields Tri-laminate structure Molecular Pyramidal Polymorphic S ensitive area in brain for Ischemic events in hippocampus is CA1 Stretches in a ‘C’ shape formation over the corpus callosum

32. Hippocampal Formation Consists of hippocampus,dentate gyrus & part of parahippocampal gyrus Formed by an infolding of inferomedial part of temporal lobe into lateral ventricle Dentate gyrus lies between parahippocampal gyrus & hippocampus Anteriorly= continues into uncus Converts recent memory to long term memory ( permits a link to previous experience; memory consolidation)

33. Inputs to Hippocampus Receives afferents from inferior temporal cortex via entorhinal area R eceives fibers from contralateral entorhinal area & hippocampus via fornix & hipoocampal commissure which consists of transverse fibers linking posterior columns of fornix on each side

34. 5. Fornix F ornix (arch) is a tract of white matter that connects the hippocampus with the hypothalamus From hippocampus , the fornix curves inferior to corpus callosum, & forms an arch that curves anteriorly, ending in the hypothalamus. Many of the fibers end in the mammillary bodies

35. 6. Mammillary bodies Nuclei in floor of hypothalamus . c ontain motor nuclei that control reflex movements associated with eating, chewing , licking & swallowing M ammillary body projects to a nuclear group of thalamus via mammillothalamic tract & to brainstem via mammillotegmental tract .

36. 7. Other components of limbic system N uclei of thalamus have connections with cingulate gyrus Several nuclei in wall (thalamus ) & floor (hypothalamus) of diencephalon are components of limbic system. A nterior nucleus of thalamus relays visceral sensations from the hypothalamus to cingulate gyrus . Experimental stimulation of the hypothalamus responsible for the emotions of rage, fear, pain, sexual arousal, and pleasure.

37. 8. Hypothalamus Stimulation of hypothalamus can produce heightened alertness & generalized excitement caused by widespread stimulation of reticular formation , an interconnected network of brain stem nuclei whose dominant nuclei lie within the mesencephalon. Stimulation of adjacent portions of hypothalamus or thalamus will depress reticular activity , resulting in generalized lethargy or actual sleep .

38. 9. Papez Circuit S eries of looped connections that project into hypothalamus Includes: subcalosal , cingulate, parahippocampal gyri , hipocampal formation, amygdaloid nucleus, mammilary bodies & anterior thalamic nucleus. Connecting pathway: Alveus , fimbria, fornex , mammilothalamic tract & stria teminalis

39. 10. Limbic Connections Entry of information to limbic system is either directly to amygdala Or indirectly to hippocampal formation , via the entorhinal area which is cranial extension of parahippocampal gyrus The limbic system, via hypothalamus & its connections with outflow of ANS & its control of endocrine system is able to influence emotional behavior (reactions to fear; anger; sexual behavior ) A ble to influence motor responses through projections to nucleus accumbens , which forms a part of the basal ganglia

40. 11. Basal nuclei Paired masses of gray matter within cerebral hemispheres. These nuclei lie within each hemisphere inferior to floor of the lateral ventricle embedded within central white matter . The radiating projection & commissural fibers travel around or between these nuclei. Consists of • Caudate nucleus • Lentiform • Putamen • Globus pallidus

41. Clinical Relevance

42. Kluver-Bucy Syndrome: damage bilateral temporal lobe i.e. damage amygdala (behavior & emotions) hence no emotional reaction- Placcidity ( fear,anger ) , Hyperplagia (eat a lot), hypersexual. It also damage hippocampus so amnesia (memory loss) Wernickes Encephalopathy: Vit . B1 deficiency & damage mammillary bodies (memory pathway) hence cause confabulation (vivid imagination-make stories). Vit B1 deficiency also damage middle cerebellar peduncles cause ataxia & damage 3 rd & 6 th Cranial nerve nucleus involved in extraocular movements ( opthalmoplasia )

43. Limbic Lobe D isorders If partial recovery occur , there is failure to remember previous experience (Retrograde amnesia) Or to learn new facts ( Anterograde amnesia –This state is called Korsakoff’s psychosis A mnesic syndrome occurs when bilateral, surgical temporal lobectomy including the hippocampal formations Temporal lobe lesion near the amygdala and hippocampi can lead to complex experiences of smell , mood , and memory. Surgical ablation of amygdala has eliminated uncontrollable rage reaction in some psychotic patients

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