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Limbic System

Limbic System. Outline 1. Overview 2. Main Components Hypothalamus Prefrontal Cortex Cingulate Cortex Olfactory Cortex Amygdala Septal Region Hippocampus. Limbic System General Description. Structural

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Limbic System

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  1. Limbic System Outline 1. Overview 2. Main Components Hypothalamus Prefrontal Cortex Cingulate Cortex Olfactory Cortex Amygdala Septal Region Hippocampus

  2. Limbic SystemGeneral Description Structural A set of interconnected nuclei in the telencephalon and diencephalon and associated cortex Functional Functions in species preservation, emotional behaviors, and self identity, including emotion, motivation, and memory, olfaction processing, and neuroendocrine/autonomic regulation

  3. Main Components • Olfactory Bulb • Hypothalamus • Nuclei • Amygdala, Septal Nuclei, Anterior Nucleus Thalamus • Cortex • Orbital prefrontal • Allocortex • Hippocampus, Piriform olfactory cortex • Visceral neocortex • Insular, Orbitofrontal, Subcallosal, Cingulate, Parahippocampal-entorhinal cortex, Piriform olfactory cortex

  4. Limbic Structures

  5. Limbic SystemProcessing • Common Output System • Septal Nuclei, Hypothalamus, and midbrain RF+PAG • Connected via Medial Forebrain Bundle • Input and Processing • Orbitomedial prefrontal cortex • Hippocampus • Connections to parahippocamalgyrus, cingualtegyrus, mamillary body, and ant. thalamic nucl. • Amygdala • Connection to prefrontal, ant. Temporal cortex, and dorsomedial nucleus thalamus

  6. 2a. Hypothalamus(“Output”)

  7. Hypothalamus

  8. Hypothalamus • Limbic Output System • Inputs • Septal Nuclei • Via medial forebrain bundle • Amygdala • Via ventral amygdalofugal path and stria terminalis • Orbital frontal cortex (prefrontal) • Via medial forebrain bundle

  9. 2bLimbic cortex

  10. Limbic Cortex • Main components • Prefrontal Cortex • Cingulate cortex • Olfactory cortex • In charge of “subjective experience”, assignment of value, how we should react to things

  11. 2b.1. Prefrontal cortex

  12. Pre-frontal cortex(areas 9, 10, 11, 12) • General Function • Insight, motivation, judgement, mood • Affective aspects of “conditioned emotional reactions • Substructural functionality • Dorsolateral PFC (9,10) • EXECUTIVE FUNCTIONS • Planning, initiationg, working memory, abstract thought, divided attention • Orbital and medial PFC (11,12) • Mood, motivation, reactivity, “personality”, emotional control 133

  13. Pre-frontal cortex • Afferents • Cingulate cortex • Mesial temporal cortex • DM of thalamus • Efferents • Other Cortical lobes (esp. temporal - amygdala) • Via association bundles • Uncinate fasciculus • Mesial temporal cortex • DM of thalamus Medial Forebrain Bundle Uncinate fasciculus

  14. Pre-frontal cortex • Lesions: • Difficulty solving puzzles, abstract reasoning, judgement, moods (r. hemisphere-apathy; l. hemisphere-euphoric; rude, tactless, incosiderate behavior.

  15. 2b.2. Cingulate cortex

  16. Cingulate cortex • General Function • Areas are involved in depression • Increased activity anteriorly, decreased in posterior cingulate • Involved in perception of pain • Most active on the border of pain in trying to decide how to act

  17. 2b.3. Olfactory cortex and pathways

  18. Olfactory cortexand Pathways • Input • Receptor cells  bulb glomeruli  mytral cells  olfactory tract axons to: • Olfactory Cortex • Olfactory tubercle (@ ant. Perforated substance) • Piriform cortex (@rostral uncal surface) • Medial amygdala (@interior uncus) Olfactory tubercle Piriform cortex Medial amygdala (within uncus0

  19. Olfactory cortexand Pathways • Mediodorsal (MD) Nucleus Thalamus • Afferent olfactory from: ventral pallidum, ant. perf. subs., & piriform cortex • Efferents to : orbitofrontal cortex • Ventromedial (VM) Nucleus hypothalamus • Afferent olfactory from: medial amygdala via stria terminalis VM Hypothalamus MD Thalamus

  20. 2c. Amygdala

  21. Amygdala • General Function • Relate: environmentral stimulie to coodinate 1) behavioral, 2) autonomic, and 3) endocrine responses • “Animal behaviors”: feed, drink, fight, mate, maternal care, response to stressors • Emotional memory • e.g., stimulation produces attention and directed rage responses Amygdala

  22. Amygdala • Afferents (~all reciprocal) • Olfactory tract (OLF) • Solitary and parabrachial nucleus (B) • Limbic neocortex (es. Mesial temp and frontal) (OF) • Thalamus (T) • Septal nucleus (S), hypothalamus (H) • Sensory and association areas of cortex CG T H S OF Olf Hip & PHG B

  23. Amygdala • Efferents (reciprocal except olfactory) • Hypothalamus • Via 1) stria terminalis & 2) ventral amygalofugal pathway • Limbic neocortex • Via MD thalamus • Autonomic centers • Central gray, parabrachial nucleus, solitary nucleus, dorsal motor nucleus of vagus, sympathetic preganglionic cells in IML CG T H S OF Hip & PHG B

  24. Amygdala • Conditioned Fear Response • Sensory inputs to amygdala

  25. Amygdala • Kluver Bucy syndrome (bilateral lesions of temporal lobe, incl. neocortex, olfa. Cortex, amygdala, hippocampus): • Hyperorality, hypersexuality, docile

  26. 2d. Septal Region

  27. Septal Region • General Function • Involved in sexual drive • Neuroendocrine regulation of reproductive behaviors via GnRH projection to median eminence • Reward area of the brain • Associated with memory functions via connection to hippocampus

  28. Septal Region

  29. 2e. Hippocampus

  30. Hippocampus • Location • Medial aspect of temporal lobe, forming medial wall of lateral ventricale (left and right) • Associated with memory functions via connection to hippocampus

  31. Hippocampus Fimbria of fornix • Afferents • Entorhinal cortex • -MAJOR INPUT • -Adjacent to parahippocampus gyrus • -Entorhinal  Dentate gyrus (via perforant path) • -Projections from: most of neocortex (incl. limbic such as cingulate, orbital, temporal association, amygdala) • Septum • Hypothalamus • -Via fornix Pyramidal cells Schaefer collaterals Granule cells CA4 Dentate gyrus Mossy fibers CA1 Perforant path Alvear path Entorhinal part of Parahippocampal gyrus Subiculum

  32. Hippocampus Fimbria of fornix • Efferents • Fornix • -Pre-commissural: septal nuclei, preoptic area, ventral striatum, orbital cortex, subcallosal cortex • -Post-commissural: to ant. Nucl. Of thalamus, mammillary bodies • -CA fields and subiculum • Reciprocal to entorhinal cortex Pyramidal cells Schaefer collaterals Granule cells CA4 Dentate gyrus Mossy fibers CA1 Perforant path Alvear path Entorhinal part of Parahippocampal gyrus Subiculum

  33. Hippocampal Connections Fornix Brain stem & spinal cord Hypothalamus Septal nuclei Ventral amygdalofugal pathway Stria terminalis Olfactory bulb & piriform cortex Amygdala Hippocampus Limbic cortex Diverse association cortex Entorhinal cortex

  34. Hippocampus • Functions • Declarative memory • Mapping the environment • Movement • Glucocorticoid hormonal control

  35. Forms of Long Term Memory Two forms of long term memory Explicit (declarative) Implicit (nondeclarative) Nonassociative learning (habituation & sensitzation) Priming Procedural (skills, habits) Associative learning (classical & operant conditioning) Facts (semantic) Events (episodic) Emotional responses Skeletal muscles Medial temporal lobe (hippocampus, parahippocampal gyrus) Reflex pathways Neocortex Striatum Amygdala Cerebellum

  36. Explicit Memory Polymodal association cortex (Dorsolateral prefrontal, limbic, parieto-occipito-temporal) Parahippocampal gyrus Parahippocampal gyrus Entorhinal cortex Entorhinal cortex Dentate gyrus Subiculum Hippocampus

  37. Hippocampal Encoding and Recall Hippocampus active in recall as well as encoding

  38. Long Term Memory Ultimately, memory storage is transferred to other association cortical sites that may be dependent on the characteristics of the memory

  39. 2f. Mesolimbic

  40. Mesolimbic • Dopaminergic Brain Pathways • “REWARD PATHWAY” • VTA to nucleus accumbens, hippocampus, amygdala, and prefrontal cortex and D3 receptors

  41. Mesolimbic • Drug abuse and schizophrenia

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