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  1. 1. Memory A specific cognitive function, the storage and retrieval of information 新光醫院 R2 黃彥瑜 103-05-08
  2. 2. Introduction • Limbic system • Regulate autonomic and endocrine function, particularly in response to emotional stimuli • Set the level of arousal and dreaming • Motivation and addiction • Olfactory system • Appetite and eating behaviors • Sexual behavior • Memory and learning
  3. 3. History • Broca, 1878: le grand lobe limbique • Papez circuit, 1937: took as emotional feeling and expression • Kluver-Bucy syndrome (in bilateral temporal lobectomy…): amnesia, docility, dietary changes/hyperphagia, hyperorality, hypersexuality, visual agnosia, hypermetamorphosis • MacLean, 1952: limbic system, extensively including parahippocampus, entorhinal cortex…
  4. 4. • Hippocampus for Emotion → Memory • LeDoux, 1986: Amygdala for Emotion • Fear, rage, aggression • Emotional reactions accompanied by autonomic reactions
  5. 5. • Pessoa, 2008 • 'affective' and 'cognitive' brain ? • Amygdala in the domain of emotion • Lateral prefrontal cortex in the case of cognition • Complex cognitive–emotional behaviors have their basis in dynamic coalitions of networks of brain areas, none of which should be conceptualized as specifically affective or cognitive.
  6. 6. Neuroanatomy • Consisted of archicortex, paleocortex and neocortex • Components of the limbic systems: no universal agreement on the total list of the structures • Cortical regions (limbic lobe): surrounding cortex including insular cortex, orbital frontal cortex, subcallosal gyrus, cingulate gyrus, parahippocampal gyrus • Hippocampal formation • Subcortical portions: olfactory bulb, hypothalamus, amygdala, septal nuclei, thalamic nuclei
  7. 7. Papez circuit • Hippocampus • Fornix • Mamillary body • Mammillothalamic tract • Anterior nucleus of the thalamus • Thalamocingulate tract • Cingulate gyrus • Parahippocampal gyrus • Hippocampus
  8. 8. Hippocampus • Hippocampus proper (Ammon’s horn, cornu Ammonis) • CA1, CA2, CA3, (CA4) • Dentate gyrus (fascia dentata)
  9. 9. • The functions associated with the limbic system, such as instinctual and affective behavior, motivation, and drive, as well as learning and memory should not be thought of as preserve of the limbic system alone • These functions depend on an intact cooperation of the limbic system with many other areas of the brain
  10. 10. Connectionstootherareasofthebrain • Papez circuit • Entorhinal afferent fibers • “Gateway” to hippocampus • Septal, hypothalamus afferent fibers • Afferent fibers from brainstem • Commissural afferent fibers • Connect the two hippocampi with each other • The major efferent bundle of the hippocampal formation: fimbria, fornix • Autonomic nervous system can travel through the hypothalamus and the medial dorsal nucleus of the thalamus to reach the orbitofrontal cortex • Amygdala, mammillary bodies……
  11. 11. • The following fiber pathways are particularly important for (declarative) memory: • Projections from the hippocampus by the way of the fornix • To the septal nuclei • To the mamillary bodies (Papez circuit) • Projections from the amygdala to the dorsomedial nuclear of thalamus and onward to the orbitofrontal cortex -Duu’sTopical Diagnosis in Neurology- ?
  12. 12. 記憶如何形成? • “Grandmother cell” • Jennifer Aniston cell • Visual invariance • Concept cells • 18000 neurons/each concept • Interpretation: 非回憶起事物 所需的細胞,而是把事物置入意 識以便形成新的連結和記憶所 需的細胞 • Sparse vs. Ddistributed
  13. 13. Long-term potentiation
  14. 14. Bloodsupply of hippocampus • The PCA directly and by its branches ontributes much more to the blood supply of the hippocampal formation than the anterior choroidal artery (AChA).
  15. 15. Stages of memory • Encoding or registration: receiving, processing and combining of received information • Consolidation • Storage: creation of a permanent record of the encoded information • Retrieval, recall or recollection: calling back the stored information in response to some cue for use in a process or activity
  16. 16. Where do they work • According to an early positron emission tomography (PET) study, several brain regions show consistent activation in normal subjects during memory testing. • A model for the functions of these areas in memory are as follows: • Prefrontal cortex: retrieval activation and attention • Hippocampi: conscious recollection • Cingulate cortex: activation of memory and selection of a specific response • Posterior midline regions: visual imagery • Parietal cortex: spatial awareness • Cerebellum: voluntary self-initiated retrieval • Lateralization: left for word semantic memory, right for nonverbal memory
  17. 17. • Medial temporal cortex activates more during new learning tasks than during previously trained and practiced memory tasks • Overlearned memories gradually become less dependent on the hippocampus. • The amygdala appears necessary for affective aspects of memory items, such as recall of fear associated with a specific stimulus • Amygdala is not essential for episodic memory but crucial for recall of emotional contexts of specific events and the reactions of fear or pleasure
  18. 18. Afilinganalogyof episodicmemory • Frontal lobes: filing clerk, deciding what memories to file or retrieve • Medial temporal lobes: recent memory filing cabinet, memories consolidated • Diffuse cortical regions: remote memory file cabinet
  19. 19. Stages of memory • Encoding or registration: receiving, processing and combining of received information • Consolidation • Storage: creation of a permanent record of the encoded information • Retrieval, recall or recollection: calling back the stored information in response to some cue for use in a process or activity Frontal lobe Prefrontal lobe Hippocampus Hippocampus (Papez circuit) Hippocampus Diffuse cortex Frontal/Prefrontal lobe Hippocampus Diffuse cortex
  20. 20. Typesof memory • Primary vs. Secondary memory • Short-term vs. Long-term memory • Explicit vs. Implicit memory
  21. 21. Classifiedby time • Working memory, immediate memory span • A subject can keep in conscious awareness without active memorization • Seven digits • Supraspan numbers or reverse digit span require active memory processing • Disorders of attention and very focal lesions of the superior frontal neocortex (Brodmann areas 8 and 9) affect immediate memory
  22. 22. • Recent memory • The ability to register and recall specific items after a delay of minutes or hours • 3 objects recall test, questions about morning breakfast • Remote memory • Recall of famous figures or events, knowledge
  23. 23. SMA
  24. 24. • Episodic memory: the memory of autobiographical events that can be explicitly stated • Semantic memory: the memory of meanings, understandings, and other concept-based knowledge, and underlies the conscious recollection of factual information and general knowledge about the world • Procedural memory: memory for the performance of particular types of action • Classical conditioning: an unconditioned stimulus becomes associated with a reward or punishment given when the conditioned stimulus is presented • Probabilistic classification learning: predicting the weather from a combination of cues that are regularly associated with sunny or rainy weather • Priming: a prior encounter with a particular item changes how one responds to the current item, even unconsciously • Perceptual priming: modality specific based on different sensory cortex • Conceptual priming: “school" relates to "student“
  25. 25. Memorydisorders:amnesticsyndrome
  26. 26. Korsakoffsyndrome • Chronic alcoholic patients who develop thiamine deficiency • Acute:Wernicke’s encephalopathy • Symptoms: • Dementia especially amnesia, anterograde and retrograde • Confabulation, anosognosia, apthy • MRI: tectal plate, periaqueductal area, mammilary bodies, dorsomedial thalamic nuclei, hypothalamus
  27. 27. Posttraumaticamnesia • Diffuse brain pathology, in particular rotational forces giving rise to diffuse axonal injury • Transient or persisting amnesia, anterograde or retrograde • Islands of memory • Memory is commonly the last cognitive function to show improvement, usually expected 1-3 months after the injury • Coexisting psychogenic disorders: posttraumatic stress disorder
  28. 28. Herpes simplexencephalitis • Bilateral temporal lobe encephalitis is pathognomonic • Symptoms: signs of meningitis/encephalitis, seizures
  29. 29. Transientglobal amnesia • Acute loss of memory, usually recover spontaneously within 12-24 hours • Middle aged or elderly, men • Symptoms: repetitive questioning (short term memory, mainly anterograde), disorientation, no other neurologic signs • Etiology: may be ischemic (subtle transient intense DWI signal seen within the hippocampus) • Need to differential with vascular events and seizures
  30. 30. Transientepilepticamnesia • Brief episodes of memory loss (1h or less) and multiple attacks may suggests epilepsy • May be residual deficits between each attacks, other signs of seizures (automatism, postictal confusion) • Anterograde amnesia or memory gaps • Standard EEG and CT are often normal
  31. 31. Vasculardisorders • Thalamic infarction • Hemorrhage or infarction of the septal nuclei • SAH following rupture of an aneurysm: ACA or PCA • Lesions of the splenium of the corpus callosum, either traumatic or ischemic, which commonly also involve the immediately underlying commissure of the fornices
  32. 32. Alzheimerdisease • Neurodegenerative disease • The most common disease that affects the episodic memory system: the hippocampus and other medial temporal lobe structures are damaged first • Affect episodic memory mainly • Distortions of memory • Ribot’s law: ability to learn new information is most impaired (anterograde amnesia), recent learned information cannot be retrieved (retrograde amnesia), remotely learned information is spared
  33. 33. Thanks for attention • Reference: • Duu’sTopical Diagnosis in Neurology • Bradley’s Neurology in Clinical Practice • Microsurgical anatomy of the hippocampal arteries (J Neurosurg 79:256-265, 1993) • The limbic system (Indian J Psychiatry. 2007 Apr- Jun; 49(2): 132–139.) • Disorders of memory (Brain (2002), 125, 2152±2190) • Memory: Clinical Disorders - Boston University Students • 科學人 NO.134 • i/chapter_9.html • •