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Remembering and Forgetting

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  1. Remembering and Forgetting Cognitive Neuroscience

  2. Learning and Memory Two kinds of knowledge: • Hard-wired • Learned (memories) “Learning is the process of acquiring new information, while memory refers to the persistence of learning in a state that can be revealed at a later time” (Squire) The study of how the brain remembers is largely a study of how the brain learns; memory systems reflect learning systems.

  3. Distinctions in memory • Time scale of storage: • Sensory memory • Short-term memory (STM) –working memory • Long-term memory (LTM) • Types of memory (knowledge): • Procedural/declarative • Implicit/explicit • Stages of memory • Encoding • Storage-consolidation • retrieval

  4. Time-Scale: Sensory Memory • Information available for brief periods, over-ridden by incoming info • Visual: iconic (500 ms) • Auditory: echoic (several seconds) • Evidence: full/partial report

  5. K L N R S J H M T W Q X P B V

  6. X X X X X X X X X X X X X X X

  7. P H V K S T J M R V Q Z B L W

  8. X X X X X X X X X X X X X X X

  9. H.M.Scoville & Milner (1957)-etc. • Bilateral medial temporal lobectomy (hippocampi) • Age 29 to alleviate chronic, severe epilepsy • Normal IQ

  10. H.M.Scoville & Milner (1957) • Normal digit span (7 +/-2)-a test of STM • Despite normal STM, if the examiner left the room he would not remember ever having met the person or performed the task • Effects of learning persist temporarily, can create new short-term but not long-term memories • Supports the distinction between STM/LTM

  11. K.F.Shallice & Warrington (1970) • 28 years old • Left parieto-occipital damage following a motorbike accident at age 17 • Normal IQ • Normal memory ability otherwise • Digit span=1 • HM and KF provide a double dissociation of STM/LTM • Why is a double dissociation useful?

  12. Courtney, et al., 1997

  13. H.M.Scoville & Milner (1957) • H.M.’s recall of old memories is relatively intact • His memory performance represents a distinction between types of learning or formation of newmemories (new STM vs. new LTM) • anterograde/ retrograde amnesia • Anterograde: loss of ability to create new lasting memories • Retrograde: loss of ability retrieve old memories

  14. Types of LTM memory: Procedural/Declarative H.M. • not all types of new, long-term memory creation were affected • Motor procedures

  15. Types of memory: Procedural/Declarative H.M. • cognitive procedures

  16. Types of Knowledge:Procedural vs. Declarative • Procedural: knowledge of processes (motor, perceptual or cognitive) • Declarative: knowledge of facts and events (knowledge “that”) • Episodic: knowledge of specific personal experiences, their content, time place • Semantic: world, word knowledge

  17. Types of Memory or Memory Retrieval: Implicit/Explicit • Implicit: knowledge that can be retrieved without conscious recollection • Explicit: knowledge that can be retrieved only with conscious recollection • Neurologically intact individuals (as well as amnesics) show many dissociations in terms of implicit/explicit memory abilities

  18. Types of Memory or Memory Retrieval: Implicit/Explicit Subjects report digits were presented in completely random sequences, altho RTs to repeating sequences become faster as compared to random sequences

  19. Priming: memory retrieval of an item is facilitated by prior processing

  20. Memory stages • Encoding • Consolidation/storage • Retrieval • HM—difficulties specifically in consolidation • Although his amnesia was primarily anterograde, there was a retrograde component

  21. Memory Stages:Consolidation • Retrograde amnesia: • Focal retrograde amnesia: primary deficit is a loss of remote memory • Graded retrograde amnesia: memory loss inversely related to time of learning  implies consolidation

  22. Memory Stages:Consolidation • Korsokoff Syndrome: • long-term alcohol abuse leads to vitamin deficiences that cause brain damage-diencephalic (dorso-medial thalamic nucleus, mamillary bodies, MTL, frontal) • Shows similar profile as hippocampal lesions

  23. Neural Bases • Neocortex: • creating new procedural memories • Implicit memory retrieval • MTL and diencephalon (thalamus & mamillary bodies): • Creating and consolidating declarative memories • Explicit memory retrieval • Frontal lobes: • Encoding and Retrieval

  24. Two learning systems: neorcortical and hippocampal Neocortex: learns slowly, by making small adjustments to connections among neurons allows integration into complex knowledge structures Hippocampus: learns quickly supports rapid, one-trial learning during consolidation serves as “teacher” to the neocortex, until neocortical connection changes are robust Priming Implicit learning and retrieval Procedural knowledge Declarative knowledge Explicit learning and retrieval McClelland, McNaughton & O’Reilly (1995)

  25. Frontal Lobes • Damage is associated with high false recognition rates (false memories)

  26. False memories Tired Bed Awake Rest Dream Night Blanket Doze Slumber Snore Peace Yawn Drowsy

  27. False memories Tired Pillow Butter Sleep Day Dream

  28. Frontal Lobes • Damage is associated with high false recognition rates (false memories) • Work is ongoing to understand to what extent this is due to encoding or retrieval failures (or both) • If encoding failure: expect improvement with instructions and strategies for more efficient encoding • If retrieval failure: expect improvement with instructions for more stringent retrieval criteria

  29. False Memories • Lest you be overconfident: “In a 1992 op-ed piece for the New York Times, Garry Trudeau recollected some of his experiences related to the draft for the Vietnam War. Trudeau remembered receiving calls of concern from friends and family on the night of the draft lottery, after they had heard about his low number. He then recalled a series of events involving his attempts to gain a draft deferment: requesting a national security deferment from the draft board for his work with a magazine; deciding not to apply for conscientious objector status because he could imagine circumstances in which he would take another’s life; preparing for his interview with the draft board by receiving a “memorable haircut”; and finally, gaining a medical deferment from the board after sending them, upon his physician father’s advice, X-rays revealing a past ulcer. This recollection, he reported, remained unchanged for 20 years. However, after talking to others and examining the records of his draft correspondence, Trudeau uncovered some notable discrepancies between his recollection and what actually happened. No family member or friend remembers making a call of concern. Trudeau now believes he imagined their concerns, because the act ov examining this recollection led him to remember that he was in fact out having a few beers that night. He discovered that he actually applied for an occupational deferment and, upon reflection, wonders how he could have believed that working for a “glorified travel magazine” was justification for a national security deferment. He also neer received a “memorable haircut”, not did he apply for conscientious objector status in part because of the prohibitive paperwork” (Dodson & Schacter)

  30. False Memories “To what extent is the life we remember the knowledge and expectations we have, and the self we seem to ourselves to be, a product of experience and to what extent a product of our imagination?” (Johnson, 1985)