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Episodic Memory

Old Taxonomy of memory (Tulving 1972)?. Types of memoryworkinglong-term(short-term)?explicit, declarativeimplicitepisodicsemanticproceduralperceptual(event)(fact)representionalTulving, Endel (1972). Episodic and semantic memory. Organization of

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Episodic Memory

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    1. Episodic Memory „Episodic memory is the form of memory that allows an individual to recollect happenings from his or her past.“ (Tulving, 1992)? Where does EM fit in the taxonomy of Memory systems?

    2. Old Taxonomy of memory (Tulving 1972)?

    3. Baddeley's (2000, 2003) memory model

    4. 2 senses of 'episodic' 1. Episodic memory task 2. Episodic memory system

    5. 1. The episodic memory task If it is not possible to retrieve information other than through recollecting a specific episode, a task is considered an EM task. „By this rule, conventional recall of and recognition tasks, in which the rememberer must produce the name, or identify as 'old', a copy of an item encountered on an earlier occasion in a particular situation, are classified as episodic.“ (Tulving, 1983, 55)?

    6. Varieties of EM tasks Free recall: Name the items in the study list Seriall recall: Name the items in their serial order Paired-associate task: What was the associate of the presented item? Cued recall task: Name the item from the list which is prompted by a retrival cue (e.g., rhyme, category)? Yes/No recognition task: Have you seen item X before? ... --> „Each of these tasks can be described in terms of the subject's earlier personal experience. This is why they are classified as episodic memory tasks.“ (Tulving, 1992)?

    7. 2. Episodic memory system What is the neurocognitive system sustaining EM? Such a neurocognitive system is supposedly specific to EM as opposed to other memory systems, e.g., semantic or procedural memory. Only by virtue of an intact brain system specialized for this purpose can we access EM.

    8. Time-scales of EM The typical EM tasks only tap on specific sections of the entire EM system, namely those on a micro- or medium time scale. The entire system also includes more long-lasting EM such as Long-term episodic memory sometimes called autobiographic memory, i.e., memories of (significant) personal past experiences such as 1st schoolday, marriage, accidents, etc.

    9. The novel Episodic Memory System The old EM Model of Tulving has been revised in the course of time. The change was conditioned, among others, by studies on young patients with anterograde amnesia due to hippocampal pathology, who, nevertheless, were able to acquire declarative (semantic) knowledge Endel Tulving and Hans J. Markowitsch (1998): Commentary. Episodic and Declarative Memory. Role of the Hippocampus. Hippocampus 8, 198-204. Vargha-Khadem, F., Gadian DG, Watkins KE, Connely, A, Van Paesschen W., Mishkin, M. (1997): Differential effects of early hippocampal pathology on episodic and semantic memory. Science, 277, 376-380.

    10. Affected Episodic Memory Spared Semantic Memory Such a dissociation argues against a unitary view of hippocampus as subserving both episodic and semantic M. (as, e.g., proposed by Squire)? Tulving claims, with Varga-Khadem, that the hippocampus is solely concerned with EM whereas other parts of the Medio-temporal lobe are associated with declarative memory. He comes up with a new division between declarative, semantic, and episodic M.

    11. The SPI Model (Tulving and Markowitsch 1998)?

    12. Similarities between declarative and episodic memory Semantic Declarative Episodic Memory

    13. 12 common features of declarative and EM. Both systems are... 1. large and complex, highly structured 2. take multimodal input 3. characterized by similar, fast, encoding OP 4. representational, 5. propositionally describable, symbolic 6. have truth value 7. accessible and expressible flexibly 8. serve as basis for inferences

    14. 12 common features continued... 9. Ops are context-specific 10. Ops are cognitive (not behavioral)? 11. products can be but do not have to be expressed in overt behavior 12. interact closely with other brain/behaviour systems (language, emotion, reasoning)?

    15. Uniqueness of EM 9 distinctive features. EM is... 1. a system that makes possible remembering of previous experiences 2. The only form of memory oriented towards the past 3. associated with autonoetic consc awareness 4. includes but goes beyond (sem.) knowledge of the world: remembering > knowing 5. its relations to semantic M are process-specific (see Serial Parallel Independent, SPI-Model)?

    16. 9 distinctive features continued 6. develops later than semantic M in young children (ca. 4 yrs)? 7. is more vulnerable (change, amnesia, age)? 8. probably unique to humans (?)? 9. associated with selective and unique cortical activity

    17. Memory systems for Sem M and Dec M EM Hippocampus Frontal Lobes, esp. right-frontal for specific episodic retrieval mode or retrieval attempt Decl M Rest of Medio-Temporal Lobe,e.g., perirhinal cortex

    18. The scope of Episodic Memory It took biological evolution a long time to build a time machine in the brain, and it has managed to do it only once, but the consequences have been enormous: By virtue of their mental control over time, human beings now wield powers on earth that in many ways rival or even exceed those of nature itself. It is difficult to imagine a marvel of nature greater than that. (Tulving 2002, p 20).

    19. Episodic Memory An event-related functional neuro-imaging perspective Michael D. Rugg and Richrd N.A. Henson (2002), In n Amanda Parker, Edward L. Wilding, and Timothy J. Bussey (Eds.), The cognitive neuroscience of memory. Encoding and retrieval. Psychology Press.3-37

    20. Event-related fMRI (efMRI)? efMRI allows for detecting the brain's response to brief stimuli, the 'events'. It detects the Blood Oxygenation Level Dependent (BOLD) haemodynamic response to neural activity. Spatial resolution: millimetres temporal resolution: hundreds of milliseconds

    21. Main Experimental Paradigm Yes-No recognition task: Learning phase: Subjects in the scanner are presented with a list of words Test phase: Subjects are presented with a new list including 'old' words but also 'new' words. Their task is to indicate which of the words are 'old' and which are 'new' During learning and test, their brain is scanned and regional blood oxygenation level is assessed

    22. 3 possible confounds 1. Preretrieval vs. Postretrieval processes: Preretrieval = attempt to use a cue to retrieve info Postretrieval= cognitive Ops after retrieval, e.g., maintenance in WM or evaluation 2. Process Impurity Hardly any retrieval task is process-pure, e.g., performance on word-stem cued recall is the result of both Episodic M and implicit M 3. Item- vs. State-related brain activity Item-specific: Activation reflects properties of the S State-specific: Activation reflects general engagement in a particular task

    23. 3 possible confounds -> Problem: Due to these confounds, one can never be sure what has caused activation in a particular brain area However, through efMRI, these confounds have been diminished

    24. Research Questions and procedures Which brain areas support Episodic M? Which are engaged in successful retrieval vs. Retrieval attempt? Which are engaged in distinguishing old vs. new words? Are there different sites for Remember/Know? Procedure: Yes/No recognition task Variant: Yes/No task with 'Remember' vs. 'Know'-judgements: Remember: whether a word was judged old on the basis of recollection of some aspect of the study episode (context)? Know: whether it was judged old solely on the basis of an acontextual sense of familiarity

    25. Brain regions sensitive to retrieval success in Episodic Memory 1. Prefrontal Cortex 2. Medio-temporal Cortex (Hippocampus, limbic system)? 3. Parietal Cortex

    26. Main regions sensitive to retrieval success in recognition studies 1. Left-anterior Prefrontal Cortex (PFC), Brodman Area (BA 10)? 2. left inferior and superior parietal cortex (BA 39/40)? 3. precuneus (BA 7/19/31) (part of the limbic system, above the subparietal sulcus)?

    27. Other regions sensitive to retrieval success in recognition studies 4. right anterior PFC (BA 10)? 5. left and right dorsolateral PFC (BA 9/46)? 6. left ventrolateral PFC (BA 47)? 7. right inferior and superior parietal cortex (BA 39/40)? 8. posterior cingulate (MTL) (BA 23/31)?

    28. Functional significance of activation Prefrontal Cortex, left anterior PFC (BA 10): More active for 'remember' than for 'know' responses for correctly recognised old items In this area, too, related 'lures' (semantically similar new words) are correctly rejected --> this brain area governs successful retrieval of stimuli with a highly episodic character. In other studies, left anterior PFC is also active when requesting a 'source' judgement for new items.

    29. Functional significance continued Prefrontal Cortex, right anterior PFC (BA 10): According to Tulving (Tulving & Markowitsch 1998), right anterior PFC is active when the brain is in the 'retrieval mode': 'a mental state in which environmental events are treated as retrieval cues, and retrieved episodic memories are experienced auto-noetically' (i.e., consciously)? --> rather state-related, not item-related Alternatively: both item-related and active in retrieval success also engaged in post-retrieval processes: correct classified old words instigate a delayed long-lasting positive wave over the right frontal scalp

    30. Functional significance continued Prefrontal Cortex, right anterior PFC (BA 10): Problem: Right anterior PFC shows atypical ERP responses, esp. delayed response latencies (after 3s) and prolonged time-course of activation.This pattern has been called 'right frontal ERP old/new effect'

    31. Functional significance continued Dorsolateral PFC (BA 9/40)? active when task demands exceed simple recognition, e.g., introspective judgements on recognition decisions (low vs. High confidence) are requested or judgement: true/false, irrespective of old vs. New items active in correct rejection of new words having been assembled from parts of old words --> responsible for post-retrieval processes including monitoring

    32. Functional significance continued 2 different kinds of retrieval processes: 1. left anterior PFC (BA 10)? active in successful retrieval of old words 2. Dorsolateral PFC (BA 9/40)? operates on the products of a retrieval attempt regardless of the amount or the nature of the information retrieved (old and new)?

    33. Functional significance continued left ventrolateral PFC (BA 47)? --> sensitive for encoding of semantic and phonological stimuli --> engaged in successful cue processing, if cues receive a sufficiently full semantic analysis --> task specific: engaged in direct recognition but also in indirect priming memory

    34. Functional significance continued Lateral and Medial Parietal Cortex (BA 39/40)? mainly left-lateralized, mainly in the inferior part (BA 40) than in the superior part (BA 7, parietal gyrus)? more active for remember > know judgements --> correlate of successful recognition of items with episodic character, irrespective of retrieval task In ERP studies, this correponds to 'left parietal old/new effect' which consists in a positive shift after 400-500 ms post-stimulus and which is maximal over the left-parietal scalp

    35. Functional significance continued Medial Parietal Cortex (BA 40)? well-recognized role in visual imagery: if this area is active in successful recognition, this proves the visual demands of visual imagery in episodic memory retrieval processes

    36. Functional significance continued Medial Temporal Lobe (MTL)? Only 3 of the many efMRI studies report retrieval-related activation of the hippocampus and adjacent medio-temporal cortex, esp. for items likely to have exhibited strong episodic memory. --> hippocampal activity is related to (strong) episodic M

    37. Functional significance continued (MTL), Hippocampus Contradiction: why is the hippocampus not generally involved in these episodic M tasks? --> the standard Yes/No recognition task is NOT process-pure, i.e., recollection of old items can be mediated by acontextual general facilitatory effects without hippocampal activation (2nd picture: blue)which is especially geared to contextual information in episodic recall Familiary is processed in the perirhinal cortex (ventral and anterior to hippocampus, 2nd picture: pink)?

    38. Functional significance continued (MTL), Hippocampus Contradiction: why is the hippocampus not generally involved in these episodic M tasks? --> could be a restriction of efMRI to detect such metabolic changes --> could be that hippocampus is involved in both encoding ('new' words) and retrieval ('old' words) so that no difference in activation is found and hence hippocampus does not figure prominently in these kinds of tasks although it is actually highly involved

    39. References Baddeley, Alan D. (2000): The episodc buffer: a new component of working memory? Trends in Cognitive Sciences, 4, 417-423. Baddeley, Alan D. (2003): Looking back and looking forward. Nature Reviews Neuroscience, 4, 829-839. Rugg, Michael D. And Henson, Richard N.A. (2002): Episodic memory retrieval: An (event-related) functional neuroimaging perspective. In Amanda Parker, Edward L. Wilding, and Timothy J. Bussey (Eds.), 3-37 Tulving, Endel (1983): Elements of episodic memory. Oxford: Clarendon Press. Tulving, Endel (1992): Episodic memory. In Larry Squire (ed.), Encyclopedia of learning and memory. NY: Macmillan Publishing Group, 161-63 Tulving, Endel (2002): Episodic Memory: From Mind to Brain. Annual Review of Psychology, 53: 1-25.

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