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Research by Wagner et al Presented by Daehan Choi

Building Memories : Remembering and Forgetting of Verbal Experiences as Predicted by Brain Activity. Research by Wagner et al Presented by Daehan Choi. The Big Picture - Memory Encoding. How come we remember some things and forget others? Neurological basis?

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Research by Wagner et al Presented by Daehan Choi

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  1. Building Memories:Remembering and Forgetting ofVerbal Experiences as Predicted by Brain Activity Research by Wagner et al Presented by DaehanChoi

  2. The Big Picture - Memory Encoding • How come we remember some things and forget others? • Neurological basis? • Differences in brain activation? • WHAT IS GOING ON IN THE BRAIN?

  3. Memory Encoding • What is Memory Encoding? • processes by which an experience is transformed into an enduring memory trace. • influenced by the cognitive operations engaged during initial encoding of that experience • semantic processing leading to superior memorability relative to nonsemantic processing

  4. Previous Functional neuro-imaging • Left prefrontal activation in verbal tasks • greater during semantic relative to nonsemantic verbal task • Activation decreases and memorization is impaired when semantic encodings are disrupted SO BASICALLY LOOKING PROMISING THERE

  5. Objective of the Study • The study examines the neural correlations of incidental word encoding in two whole-brain function-al magnetic resonance imaging (fMRI) studies.

  6. Method/Results • One experiment used blocked-design • to investigate how systematic manipulation of the encoding task affects prefrontal and medial temporal activation • Another used newly developed event-related procedures (ERP) • allow direct comparison between specific encoding trials that result in subsequent remembering and forgetting.

  7. Blocked Design Experiment • Activation during a semantic processing task was compared to that of nonsemantic • semantic task (deciding if a word is abstract or concrete) • nonsemantic – lower or upper letters • 12 right handed normal subjects • alternating semantic, nonsemantic, and visual fixation • novelty of the words in the semantic/nonsemantic equal

  8. Blocked Design Experiment Results • Reaction times were longer for semantic (873ms) than nonsemantic (539) • Subsequent memory superior following semantic (85% recognized) than nonsemantic (47%) • Regions in left prefrontal cortex and fusiformgyri demonstrated greater activation during semantic processing. - BUT do not directly specify the encoding differences that predict whether a specific experience will be later remembered or forgotten

  9. Event Related fMRI • Single incidental encoding task • to determine whether trial-by-trial differences in encoding activation predict subsequent memory for experiences even when the processing task was held constant. • 13 normal, right handed subjects underwent six fMRI scans • each presented with 120 rapidly intermixd trials • later tested on recognition test • high confidence hits, low confidence hits, misses, and fixation

  10. Event Related fMRI Results • Identified of regions that demonstrate differential activation during the encoding of words subsequently remembered and those subsequently forgotten • Greater activation was noted in multiple left prefrontal regions and left parahippocampal and fusiformgyri • The subsequent memory effect was rather specific: other regions active during word processing relative to fixation failed to demonstrate greater activation during high confidence hits relative to misses

  11. Discussion • Left prefrontal and temporal regions showed significantly greater activation for subsequently remembered items • Remembering verbal items depends on the extent to which left prefrontal and medial temporal regions are engaged during the experience. • The role of parahippocampalgyrus in memory encoding extends beyond novelty detection and encompasses more general encoding mechanisms

  12. My thoughts • Strengths • Very concise and precise • Two experimental designs to tackle the question effectively • Discovering the novel function of temporal regions in verbal memory • fMRI scans • Limits • Small sample size (12~13) • Only focused on verbal memory encoding

  13. Further Research • Parahippocampalgyrus is the principal neocortical input pathway to the hippocampal region, and thus it is suitably situated to play an important role in memory formation further investigation of the circuitry using direct inhibition or agonists. Further research in non-verbal memory tasks

  14. Questions?

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