1. Research by Wagner et al Presented by Daehan Choi

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 incident al word encoding in two whole-brain function-al magn etic resonance imaging (fMRI) studies.

6. Method/Results One experiment used blocked-design to investigate how systematic manipulation of the encod ing task affects prefrontal and medial temporal activatio n Another used newly developed event-related procedur es (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 fusiform gyri demonstrated greater activation during semantic processing. - BUT do not directly specify the encoding differences t hat predict whether a specific experience will be later r emembered or forgotten

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

11. Event Related fMRI Results Identified of regions that demonstrate differential activatio n during the encoding of words subsequently remembered and those subsequently forgotten Greater activation was noted in multiple left prefrontal region s and left parahippocampal and fusiform gyri The subsequent memory effect was rather specific: other regions active during word processing relative to fixat ion failed to demonstrate greater activation during high co nfidence hits relative to misses

15. Discussion Left prefrontal and temporal regions showed significa ntly greater activation for subsequently remembered it ems Remembering verbal items depends on the extent to which left prefrontal and medial temporal regions are engaged during the experience. The role of parahippocampal gyrus in memory encoding extends beyond novelty detection and enco mpasses more general encoding mechanisms

16. 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

17. Further Research Parahippocampal gyrus is the principal neocortical input pathway to the hippocampal region, and thus it i s 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

18. Questions?