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Interactions Between Forms of Memory: When Priming Hinders New Episodic Learning. Anthony D. Wagner, Anat Maril, and Daniel L. Schacter Journal of Cognitive Neuroscience, 2000. Wei-Chung Lee April 25, 2001. Forms of Memory. Long Term Memory. Explicit (Declarative).
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Interactions Between Forms of Memory:When Priming Hinders New Episodic Learning Anthony D. Wagner, Anat Maril, and Daniel L. Schacter Journal of Cognitive Neuroscience, 2000 Wei-Chung Lee April 25, 2001
Forms of Memory Long Term Memory Explicit (Declarative) Implicit (Non-declarative) Semantic (Facts) Episodic (Events) Priming Procedural Associative Learning Nonassociative Learning Emotional responses Skeletal musculature Medial temporal lobe Neocortex Striatum Amygdala Cerebellum Reflex pathways
Long Term Memory Explicit (Declarative) Implicit (Non-declarative) Semantic (Facts) Episodic (Events) Priming Procedural Associative Learning Nonassociative Learning Emotional responses Skeletal musculature Medial temporal lobe Neocortex Striatum Amygdala Cerebellum Reflex pathways Motivation • When and how do these different forms of memory interact? ?
Episodic Memory • Explicit memory for conscious recollection of events from past experience Buckner and Koustaal, 1998
Perceptual Repetition Priming • Facilitation derived from repeated exposure to a stimulus Buckner et al., 1998
Long Term Memory Explicit (Declarative) Implicit (Non-declarative) Semantic (Facts) Episodic (Events) Priming Procedural Associative Learning Nonassociative Learning Emotional responses Skeletal musculature Medial temporal lobe Neocortex Striatum Amygdala Cerebellum Reflex pathways Hypothesis • Priming for past experiences can hinder new episodic encoding.
Predictions • Enhanced behavioral and neural priming during re-encoding with a shorter (2 min.) relative to a longer (25 hr.) lag between two encoding episodes. • Impaired long-term retention of episodic memory in conditions with greater behavioral and neural priming. • Lag Effect: shorter lags between repetitions deleterious to explicit memory (Ebbinghaus, 1885).
Experimental Procedure • Varied temporal lag between initial and repeated encoding episodes with words.
Behavioral Priming • Mean median Reaction Times (RTs) for Abstract/Concrete decision (msec). • Once-presented: 777 • Long-Lag: 763 • Short-Lag: 720 * ** ** ** * p < 0.09** p < 0.0001
Neural Correlates of Episodic encoding and Repetition Priming Once-presented > Fixation Once-presented > All Re-encoding • A subset of regions activated by episodic encoding demonstrate a significant repetition priming effect (i.e.. decrease in activation): anterior-LIPC, posterior-LIPC, and left fusiform cortex.
Lag Effects on ROI Activation • Long-Lag > Short-Lag • Priming also effects activation in left frontal operculum, left middle frontal, and medial frontal regions (Data not shown) • Greater neural correlate of priming during re-encoding following a shorter temporal lag rather than long
Explicit Memory • Explicit memory scores = (pHit - pFalse alarm) • Overall (High & Low Confidence) pHit • Long-Lag 35% 77% • Short-Lag 31% 73% • Once-Presented 22% 64% • “High Confidence” explicit memory • Long-Lag 32% 46% • Short-Lag 25% 38% • Once-Presented 17% 30% * ** ** ** ** ** * p < 0.005** p < 0.0001
Priming Negatively Correlates with Subsequent Explicit Memory • A negative association across-subjects between behavioral & neural (posterior & anterior-LIPC shown) priming and subsequent explicit memory. • Reliable correlations not found for Short-Lag trials(highest levels of priming led to lowest levels of “High Confidence” => range too small)
Conclusions • Correlation of behavioral and neural measures of priming during the re-encoding of a stimulus and impaired episodic encoding. • “cross-talk” between implicit and explicit forms of memory. • Posited mechanism: Priming reduces “encoding variability” or multiple retrieval routes increasing the probability that same task-relevant stimulus features ...
Implications & Questions • Consolidation? Time course of Lag Effect; optimal time to re-encode? • Attention? • 1 L neocortex 1x106 neurons 1x109 synapses and 1 voxel • Segregation of memory types justified? • Activation maps show significant differences in Blood Oxygenation Levels. • Encoding versus re-encoding • Not encoding/re-encoding the same words between sessions - may evoke different “meanings”/saliencies.