1. 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

2. 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

3. Motivation ? When and how do these different forms of memory interact?
Long Term Memory
Explicit (Declarative)
Implicit (Non-declarative)
Semantic (Facts)
Episodic (Events)
Priming
Procedural
Associative
Learning
Nonassociative
Medial temporal lobe
Skeletal
musculature
Emotional
responses
Reflex
pathways
Amygdala
Striatum
Neocortex
Cerebellum ?

4. Episodic Memory
Explicit memory for conscious recollection of events from past experience
Buckner and Koustaal, 1998

5. Perceptual Repetition Priming
Facilitation derived from repeated exposure to a stimulus
Buckner et al., 1998

6. Hypothesis
Priming for past experiences can hinder new episodic encoding.
Long Term Memory
Explicit (Declarative)
Implicit (Non-declarative)
Semantic (Facts)
Episodic (Events)
Priming
Procedural
Associative
Learning
Nonassociative
Medial temporal lobe
Skeletal
musculature
Emotional
responses
Reflex
pathways
Amygdala
Striatum
Neocortex
Cerebellum

7. 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).

8. Experimental Procedure
Varied temporal lag between initial and repeated encoding episodes with words.

9. Behavioral Priming
Mean median Reaction Times (RTs) for Abstract/Concrete decision (msec).
Once-presented: 777
Long-Lag: 763
Short-Lag: 720 * ** ** **
* p < ** p <

10. 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.

11. 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

12. 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 < ** p <

13. 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)

14. 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 ...

15. 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.