REMERGE: A new approach to the neural basis of generalization and memory-based inference Dharshan...
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Transcript of REMERGE: A new approach to the neural basis of generalization and memory-based inference Dharshan...
REMERGE: A new approach to the neural basis of generalization and
memory-based inference
Dharshan Kumaran, UCLJay McClelland, Stanford University
Proposed Architecture for the Organization of Semantic Memory
McClelland, McNaughton & O’Reilly, 1995
colorform
motion
action
valance
Temporal pole
name
Medial Temporal Lobe
Two Questions
• If extraction of generalizations depends on gradual learning, how do we form generalizations and inferences shortly after initial learning?
• Why do some studies find evidence consistent with the view that an intact MTL facilitates certain types of generalization in memory?
Relational Theory of Memory (Eichenbaum & Cohen)
• Proposes that elements of related memories become linked within the same memory trace, and that the formation of such linkages is a critical function of the MTL.
REMERGE: Recurrence and Episodic Memory Results in Generalization
• Holds that several MTL based item representations may work together through recurrent activation
• Draws on classic exemplar models (Medin & Shaffer, 1978; Nosofsky, 1984)
• Extends these models by allowing similarity between stored items to influence performance, independent of direct activation by the probe (McClelland, 1981)
• Demonstrates the strong dependence of some forms of generalization and inference on the strength of learning for trained items
Phenomena Considered
• Benchmark Simulations– Categorization– Recognition memory
• Acquired Equivalence• Associative Chaining– In paired associate learning– In hippocampal reactivation during sleep
• Transitive Inference– Effects of increasing study– Effects of sleep
Acquired Equivalence(Shohamy & Wagner, 2008)
• Study:– F1-S1; – F3-S3;– F2-S1; – F2-S2;– F4-S3; – F4-S4
• Test:– Premise: F1: S1 or S3?– Inference: F1: S2 or S4?
F1 S1 F2 S2 F3 S3 F4 S4
Acquired Equivalence(Shohamy & Wagner, 2008)
• Study:– F1-S1; – F3-S3;– F2-S1; – F2-S2;– F4-S3; – F4-S4
• Test:– Premise: F1: S1 or S3?– Inference: F1: S2 or S4?
F1 S1 F2 S2 F3 S3 F4 S4
Acquired Equivalence(Shohamy & Wagner, 2008) S1 S2 S3 S4
• Study:– F1-S1; – F3-S3;– F2-S1; – F2-S2;– F4-S3; – F4-S4
• Test:– Premise: F1: S1 or S3?– Inference: F1: S2 or S4?
F1 S1 F2 S2 F3 S3 F4 S4
Acquired Equivalence(Shohamy & Wagner, 2008) S1 S2 S3 S4
• Study:– F1-S1; – F3-S3;– F2-S1; – F2-S2;– F4-S3; – F4-S4
• Test:– Premise: F1: S1 or S3?– Inference: F1: S2 or S4?
Acquired Equivalence(Shohamy & Wagner, 2008)
• Study:– F1-S1; – F3-S3;– F2-S1; – F2-S2;– F4-S3; – F4-S4
• Test:– Premise: F1: S1 or S3?– Inference: F1: S2 or S4?
Associative Chaining• Study:
– AB, XY– BC, YZ
• Test:– A: B or Y– A: C or Z
A B C X Y Z
Hippocampal Reactivation After Maze Exploration
Replays in Remerge:
Forward: 51%Backward: 31%Crossed: 18%Disjoint: <1%
Growth in Generalization with Increasing Premise Strength
Discussion• As we’ve known for quite some time
– Generalization and Inference can be supported by exemplar models• Should we, then, simply abandon the complementary learning
theory, and just make it exemplars all the way down?• I think not –
– Cortical learning supports changes in the ‘features’ that serve as the basis for exemplar learning
– And clearly, retrograde amnesia studies support = an MTL basis for recent memory= a neocortical basis for remote memory
• A future challenge is to develop an fully integrated neuro-computational theory of memory integrating MTL and neocortical influences