Remerge a new approach to the neural basis of generalization and memory based inference
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REMERGE: A new approach to the neural basis of generalization and memory-based inference. Dharshan Kumaran , UCL Jay McClelland, Stanford University. Medial Temporal Lobe. Proposed Architecture for the Organization of Semantic Memory McClelland, McNaughton & O’Reilly, 1995. name. action.

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REMERGE: A new approach to the neural basis of generalization and memory-based inference

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REMERGE: A new approach to the neural basis of generalization andmemory-based inference

DharshanKumaran, UCL

Jay McClelland, Stanford University


Medial Temporal Lobe

Proposed Architecture for the Organization of Semantic MemoryMcClelland, McNaughton & O’Reilly, 1995

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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?


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?

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?


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


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