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Memory Consolidation. PSY 506A 11.4.11 Molly Bisbee. A Summary. Overview. Definition Standard model MTT Differences Evidence. General Definition. A process after initial encoding that is critical to stable long-term memory Stabilizes memories Incorporates new information with old.

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memory consolidation

Memory Consolidation

PSY 506A

11.4.11

Molly Bisbee

A Summary

overview
Overview
  • Definition
  • Standard model
  • MTT
  • Differences
  • Evidence
general definition
General Definition
  • A process after initial encoding that is critical to stable long-term memory
    • Stabilizes memories
    • Incorporates new information with old
temporal characteristics
Temporal Characteristics
  • Cellular or synaptic consolidation
    • Brief process lasting seconds or minutes
      • Initial emphasis
  • Systems consolidation
    • Lasts weeks, months, or years
      • Recent emphasis
the standard model stm
The Standard Model (STM)
  • dispersed neocortical sites linked together by hippocampal complex, where ensemble trace is rapidly created (via LTP or the like)
    • H-trace, or “index”, “binds” the dispersed C-traces, allowing dispersed cortical sites to be reactivated together
      • over time, C-traces link directly; intervention of H-trace no longer needed, it fades away
        • information content is the same whether or not H-trace is involved in retrieval
        • Hippocampus plays same role in episodic and semantic memory
stm problems
STM Problems
  • Length of consolidation period
  • Dissociations among episodic and semantic memory
  • Reconsolidation
multiple trace theory
Multiple Trace Theory
  • H always involved in storage and retrieval of episodic memory
  • The H-C combination is the episode memory trace
  • H represents contextual component of episode
  • each re-activation/retrieval of a memory occurs in different context and results in altered trace; expanded or strengthened H trace and H-C links
  • episodic and semantic memory must be considered separately
slide10
MTT
  • Different from Standard Theory
  • the H-C complex is the episode memory trace; H serves not only to bind elements in C, but also as the repository of critical episodic components
  • each re-activation of a memory occurs in a different context and results in a new sparse, distributed trace in H
  • each such trace shares some of the C representations

Similar to Standard Theory

  • hippocampus automatically encodes all attended information
  • H- traces are sparsely encoded in distributed representations
  • these ensembles act as pointers to the cortical ensembles storing attended information

MTT asserts that H and C are both always involved in the storage and retrieval of episodic memory, and that episodic and semantic memory must be considered separately.

mtt implications
MTT Implications
  • Aging episodic memories either forgotten or benefit from formation of stronger, expanded, memory traces
  • HC active during retrieval of episode memories of any age
  • HC preferentially active in processing spatial/contextual material
  • H plays different role in episodic and semantic memory
  • Partial HC damage affects memories proportional to age/strength; complete HC lesions will yield flat gradient of RA for episodic, but not semantic memories
  • Remote memories in amnesics should be generic in nature
  • Older memories will have stronger, more distributed, traces in H
  • Reactivating a memory should lead to updating and reconsolidation
older memories will have stronger more distributed traces in h

Remote events

Foci of left hippocampal activations across subjects

Recentevents

Older memories will have weaker, less distributed, (or nonexistent) traces in H

Older memories will have stronger, more distributed, traces in H

vs.

The evidence?

Older memories are represented more diffusely within hippocampus

reactivating a memory should lead to updating and reconsolidation
Reactivating a memory should lead to updating and reconsolidation

Reactivating a memory should not affect it

vs.

The evidence?

reactivating a memory should increase h involvement
Reactivating a memory should increase H involvement

Recent 2 > Recent 1, p < 0.05

Remote 2 > Remote 1, p < 0.05

Repeated retrievals increase activation in hippocampus – equivalently for recent and remote memories

L post HC

L post HC

R phg

R phg

Reactivating a memory should reduce H involvement

vs.

The evidence?

reactivation
Reactivation

Memories can be reactivated either online (during wake) or offline (during sleep)

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