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Reinstatement of long-term memory following erasure of its behavioral and synaptic expression in Aplysia

  1. Shanping Chen
  2. Diancai Cai
  3. Kaycey Pearce
  4. Philip Y W Sun
  5. Adam C Roberts
  6. David L Glanzman Is a corresponding author
  1. Univeristy of California, Los Angeles, United States
Research Article
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Cite as: eLife 2014;3:e03896 doi: 10.7554/eLife.03896

Abstract

Long-term memory (LTM) is believed to be stored in the brain as changes in synaptic connections. Here, we show that LTM storage and synaptic change can be dissociated. Cocultures of Aplysia sensory and motor neurons were trained with spaced pulses of serotonin, which induces long-term facilitation. Serotonin (5HT) triggered growth of new presynaptic varicosities, a synaptic mechanism of long-term sensitization. Following 5HT training, two antimnemonic treatments-reconsolidation blockade and inhibition of PKM-caused the number of presynaptic varicosities to revert to the original, pretraining value. Surprisingly, the final synaptic structure was not achieved by targeted retraction of the 5HT-induced varicosities but, rather, by an apparently arbitrary retraction of both 5HT-induced and original synapses. In addition, we find evidence that the LTM for sensitization persists covertly after its apparent elimination by the same antimnemonic treatments that erase learning-related synaptic growth. These results challenge the idea that stable synapses store long-term memories.

Article and author information

Author details

  1. Shanping Chen

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Diancai Cai

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Kaycey Pearce

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Philip Y W Sun

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Adam C Roberts

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. David L Glanzman

    1. Univeristy of California, Los Angeles, Los Angeles, United States
    For correspondence
    1. dglanzman@physci.ucla.edu
    Competing interests
    The authors declare that no competing interests exist.

Reviewing Editor

  1. Mani Ramaswami, Reviewing Editor, Trinity College Dublin, Ireland

Publication history

  1. Received: July 4, 2014
  2. Accepted: November 13, 2014
  3. Accepted Manuscript published: November 17, 2014 (version 1)
  4. Version of Record published: December 12, 2014 (version 2)

Copyright

© 2014, Chen et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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