1. Neuroscience

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
https://doi.org/10.7554/eLife.03896
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  1. Shanping Chen
  2. Diancai Cai
  3. Kaycey Pearce
  4. Philip Y W Sun
  5. Adam C Roberts
  6. David L Glanzman
(2014)
Reinstatement of long-term memory following erasure of its behavioral and synaptic expression in Aplysia
eLife 3:e03896.
https://doi.org/10.7554/eLife.03896
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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.

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Author details

  1. Shanping Chen

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

  2. Diancai Cai

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

  3. Kaycey Pearce

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

  4. Philip Y W Sun

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

  5. Adam C Roberts

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

  6. David L Glanzman

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

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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  1. Shanping Chen
  2. Diancai Cai
  3. Kaycey Pearce
  4. Philip Y W Sun
  5. Adam C Roberts
  6. David L Glanzman
(2014)
Reinstatement of long-term memory following erasure of its behavioral and synaptic expression in Aplysia
eLife 3:e03896.
https://doi.org/10.7554/eLife.03896

Share this article

https://doi.org/10.7554/eLife.03896

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Further reading

    1. Neuroscience

    Role of protein synthesis and DNA methylation in the consolidation and maintenance of long-term memory in Aplysia

    Kaycey Pearce, Diancai Cai ... David L Glanzman
    Research Article Updated

    Previously, we reported that long-term memory (LTM) in Aplysia can be reinstated by truncated (partial) training following its disruption by reconsolidation blockade and inhibition of PKM (Chen et al., 2014). Here, we report that LTM can be induced by partial training after disruption of original consolidation by protein synthesis inhibition (PSI) begun shortly after training. But when PSI occurs during training, partial training cannot subsequently establish LTM. Furthermore, we find that inhibition of DNA methyltransferase (DNMT), whether during training or shortly afterwards, blocks consolidation of LTM and prevents its subsequent induction by truncated training; moreover, later inhibition of DNMT eliminates consolidated LTM. Thus, the consolidation of LTM depends on two functionally distinct phases of protein synthesis: an early phase that appears to prime LTM; and a later phase whose successful completion is necessary for the normal expression of LTM. Both the consolidation and maintenance of LTM depend on DNA methylation.