Optimal plasticity for memory maintenance during ongoing synaptic change

  1. Dhruva Raman  Is a corresponding author
  2. Timothy O'Leary  Is a corresponding author
  1. University of Cambridge, United Kingdom


Synaptic connections in many brain circuits fluctuate, exhibiting substantial turnover and remodelling over hours to days. Surprisingly, experiments show that most of this flux in connectivity persists in the absence of learning or known plasticity signals. How can neural circuits retain learned information despite a large proportion of ongoing and potentially disruptive synaptic changes? We address this question from first principles by analysing how much compensatory plasticity would be required to optimally counteract ongoing fluctuations, regardless of whether fluctuations are random or systematic. Remarkably, we find that the answer is largely independent of plasticity mechanisms and circuit architectures: compensatory plasticity should be at most equal in magnitude to fluctuations, and often less, in direct agreement with previously unexplained experimental observations. Moreover, our analysis shows that a high proportion of learning-independent synaptic change is consistent with plasticity mechanisms that accurately compute error gradients.

Data availability

All code is publicly available on github at this URL:https://github.com/Dhruva2/OptimalPlasticityRatios

Article and author information

Author details

  1. Dhruva Raman

    University of Cambridge, Cambridge, United Kingdom
    For correspondence
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8992-1353
  2. Timothy O'Leary

    University of Cambridge, Cambridge, United Kingdom
    For correspondence
    Competing interests
    Timothy O'Leary, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1029-0158


European Commission (StG 2016 716643 FLEXNEURO)

  • Dhruva Raman
  • Timothy O'Leary

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Srdjan Ostojic, Ecole Normale Superieure Paris, France

Version history

  1. Preprint posted: August 19, 2020 (view preprint)
  2. Received: September 8, 2020
  3. Accepted: September 13, 2021
  4. Accepted Manuscript published: September 14, 2021 (version 1)
  5. Version of Record published: October 11, 2021 (version 2)


© 2021, Raman & O'Leary

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. Dhruva Raman
  2. Timothy O'Leary
Optimal plasticity for memory maintenance during ongoing synaptic change
eLife 10:e62912.

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