Skip to main content

Statistical traces of long-term memories stored in strengths and patterns of synaptic connections

Learning and long-term memory rely on plasticity of neural circuits. In adult cerebral cortex plasticity can result from potentiation and depression of synaptic strengths and structural reorganization of circuits through growth and retraction of dendritic spines. By analyzing 166 distributions of spine head volumes and spine lengths from mouse, rat, monkey, and human brains, we determine the “generalized cost” of dendritic spines. This cost universally depends on spine shape, i.e. the dependence is the same in all the analyzed systems. We show that in adult synaptic strength and structural synaptic plasticity mechanisms are in statistical equilibrium, the numbers of dendritic spines in different cortical areas are nearly optimally chosen for memory storage, and the distributions of spine lengths and head volumes are governed by a single parameter – the effective temperature. We suggest that the effective temperature may be viewed as a measure of circuit stability or longevity of stored memories.


This work was supported by the NIH grants NS047138 and NS542720.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Armen Stepanyants.

Rights and permissions

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and Permissions

About this article

Cite this article

Stepanyants, A., Escobar, G. Statistical traces of long-term memories stored in strengths and patterns of synaptic connections. BMC Neurosci 12 (Suppl 1), O2 (2011).

Download citation

  • Published:

  • DOI: