Energy efficient sparse connectivity from imbalanced synaptic plasticity rules

Sacramento, João and Wichert, Andreas and van Rossum, Mark C.W. (2015) Energy efficient sparse connectivity from imbalanced synaptic plasticity rules. PLoS Computational Biology, 11 (6). e1004265. ISSN 1553-7358

[img]
Preview
PDF - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Available under Licence Creative Commons Attribution.
Download (2MB) | Preview

Abstract

It is believed that energy efficiency is an important constraint in brain evolution. As synaptic transmission dominates energy consumption, energy can be saved by ensuring that only a few synapses are active. It is therefore likely that the formation of sparse codes and sparse connectivity are fundamental objectives of synaptic plasticity. In this work we study how sparse connectivity can result from a synaptic learning rule of excitatory synapses. Information is maximised when potentiation and depression are balanced according to the mean presynaptic activity level and the resulting fraction of zero-weight synapses is around 50%. However, an imbalance towards depression increases the fraction of zero-weight synapses without significantly affecting performance. We show that imbalanced plasticity corresponds to imposing a regularising constraint on the L1-norm of the synaptic weight vector, a procedure that is well-known to induce sparseness. Imbalanced plasticity is biophysically plausible and leads to more efficient synaptic configurations than a previously suggested approach that prunes synapses after learning. Our framework gives a novel interpretation to the high fraction of silent synapses found in brain regions like the cerebellum.

Item Type: Article
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Mathematical Sciences
University of Nottingham, UK > Faculty of Science > School of Psychology
Identification Number: https://doi.org/10.1371/journal.pcbi.1004265
Depositing User: Van Rossum, Mark
Date Deposited: 08 Feb 2018 13:28
Last Modified: 08 Feb 2018 13:35
URI: http://eprints.nottingham.ac.uk/id/eprint/49632

Actions (Archive Staff Only)

Edit View Edit View