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. 2007 Jul 14;1(3):225–235. doi: 10.1007/s11571-007-9017-x

Modulation of synchrony without changes in firing rates

Jakob Heinzle 1, Peter König 2, Rodrigo F Salazar 3,✉
PMCID: PMC2267678  PMID: 19003515

Abstract

It was often reported and suggested that the synchronization of spikes can occur without changes in the firing rate. However, few theoretical studies have tested its mechanistic validity. In the present study, we investigate whether changes in synaptic weights can induce an independent modulation of synchrony while the firing rate remains constant. We study this question at the level of both single neurons and neuronal populations using network simulations of conductance based integrate-and-fire neurons. The network consists of a single layer that includes local excitatory and inhibitory recurrent connections, as well as long-range excitatory projections targeting both classes of neurons. Each neuron in the network receives external input consisting of uncorrelated Poisson spike trains. We find that increasing this external input leads to a linear increase of activity in the network, as well as an increase in the peak frequency of oscillation. In contrast, balanced changes of the synaptic weight of excitatory long-range projections for both classes of postsynaptic neurons modulate the degree of synchronization without altering the firing rate. These results demonstrate that, in a simple network, synchronization and firing rate can be modulated independently, and thus, may be used as independent coding dimensions.

Electronic supplementary material

The online version of this article (doi: 10.1007/s11571-007-9017-x) contains supplementary material, which is available to authorized users.

Keywords: Cortical columns, Integrate-and-fire neurons, Temporal code, Gamma oscillations

Acknowledgements

This work was funded by the Swiss National Science Foundation (Grant Nr: 31-65415.01). We thank Kevan AC Martin, Charles M Gray, Stefano Fusi and Shih-Cheng Yen for their careful reading and critical comments on previous versions of the manuscript.

Footnotes

Electronic supplementary material

The online version of this article (doi: 10.1007/s11571-007-9017-x) contains supplementary material, which is available to authorized users.

Contributor Information

Jakob Heinzle, Email: jakob@ini.phys.ethz.ch.

Peter König, Email: pkoenig@uos.de.

Rodrigo F. Salazar, Phone: +1-406-9947190, FAX: +1-406-9947438, Email: rsalazar@nervana.montana.edu

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