Self-organization of a doubly asynchronous irregular network state for spikes and bursts.

Filip Vercruysse,Henning Sprekeler,Richard Naud

doi:10.1371/journal.pcbi.1009478

Abstract

Cortical pyramidal cells (PCs) have a specialized dendritic mechanism for the generation of bursts, suggesting that these events play a special role in cortical information processing. In vivo, bursts occur at a low, but consistent rate. Theory suggests that this network state increases the amount of information they convey. However, because burst activity relies on a threshold mechanism, it is rather sensitive to dendritic input levels. In spiking network models, network states in which bursts occur rarely are therefore typically not robust, but require fine-tuning. Here, we show that this issue can be solved by a homeostatic inhibitory plasticity rule in dendrite-targeting interneurons that is consistent with experimental data. The suggested learning rule can be combined with other forms of inhibitory plasticity to self-organize a network state in which both spikes and bursts occur asynchronously and irregularly at low rate. Finally, we show that this network state creates the network conditions for a recently suggested multiplexed code and thereby indeed increases the amount of information encoded in bursts.

Highlights

Cortical activity consists of irregular sequences of spikes [1], interspersed with bursts of several action potentials in quick succession [2, 3]
The language of the brain consists of sequences of action potentials
Bursts appear to play a special role in the brain

Summary

Introduction

Cortical activity consists of irregular sequences of spikes [1], interspersed with bursts of several action potentials in quick succession [2, 3]. Bursts can be generated by a coincidence of back-propagating actions potentials and synaptic input to the apical dendrite [4] This associative mechanism could underlie the integration of external sensory signals—reaching the peri-somatic domain—and internally generated signals [10] such as predictions [11, 12] or errors [13,14,15,16], which reach the apical dendrite in superficial cortical layers. Based on the observation that different information streams target different compartments that in turn generate distinct spike patterns, it was recently suggested that both information streams could be conveyed simultaneously by means of a multiplexed neural code [17] Such a multiplexing could be exploited, e.g., to route feedforward and feedback information in hierarchical networks [13, 17, 18]

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Discussion

Conclusion