This title appears in the Scientific Report : 2014 

Dynamics of self-sustained asynchronous-irregular activity in random networks of spiking neurons with strong synapses
Kriener, Birgit (Corresponding Author)
Enger, Håkon / Tetzlaff, Tom / Plesser, Hans Ekkehard / Gewaltig, Marc-Oliver / Einevoll, Gaute T.
Theoretical Neuroscience; IAS-6
Computational and Systems Neuroscience; INM-6
Frontiers in computational neuroscience, 8 (2014) S. 136
Lausanne Frontiers Research Foundation 2014
Journal Article
The Human Brain Project
Supercomputing and Modelling for the Human Brain
Helmholtz Alliance on Systems Biology
Brain-inspired multiscale computation in neuromorphic hybrid systems
Signalling Pathways and Mechanisms in the Nervous System
Theory, modelling and simulation
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Random networks of integrate-and-fire neurons with strong current-based synapses can, unlike previously believed, assume stable states of sustained asynchronous and irregular firing, even without external random background or pacemaker neurons. We analyze the mechanisms underlying the emergence, lifetime and irregularity of such self-sustained activity states. We first demonstrate how the competition between the mean and the variance of the synaptic input leads to a non-monotonic firing-rate transfer in the network. Thus, by increasing the synaptic coupling strength, the system can become bistable: In addition to the quiescent state, a second stable fixed-point at moderate firing rates can emerge by a saddle-node bifurcation. Inherently generated fluctuations of the population firing rate around this non-trivial fixed-point can trigger transitions into the quiescent state. Hence, the trade-off between the magnitude of the population-rate fluctuations and the size of the basin of attraction of the non-trivial rate fixed-point determines the onset and the lifetime of self-sustained activity states. During self-sustained activity, individual neuronal activity is moreover highly irregular, switching between long periods of low firing rate to short burst-like states. We show that this is an effect of the strong synaptic weights and the finite time constant of synaptic and neuronal integration, and can actually serve to stabilize the self-sustained state.