The impact of channel and external synaptic noises on spatial and temporal coherence in neuronal networks

This paper investigates influences of internal ion channel fluctuations and external synaptic noise on the spatiotemporal dynamics of an excitatory Erdös–Rényi neuronal network. The impact of stochastic coupling between pre- and post-synaptic neurons in the network is also studied. First, we show that channel noise induces a spatiotemporal coherence resonance for a moderate-sized membrane, which is further enhanced with the increase of the strength and probability of the connections. Second, in networks with low connectivity probabilities, the presence of an external synaptic noise to each neuron, in addition to internal channel noise, further increases the channel noise-induced spatiotemporal coherence (CNI-STC). However, in networks with high probability of connections, the CNI-STC characterized by the coherence measure of firing spikes, the variability of interspike interval, as well as the mean power, remains almost unchanged to the external noise perturbation. Finally, comparing the effects of channel fluctuations with external synaptic noise has revealed several key features: in a dense network, population dynamics described by the population firing rate, the coherence measure, and the mean power, is highly susceptible to channel fluctuations, while it is relatively robust to external noise. Furthermore, in a sparse network, the external synaptic noise alone is sufficient to induce a stronger spatiotemporal coherence resonance but a lower population firing rate, in comparison to the phenomena in the presence of both intrinsic and extrinsic noises. The mechanisms of the above phenomena are explained from the interaction of intrinsic dynamics which is controlled by channel fluctuations and network topology with external synaptic noise.