A Model for Neural Activity in the Absence of External Stimuli

A. Duarte, G. Ost

2016, v.22, №1, 37-52

ABSTRACT

We study a stochastic process describing the continuous time evolution of the membrane potentials of finite system of neurons in the absence of external stimuli. The values of the membrane potentials
evolve under the effect of {\it chemical synapses}, {\it electrical synapses} and \textit{leak currents}. The evolution of the process can be informally described as follows. Each neuron spikes randomly following a point process with rate depending on its membrane potential. When a neuron spikes, its membrane potential is immediately reset to a resting value. Simultaneously, the membrane potential of the neurons which are influenced by the spiking neuron receive an additional positive value. Furthermore, between consecutive spikes, the system follows a deterministic motion due both to electrical synapses and leak currents. Electrical synapses push the system towards its average potential, while leak currents attract the membrane potential of each neuron to the resting value.

We show that in the absence of leakage the process converges to an unique invariant measure, whenever the initial configuration is non null. More interesting, when leakage is present,
we prove the system stops spiking after a finite amount of time almost surely. This implies that the unique invariant measure is supported only by the null configuration.

Keywords: piecewise deterministic Markov process, limiting distribution, neural systems, chemical synapses, electrical synapses, leak currents

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