Abstract
Despite intensive research, the mechanisms underlying the neural code remain poorly understood. Recent work has focused on the response of a single neuron to a weak, sub-threshold periodic signal. By simulating the stochastic FitzHugh-Nagumo (FHN) model and then using a symbolic method to analyze the firing activity, preferred and infrequent spike patterns (defined by the relative timing of the spikes) were detected, whose probabilities encode information about the signal. As not individual neurons but neuronal populations are responsible for sensory coding and information transfer, a relevant question is how a second neuron, which does not perceive the signal, affects the detection and the encoding of the signal, done by the first neuron. Through simulations of two stochastic FHN neurons we show that the encoding of a sub-threshold signal in symbolic spike patterns is a plausible mechanism. The neuron that perceives the signal fires a spike train that, despite having an almost random temporal structure, has preferred and infrequent patterns which carry information about the signal. Our findings could be relevant for sensory systems composed by two noisy neurons, when only one detects a weak external input.
Highlights
In spite of having been the object of intensive research for decades, the mechanisms used by neuronal populations to efficiently encode and transmit information, in noisy environments, remain poorly understood
By analyzing the ISI sequence using a nonlinear symbolic method known as ordinal analysis[25,26,27,28], it was shown that the weak periodic signal induces the emergence of temporal ordering in the timing of the spikes, which is absent if the neuron’s firing activity is only due to uncorrelated noise[22,29]
We have shown that when the neuron that perceives the signal is coupled to the second neuron, the spike rate increases and the noise level needed for firing spikes decreases, with respect to the uncoupled neuron
Summary
In spite of having been the object of intensive research for decades, the mechanisms used by neuronal populations to efficiently encode and transmit information, in noisy environments, remain poorly understood. By analyzing the ISI sequence using a nonlinear symbolic method known as ordinal analysis[25,26,27,28], it was shown that the weak periodic signal induces the emergence of temporal ordering in the timing of the spikes, which is absent if the neuron’s firing activity is only due to uncorrelated noise[22,29].
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