Analysis of ion current fluctuations in multi-compartment models of electrically stimulated neurons

Abstract

In many human cases neurons are experimentally poorly accessible, introducing the need for computer simulations to study their behavior. In order to model nerve impulses, the electrical activity of neurons is described by systems of differential equations, which in the case of this work are based on the principle of the Hodgkin and Huxley equations. These were used to create models that describe the individual parts of a neuron and, subsequently, the representation of an entire neuron. In addition to straight nerve fibers, a 2D pathway in the basal turn of the human cochlear was simulated to account for real anatomical conditions. This allowed us to study the effects of displacements of the externally stimulating electrode for real cochlear implant situations. The relative spread (RS), introduced by Verveen and representing the coefficient of variation of the cumulative Gaussian distribution, served as the central metric for stochasticity.We showed (i) that the placement of the electrode over dendritic regions leads to significantly larger RS than stimulation over soma, indicating that the site of origin of the AP is important for the RS. (ii) the inverse relationship of RS to diameter, (iii) long internodes lead to a reduction in spontaneous firing behavior, (iv) there is an inverse linear relationship between RS and myelin conductivity and (v) that if the noise transmission time (Dt) is changed, the default value to 0.0025ms of knoise has to be multiplied by the factor (0.0025/Dt)^(1/2)*knoise(0.0025).