Measurement and simulation of unmyelinated nerve electrostimulation:Lumbricus terrestrisexperiment and numerical model

Abstract

The electrostimulation excitation threshold of a nerve depends on temporal and frequency parameters of the stimulus. These dependences were investigated in terms of: (1) strength-duration (SD) curve for a single monophasic rectangular pulse, and (2) frequency dependence of the excitation threshold for a continuous sinusoidal current. Experiments were performed on the single-axon measurement setup based on Lumbricus terrestris having unmyelinated nerve fibers. The simulations were performed using the well-established SENN model for a myelinated nerve. Although the unmyelinated experimental model differs from the myelinated simulation model, both refer to a single axon. Thus we hypothesized that the dependence on temporal and frequency parameters should be very similar. The comparison was made possible by normalizing each set of results to the SD time constant and the rheobase current of each model, yielding the curves that show the temporal and frequency dependencies regardless of the model differences. The results reasonably agree, suggesting that this experimental setup and method of comparison with SENN model can be used for further studies of waveform effect on nerve excitability, including unmyelinated neurons.

Dependence of excitability indices on membrane channel dynamics, myelin impedance, electrode location and stimulus waveforms in myelinated and unmyelinated fibre models

“…Indeed, it is observed that the shape of the normalized strength-duration relation is altered, when stimulation at neuronal terminations becomes the dominant mode of excitation. This is an extension of a result obtained byŠarolić et al: it was determined byŠarolić et al that the normalized strength-duration curve does not depend on the electrode location and spatial waveform (wire electrode, bipolar electrode setup or homogeneous E-field) in the SENN-model [34]. However, the effect of neuronal terminations, waveform polarity, and membrane dynamics was not yet taken into account.…”

Benchmarking Electrical Stun Devices by Considering Electroporation

“…In that case, the variable conductivity may have resulted in the risk of these ESDs being overstated. The SENN was veri ed via an experiment with nervous tissue [39] but not in any in vivo experiments with cardiac tissue. Because of the great danger of an ESD exposure and the local restriction of animal experiments, the validation of the new benchmarking procedure is currently not possible.…”