Neuron matters: electric activation of neuronal tissue is dependent on the interaction between the neuron and the electric field

Abstract

In laboratory research and clinical practice, externally-applied electric fields have been widely used to control neuronal activity. It is generally accepted that neuronal excitability is controlled by electric current that depolarizes or hyperpolarizes the excitable cell membrane. What determines the amount of polarization? Research on the mechanisms of electric stimulation focus on the optimal control of the field properties (frequency, amplitude, and direction of the electric currents) to improve stimulation outcomes. Emerging evidence from modeling and experimental studies support the existence of interactions between the targeted neurons and the externally-applied electric fields. With cell-field interaction, we suggest a two-way process. When a neuron is positioned inside an electric field, the electric field will induce a change in the resting membrane potential by superimposing an electrically-induced transmembrane potential (ITP). At the same time, the electric field can be perturbed and re-distributed by the cell. This cell-field interaction may play a significant role in the overall effects of stimulation. The redistributed field can cause secondary effects to neighboring cells by altering their geometrical pattern and amount of membrane polarization. Neurons excited by the externally-applied electric field can also affect neighboring cells by ephaptic interaction. Both aspects of the cell-field interaction depend on the biophysical properties of the neuronal tissue, including geometric (i.e., size, shape, orientation to the field) and electric (i.e., conductivity and dielectricity) attributes of the cells. The biophysical basis of the cell-field interaction can be explained by the electromagnetism theory. Further experimental and simulation studies on electric stimulation of neuronal tissue should consider the prospect of a cell-field interaction, and a better understanding of tissue inhomogeneity and anisotropy is needed to fully appreciate the neural basis of cell-field interaction as well as the biological effects of electric stimulation.

Alternating chimeras in networks of ephaptically coupled bursting neurons

“…Moreover, recent researches 46,50,52,55,57 suggest that the modeling of neuronal networks as mere an ensemble of physical connections (biochemical or electrical) among neurons is incomplete unless it also includes effusive extra-neuronal phenomena such as electric and magnetic fields. Indeed, the dynamics of the neuronal activity may get affected because of the fluctuation in the inter-and extra-cellular ion concentrations.…”

Deformation but not migration and rotation – a model study on vesicle biomechanics in a uniform DC electric field

“…This work supports our hypothesis that biological effects of electric stimulation is a function of both the field parameters and the cellular properties. [39] 4.1 Induced charges and vesicle deformation Our model predicts that the direction of vesicle deformation depends on the dielectric properties of the vesicle (see Figure 2). Prolate deformation will occur along the symmetry axis that aligns parallel to the field if the cytoplasm is more conductive than the medium (see Figure 2A), and an oblate deformation will occur if the medium is more conductive than the cytoplasm (see Figure 2B).…”

“…A detailed review on this topic could be found elsewhere. [39] 4.4 Future directions Several assumptions have to be made in the model to simplify the calculation. It did not include other mechanical considerations such as shear elasticity of the membrane [3] and ion movement through field-induced pores, which will affect electric fields [51] and vesicle shapes.…”

Technobiology’s Enabler: The Magnetoelectric Nanoparticle

“…Using a back-of-the-envelope-type estimation, assuming an applied magnetic field of 1000 Oe, an MENP with an α of 100 mV cm −1 Oe −1 would generate an electric field of 100 V/cm (10 4 V/m). Generating such a field across the membrane would be sufficient to trigger firing of an action potential by a single nanoparticle (Ye and Steiger 2015). Furthermore, when acted collectively and under application of periodic signals corresponding to periodic rhythms of brain waves, MENPs could easily provide highefficacy stimulation.…”