Electric fields have been widely used for the treatment of neurological diseases, using techniques such as non-invasive brain stimulation. An electric current controls cell excitability by imposing voltage changes across the cell membrane. At the same time, the presence of the cell itself causes a re-distribution of the local electric field. Computation of the electric field distribution at a single cell microscopic level is essential in understanding the mechanism of electric stimulation. In addition, the impact of the cellular biophysical properties on the field distribution in the vicinity of the cell should also be addressed. In this paper, we have begun by first computing the field distribution around and within a spherical model cell. The electric fields in the three regions differed by several orders of magnitude. The field intensity in the extracellular space was of the same order as that of the externally applied field, while in the membrane, it was calculated to be several thousand times greater than the applied field. In contrast, the field intensity inside the cell was greatly attenuated to approximately 1/133th of the applied field. We then performed a detailed analysis on the dependency of the local field distribution on both the electrical properties (i.e., conductivity, dielectricity), and the geometrical properties (i.e., size, membrane thickness) of the target cell. Variations of these parameters caused significant changes to the amplitude and direction of the electric field around a single cell. The biophysical mechanisms of such observations and their experimental implications are discussed. These results highlight the significance of considering cellular properties during the electric stimulation of neuronal tissues.
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