On the physical nature of biopotentials, their propagation and measurement

This paper discusses various consequences of the fact that the physical nature of process of generation, propagation and measurement of biopotentials is inherently ionic. Source of macroscopic biopotential is the temporary deficit of charge captured by ionic channels, which polarizes the organ border. Electric properties of the living tissue seem to be dominated by the electrolyte which polarizes easily and fast. Current theory of biopotential which treats the body as a volume conductor of certain conductivity is an idealization, which does not consider polarization of tissue. Polarization in quasistatic approximation may be reliably described using the well-known Debye–Hückel theory for electrolytes, derived directly from Boltzmann equation and Poisson equation. The polarization theory for biopotential generation, propagation and measurement is conceptually simple and enables to model wider range of experimental conditions, such as dependence of the potential on ionic strength. Modification of the basic numerical assumption for biopotential modeling: the electroneutrality condition is proposed. The accuracy of the theory is verified by comparison with existing experimental results, which shows very good accuracy. This paper shows the importance of a proper physical description to interpretation of biopotentials. The topic is of special importance to electrophysiology and neuroscience, but affects all biopotential measurements, theories and numerical studies.