Experimental models for current conduction in an anisotropic medium

Many biological tissues have some degree of directional organization and would therefore be expected to behave anisotropically to electrical current conduction. An analysis of curren t and poten tial distribu tions throughout the bulk of such a tissue may be required, for exa nrple, in electrical stimulation and recording with macroelectrodes, impedance measurements, and field effects in cerebral cortex. In all these cases the sources and sinks of current will usually have complex distributions which render a cornputa tional solution difficult and inaccessible to experirnental workers, In addition it is normally impossible to construct a model and measure the required quantities since the model would require an anisotropically conducting medium which could not be easily realized in practice. The method described, subsequently, shows it is possible to use a model with an isotropic medium provided the shape of the model is suitably distorted. The method will be outlined for the case of finding the current and potential distributions when a current I is passed between two arbitrarily shaped electrodes in an anisotropic medium having principal conductivities.