Development of a model for point source electrical fibre bundle stimulation

A model is presented for determining the excitation (transmembrane) potentials on nerve and muscle fibres in a cylindrical bundle from an external point source electrode at the surface and within the preparation. The fibre bundle is considered to be immersed in an infinite isotropic conductive medium and is idealised as an infinitely extending cylinder. This cylinder is initially represented as an isotropic monodomain. A subsequent degree of complexity introduces anisotropy in the monodomain, and finally the bundle is represented as an anisotropic bidomain comprised of the interstitial radial and longitudinal conductivities, the intracellular longitudinal conductivity and the fibre membrane between the two domains. In this latter model, electrical coupling from extracellular to intracellular space is included by means of the bidomain formulation. Computational aspects are discussed, and preliminary results for prescribed conditions are presented.