Comparison study of different head model structures with homogeneous/inhomogeneous conductivity

Most of the human head models used in dipole localisation research, which have been reported in the literature to date, assume a simplified cranial structure wherein the head is modelled as a set of distinct homogenous tissue compartments. The inherent inhomogeneity of the tissues has so far been ignored in these models due to the difficulties involved in obtaining the conductivity characteristics with sufficiently high enough spatial resolution throughout the head. A technique for developing an inhomogeneous head model based on the generation of pseudo-conductivity values from the existing but sparse conductivity values is proposed in this paper. Comparative studies are conducted on different model structures and different mechanisms for generating the pseudo conductivities. An evaluation of the results of these studies as reported in this paper, shows that contrary to current simplifying assumptions, tissue inhomogeneity has a major influence on the computation of electrical potential distributions in the head