The Effect of Media Inhomogeneities Upon Intracranial Electrical Fields

A three-dimensional finite difference computer simulation has been used to model entire intracranial fields from a known dipole generator in both a cat brain and an insulated cube. The model permits pointwise variation of conductivity coincident with intracranial inhomogeneities due to gray and white matter, cerebrospinal fluid, and bone. Adequacy of the model was verified by agreement between the computed results and those obtained in the cube with both homogeneous and inhomogeneous media and in the cat brain along the dipole axis. Variation of brain model parameters showed that neither increasing nor abolishing intracranial inhomogeneities would give differences great enough to be detected experimentally. On the other hand, the position of the boundary could have significant effects on the fields. The model is general enough to be applicable to a variety of multipole generators and generator locations, as well as permitting consideration of the influence of localized inhomogeneities.