1. A computer-assisted method comprising: obtaining imaging data of an anatomic volume of a brain of a patient; obtaining nonuniform tissue conductivity data of the anatomic volume to represent inhomogeneous and anisotropic tissue properties; creating a finite element model (FEM) of a tissue volume near a possible electrode location, in which the FEM is tailored to a particular electrode morphology, and in which the FEM incorporates the nonuniform tissue conductivity data; solving the FEM, by a computer processor, to obtain a second difference in an electric potential distribution in the tissue volume; defining at least one threshold requirement on the second difference in the electric potential distribution, including using at least one neuron or axon model to define the at least one threshold requirement; and computing, by the computer processor, a volume of influence defined by a surface about the possible electrode location at which the second difference in the electric potential distribution meets the threshold requirement.