1. A computer-assisted method comprising: displaying volumetric imaging data representing an anatomic volume of a brain of a patient; guiding an electrode into the anatomic volume represented by the imaging data; displaying an actual first electrode location of the electrode in the anatomic volume; using a computer model in calculating at least one volume of influence, wherein the volume of influence comprises a predicted volume of tissue affected by an electrical stimulation delivered by the displayed first electrode, and wherein calculating the volume of influence comprises at least one of: i) calculating a second difference of a potential distribution to represent the volume of influence; or ii) calculating the volume of influence includes using an electric field model together with a multi-compartment neuron model oriented and positioned to represent at least one actual nerve pathway in the anatomic volume; and displaying the calculated volume of influence to a user.