1. A computer-assisted method comprising: displaying volumetric imaging data on a display representing an anatomic volume of tissue of a patient; displaying an indication of a first electrode location of an electrode that has been guided into the anatomic volume; using a computer model in calculating a volume of influence; and displaying the calculated volume of influence; wherein: the volume of influence includes a predicted volume of tissue affected by an electrical stimulation delivered by the first electrode; and calculating the volume of influence includes calculating a second difference of a potential distribution to represent the volume of influence.