1. A computer-implemented method for determining anatomical tissue regions that are relevant to stimulation, comprising: receiving a selection of a stimulation effect, wherein the selected stimulation effect is either a therapeutic effect or a side effect; obtaining, by a computer processor, a first collection of a first plurality of anatomical tissue volumes for which previous stimulation of each of the first plurality of anatomical tissue volumes for a plurality of patients produced the selected stimulation effect; obtaining, by the computer processor, a second collection of a second plurality of anatomical tissue volumes for which previous stimulation of each of the second plurality of anatomical tissue volumes for a plurality of patients did not produce the selected stimulation effect, the first and second plurality of anatomical tissue volumes being registered to a common reference space; comparing, by the processor, the first plurality of anatomical tissue volumes to the second plurality of anatomical tissue volumes; based on the comparing, finding, by the processor, a target volume for the selected stimulation effect, wherein the target volume comprises a plurality of volume elements that each meet two criteria: (a) the volume element is included in either a threshold number or a threshold percentage of the first plurality of anatomical tissue volumes and (b) the volume element is not included in either a threshold number or a threshold percentage of the second plurality of anatomical tissue volumes; subsequent to the comparing, outputting, by the processor, a representation of the target volume found in the finding step, wherein the representation represents the target volume as an anatomical region and indicates, when the selected stimulation effect is the therapeutic effect, that the target volume is to be stimulated or, when the selected stimulation effect is the side effect, that stimulation is to be avoided in the target volume; comparing the target volume with a plurality of volumes of activation (VOAs), wherein each the VOAs corresponds to an estimate of a volume of tissue stimulated using a corresponding set of stimulation parameters: selecting one of the volumes of activation based on the comparison with the target volume where the selected VOA either (a) overlaps with the target volume by a threshold amount when the target volume is to be stimulated because the selected stimulation effect is the therapeutic effect or (b) does not overlap with the target volume by a threshold amount when stimulation is to be avoided in the target volume because the selected stimulation effect is the side effect; and stimulating a patient using the corresponding set of stimulation parameters for the selected VOA.