However, VC/VS DBS' efficacy is limited by two major factors: imperfect targeting and a lack of decision rules for stimulation adjustment. The VC/VS target is not a single identifiable structure, but encompasses white matter of the internal capsule and gray matter of the nucleus accumbens (NAc). In current practice for DBS in OCD, all patients are implanted at standard x,y,z coordinates in the VC/VS region. Due to this inter-subject anatomical variability, different fiber tracts are stimulated by ostensibly the "same" parameters in each subject, leading to variable outcomes. This investigation will identify aspects of VC/VS circuitry that may determine clinical response. The hypothesis is that good clinical outcomes may correlate to electrical field capture of either striatal gray matter or of white matter fibers connecting OFC to thalamus.