Dissociative symptoms commonly are associated with exposure to traumatic stress. Preliminary evidence from functional magnetic resonance imaging-based analysis (fMRI) of neural activation during dissociative symptom provocation in patients with PTSD or DID has implicated certain key structures involved in the generation of dissociative symptoms. Given the presumed region-to-region neural interplay implicit within this model, the investigators believe the use of intrinsic functional connectivity MRI (fcMRI) represents a valuable next line of investigation into the neurobiology of traumatic dissociation. The investigators also believe that a genetic approach holds promise as another converging line of inquiry into our understanding of traumatic dissociation.