Heightened degree connectivity of the striatum in obsessive-compulsive disorder induced by symptom provocation

Background: Neurosurgical intervention studies have provided direct evidence that the ventral striatum/nucleus accumbens (NAc) mediates symptoms of obsessive-compulsive disorder (OCD), yet meta-analysis of functional neuroimaging studies using symptom provocation revealed no striatal activation differences, and the existing studies reporting hyperactivity found abnormalities in dorsal but not ventral striatal subdivisions. Resting-state neuroimaging evidence holds that corticostriatal areas are more connected both locally and to distant regions, but the functional inferences to be drawn from these altered network characteristics regarding the present experience of OCD symptoms remain limited. Methods: The present study tested whether symptom provocation induces abnormally high striatal network connectivity using two independent datasets of unmedicated patients with OCD. One study (14 patients, 14 matched controls) required passive viewing of OC-related, emotionally aversive and neutral pictures, the other (21 patients, 21 controls) involved self-referential evaluation of the same picture types, as well as distraction from these stimuli (engagement in a simple task). Results: Heightened local connectivity of the dorsal striatum occurred during passive viewing of briefly presented OC-related pictures in patients, however group differences were also observed in a neutral control condition. In contrast, distracted symptom provocation selectively yielded local connectivity differences of the ventral striatum, as heightened NAc connectivity to its immediate neighborhood was exclusively observed when OC-related pictures were accompanied by concurrent task demands. Limitations: Small samples sizes. Conclusions: In moderately affected patients with OCD, symptom provocation induces a discrete, condition specific network abnormality anchored in NAc, the location targeted by deep brain stimulation for refractory patients with OCD.