A group effect for left dorsal striatum (A, column 1) connectivity with rostral anterior cingulate cortex (rACC; A, column 2) was driven by reduced connectivity in obsessive compulsive disorder patients (OCD) compared to healthy controls (HC). Note: A group × age interaction was also observed for left dorsal striatal connectivity to nearby region of the rostral anterior cingulate cortex (A, column 3), driven by reduced connectivity in the youngest patients to matched controls (B). Left dorsal striatal connectivity to rostral anterior cingulate cortex inversely correlated with symptom severity in child patients (C). Group differences and group × age interactions displayed in standard neuroanatomical space (Montreal Neurological Institute) at a threshold of p < .005, uncorrected. CYBOCS P: Children's Yale-Brown Obsessive Compulsive Scale, Present score.