Altered anterior cingulate cortex functional connectivity in treatment-naïve obsessive-compulsive disorder: a resting-state fMRI study

Objective To investigate the anterior cingulate cortex (ACC) resting-state functional connectivity patterns in OCD patients who have not yet received therapy and analyze how they relate to the intensity of their clinical symptoms. Methods Resting-state fMRI data were acquired from 46 medication-naïve participants with OCD and 33 demographically comparable neurotypical control subjects. The region of focus for the seed-based whole-brain functional connectivity investigation was bilateral ACC. Relationships between aberrant connections and clinical characteristics measured by the Y-BOCS, HAMD-17, and HAMA were investigated using Pearson’s correlation coefficient and partial correlation analysis. Results Key findings (OCD patients vs. healthy controls): Increased functional connectivity (FC) in OCD patients: Right insula (Brodmann area 48), Right hippocampus (BA 20), Right fusiform gyrus (BA 37); Decreased FC involving the anterior cingulate cortex (ACC) with: Right supplementary motor area (SMA, BA 32), Left inferior frontal gyrus (IFG, BA 47) (AlphaSim corrected, P < 0.05). Clinical association: There was a significant positive relationship between Y-BOCS total scores (a measure of OCD symptom severity) and FC strength linking the left IFG to the ACC (r = 0.351, P = 0.017). In practical terms, greater symptom severity is associated with stronger coupling between these two regions. No other clear brain-behavior relationships were found in the other regions examined. Conclusion Treatment-naïve OCD patients demonstrate distinct ACC functional connectivity alterations involving cognitive control, motor planning, and limbic processing regions. The specific association between left inferior frontal gyrus (IFG)-ACC connectivity and symptom severity suggests that this pathway may serve as a neurobiological marker for OCD pathophysiology.