Cognitive Cerebellum Structure and Functional Connectivity in Relation to Executive Functions in Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) has been primarily linked to abnormalities within the cortico-striato-thalamo-cortical circuit; however, recent evidence suggests that the posterior cerebellum may contribute to the executive dysfunction observed in the disorder. In 56 adults (28 OCD, 28 controls), we assessed executive functions using the BANFE-2 battery and integrated structural MRI (T1) and resting-state fMRI. Although the Global Executive Index did not differ significantly between groups, patients with OCD showed significantly lower scores in the inhibitory control/decision-making domain relative to controls. We quantified cortical thickness and volume (% intracranial volume) in Crus I/II and lobule VI using CERES and examined resting-state functional connectivity (seed-to-voxel) in CONN, adjusting for age, sex, medication, and depression. Compared with controls, patients with OCD showed reduced bilateral cortical thickness in Crus I/II and lobule VI (false discovery rate-corrected q < 0.05; β_OCD - Control = -0.27 to -0.59; ηp² = 0.34-0.55), with no significant volumetric differences after correction for multiple comparisons. Functional connectivity results revealed a mixed pattern, including focal hyperconnectivity (e.g., left Crus I with primary auditory cortex; left Crus II with occipital cortex) and widespread intracerebellar hypoconnectivity. In addition, significant Group × executive-function interactions (p-family-wise error < 0.05) emerged mainly for bilateral Crus I (Global Executive Index and working memory/flexibility) and left lobule VI (inhibition/decision-making), indicating that the relationship between cerebellar connectivity and executive performance differs in OCD relative to controls. These findings support an expanded model of executive circuits in OCD that incorporates the posterior cerebellum as a relevant node.