Functional connectivity abnormalities of brain networks in obsessive-compulsive disorder: a systematic review

Obsessive-compulsive disorder (OCD) is characterized by cognitive abnormalities encompassing several executive processes. Neuroimaging studies highlight functional abnormalities of executive fronto-parietal network (FPN) and default-mode network (DMN) in OCD patients, as well as of the prefrontal cortex (PFC) more specifically. We aim at assessing the presence of functional connectivity (FC) abnormalities of intrinsic brain networks and PFC in OCD, possibly underlying specific computational impairments and clinical manifestations. A systematic review of resting-state fMRI studies investigating FC was conducted in unmedicated OCD patients by querying three scientific databases (PubMed, Scopus, PsycInfo) up to July 2022 (search terms: obsessive-compulsive disorder AND resting state AND fMRI AND function* *connect* AND task-positive OR executive OR central executive OR executive control OR executive-control OR cognitive control OR attenti* OR dorsal attention OR ventral attention OR frontoparietal OR fronto-parietal OR default mode AND network* OR system*). Collectively, 20 studies were included. A predominantly reduced FC of DMN - often related to increased symptom severity - emerged. Additionally, intra-network FC of FPN was predominantly increased and often positively related to clinical scores. Concerning PFC, a predominant hyper-connectivity of right-sided prefrontal links emerged. Finally, FC of lateral prefrontal areas correlated with specific symptom dimensions. Several sources of heterogeneity in methodology might have affected results in unpredictable ways and were discussed. Such findings might represent endophenotypes of OCD manifestations, possibly reflecting computational impairments and difficulties in engaging in self-referential processes or in disengaging from cognitive control and monitoring processes.

Automated summary

Obsessive-compulsive disorder (OCD) is associated with cognitive abnormalities in executive processes. Neuroimaging studies have shown functional abnormalities in the executive fronto-parietal network (FPN), default-mode network (DMN), and prefrontal cortex (PFC) in OCD patients. This systematic review found reduced DMN functional connectivity, increased FPN intra-network connectivity, and hyper-connectivity of right-sided prefrontal links in OCD patients. These findings may represent endophenotypes reflecting computational impairments and difficulties in self-referential processes and cognitive control.