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Aim:Although many neuroimaging studies of obsessive-compulsive disorder (OCD) have reported broad abnormalities in gray matter (GM), their results remain inconsistent. One reason for this inconsistency could be the heterogeneity of OCD. In the present study, we aimed to classify alterations in brain anatomy by OCD subtype.Methods: Magnetic resonance imaging examinations of 37 OCD patients and 37 matched healthy controls were conducted using a 3.0-Tesla scanner. In the voxel-based morphometric procedure, preprocessed GM structural images were used to compare the two groups, and multiple regression analysis was used to investigate the correlation between regional GM volume in OCD patients and the OCD symptom dimension type assessed by using the Dimensional Yale-Brown Obsessive-Compulsive Scale. Results:We found significant reductions in GM volume in broad areas of the left prefrontal, right orbitofrontal, right parietal, right temporal, and right posterior cingulate cortex in the OCD patients compared to healthy controls. In addition, we found specific negative correlations between symptomatic dimension scores and regional GM volumes, mainly as decreased right cerebellum in 'aggression/checking' and decreased right insula in 'contamination/washing'. Conclusion:The pathophysiology of OCD may involve widely distributed neural systems. Moreover, there are distinct correlations among symptomatic dimensions and structural abnormalities.

BackgroundImpaired cognitive flexibility has been implicated in the genetic basis of obsessive-compulsive disorder (OCD). Recent endophenotype studies of OCD showed neural inefficiency in the cognitive control network and interference by the limbic network of the cognitive control network. Exploring the relationship between the functional brain network and impaired cognitive flexibility may provide novel information about the neurobiological basis of OCD.MethodsWe obtained resting-state functional magnetic resonance imaging (rsfMRI) scans and measured the cognitive flexibility of 37 medication-free OCD patients and 40 healthy control (HC) participants using the Wisconsin Card Sorting Test (WCST). We explored the difference between OCD and HC groups in the functional brain network related to impaired cognitive flexibility from the amygdala and dorsal striatal regions of interest (ROIs) by using a seed-based approach.ResultsSignificant differences between the OCD and HC groups were identified in the resting state functional network from the dorsal caudate. Increased functional connectivity from the dorsal caudate to the dorsal anterior cingulate cortex (dACC) and anterior insula (AI) was associated with poorer cognitive flexibility in the OCD group, but better cognitive flexibility in the HC group.ConclusionsThese results provide evidence that the impaired cognitive flexibility of OCD may be associated with dysfunctions of the brain network from the dorsal caudate (DC) to important nodes of the salience network. Our results extend the neuropsychological model of OCD by showing intrinsically different associations between OCD and HC in functional network and cognitive flexibility.

Recent evidence suggests that presupplementary motor area (pre-SMA) and inferior frontal gyrus (IFG) play an important role in response inhibition. However, no study has investigated the relationship between these brain networks at resting-state and response inhibition in obsessive-compulsive disorder (OCD). We performed resting-state functional magnetic resonance imaging scans and then measured the response inhibition of 41 medication-free OCD patients and 49 healthy control (HC) participants by using the stop-signal task outside the scanner. We explored the differences between OCD and HC groups in the functional connectivity of pre-SMA and IFG associated with the ability of motor response inhibition. OCD patients showed a longer stop-signal reaction time (SSRT). Compared to HC, OCD patients exhibit different associations between the ability of motor response inhibition and the functional connectivity between pre-SMA and IFG, inferior parietal lobule, dorsal anterior cingulate cortex, insula, and anterior prefrontal cortex. Additional analysis to investigate the functional connectivity difference from the seed ROIs to the whole brain voxels revealed that, compared to HC, OCD exhibited greater functional connectivity between pre-SMA and IFG. Also, this functional connectivity was positively correlated with the SSRT score. These results provide additional insight into the characteristics of the resting-state functional connectivity of the regions belonging to the cortico-striato-thalamo-cortical circuit and the cingulo-opercular salience network, underlying the impaired motor response inhibition of OCD. In particular, we emphasize the importance of altered functional connectivity between pre-SMA and IFG for the pathophysiology of motor response inhibition in OCD.