Cognitive Inflexibility Shares Across Schizophrenia and Obsessive–Compulsive Disorder: A Task-Based Functional MRI Study

Abstract Background and Hypothesis Schizo-obsessive comorbidity (SOC), defined as obsessive–compulsive symptoms (OCS) in schizophrenia (SCZ), is linked to severe psychopathology and poor prognosis. Schizophrenia and obsessive–compulsive disorder (OCD) share cognitive impairments, particularly in inhibition and cognitive flexibility, which may underlie SOC. However, little is known regarding the underlying neural mechanisms of SOC. We aimed to directly compare the inhibition- and cognitive flexibility-related neural activations between patients with SOC, SCZ, OCD, and healthy controls (HCs). Study Design Twenty-eight patients with SOC, 33 SCZ patients, 30 OCD patients, and 33 HCs undertook fMRI while performing the combined shifting go/no-go task. We analyzed the shifting-related (shift vs go) and stopping-related (no-go vs go) activations among the different diagnostic groups. Study Results Compared to HCs, the 3 clinical groups showed significant shifting-related hypoactivation in the left postcentral gyrus, left paracentral lobule, left supplementary motor area, and right superior frontal gyrus, with SOC exhibiting significantly lower activation than SCZ and OCD patients. Regarding stopping, OCD patients showed significant hyperactivation in the left precuneus compared with SCZ patients and HCs. Like OCD patients, SOC patients also exhibited greater hyperactivation than SCZ patients. Behaviorally, SOC and SCZ patients made significantly more commission errors than OCD patients, with SCZ also having more commission errors than HCs. Furthermore, SOC and SCZ made more shifting errors than HCs; and SOC made more shifting errors than SCZ and OCD patients. Conclusions All 3 clinical groups shared cognitive inflexibility. Moreover, the presence of the 2 features appears to amplify the neural alterations, implicating “additive effects.”