Abnormal spontaneous neural activity in hippocampal-cortical system of patients with obsessive-compulsive disorder and its potential for diagnosis and prediction of early treatment response

Abstract

Early brain functional changes induced by pharmacotherapy in patients with obsessive-compulsive disorder (OCD) in relation to drugs per se or because of the impact of such drugs on the improvement of OCD remain unclear. Moreover, no neuroimaging biomarkers are available for diagnosis of OCD and prediction of early treatment response. We performed a longitudinal study involving 34 patients with OCD and 36 healthy controls (HCs). Patients with OCD received 5-week treatment with paroxetine (40 mg/d). Resting-state functional magnetic resonance imaging (fMRI), regional homogeneity (ReHo), support vector machine (SVM), and support vector regression (SVR) were applied to acquire and analyze the imaging data. Compared with HCs, patients with OCD had higher ReHo values in the right superior temporal gyrus and bilateral hippocampus/parahippocampus/fusiform gyrus/cerebellum at baseline. ReHo values in the left hippocampus and parahippocampus decreased significantly after treatment. The reduction rate (RR) of ReHo values was positively correlated with the RRs of the scores of Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and obsession. Abnormal ReHo values at baseline could serve as potential neuroimaging biomarkers for OCD diagnosis and prediction of early therapeutic response. This study highlighted the important role of the hippocampal-cortical system in the neuropsychological mechanism underlying OCD, pharmacological mechanism underlying OCD treatment, and the possibility of building models for diagnosis and prediction of early treatment response based on spontaneous activity in the hippocampal-cortical system.

Keywords: hippocampus; obsessive–compulsive disorder; parahippocampus; regional homogeneity; support vector machine.

FIGURE 1

Brain regions with significant difference in ReHo values between patients with OCD and healthy controls. Compared with healthy controls, patients with OCD had higher ReHo values in the right superior temporal gyrus and bilateral hippocampus/parahippocampus/fusiform gyrus/cerebellum. ReHo, regional homogeneity; OCD, obsessive–compulsive disorder.

FIGURE 2

(A) The accuracy of classification of seven combinations of ReHo values. A represents the right hippocampus/parahippocampus/fusiform gyrus/cerebellum; B represents the left hippocampus/parahippocampus/fusiform gyrus/cerebellum; C represents the right superior temporal gyrus; D represents the right hippocampus/parahippocampus/fusiform gyrus/cerebellum and left hippocampus/parahippocampus/fusiform gyrus/cerebellum; E represents the right hippocampus/parahippocampus/fusiform gyrus/cerebellum and right superior temporal gyrus; F represents the left hippocampus/parahippocampus/fusiform gyrus/cerebellum and right superior temporal gyrus; G represents the right hippocampus/parahippocampus/fusiform gyrus/cerebellum, left hippocampus/parahippocampus/fusiform gyrus/cerebellum, and right superior temporal gyrus. (B) SVM analysis of the combination of ReHo values in the right hippocampus/parahippocampus/fusiform gyrus/cerebellum and left hippocampus/parahippocampus/fusiform gyrus/cerebellum. Sensitivity = 73.53%, specificity = 91.67%, and accuracy = 82.86%. SVM, support vector machines; ReHo, regional homogeneity.

FIGURE 3

Brain regions showing significant changes in ReHo values after treatment. Compared with the baseline data, patients with OCD showed significantly decreased ReHo values in the left hippocampus and parahippocampus after a 5-week paroxetine treatment. ReHo, regional homogeneity; OCD, obsessive–compulsive disorder.

FIGURE 4

Support vector regression results suggested that the ReHo values in the left hippocampus, parahippocampus, fusiform gyrus, and cerebellum at baseline can be used to predict early therapeutic response. (A) SVR results showed a positive correlation between the actual and predicted RRs in the total scores of Y-BOCS (r = 0.590, p = 0.002). (B) SVR results showed a positive correlation between the actual and predicted RRs in scores of obsession (r = 0.661, p < 0.001). (C) SVR results showed a positive correlation between the actual and predicted RRs in the scores of compulsion (r = 0.595, p = 0.002). SVR, support vector regression; ReHo, regional homogeneity; RR, reduction rate.