The Role Of Hippocampus Connectivity In Regulating The Relationship Between Obsessive-compulsive Symptoms And Anxiety In Patients With Obsessive-compulsive Disorder

BackgroundObsessive-compulsive disorder(OCD)is mainly performed in obsession and compulsion,and is associated with severe anxiety.The interaction of obsessive-compulsive and anxious symptoms has affecting the clinical treatment and prognosis of patients.The neurological mechanism of comorbidity in patients with OCD is still unclear.However,hippocampus is closely related to the generation and maintenance of anxiety.The changes of hippocampus functional connectivity(FC)are still unclear in OCD patients.Whether the hippocampus FC network is associated with comorbidity of obsessive-compulsive and anxious symptoms needs further exploration.ObjectivesThe purpose of this study was to investigate whether the hippocampus FC network was abnormal in OCD patients and to clarify the neural mechanism of comorbidity between obsessive-compulsive and anxious symptoms.MethodsThe 45 patients who met the OCD criteria in the DSM-IV-TR(Diagnostic and Statistical Manual of Mental Disorders,Fourth edition,text revision)and 42 normal controls(NCs)matched in age,gender and education were included.All subjects of two groups were collected the data of blood oxygen level dependent(BOLD)resting-state functional magnetic resonance(MRI)underwent 3.0 T Siemens MRI.The obsessive-compulsive symptoms were assessed by the Yale-Brown Obsessive-Compulsive Scale(Y-BOCS).The beck anxiety inventory(BAI)was applied to assess anxious state.On the Matlab 2013 b platform,the REST toolkit was used to extract the bilateral hippocampus from the AAL atlas as the regions of interest(ROI).The bilateral hippocampus was used as the seed regions for the FC analysis in the whole brain.Independent sample t-test was used to compare the FC network between OCD and NCs group.In addition,multivariate linear regression equations were used to analyze the neural mechanism and interaction effect of obsessive-compulsive symptom(including Y-BOCS total scores,obsessive scores and compulsive scores)and anxious symptom(Beck Anxiety Inventory scores)on the hippocampus FC network using SPM12.In addition,this study also used a method of mediation analysis to explore whether the hippocampus FC network mediates the relationship between obsessive-compulsive symptoms and anxiety symptoms in patients with OCD.ResultsThere was no significant difference between the two groups in age,gender,education and FD head motion parameters.However,the BAI scores of OCD group was significantly higher than the NCs group.In the comparison of the hippocampus FC network between the two groups,abnormal regions were found in the middle temporal gyrus(MTG),anterior cingulate cortex(ACC)and cerebellum.The main effect of anxiety on the hippocampus FC network are mainly distributed in the frontal and temporal lobes.The main effect regions of obsession are mainly MTG,inferior parietal gyrus(IPG)and dorsolateral prefrontal lobe.The main effect brain regions of anxiety and obsession are positive.The main effect brain regions of compulsion are mainly negative,mainly located in the precentral cortex,postcentral cortex,and supplementary motor area(SMA).The brain regions of the interaction between obsession and anxiety are mainly located in the MTG,IPG and middle frontal gyrus(MFG).There was no significant regions in interactive analysis between compulsive,Y-BOCS total scores and anxious symptoms.The total scores of obsessive-compulsive behavior and obsessive-compulsive symptoms were not found to have significant interaction with the symptoms of anxiety.More importantly,mediation analysis showed that the FC between hippocampus and MTG mediates the relationship between obsessive-compulsive symptoms and anxious symptoms in OCD patients.ConclusionsIn the interaction between obsessive-compulsive symptoms and anxiety symptoms,some brain regions including temporal lobe,frontal lobe and parietal lobe were involved in the common neural mechanism.Among them,the FC between hippocampus and MTG indirectly regulated the relationship between obsession and anxiety symptoms.These findings extended our understanding of the mechanisms underlying anxiety in patients with OCD and shed new light on potential therapeutic targets.