Localization Of Cerebral Functional Deficits In Patients With Obsessive-compulsive Disorder Using FMRI

PART I. Brain dysfunction during Stroop task in patients withobsessive-compulsive disorder：a functional MRI studyBackgrounds and objective:Obsessive-compulsive disorder （OCD） is a debilitating neuropsychiatric disorder with anapproximate lifetime prevalence of2–3%. This disorder is characterized by persistentintrusive thoughts （obsessions） and/or repetitive behaviors （compulsions）. Despite its highprevalence, the exact etiology and pathogenesis of OCD remain unclear. The purpose of thisstudy was to investigate brain dysfunction during Stroop task in obsessive-compulsivepatients by using functional MRI.Methods：Thirteen obsessive compulsive patients and fifteen healthy controls（matched with age,sex and extent of education）underwent functional MRI when they performed a ChineseStroop test. The imaging data were analyzed and compared with SPM8software to acquirethe locations of activation regions.Results：To complete the simple word reading Stroop test, OCD patients need to activate morebrain areas such as left parahippocampal gyrus, paracentral lobule, thalamus, etc. Thedecreased activation was demonstrated in left anterior cingulate cortex and caudate nucleus.There were scarcely any regions in which the OCD patients showed stronger activation thanthe healthy controls during the color naming Stroop test. But the OCD showed weakeractivation in the orbitofrontal cortex, anterior cingulate cortex and caudate.Conclusion:The OCD patients may have brain dysfunction in orbitofrontal cortex, anterior cingulatecortex and caudate, and abnormality of orbitofronto-striatal circuits might play a critical rolein pathophysiology of OCD. PART II. Localization of cerebral functional deficits in patients withobsessive-compulsive disorder: A resting-state fMRI studyBackgrounds and objective:Abnormality of orbitofronto-striatal circuits was postulated in obsessive-compulsivedisorder （OCD）. The aim of this study is to test the abnormality hypothesis oforbitofronto-striatal circuits and explore whether there are any other dysfunctional brainregions in OCD using a resting-state functional magnetic resonance imaging （fMRI）, andfurther investigate the relationship between the whole-brain voxel-based spontaneousneuronal activity of patients with OCD and clinical characteristics.Methods：23patients with OCD and23age-and gender-matched normal controls were examinedusing resting-state fMRI, and amplitude of low-frequency fluctuation （ALFF） approachmethod were used to analyze fMRI data. The fMRI data were processed by SPM8soft andREST soft based on MATLAB2009b. One-sample t-test using SPM8was performed withineach group to explore where in the cerebral regions may present with the ALFF differed fromthe value of1. In order to examine the ALFF diference between the two groups, two-samplet-test was performed in SPM8, results were displayed using REST software with a thresholdof P<0.01with multiple comparison corrected by AlphaSim methods. We also performed awhole-brain voxel-based correlative analysis between ALFF values and clinical indexes suchas Y-BOCS score, disease duration. Given the exploratory nature of the study, we adopted amore liberal statistical threshold (P_uncorrected<0.005with a minimum cluster size of270mm³).Results：23patients with OCD and23normal controls completed the fMRI scans.2patients and2controls were excluded because of excessive head motion. The results were present for21patients with OCD and21normal controls. No significant differences were found between thetwo groups in gender, age, height, weight and education. two-sample t-test showed that,compared to the normal controls, patients with OCD had significantly increased ALFF inmultiple areas including bilateral OFC, ACC, as well as decreased ALFF in several brainareas including the parietal and bilateral cerebellum （P<0.01, corrected）. In addition, theALFF values in bilateral OFC were positively correlated with total Y-BOCS scores （Left OFC:R²=0.372, P=0.003; Right OFC: R²=0.513, P<0.001）. Conclusion:In conclusion, the present study observed the abnormal spontaneous activities in patientswith OCD by analyzing resting-state fMRI data, including increased ALFF in the bilateralOFC and ACC as well as decreased ALFF in the bilateral cerebellum and parietal cortex. Ourfindings suggest that the abnormal spontaneous activity of these brain regions may implicatethe underlying pathophysiology in patients with OCD. Future experimentations are expectedto combine different modalities to provide more information about the disorder.