Reduced gray matter volume of dorsal cingulate cortex in patients with obsessive-compulsive disorder: a voxel-based morphometric study

Aims: Previous morphometric studies using magnetic resonance imaging (MRI) have revealed structural brain abnormalities in obsessive–compulsive disorder (OCD). The aim of the present study was to investigate the alterations in brain structure of patients with OCD using a voxel‐based morphometry (VBM) method. Methods: Sixteen patients with OCD free of comorbid major depression, and 32 sex‐ and age‐matched healthy subjects underwent MRI using a 1.5‐T MR scanner. OCD severity was assessed with the Yale–Brown Obsessive–Compulsive Scale (mean ± SD: 22 ± 7.6; range: 7–32). MR images were spatially normalized and segmented using the VBM5 package ( http://dbm.neuro.uni‐jena.de/vbm/ ). Statistical analysis was performed using statistical parametric mapping software. Results: Significant reductions in regional gray matter volume were detected in the left caudal anterior cingulate cortex and right dorsal posterior cingulate cortex in the patients with OCD as compared to healthy controls (uncorrected, P < 0.001). No significant differences in white matter volumes were observed in any brain regions of the patients. No significant correlation between Yale–Brown Obsessive–Compulsive Scale score and regional gray matter or white matter volume was observed. Conclusions: Regional gray matter alteration in the dorsal cingulate cortex, which is suggested to play a role in non‐emotional cognitive processes, may be related to the pathophysiology in OCD.     

Regional cerebral blood flow abnormalities in early-onset obsessive-compulsive disorder: an exploratory SPECT study

OBJECTIVE: Recent epidemiological and clinical data suggest that obsessive-compulsive disorder (OCD) may be subtyped according the age of onset of obsessive-compulsive symptoms. The regional cerebral blood flow (rCBF) single photon emission computed tomography (SPECT) technique was used to investigate whether the pathophysiology of OCD differs between early- and late-onset OCD subjects. METHOD: Resting rCBF was measured in 13 early-onset (<10 years) and 13 late-onset (>12 years) adult OCD subjects and in 22 healthy controls. Voxel-based rCBF comparisons were performed with statistical parametric mapping. RESULTS: Early-onset OCD cases showed decreased rCBF in the right thalamus, left anterior cingulate cortex, and bilateral inferior prefrontal cortex relative to late-onset subjects (p < .0005, uncorrected for multiple comparisons). Relative to controls, early-onset cases had decreased left anterior cingulate and right orbitofrontal rCBF, and increased rCBF in the right cerebellum, whereas late-onset subjects showed reduced right orbitofrontal rCBF and increased rCBF in the left precuneus. In early-onset subjects only, severity of obsessive-compulsive symptoms correlated positively with left orbitofrontal rCBF. CONCLUSIONS: rCBF differences in frontal-subcortical circuits between early-onset and late-onset OCD subjects were found, both in location and direction of changes. These results provide preliminary evidence that brain mechanisms in OCD may differ depending on the age at which symptoms are first expressed.     

Regional brain gray matter volume differences in patients with bipolar disorder as assessed by optimized voxel-based morphometry.

BACKGROUND: Structural magnetic resonance imaging (MRI) studies of regions of interest in brain have been inconsistent in demonstrating volumetric differences in subjects with bipolar disorder (BD). Voxel-based morphometry (VBM) provides an unbiased survey of the brain, can identify novel brain areas, and validates previously hypothesized regions. We conducted both optimized VBM, comparing MRI gray matter volume, and traditional VBM, comparing MRI gray matter density, in 11 BD subjects and 31 healthy volunteers. To our knowledge, these are the first VBM analyses of BD. METHODS: Segmented MRI gray matter images were normalized into standardized stereotactic space, modulated to allow volumetric analysis (optimized only), smoothed, and compared at the voxel level with statistical parametric mapping. RESULTS: Optimized VBM showed that BD subjects had smaller volume in left ventromedial temporal cortex and bilateral cingulate cortex and larger volume in left insular/frontoparietal operculum cortex and left ventral occipitotemporal cortex. Traditional VBM showed that BD subjects had less gray matter density in left ventromedial temporal cortex and greater gray matter density in left insular/frontoparietal operculum cortex and bilateral thalamic cortex. Exploratory analyses suggest that these abnormalities might differ according to gender. CONCLUSIONS: Bipolar disorder is associated with volumetric and gray matter density changes that involve brain regions hypothesized to influence mood.     

A voxel-based investigation of regional cerebral blood flow abnormalities in obsessive-compulsive disorder using single photon emission computed tomography (SPECT)

Several functional imaging studies have reported abnormalities of the orbitofrontal and anterior cingulate cortices, striatum and thalamus in obsessive-compulsive disorder (OCD). These studies have often been limited by small patient samples and image analysis methods that rely on region-of-interest (ROI) approaches. We have assessed resting regional cerebral blood flow with 99mTc-ECD SPECT in 26 unmedicated OCD patients and 22 healthy control subjects using the voxel-based Statistical Parametric Mapping method for data analysis. We found a significantly reduced ECD uptake in OCD patients relative to the control subjects in the right lateral orbitofrontal cortex, and in the left dorsal anterior cingulate cortex (P<0.001 two-tailed, uncorrected for multiple comparisons). There were significant positive correlations in the OCD group between the ECD uptake in the left lateral orbitofrontal cortex and ratings for obsessive-compulsive symptoms (OCS), and between the ECD uptake in the right medial orbitofrontal cortex and the ratings for both OCS and depressive symptoms. There were also unpredicted significant ECD uptake increases in the cerebellum in OCD patients, as well as a negative correlation between posterior cingulate ECD uptake and OCS severity (P<0.05, corrected for multiple testing). These results implicate specific subregions of the orbitofrontal and anterior cingulate cortices in the pathophysiology of OCD, as well as suggesting the involvement of other areas not usually included in ROI-based imaging studies. With the incorporation of voxel-based methods and the use of large patient samples, rCBF-SPECT studies may continue to provide valuable information about the functional anatomy of OCD.     

Brain structural abnormalities in psychotropic drug-naive pediatric patients with obsessive-compulsive disorder

OBJECTIVE: The authors investigated structural abnormalities in brain regions comprising cortical-striatal-thalamic-cortical loops in pediatric patients with obsessive-compulsive disorder (OCD). METHOD: Volumes of the caudate nucleus, putamen, and globus pallidus and gray and white matter volumes of the anterior cingulate gyrus and superior frontal gyrus were computed from contiguous 1.5-mm magnetic resonance images from 23 psychotropic drug-naive pediatric patients with OCD (seven male patients and 16 female patients) and 27 healthy volunteers (12 male subjects and 15 female subjects). RESULTS: Patients had smaller globus pallidus volumes than healthy volunteers, but the two groups did not differ in volumes of the caudate nucleus, putamen, or frontal white matter regions. Compared to healthy volunteers, patients had more total gray matter in the anterior cingulate gyrus but not the superior frontal gyrus. Total anterior cingulate gyrus volume correlated significantly and positively with globus pallidus volume in the healthy volunteers but not in patients. CONCLUSIONS: These findings provide evidence of smaller globus pallidus volume in patients with OCD without the potentially confounding effects of prior psychotropic drug exposure. Volumetric abnormalities in the anterior cingulate gyrus appear specific to the gray matter in OCD, at least at the gross anatomic level, and are consistent with findings of functional neuroimaging studies that have reported anterior cingulate hypermetabolism in the disorder.     

Changes in gray matter volume in patients with bipolar disorder.

BACKGROUND: Several lines of evidence suggest the presence of neurofunctional abnormalities in patients with bipolar disorder. These functional abnormalities may stem from structural pathology in these or connected brain regions. Previous studies have generally used a region of interest (ROI) approach to study morphologic changes in bipolar disorder with inconsistent findings among research groups, which may reflect differences in how ROIs are defined. Voxel based morphometry (VBM) allows a more exploratory analysis without the necessity for predefined anatomic boundaries. In this study we utilized VBM to compare gray matter volume between groups of bipolar and healthy subjects. METHODS: Thirty-two patients with bipolar disorder and 27 healthy subjects participated in structural magnetic resonance imaging (MRI) scans. MRI images were segmented, normalized to a standard stereotactic space, and compared on a voxel-by-voxel basis using statistical parametric mapping. RESULTS: Bipolar subjects showed increased gray matter in several regions including portions of anterior cingulate, ventral prefrontal cortex, fusiform gyrus and parts of the primary and supplementary motor cortex. Bipolar subjects showed decreased gray matter volume in superior parietal lobule. CONCLUSIONS: These data support suggestions that neurofunctional deficits are related to structural brain abnormalities in patients with bipolar disorder. The increased gray matter observed in several regions suggests that some affected areas may demonstrate volumetric expansion, at least in some patient populations.     

Anterior cingulate, gyrus rectus, and orbitofrontal abnormalities in elderly depressed patients: an MRI-based parcellation of the prefrontal cortex

OBJECTIVE: To examine structural abnormalities in subregions of the prefrontal cortex in elderly patients with depression, the authors explored differences in gray matter, white matter, and CSF volumes by applying a parcellation method based on magnetic resonance imaging (MRI). METHOD: Twenty-four elderly patients with major depression and 19 group-matched comparison subjects were studied with high-resolution MRI. Cortical surface extraction, tissue segmentation, and cortical parcellation methods were applied to obtain volume measures of gray matter, white matter, and CSF in seven prefrontal subregions: the anterior cingulate, gyrus rectus, orbitofrontal cortex, precentral gyrus, superior frontal cortex, middle frontal cortex, and inferior frontal cortex. RESULTS: Highly significant bilateral volume reductions in gray matter were observed in the anterior cingulate, the gyrus rectus, and the orbitofrontal cortex. Depressed patients also exhibited significant bilateral white matter volume reductions and significant CSF volume increases in the anterior cingulate and the gyrus rectus. Finally, the depressed group showed significant CSF volume reductions in the orbitofrontal cortex relative to the comparison subjects. None of the other regions examined revealed significant structural abnormalities. CONCLUSIONS: The prominent bilateral gray matter deficits in the anterior cingulate and the gyrus rectus as well as the orbitofrontal cortex may reflect disease-specific modifications of elderly depression. The differential pattern of abnormalities detected in the white matter and CSF compartments imply that distinct etiopathological mechanisms might underlie the structural cortical changes in these regions.     

Structural changes in the gray matter of unmedicated patients with obsessive-compulsive disorder: a voxel-based morphometric study

The aim of the current study was to use whole brain voxel-based morphometry（VBM）to assess the gray matter（GM）changes in unmedicated patients with obsessive-compulsive disorder（OCD）compared with normal controls.We compared the GM volumes in28 patients with 22 matched healthy controls using a1.5T MRI.Three-dimensional T1-weighted magnetic resonance images were obtained from all participants.VBM was performed to detect GM volume differences between the two groups.We detected increased regional GM volumes in the bilateral middle temporal gyri,bilateral middle occipital gyri,bilateral globus pallidus,right inferior parietal gyrus,left superior parietal gyrus,right parahippocampus,right supramarginal gyrus,right medial superior frontal gyrus,and left inferior frontal opercular cortex in the OCD patients relative to controls（P〈0.001,uncorrected,cluster size〉100 voxels）.No decreased GM volume was found in the OCD group compared with normal controls.Our findings suggest that structural changes in the GM are not limited to fronto-striato-thalamic circuits in the pathogenesis of OCD.Temporo-parietal cortex may also play an important role.     

A voxel-based morphometric MRI study of stabilized obsessive-compulsive adolescent patients

Background

The aim of this study was to determine whether treated stabilized adolescents with obsessive-compulsive disorder (OCD) present brain structure differences in comparison with healthy control subjects.

Methods

Twenty-seven adolescents with already-treated OCD and 27 healthy controls matched by age, sex and estimated intellectual level were assessed by means of psychopathological scales and magnetic resonance imaging (MRI). Axial three-dimensional T1-weighted images were obtained in a 1.5 T scanner and analyzed using optimized voxel-based morphometry (VBM).

Results

Compared with controls, stabilized patients with OCD did not present any statistical differences in the whole brain. However, a small volume correction analysis yielded significant results that survived correction for multiple comparisons, showing decreased white matter (WM) volume in a small area of the parietal cortex (t = 3.39, p = 0.045 FWE (family wise error)-corrected) of OCD patients in comparison with healthy controls. There was no significant correlation between decreased WM volume in the parietal cortex and obsessive-compulsive symptomatology.

Conclusion

There were no global significant differences in either gray matter (GM) or WM. Small differences were found between adolescent patients with stabilized OCD and healthy controls as regards in WM volume in right parietal areas. The parietal lobe may play a role in the pathophysiology of OCD, even in clinically stabilized patients.     

Gray matter volume differences and the effects of smoking on gray matter in schizophrenia

OBJECTIVE: Many studies have evaluated differences in gray matter volume in schizophrenia, but have not considered the possible effects of smoking, which is extraordinarily common in people with the illness. The present study used voxel-based morphometry (VBM) to examine differences in gray matter in subjects with schizophrenia and evaluate the effects of smoking on this measure. METHODS: Thirty-two subjects with schizophrenia (14 smokers, 18 non-smokers) and 32 healthy comparison subjects participated in the study. Whole brain, voxel-wise analyses of regional gray matter volume were conducted using voxel-based morphometry (VBM). RESULTS: Reduced gray matter was observed in the schizophrenia group in the orbitofrontal cortex, bilateral insula and superior temporal gyri (STG), bilateral dorsolateral prefrontal cortices (DLPFC), medial frontal gyrus, and cingulate gyrus. Within this group, smoking subjects had greater lateral prefrontal and STG gray matter volumes relative to non-smoking subjects. CONCLUSIONS: The finding of reduced gray matter volume in prefrontal and temporal regions in schizophrenia is consistent with prior anatomical tracing and whole-brain voxel-based studies. Greater gray matter volumes in smoking relative to non-smoking subjects with schizophrenia highlight a potential experimental confound in volumetric studies and suggests that smoking may be associated with a relative preservation of lateral prefrontal and temporal gray matter in schizophrenia.     

Anterior insular volume is larger in patients with obsessive-compulsive disorder

There has been increasing evidence indicating gray matter abnormalities in patients with obsessive-compulsive disorder (OCD). Several voxel-based morphometry (VBM) studies have reported volume changes in the insular cortex. Although there are distinct differences in the connectivity and functions in the anterior and posterior insular cortices, these two regions have never been distinguished in previous VBM studies. In this study, we adopted a region of interest (ROI) method to measure insular volume separately. We investigated insular volume in 32 drug-free patients with OCD and in 34 healthy controls using magnetic resonance imaging (MRI). Repeated measures multivariate analysis of covariance (MANCOVA) was conducted to examine the difference between the patients and the controls. Compared with the healthy controls, the patients had a significantly larger gray matter volume in the anterior insular cortex bilaterally (post hoc test, p = 0.036; left, p = 0.047; right). This is the first volumetric MRI study to separately investigate the anterior and posterior insular cortex volumes in non-medicated patients with OCD. The results suggest that the anterior insular cortex may be related to the pathophysiology of OCD.     

A proton MRSI study of brain N-acetylaspartate level after 12 weeks of citalopram treatment in drug-naive patients with obsessive-compulsive disorder

OBJECTIVE: Reductions in the level of N-acetylaspartate within subcortical structures of patients with obsessive-compulsive disorder (OCD) have been reported in several studies. However, there have been, as yet, no reports regarding N-acetylaspartate levels in the prefrontal cortex of adult drug-naive OCD patients. The authors used proton magnetic resonance spectroscopic imaging ((1)H-MRSI) to investigate regional N-acetylaspartate level abnormalities and changes after 12 weeks of pharmacotherapy with citalopram in drug-naive OCD patients. METHOD: Thirteen drug-naive OCD patients and 13 age- and sex-matched healthy comparison subjects were included in this study. N-acetylaspartate levels (obtained from ratios of N-acetylaspartate with creatine, choline, and creatine plus choline) in the prefrontal cortex, parietal cortex, anterior cingulate, posterior cingulate, frontal white matter, and parietal white matter were measured by (1)H-MRSI. In OCD patients, measurements were taken before and after 12 weeks of citalopram treatment. Correlations between N-acetylaspartate concentrations in regions of interest and clinical measures were also assessed. RESULTS: Drug-naive OCD patients exhibited significantly lower N-acetylaspartate levels in the prefrontal cortex, frontal white matter, and anterior cingulate at baseline than did comparison subjects. Significant increases in N-acetylaspartate level were detected in the prefrontal cortex and frontal white matter in OCD patients after 12 weeks of citalopram treatment. CONCLUSIONS: These data suggest that reductions in neuronal viability occur in the frontal region of OCD patients and that these reductions may be partly reversible.     

Neuroanatomical characteristics of geriatric apathy and depression: a magnetic resonance imaging study.

OBJECTIVE: Apathy is one of the most common late-life neuropsychiatric syndromes. The objective of our study was to examine the neuroanatomical correlates of apathy in older subjects with and without geriatric major depression (MDD). METHODS: Eighty-four subjects (43 patients with MDD and 41 normal comparison subjects) underwent comprehensive neuropsychiatric examination, physical examination, and high-resolution magnetic resonance imaging (MRI) brain scans on a 1.5T GE MRI scanner. Apathy was assessed using the Apathy Evaluation Scale. MRI image analyses included cortical surface extraction, tissue segmentation, and cortical parcellation methods to measure the gray and white matter volumes in two prefrontal subregions: the anterior cingulate and orbitofrontal cortex. RESULTS: The depressed group had smaller orbitofrontal gray matter volumes compared to the age-matched normal comparison group. The severity of apathy was associated with the decreased gray matter volume in the right anterior cingulate gray matter volumes using partial correlation and regression analyses after controlling for age, sex, and diagnosis. CONCLUSION: Apathy and depression were associated with different anatomical correlates in the prefrontal regions implicated in the regulation of cognition and emotion. Our findings offer new understanding of the neuroanatomical characteristics of apathy and depression in late life, and have broad implications for the neurobiology of behavior.     

Volumetric MRI study of key brain regions implicated in obsessive-compulsive disorder

Neuroanatomic abnormalities have been implicated in the pathophysiology of obsessive-compulsive disorder (OCD). To date, no study has measured the orbito-frontal cortex (OFC), anterior cingulate, caudate nucleus, and thalamus concurrently in first-episode patients. Thus, we performed a volumetric MRI study in patients who were treatment-naive and healthy controls focusing on the in vivo neuroanatomy of the whole brain, total gray and white matter volume, thalamus, caudate nucleus, anterior cingulate cortex, and OFC concurrently. The volumes of thalamus, caudate nucleus, anterior cingulate cortex, and OFC were measured in 12 OCD patients who were treatment-naive and 12 healthy control subjects. Anterior cingulate and OFC volumes included both white and gray matters. Volumetric measurements were made with T1-weighted coronal MRI images, with 1.5-mm-thick slices, at 1.5 T. The patients had increased white matter volume than healthy controls. The patient group had significantly smaller left and right OFC volumes and significantly greater left and right thalamus volumes compared with healthy controls. Anterior cingulate exhibited a near-significant difference between the patients and healthy controls on left side. Significant correlations were found between Y-BOCS scores and left OFC, and right OFC, and between Y-BOCS and left thalamus volumes in the patient group. In conclusion, our findings suggest that abnormalities in these areas may play an important role in the pathophysiology of OCD.     

White matter abnormalities in obsessive-compulsive disorder: a diffusion tensor imaging study

CONTEXT: Several neurobiological models of obsessive-compulsive disorder (OCD) posit a primary role for dysfunction of the anterior cingulate gyrus. Both functional and structural neuroimaging studies have implicated anterior cingulate gray matter abnormalities in the pathophysiology of OCD, but there has been little investigation of the anterior cingulate white matter in this disorder. OBJECTIVE: To test the hypothesis that patients with OCD have abnormal white matter microstructure in the anterior cingulate gyrus compared with healthy volunteers as inferred from diffusion tensor imaging. Additional analyses examined group differences in white matter integrity across the entire brain. DESIGN, SETTING, AND PARTICIPANTS: Fifteen patients with a DSM-IV diagnosis of OCD and 15 healthy volunteers matched for age, sex, and handedness underwent diffusion tensor imaging and structural magnetic resonance imaging examinations. Fractional anisotropy (FA), a robust intravoxel measure of water self-diffusion, was compared between groups on a voxel-by-voxel basis in the anterior cingulate white matter after standardization in Talairach space. MAIN OUTCOME MEASURES: Clinical ratings of symptom severity (ie, Yale-Brown Obsessive-Compulsive Scale) and FA. RESULTS: Compared with healthy volunteers, patients demonstrated significantly lower FA bilaterally in 3 areas of the anterior cingulate gyrus white matter. Additional analyses conducted across the rest of the brain white matter revealed lower FA bilaterally in the parietal region (supramarginal gyri), right posterior cingulate gyrus, and left occipital lobe (lingual gyrus). No areas of significantly higher FA were observed in patients compared with healthy volunteers. Lower FA in the parietal region correlated significantly with higher Yale-Brown Obsessive-Compulsive Scale scores. CONCLUSIONS: These preliminary findings provide evidence of an abnormality that involves the anterior cingulate white matter in the pathogenesis of OCD and are consistent with neurobiological models that posit a defect in connectivity in the anterior cingulate basal ganglia-thalamocortical circuit. White matter abnormalities in other brain regions may also be implicated in the neurobiology of OCD.     

Volumetric investigation of the frontal-subcortical circuitry in patients with obsessive-compulsive disorder

The pathophysiology of obsessive-compulsive disorder (OCD) is thought to involve disturbance of the frontal-subcortical circuitry. To investigate the morphological characteristics of this circuitry, we examined the volume of the orbitofrontal cortex, anterior cingulate, thalamus, caudate, and the putamen in 36 age- and sex-matched OCD patients and normal control subjects using three-dimensional magnetic resonance (MR) brain imaging. The left orbitofrontal volumes were found to be significantly smaller in the OCD patients and showed significant negative correlations with obsessive-compulsive symptom severity. These findings suggest that a structural abnormality of this brain region is implicated in the pathophysiology of OCD.     

Gray matter volumes in obsessive-compulsive disorder before and after fluoxetine or cognitive-behavior therapy: a randomized clinical trial

Serotonin reuptake inhibitors and cognitive-behavior therapy (CBT) are considered first-line treatments for obsessive-compulsive disorder (OCD). However, little is known about their modulatory effects on regional brain morphology in OCD patients. We sought to document structural brain abnormalities in treatment-naive OCD patients and to determine the effects of pharmacological and cognitive-behavioral treatments on regional brain volumes. Treatment-naive patients with OCD (n=38) underwent structural magnetic resonance imaging scan before and after a 12-week randomized clinical trial with either fluoxetine or group CBT. Matched-healthy controls (n=36) were also scanned at baseline. Voxel-based morphometry was used to compare regional gray matter (GM) volumes of regions of interest (ROIs) placed in the orbitofrontal, anterior cingulate and temporolimbic cortices, striatum, and thalamus. Treatment-naive OCD patients presented smaller GM volume in the left putamen, bilateral medial orbitofrontal, and left anterior cingulate cortices than did controls (p<0.05, corrected for multiple comparisons). After treatment with either fluoxetine or CBT (n=26), GM volume abnormalities in the left putamen were no longer detectable relative to controls. ROI-based within-group comparisons revealed that GM volume in the left putamen significantly increased (p<0.012) in fluoxetine-treated patients (n=13), whereas no significant GM volume changes were observed in CBT-treated patients (n=13). This study supports the involvement of orbitofronto/cingulo-striatal loops in the pathophysiology of OCD and suggests that fluoxetine and CBT may have distinct neurobiological mechanisms of action.     

Regional gray matter reduction and theory of mind deficit in the early phase of schizophrenia: a voxel‐based morphometric study

Objective: We tested the association between theory of mind (ToM) performance and structural changes in the brains of patients in the early course of schizophrenia. Method: Voxel‐based morphometry (VBM) data of 18 patients with schizophrenia were compared with those of 21 controls. ToM skills were assessed by computerized faux pas (FP) tasks. Results: Patients with schizophrenia performed significantly worse in FP tasks than healthy subjects. VBM revealed significantly reduced gray matter density in certain frontal, temporal and subcortical regions in patients with schizophrenia. Poor FP performance of schizophrenics correlated with gray matter reduction in the left orbitofrontal cortex and right temporal pole. Conclusion: Our data indicate an association between poor ToM performance and regional gray matter reduction in the left orbitofrontal cortex and right temporal pole shortly after the onset of schizophrenia.     

Relationship between symptom dimensions and brain morphology in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is known as a clinically heterogeneous disorder characterized by symptom dimensions. Although substantial numbers of neuroimaging studies have demonstrated the presence of brain abnormalities in OCD, their results are controversial. The clinical heterogeneity of OCD could be one of the reasons for this. It has been hypothesized that certain brain regions contributed to the respective obsessive-compulsive dimensions. In this study, we investigated the relationship between symptom dimensions of OCD and brain morphology using voxel-based morphometry to discover the specific regions showing alterations in the respective dimensions of obsessive-compulsive symptoms. The severities of symptom dimensions in thirty-three patients with OCD were assessed using Obsessive-Compulsive Inventory-Revised (OCI-R). Along with numerous MRI studies pointing out brain abnormalities in autistic spectrum disorder (ASD) patients, a previous study reported a positive correlation between ASD traits and regional gray matter volume in the left dorsolateral prefrontal cortex and amygdala in OCD patients. We investigated the correlation between gray and white matter volumes at the whole brain level and each symptom dimension score, treating all remaining dimension scores, age, gender, and ASD traits as confounding covariates. Our results revealed a significant negative correlation between washing symptom dimension score and gray matter volume in the right thalamus and a significant negative correlation between hoarding symptom dimension score and white matter volume in the left angular gyrus. Although our result was preliminary, our findings indicated that there were specific brain regions in gray and white matter that contributed to symptom dimensions in OCD patients.     

Parietal white matter abnormalities in obsessive-compulsive disorder: a magnetic resonance spectroscopy study at 3-Tesla

OBJECTIVE: To identify a neurochemical basis for the hypothesis that an aberrant cortico-subcortical circuit underlies obsessive-compulsive disorder (OCD). The white matter was also investigated because of recent research which suggests the altered connectivity of axons. METHOD: Using 3-Tesla magnetic resonance spectroscopy, the relative concentrations of N-acetylaspartate (NAA) and choline-containing compounds (Cho) to creatine/phosphocreatine (Cr) were measured in the anterior cingulate, basal ganglia, thalamus, frontal and parietal white matter of 12 OCD patients, and 32 control subjects. RESULTS: The mean concentration of Cho/Cr was significantly higher in the patients than in the controls, but only in the parietal white matter, while no significant group differences in NAA/Cr were observed in any of the brain regions. Parietal Cho/Cr correlated positively with the severity of OCD symptoms. CONCLUSION: This finding provides indirect evidence for the parietal white matter involvement in OCD, thus suggesting a change in the phospholipids of myelinated axons and/or glia cells.