Abnormalities of white matter microstructure in unmedicated patients with obsessive-compulsive disorder: Changes after cognitive behavioral therapy

Advances in DTI studies for diagnoses and treatment of obsessive-compulsive disorder

This review summarizes the current state of neuroimaging research on obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI), which allows for the examination of white matter abnormalities in the brain. DTI studies on individuals with obsessive-compulsive disorder (OCD) consistently demonstrate widespread reductions in white matter integrity in various regions of the brain, including the corpus callosum, anterior and posterior cingulate cortex, and prefrontal cortex, which are involved in emotion regulation, decision-making, and cognitive control. However, the reviewed studies often have small sample sizes, and findings vary between studies, highlighting the need for larger and more standardized studies. Furthermore, discerning between causal and consequential effects of OCD on white matter integrity poses a challenge. Addressing this issue may be facilitated through longitudinal studies, including those evaluating the impact of treatment interventions, to enhance the accuracy of DTI data acquisition and processing, thereby improving the validity and comparability of study outcomes. In summary, DTI studies provide valuable insights into the neural circuits and connectivity disruptions in OCD, and future studies may benefit from standardized data analysis and larger sample sizes to determine whether structural abnormalities could be potential biomarkers for early identification and treatment of OCD.

Cerebellar Microstructural Abnormalities in Obsessive-Compulsive Disorder (OCD): a Systematic Review of Diffusion Tensor Imaging Studies

Previous neuroimaging studies have suggested that obsessive-compulsive disorder (OCD) is associated with altered resting-state functional connectivity of the cerebellum. In this study, we aimed to describe the most significant and reproducible microstructural abnormalities and cerebellar changes associated with obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI) investigations. PubMed and EMBASE were searched for relevant studies using the PRISMA 2020 protocol. A total of 17 publications were chosen for data synthesis after screening titles and abstracts, full-text examination, and executing the inclusion criteria. The patterns of cerebellar white matter (WM) integrity loss, determined by fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) metrics, varied across studies and symptoms. Changes in fractional anisotropy (FA) values were described in six publications, which were decreased in four and increased in two studies. An increase in diffusivity parameters of the cerebellum (i.e., MD, RD, and AD) in OCD patients was reported in four studies. Alterations of the cerebellar connectivity with other brain areas were also detected in three studies. Heterogenous results were found in studies that investigated cerebellar microstructural abnormalities in correlation with symptom dimension or severity. OCD's complex phenomenology may be characterized by changes in cerebellar WM connectivity across wide networks, as shown by DTI studies on OCD patients in both children and adults. Classification features in machine learning and clinical tools for diagnosing OCD and determining the prognosis of the disorder might both benefit from using cerebellar DTI data.

Tract-based analyses of white matter in schizophrenia, bipolar disorder, aging, and dementia using high spatial and directional resolution diffusion imaging: a pilot study

Introduction

Structural brain connectivity abnormalities have been associated with several psychiatric disorders. Schizophrenia (SCZ) is a chronic disabling disorder associated with accelerated aging and increased risk of dementia, though brain findings in the disorder have rarely been directly compared to those that occur with aging.

Methods

We used an automated approach to reconstruct key white matter tracts and assessed tract integrity in five participant groups. We acquired one-hour-long high-directional diffusion MRI data from young control (CON, n =28), bipolar disorder (BPD, n =21), and SCZ (n =22) participants aged 18-30, and healthy elderly (ELD, n =15) and dementia (DEM, n =9) participants. Volume, fractional (FA), radial diffusivity (RD) and axial diffusivity (AD) of seven key white matter tracts (anterior thalamic radiation, ATR; dorsal and ventral cingulum bundle, CBD and CBV; corticospinal tract, CST; and the three superior longitudinal fasciculi: SLF-1, SLF-2 and SLF-3) were analyzed with TRACULA. Group comparisons in tract metrics were performed using multivariate and univariate analyses. Clinical relationships of tract metrics with recent and chronic symptoms were assessed in SCZ and BPD participants.

Results

A MANOVA showed group differences in FA (λ=0.5; p=0.0002) and RD (λ=0.35; p<0.0001) across the seven tracts, but no significant differences in tract AD and volume. Post-hoc analyses indicated lower tract FA and higher RD in ELD and DEM groups compared to CON, BPD and SCZ groups. Lower FA and higher RD in SCZ compared to CON did not meet statistical significance. In SCZ participants, a significant negative correlation was found between chronic psychosis severity and FA in the SLF-1 (r= -0.45; p=0.035), SLF-2 (r= -0.49; p=0.02) and SLF-3 (r= -0.44; p=0.042).

Discussion

Our results indicate impaired white matter tract integrity in elderly populations consistent with myelin damage. Impaired tract integrity in SCZ is most prominent in patients with advanced illness.

Insight in obsessive-compulsive disorder: conception, clinical characteristics, neuroimaging, and treatment

Obsessive-compulsive disorder (OCD) is a chronic disabling disease with often unsatisfactory therapeutic outcomes. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) has broadened the diagnostic criteria for OCD, acknowledging that some OCD patients may lack insight into their symptoms. Previous studies have demonstrated that insight can impact therapeutic efficacy and prognosis, underscoring its importance in the treatment of mental disorders, including OCD. In recent years, there has been a growing interest in understanding the influence of insight on mental disorders, leading to advancements in related research. However, to the best of our knowledge, there is dearth of comprehensive reviews on the topic of insight in OCD. In this review article, we aim to fill this gap by providing a concise overview of the concept of insight and its multifaceted role in clinical characteristics, neuroimaging mechanisms, and treatment for OCD.

The role of brain white matter in depression resilience and response to sleep interventions

Insomnia poses a high risk for depression. Brain mechanisms of sleep and mood improvement following cognitive behavioural therapy for insomnia remain elusive. This longitudinal study evaluated whether (i) individual differences in baseline brain white matter microstructure predict improvements and (ii) intervention affects brain white matter microstructure. People meeting the Diagnostic and Statistical Manual of Mental Disorders-5 criteria for Insomnia Disorder (n = 117) participated in a randomized controlled trial comparing 6 weeks of no treatment with therapist-guided digital cognitive behavioural therapy for insomnia, circadian rhythm support or their combination (cognitive behavioural therapy for insomnia + circadian rhythm support). Insomnia Severity Index and Inventory of Depressive Symptomatology-Self Report were assessed at baseline and followed up at Weeks 7, 26, 39 and 52. Diffusion-weighted magnetic resonance images were acquired at baseline and Week 7. Skeletonized white matter tracts, fractional anisotropy and mean diffusivity were quantified both tract-wise and voxel-wise using tract-based spatial statistics. Analyses used linear and mixed effect models while correcting for multiple testing using false discovery rate and Bonferroni for correlated endpoint measures. Our results show the following: (i) tract-wise lower fractional anisotropy in the left retrolenticular part of the internal capsule at baseline predicted both worse progression of depressive symptoms in untreated participants and more improvement in treated participants (fractional anisotropy × any intervention, PFDR = 0.053, Pcorr = 0.045). (ii) Only the cognitive behavioural therapy for insomnia + circadian rhythm support intervention induced a trend-level mean diffusivity decrease in the right superior corona radiata (PFDR = 0.128, Pcorr = 0.108), and individuals with a stronger mean diffusivity decrease showed a stronger alleviation of insomnia (R = 0.20, P = 0.035). In summary, individual differences in risk and treatment-supported resilience of depression involve white matter microstructure. Future studies could target the role of the left retrolenticular part of the internal capsule and right superior corona radiata and the brain areas they connect.

Psychotherapies and digital interventions for OCD in adults: What do we know, what do we need still to explore?

BACKGROUND

Despite significant advances in the understanding and treatment of obsessive compulsive disorder (OCD), current treatment options are limited in terms of efficacy for symptom remission. Thus, assessing the potential role of iterative or alternate psychotherapies is important. Also, the potential role of digital technologies to enhance the accessibility of these therapies, should not be underestimated. We also need to embrace the idea of a more personalized treatment choice, being cognisant of clinical, genetic and neuroimaging predictors of treatment response.

PROCEDURES

Non-systematic review of current literature on emerging psychological and digital therapies for OCD, as well as of potential biomarkers of treatment response.

FINDINGS

A number of 'third wave' therapies (e.g., Acceptance and Commitment Therapy, Mindfulness-Based Cognitive Therapy) have an emerging and encouraging evidence base in OCD. Other approaches entail employment of elements of other psychotherapies such as Dialectical Behaviour Therapy; or trauma-focussed therapies such as Eye Movement Desensitisation and Reprocessing, and Imagery Rescripting and Narrative Therapy. Further strategies include Danger Ideation Reduction Therapy and Habit Reversal. For these latter approaches, large-scale randomised controlled trials are largely lacking, and the precise role of these therapies in treating people with OCD, remains to be clarified. A concentrated 4-day program (the Bergen program) has shown promising short- and long-term results. Exercise, music, and art therapy have not been adequately tested in people with OCD, but may have an adjunctive role. Digital technologies are being actively investigated for enhancing reach and efficacy of psychological therapies for OCD. Biomarkers, including genetic and neuroimaging, are starting to point to a future with more 'personalised medicine informed' treatment strategizing for OCD.

CONCLUSIONS

There are a number of potential psychological options for the treatment of people with OCD who do not respond adequately to exposure/response prevention or cognitive behaviour therapy. Adjunctive exercise, music, and art therapy might be useful, albeit the evidence base for these is very small. Consideration should be given to different ways of delivering such interventions, including group-based, concentrated, inpatient, or with outreach, where appropriate. Digital technologies are an emerging field with a number of potential applications for aiding the treatment of OCD. Biomarkers for treatment response determination have much potential capacity and deserve further empirical testing.

White matter microstructural abnormalities and gray matter volume alterations in obsessive-compulsive disorder: A coordinate-based meta-analysis

OBJECTIVE

A comprehensive meta-analysis using correlated coordinate data to explore abnormalities in white matter (WM) microarchitecture and changes in gray matter volume (GMV) in patients with obsessive-compulsive disorder (OCD).

METHODS

We reviewed 23 reported studies of diffusion tensor imaging (DTI) in OCD patients. The differences in WM fractional anisotropy (FA) between OCD patients and healthy controls (HCs) were investigated using tract-based spatial statistics (TBSS) and voxel-based analysis (VBA), respectively, and the results of the two methods were compared. In addition, we will explore changes in OCD GMV by analyzing studies (n = 21) using the voxel-based morphometry (VBM) approach and comparing the difference between adults and adolescents.

RESULTS

In the pooled meta-analysis, WM study results presented that compared with HCs, OCD patients had higher FA in right lenticular nucleus (putamen), and lower FA in corpus callosum (CC), left insula, right cerebellum (hemispheric lobule), right gyrus rectal and left inferior parietal gyri. However, in subgroup analysis, there was a significant difference in FA changes between TBSS and VBA in OCD patients compared with HCs. In addition, we found that the GMV of OCD patients was significantly increased in left striatum and left precentral gyrus, and significantly decreased in right inferior frontal gyrus triangular part, right superior temporal gyrus and right hippocampus. Compared with adolescents, adult patients have increased GMV in left lenticular nucleus putamen.

CONCLUSION

The meta-analysis showed that OCD patients had abnormal WM microarchitecture and altered GMV. These changes may be closely related to the pathophysiological mechanism of the disease.

Neurobiological outcomes of cognitive behavioral therapy for obsessive-compulsive disorder: A systematic review

Introduction

Obsessive-compulsive disorder (OCD) is characterized by recurrent distressing thoughts and repetitive behaviors, or mental rituals performed to reduce anxiety. Recent neurobiological techniques have been particularly convincing in suggesting that cortico-striatal-thalamic-cortico (CSTC) circuits, including orbitofrontal cortex (OFC) and striatum regions (caudate nucleus and putamen), are responsible for mediation of OCD symptoms. However, it is still unclear how these regions are affected by OCD treatments in adult patients. To address this yet open question, we conducted a systematic review of all studies examining neurobiological changes before and after first-line psychological OCD treatment, i.e., cognitive-behavioral therapy (CBT).

Methods

Studies were included if they were conducted in adults with OCD and they assessed the neurobiological effects of CBT before and after treatment. Two databases were searched: PsycINFO and PubMed for the time frame up to May 2022.

Results

We obtained 26 pre-post CBT treatment studies performed using different neurobiological techniques, namely functional magnetic resonance imaging (fMRI), Positron emission tomography (PET), regional cerebral blood flow (rCBF), 5-HT concentration, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), Electroencephalography (EEG). Neurobiological data show the following after CBT intervention: (i) reduced activations in OFC across fMRI, EEG, and rCBF; (ii) decreased activity in striatum regions across fMRI, rCBF, PET, and MRI; (iii) increased activations in cerebellum (CER) across fMRI and MRI; (iv) enhanced neurochemical concentrations in MRS studies in OFC, anterior cingulate cortex (ACC) and striatum regions. Most of these neurobiological changes are also accompanied by an improvement in symptom severity as assessed by a reduction in the Y-BOCS scores.

Conclusion

Cognitive-behavioral therapy seems to be able to restructure, modify, and transform the neurobiological component of OCD, in addition to the clinical symptoms. Nevertheless, further studies are necessary to frame the OCD spectrum in a dimensional way.

Changes in the geometry and robustness of diffusion tensor imaging networks: Secondary analysis from a randomized controlled trial of young autistic children receiving an umbilical cord blood infusion

Diffusion tensor imaging (DTI) has been used as an outcome measure in clinical trials for several psychiatric disorders but has rarely been explored in autism clinical trials. This is despite a large body of research suggesting altered white matter structure in autistic individuals. The current study is a secondary analysis of changes in white matter connectivity from a double-blind placebo-control trial of a single intravenous cord blood infusion in 2-7-year-old autistic children (1). Both clinical assessments and DTI were collected at baseline and 6 months after infusion. This study used two measures of white matter connectivity: change in node-to-node connectivity as measured through DTI streamlines and a novel measure of feedback network connectivity, Ollivier-Ricci curvature (ORC). ORC is a network measure which considers both local and global connectivity to assess the robustness of any given pathway. Using both the streamline and ORC analyses, we found reorganization of white matter pathways in predominantly frontal and temporal brain networks in autistic children who received umbilical cord blood treatment versus those who received a placebo. By looking at changes in network robustness, this study examined not only the direct, physical changes in connectivity, but changes with respect to the whole brain network. Together, these results suggest the use of DTI and ORC should be further explored as a potential biomarker in future autism clinical trials. These results, however, should not be interpreted as evidence for the efficacy of cord blood for improving clinical outcomes in autism. This paper presents a secondary analysis using data from a clinical trial that was prospectively registered with ClinicalTrials.gov(NCT02847182).

Unhealthy mind in a healthy body: A criticism to eliminativism in psychopathology

In this article we criticize the thesis "The diseases we treat are diseases of the brain". A first criticism is against the eliminativist perspective and in favor of a perspective that is still reductionist but emergentist and functionalist. In a second part, we try to answer the question "under which conditions can we consider this statement legitimate?". We argue that only those mental disorders whose neural substrate has clearly neuropathological characteristics, i.e., anomalies with respect to the laws of good neural functioning, can be considered "brain diseases." We propose that it is not sufficient to observe a simple difference between the brains of people with psychopathology, that is, with anomalies with respect to the laws of good psychological functioning, and that of people without psychopathology. Indeed, we believe it is a categorical error to postulate a neuropathology starting from a psychopathology. Finally, we summarize some research that shows how purely psychological interventions can reduce or eliminate the differences between the brains of people with or psychopathology and those of people without.

Multi-modality connectome-based predictive modeling of individualized compulsions in obsessive-compulsive disorder

BACKGROUND

While previous neuroimaging studies are mainly focused on dichotomous classification of obsessive-compulsive disorder (OCD) from controls, predicting continuous severity of specific symptom is also pivotal to clinical diagnosis and treatment.

METHODS

We applied a machine-learning approach, connectome-based predictive modeling, on functional and structural brain networks constructed from resting-state functional magnetic resonance imaging and diffusion tensor imaging data to decode compulsions and obsessions of fifty-four patients with OCD.

RESULTS

We successfully predicted individualized compulsions with a positive model of structural brain network and with a negative model of functional brain network. The structural predictive brain network comprises the motor cortex, cerebellum and limbic lobe, which are involved in basic motor control, motor execution and emotion processing, respectively. The functional predictive brain network is composed by the prefrontal and limbic systems which are related to cognitive and affective control. Computational lesion analysis shows that functional connectivity among the salience network (SN), the frontal parietal network and the default mode network, as well as structural connectivity within the SN are vital in the individualized prediction of compulsions in OCD.

LIMITATIONS

There was no external validation of large samples to test the robustness of our predictive model.

CONCLUSIONS

These findings provide the first evidence for the predictive role of the triple network model in individualized compulsions and have important implications in diagnosis, prognosis and treatment of patients with OCD.

Transdiagnostic role of glutamate and white matter damage in neuropsychiatric disorders: A Systematic Review

Neuropsychiatric disorders including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology. We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities in these disorders from a transdiagnostic perspective. The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 401 studies were included. The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus displayed decreased FA in all disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients. The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

A study on diffusion tensor imaging in patients with untreated first-episode obsessive-compulsive disorder

OBJECTIVE

The present study provides an overview of studies investigating white matter (WM) integrity in patients with obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI). Furthermore, it studies the correlation of fractional anisotropy (FA) in abnormal cerebral WM areas with the course and clinical signs of the disease.

METHODS

The study subjects were divided into two groups, the OCD group (n=38) and the control group (n=40), based on the Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5) diagnostic criteria for OCD. Patients with untreated first-episode OCD were assigned to the OCD group, while healthy volunteers were assigned to the control group. The study group was evaluated in accordance with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), Self-Rating Depression Scale (SDS) and Self-Rating Anxiety Scale (SAS). Subjects who met the inclusion criteria underwent whole-brain scanning via 3.0 T structural magnetic resonance imaging (sMRI). The WM FA values in different brain areas were compared between the two groups using voxel-based analysis (VBA). Subsequently, the correlations of the patient Y-BOCS score and disorder course with the FA values in significantly improved encephalic areas were analyzed.

RESULTS

(I) The FA values of the right precentral gyrus (PreCG.R), left insular lobe, left inferior frontal gyrus and right inferior occipital gyrus (Occipital_Inf_R) WM were significantly lower in the OCD group than in the control group (P<0.05). Elevated FA values were not observed in the OCD group. (II) FA values of PreCG.R, left insular lobe/left inferior frontal gyrus, and Occipital_Inf_R were not found in relation to the total Y-BOCS score (P=0.122; P=0.401; P=0.134), obsessional thoughts score (P=0.299; P=0.760; P=0.062), compulsive activities checklist (P=0.487; P=0.420; P=0.431), and disease course (P=0.604; P=0.380; P=0.182).

CONCLUSIONS

Multiple microstructural cerebral WM changes were observed in the frontal lobe, occipital lobe, and insula in patients with untreated first-episode OCD, presenting the correlation of these changes with OCD occurrence.

The Cerebellum in Drug-naive Children with Tourette Syndrome and Obsessive–Compulsive Disorder

Tourette syndrome (TS) and obsessive–compulsive disorder (OCD) are two neurodevelopmental disorders characterized by repetitive behaviors. Our recent study in drug-naive children with TS and OCD provided evidence of cerebellar involvement in both disorders. In addition, cerebellar functional connectivity (FC) was similar in TS patients without comorbidities (TSpure) and TS patients with OCD comorbidity (TS + OCD), but differed in pure OCD patients. To investigate in detail the cerebellar involvement in the pathophysiology of TS and OCD, we explored cerebellar structural and functional abnormalities in drug-naive children with TSpure, TS + OCD, and OCD and assessed possible correlations with severity scores. We examined 53 drug-naive children, classified as TSpure (n = 16), TS + OCD (n = 14), OCD (n = 11), or controls (n = 12). All subjects underwent a multimodal 3T magnetic resonance imaging examination. Cerebellar lobular volumes and quantitative diffusion tensor imaging parameters of cerebellar peduncles were used as measures of structural integrity. The dentate nucleus was selected as a region of interest to examine cerebello-cerebral functional connectivity alterations. Structural analysis revealed that both TSpure and TS + OCD patients had higher fractional anisotropy in cerebellar peduncles than controls. Conversely, OCD patients were characterized by lower fractional anisotropy than both controls and TSpure and TS + OCD patients. Lastly, cerebellar functional connectivity analysis revealed significant alterations in the cerebello-thalamo-cortical circuit in TSpure, TS + OCD, and OCD patients. Early cerebellar structural and functional changes in drug-naive pediatric TSpure, TS + OCD, and OCD patients support a primary role of the cerebellum in the pathophysiology of these disorders.

Using Electronically Delivered Therapy and Brain Imaging to Understand OCD Pathophysiology: Pilot Protocol

BACKGROUND

Obsessive-compulsive disorder (OCD) is a debilitating and prevalent anxiety disorder. While the basal ganglia and frontal cortex are the most hypothesized brain regions involved, the exact pathophysiology is unknown. By observing the effects of proven treatments on brain activation levels, the cause of OCD can be better understood. Currently, the gold standard treatment for OCD is cognitive behavioural therapy (CBT) with exposure and response prevention (ERP). However, this is often temporally and geographically inaccessible, time-consuming, and costly. Fortunately, CBT can be effectively delivered using the internet (e-CBT) due to its structured nature thus addressing these barriers.

OBJECTIVE

This study will implement an e-CBT program for OCD and observe its effects on brain activation levels using functional magnetic resonance imaging (fMRI). It is hypothesized that brain activation levels in the basal ganglia and frontal cortex will decrease following treatment.

METHODS

Individuals with OCD will be offered a 16-week e-CBT program with ERP mirroring in-person CBT content that will be administered through a secure online platform. Efficacy of treatment will be evaluated using clinically validated symptomology questionnaires at baseline, week 8, and post-treatment (week 16). Using fMRI at baseline and post-treatment, brain activation levels will be assessed at resting state, and while exposed to anxiety-inducing images (i.e., dirty dishes if cleanliness is an obsession). The effects of treatment on brain activation levels and the correlation between symptom changes and activation levels will be analyzed.

RESULTS

The study received initial ethics approval in December 2020 and participant recruitment began in January 2021. Participant recruitment has been conducted through social media advertisements, physical advertisements, and physician referrals. To date, there have been 5 participants recruited. Data collection is expected to conclude by January 2022, and data analysis is expected to be completed by February 2022.

CONCLUSIONS

The findings from this study can further our understanding of the causation of OCD, helping to develop more effective treatments for this disorder.

CLINICALTRIAL

ClinicalTrials.gov NCT04630197; clinicaltrials.gov/ct2/show/NCT04630197.

Disrupted pathways from frontal-parietal cortex to basal ganglia and cerebellum in patients with unmedicated obsessive compulsive disorder as observed by whole-brain resting-state effective connectivity analysis - a small sample pilot study

OBJECTIVE

To date, a systematic characterization of abnormalities in resting-state effective connectivity (rsEC) in obsessive-compulsive disorder (OCD) is lacking. The present study aimed to systematically characterize whole-brain rsEC in OCD patients as compared to healthy controls.

METHODS

Using resting-state fMRI data of 50 unmedicated patients with OCD and 50 healthy participants, we constructed whole-brain rsEC networks using Granger causality analysis followed by univariate and multivariate comparisons between patients and controls. Similar analyses were performed for resting-state functional connectivity (rsFC) networks to examine how rsFC and rsEC differentially capture abnormal brain connectivity in OCD.

RESULTS

Univariate comparisons identified 10 rsEC networks that were significantly disrupted in patients, and which were mainly associated with frontal-parietal cortex, basal ganglia, and cerebellum. Conversely, abnormal rsFC networks were widely distributed throughout the whole brain. Multivariate pattern analysis revealed a classification accuracy as high as 80.5% for distinguishing patients from controls using combined whole-brain rsEC and rsFC.

CONCLUSIONS

The results of the present study suggest disrupted communication of information from frontal-parietal cortex to basal ganglia and cerebellum in OCD patients. Using combined whole-brain rsEC and rsFC, multivariate pattern analysis revealed a classification accuracy as high as 80.5% for distinguishing patients from controls. The alterations observed in OCD patients could aid in identifying treatment mechanisms for OCD.

Defining functional brain networks underlying obsessive-compulsive disorder (OCD) using treatment-induced neuroimaging changes: a systematic review of the literature

Approximately 2%-3% of the population suffers from obsessive-compulsive disorder (OCD). Several brain regions have been implicated in the pathophysiology of OCD, but their various contributions remain unclear. We examined changes in structural and functional neuroimaging before and after a variety of therapeutic interventions as an index into identifying the underlying networks involved. We identified 64 studies from 1990 to 2020 comparing pretreatment and post-treatment imaging of patients with OCD, including metabolic and perfusion, neurochemical, structural, functional and connectivity-based modalities. Treatment class included pharmacotherapy, cognitive-behavioural therapy/exposure and response prevention, stereotactic lesions, deep brain stimulation and transcranial magnetic stimulation. Changes in several brain regions are consistent and correspond with treatment response despite the heterogeneity in treatments and neuroimaging modalities. Most notable are decreases in metabolism and perfusion of the caudate, anterior cingulate cortex, thalamus and regions of prefrontal cortex (PFC) including the orbitofrontal cortex (OFC), dorsolateral PFC (DLPFC), ventromedial PFC (VMPFC) and ventrolateral PFC (VLPFC). Modulating activity within regions of the cortico-striato-thalamo-cortical system may be a common therapeutic mechanism across treatments. We identify future needs and current knowledge gaps that can be mitigated by implementing integrative methods. Future studies should incorporate a systematic, analytical approach to testing objective correlates of treatment response to better understand neurophysiological mechanisms of dysfunction.

Diffusion Tensor Imaging Before and 3 Months After Concentrated Exposure Response Prevention in Obsessive-Compulsive Disorder

Background: Subtle differences in white matter microstructure have been found in obsessive-compulsive disorder (OCD) compared to controls using diffusion tensor imaging (DTI), but it is unclear if and how this change after treatment. The primary aim of this pre-registered study was to investigate white matter integrity between OCD patients and controls and changes after concentrated exposure and response prevention (ERP). Methods: Fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD) and mean diffusivity (MD) were estimated using FMRIB Software Library (FSL). The images were registered to a study-specific template using a longitudinal pipeline based on full tensor information in DTI-TK. Voxel-based analysis was performed using tract-based spatial statistics (TBSS). Using SPSS, we compared the integrity in three bilateral regions of interest (ROI), the sagittal stratum, posterior thalamic radiation and cingulum, in 32 OCD patients and 30 matched healthy controls at baseline. Patients received a four-day concentrated ERP format. We investigated longitudinal changes in 26 OCD patients and 22 healthy controls at 3months follow-up using repeated-measures ANOVA. Exploratory t-tests were conducted for AD and MD. Secondary hypothesis used linear regression to investigate if baseline FA predict treatment outcome 3 months later, and if patients with illness onset before 18 years of age would show lower FA in sagittal stratum. Finally, we performed sensitivity analysis on medication and comorbidity influences on FA. Results: Three months after treatment, 77% of the patients were in remission. Contrary to our hypotheses, we did not find any significant differences in FA, RD, AD or MD between the groups before treatment, nor significant group by time effects in any of the ROI. None of the baseline FA measures significantly predicted treatment outcome. Illness onset before 18 years of age did not significantly predict FA in the sagittal stratum. Adjusting for medication or comorbid anxiety or mood disorder did not influence the results. Conclusions: Although concentrated ERP in OCD lead to high remission, we did not find significant long-term changes by DTI. Future studies will benefit from using larger sample sizes and multi-shell diffusion-weighted imaging when investigating white matter microstructure in OCD and underlying neurobiological mechanisms of treatment.

Consistent altered internal capsule white matter microstructure in insomnia disorder

STUDY OBJECTIVES

Suggested neural correlates of insomnia disorder have been hard to replicate. Even the most consistent finding, altered white matter microstructure in the anterior limb of the internal capsule, is based on handful studies. The urge for replicable targets to understand the underlying mechanisms of insomnia made us study white matter fractional anisotropy (FA) across three samples of cases and controls.

METHODS

3-Tesla MRI diffusion tensor imaging data of three independent samples were combined for analysis, resulting in n = 137 participants, of whom 73 were diagnosed with insomnia disorder and 64 were matched controls without sleep complaints. Insomnia severity was measured with the Insomnia Severity Index (ISI). White matter microstructure was assessed with FA. White matter tracts were skeletonized and analyzed using tract-based spatial statistics. We performed a region-of-interest analysis using linear mixed-effect models to evaluate case-control differences in internal capsule FA as well as associations between internal capsule FA and insomnia severity.

RESULTS

FA in the right limb of the anterior internal capsule was lower in insomnia disorder than in controls (β = -9.76e-3; SE = 4.17e-3, p = .034). In the entire sample, a higher ISI score was associated with a lower FA value of the right internal capsule (β = -8.05e- 4 FA/ISI point, SE = 2.60e- 4, p = .008). Ancillary whole brain voxel-wise analyses showed no significant group difference or association with insomnia severity after correction for multiple comparisons.

CONCLUSIONS

The internal capsule shows small but consistent insomnia-related alterations. The findings support a circuit-based approach to underlying mechanisms since this tract connects many brain areas previously implicated in insomnia.

White matter microstructural and Compulsive Sexual Behaviors Disorder - Diffusion Tensor Imaging study

BACKGROUND AND AIMS

Even though the Compulsive Sexual Behavior Disorder (CSBD) was added to the ICD-11 under the impulse control category in 2019, its neural mechanisms are still debated. Researchers have noted its similarity both to addiction and to Obssesive-Compulsive Disorder (OCD). The aim of our study was to address this question by investigating the pattern of anatomical brain abnormalities among CSBD patients.

METHODS

Reviewing 39 publications on Diffusion Tensor Imaging (DTI) we have identified main abnormalities specific for addictions and OCD. Than we have collected DTI data from 36 heterosexual males diagnosed with CSBD and 31 matched healthy controls. These results were then compared to the addiction and OCD patterns.

RESULTS

Compared to controls, CSBD individuals showed significant fractional anisotropy (FA) reduction in the superior corona radiata tract, the internal capsule tract, cerebellar tracts and occipital gyrus white matter. Interestingly, all these regions were also identified in previous studies as shared DTI correlates in both OCD and addiction.

DISCUSSION AND CONCLUSIONS

Results of our study suggest that CSBD shares similar pattern of abnormalities with both OCD and addiction. As one of the first DTI study comparing structural brain differences between CSBD, addictions and OCD, although it reveals new aspects of CSBD, it is insufficient to determine whether CSBD resembles more an addiction or OCD. Further research, especially comparing directly individuals with all three disorders may provide more conclusive results.

The effects of cognitive behavioral therapy on the whole brain structural connectome in unmedicated patients with obsessive-compulsive disorder

Cognitive behavioral therapy (CBT) is considered a first-line treatment for patients with obsessive-compulsive disorder (OCD), and it possesses advantages over pharmacological treatments in stronger tolerance to distress, lower rates of drop out and relapse, and no physical "side-effects". Previous studies have reported CBT-related alterations in focal brain regions and connections. However, the effects of CBT on whole-brain structural networks have not yet been elucidated. Here, we collected diffusion MRI data from 34 unmedicated OCD patients before and after 12 weeks of CBT. Fifty healthy controls (HCs) were also scanned twice at matched intervals. We constructed individual brain white matter connectome and performed a graph-theoretical network analysis to investigate the effects of CBT on whole-brain structural topology. We observed significant group-by-time interactions on the global network clustering coefficient and the nodal clustering of the left lingual gyrus, the left middle temporal gyrus, the left precuneus, and the left fusiform gyrus of 26 CBT responders in OCD patients. Further analysis revealed that these CBT responders showed prominently higher global and nodal clustering compared to HCs at baseline and reduced to normal levels after CBT. Such significant changes in the nodal clustering of the left lingual gyrus were also found in 8 CBT non-responders. The pre-to-post decreases in nodal clustering of the left lingual gyrus and the left fusiform gyrus positively correlated with the improvements in obsessive-compulsive symptoms in the CBT-responding patients. These findings indicated that the network segregation of the whole-brain white matter network in OCD patients was abnormally higher and might recover to normal after CBT, which provides mechanistic insights into the CBT response in OCD and potential imaging biomarkers for clinical practice.

Microstructural white matter abnormalities in obsessive-compulsive disorder: A coordinate-based meta-analysis of diffusion tensor imaging studies

BACKGROUND

There are no conclusive diffusion tensor imaging (DTI) findings on obsessive-compulsive disorder (OCD) for now. We conducted a comprehensive meta-analysis of DTI studies to identify white matter (WM) microarchitecture changes in OCD, and also to compare the results differences between the two most frequently used methods (voxel-based analysis, VBA versus tract-based spatial statistics, TBSS) for DTI data.

METHODS

A systematic search was performed on relevant studies that reported fractional anisotropy (FA) alterations between patients with OCD and healthy controls (HC). Seed-based d mapping (SDM) was applied to analyze microstructural WM abnormalities in OCD patients. Subgroup meta-analysis was subsequently performed to explore methodological differences between VBA and TBSS approaches.

RESULTS

A total of 30 studies (with 31 datasets) that comprised 855 patients and 875 HC were identified. OCD patients exhibited significantly decreased FA in the right cerebellar hemispheric lobule, corpus callosum (CC), left superior frontal gyrus (orbital part), right gyrus rectus, left superior longitudinal fasciculus and right lenticular nucleus in the pooled meta-analysis. The VBA subgroup showed lower FA in several brain regions while the TBSS subgroup only exhibited significant FA reductions in the CC.

CONCLUSION

According to the pooled meta-analysis, OCD patients presented microstructural abnormalities in distributed WM tracts. However, heterogeneous results were found between VBA and TBSS studies.

Increased cerebellar-default-mode network connectivity at rest in obsessive-compulsive disorder

Abnormalities of the cerebellum and default-mode network (DMN) in patients with obsessive-compulsive disorder (OCD) have been widely reported. However, alterations of reciprocal functional connections between the cerebellum and DMN at rest in OCD remain unclear. Forty patients with OCD and 38 gender-, age-, and education-matched healthy controls (HCs) underwent resting-state functional magnetic resonance imaging scan. Seed-based functional connectivity (FC) and support vector machine (SVM) were applied to analyze the imaging data. Compared with HCs, patients with OCD exhibited increased FCs between the left Crus I-left superior medial prefrontal cortex (MPFC) and between the right Crus I-left superior MPFC, left middle MPFC, and left middle temporal gyrus (MTG). A significantly negative correlation was observed between the right Crus I-left MTG connectivity and the Yale-Brown Obsessive-Compulsive Scale compulsion subscale scores in the OCD group (r = - 0.476, p = 0.002, Bonferroni corrected). SVM classification analysis indicated that a combination of the left Crus I-left superior MPFC connectivity and the right Crus I-left middle MPFC connectivity can be used to discriminate patients with OCD from HCs with a sensitivity of 85.00%, specificity of 68.42%, and accuracy of 76.92%. Our study highlights the contribution of the cerebellar-DMN connectivity in OCD pathophysiology and provides new findings to OCD research.

A voxel-based analysis of cerebral blood flow abnormalities in obsessive-compulsive disorder using pseudo-continuous arterial spin labeling MRI

Objective

To identify abnormalities of regional cerebral blood flow (rCBF) in individuals with obsessive-compulsive disorder (OCD) by conducting a voxel-based analysis of pseudo-continuous arterial spin labeling (pCASL) perfusion images.

Materials and methods

This prospective study included 23 OCD patients (nine males, 14 females; age 21–62 years; mean ± SD 37.2 ± 10.7 years) diagnosed based on DSM-IV-TR criteria and 64 healthy controls (27 males, 37 females; age 20–64 years; mean ± SD 38.3 ± 12.8 years). Subjects were recruited from October 2011 to August 2017. Imaging was performed on a 3T scanner. Quantitative rCBF maps generated from pCASL images were co-registered and resliced with the three-dimensional T1-weighted images, and then spatially normalized to a brain template and smoothed. We used statistical nonparametric mapping to assess the differences in rCBF and gray matter volume between the OCD and control groups. The significance level was set at the p-value <0.05 with family-wise error rate correction for multiple comparisons.

Results

Compared to the control group, there were significant rCBF reductions in the right putamen, right frontal operculum, left midcingulate cortex, and right temporal pole in the OCD group. There were no significant between-group differences in the gray matter volume.

Conclusion

The pCASL imaging noninvasively detected physiologically disrupted areas without structural abnormalities in OCD patients. The rCBF reductions observed in these regions in OCD patients could be associated with the pathophysiology of OCD.

Abnormalities of white matter microstructure in unmedicated patients with obsessive-compulsive disorder: Changes after cognitive behavioral therapy

BACKGROUND

Cognitive behavioral therapy (CBT) is an effective treatment for Obsessive-compulsive disorder (OCD). Structural and functional white matter defects may suggest a vital neurobiological basis of OCD. However, the effects of CBT on white matter in OCD remain unknown.

OBJECTIVE

The aim was to investigate white matter changes and the effect of CBT on white matter in OCD patients.

METHODS

Fractional anisotropy (FA) maps were acquired using DTI. Participants included 85 patients with OCD and 90 healthy controls. VBM was then performed to detect regions with significant group differences.

RESULTS

Obsessive-compulsive disorder patients exhibited significantly reduced FA values in bilateral OFC, right cerebellum, and left SPG, while higher FA values were observed in right PUT compared with healthy controls. Following CBT, OCD patients showed higher FA values in right MFG, left OFC, right cerebellum, and left MTG, and decreased FA values in right PUT in comparison with pretreatment. Furthermore, FA values in the left OFC of patients were significantly positively correlated with the Y-BOCS and its associated Compulsions subscale, and FA values in the right PUT were positively correlated with Compulsions subscale. In addition, the percentage change in FA values in left MTG was positively correlated with the percentage reduction in Compulsions subscale, while the percentage change in FA values in left OFC and right PUT was negatively correlated with the percentage reductions in Obsessive and Compulsions subscale, respectively.

CONCLUSIONS

Our findings demonstrate the abnormalities of white matter microstructure in unmedicated patients with OCD. These abnormalities may be partly reversed by CBT.