Functional neuroimaging and the neuroanatomy of obsessive-compulsive disorder

Towards zebrafish models to unravel translational insights of obsessive-compulsive disorder: A neurobehavioral perspective

Obsessive-compulsive disorder (OCD) is a chronic and debilitating illness that has been considered a polygenic and multifactorial disorder, challenging effective therapeutic interventions. Although invaluable advances have been obtained from human and rodent studies, several molecular and mechanistic aspects of OCD etiology are still obscure. Thus, the use of non-traditional animal models may foster innovative approaches in this field, aiming to elucidate the underlying mechanisms of disease from an evolutionary perspective. The zebrafish (Danio rerio) has been increasingly considered a powerful organism in translational neuroscience research, especially due to the intrinsic features of the species. Here, we outline target mechanisms of OCD for translational research, and discuss how zebrafish-based models can contribute to explore neurobehavioral aspects resembling those found in OCD. We also identify possible advantages and limitations of potential zebrafish-based models, as well as highlight future directions in both etiological and therapeutic research. Lastly, we reinforce the use of zebrafish as a promising tool to unravel the biological basis of OCD, as well as novel pharmacological therapies in the field.

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.

Repeated Δ-9-Tetrahydrocannabinol administration dose dependently increases stablished schedule-induced drinking

RATIONALE

Schedule-induced drinking (SID) reproduces an excessive and repetitive behavioural pattern that has led to propose this procedure as an animal model to study compulsive behaviours. Although it is known that cannabis can cause several adverse effects, in recent years there has been great interest in the medical application of cannabis derivatives for obsessive-compulsive related disorders.

OBJECTIVES

The present study investigated the effects of repeated THC administration on rates of previously acquired SID, as well as the possible alteration of its temporal distribution along inter-food intervals.

METHODS

Male Wistar rats acquired SID under a 30 min fixed-time 30-sec food delivery schedule (from 30 to 43 sessions to reach a stable level). Thereafter, 5 or 10 mg/kg daily i.p. injections of THC or vehicle were repeatedly administered for 7 days to evaluate the effects on SID.

RESULTS

Repeated THC administration at a dose of 5 mg/kg resulted in an increase on licking. Surprisingly, no effects on SID were observed with the 10 mg/kg dose. However, magazine entries were reduced with both THC doses. THC also modified the temporal distributions of licking and magazine entries during inter-food intervals.

CONCLUSIONS

The present results show that repeated THC administration may (i) increase induced licking at moderate doses, (ii) reduce magazine entries, and (iii) affect the temporal pattern of SID. These findings suggest that THC does not appear to be beneficial to reduce compulsive behaviour in this animal model, while another collateral effect of THC -such as a greater habitual-like behaviour- needs to be considered.

Hyperactivity of indirect pathway-projecting spiny projection neurons promotes compulsive behavior

Compulsive behaviors are a hallmark symptom of obsessive compulsive disorder (OCD). Striatal hyperactivity has been linked to compulsive behavior generation in correlative studies in humans and causal studies in rodents. However, the contribution of the two distinct striatal output populations to the generation and treatment of compulsive behavior is unknown. These populations of direct and indirect pathway-projecting spiny projection neurons (SPNs) have classically been thought to promote or suppress actions, respectively, leading to a long-held hypothesis that increased output of direct relative to indirect pathway promotes compulsive behavior. Contrary to this hypothesis, here we find that indirect pathway hyperactivity is associated with compulsive grooming in the Sapap3-knockout mouse model of OCD-relevant behavior. Furthermore, we show that suppression of indirect pathway activity using optogenetics or treatment with the first-line OCD pharmacotherapy fluoxetine is associated with reduced grooming in Sapap3-knockouts. Together, these findings highlight the striatal indirect pathway as a potential treatment target for compulsive behavior.

The role of neuroactive steroids in tic disorders

Tics are sudden, repetitive movements or vocalizations. Tic disorders, such as Tourette syndrome (TS), are contributed by the interplay of genetic risk factors and environmental variables, leading to abnormalities in the functioning of the cortico-striatal-thalamo-cortical (CSTC) circuitry. Various neurotransmitter systems, such as gamma-aminobutyric acid (GABA) and dopamine, are implicated in the pathophysiology of these disorders. Building on the evidence that tic disorders are predominant in males and exacerbated by stress, emerging research is focusing on the involvement of neuroactive steroids, including dehydroepiandrosterone sulfate (DHEAS) and allopregnanolone, in the ontogeny of tics and other phenotypes associated with TS. Emerging evidence indicates that DHEAS levels are significantly elevated in the plasma of TS-affected boys, and the clinical onset of this disorder coincides with the period of adrenarche, the developmental stage characterized by a surge in DHEAS synthesis. On the other hand, allopregnanolone has garnered particular attention for its potential to mediate the adverse effects of acute stress on the exacerbation of tic severity and frequency. Notably, both neurosteroids act as key modulators of GABA-A receptors, suggesting a pivotal role of these targets in the pathophysiology of various clinical manifestations of tic disorders. This review explores the potential mechanisms by which these and other neuroactive steroids may influence tic disorders and discusses the emerging therapeutic strategies that target neuroactive steroids for the management of tic disorders.

Associations between somatomotor-putamen resting state connectivity and obsessive-compulsive symptoms vary as a function of stress during early adolescence: Data from the ABCD study

Obsessive-compulsive symptoms (OCS) are relatively common during adolescence although most individuals do not meet diagnostic criteria for obsessive-compulsive disorder (OCD). Nonetheless, OCS during adolescence are associated with comorbid psychopathologies and behavioral problems. Heightened levels of environmental stress and greater functional connectivity between the somatomotor network and putamen have been previously associated with elevated OCS in OCD patients relative to healthy controls. However, the interaction of these factors within the same sample of individuals has been understudied. This study examined somatomotor-putamen resting state connectivity, stress, and their interaction on OCS in adolescents from 9-12 years of age. Participants (n = 6386) were drawn from the ABCD Study 4.0 release. Multilevel modeling was used to account for nesting in the data and to assess changes in OCS in this age range. Stress moderated the association between somatomotor-putamen connectivity and OCS (β = 0.35, S.E. = 0.13, p = 0.006). Participants who reported more stress than their average and had greater somatomotor-left putamen connectivity reported more OCS, whereas participants who reported less stress than their average and had greater somatomotor-left putamen connectivity reported less OCS. These data suggest that stress differentially affects the direction of association between somatomotor-putamen connectivity and OCS. Individual differences in the experience or perception of stress may contribute to more OCS in adolescents with greater somatomotor-putamen connectivity.

Association of rs11081062 polymorphism of DLGAP1 gene and levels of SLC1A1 protein with obsessive-compulsive disorder

Glutamate is an important neurotransmitter known to be effective in obsessive-compulsive disorder (OCD). The aim of this study is to investigate the relationship between the DLGAP1 gene encoding the scaffold protein of ionotropic glutamate receptors and the SLC1A1 gene encoding the glutamate transporter protein with OCD. Study groups consisted of 95 patients with OCD and 100 healthy controls. The severity of OCD in the patient group was determined by using the Y-BOCS. Single nucleotide polymorphisms of rs11081062 (C/T) in DLGAP1 and rs587777696 (C/T) in SLC1A1 were analyzed by real-time PCR. Levels of SLC1A1 protein were determined by ELISA. A significant difference was found between genotype distributions of rs11081062 in DLGAP1 in study groups (p < 0.001). No significant association was found rs587777696 in SLC1A1 in OCD patients and controls. SLC1A1 protein levels were found to be lower in OCD patients compared to controls (p = 0.005). According to OCD risk estimates for genotypes distributions of rs11081062 in DLGAP1, having CT + TT genotypes was associated with the occurrence of sexual and religious obsessions and counting compulsions (p = 0.038, OR = 2.98; p = 0.033, OR = 3.43; p = 0.035, OR = 2.66, respectively). CT genotype in DLGAP1 rs11081062 polymorphism was found to increase the risk of OCD in the female gender (p = 0.042, OR = 3.01). This study suggests that rs11081062 in DLGAP1 may be associated with OCD and that SLC1A1 protein levels may be involved in the occurrence of OCD. We believe that our research can contribute to the understanding of the importance of glutamate in OCD.

Striatal insights: a cellular and molecular perspective on repetitive behaviors in pathology

Animals often behave repetitively and predictably. These repetitive behaviors can have a component that is learned and ingrained as habits, which can be evolutionarily advantageous as they reduce cognitive load and the expenditure of attentional resources. Repetitive behaviors can also be conscious and deliberate, and may occur in the absence of habit formation, typically when they are a feature of normal development in children, or neuropsychiatric disorders. They can be considered pathological when they interfere with social relationships and daily activities. For instance, people affected by obsessive-compulsive disorder, autism spectrum disorder, Huntington's disease and Gilles de la Tourette syndrome can display a wide range of symptoms like compulsive, stereotyped and ritualistic behaviors. The striatum nucleus of the basal ganglia is proposed to act as a master regulator of these repetitive behaviors through its circuit connections with sensorimotor, associative, and limbic areas of the cortex. However, the precise mechanisms within the striatum, detailing its compartmental organization, cellular specificity, and the intricacies of its downstream connections, remain an area of active research. In this review, we summarize evidence across multiple scales, including circuit-level, cellular, and molecular dimensions, to elucidate the striatal mechanisms underpinning repetitive behaviors and offer perspectives on the implicated disorders. We consider the close relationship between behavioral output and transcriptional changes, and thereby structural and circuit alterations, including those occurring through epigenetic processes.

Neuronal correlates of intensification and acceptance of symptoms during exposure therapy in patients with obsessive-compulsive disorder

Introduction

Cognitive behaviour therapy with exposure and response prevention is efficient in treating patients with obsessive-compulsive disorder (OCD). Nevertheless, it would be helpful for many patients to complement the therapeutic treatment with acceptance strategies to further increase the therapeutic benefit. The aim of the present study was to examine neurobiological responses to acceptance and intensification strategies during symptom provocation alongside the psychotherapeutic process.

Method

A total of 23 patients diagnosed with OCD (subtype: washing/contamination fear) was instructed to utilise either an acceptance strategy (ACS) or an intensification strategy (INS) to cope with their emotional and cognitive reactions to personalised symptom-triggering and neutral pictures. Fourteen patients participated twice: at the beginning [T1] and at the end [T2] of an inpatient multimodal treatment including cognitive behaviour therapy with response prevention to assess functional variations.

Results

For the contrast of T1 and T2, ACS showed increased brain activity in the left inferior frontal gyrus (IFG), left caudate body, and posterior cingulate gyrus (PCC). They also showed decreased activity in the left anterior insula. INS showed decreased activation in right lingual gyrus and right caudate body. At T2, ACS showed increased activation compared to INS in the left cerebrum: IFG, caudate nucleus, middle and superior temporal gyrus, and PCC/cuneus. For the comparison of T1 and T2, the ACS revealed increased brain activity in the left IFG, left caudate body, and right inferior parietal lobe. It showed decreased activity in the left anterior insula. The INS revealed decreased activity in right lingual gyrus and right caudate body.The psychometric questionnaires suggested that patients were able to reduce obsession, compulsion, and depression symptoms. Furthermore, patients rated the ACS as more useful for themselves compared with the INS.

Conclusion

The increased left IFG activity using ACS (T1 vs. T2) could be interpreted as a better inhibitory top-down process, while the increased PCC response might be due to a better reappraisal strategy after therapy. ACS seems to mobilise neuronal activations under therapy, especially in the left hemisphere. Both strategies showed reductions in emotional networks as a neuronal correlate of therapy success. Overall, ACS may be more efficient than INS, as rated by the patients and as in accordance with neurobiological findings.

Structural and functional brain imaging after treatment with selective-serotonin reuptake-inhibitors in obsessive-compulsive disorder: A mini review

BACKGROUND

Obsessive-compulsive disorder (OCD) is a psychiatric disorder whose etiopathogenesis, according to various neuroimaging studies, seems to be linked to selective dysfunctions in regions within the cortico-striatal-thalamo-cortical circuit. Selective Serotonin Reuptake Inhibitors (SSRIs) are the first-line therapy for OCD but their neurobiological effects on the brain is only partially understood. Therefore, the aim of this review is to highlight structural and functional brain imaging modifications induced by SSRIs treatment.

METHODS

A literature search on PubMed, Psych-Info and Embase database was performed. Studies including patients with OCD that analyzed the effect of SSRIs through structural and functional Magnetic Resonance Imaging were selected. Seven relevant studies were considered eligible for the present review.

RESULTS

Overall, the results of the reviewed studies showed that SSRIs treatment seems to normalize structural, in terms of the white matter and gray matter volumes, and functional activity alterations observed in OCD patients, especially in regions within the prefrontal cortex and striatum.

LIMITATIONS

The poor design of the studies, the small and heterogeneous samples, differences in age, gender, illness course, comorbidities, treatment protocols and the different magnetic fields used make it difficult to generalize the results.

CONCLUSIONS

From the available evidence it emerged that SSRIs treatment has proven to be effective in normalizing brain structural and functional alterations observed in OCD patients. However, future neuroimaging investigations should focus on long-term effects of drugs on brain structure and function in OCD patients through longitudinal approaches in order to identify more effective treatments for these patients.

Resolving heterogeneity in schizophrenia, bipolar I disorder, and attention-deficit/hyperactivity disorder through individualized structural covariance network analysis

Disruptions in large-scale brain connectivity are hypothesized to contribute to psychiatric disorders, including schizophrenia, bipolar I disorder, and attention-deficit/hyperactivity disorder. However, high inter-individual variation among patients with psychiatric disorders hinders achievement of unified findings. To this end, we adopted a newly proposed method to resolve heterogeneity of differential structural covariance network in schizophrenia, bipolar I disorder, and attention-deficit/hyperactivity disorder. This method could infer individualized structural covariance aberrance by assessing the deviation from healthy controls. T1-weighted anatomical images of 114 patients with psychiatric disorders (schizophrenia: n = 37; bipolar I disorder: n = 37; attention-deficit/hyperactivity disorder: n = 37) and 110 healthy controls were analyzed to obtain individualized differential structural covariance network. Patients exhibited tremendous heterogeneity in profiles of individualized differential structural covariance network. Despite notable heterogeneity, patients with the same disorder shared altered edges at network level. Moreover, individualized differential structural covariance network uncovered two distinct psychiatric subtypes with opposite differences in structural covariance edges, that were otherwise obscured when patients were merged, compared with healthy controls. These results provide new insights into heterogeneity and have implications for the nosology in psychiatric disorders.

A closer look to neural pathways and psychopharmacology of obsessive compulsive disorder

The intricate neural pathways involved in obsessive-compulsive disorder (OCD) affect areas of our brain that control executive functioning, organization, and planning. OCD is a chronic condition that can be debilitating, afflicting millions of people worldwide. The lifetime prevalence of OCD in the US is 2.3%. OCD is predominantly characterized by obsessions consisting of intrusive and unwanted thoughts, often with impulses that are strongly associated with anxiety. Compulsions with OCD encompass repetitive behaviors or mental acts to satisfy their afflicted obsessions or impulses. While these factors can be unique to each individual, it has been widely established that the etiology of OCD is complex as it relates to neuronal pathways, psychopharmacology, and brain chemistry involved and warrants further exploration.

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.

Pathological Networking of Gray Matter Dendritic Density With Classic Brain Morphometries in OCD

Importance

The pathogenesis of obsessive-compulsive disorder (OCD) may involve altered dendritic morphology, but in vivo imaging of neurite morphology in OCD remains limited. Such changes must be interpreted functionally within the context of the multimodal neuroimaging approach to OCD.

Objective

To examine whether dendritic morphology is altered in patients with OCD compared with healthy controls (HCs) and whether such alterations are associated with other brain structural metrics in pathological networks.

Design, Setting, and Participants

This case-control study used cross-sectional data, including multimodal brain images and clinical symptom assessments, from 108 patients with OCD and 108 HCs from 2014 to 2017. Patients with OCD were recruited from Shanghai Mental Health Center, Shanghai, China, and HCs were recruited via advertisements. The OCD group comprised unmedicated adults with a Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) diagnosis of OCD, while the HCs were adults without any DSM-IV diagnosis, matched for age, sex, and education level. Data were analyzed from September 2019 to April 2023.

Exposure

DSM-IV diagnosis of OCD.

Main Outcomes and Measures

Multimodal brain imaging was used to compare neurite microstructure and classic morphometries between patients with OCD and HCs. The whole brain was searched to identify regions exhibiting altered morphology in patients with OCD and explore the interplay between the brain metrics representing these alterations. Brain-symptom correlations were analyzed, and the performance of different brain metric configurations were evaluated in distinguishing patients with OCD from HCs.

Results

Among 108 HCs (median [IQR] age, 26 [23-31] years; 50 [46%] female) and 108 patients with OCD (median [IQR] age, 26 [24-31] years; 46 [43%] female), patients with OCD exhibited deficient neurite density in the right lateral occipitoparietal regions (peak t = 3.821; P ≤ .04). Classic morphometries also revealed widely-distributed alterations in the brain (peak t = 4.852; maximum P = .04), including the prefrontal, medial parietal, cingulate, and fusiform cortices. These brain metrics were interconnected into a pathological brain network associated with OCD symptoms (global strength: HCs, 0.253; patients with OCD, 0.941; P = .046; structural difference, 0.572; P < .001). Additionally, the neurite density index exhibited high discriminatory power in distinguishing patients with OCD from HCs (accuracy, ≤76.85%), and the entire pathological brain network also exhibited excellent discriminative classification properties (accuracy, ≤82.87%).

Conclusions and Relevance

The findings of this case-control study underscore the utility of in vivo imaging of gray matter dendritic density in future OCD research and the development of neuroimaging-based biomarkers. They also endorse the concept of connectopathy, providing a potential framework for interpreting the associations among various OCD symptom-related morphological anomalies.

Theta and Gamma Activity Differences in Obsessive-Compulsive Disorder and Panic Disorder: Insights from Resting-State EEG with eLORETA

Background: Obsessive-compulsive disorder (OCD) and panic disorder (PD) are debilitating psychiatric conditions, yet their underlying neurobiological differences remain underexplored. This study aimed to directly compare resting-state EEGs in patients with OCD and PD, without a healthy control group, using the eLORETA method. Methods: We collected retrospective EEG data from 24 OCD patients and 22 PD patients who were hospitalized due to significant impairment in daily life functions. eLORETA was used to analyze the EEG data. Results: Heightened theta activity was observed in the anterior cingulate cortex (ACC) of OCD patients compared to PD patients (PD vs. OCD, t = -2.168, p < 0.05). Conversely, higher gamma activity was found in the medial frontal gyrus (MFG) and paracentral lobule (PCL) in PD patients (PD vs. OCD, t = 2.173, p < 0.05). Conclusions: Our findings highlight neurobiological differences between OCD and PD patients. Specifically, the increased theta activity in the ACC for OCD patients and elevated gamma activity in the MFG and PCL for PD patients offer preliminary insights into the neural mechanisms of these disorders. Further studies are essential to validate these results and delve deeper into the neural underpinnings.

Glutamatergic abnormalities in the pregenual anterior cingulate cortex in obsessive-compulsive disorder using magnetic resonance spectroscopy: A controlled study

In this study, we utilized proton magnetic resonance spectroscopy (MRS) to understand the role of glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) of OCD patients in the pregenual anterior cingulate cortex (pgACC). In total, 54 patients with OCD and 54 healthy controls (HC) matched for age and sex were included in the study. They underwent MRS in the pgACC region to calculate the concentrations of Glu, Gln, GABA, and Glu + Gln (Glx). After quality control of the MRS data, 21 OCD and 21 HC were statistically analyzed. The severity of symptoms were evaluated using the Yale-Brown Obsessive-Compulsive Scale (YBOCS). In the statistical analysis, we compared differences between groups for the metabolites; in the OCD we analyzed the correlations with symptom severity, medication status, age, and duration of illness. A significant decrease in Glx, in Glu, and in Gln in the pgACC were observed in the OCD compared to HC. The correlation statistics showed a significant positive correlation between Glu levels and the YBOCS compulsions subscale. The results indicate that patients with OCD present a disturbance in glutamatergic metabolism in the pgACC. The results also demonstrate that these changes correlate with the severity of compulsions.

Will Transcranial Magnetic Stimulation Improve the Treatment of Obsessive-Compulsive Disorder? A Systematic Review and Meta-Analysis of Current Targets and Clinical Evidence

BACKGROUND

Although in 2017 a repetitive transcranial magnetic stimulation (rTMS) protocol received Food and Drug Administration approval for the first time for the treatment of obsessive-compulsive disorder (OCD), which neural target and which protocol should be used for OCD are still debated. The aim of the present study was to perform a systematic review and meta-analysis of the available open and sham-controlled trials.

METHODS

The primary analysis included a pairwise meta-analysis (over 31 trials), and then subgroup analyses were performed for each targeted brain area. Meta-regression analyses explored the possible moderators of effect size.

RESULTS

The pairwise meta-analysis showed a significant reduction in OCD symptoms following active rTMS (g = -0.45 [95%CI: -0.62, -0.29]) with moderate heterogeneity (I² = 34.9%). Subgroup analyses showed a significant effect of rTMS over the bilateral pre-SMA (supplementary motor area), the DLPFC (dorsolateral prefrontal cortex), the ACC/mPFC (anterior cingulate cortex and medial prefrontal cortex), and the OFC (orbitofrontal cortex). No moderators of the effect size emerged.

CONCLUSIONS

TMS of several brain targets represents a safe and effective treatment option for OCD patients. Further studies are needed to help clinicians to individualize TMS protocols and targets for each patient.

Cortical glutamate and GABA are related to compulsive behaviour in individuals with obsessive compulsive disorder and healthy controls

There has been little analysis of neurochemical correlates of compulsive behaviour to illuminate its underlying neural mechanisms. We use 7-Tesla proton magnetic resonance spectroscopy (¹H-MRS) to assess the balance of excitatory and inhibitory neurotransmission by measuring glutamate and GABA levels in anterior cingulate cortex (ACC) and supplementary motor area (SMA) of healthy volunteers and participants with Obsessive-Compulsive Disorder (OCD). Within the SMA, trait and clinical measures of compulsive behaviour are related to glutamate levels, whereas a behavioural index of habitual control correlates with the glutamate:GABA ratio. Participants with OCD also show the latter relationship in the ACC while exhibiting elevated glutamate and lower GABA levels in that region. This study highlights SMA mechanisms of habitual control relevant to compulsive behaviour, common to the healthy sub-clinical and OCD populations. The results also demonstrate additional involvement of anterior cingulate in the balance between goal-directed and habitual responding in OCD.

Memantine for Refractory Obsessive-Compulsive Disorder: Protocol for a Pragmatic, Double-blind, Randomized, Parallel-Group, Placebo-Controlled, Monocenter Trial

BACKGROUND

Obsessive-compulsive disorder (OCD) is a psychiatric syndrome characterized by unwanted and repetitive thoughts and repeated ritualistic compulsions for decreasing distress. Symptoms can cause severe distress and functional impairment. OCD affects 2% to 3% of the population and is ranked within the 10 leading neuropsychiatric causes of disability. Cortico-striatal-thalamo-cortical circuitry dysfunction has been implicated in OCD, including altered brain activation and connectivity. Complex glutamatergic signaling dysregulation within cortico-striatal circuitry has been proposed in OCD. Data obtained by several studies indicate reduced glutamatergic concentrations in the anterior cingulate cortex, combined with overactive glutamatergic signaling in the striatum and orbitofrontal cortex. A growing number of randomized controlled trials have assessed the utility of different glutamate-modulating drugs as augmentation medications or monotherapies for OCD, including refractory OCD. However, there are relevant variations among studies in terms of patients' treatment resistance, comorbidity, age, and gender. At present, 4 randomized controlled trials are available on the efficacy of memantine as an augmentation medication for refractory OCD.

OBJECTIVE

Our study's main purpose is to conduct a double-blind, randomized, parallel-group, placebo-controlled, monocenter trial to assess the efficacy and safety of memantine as an augmentative agent to a selective serotonin reuptake inhibitor in the treatment of moderate to severe OCD. The study's second aim is to evaluate the effect of memantine on cognitive functions in patients with OCD. The third aim is to investigate if responses to memantine are modulated by variables such as gender, symptom subtypes, and the duration of untreated illness.

METHODS

Investigators intend to conduct a double-blind, randomized, parallel-group, placebo-controlled, monocenter trial to assess the efficacy and safety of memantine as an augmentative agent to a selective serotonin reuptake inhibitor in the treatment of patients affected by severe refractory OCD. Participants will be rated via the Yale-Brown Obsessive Compulsive Scale at baseline and at 2, 4, 6, 8, 10, and 12 months. During the screening period and T4 and T6 follow-up visits, all participants will undergo an extensive neuropsychological evaluation. The 52-week study duration will consist of 4 distinct periods, including memantine titration and follow-up periods.

RESULTS

Recruitment has not yet started. The study will be conducted from June 2023 to December 2024. Results are expected to be available in January 2025. Throughout the slow-titration period, we will observe the minimum effective dose of memantine, and the follow-up procedure will detail its residual efficacy after drug withdrawal.

CONCLUSIONS

The innovation of this research proposal is not limited to the evaluation of the efficacy and safety of memantine as an augmentation medication for OCD. We will also test if memantine acts as a pure antiobsessive medication or if memantine's ability to improve concentration and attention mimics an antiobsessive effect.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05015595; https://clinicaltrials.gov/ct2/show/NCT05015595.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/39223.

Striatal adenosine A2A receptor involvement in normal and large nest building deer mice: perspectives on compulsivity and anxiety

Obsessive-compulsive disorder (OCD) is characterized by recurring obsessive thoughts and repetitive behaviors that are often associated with anxiety and perturbations in cortico-striatal signaling. Given the suboptimal response of OCD to current serotonergic interventions, there is a need to better understand the psychobiological mechanisms that may underlie the disorder. In this regard, investigations into adenosinergic processes might be fruitful. Indeed, adenosine modulates both anxiety- and motor behavioral output. Thus, we aimed to explore the potential associations between compulsive-like large nest building (LNB) behavior in deer mice, anxiety and adenosinergic processes. From an initial pool of 120 adult deer mice, 34 normal nest building (NNB)- and 32 LNB-expressing mice of both sexes were selected and exposed to either a normal water (wCTRL) or vehicle control (vCTRL), lorazepam (LOR) or istradefylline (ISTRA) for 7- (LOR) or 28 days after which nesting assessment was repeated and animals screened for anxiety-like behavior in an anxiogenic open field. Mice were then euthanized, the striatal tissue removed on ice and the adenosine A_2A receptor expression quantified. Our findings indicate that NNB and LNB behavior are not distinctly associated with measures of generalized anxiety and that ISTRA-induced changes in nesting expression are dissociated from changes in anxiety scores. Further, data from this investigation show that nesting in deer mice is directly related to striatal adenosine signaling, and that LNB is founded upon a lower degree of adenosinergic A_2A stimulation.

Mapping the neuroanatomical heterogeneity of OCD using a framework integrating normative model and non-negative matrix factorization

Obsessive-compulsive disorder (OCD) is a spectrum disorder with high interindividual heterogeneity. We propose a comprehensible framework integrating normative model and non-negative matrix factorization (NMF) to quantitatively estimate the neuroanatomical heterogeneity of OCD from a dimensional perspective. T1-weighted magnetic resonance images of 98 first-episode untreated patients with OCD and matched healthy controls (HCs, n = 130) were acquired. We derived individualized differences in gray matter morphometry using normative model and parsed them into latent disease factors using NMF. Four robust disease factors were identified. Each patient expressed multiple factors and exhibited a unique factor composition. Factor compositions of patients were significantly correlated with severity of symptom, age of onset, illness duration, and exhibited sex differences, capturing sources of clinical heterogeneity. In addition, the group-level morphological differences obtained with two-sample t test could be quantitatively derived from the identified disease factors, reconciling the group-level and subject-level findings in neuroimaging studies. Finally, we uncovered two distinct subtypes with opposite morphological differences compared with HCs from factor compositions. Our findings suggest that morphological differences of individuals with OCD are the unique combination of distinct neuroanatomical patterns. The proposed framework quantitatively estimating neuroanatomical heterogeneity paves the way for precision medicine in OCD.

Identification of shared and distinct patterns of brain network abnormality across mental disorders through individualized structural covariance network analysis

BACKGROUND

Mental disorders, including depression, obsessive compulsive disorder (OCD), and schizophrenia, share a common neuropathy of disturbed large-scale coordinated brain maturation. However, high-interindividual heterogeneity hinders the identification of shared and distinct patterns of brain network abnormalities across mental disorders. This study aimed to identify shared and distinct patterns of altered structural covariance across mental disorders.

METHODS

Subject-level structural covariance aberrance in patients with mental disorders was investigated using individualized differential structural covariance network. This method inferred structural covariance aberrance at the individual level by measuring the degree of structural covariance in patients deviating from matched healthy controls (HCs). T1-weighted anatomical images of 513 participants (105, 98, 190 participants with depression, OCD and schizophrenia, respectively, and 130 age- and sex-matched HCs) were acquired and analyzed.

RESULTS

Patients with mental disorders exhibited notable heterogeneity in terms of altered edges, which were otherwise obscured by group-level analysis. The three disorders shared high difference variability in edges attached to the frontal network and the subcortical-cerebellum network, and they also exhibited disease-specific variability distributions. Despite notable variability, patients with the same disorder shared disease-specific groups of altered edges. Specifically, depression was characterized by altered edges attached to the subcortical-cerebellum network; OCD, by altered edges linking the subcortical-cerebellum and motor networks; and schizophrenia, by altered edges related to the frontal network.

CONCLUSIONS

These results have potential implications for understanding heterogeneity and facilitating personalized diagnosis and interventions for mental disorders.

Transcranial Magnetic Stimulation in Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) patients need novel therapeutic interventions since most experience residual symptoms despite treatment. Converging evidence suggest that OCD involves dysfunction of limbic cortico-striato-thalamo-cortical loops, including the medial prefrontal cortex (mPFC) and dorsal anterior cingulate cortex (dACC), that tends to normalize with successful treatment. Recently, three repetitive transcranial magnetic stimulation (rTMS) coils were FDA-cleared for treatment-refractory OCD. This review presents on-label and off-label clinical evidence and relevant physical characteristics of the three coils. The Deep TMS™ H7 Coil studies' point to efficacy of mPFC-dACC stimulation, while no clear target stems from the small heterogenous D-B80 and figure-8 coils studies.

Individuals with problem gambling and obsessive-compulsive disorder learn through distinct reinforcement mechanisms

Obsessive-compulsive disorder (OCD) and pathological gambling (PG) are accompanied by deficits in behavioural flexibility. In reinforcement learning, this inflexibility can reflect asymmetric learning from outcomes above and below expectations. In alternative frameworks, it reflects perseveration independent of learning. Here, we examine evidence for asymmetric reward-learning in OCD and PG by leveraging model-based functional magnetic resonance imaging (fMRI). Compared with healthy controls (HC), OCD patients exhibited a lower learning rate for worse-than-expected outcomes, which was associated with the attenuated encoding of negative reward prediction errors in the dorsomedial prefrontal cortex and the dorsal striatum. PG patients showed higher and lower learning rates for better- and worse-than-expected outcomes, respectively, accompanied by higher encoding of positive reward prediction errors in the anterior insula than HC. Perseveration did not differ considerably between the patient groups and HC. These findings elucidate the neural computations of reward-learning that are altered in OCD and PG, providing a potential account of behavioural inflexibility in those mental disorders.

Disorder-specific cingulo-opercular network hyperconnectivity in pediatric OCD relative to pediatric anxiety

BACKGROUND

Prior investigation of adult patients with obsessive compulsive disorder (OCD) has found greater functional connectivity within orbitofrontal-striatal-thalamic (OST) circuitry, as well as altered connectivity within and between large-scale brain networks such as the cingulo-opercular network (CON) and default mode network (DMN), relative to controls. However, as adult OCD patients often have high rates of co-morbid anxiety and long durations of illness, little is known about the functional connectivity of these networks in relation to OCD specifically, or in young patients near illness onset.

METHODS

In this study, unmedicated female patients with OCD (ages 8-21 years, n = 23) were compared to age-matched female patients with anxiety disorders (n = 26), and healthy female youth (n = 44). Resting-state functional connectivity was used to determine the strength of functional connectivity within and between OST, CON, and DMN.

RESULTS

Functional connectivity within the CON was significantly greater in the OCD group as compared to the anxiety and healthy control groups. Additionally, the OCD group displayed greater functional connectivity between OST and CON compared to the other two groups, which did not differ significantly from each other.

CONCLUSIONS

Our findings indicate that previously noted network connectivity differences in pediatric patients with OCD were likely not attributable to co-morbid anxiety disorders. Moreover, these results suggest that specific patterns of hyperconnectivity within CON and between CON and OST circuitry may characterize OCD relative to non-OCD anxiety disorders in youth. This study improves understanding of network dysfunction underlying pediatric OCD as compared to pediatric anxiety.

Functional connectivity abnormalities of brain networks in obsessive–compulsive disorder: a systematic review

Obsessive-compulsive disorder (OCD) is characterized by cognitive abnormalities encompassing several executive processes. Neuroimaging studies highlight functional abnormalities of executive fronto-parietal network (FPN) and default-mode network (DMN) in OCD patients, as well as of the prefrontal cortex (PFC) more specifically. We aim at assessing the presence of functional connectivity (FC) abnormalities of intrinsic brain networks and PFC in OCD, possibly underlying specific computational impairments and clinical manifestations. A systematic review of resting-state fMRI studies investigating FC was conducted in unmedicated OCD patients by querying three scientific databases (PubMed, Scopus, PsycInfo) up to July 2022 (search terms: “obsessive–compulsive disorder” AND “resting state” AND “fMRI” AND “function* *connect*” AND “task-positive” OR “executive” OR “central executive” OR “executive control” OR “executive-control” OR “cognitive control” OR “attenti*” OR “dorsal attention” OR “ventral attention” OR “frontoparietal” OR “fronto-parietal” OR “default mode” AND “network*” OR “system*”). Collectively, 20 studies were included. A predominantly reduced FC of DMN – often related to increased symptom severity – emerged. Additionally, intra-network FC of FPN was predominantly increased and often positively related to clinical scores. Concerning PFC, a predominant hyper-connectivity of right-sided prefrontal links emerged. Finally, FC of lateral prefrontal areas correlated with specific symptom dimensions. Several sources of heterogeneity in methodology might have affected results in unpredictable ways and were discussed. Such findings might represent endophenotypes of OCD manifestations, possibly reflecting computational impairments and difficulties in engaging in self-referential processes or in disengaging from cognitive control and monitoring processes.

Disclosing common biological signatures and predicting new therapeutic targets in schizophrenia and obsessive-compulsive disorder by integrated bioinformatics analysis

Schizophrenia (SCZ) is a severe mental illness mainly characterized by a number of psychiatric symptoms. Obsessive-compulsive disorder (OCD) is a long-lasting and devastating mental disorder. SCZ has high co-occurrence with OCD resulting in the emergence of a concept entitled "schizo-obsessive disorder" as a new specific clinical entity with more severe psychiatric symptoms. Many studies have been done on SCZ and OCD, but the common pathogenesis between them is not clear yet. Therefore, this study aimed to identify shared genetic basis, potential biomarkers and therapeutic targets between these two disorders. Gene sets were extracted from the Geneweaver and Harmonizome databases for each disorder. Interestingly, the combination of both sets revealed 89 common genes between SCZ and OCD, the most important of which were BDNF, SLC6A4, GAD1, HTR2A, GRIN2B, DRD2, SLC6A3, COMT, TH and DLG4. Then, we conducted a comprehensive bioinformatics analysis of the common genes. Receptor activity as the molecular functions, neuron projection and synapse as the cellular components as well as serotonergic synapse, dopaminergic synapse and alcoholism as the pathways were the most significant commonalities in enrichment analyses. In addition, transcription factor (TFs) analysis predicted significant TFs such as HMGA1, MAPK14, HINFP and TEAD2. Hsa-miR-3121-3p and hsa-miR-495-3p were the most important microRNAs (miRNAs) associated with both disorders. Finally, our study predicted 19 existing drugs (importantly, Haloperidol, Fluoxetine and Melatonin) that may have a potential influence on this co-occurrence. To summarize, this study may help us to better understand and handle the co-occurrence of SCZ and OCD by identifying potential biomarkers and therapeutic targets.

Role of Sonic Hedgehog Signaling Activation in the Prevention of Neurological Abnormalities Associated with Obsessive-Compulsive Disorder

The smoothened sonic hedgehog (Smo-Shh) pathway is one mechanism that influences neurogenesis, including brain cell differentiation and development during childhood. Shh signaling dysregulation leads to decreased target gene transcription, which contributes to increased neuronal excitation, apoptosis, and neurodegeneration, eventually leading to neurological deficits. Neuropsychiatric disorders such as OCD and related neurological dysfunctions are characterized by neurotransmitter imbalance, neuroinflammation, oxidative stress, and impaired neurogenesis, disturbing the cortico-striato-thalamo-cortical (CSTC) link neuronal network. Despite the availability of several treatments, such as selective serotonin reuptake inhibitors, some individuals may not benefit much from them. Several trials on the use of antipsychotics in the treatment of OCD have also produced inadequate findings. This evidence-based review focuses on a potential pharmacological approach to alleviating OCD and associated neuronal deficits by preventing neurochemical alterations, in which sonic hedgehog activators are neuroprotective, lowering neuronal damage while increasing neuronal maintenance and survival. As a result, stimulating SMO-Shh via its potential activators may have neuroprotective effects on neurological impairment associated with OCD. This review investigates the link between SMO-Shh signaling and the neurochemical abnormalities associated with the progression of OCD and associated neurological dysfunctions. Role of Smo-Shh signaling in serotonergic neurogenesis and in maintaining their neuronal identity. The Shh ligand activates two main transcriptional factors known as Foxa2 and Nkx2.2, which again activates another transcriptional factor, GATA (GATA2 and GATA3), in post mitotic precursor cells of serotonergic neurons-following increased expression of Pet-1 and Lmx1b after GATA regulates the expression of many serotonergic enzymes such as TPH2, SERT, VMAT, slc6a4, Htr1a, Htr1b (Serotonin receptor enzymes), and MAO that regulate and control the release of serotonin and maintain their neuronal identity after their maturation. Abbreviation: Foxa2: Forkhead box; GATA: Globin transcription factor; Lmx1b: LIM homeobox transcription factor 1 beta; TPH2: Tryptophan hydroxylase 2; Htr1a: Serotonin receptor 1a; Htr1b: Serotonin receptor 1b; SERT: Serotonin transporter; VMAT: Vesicular monoamine transporter; MAO: Monoamine oxidase.

Differential patterns of association between resting-state functional connectivity networks and stress in OCD patients

Obsessive-compulsive disorder (OCD) is a highly prevalent psychiatric disorder that is characterized by its complex pathophysiology and heterogenous presentation. Multiple studies to date have identified a variety of factors that are involved in the development of symptoms, but little is known about how these affect brain function. In this study, we have tried to understand how stress, one of the most studied risk factors for OCD, may influence resting-state functional connectivity (rsFC) by comparing resting brain activity of OCD patients with healthy control subjects, while assessing self-reported levels of perceived stress using the Perceived Stress Scale-10 (PSS-10). Seventy-five OCD patients and seventy-one healthy matched control subjects were enrolled in this study, where we used a data-driven, independent component analysis approach. Our results show differences in connectivity between patients and healthy controls involving the dorsal attention (DAN) and lateral visual networks, with patients presenting increased rsFC within the DAN and decreased rsFC within the lateral visual network. Moreover, connectivity in the anterior default mode (aDMN), dorsal attention and basal ganglia networks was associated with PSS scores in OCD patients. Specifically, rsFC within the DAN and aDMN was positively correlated with PSS scores, while the opposite was observed for the basal ganglia network. This study is the first to report such association between rsFC alterations and self-reported stress levels. Our findings are relevant in the context of OCD pathophysiology given evidence of functional dysconnectivity involving the same networks in previous OCD studies and the possible involvement of these changes in the generation of obsessions.

Analysis of lateral orbitofrontal cortex activation on acquisition of fear extinction and neuronal activities in fear circuit

Inappropriate fear expression and failure of fear extinction are commonly seen in patients with post-traumatic stress disorder (PTSD) and obsessive-compulsive disorder (OCD). Among the patients, aberrant and asymmetric activation of the lateral orbitofrontal cortex (lOFC) is reported in some clinical cases. In this study, we aimed to examine the role of lOFC activation in extinction acquisition and explore the potential functional lateralization of lOFC on extinction. We bilaterally or unilaterally activated the lOFC with N-methyl-_D-aspartate (NMDA) before fear extinction acquisition in rats. Our data suggested that both left and bilateral lOFC activation interfered with the in-session expression of conditioned fear, whereas activation of the right lOFC did not. In addition, pre-extinction unilateral or bilateral activation of the lOFC, regardless of the side, impaired the acquisition of fear extinction. We also quantified the neuronal activities during the late phase of extinction with immunohistochemical approach. Our data showed that activation of the lOFC increased the neuronal activities on the injection side(s) in the medial prefrontal cortex (mPFC), the lateral amygdala (LA), the basolateral amygdala (BLA; preferentially the non-GABAergic neurons), and the medial intercalated cells (mITC; preferentially the right side). To conclude, aberrant activation of the lOFC during extinction disturbed the excitatory/inhibitory balance of neuronal activities in fear-related brain regions, which interfered with the expression of conditioned fear and impaired the acquisition of fear extinction.

Aberrant functional connectivity of neural circuits associated with thought-action fusion in patients with obsessive-compulsive disorder

BACKGROUND

Cognitive theories of obsessive-compulsive disorder (OCD) stress the importance of dysfunctional beliefs in the development and maintenance of the disorder. However, a neurobiological understanding of these cognitive models, including thought-action fusion (TAF), is surprisingly lacking. Thus, this functional magnetic resonance imaging study aimed to investigate whether altered functional connectivity (FC) is associated with the TAF paradigm in OCD patients.

METHODS

Forty-one OCD patients and 47 healthy controls (HCs) participated in a functional magnetic resonance imaging study using a TAF task, in which they were asked to read the name of a close or a neutral person in association with positive and negative statements.

RESULTS

The conventional TAF condition (negative statements/close person) induced significant FC between the regions of interest (ROIs) identified using multivoxel pattern analysis and the visual association areas, default mode network subregions, affective processing, and several subcortical regions in both groups. Notably, sparser FC was observed in OCD patients. Further analysis confined to the cortico-striato-thalamo-cortical (CSTC) and affective networks demonstrated that OCD patients exhibited reduced ROI FC with affective regions and greater ROI FC with CSTC components in the TAF condition compared to HCs. Within the OCD patients, middle cingulate cortex-insula FC was correlated with TAF and responsibility scores.

CONCLUSIONS

Our TAF paradigm revealed altered context-dependent engagement of the CSTC and affective networks in OCD patients. These findings suggest that the neurobiology of cognitive models corresponds to current neuroanatomical models of OCD. Further, they elucidate the underlying neurobiological mechanisms of OCD at the circuit-based level.

Aberrant cortico-striatal white matter connectivity and associated subregional microstructure of the striatum in obsessive-compulsive disorder

The striatum and its cortical circuits play central roles in the pathophysiology of obsessive-compulsive disorder (OCD). The striatum is subdivided by cortical connections and functions; however, the anatomical aberrations in different cortico-striatal connections and coexisting microstructural anomalies in striatal subregions of OCD patients are poorly understood. Thus, we aimed to elucidate the aberrations in cortico-striatal white matter (WM) connectivity and the associated subregional microstructure of the striatum in patients with OCD. From diffusion tensor/kurtosis imaging of 107 unmedicated OCD patients and 110 matched healthy controls (HCs), we calculated the cortico-striatal WM connectivity and segmented the striatum using probabilistic tractography. For the segmented striatal subregions, we measured average diffusion kurtosis values, which represent microstructural complexity. Connectivity and mean kurtosis values in each cortical target and associated striatal subregions were compared between groups. We identified significantly reduced orbitofrontal WM connectivity with its associated striatal subregion in patients with OCD compared to that in HCs. However, OCD patients exhibited significantly increased caudal-motor and parietal connectivity with the associated striatal subregions. The mean kurtosis values of the striatal subregions connected to the caudal-motor and parietal cortex were significantly decreased in OCD patients. Our results highlighted contrasting patterns of striatal WM connections with the orbitofrontal and caudal-motor/parietal cortices, thus supporting the cortico-striatal circuitry imbalance model of OCD. We suggest that aberrations in WM connections and the microstructure of their downstream regions in the caudal-motor-/parietal-striatal circuits may underlie OCD pathophysiology and further provide potential neuromodulation targets for the treatment of OCD.

Resting-State Functional Connectivity Differences Following Experimental Manipulation of the Orbitofrontal Cortex in Two Directions via Theta-Burst Stimulation

Compulsive behaviors (CBs) have been linked to orbitofrontal cortex (OFC) function in animal and human studies. However, brain regions function not in isolation but as components of widely distributed brain networks—such as those indexed via resting-state functional connectivity (RSFC). Sixty-nine individuals with CB disorders were randomized to receive a single session of neuromodulation targeting the left OFC—intermittent theta-burst stimulation (iTBS) or continuous TBS (cTBS)—followed immediately by computer-based behavioral “habit override” training. OFC seeds were used to quantify RSFC following iTBS and following cTBS. Relative to cTBS, iTBS showed increased RSFC between right OFC (Brodmann’s area 47) and other areas, including dorsomedial prefrontal cortex (dmPFC), occipital cortex, and a priori dorsal and ventral striatal regions. RSFC connectivity effects were correlated with OFC/frontopolar target engagement and with subjective difficulty during habit-override training. Findings help reveal neural network-level impacts of neuromodulation paired with a specific behavioral context, informing mechanistic intervention development.

The Role of SliTrk5 in Central Nervous System

SLIT and NTRK-like protein-5 (SliTrk5) is one of the six members of SliTrk protein family, which is widely expressed in the central nervous system (CNS), regulating and participating in many essential steps of central nervous system development, including axon and dendritic growth, neuron differentiation, and synaptogenesis. SliTrk5, as a neuron transmembrane protein, contains two important conservative domains consisting of leucine repeats (LRRs) located at the amino terminal in the extracellular region and tyrosine residues (Tyr) located at the carboxyl terminal in the intracellular domains. These special structures make SliTrk5 play an important role in the pathological process of the CNS. A large number of studies have shown that SliTrk5 may be involved in the pathogenesis of CNS diseases, such as obsessive-compulsive-disorder (OCD), attention deficit/hyperactivity disorder (ADHD), glioma, autism spectrum disorders (ASDs), and Parkinson's disease (PD). Targeting SliTrk5 is expected to become a new target for the treatment of CNS diseases, promoting the functional recovery of CNS. The purpose of this article is to review the current research progression of the role of SliTrk5 in CNS and its potential mechanisms in CNS diseases.

BDNF Alleviates Microglial Inhibition and Stereotypic Behaviors in a Mouse Model of Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a severe mental illness characterized by obsessions and compulsions. However, its underlying mechanisms remain to be elucidated. Recent studies have suggested that neuroimmune dysregulation is involved in the pathogenesis of OCD. To investigate the role of microglia in this disorder, we established a pharmacological mouse model by using the serotonin (5-HT) 1A/1B receptor agonist RU24969 to mimic monoamine dysregulation in OCD, and we examined the morphological and functional alterations of microglia in this model. We found that RU24969 treatment led to compulsive circling behavior in mice. Strikingly, we found that the density and mobility of microglia in the prelimbic cortex were much lower in RU24969-treated mice than in control mice. Moreover, the expression of cytokines and chemokines, including BDNF, IL-1β, IL-6, TNFα, CD80, CD86, MHC-I, and MHC-II, also decreased in RU24969-treated mice. Importantly, we found that injection of BDNF or induction of BDNF expression by trehalose completely reversed microglial dysfunction and reduced stereotypic behavior. These results indicate that microglial dysfunction is closely related to stereotypic behaviors in our mouse model of OCD and that BDNF could be an effective treatment for stereotypic behaviors.

Two distinct subtypes of obsessive compulsive disorder revealed by a framework integrating multimodal neuroimaging information

Patients with obsessive compulsive disorder (OCD) exhibit tremendous heterogeneity in structural and functional neuroimaging aberrance. However, most previous studies just focus on group‐level aberrance of a single modality ignoring heterogeneity and multimodal features. On that account, we aimed to uncover OCD subtypes integrating structural and functional neuroimaging features with the help of a multiview learning method and examined multimodal aberrance for each subtype. Ninety‐nine first‐episode untreated patients with OCD and 104 matched healthy controls (HCs) undergoing structural and functional MRI were included in this study. Voxel‐based morphometric and amplitude of low‐frequency fluctuation (ALFF) were adopted to assess gray matter volumes (GMVs) and the spontaneous neuronal fluctuations respectively. Structural/functional distance network was obtained by calculating Euclidean distance between pairs of regional GMVs/ALFF values across patients. Similarity network fusion, one of multiview learning methods capturing shared and complementary information from multimodal data sources, was used to fuse multimodal distance networks into one fused network. Then spectral clustering was adopted to categorize patients into subtypes. As a result, two robust subtypes were identified. These two subtypes presented opposite GMV aberrance and distinct ALFF aberrance compared with HCs while shared indistinguishable clinical and demographic features. In addition, these two subtypes exhibited opposite structure–function difference correlation reflecting distinct adaptive modifications between multimodal aberrance. Altogether, these results uncover two objective subtypes with distinct multimodal aberrance and provide a new insight into taxonomy of OCD.

Neurocircuit dynamics of arbitration between decision-making strategies across obsessive-compulsive and related disorders

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Obsessive-compulsive and related disorders (OCRD) include OCD and BDD.

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Neural differences in decision-making arbitration may underlie OCRD symptoms.

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Resting-state effective connectivity was used to assess arbitration circuitry.

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Greater left putamen inhibition via left ventrolateral prefrontal cortex in OCRD.

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Stronger left putamen inhibition was correlated with less severe symptoms.

Obsessions and compulsions are central components of obsessive–compulsive disorder (OCD) and obsessive–compulsive related disorders such as body dysmorphic disorder (BDD). Compulsive behaviours may result from an imbalance of habitual and goal-directed decision-making strategies. The relationship between these symptoms and the neural circuitry underlying habitual and goal-directed decision-making, and the arbitration between these strategies, remains unknown. This study examined resting state effective connectivity between nodes of these systems in two cohorts with obsessions and compulsions, each compared with their own corresponding healthy controls: OCD (n_OCD = 43; n_healthy = 24) and BDD (n_BDD = 21; n_healthy = 16). In individuals with OCD, the left ventrolateral prefrontal cortex, a node of the arbitration system, exhibited more inhibitory causal influence over the left posterolateral putamen, a node of the habitual system, compared with controls. Inhibitory causal influence in this connection showed a trend for a similar pattern in individuals with BDD compared with controls. Those with stronger negative connectivity had lower obsession and compulsion severity in both those with OCD and those with BDD. These relationships were not evident within the habitual or goal-directed circuits, nor were they associated with depressive or anxious symptomatology. These results suggest that abnormalities in the arbitration system may represent a shared neural phenotype across these two related disorders that is specific to obsessive–compulsive symptoms. In addition to nosological implications, these results identify potential targets for novel, circuit-specific treatments.

Two distinct subtypes of obsessive compulsive disorder revealed by heterogeneity through discriminative analysis

Neurobiological heterogeneity in obsessive compulsive disorder (OCD) is understudied leading to conflicting neuroimaging findings. Therefore, we investigated objective neuroanatomical subtypes of OCD by adopting a newly proposed method based on gray matter volumes (GMVs). GMVs were derived from T1‐weighted anatomical images of patients with OCD (n = 100) and matched healthy controls (HCs; n = 106). We first inquired whether patients with OCD presented higher interindividual variability HCs in terms of GMVs. Then, we identified distinct subtypes of OCD by adopting heterogeneity through discriminative analysis (HYDRA), where regional GMVs were treated as features. Patients with OCD presented higher interindividual variability than HCs, suggesting a high structural heterogeneity of OCD. HYDRA identified two distinct robust subtypes of OCD presenting opposite neuroanatomical aberrances compared with HCs, while sharing indistinguishable clinical and demographic features. Specifically, Subtype 1 exhibited widespread increased GMVs in cortical and subcortical regions, including the orbitofrontal gyrus, right anterior insula, bilateral hippocampus, and bilateral parahippocampus and cerebellum. Subtype 2 demonstrated overall decreased GMVs in regions such as the orbitofrontal gyrus, right anterior insula, and precuneus. When mixed together, none of patients presented significant differences compared with HCs. In addition, the total intracranial volume of Subtype 2 was significantly correlated with the total score of the Yale–Brown Obsessive Compulsive Scale while that of Subtype 1 was not. These results identified two distinct neuroanatomical subtypes, providing a possible explanation for conflicting neuroimaging findings, and proposed a potential objective taxonomy contributing to precise clinical diagnosis and treatment in OCD.

We Move or Are We Moved? Unpicking the Origins of Voluntary Movements to Better Understand Semivoluntary Movements

The capacity for voluntary control is seen as essential to human movements; the sense that one intended to move (willing) and those actions were self-generated (self-agency) gives the sense of voluntariness and of being in control. While the mechanisms underlying voluntary movement have long been unclear, recent neuroscientific tools have identified networks of different brain areas, namely, the prefrontal cortex, supplementary motor area, and parietal cortex, that underlie voluntary action. Dysfunction in these brain areas can result in different forms of semivoluntary movement as the borderland of voluntary and involuntary movement where a person may experience a disordered sense of will or agency, and thus the movement is experienced as unexpected and involuntary, for an otherwise voluntary-appearing movement. Tics, functional movement disorders, stereotypies, perseveration, compulsions, utilization behaviors, and motor mannerism have been described elsewhere in the context of psychoses, and are often mistaken for each other. Yet, they reflect an impairment of prefrontal cortices and related circuits rather than simple motor systems, which results in the absence of subjective recognition of the movements, in contrast to other neurological movement disorders where principal abnormalities are located within the basal ganglia and its connections. Therefore, their recognition is clinically important since they are usually associated with neurodevelopmental and neurodegenerative disorders. In this review, we first defined a conceptual framework, from both a neuroanatomical and a neurophysiological point of view, for the generation of voluntary movement. We then examined the evidence linking dysfunctions in different motor pathways to each type of movement disorder. We looked at common semivoluntary movement disorders providing an overview, where possible, of their phenomenology and brain network abnormalities for each condition. We also emphasized important clinical feature similarities and differences to increase recognition of each condition in practice.

Memantine augmentation of sertraline in the treatment of symptoms and executive function among patients with obsessive-compulsive disorder: A double-blind placebo-controlled, randomized clinical trial

BACKGROUND

Medications currently recommended for the treatment of Obsessive-Compulsive Disorder (OCD) usually decrease the severity of the symptoms by 20-30%; however, 40-60% of OCD patients do not achieve a satisfactory response. Our main objective was to investigate the effectiveness of memantine, a non-competitive N-Methyl-D-aspartate (NMDA) receptor antagonist, as an adjunct therapy to sertraline, a selective serotonin reuptake inhibitor (SSRI), to improve severity of symptoms and executive function among patients with obsessive-compulsive disorder.

METHODS

Seventy patients with OCD according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria, and a Yale-Brown obsessive compulsive scale (Y-BOCS) score of more than 21 were recruited to the study. They received sertraline (100 mg daily initially followed by 200 mg daily after week 4) and either memantine (10 mg twice daily) or placebo in a placebo controlled, double-blinded, parallel-group, clinical trial of 12 weeks. The primary outcome was OCD symptoms measured by the Y-BOCS. Moreover, executive function of participants was measured by the Wisconsin Card Sorting Test (WCST).

RESULTS

The total score, and obsession and compulsion subscales of Y-BOCS significantly dropped in both groups with no significant difference between the two groups. However, memantine group showed a greater response in the number of completed categories subscale of the WCST (p value<0.001). We did not observe any major adverse effects in any of the groups.

CONCLUSION

Memantine has an acceptable safety and tolerability in patients with OCD and might have a positive effect on their executive function. Nevertheless, the current results don`t support the efficacy of memantine as an adjunctive agent to sertraline for symptoms in patients with OCD.

TRIAL REGISTRATION

The trial was registered at the Iranian Registry of Clinical Trials on 04/10/2019 ( www.irct.ir ; IRCT ID: IRCT20170123032145N4).

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.

Neurosurgery and neuromodulation for anorexia nervosa in the 21st century: a systematic review of treatment outcomes

As current psychosocial and pharmacological interventions show limited efficacy in the treatment of anorexia nervosa (AN), interest in the potential value of neurosurgical intervention and neuromodulation in managing severe and enduring illness has grown. We conducted a systematic review of 20 trials of neurosurgical and neuromodulatory treatments for AN, including neurosurgical ablation, deep brain stimulation (DBS), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS). Overall, there is evidence to support the role of stereotactic ablation and DBS in the treatment of AN. In contrast, results for rTMS and tDCS have been modest and generally more mixed. Neurosurgical treatment may offer important new avenues for the treatment of AN. Additional randomized clinical trials with comparable patient populations will be needed, in which change in affective, cognitive, and perceptual symptom phenomena, and interrogation of targeted circuits, pre- and post-intervention, are carefully documented.

Efficacy and Safety of Deep Transcranial Magnetic Stimulation for Obsessive-Compulsive Disorder: A Prospective Multicenter Randomized Double-Blind Placebo-Controlled Trial

(Appeared originally in American Journal of Psychiatry 2019; 176:931-938) Reprinted with permission from American Psychiatric Association Publishing.

Higher brain structural heterogeneity in schizophrenia

As a highly heterogeneous disorder, schizophrenia shows notable interindividual variation in clinical manifestations. On that account, an increasing number of studies begin to examine the interindividual variability in neuroimaging characterization in schizophrenia. However, whether schizophrenia demonstrates higher interindividual morphological variability than health controls (HCs) remains unknown. T1-weighted anatomical images were obtained from patients with schizophrenia (n = 61) and matched HCs (n = 73). For each subject, voxel-wise gray matter volume was obtained using voxel-based morphometry analysis. We first inquired whether patients with schizophrenia showed higher interindividual structural variation than HCs using the person based similarity index (PBSI). Then, we examined differences of voxel-wise morphological coefficient of variation (CV) between schizophrenia and HCs. To further associate identified regions showing higher variability in schizophrenia with cognitive/functional processes, functional annotation was performed. Patients with schizophrenia exhibited lower PBSIs than matched HCs, suggesting higher interindividual morphological variability in schizophrenia. The following results showed that patients with schizophrenia exhibited higher CVs than HCs in distributed brain regions including the striatum, hippocampus, thalamus, parahippocampa gyrus, frontal gyrus, and amygdala. Brain regions showing higher CVs in schizophrenia were significantly implicated in affective, incentive and reward related terms. These results provide a new insight into the high clinical heterogeneity and facilitate personalized diagnose and treatment in schizophrenia.

The prefrontal cortex and neurosurgical treatment for intractable OCD

Over the past two decades, circuit-based neurosurgical procedures have gained increasing acceptance as a safe and efficacious approach to the treatment of the intractable obsessive-compulsive disorder (OCD). Lesions and deep brain stimulation (DBS) of the longitudinal corticofugal white matter tracts connecting the prefrontal cortex with the striatum, thalamus, subthalamic nucleus (STN), and brainstem implicate orbitofrontal, medial prefrontal, frontopolar, and ventrolateral cortical networks in the symptoms underlying OCD. The highly parallel distributed nature of these networks may explain the relative lack of adverse effects observed following surgery. Additional pre-post studies of cognitive tasks in more surgical patients are needed to confirm the role of these networks in OCD and to define therapeutic responses to surgical intervention.

Functional connectivity alterations between default mode network and occipital cortex in patients with obsessive-compulsive disorder (OCD)

Altered brain network connectivity is a potential biomarker for obsessive-compulsive disorder (OCD). A meta-analysis of resting-state MRI studies by Gürsel et al. (2018) described altered functional connectivity in OCD patients within and between the default mode network (DMN), the salience network (SN), and the frontoparietal network (FPN), as well as evidence for aberrant fronto-striatal circuitry. Here, we tested the replicability of these meta-analytic rsfMRI findings by measuring functional connectivity during resting-state fMRI in a new sample of OCD patients (n = 24) and matched controls (n = 33). We performed seed-to-voxel analyses using 30 seed regions from the prior meta-analysis. OCD patients showed reduced functional connectivity between the SN and the DMN compared to controls, replicating previous findings. We did not observe significant group differences of functional connectivity within the DMN, SN, nor FPN. Additionally, we observed reduced connectivity between the visual network to both the DMN and SN in OCD patients, in particular reduced functional connectivity between lateral parietal seeds and the left inferior lateral occipital pole. Furthermore, the right lateral parietal seed (associated with the DMN) was more strongly correlated with a cluster in the right lateral occipital cortex and precuneus (a region partly overlapping with the Dorsal Attentional Network (DAN)) in patients. Importantly, this latter finding was positively correlated to OCD symptom severity. Overall, our study partly replicated prior meta-analytic findings, highlighting hypoconnectivity between SN and DMN as a potential biomarker for OCD. Furthermore, we identified changes between the SN and the DMN with the visual network. This suggests that abnormal connectivity between cortex regions associated with abstract functions (transmodal regions such as the DMN), and cortex regions associated with constrained neural processing (unimodal regions such as the visual cortex), may be important in OCD.

Imbalance in Functional and Structural Connectivity Underlying Goal-Directed and Habitual Learning Systems in Obsessive-Compulsive Disorder

An imbalance between the goal-directed and habitual learning systems has been proposed to underlie compulsivity in obsessive-compulsive disorder (OCD). In addition, the overall balance between these systems may be influenced by stress hormones. We examined the multimodal networks underlying these dual learning systems. Both functional and structural measures indicated reduced connectivity within the goal-directed subnetwork (FC: P = 0.042; SC-FN: P = 0.014) and reduced connectivity between the goal-directed and habitual subnetworks (FC: P = 0.014; SC-FA: P = 0.052), but no differences within the habitual subnetwork in patients with OCD compared with controls. Path modeling indicated that anatomical connectivity in the goal-directed subnetwork influenced compulsive symptoms (R2 = 0.41), whereas functional connectivity within the habit subnetwork and between goal-directed and habitual subnetworks influenced obsessive symptoms (R2 = 0.63). In addition, the relationship between anatomical connectivity in the goal-directed subnetwork and compulsion was moderated by the stress hormone ACTH (adrenocorticotropic hormone), such that at low levels of ACTH greater connectivity resulted in lower compulsion, but at high levels of ACTH this relationship was reversed. These results provide new insights into the neural correlates of the imbalance between dual learning systems, and their relationship with symptom dimensions in patients with OCD. It may further support the reconceptualization of OCD as "compulsive-obsessive disorder," with a greater focus on the transdiagnostic dimension of compulsivity.

A Unified Functional Network Target for Deep Brain Stimulation in Obsessive-Compulsive Disorder

BACKGROUND

Multiple deep brain stimulation (DBS) targets have been proposed for treating intractable obsessive-compulsive disorder (OCD). Here, we investigated whether stimulation effects of different target sites would be mediated by one common or several segregated functional brain networks.

METHODS

First, seeding from active electrodes of 4 OCD patient cohorts (N = 50) receiving DBS to anterior limb of the internal capsule or subthalamic nucleus zones, optimal functional connectivity profiles for maximal Yale-Brown Obsessive Compulsive Scale improvements were calculated and cross-validated in leave-one-cohort-out and leave-one-patient-out designs. Second, we derived optimal target-specific connectivity patterns to determine brain regions mutually predictive of clinical outcome for both targets and others predictive for either target alone. Functional connectivity was defined using resting-state functional magnetic resonance imaging data acquired in 1000 healthy participants.

RESULTS

While optimal functional connectivity profiles showed both commonalities and differences between target sites, robust cross-predictions of clinical improvements across OCD cohorts and targets suggested a shared network. Connectivity to the anterior cingulate cortex, insula, and precuneus, among other regions, was predictive regardless of stimulation target. Regions with maximal connectivity to these commonly predictive areas included the insula, superior frontal gyrus, anterior cingulate cortex, and anterior thalamus, as well as the original stereotactic targets.

CONCLUSIONS

Pinpointing the network modulated by DBS for OCD from different target sites identified a set of brain regions to which DBS electrodes associated with optimal outcomes were functionally connected-regardless of target choice. On these grounds, we establish potential brain areas that could prospectively inform additional or alternative neuromodulation targets for obsessive-compulsive disorder.

Genetics of obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a psychiatric disorder with multiple symptom dimensions (e.g. contamination, symmetry). OCD clusters in families and decades of twin studies clearly demonstrate an important role for genetics in the etiology of the disorder.

METHODS

In this review, we summarize the genetic epidemiology and molecular genetic studies of OCD and obsessive-compulsive symptoms.

RESULTS

OCD is a heritable, polygenic disorder with contributions from both common and rare variants, including de novo deleterious variations. Multiple studies have provided reliable support for a large additive genetic contribution to liability to OCD, with discrete OCD symptom dimensions having both shared and unique genetic risks. Genome-wide association studies have not produced significant results yet, likely because of small sample sizes, but larger meta-analyses are forthcoming. Both twin and genome-wide studies show that OCD shares genetic risk with its comorbid conditions (e.g. Tourette syndrome and anorexia nervosa).

CONCLUSIONS

Despite significant efforts to uncover the genetic basis of OCD, the mechanistic understanding of how genetic and environmental risk factors interact and converge at the molecular level to result in OCD's heterogeneous phenotype is still mostly unknown. Future investigations should increase ancestral genetic diversity, explore age and/or sex differences in genetic risk for OCD and expand the study of pharmacogenetics, gene expression, gene × environment interactions and epigenetic mechanisms for OCD.