A trans-diagnostic perspective on obsessive-compulsive disorder

Distinct neural networks associated with obsession and delusion: a connectome-wide association study

BACKGROUND

Obsession and delusion are theoretically distinct from each other in terms of reality testing. Despite such phenomenological distinction, no extant studies have examined the identification of common and distinct neural correlates of obsession and delusion by employing biologically grounded methods. Here, we investigated dimensional effects of obsession and delusion spanning across the traditional diagnostic boundaries reflected upon the resting-state functional connectivity (RSFC) using connectome-wide association studies (CWAS).

METHODS

Our study sample comprised of 96 patients with obsessive-compulsive disorder, 75 patients with schizophrenia, and 65 healthy controls. A connectome-wide analysis was conducted to examine the relationship between obsession and delusion severity and RFSC using multivariate distance-based matrix regression.

RESULTS

Obsession was associated with the supplementary motor area, precentral gyrus, and superior parietal lobule, while delusion was associated with the precuneus. Follow-up seed-based RSFC and modularity analyses revealed that obsession was related to aberrant inter-network connectivity strength. Additional inter-network analyses demonstrated the association between obsession severity and inter-network connectivity between the frontoparietal control network and the dorsal attention network.

CONCLUSIONS

Our CWAS study based on the Research Domain Criteria (RDoC) provides novel evidence for the circuit-level functional dysconnectivity associated with obsession and delusion severity across diagnostic boundaries. Further refinement and accumulation of biomarkers from studies embedded within the RDoC framework would provide useful information in treating individuals who have some obsession or delusion symptoms but cannot be identified by the category of clinical symptoms alone.

Lost in translation: no effect of repeated optogenetic cortico-striatal stimulation on compulsivity in rats

The orbitofrontal cortex-ventromedial striatum (OFC-VMS) circuitry is widely believed to drive compulsive behavior. Hyperactivating this pathway in inbred mice produces excessive and persistent self-grooming, which has been considered a model for human compulsivity. We aimed to replicate these findings in outbred rats, where there are few reliable compulsivity models. Male Long-Evans rats implanted with optical fibers into VMS and with opsins delivered into OFC received optical stimulation at parameters that produce OFC-VMS plasticity and compulsive grooming in mice. We then evaluated rats for compulsive self-grooming at six timepoints: before, during, immediately after, and 1 h after each stimulation, 1 and 2 weeks after the ending of a 6-day stimulation protocol. To further test for effects of OFC-VMS hyperstimulation, we ran animals in three standard compulsivity assays: marble burying, nestlet shredding, and operant attentional set-shifting. OFC-VMS stimulation did not increase self-grooming or induce significant changes in nestlet shredding, marble burying, or set-shifting in rats. Follow-on evoked potential studies verified that the stimulation protocol altered OFC-VMS synaptic weighting. In sum, although we induced physiological changes in the OFC-VMS circuitry, we could not reproduce in a strongly powered study in rats a model of compulsive behavior previously reported in mice. This suggests possible limitations to translation of mouse findings to species higher on the phylogenetic chain.

Specialty knowledge and competency standards for pharmacotherapy for pediatric obsessive-compulsive disorder

Evidence based treatments for pediatric Obsessive-Compulsive Disorder (OCD) are delivered with varying levels of expertise. This paper is part of the phase two series by the International OCD Accreditation Task Force (ATF) to advance a standardized high level of care globally. This paper presents specific knowledge and competencies recommended for specialized practice for pediatric psychopharmacologists working with OCD, developed by an international group of clinicians with extensive expertise in assessment and treatment of OCD. Tabulated knowledge and competency standards are operationalized as clinician abilities with specification of evidence for each standard. The distinction between current practice guidelines and ATF standards is discussed. Drug treatment has a solid evidence base. However, it should not be applied isolated, but informed by broad competence in general child and adolescent psychiatry and pediatrics. Other treatment relevant areas such as specialty CBT, family functioning, developmental issues, and neurobiology require consideration. Drug treatment includes several phases with varying degrees of evidence: Starting up medication, titration to maximum tolerated dose, maintenance, termination, and relapse prevention. In complex cases, pharmacotherapy with weak evidence may be needed to target symptoms and/or co-morbidity. The ATF knowledge and competency standards presented will be reviewed and updated commensurate with research.

Efficacy and safety of transcranial direct current stimulation as an add-on treatment for obsessive-compulsive disorder: a randomized, sham-controlled trial

Obsessive-compulsive disorder (OCD) is a frequent, disabling disorder with high rates of treatment resistance. Transcranial direct current stimulation (tDCS) is a safe, tolerable noninvasive neuromodulation therapy with scarce evidence for OCD. This double-blind, randomized, and sham-controlled study investigates the efficacy of tDCS as add-on treatment for treatment-resistant OCD (failure to respond to at least one previous pharmacological treatment). On 20 consecutive weekdays (4 weeks), 43 patients with treatment-resistant OCD underwent 30 min active or sham tDCS sessions, followed by a 8 week follow-up. The cathode was positioned over the supplementary motor area (SMA) and the anode over the left deltoid. The primary outcome was the change in baseline Y-BOCS score at week 12. Secondary outcomes were changes in mood and anxiety and the occurrence of adverse events. Response was evaluated considering percent decrease of baseline Y-BOCS scores and the Improvement subscale of the Clinical Global Impression (CGI-I) between baseline and week 12. Patients that received active tDCS achieved a significant reduction of OCD symptoms than sham, with mean (SD) Y-BOCS score changes of 6.68 (5.83) and 2.84 (6.3) points, respectively (Cohen's d: 0.62 (0.06-1.18), p = 0.03). We found no between-group differences in responders (four patients in the active tDCS and one in the sham group). Active tDCS of the SMA was not superior to sham in reducing symptoms of depression or anxiety. Patients in both groups reported mild adverse events. Our results suggest that cathodal tDCS over the SMA is an effective add-on strategy in treatment-resistant OCD.

A Psychophysical Window onto the Subjective Experience of Compulsion

In this perspective, we follow the idea that an integration of cognitive models with sensorimotor theories of compulsion is required to understand the subjective experience of compulsive action. We argue that cognitive biases in obsessive-compulsive disorder may obscure an altered momentary, pre-reflective experience of sensorimotor control, whose detection thus requires an implicit experimental operationalization. We propose that a classic psychophysical test exists that provides this implicit operationalization, i.e., the intentional binding paradigm. We show how intentional binding can pit two ideas against each other that are fundamental to current sensorimotor theories of compulsion, i.e., the idea of excessive conscious monitoring of action, and the idea that patients with obsessive-compulsive disorder compensate for diminished conscious access to "internal states", including states of the body, by relying on more readily observable proxies. Following these ideas, we develop concrete, testable hypotheses on how intentional binding changes under the assumption of different sensorimotor theories of compulsion. Furthermore, we demonstrate how intentional binding provides a touchstone for predictive coding accounts of obsessive-compulsive disorder. A thorough empirical test of the hypotheses developed in this perspective could help explain the puzzling, disabling phenomenon of compulsion, with implications for the normal subjective experience of human action.

High-frequency neuromodulation improves obsessive-compulsive behavior

Nearly one billion people worldwide suffer from obsessive-compulsive behaviors^1,2, yet our mechanistic understanding of these behaviors is incomplete, and effective therapeutics are unavailable. An emerging perspective characterizes obsessive-compulsive behaviors as maladaptive habit learning^3,4, which may be associated with abnormal beta-gamma neurophysiology of the orbitofrontal-striatal circuitry during reward processing^5,6. We target the orbitofrontal cortex with alternating current, personalized to the intrinsic beta-gamma frequency of the reward network, and show rapid, reversible, frequency-specific modulation of reward- but not punishment-guided choice behavior and learning, driven by increased exploration in the setting of an actor-critic architecture. Next, we demonstrate that chronic application of the procedure over 5 days robustly attenuates obsessive-compulsive behavior in a non-clinical population for 3 months, with the largest benefits for individuals with more severe symptoms. Finally, we show that convergent mechanisms underlie modulation of reward learning and reduction of obsessive-compulsive symptoms. The results contribute to neurophysiological theories of reward, learning and obsessive-compulsive behavior, suggest a unifying functional role of rhythms in the beta-gamma range, and set the groundwork for the development of personalized circuit-based therapeutics for related disorders.

Whole genome analyses reveal significant convergence in obsessive-compulsive disorder between humans and dogs

Obsessive-compulsive disorder (OCD) represents a heterogeneous collection of diseases with diverse levels of phenotypic, genetic, and etiologic variability, making it difficult to identify the underlying genetic and biological mechanisms in humans. Domestic dogs exhibit several OCD-like behaviors. Using continuous circling as a representative phenotype for OCD, we screened two independent dog breeds, the Belgian Malinois and Kunming Dog and subsequently sequenced ten circling dogs and ten unaffected dogs for each breed. Using population differentiation analyses, we identified 11 candidate genes in the extreme tail of the differentiated regions between cases and controls. These genes overlap significantly with genes identified in a genome wide association study (GWAS) of human OCD, indicating strong convergence between humans and dogs. Through gene expressional analysis and functional exploration, we found that two candidate OCD risk genes, PPP2R2B and ADAMTSL3, affected the density and morphology of dendritic spines. Therefore, changes in dendritic spine may underlie some common biological and physiological pathways shared between humans and dogs. Our study revealed an unprecedented level of convergence in OCD shared between humans and dogs, and highlighted the importance of using domestic dogs as a model species for many human diseases including OCD.

The Error-Related Negativity Predicts Self-Control Failures in Daily Life

Adaptive behavior critically depends on performance monitoring (PM), the ability to monitor action outcomes and the need to adapt behavior. PM-related brain activity has been linked to guiding decisions about whether action adaptation is warranted. The present study examined whether PM-related brain activity in a flanker task, as measured by electroencephalography (EEG), was associated with adaptive behavior in daily life. Specifically, we were interested in the employment of self-control, operationalized as self-control failures (SCFs), and measured using ecological momentary assessment. Analyses were conducted using an adaptive elastic net regression to predict SCFs from EEG in a sample of 131 participants. The model was fit using within-subject averaged response-locked EEG activity at each electrode and time point within an epoch surrounding the response. We found that higher amplitudes of the error-related negativity (ERN) were related to fewer SCFs. This suggests that lower error-related activity may relate to lower recruitment of interventive self-control in daily life. Altered cognitive control processes, like PM, have been proposed as underlying mechanisms for various mental disorders. Understanding how alterations in PM relate to regulatory control might therefore aid in delineating how these alterations contribute to different psychopathologies.

Electroencephalographic Correlates of Obsessive-Compulsive Disorder

This chapter reviews EEG research in Obsessive-Compulsive Disorder (OCD), focusing on Event-Related Potentials (ERPs) such as the Contingent Negative Variation, N2, Error-Related Negativity, the feedback Error-Related Negativity and the Readiness Potential and their neural bases. The functional significance, utility and correlation of these ERPs with OCD symptoms will be discussed, alongside novel theories for integrating the research findings. I will consider hypotheses including goal-directed behaviour, overreliance on habits, dissociations between action and knowledge, and excessive intolerance of uncertainty in the context of EEG studies, thus providing a comprehensive framework of the electroencephalographic literature concerning OCD.

Neurocognitive Endophenotypes of OCD

In this chapter, I address the concept of endophenotypes for obsessive-compulsive disorder (OCD). Endophenotypes are objective and heritable quantitative traits hypothesized to be more biologically tractable than distal clinical phenotypes. This approach has been adopted to gain a better understanding of psychiatric conditions in general. It is theorized that endophenotypes will particularly assist in clarifying both the diagnostic status and aetiological origins of complex neuropsychiatric conditions such as OCD. At the cognitive level, separable constructs of relevance for OCD have been identified. The prevailing model for OCD assumes the development of abnormalities within fronto-striatal neural circuits leading to impairment of executive functions and their neuropsychological subcomponents. Here, I address whether this model can guide towards the identification of endophenotypes for this condition and discuss possible implications.

The Future of Obsessive-Compulsive Spectrum Disorders: A Research Perspective

Obsessive-compulsive disorder (OCD) sits at the epicenter of a spectrum of related conditions (often referred to as obsessive-compulsive related disorders (OCRD) or obsessive-compulsive spectrum disorders (OCSD)) that can be as disabling as they are varied in presentation. Research in the field now encompasses diverse disciplines ranging from inflammatory mechanisms to computational psychiatry, to neurocognitive endophenotypes to functional imaging to pharmacogenomics to brain stimulation approaches. As these disorders become more clearly elucidated, there is a need to continually re-evaluate the implications of research findings and to incorporate these findings into new treatment approaches that benefit both patients and clinicians. Even the Diagnostic and Statistical Manual of Mental Disorders 5th Edition (DSM-5) is intended to be flexible and to incorporate validated and reliable biomarkers and neuroscience findings as they become available. This concluding chapter highlights just a few areas of study that promise to influence our understanding of the pathophysiology and clinical practice of OCRD. These include patient-centered outcomes research, the study of developmental brain trajectories in spectrum conditions, robot models of OCRDs, goal-directed versus habit-based behaviors, pharmacogenomics, problematic use of the Internet, and digital interventions. For example, digital medicine may become increasingly useful by identifying patients early on in the course of their illness; providing biomarkers to subtype patients; predicting treatment response; serving as a more proximal outcome measure of treatment response; or providing easily accessible and less costly forms of care. In order to address unmet clinical needs in OCRD, it is helpful to take an interdisciplinary perspective, and the work described in this collection of articles is likely to be invaluable in shaping the future of the field.

Recent Developments in the Habit Hypothesis of OCD and Compulsive Disorders

This chapter aims to familiarise the reader with a diverse and fast-growing literature concerning the role that habits play in obsessive-compulsive disorder (OCD). Core concepts will be introduced, including how the balance between habits and a more deliberate form of action selection (goal-directed control) has traditionally been measured and how cross-species translation, neuroscience tools, and computational modelling have been used to build on these basic principles and reveal core mechanisms under study today. Next, the application of these methods to the study of OCD and related disorders will be detailed, converging on a theory that enhanced habit expression, and indeed compulsions in OCD, might arise from deficits in goal-directed control systems. These basic findings will be contextualised in terms of major tide changes in the field, including the shift from categorical disease frameworks to dimensional ones. Mechanistically, recent research concerning how goal-directed deficits arise, perhaps through failures in the construction of a mental model, are discussed along with studies critically evaluating our ability to measure habits in humans, in a laboratory setting. The chapter ends with a nod to the future, focusing on the need for clinically oriented, longitudinal, and intervention-based research that aim to translate what is now a wealth of cross-sectional mechanistic insights to the clinic.

Structural Imaging in OCD

Anatomical imaging in OCD using magnetic resonance imaging (MRI) has been performed since the late 1980s. MRI research was further stimulated with the advent of automated image processing techniques such as voxel-based morphometry (VBM) and surface-based methods (e.g., FreeSurfer) which allow for detailed whole-brain data analyses. Early studies suggesting involvement of corticostriatal circuitry (particularly orbitofrontal cortex and ventral striatum) have been complemented by meta-analyses and pooled analyses indicating additional involvement of posterior brain regions, in particular parietal cortex. Recent large-scale meta-analyses from the ENIGMA consortium have revealed greater pallidum and smaller hippocampus volume in adult OCD, coupled with parietal cortical thinning. Frontal cortical thinning was only observed in medicated patients. Previous reports of symptom dimension-specific alterations were not confirmed. In paediatric OCD, thalamus enlargement has been a consistent finding. Studies investigating white matter volume (VBM) or integrity (using diffusion tensor imaging (DTI)) have shown mixed results, with recent DTI meta-analyses mainly showing involvement of posterior cortical-subcortical tracts in addition to subcortical-prefrontal connections. To which extent these abnormalities are unique to OCD or common to other psychiatric disorders is unclear, as few comparative studies have been performed. Overall, neuroanatomical alterations in OCD appear to be subtle and may vary with time, stressing the need for adequately powered longitudinal studies. Although multivariate approaches using machine learning methodologies have so far been disappointing in distinguishing individual OCD patients from healthy controls, including multimodal data in such analyses may aid in further establishing a neurobiological profile of OCD.

Obsessive-compulsive symptoms in anxiety and depressive disorders: Influence of recent and/or traumatic life events

INTRODUCTION

A high prevalence of obsessive-compulsive symptoms (OCSs) in anxiety-depressive disorders ranging from 30 to 67% has been described.

OBJECTIVE

This study aims to assess the presence and persistence of OCSs in an outpatient sample of subjects with anxiety and depressive disorders, as well as its relationship with recent life events (RLEs) and/or traumatic experiences (TEs).

METHOD

We conducted a prospective, observational, analytical study of 200 subjects with DSM-5 diagnoses of anxiety and/or depression. Participants were included by consecutive sampling and were evaluated at baseline and after 6-12 months (mean 8.5 months) of follow-up. The severity of the symptoms was assessed through the Hamilton Anxiety Scale (HARS) and Hamilton Scale for the evaluation of depression (HRSD-17), and comorbidity was assessed through the International Neuropsychiatric Interview (MINI). The Revised Inventory of Obsessions and Compulsions (OCI-R), the Recent Vital Changes Questionnaire (CVSV), and the Diagnostic Scale for Post-Traumatic Stress (PDS) were also administered.

RESULTS

54% of the sample presented OCSs, and 30.5% presented one or more TEs throughout life. At the baseline visit, the presence of OCSs was associated with the severity of depressive symptoms (p=0.028), the presence of TEs (p<0.01), symptoms of post-traumatic stress disorder (p<0.01) and the number of RLEs (p<0.01). Response rate at follow-up was 38%, and persistence of OCSs was found in 60.5% of patients, independent of depressive or anxious symptoms, but was associated with the number of RLEs (p<0.01).

CONCLUSION

The presence of OCSs in patients with anxiety and depressive disorders is frequent and persistent. Anxious-depressive patients with a history of TEs and RLEs had higher OCS levels. These findings highlight the importance of early detection and the use of therapeutic strategies focused on resilience to stress and trauma.

A dimensional investigation of error-related negativity (ERN) and self-reported psychiatric symptoms

Alterations in error processing are implicated in a range of DSM-defined psychiatric disorders. For instance, obsessive-compulsive disorder (OCD) and generalised anxiety disorder show enhanced electrophysiological responses to errors-i.e. error-related negativity (ERN)-while others like schizophrenia have an attenuated ERN. However, as diagnostic categories in psychiatry are heterogeneous and also highly intercorrelated, the precise mapping of ERN enhancements/impairments is unclear. To address this, we recorded electroencephalograms (EEG) from 196 participants who performed the Flanker task and collected scores on 9 questionnaires assessing psychiatric symptoms to test if a dimensional framework could reveal specific transdiagnostic clinical manifestations of error processing dysfunctions. Contrary to our hypothesis, we found non-significant associations between ERN amplitude and symptom severity of OCD, trait anxiety, depression, social anxiety, impulsivity, eating disorders, alcohol addiction, schizotypy and apathy. A transdiagnostic approach did nothing to improve signal; there were non-significant associations between all three transdiagnostic dimensions (anxious-depression, compulsive behaviour and intrusive thought, and social withdrawal) and ERN magnitude. In these same individuals, we replicated a previously published transdiagnostic association between goal-directed learning and compulsive behaviour and intrusive thought. Possible explanations discussed are (i) that associations between the ERN and psychopathology might be smaller than previously assumed, (ii) that these associations might depend on a greater level of symptom severity than other transdiagnostic cognitive biomarkers, or (iii) that task parameters, such as the ratio of compatible to incompatible trials, might be crucial for ensuring the sensitivity of the ERN to clinical phenomena.

Towards a computational psychiatry of juvenile obsessive-compulsive disorder

Obsessive-Compulsive Disorder (OCD) most often emerges during adolescence, but we know little about the aberrant neural and cognitive developmental mechanisms that underlie its emergence during this critical developmental period. To move towards a computational psychiatry of juvenile OCD, we review studies on the computational, neuropsychological and neural alterations in juvenile OCD and link these findings to the adult OCD and cognitive neuroscience literature. We find consistent difficulties in tasks entailing complex decision making and set shifting, but limited evidence in other areas that are altered in adult OCD, such as habit and confidence formation. Based on these findings, we establish a neurocomputational framework that illustrates how cognition can go awry and lead to symptoms of juvenile OCD. We link these possible aberrant neural processes to neuroimaging findings in juvenile OCD and show that juvenile OCD is mainly characterised by disruptions of complex reasoning systems.

The Necessity of Preventing Obsessive-Compulsive Disorder During the COVID-19 Pandemic

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The roles of online and offline replay in planning

Animals and humans replay neural patterns encoding trajectories through their environment, both whilst they solve decision-making tasks and during rest. Both on-task and off-task replay are believed to contribute to flexible decision making, though how their relative contributions differ remains unclear. We investigated this question by using magnetoencephalography (MEG) to study human subjects while they performed a decision-making task that was designed to reveal the decision algorithms employed. We characterised subjects in terms of how flexibly each adjusted their choices to changes in temporal, spatial and reward structure. The more flexible a subject, the more they replayed trajectories during task performance, and this replay was coupled with re-planning of the encoded trajectories. The less flexible a subject, the more they replayed previously preferred trajectories during rest periods between task epochs. The data suggest that online and offline replay both participate in planning but support distinct decision strategies.

Meta-analysis of neurocognitive deficits in unaffected relatives of obsessive-compulsive disorder (OCD): comparison with healthy controls and patients with OCD

BACKGROUND

Obsessive-compulsive disorder (OCD) has been associated with cognitive deficits, particularly with executive functions. These findings support fronto-striatal dysfunction in OCD. However, it is not certain whether these findings are trait features of OCD. In recent years, a number of studies have investigated cognitive functions in unaffected relatives of OCD (OCDrel) but the findings of these studies are contradictory.

METHODS

A systematic review in Pubmed and Scopus databases was performed until 18 March 2019, to locate the studies comparing cognitive functions of OCDrel with healthy controls and OCD patients (OCDpt). A random-effects meta-analysis was conducted.

RESULTS

Current meta-analysis included 16 studies including 527 OCDrel, 445 OCDpt and 639 healthy controls. Healthy controls overperformed OCDpt in all cognitive domains (d = 0.36-0.86). OCDrel underperformed healthy controls in inhibition (d = 0.58, CI = 0.29-0.86), planning (d = 0.45, CI = 0.28-0.63), decision-making (d = 0.58, CI = 0.19-0.98). OCDrel also had small-sized deficits in set-shifting (d = 0.37, CI = 0.04-0.69) and visual memory (d = 0.28, CI = 0.08-0.49). OCDpt underperformed OCDrel in visual memory (d = 0.45, CI = 0.22-0.67) and set-shifting (d = 0.23, CI = 0.04-0.42).

CONCLUSIONS

Current findings suggest that abnormalities in inhibition, planning/problem solving and reward-based decision-making are shared features of OCDrel and OCDpt and might be trait markers related to vulnerability for developing OCD. Visual memory and set-shifting deficits might potentially be biomarkers of incipient illness or subthreshold OCD presentation among OCDrel. Further exploration of cognitive heterogeneity in OCDrel and investigating the effects of the subtypes of OCD in probands on cognitive impairment in OCDrel are needed.

The Utility of Event-Related Potentials in Clinical Psychology

Event-related potentials (ERPs) are direct measures of brain activity that can be leveraged for clinically meaningful research. They can relate robustly both to continuous measures of individual difference and to categorical diagnoses in ways that clarify similarities and distinctions between apparently related disorders and traits. ERPs can be linked to genetic risk, can act as moderators of developmental trajectories and responses to stress, and can be leveraged to identify those at greater risk for psychopathology, especially when used in combination with other neural and self-report measures. ERPs can inform models of the development of, and risk for, psychopathology. Finally, ERPs can be used as targets for existing and novel interventions and prevention efforts. We provide concrete examples for each of these possibilities by focusing on programmatic research on the error-related negativity and anxiety, and thus show that ERPs are poised to make greater contributions toward the identification, prediction, treatment, and prevention of mental disorders.

The erring brain: Error-related negativity as an endophenotype for OCD-A review and meta-analysis

Obsessive-compulsive disorder (OCD) is a complex and heterogeneous disorder that is associated with high personal and societal costs. Feelings of doubt, worry, and repetitive behavior, key symptoms of OCD, have been linked to hyperactive error signals in the brain. The error-related negativity (ERN) represents a validated marker of error processing in the ERP. Increased ERN amplitudes in OCD have been reported very robustly over the last 20 years. This article integrates results from 38 studies analyzing the ERN in OCD, using a quantitative meta-analysis. Meta-regressions were used to examine potential moderators such as task type, symptom severity, age, and sample size. The meta-analysis reveals a robust increase of ERN in OCD patients compared to healthy participants in response-conflict tasks (SMD -0.55) that is not modulated by symptom severity and age. No increase in ERN in OCD was observed in tasks that do not induce response conflict (SMD -0.10). In addition to the meta-analysis, the current article reviews evidence supporting that increased ERN amplitudes in OCD fulfill central criteria for an endophenotype. Further, the specificity of increased ERN amplitudes for OCD and its suitability as a potential transdiagnostic endophenotype is discussed. Finally, the clinical utility and clinical applications are examined. Overall, the evidence that increased ERN amplitudes represent a promising endophenotype indicating vulnerability for OCD is compelling. Furthermore, alterations in ERN are not limited to OCD and may constitute a transdiagnostic endophenotype. Altered neural error signals might serve as a diagnostic or predictive marker and represent a promising target for interventions.

Checking responses of goal- and sign-trackers are differentially affected by threat in a rodent analog of obsessive-compulsive disorder

In obsessive–compulsive disorder (OCD), functional behaviors such as checking that a door is locked become dysfunctional, maladaptive, and debilitating. However, it is currently unknown how aversive and appetitive motivations interact to produce functional and dysfunctional behavior in OCD. Here we show a double dissociation in the effects of anxiogenic cues and sensitivity to rewarding stimuli on the propensity to develop functional and dysfunctional checking behavior in a rodent analog of OCD, the observing response task (ORT). While anxiogenic manipulations of perceived threat (presentation of threat-associated contextual cues) and actual threat (punishment of incorrect responding on the ORT) enhanced functional checking, dysfunctional checking was unaffected. In contrast, rats that had previously been identified as “sign-trackers” on an autoshaping task—and therefore were highly sensitive to the incentive salience of appetitive environmental cues—selectively showed elevated levels of dysfunctional checking under a range of conditions, but particularly so under conditions of uncertainty. These data indicate that functional and dysfunctional checking are dissociable and supported by aversive and appetitive motivational processes, respectively. While functional checking is modulated by perceived and actual threat, dysfunctional checking recruits appetitive motivational processes, possibly akin to the “incentive habits” that contribute to drug-seeking in addiction.

The ease and sureness of a decision: evidence accumulation of conflict and uncertainty

The likelihood of an outcome (uncertainty or sureness) and the similarity between choices (conflict or ease of a decision) are often critical to decision-making. We often ask ourselves: how likely are we to win or lose? And how different is this option's likelihood from the other? Uncertainty is a characteristic of the stimulus and conflict between stimuli, but these dissociable processes are often confounded. Here, applying a novel hierarchical drift diffusion approach, we study their interaction using a sequential learning task in healthy volunteers and pathological groups characterized by compulsive behaviours, by posing it as an evidence accumulation problem. The variables, Conflict (difficult or easy; difference between reward probabilities of the stimuli) and Uncertainty (low, medium or high; inverse U-shaped probability-uncertainty function) were then used to extract threshold ('a', amount of evidence accumulated before making a decision) and drift rate ('v', information processing speed) parameters. Critically, when a decision was both difficult (high conflict) and uncertain, relative to other conditions, healthy volunteers unexpectedly accumulated less evidence with lower decision thresholds and accuracy rates at chance levels. In contrast, patients with obsessive-compulsive disorder had slower processing speeds during these difficult uncertain decisions; yet, despite this more cautious approach, performed suboptimally with poorer accuracy relative to healthy volunteers below that of chance level. Thus, faced with a difficult uncertain decision, healthy controls are capable of rapid possibly random decisions, displaying almost a willingness to 'walk away', whereas those with obsessive compulsive disorder become more deliberative and cautious but despite appearing to learn the differential contingencies, still perform poorly. These observations might underlie disordered behaviours characterized by pathological uncertainty or doubt despite compulsive checking with impaired performance. In contrast, alcohol-dependent subjects show a different pattern relative to healthy controls with difficulties in adjusting their behavioural patterns with slower drift rates or processing speed despite decisions being easy or low conflict. We emphasize the multidimensional nature of compulsive behaviours and the utility of computational models in detecting subtle underlying processes relative to behavioural measures. These observations have implications for targeted behavioural interventions for specific cognitive impairments across psychiatric disorders.

Transdiagnostic Phenotyping Reveals a Host of Metacognitive Deficits Implicated in Compulsivity

Recent work suggests that obsessive-compulsive disorder (OCD) patients have a breakdown in the relationship between explicit beliefs (i.e. confidence about states) and updates to behaviour. The precise computations underlying this disconnection are unclear because case-control and transdiagnostic studies yield conflicting results. Here, a large online population sample (N = 437) completed a predictive inference task previously studied in the context of OCD. We tested if confidence, and its relationship to action and environmental evidence, were specifically associated with self-reported OCD symptoms or common to an array of psychiatric phenomena. We then investigated if a transdiagnostic approach would reveal a stronger and more specific match between metacognitive deficits and clinical phenotypes. Consistent with prior case-control work, we found that decreases in action-confidence coupling were associated with OCD symptoms, but also 5/8 of the other clinical phenotypes tested (8/8 with no correction applied). This non-specific pattern was explained by a single transdiagnostic symptom dimension characterized by compulsivity that was linked to inflated confidence and several deficits in utilizing evidence to update confidence. These data highlight the importance of metacognitive deficits for our understanding of compulsivity and underscore how transdiagnostic methods may prove a more powerful alternative over studies examining single disorders.

Comparison of the Association Between Goal-Directed Planning and Self-reported Compulsivity vs Obsessive-Compulsive Disorder Diagnosis

IMPORTANCE

Dimensional definitions of transdiagnostic mental health problems have been suggested as an alternative to categorical diagnoses, having the advantage of capturing heterogeneity within diagnostic categories and similarity across them and bridging more naturally psychological and neural substrates.

OBJECTIVE

To examine whether a self-reported compulsivity dimension has a stronger association with goal-directed and related higher-order cognitive deficits compared with a diagnosis of obsessive-compulsive disorder (OCD).

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, patients with OCD and/or generalized anxiety disorder (GAD) from across the United States completed a telephone-based diagnostic interview by a trained rater, internet-based cognitive testing, and self-reported clinical assessments from October 8, 2015, to October 1, 2017. Follow-up data were collected to test for replicability.

MAIN OUTCOMES AND MEASURES

Performance was measured on a test of goal-directed planning and cognitive flexibility (Wisconsin Card Sorting Test [WCST]) and a test of abstract reasoning. Clinical variables included DSM-5 diagnosis of OCD and GAD and 3 psychiatric symptom dimensions (general distress, compulsivity, and obsessionality) derived from a factor analysis.

RESULTS

Of 285 individuals in the analysis (mean [SD] age, 32 [12] years; age range, 18-77 years; 219 [76.8%] female), 111 had OCD; 82, GAD; and 92, OCD and GAD. A diagnosis of OCD was not associated with goal-directed performance compared with GAD at baseline (β [SE], -0.02 [0.02]; P = .18). In contrast, a compulsivity dimension was negatively associated with goal-directed performance (β [SE], -0.05 [0.02]; P = .003). Results for abstract reasoning task and WCST mirrored this pattern; the compulsivity dimension was associated with abstract reasoning (β [SE], 2.99 [0.63]; P < .001) and several indicators of WCST performance (eg, categories completed: β [SE], -0.57 [0.09]; P < .001), whereas OCD diagnosis was not (abstract reasoning: β [SE], 0.39 [0.66]; P = .56; categories completed: β [SE], -0.09 [0.10]; P = .38). Other symptom dimensions relevant to OCD, obsessionality, and general distress had no reliable association with goal-directed performance, WCST, or abstract reasoning. Obsessionality had a positive association with requiring more trials to reach the first category on the WCST at baseline (β [SE], 2.92 [1.39]; P = .04), and general distress was associated with impaired goal-directed performance at baseline (β [SE],-0.04 [0.02]; P = .01). However, unlike the key results of this study, neither survived correction for multiple comparisons or was replicated at follow-up testing.

CONCLUSIONS AND RELEVANCE

Deficits in goal-directed planning in OCD may be more strongly associated with a compulsivity dimension than with OCD diagnosis. This result may have implications for research assessing the association between brain mechanisms and clinical manifestations and for understanding the structure of mental illness.

Punishment has a persistent effect on error-related brain activity in highly anxious individuals twenty-four hours after conditioning

The ability to detect and respond to errors, and to subsequently recruit cognitive control to remediate those errors, is critical to successful adaptation in a changing environment. However, there is also evidence that, for anxious individuals, this error signal is enhanced, highlighting affective and motivational influences on error monitoring. These individual differences arise as a function of both genetic influences and learning experiences. In this study, we examined punishment-based modulation of the error-related negativity (ERN) in high and low anxious individuals across two days. Twenty-two low- and 25 high-anxious participants performed a Flanker task in a standard and punishment condition in three phases (Day one: acquisition and extinction 1, Day two: extinction 2). During the acquisition phase, errors in one condition were punished by a loud noise. This was followed by an immediate extinction phase (extinction 1), during which errors were no longer punished, and an identical extinction phase 24 h later (extinction 2). Only high anxious individuals showed increased ERN amplitudes in the punishment compared to the standard condition. This effect was not modulated by phase and was observed across acquisition and both extinction phases, such that anxious individuals appeared not to learn that the threat value of formerly-punished errors had changed in the course of the experiment. These data suggest that environmental factors (i.e., punishment) can have a persistent effect on the magnitude of the ERN, particularly for anxious individuals. This may point to a pathogenic mechanism linking learning experiences with the development of overactive error-monitoring in anxiety.

Animal models of OCD-relevant processes: an RDoC perspective

Animal models have been invaluable tools in deciphering pathophysiology in many branches of medicine. Their application in the study of complex neuropsychiatric conditions such as obsessive-compulsive disorder (OCD), however, raises vexing interpretative challenges. The Research Domain Criteria (RDoC) approach of identifying dimensions of function and dysfunction that cut across syndromic diagnoses provides one potential path forward. We review some of the domains in the current RDoC matrix that may inform our understanding of patients with obsessions and compulsions, and how work in animal model systems is helping us to understand them. We focus on three specific RDoC constructs that may be particularly informative for our understanding of OCD: potential threat, habit, and cognitive control. In each case we review selected recent studies in animal models and their potential contribution to our understanding of OCD, and suggest directions for future research, informed by the animal studies. Such mechanistic work in animal models, in parallel with clinical studies refining our understanding of the relationship between these dimensional constructs and the symptomatology of particular groups of patients, may over time help us to generate a more comprehensive understanding of the pathogenesis and complexity of obsessions and compulsions.

Verifying Feighner's Hypothesis; Anorexia Nervosa Is Not a Psychiatric Disorder

Mental causation takes explanatory priority over evolutionary biology in most accounts of eating disorders. The evolutionary threat of starvation has produced a brain that assists us in the search for food and mental change emerges as a consequence. The major mental causation hypothesis: anxiety causes eating disorders, has been extensively tested and falsified. The subsidiary hypothesis: anxiety and eating disorders are caused by the same genotype, generates inconsistent results because the phenotypes are not traits, but vary along dimensions. Challenging the mental causation hypothesis in Feighner et al. (1972) noted that anorexic patients are physically hyperactive, hoarding for food, and they are rewarded for maintaining a low body weight. In 1996, Feighner's hypothesis was formalized, relating the patients' behavioral phenotype to the brain mechanisms of reward and attention (Bergh and Södersten, 1996), and in 2002, the hypothesis was clinically verified by training patients how to eat normally, thus improving outcomes (Bergh et al., 2002). Seventeen years later we provide evidence supporting Feighner's hypothesis by demonstrating that in 2012, 20 out of 37 patients who were referred by a psychiatrist, had a psychiatric diagnosis that differed from the diagnosis indicated by the SCID-I. Out of the 174 patients who were admitted in 2012, most through self-referral, there was significant disagreement between the outcomes of the SCID-I interview and the patient's subjective experience of a psychiatric problem in 110 of the cases. In addition, 358 anorexic patients treated to remission scored high on the Comprehensive Psychopathological Rating Scale, but an item response analysis indicated one (unknown) underlying dimension, rather than the three dimensions the scale can dissociate in patients with psychiatric disorders. These results indicate that psychiatric diagnoses, which are reliable and valid in patients with psychiatric disorders, are less well suited for patients with anorexia. The results are in accord with the hypothesis of the present Research Topic, that eating disorders are not always caused by disturbed psychological processes, and support the alternative, clinically relevant hypothesis that the behavioral phenotype of the patients should be addressed directly.

Behavioral and biological markers for predicting compulsive-like drinking in schedule-induced polydipsia

Schedule-induced polydipsia (SIP), characterized by the development of persistent and excessive drinking under intermittent food-reinforcement schedules, is an animal model of compulsive behavior that can differentiate two populations: high drinkers (HD) and low drinkers (LD). The aim of the present study was to identify behavioral and biological markers to predict the vulnerability to developing compulsive-like drinking in SIP. Adult male Wistar rats were first trained in a spatial-discrimination serial reversal-learning task and in a reinforcer devaluation task to measure behavioral flexibility and habit formation, respectively. Subsequently, the rats were tested using the SIP protocol and identified as HD or LD based on their drinking rates. The performance of HD and LD rats in the two previous tasks was then analyzed. Before and after SIP exposure, blood glucose and plasma corticosterone (CORT) levels were measured. Additionally, serum electrolyte levels, including sodium, potassium, and chloride, were analyzed after SIP. HD rats showed higher behavioral inflexibility by exhibiting increased perseverative responses in the reversal-learning task and insensitivity to reinforcer devaluation during extinction under selective satiation. After SIP exposure, HD rats exhibited increased basal plasma CORT levels, indicating that this vulnerable group might have a dysregulation of the HPA axis. Although HD and LD rats had blood glucose levels within normal range, the HD group showed lower levels. The HD group did not exhibit hyponatremia (i.e., reduced serum sodium levels) when compared to LD rats after 20 daily SIP sessions. The results of the present study demonstrated that HD rats exhibit behavioral inflexibility and greater habitual-like behavior before SIP. Moreover, these results highlight the importance of measuring different behavioral and biological markers for predicting the vulnerability to developing compulsivity, and for enhancing the understanding of the pathophysiology of compulsive spectrum disorders.

Increased Fear Memory and Glutamatergic Modulation in Compulsive Drinker Rats Selected by Schedule-Induced Polydipsia

Compulsive behavior is observed in several neuropsychiatric disorders such as obsessive-compulsive disorder (OCD), anxiety, depression, phobia, and schizophrenia. Thus, compulsivity has been proposed as a transdiagnostic symptom with a highly variable pharmacological treatment. Recent evidence shows that glutamate pharmacotherapy may be of benefit in impaired inhibitory control. The purpose of the present study was: first, to test the comorbidity between compulsivity and other neuropsychiatric symptoms on different preclinical behavioral models; second, to assess the therapeutic potential of different glutamate modulators in a preclinical model of compulsivity. Long Evans rats were selected as either high (HD) or low (LD) drinkers corresponding with their water intake in schedule-induced polydipsia (SIP). We assessed compulsivity in LD and HD rats by marble burying test (MBT), depression by forced swimming test (FST), anxiety by elevated plus maze (EPM) and fear behavior by fear conditioning (FC) test. After that, we measured the effects of acute administration (i.p.) of glutamatergic drugs: N-Acetylcysteine (NAC; 25, 50, 100 and 200 mg/kg), memantine (3.1 and 6.2 mg/kg) and lamotrigine (15 and 30 mg/kg) on compulsive drinking on SIP. The results obtained showed a relation between high compulsive drinking on SIP and a higher number of marbles partially buried in MBT, as well as a higher percentage of freezing on the retrieval day of FC test. We did not detect any significant differences between LD and HD rats in FST, nor in EPM. The psychopharmacological study of glutamatergic drugs revealed that memantine and lamotrigine, at all doses tested, decreased compulsive water consumption in HD rats compared to LD rats on SIP. NAC did not produce any significant effect on SIP. These results indicate that the symptom clusters of different forms of compulsivity and phobia might be found in the compulsive phenotype of HD rats selected by SIP. The effects of memantine and lamotrigine in HD rats point towards a dysregulation in the glutamatergic signaling as a possible underlying mechanism in the vulnerability to compulsive behavior on SIP. Further studies on SIP, could help to elucidate the therapeutic role of glutamatergic drugs as a pharmacological strategy on compulsive spectrum disorders.

Error Processing and Inhibitory Control in Obsessive-Compulsive Disorder: A Meta-analysis Using Statistical Parametric Maps

BACKGROUND

Error processing and inhibitory control enable the adjustment of behaviors to meet task demands. Functional magnetic resonance imaging studies report brain activation abnormalities in patients with obsessive-compulsive disorder (OCD) during both processes. However, conclusions are limited by inconsistencies in the literature and small sample sizes. Therefore, the aim here was to perform a meta-analysis of the existing literature using unthresholded statistical maps from previous studies.

METHODS

A voxelwise seed-based d mapping meta-analysis was performed using t-maps from studies comparing patients with OCD and healthy control subjects (HCs) during error processing and inhibitory control. For the error processing analysis, 239 patients with OCD (120 male; 79 medicated) and 229 HCs (129 male) were included, while the inhibitory control analysis included 245 patients with OCD (120 male; 91 medicated) and 239 HCs (135 male).

RESULTS

Patients with OCD, relative to HCs, showed longer inhibitory control reaction time (standardized mean difference = 0.20, p = .03, 95% confidence interval = 0.016, 0.393) and more inhibitory control errors (standardized mean difference = 0.22, p = .02, 95% confidence interval = 0.039, 0.399). In the brain, patients showed hyperactivation in the bilateral dorsal anterior cingulate cortex, supplementary motor area, and pre-supplementary motor area as well as right anterior insula/frontal operculum and anterior lateral prefrontal cortex during error processing but showed hypoactivation during inhibitory control in the rostral and ventral anterior cingulate cortices and bilateral thalamus/caudate, as well as the right anterior insula/frontal operculum, supramarginal gyrus, and medial orbitofrontal cortex (all seed-based d mapping z value >2, p < .001).

CONCLUSIONS

A hyperactive error processing mechanism in conjunction with impairments in implementing inhibitory control may underlie deficits in stopping unwanted compulsive behaviors in the disorder.

Error-related brain activity as a transdiagnostic endophenotype for obsessive-compulsive disorder, anxiety and substance use disorder

BACKGROUND

Increased neural error-signals have been observed in obsessive-compulsive disorder (OCD), anxiety disorders, and inconsistently in depression. Reduced neural error-signals have been observed in substance use disorders (SUD). Thus, alterations in error-monitoring are proposed as a transdiagnostic endophenotype. To strengthen this notion, data from unaffected individuals with a family history for the respective disorders are needed.

METHODS

The error-related negativity (ERN) as a neural indicator of error-monitoring was measured during a flanker task from 117 OCD patients, 50 unaffected first-degree relatives of OCD patients, and 130 healthy comparison participants. Family history information indicated, that 76 healthy controls were free of a family history for psychopathology, whereas the remaining had first-degree relatives with depression (n = 28), anxiety (n = 27), and/or SUD (n = 27).

RESULTS

Increased ERN amplitudes were found in OCD patients and unaffected first-degree relatives of OCD patients. In addition, unaffected first-degree relatives of individuals with anxiety disorders were also characterized by increased ERN amplitudes, whereas relatives of individuals with SUD showed reduced amplitudes.

CONCLUSIONS

Alterations in neural error-signals in unaffected first-degree relatives with a family history of OCD, anxiety, or SUD support the utility of the ERN as a transdiagnostic endophenotype. Reduced neural error-signals may indicate vulnerability for under-controlled behavior and risk for substance use, whereas a harm- or error-avoidant response style and vulnerability for OCD and anxiety appears to be associated with increased ERN. This adds to findings suggesting a common neurobiological substrate across psychiatric disorders involving the anterior cingulate cortex and deficits in cognitive control.

Obsessive-Compulsive Disorder: Puzzles and Prospects

Obsessive-compulsive disorder is a severe and disabling psychiatric disorder that presents several challenges for neuroscience. Recent advances in its genetic and developmental causation, as well as its neuropsychological basis, are reviewed. Hypotheses concerning an imbalance between goal-directed and habitual behavior together with neural correlates in cortico-striatal circuitry are evaluated and contrasted with metacognitive theories. Treatments for obsessive-compulsive disorder (OCD) tend to be of mixed efficacy but include psychological, pharmacological, and surgical approaches, the underlying mechanisms of which are still under debate. Overall, the prospects for new animal models and an integrated understanding of the pathophysiology of OCD are considered in the context of dimensional psychiatry.

Does cognitive-behavioral therapy affect goal-directed planning in obsessive-compulsive disorder?

Cross-sectional studies have reported failures in goal-directed planning in obsessive-compulsive disorder (OCD). It remains unclear whether these deficits confer vulnerability to developing OCD, or are a consequence of symptoms. The present study examined goal-directed learning before and after cognitive behavioral therapy (CBT), using treatment as a tool to reduce symptoms. Eighteen adult OCD patients undergoing 17 sessions of CBT completed an established task of model-based (i.e., goal directed) versus model-free planning as well as measures of OCD and depression before and after treatment. We thus tested whether improvements in goal-directed performance accompany improvements in OCD symptoms or if instead task performance remains stable despite symptom improvement. Results showed prior to treatment, higher OCD severity was associated with greater deficits in model-based planning. OCD severity scores significantly improved from pre- to post-treatment. Inconsistent with the state-view, OCD symptom improvement was not accompanied by improvements in model-based performance. At post-treatment, OCD severity scores were no longer correlated with model-based performance. Together, these data suggest that reducing OCD symptoms with CBT does not affect goal-directed planning. This supports a trait model of the relationship between goal-directed planning and OCD symptoms, such that problems in goal-directed planning may be an OCD risk factor.

Duration of untreated illness and response to SRI treatment in Obsessive-Compulsive Disorder

BACKGROUND

The duration of untreated illness (DUI) is a potentially modifiable parameter associated with worst prognosis in several psychiatric disorders, but poorly investigated in Obsessive-Compulsive Disorder (OCD). Our aims were to estimate the mean DUI in a large sample of individuals with OCD and its impact on response to the first ever adequate SRI treatment.

METHODS

We retrospectively examined records of 251 patients with OCD (SCID-I, DSM-IV) who referred to our Department and were prospectively and naturalistically treated according to International Guidelines. The DUI was defined as the interval between age at onset and age at which patients received their first adequate pharmacological treatment. Response rates were compared in subjects with brief (≤24 months) versus long DUI. Logistic regression models predicting response and 12-week Y-BOCS score were run with DUI (among others) as independent variable.

RESULTS

The mean DUI was 106.19 ± 118.14 months, with a mean interval between onset of the disorder and when patients sought professional help of 82.27 ± 112.30 months. Response rates were significantly reduced in subjects with a long DUI, using both the cut-off of 24 months and the median value of 60 months. Regression analyses confirmed that a long (>24 months) DUI predicts poorer response and higher Y-BOCS scores at 12 weeks.

CONCLUSIONS

Our results, although preliminary, seem to suggest that a longer duration of untreated illness in OCD is associated with poorer outcome in terms of response to SRI treatments. It is imperative to do all the possible to shorten the DUI, both by improving access to mental health services, improving the ability of primary care physicians and mental health professionals to recognize OCD, and disseminate best-practice prescription guidelines.

Effectiveness of imaging genetics analysis to explain degree of depression in Parkinson's disease

Depression is one of the most common and important neuropsychiatric symptoms in Parkinson's disease and often becomes worse as Parkinson's disease progresses. However, the underlying mechanisms of depression in Parkinson's disease are not clear. The aim of our study was to find genetic features related to depression in Parkinson's disease using an imaging genetics approach and to construct an analytical model for predicting the degree of depression in Parkinson's disease. The neuroimaging and genotyping data were obtained from an openly accessible database. We computed imaging features through connectivity analysis derived from tractography of diffusion tensor imaging. The imaging features were used as intermediate phenotypes to identify genetic variants according to the imaging genetics approach. We then constructed a linear regression model using the genetic features from imaging genetics approach to describe clinical scores indicating the degree of depression. As a comparison, we constructed other models using imaging features and genetic features based on references to demonstrate the effectiveness of our imaging genetics model. The models were trained and tested in a five-fold cross-validation. The imaging genetics approach identified several brain regions and genes known to be involved in depression, with the potential to be used as meaningful biomarkers. Our proposed model using imaging genetic features predicted and explained the degree of depression in Parkinson's disease appropriately (adjusted R2 larger than 0.6 over five training folds) and with a lower error and higher correlation than with other models over five test folds.

Dopaminergic drug treatment remediates exaggerated cingulate prediction error responses in obsessive-compulsive disorder

RATIONALE

Patients with obsessive-compulsive disorder (OCD) have been found to show exaggerated error responses and prediction error learning signals in a variety of EEG and fMRI tasks, with data converging on the anterior cingulate cortex as a key locus of dysfunction. Considerable evidence has linked prediction error processing to dopaminergic function.

OBJECTIVE

In this study, we investigate potential dopaminergic dysfunction during reward processing in the context of OCD.

METHODS

We studied OCD patients (n = 18) and controls (n = 18) whilst they learned probabilistic associations between abstract stimuli and monetary rewards in the fMRI scanner involving administration (on separate visits) of a dopamine receptor agonist, pramipexole 0.5 mg; a dopamine receptor antagonist, amisulpride 400 mg; and placebo. We fitted a Q-learning computational model to fMRI prediction error responses; group differences were examined in anterior cingulate and nucleus accumbens regions of interest.

RESULTS

There were no significant group, drug, or interaction effects in the number of correct choices; computational modeling suggested a marginally significant difference in learning rates between groups (p = 0.089, partial ƞ² = 0.1). In the imaging results, there was a significant interaction of group by drug (p = 0.013, partial ƞ² = 0.13). OCD patients showed abnormally strong cingulate signaling of prediction errors during omission of an expected reward, with unexpected reduction by both pramipexole and amisulpride (p = 0.014, partial ƞ² = 0.26, 1-β error probability = 0.94). Exaggerated cingulate prediction error signaling to omitted reward in placebo was related to trait subjective difficulty in self-regulating behavior in OCD.

CONCLUSIONS

Our data support cingulate dysfunction during reward processing in OCD, and bidirectional remediation by dopaminergic modulation, suggesting that exaggerated cingulate error signals in OCD may be of dopaminergic origin. The results help to illuminate the mechanisms through which dopamine receptor antagonists achieve therapeutic benefit in OCD. Further research is needed to disentangle the different functions of dopamine receptor agonists and antagonists during bidirectional modulation of cingulate activation.

Latent traits of impulsivity and compulsivity: toward dimensional psychiatry

BACKGROUND

The concepts of impulsivity and compulsivity are commonly used in psychiatry. Little is known about whether different manifest measures of impulsivity and compulsivity (behavior, personality, and cognition) map onto underlying latent traits; and if so, their inter-relationship.

METHODS

A total of 576 adults were recruited using media advertisements. Psychopathological, personality, and cognitive measures of impulsivity and compulsivity were completed. Confirmatory factor analysis was used to identify the optimal model.

RESULTS

The data were best explained by a two-factor model, corresponding to latent traits of impulsivity and compulsivity, respectively, which were positively correlated with each other. This model was statistically superior to the alternative models of their being one underlying factor ('disinhibition') or two anticorrelated factors. Higher scores on the impulsive and compulsive latent factors were each significantly associated with worse quality of life (both p < 0.0001).

CONCLUSIONS

This study supports the existence of latent functionally impairing dimensional forms of impulsivity and compulsivity, which are positively correlated. Future work should examine the neurobiological and neurochemical underpinnings of these latent traits; and explore whether they can be used as candidate treatment targets. The findings have implications for diagnostic classification systems, suggesting that combining categorical and dimensional approaches may be valuable and clinically relevant.

Do psychoactive drugs have a therapeutic role in compulsivity? Studies on schedule-induced polydipsia

RATIONALE

Clinical studies have shown that some psychoactive recreational drugs have therapeutic applications in anxiety, depression, and schizophrenia. However, to date, there are few studies on the therapeutic potential efficacy of recreational drugs in compulsive neuropsychiatric disorders.

OBJECTIVES

We explored the therapeutic potential of different psychoactive and psychedelic drugs in a preclinical model of compulsive behavior.

METHODS

Outbred male Wistar rats were selected as either high (HD) or low (LD) drinkers according to their behavior in schedule-induced polydipsia (SIP). Subsequently, we assessed the effects of acute administration of scopolamine (0.125, 0.25, and 0.5 mg/kg), methamphetamine (0.25, 0.5, 1.25, and 2.5 mg/kg), ketamine (1.25, 2.5, 5, and 10 mg/kg), cannabidiol (1 and 3 mg/kg), WIN21255-2 (0.5, 075, and 1 mg/kg), and AM404 (0.25 and 0.5 mg/kg) on compulsive drinking in SIP.

RESULTS

Scopolamine reduced dose-dependent compulsive drinking in HD compared with LD rats in SIP. Methamphetamine induced a dose-dependent inverted U-curve effect in both groups, in which lower doses increased and higher doses reduced compulsive drinking in SIP. Ketamine, cannabidiol, WIN21255-2, and AM404 did not have any relevant effects in SIP.

CONCLUSIONS

These data provide new evidence that low doses of scopolamine and intermediate doses of methamphetamine might therapeutically reduce compulsive behaviors and suggest that there is not a direct participation of the endocannabinoid system in compulsive behavior on SIP. The research in the underlying neurochemical mechanisms of these psychoactive drugs might provide an additional insight on new therapeutic targets in compulsive neuropsychiatric disorders.