Local cerebral glucose metabolic rates in obsessive-compulsive disorder. A comparison with rates in unipolar depression and in normal controls

Self-Inflicted Head Injury in Behavioral Variant Frontotemporal Dementia with Compulsive Behaviors: A Case Report

Here we present the case of a 56-year-old right-handed White male who developed osteomyelitis and empyema after repetitive compulsive excoriation rituals. His recent history included profound personality changes, apathy, loss of empathy, limited insight, behavioral agitation, and episodic memory loss. In addition to these progressive behavioral deficits, he had significant difficulties with executive functioning, leading to the loss of his job and inability to independently perform instrumental activities of daily living. Brain MRI showed asymmetric enlargement of the right lateral ventricle and mild asymmetric parenchymal volume loss in the right hippocampus. 18F-FDG PET imaging revealed severe hypometabolism in the right hemisphere. Based on this individual's clinical presentation, reported history, and neuroimaging findings, we concluded that his condition was most consistent with a diagnosis of behavioral variant frontotemporal dementia (bvFTD), rather than another psychiatric diagnosis. This case illustrates the importance of differentiating between bvFTD and other psychiatric disorders, as well as the need for further studies to improve clinicians' ability to do so at earlier stages.

Anatomical mapping of whole-brain monosynaptic inputs to the orbitofrontal cortex

The orbitofrontal cortex (ORB) exhibits a complex structure and diverse functional roles, including emotion regulation, decision-making, and reward processing. Structurally, it comprises three distinct regions: the medial part (ORBm), the ventrolateral part (ORBvl), and the lateral part (ORBl), each with unique functional attributes, such as ORBm's involvement in reward processing, ORBvl's regulation of depression-like behavior, and ORBl's response to aversive stimuli. Dysregulation of the ORB has been implicated in various psychiatric disorders. However, the neurocircuitry underlying the functions and dysfunctions of the ORB remains poorly understood. This study employed recombinant adeno-associated viruses (rAAV) and rabies viruses with glycoprotein deletion (RV-ΔG) to retrogradely trace monosynaptic inputs to three ORB subregions in male C57BL/6J mice. Inputs were quantified across the whole brain using fluorescence imaging and statistical analysis. Results revealed distinct input patterns for each ORB subregion, with significant contributions from the isocortex and thalamus. The ORBm received prominent inputs from the prelimbic area, agranular insular area, and hippocampal field CA1, while the ORBvl received substantial intra-ORB inputs. The ORBl exhibited strong inputs from the somatomotor and somatosensory areas. Thalamic inputs, particularly from the mediodorsal nucleus and submedial nucleus of the thalamus, were widespread across all ORB subregions. These findings provide novel insights into the functional connectivity of ORB subregions and their roles in neural circuit mechanisms underlying behavior and psychiatric disorders.

Psychedelics for the Treatment of Obsessive-Compulsive Disorder: Efficacy and Proposed Mechanisms

Psychedelics are emerging as potential treatments for a range of mental health conditions, including anxiety and depression, treatment-resistant depression, and substance use disorders. Recent studies have also suggested that the psychedelic psilocybin may be able to treat obsessive-compulsive disorder (OCD). Since the 1960s, case studies have reported improvements to obsessive and compulsive behaviors in patients taking psychedelics recreationally. The effects of psilocybin were then systematically assessed in a small, open-label trial in 2006, which found that psilocybin significantly reduced the symptoms of OCD. Reduced compulsive behaviors have also been seen in rodent models of OCD after administration of psilocybin. Nonetheless, the mechanisms underlying the effects of psychedelics for OCD are unclear, with hypotheses including their acute pharmacological effects, changes in neuroplasticity and resting state neural networks, and their psychological effects. This review will evaluate the evidence supporting the theory that psychedelics can be used for the treatment of OCD, as well as the data regarding claims about their mechanisms. It will also discuss issues with the current evidence and the ongoing trials of psilocybin that aim to address these knowledge gaps.

Does compulsion explain addiction?

One of the leading drug addiction theories states that habits and the underlying neural process of a ventral to dorsal striatal shift are the building blocks of compulsive drug-seeking behaviour and that compulsion is the maladaptive persistence of responding despite adverse consequences. Here we discuss that compulsive behaviour as defined primarily from the perspective of animal experimentation falls short of the clinical phenomena and their neurobiological correlates. Thus for the human condition, the concept of compulsive habbits should be critically addressed and potentially revised.

Persistent enhancement of basolateral amygdala-dorsomedial striatum synapses causes compulsive-like behaviors in mice

Compulsive behaviors are observed in a range of psychiatric disorders, however the neural substrates underlying the behaviors are not clearly defined. Here we show that the basolateral amygdala-dorsomedial striatum (BLA-DMS) circuit activation leads to the manifestation of compulsive-like behaviors. We revealed that the BLA neurons projecting to the DMS, mainly onto dopamine D1 receptor-expressing neurons, largely overlap with the neuronal population that responds to aversive predator stress, a widely used anxiogenic stressor. Specific optogenetic activation of the BLA-DMS circuit induced a strong anxiety response followed by compulsive grooming. Furthermore, we developed a mouse model for compulsivity displaying a wide spectrum of compulsive-like behaviors by chronically activating the BLA-DMS circuit. In these mice, persistent molecular changes at the BLA-DMS synapses observed were causally related to the compulsive-like phenotypes. Together, our study demonstrates the involvement of the BLA-DMS circuit in the emergence of enduring compulsive-like behaviors via its persistent synaptic changes.

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.

Dissecting Psychiatric Heterogeneity and Comorbidity with Core Region-Based Machine Learning

Machine learning approaches are increasingly being applied to neuroimaging data from patients with psychiatric disorders to extract brain-based features for diagnosis and prognosis. The goal of this review is to discuss recent practices for evaluating machine learning applications to obsessive-compulsive and related disorders and to advance a novel strategy of building machine learning models based on a set of core brain regions for better performance, interpretability, and generalizability. Specifically, we argue that a core set of co-altered brain regions (namely 'core regions') comprising areas central to the underlying psychopathology enables the efficient construction of a predictive model to identify distinct symptom dimensions/clusters in individual patients. Hypothesis-driven and data-driven approaches are further introduced showing how core regions are identified from the entire brain. We demonstrate a broadly applicable roadmap for leveraging this core set-based strategy to accelerate the pursuit of neuroimaging-based markers for diagnosis and prognosis in a variety of psychiatric disorders.

Considerations for the treatment of obsessive-compulsive disorder in patients who have comorbid major depression

INTRODUCTION

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder that affects a significant number of individuals worldwide. Major depressive disorder (MDD) is among the most common comorbidities reported in people with OCD. The emergence of MDD in individuals with OCD can be attributed to the increased severity of OCD symptoms and their profound impact on daily functioning. Depressive symptoms can also modify the course of OCD.

AREAS COVERED

In this review, the authors explore potential shared neurobiological mechanisms that may underlie both OCD and MDD, such as disturbed sleep patterns, immunological dysregulations, and neuroendocrine changes. Furthermore, they address the challenges clinicians face when managing comorbid OCD and MDD. The authors also discuss a range of treatment options for OCD associated with MDD, including augmentation strategies for serotonin reuptake inhibitors (e.g. aripiprazole), psychotherapy (especially CBT/EPR), transcranial magnetic stimulation (TMS), electroconvulsive therapy (ECT), and deep brain stimulation (DBS).

EXPERT OPINION

Although there is no 'rule of thumb' or universally acceptable strategy in the treatment of OCD comorbid with MDD, many clinicians, including the authors, tend to adopt a unique transdiagnostic approach to the treatment of OCD and related disorders, focusing on strategies known to be effective across diagnoses. Nevertheless, the existing 'cisdiagnostic approaches' still retain importance, i.e. specific therapeutic strategies tailored for more severe forms of individual disorders.

Obsessions And Compulsions: A Lifespan Perspective

Freud traced the origin of the obsessional neurosis, which he considered a model condition for psychoanalytic inquiry, to a fixation in the anal phase of psychosexual development. Although many analysts have raised doubts about his account, and while the Sullivanian and Lacanian traditions have proposed alternatives, no approach has accounted for what Freud observed as the dizzying variety of obsessive presentations, which seem to defy a singular explanation. The broader research community has moved on, meanwhile, to genetic, neurological, and cognitive-behavioral explanations of what we now call obsessive-compulsive disorder. I argue that we can best account for the variety of obsessive presentations and meaningfully contribute to this interdisciplinary dialogue by framing obsessive-compulsive symptoms as the result of a disorder of volition, an exaggerated sense of willpower, not tied to any one developmental phase or bodily zone. Such a disorder evolves through the lifespan processes of introjection, identification, and repudiation in relation to an anxious/critical parent or an unpredictable environment. I trace these processes through three major developmental milestones. The implication is that, by looking in depth at how the obsessive person internalizes relationships, psychoanalysis can make a unique contribution to a conversation beyond its own borders.

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.

Near-infrared spectroscopy in child and adolescent neurodevelopmental disorders

Near-infrared spectroscopy (NIRS) is a noninvasive optical technique that uses the near-infrared spectrum for functional neuroimaging by measuring oxygenation and hemodynamic changes in the cerebral cortex. The advantages of NIRS include its portability and ease of application, which allows for testing with the subject in natural positions, such as sitting or standing. Since 1994, NIRS has been increasingly used to conduct functional activation studies on different psychiatric disorders, most prominently schizophrenia, depression, bipolar disorder, and neurodevelopmental disorders. However, limited information on its use among child and adolescent patients is available. We herein review recent findings obtained using NIRS measurements of the brain during cognitive tasks in neurodevelopmental disorders, such as autism spectrum disorder, attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, and Tourette's disorder. This will facilitate evaluations of the causation and treatment of prefrontal cortex dysfunctions.

Use of right orbitofrontal repetitive transcranial magnetic stimulation (rTMS) augmentation for treatment-refractory obsessive-compulsive disorder with comorbid major depressive disorder

We examined the safety and efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) of the right orbitofrontal cortex (OFC) in patients with refractory obsessive-compulsive disorder (OCD) and comorbid Major Depressive Disorder. All participants (n = 26) received excitatory stimulation of the left dorsolateral prefrontal cortex followed by inhibitory stimulation of bilateral supplementary motor area for 10 sessions. In 18 patients with poor early OCD response, treatment was augmented with OFC inhibitory stimulation after the tenth treatment session. Augmentation with OFC stimulation was well-tolerated, and associated with further alleviation of both OCD and depression symptoms, particularly in individuals with more severe illnesses.

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.

Explicit knowledge of task structure is a primary determinant of human model-based action

Explicit information obtained through instruction profoundly shapes human choice behaviour. However, this has been studied in computationally simple tasks, and it is unknown how model-based and model-free systems, respectively generating goal-directed and habitual actions, are affected by the absence or presence of instructions. We assessed behaviour in a variant of a computationally more complex decision-making task, before and after providing information about task structure, both in healthy volunteers and in individuals suffering from obsessive-compulsive or other disorders. Initial behaviour was model-free, with rewards directly reinforcing preceding actions. Model-based control, employing predictions of states resulting from each action, emerged with experience in a minority of participants, and less in those with obsessive-compulsive disorder. Providing task structure information strongly increased model-based control, similarly across all groups. Thus, in humans, explicit task structural knowledge is a primary determinant of model-based reinforcement learning and is most readily acquired from instruction rather than experience.

Developmental impact of glutamate transporter overexpression on dopaminergic neuron activity and stereotypic behavior

Obsessive-compulsive disorder (OCD) is a disabling condition that often begins in childhood. Genetic studies in OCD have pointed to SLC1A1, which encodes the neuronal glutamate transporter EAAT3, with evidence suggesting that increased expression contributes to risk. In mice, midbrain Slc1a1 expression supports repetitive behavior in response to dopaminergic agonists, aligning with neuroimaging and pharmacologic challenge studies that have implicated the dopaminergic system in OCD. These findings suggest that Slc1a1 may contribute to compulsive behavior through altered dopaminergic transmission; however, this theory has not been mechanistically tested. To examine the developmental impact of Slc1a1 overexpression on compulsive-like behaviors, we, therefore, generated a novel mouse model to perform targeted, reversible overexpression of Slc1a1 in dopaminergic neurons. Mice with life-long overexpression of Slc1a1 showed a significant increase in amphetamine (AMPH)-induced stereotypy and hyperlocomotion. Single-unit recordings demonstrated that Slc1a1 overexpression was associated with increased firing of dopaminergic neurons. Furthermore, dLight1.1 fiber photometry showed that these behavioral abnormalities were associated with increased dorsal striatum dopamine release. In contrast, no impact of overexpression was observed on anxiety-like behaviors or SKF-38393-induced grooming. Importantly, overexpression solely in adulthood failed to recapitulate these behavioral phenotypes, suggesting that overexpression during development is necessary to generate AMPH-induced phenotypes. However, doxycycline-induced reversal of Slc1a1/EAAT3 overexpression in adulthood normalized both the increased dopaminergic firing and AMPH-induced responses. These data indicate that the pathologic effects of Slc1a1/EAAT3 overexpression on dopaminergic neurotransmission and AMPH-induced stereotyped behavior are developmentally mediated, and support normalization of EAAT3 activity as a potential treatment target for basal ganglia-mediated repetitive behaviors.

Accumulation of evidence during decision making in OCD patients

Decision-making often entails the accumulation of evidence. Previous studies suggested that people with obsessive-compulsive disorder (OCD) process decision-making differently from healthy controls. Both their compulsive behavior and obsessive thoughts may influence the evidence accumulation process, yet the previous studies disagreed on the reason. To address this question, we employed a probabilistic reasoning task in which subjects made two alternative forced choices by viewing a series of visual stimuli. These stimuli carried probabilistic information toward the choices. While the OCD patients achieved similar accuracy to the control, they took longer time and accumulated more evidence, especially in difficult trials in which the evidence strength was low. We further modeled the subjects' decision making as a leaky drifting diffusion process toward two collapsing bounds. The control group showed a higher drifting rate than the OCD group, indicating that the OCD group was less sensitive to evidence. Together, these results demonstrated that the OCD patients were less efficient than the control at transforming sensory information into evidence. However, their evidence accumulation was comparable to the healthy control, and they compensated for their decision-making accuracy with longer reaction times.

The prefrontal cortex and OCD

Obsessive Compulsive Disorder (OCD) is a highly prevalent and severe neuropsychiatric disorder, with an incidence of 1.5-3% worldwide. However, despite the clear public health burden of OCD and relatively well-defined symptom criteria, effective treatments are still limited, spotlighting the need for investigation of the neural substrates of the disorder. Human neuroimaging studies have consistently highlighted abnormal activity patterns in prefrontal cortex (PFC) regions and connected circuits in OCD during both symptom provocation and performance of neurocognitive tasks. Because of recent technical advances, these findings can now be leveraged to develop novel targeted interventions. Here we will highlight current theories regarding the role of the prefrontal cortex in the generation of OCD symptoms, discuss ways in which this knowledge can be used to improve treatments for this often disabling illness, and lay out challenges in the field for future study.

A selective serotonin reuptake inhibitor ameliorates obsessive-compulsive disorder-like perseverative behavior by attenuating 5-HT2C receptor signaling in the orbitofrontal cortex

Perseveration is a characteristic of patients with obsessive-compulsive disorder (OCD). Clinically, neuronal activity in the lateral orbitofrontal cortex (OFC) is increased in OCD patients. Successful treatment with selective serotonin reuptake inhibitors (SSRIs) reduces activity in the lateral OFC of OCD patients, but the precise mechanisms underlying this effect are unclear. Previously, we reported that repeated injection of the dopamine D₂ receptor agonist quinpirole (QNP) resulted in OCD-like deficits, including perseveration in a reversal learning task. QNP-treated mice showed hyperactivity in lateral OFC pyramidal neurons. The present study demonstrated that 4-week administration of an SSRI increased the rate of correct choice in a reversal learning task. Using the electrophysiological approach, we revealed that an SSRI decreased the activity of lateral OFC pyramidal neurons in QNP-treated mice by potentiating inhibitory inputs. The 4-week administration of an SSRI inhibited the potentiation of neuronal activity induced by a 5-HT_2C receptor agonist. Additionally, both 4-week administration of SSRI and acute application of 5-HT_2C receptor antagonist prevented the QNP-induced potentiation of inhibitory inputs to fast-spiking interneurons in the lateral OFC. Administration of a 5-HT_2C receptor antagonist to mice for 4 days increased the rate of correct choice in a reversal learning task. Collectively, these results indicate that chronic SSRI ameliorated perseverative behavior in QNP-treated mice by modulating inhibitory inputs in the lateral OFC. Short-term 5-HT_2C receptor blockade also ameliorated QNP-induced behavioral and neurological abnormalities by, at least in part, a common mechanism with chronic SSRI.

Distinct Patterns of Abnormal Lateral Orbitofrontal Cortex Activity During Compulsive Grooming and Reversal Learning Normalize After Fluoxetine

BACKGROUND

Patients with obsessive-compulsive disorder (OCD) display disrupted performance and abnormal lateral orbitofrontal cortex (LOFC) activity during reversal learning tasks. However, it is unknown whether compulsions and reversal learning deficits share a common neural substrate. To answer this question, we measured neural activity with in vivo calcium imaging in LOFC during compulsive grooming and reversal learning before and after fluoxetine treatment.

METHODS

Sapap3 knockout (KO) mice were used as a model for OCD-relevant behaviors. Sapap3 KOs and control littermates were injected with a virus encoding GCaMP6f and implanted with gradient-index lenses to visualize LOFC activity using miniature microscopes. Grooming, reversal learning, and neural activity were measured pre- and post-fluoxetine treatment (18 mg/kg, 4 weeks).

RESULTS

Baseline compulsive grooming and reversal learning impairments in KOs improved after fluoxetine treatment. In addition, KOs displayed distinct patterns of abnormal LOFC activity during grooming and reversal learning, both of which normalized after fluoxetine. Finally, reversal learning-associated neurons were distributed randomly among grooming-associated neurons (i.e., overlap is what would be expected by chance).

CONCLUSIONS

In OCD, LOFC is disrupted during both compulsive behaviors and reversal learning, but whether these behaviors share common neural underpinnings is unknown. We found that LOFC plays distinct roles in compulsive grooming and impaired reversal learning and their improvement with fluoxetine. These findings suggest that LOFC plays separate roles in pathophysiology and treatment of different perseverative behaviors in OCD.

The Role of Stress in Obsessive-Compulsive Disorder: A Narrative Review

Obsessive-compulsive disorder (OCD) has a worldwide prevalence of 2%-3%. Characterized by the presence of either one or two core symptoms-obsessions and compulsions-it generally runs a chronic course and may cause serious functional impairment. Though previously thought to be of psychogenic origin, the pathophysiology of OCD is now understood to be more complex. A multitude of environmental factors have been shown to contribute to the development of OCD, including infection, neonatal complications, childhood trauma, occurrence of stressful events, and brain injury. It has also been proposed that genetic vulnerability may play a role in OCD pathology, although candidate genes have yet to be identified. Likewise, although it is widely accepted that stress plays a role in OCD pathophysiology, the mechanisms remain unclear. Observations from the clinics indicate that stress may serve as both a triggering and aggravating factor, meaning it can prompt symptoms to appear while also contributing to their exacerbation. Additionally, dysfunction of the hypothalamic-pituitary-adrenal axis and impaired stress response have been identified in OCD patients. In this review, we analyze the role of stress in the pathophysiology of OCD, complemented by relevant findings from recent animal studies.

Reduced Axon Calibre in the Associative Striatum of the Sapap3 Knockout Mouse

Pathological repetitive behaviours are a common feature of various neuropsychiatric disorders, including compulsions in obsessive-compulsive disorder or tics in Gilles de la Tourette syndrome. Clinical research suggests that compulsive-like symptoms are related to associative cortico-striatal dysfunctions, and tic-like symptoms to sensorimotor cortico-striatal dysfunctions. The Sapap3 knockout mouse (Sapap3-KO), the current reference model to study such repetitive behaviours, presents both associative as well as sensorimotor cortico-striatal dysfunctions. Previous findings point to deficits in both macro-, as well as micro-circuitry, both of which can be affected by neuronal structural changes. However, to date, structural connectivity has not been analysed. Hence, in the present study, we conducted a comprehensive structural characterisation of both associative and sensorimotor striatum as well as major cortical areas connecting onto these regions. Besides a thorough immunofluorescence study on oligodendrocytes, we applied AxonDeepSeg, an open source software, to automatically segment and characterise myelin thickness and axon area. We found that axon calibre, the main contributor to changes in conduction speed, is specifically reduced in the associative striatum of the Sapap3-KO mouse; myelination per se seems unaffected in associative and sensorimotor cortico-striatal circuits.

Pharmacotherapy for Neuropsychiatric Symptoms in Frontotemporal Dementia

Despite significant progress in the understanding of the frontotemporal dementias (FTDs), there remains no disease-modifying treatment for these conditions, and limited effective symptomatic treatment. Behavioural variant frontotemporal dementia (bvFTD) is the most common FTD syndrome, and is characterized by severe impairments in behaviour, personality and cognition. Neuropsychiatric symptoms are common features of bvFTD but are present in the other FTD syndromes. Current treatment strategies therefore focus on ameliorating the neuropsychiatric features. Here we review the rationale for current treatments related to each of the main neuropsychiatric symptoms forming the diagnostic criteria for bvFTD relevant to all FTD subtypes, and two additional symptoms not currently part of the diagnostic criteria: lack of insight and psychosis. Given the paucity of effective treatments for these symptoms, we highlight how contributing mechanisms delineated in cognitive neuroscience may inform future approaches to clinical trials and more precise symptomatic treatments for FTDs.

Cerebral perfusion changes in chronic dizziness: A single-photon emission computed tomography study

Background and purpose

Dizziness may persist even after the causative vestibular imbalance subsides. Although the precise mechanism of chronic dizziness is unknown, various cerebral activity changes associated with it have been reported. To understand its mechanism in the absence of the causative vestibular imbalance, we compared cerebral changes in chronic dizziness with and without persistent vestibular imbalance.

Methods

Between September 2014 and March 2020, we examined regional cerebral blood flow (rCBF) in 12 patients having chronic post-lateral medullary infarction dizziness with persistent brainstem vestibular imbalance and 23 patients having chronic dizziness without currently active vestibular imbalance using single-photon emission computed tomography (SPECT) with 99m Technetium-ethyl cysteinate dimer. Further, we analyzed the SPECT images using a voxel-based group comparison.

Results

We observed a decreased rCBF in the occipital lobe and increased rCBF in the medial and inferior parts of the temporal lobe in patients having chronic dizziness with and without active vestibular imbalance compared to healthy controls. However, only patients having chronic dizziness without active vestibular imbalance exhibited increased rCBF in the frontal lobe, including the orbitofrontal cortex.

Conclusion

This is the first study to highlight the difference in rCBF changes between patients having chronic dizziness with and without active vestibular imbalance. Decreased occipital lobe activity and increased medial and inferior temporal lobe activity may be related to keeping dizziness perception triggered regardless of the presence or absence of active vestibular imbalance, whereas increased frontal lobe activity may explain the dizziness background to persist after the disappearance of vestibular imbalance.

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Dizziness may persist even when the causative vestibular imbalance (VI) subsided.

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Changes in cerebral activity are associated with chronic dizziness (CD).

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We compared cerebral activity changes in CD patients with and without VI.

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Regional cerebral blood flow differs in CD patients with and without VI.

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Cerebral activity changes either can be associated with CD or can trigger CD.

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

Obsessive-compulsive disorder (OCD) affects approximately one person in 40 and causes substantial suffering. Evidence-based treatments can benefit many; however, optimal treatment can be difficult to access. Diagnosis is frequently delayed, and pharmacological and psychotherapeutic interventions often fail to follow evidence-based guidelines. To ameliorate this distressing situation, the International OCD Accreditation Task Force of the Canadian Institute for Obsessive-Compulsive Disorders has developed knowledge and competency standards for specialized treatments for OCD through the lifespan. These are foundational to evidence-based practice and will form the basis for upcoming ATF development of certification/accreditation programs. Here, we present specialty standards for the pharmacological treatment of adult OCD. We emphasize the importance of integrating pharmacotherapy with clear diagnosis, appreciation of complicating factors, and evidence-based cognitive behavioral therapy. Clear evidence exists to inform first- and second-line pharmacological treatments. In disease refractory to these initial efforts, multiple strategies have been investigated, but the evidence is more equivocal. These standards summarize this limited evidence to give the specialist practitioner a solid basis on which to make difficult decisions in complex cases. It is hoped that further research will lead to development of a clear, multi-step treatment algorithm to support each step in clinical decision-making.

NOX1/NADPH Oxidase Promotes Synaptic Facilitation Induced by Repeated D2 Receptor Stimulation: Involvement in Behavioral Repetition

Repetitive behavior is a widely observed neuropsychiatric symptom. Abnormal dopaminergic signaling in the striatum is one of the factors associated with behavioral repetition; however, the molecular mechanisms underlying the induction of repetitive behavior remain unclear. Here, we demonstrated that the NOX1 isoform of the superoxide-producing enzyme NADPH oxidase regulated repetitive behavior in mice by facilitating excitatory synaptic inputs in the central striatum (CS). In male C57Bl/6J mice, repeated stimulation of D2 receptors induced abnormal behavioral repetition and perseverative behavior. Nox1 deficiency or acute pharmacological inhibition of NOX1 significantly shortened repeated D2 receptor stimulation-induced repetitive behavior without affecting motor responses to a single D2 receptor stimulation. Among brain regions, Nox1 showed enriched expression in the striatum, and repeated dopamine D2 receptor stimulation further increased Nox1 expression levels in the CS, but not in the dorsal striatum. Electrophysiological analyses revealed that repeated D2 receptor stimulation facilitated excitatory inputs in the CS indirect pathway medium spiny neurons (iMSNs), and this effect was suppressed by the genetic deletion or pharmacological inhibition of NOX1. Nox1 deficiency potentiated protein tyrosine phosphatase activity and attenuated the accumulation of activated Src kinase, which is required for the synaptic potentiation in CS iMSNs. Inhibition of NOX1 or β-arrestin in the CS was sufficient to ameliorate repetitive behavior. Striatal-specific Nox1 knockdown also ameliorated repetitive and perseverative behavior. Collectively, these results indicate that NOX1 acts as an enhancer of synaptic facilitation in CS iMSNs and plays a key role in the molecular link between abnormal dopamine signaling and behavioral repetition and perseveration.SIGNIFICANCE STATEMENT Behavioral repetition is a form of compulsivity, which is one of the core symptoms of psychiatric disorders, such as obsessive-compulsive disorder. Perseveration is also a hallmark of such disorders. Both clinical and animal studies suggest important roles of abnormal dopaminergic signaling and striatal hyperactivity in compulsivity; however, the precise molecular link between them remains unclear. Here, we demonstrated the contribution of NOX1 to behavioral repetition induced by repeated stimulation of D2 receptors. Repeated stimulation of D2 receptors upregulated Nox1 mRNA in a striatal subregion-specific manner. The upregulated NOX1 promoted striatal synaptic facilitation in iMSNs by enhancing phosphorylation signaling. These results provide a novel mechanism for D2 receptor-mediated excitatory synaptic facilitation and indicate the therapeutic potential of NOX1 inhibition in compulsivity.

Transcriptome alterations are enriched for synapse-associated genes in the striatum of subjects with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a chronic and severe psychiatric disorder for which effective treatment options are limited. Structural and functional neuroimaging studies have consistently implicated the orbitofrontal cortex (OFC) and striatum in the pathophysiology of the disorder. Recent genetic evidence points to involvement of components of the excitatory synapse in the etiology of OCD. However, the transcriptional alterations that could link genetic risk to known structural and functional abnormalities remain mostly unknown. To assess potential transcriptional changes in the OFC and two striatal regions (caudate nucleus and nucleus accumbens) of OCD subjects relative to unaffected comparison subjects, we sequenced messenger RNA transcripts from these brain regions. In a joint analysis of all three regions, 904 transcripts were differentially expressed between 7 OCD versus 8 unaffected comparison subjects. Region-specific analyses highlighted a smaller number of differences, which concentrated in caudate and nucleus accumbens. Pathway analyses of the 904 differentially expressed transcripts showed enrichment for genes involved in synaptic signaling, with these synapse-associated genes displaying lower expression in OCD subjects relative to unaffected comparison subjects. Finally, we estimated that cell type fractions of medium spiny neurons were lower whereas vascular cells and astrocyte fractions were higher in tissue of OCD subjects. Together, these data provide the first unbiased examination of differentially expressed transcripts in both OFC and striatum of OCD subjects. These transcripts encoded synaptic proteins more often than expected by chance, and thus implicate the synapse as a vulnerable molecular compartment for OCD.

Functional Brain Imaging and OCD

In the last 20 years, functional magnetic resonance imaging (fMRI) has been extensively used to investigate system-level abnormalities in the brain of patients with obsessive-compulsive disorder (OCD). In this chapter, we start by reviewing the studies assessing regional brain differences between patients with OCD and healthy controls in task-based fMRI. Specifically, we review studies on executive functioning and emotional processing, protocols in which these patients have been described to show alterations at the behavioral level, as well as research using symptom provocation protocols. Next, we review studies on brain connectivity alterations, focusing on resting-state studies evaluating disruptions in fronto-subcortical functional connectivity and in cortical networks. Likewise, we also review research on effective connectivity, which, different from functional connectivity, allows for ascertaining the directionality of inter-regional connectivity alterations. We conclude by reviewing the most significant findings on a topic of translational impact, such as the use of different fMRI measurements to predict response across a variety of treatment approaches. Overall, results suggest that there exists a pattern of regions, involving, but not limited to, different nodes of the cortico-striatal-thalamo-cortical circuits, showing robust evidence of functional alteration across studies, although the nature of the alterations critically depends on the specific tasks and their particular demands. Moreover, such findings have been, to date, poorly translated into clinical practice. It is suggested that this may be partially accounted for by the difficulty to integrate into a common framework results obtained under a wide variety of analysis approaches.

Neurocircuitry of Deep Brain Stimulation for Obsessive-Compulsive Disorder as Revealed by Tractography: A Systematic Review

Objective: Deep brain stimulation (DBS) was proposed in 1999 to treat refractory obsessive-compulsive disorder (OCD). Despite the accumulated experience over more than two decades, 30-40% of patients fail to respond to this procedure. One potential reason to explain why some patients do not improve in the postoperative period is that DBS might not have engaged structural therapeutic networks that are crucial to a favorable outcome in non-responders. This article reviews magnetic resonance imaging diffusion studies (DTI-MRI), analyzing neural networks likely modulated by DBS in OCD patients and their corresponding clinical outcome. Methods: We used a systematic review process to search for studies published from 2005 to 2020 in six electronic databases. Search terms included obsessive-compulsive disorder, deep brain stimulation, diffusion-weighted imaging, diffusion tensor imaging, diffusion tractography, tractography, connectome, diffusion analyses, and white matter. No restriction was made concerning the surgical target, DTI-MRI technique and the method of data processing. Results: Eight studies published in the last 15 years were fully assessed. Most of them used 3 Tesla DTI-MRI, and different methods of data acquisition and processing. There was no consensus on potential structures and networks underlying DBS effects. Most studies stimulated the ventral anterior limb of the internal capsule (ALIC)/nucleus accumbens. However, the contribution of different white matter pathways that run through the ALIC for the effects of DBS remains elusive. Moreover, the improvement of cognitive and affective symptoms in OCD patients probably relies on electric modulation of distinct networks. Conclusion: Though, tractography is a valuable tool to understand neural circuits, the effects of modulating different fiber tracts in OCD are still unclear. Future advances on image acquisition and data processing and a larger number of studies are still required for the understanding of the role of tractography-based targeting and to clarify the importance of different tracts for the mechanisms of DBS.

The anterior limb of the internal capsule: Anatomy, function, and dysfunction

The last two decades have seen a re-emergence of neurosurgery for severe, refractory psychiatric diseases, largely due to the advent of more precise and safe operative techniques. Nevertheless, the optimal targets for these surgeries remain a matter of debate, and are often grandfathered from experiences in the late 20th century. To better explore the rationale for one target in particular - the anterior limb of the internal capsule (ALIC) - we comprehensively reviewed all available literature on its role in the pathophysiology and treatment of mental illness. We first provide an overview of its functional anatomy, followed by a discussion on its role in several prevalent psychiatric diseases. Given its structural integration into the limbic system and involvement in a number of cognitive and emotional processes, the ALIC is a robust target for surgical treatment of refractory psychiatric diseases. The advent of novel neuroimaging techniques, coupled with image-guided therapeutics and neuromodulatory treatments, will continue to enable study on the ALIC in mental illness.

Striatum-Mediated Deficits in Stimulus-Response Learning and Decision-Making in OCD

Obsessive compulsive disorder (OCD) is a prevalent psychiatric disorder characterized by obsessions and compulsions. Studies investigating symptomatology and cognitive deficits in OCD frequently implicate the striatum. The aim of this study was to explore striatum-mediated cognitive deficits in patients with OCD as they complete a stimulus-response learning task previously shown to differentially rely on the dorsal (DS) and ventral striatum (VS). We hypothesized that patients with OCD will show both impaired decision-making and learning, coupled with reduced task-relevant activity in DS and VS, respectively, compared to healthy controls. We found that patients with OCD (n = 14) exhibited decision-making deficits and learned associations slower compared to healthy age-matched controls (n = 16). Along with these behavioral deficits, OCD patients had reduced task-relevant activity in DS and VS, compared to controls. This study reveals that responses in DS and VS are altered in OCD, and sheds light on the cognitive deficits and symptoms experienced by patients with OCD.

Impaired instrumental reversal learning is associated with increased medial prefrontal cortex activity in Sapap3 knockout mouse model of compulsive behavior

Convergent functional neuroimaging findings implicate hyperactivity across the prefrontal cortex (PFC) and striatum in the neuropathology of obsessive compulsive disorder (OCD). The impact of cortico-striatal circuit hyperactivity on executive functions subserved by these circuits is unclear, because impaired recruitment of PFC has also been observed in OCD patients during paradigms assessing cognitive flexibility. To investigate the relationship between cortico-striatal circuit disturbances and cognitive functioning relevant to OCD, Sapap3 knockout mice (KOs) and littermate controls were tested in an instrumental reversal-learning paradigm to assess cognitive flexibility. Cortical and striatal activation associated with reversal learning was assessed via quantitative analysis of expression of the immediate early gene cFos and generalized linear mixed-effects models. Sapap3-KOs displayed heterogeneous reversal-learning performance, with almost half (n = 13/28) failing to acquire the reversed contingency, while the other 15/28 had similar acquisition as controls. Notably, reversal impairments were not correlated with compulsive grooming severity. cFos analysis revealed that reversal performance declined as medial PFC (mPFC) activity increased in Sapap3-KOs. No such relationship was observed in controls. Our studies are among the first to describe cognitive impairments in a transgenic OCD-relevant model, and demonstrate pronounced heterogeneity among Sapap3-KOs. These findings suggest that increased neural activity in mPFC is associated with impaired reversal learning in Sapap3-KOs, providing a likely neural basis for this observed heterogeneity. The Sapap3-KO model is thus a useful tool for future mechanistic studies to determine how mPFC hyperactivity contributes to OCD-relevant cognitive dysfunction.

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.

An Adenosine A2A Receptor Antagonist Improves Multiple Symptoms of Repeated Quinpirole-Induced Psychosis

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder characterized by the repeated rise of concerns (obsessions) and repetitive unwanted behavior (compulsions). Although selective serotonin reuptake inhibitors (SSRIs) is the first-choice drug, response rates to SSRI treatment vary between symptom dimensions. In this study, to find a therapeutic target for SSRI-resilient OCD symptoms, we evaluated treatment responses of quinpirole (QNP) sensitization-induced OCD-related behaviors in mice. SSRI administration rescued the cognitive inflexibility, as well as hyperactivity in the lateral orbitofrontal cortex (lOFC), while no improvement was observed for the repetitive behavior. D₂ receptor signaling in the central striatum (CS) was involved in SSRI-resistant repetitive behavior. An adenosine A_2A antagonist, istradefylline, which rescued abnormal excitatory synaptic function in the CS indirect pathway medium spiny neurons (MSNs) of sensitized mice, alleviated both of the QNP-induced abnormal behaviors with only short-term administration. These results provide a new insight into therapeutic strategies for SSRI-resistant OCD symptoms and indicate the potential of A_2A antagonists as a rapid-acting anti-OCD drug.

Neuroimaging findings in obsessive-compulsive disorder: A narrative review to elucidate neurobiological underpinnings

Obsessive compulsive disorder (OCD) is a common psychiatric illness and significant research has been ongoing to understand its neurobiological basis. Neuroimaging studies right from the 1980s have revealed significant differences between OCD patients and healthy controls. Initial imaging findings showing hyperactivity in the prefrontal cortex (mainly orbitofrontal cortex), anterior cingulate cortex and caudate nucleus led to the postulation of the cortico-striato-thalamo-cortical (CSTC) model for the neurobiology of OCD. However, in the last two decades emerging evidence suggests the involvement of widespread associative networks, including regions of the parietal cortex, limbic areas (including amygdala) and cerebellum. This narrative review discusses findings from structural [Magnetic Resonance Imaging (MRI), Diffusion Tensor Imaging(DTI)], functional [(functional MRI (fMRI), Single photon emission computed tomography (SPECT), Positron emission tomography (PET), functional near-infrared spectroscopy (fNIRS)], combined structural and functional imaging studies and meta-analyses. Subsequently, we collate these findings to describe the neurobiology of OCD including CSTC circuit, limbic system, parietal cortex, cerebellum, default mode network and salience network. In future, neuroimaging may emerge as a valuable tool for personalised medicine in OCD treatment.

Inferior thalamic peduncle deep brain stimulation for treatment-refractory obsessive-compulsive disorder: A phase 1 pilot trial

BACKGROUND

Several different surgical procedures targeting the limbic circuit have been utilized for severe, treatment resistant obsessive-compulsive disorder; however, there has only been limited exploration of the inferior thalamic peduncle (ITP). The aim of this study was to determine the safety and initial efficacy of ITP deep brain stimulation (DBS) in patients with severe obsessive-compulsive disorder.

METHODS

Patients with severe, treatment-refractory obsessive-compulsive disorder were enrolled into this open-label phase 1 DBS pilot study. Bilateral ITP DBS devices were implanted between November 2010 and December 2015. The primary outcome was safety. The initial efficacy was determined by Yale-Brown Obsessive-Compulsive scale (YBOCs) scores. Component Y-BOCs scores, Hamilton Depression Severity Scale, Quality of Life Assessment (SF-36), Oxford Happiness Questionnaire, Warwick-Edinburgh Mental Well-Being Scale, and Sheehan Disability Scale were also analyzed for a minimum of 2 years after surgery. Additionally, preoperative and three-month postoperative FDG-PET studies were performed on two patients.

RESULTS

Five patients (2 males, 3 females; age range 25-48 years) received ITP DBS. All five patients were considered responders at one year (52% improvement in YBOCs scores compared to baseline (range 39-73%, p < 0.01) and last follow-up (54% improvement; range 38-85%; p < 0.01). At two years follow-up, there were three adverse events that occurred in two patients. One patient had his DBS system removed after one year due to the device becoming the object of his obsession. The other two adverse events were not related to the device. Post-operative FDG-PET imaging in two patients demonstrated decreased glucose uptake within the right caudate, right putamen, right supplementary motor area, and right cingulum and increased glucose uptake in bilateral motor areas, left temporal pole, and left orbitfrontal cortex.

CONCLUSIONS

ITP DBS has a favorable safety profile and is potentially an efficacious treatment for severe obsessive-compulsive disorder. Larger clinical trials are necessary to determine efficacy.

Use of an Individual-Level Approach to Identify Cortical Connectivity Biomarkers in Obsessive-Compulsive Disorder

BACKGROUND

Existing functional connectivity studies of obsessive-compulsive disorder (OCD) support a model of circuit dysfunction. However, these group-level observations have failed to yield neuroimaging biomarkers sufficient to serve as a test for the OCD diagnosis, predict current or future symptoms, or predict treatment response, perhaps because these studies failed to account for the substantial intersubject variability in structural and functional brain organization.

METHODS

We used functional regions, localized in each of 41 individual OCD patients, to identify cortical connectivity biomarkers of both global and dimension-specific symptom severity and to detect functional connections that track changes in symptom severity following intensive residential treatment.

RESULTS

Global OCD symptom severity was directly linked to dysconnectivity between large-scale intrinsic brain networks-particularly among the dorsal attention, default, and frontoparietal networks. Changes within a subset of connections among these networks were associated with symptom resolution. Additionally, distinct and nonoverlapping cortical connectivity biomarkers were identified that were significantly associated with the severity of contamination/washing and responsibility for harm/checking symptoms, highlighting the contribution of dissociable neural networks to specific OCD symptom dimensions. By contrast, when we defined functional regions conventionally, using a population-level brain atlas, we could no longer identify connectivity biomarkers of severity or improvement for any of the symptom dimensions.

CONCLUSIONS

Our findings would seem to encourage the use of individual-level approaches to connectivity analyses to better delineate the cortical and subcortical networks underlying symptom severity and improvement at the dimensional level in OCD patients.

Organization of afferents to the orbitofrontal cortex in the rat

The prefrontal cortex (PFC) is usually defined as the frontal cortical area receiving a mediodorsal thalamic (MD) innervation. Certain areas in the medial wall of the rat frontal area receive a MD innervation. A second frontal area that is the target of MD projections is located dorsal to the rhinal sulcus and often referred to as the orbitofrontal cortex (OFC). Both the medial PFC and OFC are comprised of a large number of cytoarchitectonic regions. We assessed the afferent innervation of the different areas of the OFC, with a focus on projections arising from the mediodorsal thalamic nucleus, the basolateral nucleus of the amygdala, and the midbrain dopamine neurons. Although there are specific inputs to various OFC areas, a simplified organizational scheme could be defined, with the medial areas of the OFC receiving thalamic inputs, the lateral areas of the OFC being the recipient of amygdala afferents, and a central zone that was the target of midbrain dopamine neurons. Anterograde tracer data were consistent with this organization of afferents, and revealed that the OFC inputs from these three subcortical sites were largely spatially segregated. This spatial segregation suggests that the central portion of the OFC (pregenual agranular insular cortex) is the only OFC region that is a prefrontal cortical area, analogous to the prelimbic cortex in the medial prefrontal cortex. These findings highlight the heterogeneity of the OFC, and suggest possible functional attributes of the three different OFC areas.

Seroprevalance Anti-Toxoplasma gondii antibodies in children and adolescents with tourette syndrome/chronic motor or vocal tic disorder: A case-control study

Toxoplasma gondii infection may be associated with psychiatric disorders due to its neurological effects. The purpose of this study was to investigate the relation between tic disorders in children and adolescents and Anti-Toxoplasma IgG. 43 children diagnosed with Tourette's syndrome(TS) and 87 with chronic motor or vocal tic disorder(CMVTD), and 130 healthy volunteers, all aged 7-18, were enrolled. Anti-Toxoplasma IgG antibody levels obtained from blood specimens were investigated. Toxoplasma IgG positivity was determined in 16(37.2%) of the patients with TS, in 27(31%) of those with CMVTD and in 12(9.2%) members of the control group. Anti-Toxoplasma gondii antibody positivity was 5.827-fold higher in subjects with TS and 4.425-fold higher in subjects with CMVTD compared to the control group. Correlation was determined between a diagnosis of TS or CMVTD and Anti-Toxoplasma gondii antibodies. We think that it will be useful for the neuropsychiatric process associated with Anti-Toxoplasma gondii antibodies to be clarified.

Altered Regional Cerebral Blood Flow in Idiopathic Hypersomnia

Study Objectives

Idiopathic hypersomnia is characterized by excessive daytime sleepiness, despite normal or long sleep time. Its pathophysiological mechanisms remain unclear. This pilot study aims at characterizing the neural correlates of idiopathic hypersomnia using single photon emission computed tomography.

Methods

Thirteen participants with idiopathic hypersomnia and 16 healthy controls were scanned during resting wakefulness using a high-resolution single photon emission computed tomography scanner with 99mTc-ethyl cysteinate dimer to assess cerebral blood flow. The main analysis compared regional cerebral blood flow distribution between the two groups. Exploratory correlations between regional cerebral blood flow and clinical characteristics evaluated the functional correlates of those brain perfusion patterns. Significance was set at p < .05 after correction for multiple comparisons.

Results

Participants with idiopathic hypersomnia showed regional cerebral blood flow decreases in medial prefrontal cortex and posterior cingulate cortex and putamen, as well as increases in amygdala and temporo-occipital cortices. Lower regional cerebral blood flow in the medial prefrontal cortex was associated with higher daytime sleepiness.

Conclusions

These preliminary findings suggest that idiopathic hypersomnia is characterized by functional alterations in brain areas involved in the modulation of vigilance states, which may contribute to the daytime symptoms of this condition. The distribution of regional cerebral blood flow changes was reminiscent of the patterns associated with normal non-rapid-eye-movement sleep, suggesting the possible presence of incomplete sleep-wake transitions. These abnormalities were strikingly distinct from those induced by acute sleep deprivation, suggesting that the patterns seen here might reflect a trait associated with idiopathic hypersomnia rather than a non-specific state of sleepiness.

Influence of Culture in Obsessive-compulsive Disorder and Its Treatment

Background

The aspects of cultural identity and its impact on obsessive-compulsive disorder (OCD) have been un-derstudied. There are different opinions, ranging from the idea that culture does not affect the symptoms of this condition to the idea that cultures with high religiosity may have more severity of OCD. Also, the concept of OCD has considerably var-ied across history and cultures, from being considered an issue related to lack of control of blasphemous ideas, and a part of anxious issues, to the description of complex neurobiological systems in its causation.

Objective

The aim of this review was to address OCD as a well-characterized disorder with a proposed neurobiological ba-sis which may or may not have variations depending on cultural diversity. The question that was asked in this review is whether or not there are cultural differences in the manifestations of the OCD symptomatology and which factors of cultural diversity have a major influence on such manifestations along with the differences among some cultures regarding OCD is-sues, where the difference among countries has also been highlighted.

Methods

A review of the literature was conducted that includes the following words: obsessive-compulsive disorder, cul-ture, cultural identity and religion in a period of 10 years.

Conclusion

Cultural variations do not seem to differ from symptomatic clusters of OCD, which may be indicating that a se-ries of adaptive behaviors is evolutionarily evolving to be constantly altered, perhaps by well-determined pathophysiological mechanisms. Some aspects that have been related to some dimensions of OCD symptomatology are religion and religiosity, affecting the content of obsessions and the severity of manifestations. Properly evaluating the education background, access to health services, food, and the genetic structure of populations, using investigational instruments sensitive to these cultural elements, will increase our understanding of the importance of culture on OCD and its treatment.

Types of Anxiety and Depression: Theoretical Assumptions and Development of the Anxiety and Depression Questionnaire

The present paper is addressed to (1) the validation of a recently proposed typology of anxiety and depression, and (2) the presentation of a new tool—the Anxiety and Depression Questionnaire (ADQ)—based on this typology. Empirical data collected across two stages—construction and validation—allowed us to offer the final form of the ADQ, designed to measure arousal anxiety, apprehension anxiety, valence depression, anhedonic depression, and mixed types of anxiety and depression. The results support the proposed typology of anxiety and depression and provide evidence that the ADQ is a reliable and valid self-rating measure of affective types, and accordingly its use in scientific research is recommended.

The Neural Correlates of Probabilistic Classification Learning in Obsessive-Compulsive Disorder: A Pilot Study

Individuals suffering from obsessive-compulsive disorder (OCD) have been found to show deficits in implicitly learning probabilistic associations between events. Neuroimaging studies have associated these implicit learning deficits in OCD individuals with aberrant activation of the striatal system. Recent behavioral studies have highlighted that probabilistic classification learning (PCL) deficits in OCD individuals only occur in a disorder-specific context, while PCL remains intact in a neutral context. The neural correlates of implicit learning in an OCD-specific context, however, have not yet been investigated. Using functional magnetic resonance imaging during a neutral (prediction of weather) and an OCD-specific variant (prediction of a virus epidemic) of a PCL paradigm, we assessed brain activity associated with implicit learning processes in 10 participants with OCD and 10 matched healthy controls. Regions of interest (ROIs) were the striatum and the medial temporal lobe. ROI analyses revealed a significantly higher activity in the bilateral putamen and the left hippocampus of OCD participants as compared to healthy controls during both PCL tasks. The group differences could partly be subsumed under a group × task interaction effect with OCD participants showing a significantly higher activity than healthy controls in the left putamen and the left hippocampus in the OCD-specific task variant only. These results suggest a compensation of aberrant striatal activity by an augmented engagement of the explicit memory system particularly in a disorder-relevant context in OCD participants.

How can preclinical mouse models be used to gain insight into prefrontal cortex dysfunction in obsessive-compulsive disorder?

Obsessive-compulsive disorder is a debilitating psychiatric disorder that is characterised by perseverative thoughts and behaviours. Cognitive and affective disturbances play a central role in this illness, and it is therefore not surprising that clinical neuroimaging studies have demonstrated widespread alterations in prefrontal cortex functioning in patients. Preclinical mouse experimental systems provide the opportunity to gain mechanistic insight into the neurobiological changes underlying prefrontal cortex dysfunction through new technologies that allow measurement and manipulation of activity in discrete neural populations in awake, behaving mice. However, recent preclinical research has focused on striatal dysfunction, and has therefore provided relatively little insight regarding the role of the prefrontal cortex in obsessive-compulsive disorder-relevant behaviours. Here, we will discuss a number of translational prefrontal cortex-dependent paradigms, including obsessive-compulsive disorder-relevant tasks that produce compulsive responding, and how they can be leveraged in this context. Drawing on recent examples that have led to mechanistic insight about specific genes, cell types and circuits that mediate prefrontal cortex contributions to distinct aspects of cognition, we will provide a framework for applying similar strategies to identify neural mechanisms underlying obsessive-compulsive disorder-relevant behavioural domains. We propose that research using clinically relevant paradigms will accelerate translation of findings from preclinical mouse models, thus supporting the development of novel therapeutics targeted to specific pathophysiological mechanisms.

Connectivity-based parcellation of the anterior limb of the internal capsule

The anterior limb of the internal capsule (ALIC) is an important locus of frontal-subcortical fiber tracts involved in cognitive and limbic feedback loops. However, the structural organization of its component fiber tracts remains unclear. Therefore, although the ALIC is a promising target for various neurosurgical procedures for psychiatric disorders, more precise understanding of its organization is required to optimize target localization. Using diffusion tensor imaging (DTI) collected on healthy subjects by the Human Connectome Project (HCP), we generated parcellations of the ALIC by dividing it according to structural connectivity to various frontal regions. We then compared individuals' parcellations to evaluate the ALIC's structural consistency. All 40 included subjects demonstrated a posterior-superior to anterior-inferior axis of tract organization in the ALIC. Nonetheless, subdivisions of the ALIC were found to vary substantially, as voxels in the average parcellation were accurately assigned for a mean of only 66.2% of subjects. There were, however, some loci of consistency, most notably in the region maximally connected to orbitofrontal cortex. These findings clarify the highly variable organization of the ALIC and may represent a tool for patient-specific targeting of neuromodulation. Hum Brain Mapp 38:6107-6117, 2017. © 2017 Wiley Periodicals, Inc.

Global and local excitation and inhibition shape the dynamics of the cortico-striatal-thalamo-cortical pathway

The cortico-striatal-thalamo-cortical (CSTC) pathway is a brain circuit that controls movement execution, habit formation and reward. Hyperactivity in the CSTC pathway is involved in obsessive compulsive disorder (OCD), a neuropsychiatric disorder characterized by the execution of repetitive involuntary movements. The striatum shapes the activity of the CSTC pathway through the coordinated activation of two classes of medium spiny neurons (MSNs) expressing D1 or D2 dopamine receptors. The exact mechanisms by which balanced excitation/inhibition (E/I) of these cells controls the network dynamics of the CSTC pathway remain unclear. Here we use non-linear modeling of neuronal activity and bifurcation theory to investigate how global and local changes in E/I of MSNs regulate the activity of the CSTC pathway. Our findings indicate that a global and proportionate increase in E/I pushes the system to states of generalized hyper-activity throughout the entire CSTC pathway. Certain disproportionate changes in global E/I trigger network oscillations. Local changes in the E/I of MSNs generate specific oscillatory behaviors in MSNs and in the CSTC pathway. These findings indicate that subtle changes in the relative strength of E/I of MSNs can powerfully control the network dynamics of the CSTC pathway in ways that are not easily predicted by its synaptic connections.