Fronto-striatal glutamatergic compounds in compulsive and impulsive syndromes: A review of magnetic resonance spectroscopy studies

Glutamate dynamics and BOLD response during OCD symptom provocation in the lateral occipital cortex: A 7 Tesla fMRI-fMRS study

Obsessive-compulsive disorder (OCD) is linked with dysfunction in frontal-striatal, fronto-limbic, and visual brain regions. Research using proton magnetic resonance spectroscopy (1H-MRS) suggests that altered neurometabolite levels, like glutamate, may contribute to this dysfunction. However, static neurometabolite levels in OCD patients have shown inconsistent results, likely due to previous studies' limited focus on neurometabolite dynamics. We employ functional MRS (fMRS) and functional magnetic resonance imaging (fMRI) to explore these dynamics and brain activation during OCD symptom provocation. We utilized a combined 7-tesla fMRI-fMRS setup to examine task-related BOLD response and glutamate changes in the lateral occipital cortex (LOC) of 30 OCD participants and 34 matched controls during an OCD-specific symptom provocation task. The study examined main effects and between-group differences in brain activation and glutamate levels during the task. A whole sample task-effects analysis on data meeting predefined quality criteria showed significant glutamate increases (n = 41 (22 OCD, 19 controls), mean change: 3.2 %, z = 3.75, p < .001) and task activation (n = 54 (26 OCD, 28 controls), p < .001) in the LOC during OCD blocks compared to neutral blocks. However, no differences in task-induced glutamate dynamics or activation between groups were found, nor a correlation between glutamate levels and task activation. We were able to measure task-induced increases in glutamate and BOLD levels, emphasizing its feasibility for OCD research. The absence of group differences highlights the need for further exploration to discern to what extent neurometabolite dynamics differ between OCD patients and controls. Once established, future studies can use pre-post intervention fMRS-fMRI to probe the effects of therapies modulating glutamate pathways in OCD.

Schizophrenia-Like Deficits and Impaired Glutamate/Gamma-aminobutyric acid Homeostasis in Zfp804a Conditional Knockout Mice

BACKGROUND AND HYPOTHESIS

Zinc finger protein 804A (ZNF804A) was the first genome-wide associated susceptibility gene for schizophrenia (SCZ) and played an essential role in the pathophysiology of SCZ by influencing neurodevelopment regulation, neurite outgrowth, synaptic plasticity, and RNA translational control; however, the exact molecular mechanism remains unclear.

STUDY DESIGN

A nervous-system-specific Zfp804a (ZNF804A murine gene) conditional knockout (cKO) mouse model was generated using clustered regularly interspaced short palindromic repeat/Cas9 technology and the Cre/loxP method.

RESULTS

Multiple and complex SCZ-like behaviors, such as anxiety, depression, and impaired cognition, were observed in Zfp804a cKO mice. Molecular biological methods and targeted metabolomics assay validated that Zfp804a cKO mice displayed altered SATB2 (a cortical superficial neuron marker) expression in the cortex; aberrant NeuN, cleaved caspase 3, and DLG4 (markers of mature neurons, apoptosis, and postsynapse, respectively) expressions in the hippocampus and a loss of glutamate (Glu)/γ-aminobutyric acid (GABA) homeostasis with abnormal GAD67 (Gad1) expression in the hippocampus. Clozapine partly ameliorated some SCZ-like behaviors, reversed the disequilibrium of the Glu/GABA ratio, and recovered the expression of GAD67 in cKO mice.

CONCLUSIONS

Zfp804a cKO mice reproducing SCZ-like pathological and behavioral phenotypes were successfully developed. A novel mechanism was determined in which Zfp804a caused Glu/GABA imbalance and reduced GAD67 expression, which was partly recovered by clozapine treatment. These findings underscore the role of altered gene expression in understanding the pathogenesis of SCZ and provide a reliable SCZ model for future therapeutic interventions and biomarker discovery.

The impact of spectral basis set composition on estimated levels of cingulate glutamate and its associations with different personality traits

BACKGROUND

1H-MRS is increasingly used in basic and clinical research to explain brain function and alterations respectively. In psychosis research it is now one of the main tools to investigate imbalances in the glutamatergic system. Interestingly, however, the findings are extremely variable even within patients of similar disease states. One reason may be the variability in analysis strategies, despite suggestions for standardization. Therefore, our study aimed to investigate the extent to which the basis set configuration- which metabolites are included in the basis set used for analysis- would affect the spectral fit and estimated glutamate (Glu) concentrations in the anterior cingulate cortex (ACC), and whether any changes in levels of glutamate would be associated with psychotic-like experiences and autistic traits.

METHODS

To ensure comparability, we utilized five different exemplar basis sets, used in research, and two different analysis tools, r-based spant applying the ABfit method and Osprey using the LCModel.

RESULTS

Our findings revealed that the types of metabolites included in the basis set significantly affected the glutamate concentration. We observed that three basis sets led to more consistent results across different concentration types (i.e., absolute Glu in mol/kg, Glx (glutamate + glutamine), Glu/tCr), spectral fit and quality measurements. Interestingly, all three basis sets included phosphocreatine. Importantly, our findings also revealed that glutamate levels were differently associated with both schizotypal and autistic traits depending on basis set configuration and analysis tool, with the same three basis sets showing more consistent results.

CONCLUSIONS

Our study highlights that scientific results may be significantly altered depending on the choices of metabolites included in the basis set, and with that emphasizes the importance of carefully selecting the configuration of the basis set to ensure accurate and consistent results, when using MR spectroscopy. Overall, our study points out the need for standardized analysis pipelines and reporting.

Biomarkers and Tourette syndrome: a systematic review and meta-analysis

Objective

This research aims to investigate whether peripheral biomarkers might differentiate individuals with Tourette syndrome (TS) from those without the condition.

Methods

A broad range of databases was searched through November 2022. This study employed a systematic literature review and subsequent meta-analysis of case-control studies that assessed the aberration of biomarkers of patients with TS and controls.

Results

A total of 81 studies were identified, out of which 60 met the eligibility criteria for inclusion in the meta-analysis. Following a meticulous screening procedure to determine the feasibility of incorporating case-control studies into the meta-analysis, 13 comparisons were statistically significant [CD3+ T cell, CD4+ T cell, CD4+ T cell to CD8+ T cell ratio, NK-cell, anti-streptolysin O antibodies, anti-DNase antibodies, glutamic acid (Glu), aspartic acid (Asp), ferritin (Fe), zinc (Zn), lead (Pb), vitamin D, and brain-derived neurotrophic factor (BDNF)]. Publication bias was found for anti-streptolysin O antibodies. Suggestive associations were evidenced for norsalsolinol (NSAL), neuron-specific enolase (NSE), and S100B.

Conclusion

In this study, we present empirical evidence substantiating the link between several peripheral biomarkers and the early diagnosis of TS. Larger and more standardized studies are necessary to replicate the observed results, elucidate the specificity of the biomarkers for TS, and evaluate their precision for use in clinical settings.

Molecular Mechanisms Underlying NMDARs Dysfunction and Their Role in ADHD Pathogenesis

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, although the aetiology of ADHD is not yet understood. One proposed theory for developing ADHD is N-methyl-D-aspartate receptors (NMDARs) dysfunction. NMDARs are involved in regulating synaptic plasticity and memory function in the brain. Abnormal expression or polymorphism of some genes associated with ADHD results in NMDAR dysfunction. Correspondingly, NMDAR malfunction in animal models results in ADHD-like symptoms, such as impulsivity and hyperactivity. Currently, there are no drugs for ADHD that specifically target NMDARs. However, NMDAR-stabilizing drugs have shown promise in improving ADHD symptoms with fewer side effects than the currently most widely used psychostimulant in ADHD treatment, methylphenidate. In this review, we outline the molecular and genetic basis of NMDAR malfunction and how it affects the course of ADHD. We also present new therapeutic options related to treating ADHD by targeting NMDAR.

Chronic 3,4-Methylenedioxymethamphetamine (MDMA) Use Is Related to Glutamate and GABA Concentrations in the Striatum But Not the Anterior Cingulate Cortex

BACKGROUND

3,4-Methylenedioxymethamphetamine (MDMA) is a widely used recreational substance inducing acute release of serotonin. Previous studies in chronic MDMA users demonstrated selective adaptations in the serotonin system, which were assumed to be associated with cognitive deficits. However, serotonin functions are strongly entangled with glutamate as well as γ-aminobutyric acid (GABA) neurotransmission, and studies in MDMA-exposed rats show long-term adaptations in glutamatergic and GABAergic signaling.

METHODS

We used proton magnetic resonance spectroscopy (MRS) to measure the glutamate-glutamine complex (GLX) and GABA concentrations in the left striatum and medial anterior cingulate cortex (ACC) of 44 chronic but recently abstinent MDMA users and 42 MDMA-naïve healthy controls. While the Mescher-Garwood point-resolved-spectroscopy sequence (MEGA-PRESS) is best suited to quantify GABA, recent studies reported poor agreement between conventional short-echo-time PRESS and MEGA-PRESS for GLX measures. Here, we applied both sequences to assess their agreement and potential confounders underlying the diverging results.

RESULTS

Chronic MDMA users showed elevated GLX levels in the striatum but not the ACC. Regarding GABA, we found no group difference in either region, although a negative association with MDMA use frequency was observed in the striatum. Overall, GLX measures from MEGA-PRESS, with its longer echo time, appeared to be less confounded by macromolecule signal than the short-echo-time PRESS and thus provided more robust results.

CONCLUSION

Our findings suggest that MDMA use affects not only serotonin but also striatal GLX and GABA concentrations. These insights may offer new mechanistic explanations for cognitive deficits (e.g., impaired impulse control) observed in MDMA users.

Direct changes of neurometabolic concentrations in the pregenual anterior cingulate cortex among obsessive-compulsive patients after repetitive transcranial magnetic stimulation treatment

BACKGROUND AND AIM

Although Repetitive Transcranial Magnetic Stimulation (rTMS) is a promising new noninvasive brain stimulation therapy, its underlying mechanisms of action remain unknown. OCD patients exhibit impaired response control and attention shifting, which is linked to some brain areas such as anterior cingulate cortex and basal ganglia. OCD patients also display altered neurometabolic concentrations in cortical cortical-striatal-thalamic-cortical (CSTC). In this study, we aimed to elucidate efficacy of rTMS treatment in alleviating related symptoms and pregenual anterior cingulate cortex (pACC) neurometabolites.

METHODS

OCD patients were randomly divided into either drug (n = 23) or drug + rTMS (n = 29) groups, and those in the latter group subjected to 4-week rTMS treatment. All participants were visited twice, at baseline and follow-up after four weeks. During both visits, all patients were subjected to 1H-MRS, then Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Global Assessment Function (GAF) used to assess severity of obsessive-compulsive symptoms. We also evaluated synchronous anxiety and depression by Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), Hamilton Anxiety Scale (HAM-A) and Hamilton Depression Scale (HAM-D).

RESULTS

After 4 weeks of treatment, patients in the Drug + rTMS group displayed significantly lower Y-BOCS (p = 0.038), BDI (p = 0.009), HAM-D (p = 0.013), HAM-A (p = 0.012) scores than their counterparts in the Drug group. Conversely, patients in the Drug + rTMS group had significantly higher tNAA concentrations (p = 0.030) than those in the Drug group. Notably, the Drug + rTMS group exhibited higher, but insignificant Glu (p = 0.055) and Glx (p = 0.068) concentrations compared to the Drug group. Partial correlation analysis revealed a significant negative correlation between post HAM-A scores and 4-week change of pACC glutamate levels in the Drug + rTMS group (r = -0.434, p = 0.02).

CONCLUSION

rTMS treatment is an efficacious treatment therapy for OCD, mainly by inducing changes in neurometabolites.

Neonatal loss of FGFR2 in astroglial cells affects locomotion, sociability, working memory, and glia-neuron interactions in mice

Fibroblast growth factor receptor 2 (FGFR2) is almost exclusively expressed in glial cells in postnatal mouse brain, but its impact in glia for brain behavioral functioning is poorly understood. We compared behavioral effects from FGFR2 loss in both neurons and astroglial cells and from FGFR2 loss in astroglial cells by using either the pluripotent progenitor-driven hGFAP-cre or the tamoxifen-inducible astrocyte-driven GFAP-creERT2 in Fgfr2 floxed mice. When FGFR2 was eliminated in embryonic pluripotent precursors or in early postnatal astroglia, mice were hyperactive, and had small changes in working memory, sociability, and anxiety-like behavior. In contrast, FGFR2 loss in astrocytes starting at 8 weeks of age resulted only in reduced anxiety-like behavior. Therefore, early postnatal loss of FGFR2 in astroglia is critical for broad behavioral dysregulation. Neurobiological assessments demonstrated that astrocyte-neuron membrane contact was reduced and glial glutamine synthetase expression increased only by early postnatal FGFR2 loss. We conclude that altered astroglial cell function dependent on FGFR2 in the early postnatal period may result in impaired synaptic development and behavioral regulation, modeling childhood behavioral deficits like attention deficit hyperactivity disorder (ADHD).

Cerebellar gamma-aminobutyric acid: Investigation of group effects in neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) including autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) are thought to arise in part from the disruption in the excitatory/inhibitory balance of gamma-aminobutyric acid (GABA) and glutamate in the brain. Recent evidence has shown the involvement of the cerebellum in cognition and affect regulation, and cerebellar atypical function or damage is reported frequently in NDDs. Magnetic resonance spectroscopy studies have reported decreases in GABA in cortical brain areas in the NDDs, however, GABA levels in the cerebellum have not been examined. To determine possible group effects, we used a MEGA-PRESS acquisition to investigate GABA+ levels in a cerebellar voxel in 343 individuals (aged 2.5-22 years) with ASD, ADHD, OCD and controls. Using a mixed effects model, we found no significant differences between groups in GABA+ concentration. Our findings suggest that cerebellar GABA+ levels do not differentiate NDD groups.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Intravenous esketamine leads to an increase in impulsive and suicidal behaviour in a patient with recurrent major depression and borderline personality disorder

Objectives: As clinical studies demonstrated that ketamine possesses rapid-acting antidepressant and antisuicidal effects, it is increasingly used in affective disorders. The neuroplastic properties of ketamine are well described in preclinical and imaging studies, and are highly related to its antidepressive mechanism of action.Methods: Here, we report on a female patient with recurrent major depression and borderline personality disorder (BPD) who was treated with intravenous (i.v.) esketamine as rapid-acting augmentation therapy to improve severe and acute depressive symptoms and suicidal behaviour.Results: Esketamine led to an initial improvement of these symptoms. However, during the course of treatment, loosened and disinhibited behaviour and severe suicidal ideation occurred during and immediately after esketamine application. Hence, i.v. esketamine was discontinued, and she further received treatment as usual, which demonstrated to be beneficial.Conclusions: With current knowledge at hand, one cannot exclude esketamine's effects on the equilibrium of neural plasticity in brain networks, potentially initiating undesirable symptoms as impulsive behaviour and emotional dysregulation. Therefore, until investigations focus on efficacy and side effects profile of esketamine in depressed patients with (comorbid) BPD, treatment with this fast-acting medication should be considered with caution in this patient group.

Memantine as treatment for compulsivity in child and adolescent psychiatry: Descriptive findings from an incompleted randomized, double-blind, placebo-controlled trial

Background

Autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD) are mental disorders with a considerable overlap in terms of their defining symptoms. The glutamatergic agent memantine appears to be a promising candidate for the treatment of ASD and OCD in children and adolescents. The aim of this study was to investigate the clinical efficacy and tolerability/safety of memantine in this population.

Methods

This randomized, double-blind, placebo-controlled multicenter add-on trial comprised patients aged 6 to 17; 9 years with a confirmed diagnosis of ASD and/or OCD. Participants were randomized to either memantine or placebo for 10 consecutive weeks, including an up-titration phase.

Results

A total of 7 patients were included in the study. N = 4 (57.1%) participants were treated with verum (memantine) and n = 3 (42.9%) received placebo. Patients receiving memantine showed a more pronounced reduction in their CY-BOCS score, as well as greater CGI-Improvement, compared to patients receiving placebo. No serious adverse events (SAEs) were reported.

Conclusions

Our findings, although based on a very small number of patients and therefore insufficient to draw clear conclusions, appear to be in line with the hypothesis that memantine is an effective, tolerable and safe agent for children and adolescents.

Trial registration

EudraCT Number: 2014-003080-38, Registered 14 July 2014, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2014-003080-38.

The comparison of nucleotide metabolites and amino acids patterns in patients with eating disorders, with and without symptoms of depression

Purines, pyrimidines, and amino acid level have gained attention recently as potential determinants of mental disorders. However, eating disorders patients (ED) have not been yet appropriately studied, especially subjects with coexisting mood disorders. This paper examines the serum level of nucleotide catabolites and plasma amino acids in eating disorders with hyperphagia, with and without Major Depressive Disorder (MDD). Samples were taken from adult persons suffering from eating disorders (two forms: simple obesity and binge eating disorder) with MDD (n = 20) and without (n = 17). Serum nucleotides and plasma amino acids concentrations were analyzed with high-performance liquid chromatography-mass spectrometry. The nucleotides metabolite in MDD patients had a significantly (p < 0.05) lower uridine. Among MDD patients with ED significantly (p < 0.05) higher levels of asparagine, glutamine, proline, and arginine were found as compared to the control group. This study demonstrated differences in nucleotide metabolite and amino acid pattern in depression patients with eating disorders. This may be relevant to the mechanisms and may help identify biomarkers.

Memantine treatment does not affect compulsive behavior or frontostriatal connectivity in an adolescent rat model for quinpirole-induced compulsive checking behavior

RATIONALE

Compulsivity often develops during childhood and is associated with elevated glutamate levels within the frontostriatal system. This suggests that anti-glutamatergic drugs, like memantine, may be an effective treatment.

OBJECTIVE

Our goal was to characterize the acute and chronic effect of memantine treatment on compulsive behavior and frontostriatal network structure and function in an adolescent rat model of compulsivity.

METHODS

Juvenile Sprague-Dawley rats received repeated quinpirole, resulting in compulsive checking behavior (n = 32; compulsive) or saline injections (n = 32; control). Eight compulsive and control rats received chronic memantine treatment, and eight compulsive and control rats received saline treatment for seven consecutive days between the 10th and 12th quinpirole/saline injection. Compulsive checking behavior was assessed, and structural and functional brain connectivity was measured with diffusion MRI and resting-state fMRI before and after treatment. The other rats received an acute single memantine (compulsive: n = 12; control: n = 12) or saline injection (compulsive: n = 4; control: n = 4) during pharmacological MRI after the 12th quinpirole/saline injection. An additional group of rats received a single memantine injection after a single quinpirole injection (n = 8).

RESULTS

Memantine treatment did not affect compulsive checking nor frontostriatal structural and functional connectivity in the quinpirole-induced adolescent rat model. While memantine activated the frontal cortex in control rats, no significant activation responses were measured after single or repeated quinpirole injections.

CONCLUSIONS

The lack of a memantine treatment effect in quinpirole-induced compulsive adolescent rats may be partly explained by the interaction between glutamatergic and dopaminergic receptors in the brain, which can be evaluated with functional MRI.

Glutamatergic medications as adjunctive therapy for moderate to severe obsessive-compulsive disorder in adults: a systematic review and meta-analysis

BACKGROUND

Obsessive-compulsive disorder (OCD) is among the most disabling neuropsychiatric conditions characterized by the presence of repetitive intrusive thoughts, impulses, or images (obsessions) and/or ritualized mental or physical acts (compulsions). Serotonergic medications, particularly Selective Serotonin Reuptake Inhibitors (SSRIs), are the first-line treatments for patients with OCD. Recently, dysregulation of glutamatergic system has been proposed to be involved in the etiology of OCD. We designed this systematic review and meta-analysis to evaluate clinical efficacy of glutamatergic medications in patients with OCD, according to the guidelines of Cochrane collaboration.

METHOD

We searched Medline, Scopus, and Cochrane library without applying any language filter. Two of the authors independently reviewed search results for irrelevant and duplicate studies and extracted data and assessed methodological quality of the studies. We transformed data into a common rubric and calculated a weighted treatment effect across studies using Review Manager.

RESULTS

We found 476 references in 3 databases, and after exclusion of irrelevant and duplicate studies, 17 studies with total number of 759 patients with OCD were included. In the present review we found evidence for several drugs such as memantine, N-acetylcysteine (NAC), Minocycline, L-carnosine and riluzole. Glutamaterigic drug plus SSRIs were superior to SSRI+ Placebo with regard to Y-BOCS scale [standardized mean difference (SMD = - 3.81 95% CI = - 4.4, - 3.23).

CONCLUSION

Augmentation of glutamatergic medications with SSRIs are beneficial in obsessive-compulsive patients, no harmful significant differences in any safety outcome were found between the groups.

Brain MRI in Autism Spectrum Disorder: Narrative Review and Recent Advances

Autism spectrum disorder (ASD) is neuropsychiatric continuum of disorders characterized by persistent deficits in social communication and restricted repetitive patterns of behavior which impede optimal functioning. Early detection and intervention in ASD children can mitigate the deficits in social interaction and result in a better outcome. Various non-invasive imaging methods and molecular techniques have been developed for the early identification of ASD characteristics. There is no general consensus on specific neuroimaging features of autism; however, quantitative magnetic resonance techniques have provided valuable structural and functional information in understanding the neuropathophysiology of ASD and how the autistic brain changes during childhood, adolescence, and adulthood. In this review of decades of ASD neuroimaging research, we identify the structural, functional, and molecular imaging clues that most accurately point to the diagnosis of ASD vs. typically developing children. These studies highlight the 1) exaggerated synaptic pruning, 2) anomalous gyrification, 3) interhemispheric under- and overconnectivity, and 4) excitatory glutamate and inhibitory GABA imbalance theories of ASD. The application of these various theories to the analysis of a patient with ASD is mitigated often by superimposed comorbid neuropsychological disorders, evolving brain maturation processes, and pharmacologic and behavioral interventions that may affect the structure and function of the brain. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 3.

Decades of Progress in the Psychopharmacology of Autism Spectrum Disorder

Recent decades have been marked by a wave drug treatment research in autism spectrum disorder (ASD). This work has resulted in improved ability to treat commonly occurring behavioral challenges associated with ASD including most prominently irritability marked by aggression, self-injurious behavior, and severe tantrums. While treatment of interfering behavior has progressed in our field, there remain several areas of unmet medical need including most prominently a lack of any approved drug therapies for the core, defining symptoms of autism. We outline the progress to date in the field of autism drug treatment while taking a future look forward into how decades of work can inform better future steps in this field.

Region-specific elevations of glutamate + glutamine correlate with the sensory symptoms of autism spectrum disorders

Individuals on the autism spectrum are often reported as being hyper- and/or hyporeactive to sensory input. These sensory symptoms were one of the key observations that led to the development of the altered excitation-inhibition (E-I) model of autism, which posits that an increase ratio of excitatory to inhibitory signaling may explain certain phenotypical expressions of autism spectrum disorders (ASD). While there has been strong support for the altered E-I model of autism, much of the evidence has come from animal models. With regard to in-vivo human studies, evidence for altered E-I balance in ASD come from studies adopting magnetic resonance spectroscopy (MRS). Spectral-edited MRS can be used to provide measures of the levels of GABA + (GABA + macromolecules) and Glx (glutamate + glutamine) in specific brain regions as proxy markers of inhibition and excitation respectively. In the current study, we found region-specific elevations of Glx in the primary sensorimotor cortex (SM1) in ASD. There were no group differences of GABA+ in either the SM1 or thalamus. Higher levels of Glx were associated with more parent reported difficulties of sensory hyper- and hyporeactivity, as well as reduced feed-forward inhibition during tactile perception in children with ASD. Critically, the finding of elevated Glx provides strong empirical support for increased excitation in ASD. Our results also provide a clear link between Glx and the sensory symptoms of ASD at both behavioral and perceptual levels.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Mice with reduced glutamate transporter GLT1 expression exhibit behaviors related to attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common neuropsychiatric disorder in children. Although animal models and human brain imaging studies indicate a significant role for glutamatergic dysfunction in ADHD, there is no direct evidence that glutamatergic dysfunction is sufficient to induce ADHD-like symptoms. The glial glutamate transporter GLT1 plays a critical role in glutamatergic neurotransmission. We report here the generation of mice expressing only 20% of normal levels of the GLT1. Unlike conventional GLT1 knockout mice, these mice survive to adulthood and exhibit ADHD-like phenotypes, including hyperactivity, impulsivity and impaired memory. These findings indicate that glutamatergic dysfunction due to GLT1 deficiency, a mechanism distinct from the dopaminergic deficit hypothesis of ADHD, underlies ADHD-like symptoms.

Developmental changes in fronto-striatal glutamate and their association with functioning during inhibitory control in autism spectrum disorder and obsessive compulsive disorder

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Multi-center, longitudinal, transdiagnostic study of glutamate and neural activity.

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Differing roles of glutamate on activity in striatum during inhibitory control.

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Glutamate concentrations in ACC decrease over time in ASD adolescents.

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Differing neural mechanisms of compulsivity in OCD and repetitive behaviors in ASD.

Autism spectrum disorder (ASD) and obsessive compulsive disorder (OCD) show overlapping symptomatology and deficits in inhibitory control, which are associated with altered functioning and glutamatergic signaling in fronto-striatal circuitry. These parameters have never been examined together. The purpose of the current study was to investigate functioning during inhibitory control and its association with fronto-striatal glutamate concentrations across these disorders using a multi-center, longitudinal approach. Adolescents with ASD (n = 24), OCD (n = 15) and controls (n = 35) underwent two magnetic resonance imaging (MRI) sessions with a one-year interval. This included proton magnetic resonance spectroscopy (¹H-MRS; n = 74) and functional MRI during an inhibitory control task (n = 53). We investigated ¹H-MRS data and fMRI data separately as well as integrated in a multimodal analysis using linear models focusing on diagnosis and continuous measures of overlapping compulsivity symptoms. ACC glutamate was reduced over time in the ASD group compared with controls, while striatal glutamate decreased over time independent of diagnosis. Increased compulsive behavior seemed to be associated with increased striatal activity during failed inhibitory control. The integrated analyses showed differential involvement of increased striatal glutamate during failed but decreased striatal glutamate during successful inhibitory control in the OCD group compared to controls and ASD, suggesting different underlying mechanisms for OCD compared to ASD.

Disorder-specific alterations of tactile sensitivity in neurodevelopmental disorders

Alterations of tactile processing have long been identified in autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). However, the extent to which these alterations are disorder-specific, rather than disorder-general, and how they relate to the core symptoms of each disorder, remains unclear. We measured and compared tactile detection, discrimination, and order judgment thresholds between a large sample of children with ASD, ADHD, ASD + ADHD combined and typically developing controls. The pattern of results suggested that while difficulties with tactile detection and order judgement were more common in children with ADHD, difficulties with tactile discrimination were more common in children with ASD. Interestingly, in our subsequent correlation analyses between tactile perception and disorder-specific clinical symptoms, tactile detection and order judgment correlated exclusively with the core symptoms of ADHD, while tactile discrimination correlated exclusively with the symptoms of ASD. When taken together, these results suggest that disorder-specific alterations of lower-level sensory processes exist and are specifically related to higher-level clinical symptoms of each disorder.

GABA and glutamate deficits from frontotemporal lobar degeneration are associated with disinhibition

Behavioural disinhibition is a common feature of the syndromes associated with frontotemporal lobar degeneration (FTLD). It is associated with high morbidity and lacks proven symptomatic treatments. A potential therapeutic strategy is to correct the neurotransmitter deficits associated with FTLD, thereby improving behaviour. Reductions in the neurotransmitters glutamate and GABA correlate with impulsive behaviour in several neuropsychiatric diseases and there is post-mortem evidence of their deficit in FTLD. Here, we tested the hypothesis that prefrontal glutamate and GABA levels are reduced by FTLD in vivo, and that their deficit is associated with impaired response inhibition. Thirty-three participants with a syndrome associated with FTLD (15 patients with behavioural variant frontotemporal dementia and 18 with progressive supranuclear palsy, including both Richardson's syndrome and progressive supranuclear palsy-frontal subtypes) and 20 healthy control subjects were included. Participants undertook ultra-high field (7 T) magnetic resonance spectroscopy and a stop-signal task of response inhibition. We measured glutamate and GABA levels using semi-LASER magnetic resonance spectroscopy in the right inferior frontal gyrus, because of its strong association with response inhibition, and in the primary visual cortex, as a control region. The stop-signal reaction time was calculated using an ex-Gaussian Bayesian model. Participants with frontotemporal dementia and progressive supranuclear palsy had impaired response inhibition, with longer stop-signal reaction times compared with controls. GABA concentration was reduced in patients versus controls in the right inferior frontal gyrus, but not the occipital lobe. There was no group-wise difference in partial volume corrected glutamate concentration between patients and controls. Both GABA and glutamate concentrations in the inferior frontal gyrus correlated inversely with stop-signal reaction time, indicating greater impulsivity in proportion to the loss of each neurotransmitter. We conclude that the glutamatergic and GABAergic deficits in the frontal lobe are potential targets for symptomatic drug treatment of frontotemporal dementia and progressive supranuclear palsy.

Dopaminergic System Alteration in Anxiety and Compulsive Disorders: A Systematic Review of Neuroimaging Studies

Objective: The dopaminergic system is involved in many psychiatric disorders as a GABAergic, serotonergic, and glutamatergic system. A systematic review and meta-analysis was performed to elucidate the alteration of the dopaminergic system in anxiety and compulsive disorders.

Methods: The databases of Pubmed, Embase, and ScienceDirect were searched and articles reporting the involvement of the dopaminergic system in patients with anxiety disorder and obsessive compulsive disorder (OCD) were recognized. The key research data were extracted from the included articles and standardized mean differences were calculated using meta-analyses if there were more than two studies with obtainable data. Sensitivity analyses were further performed to detect the stability of results, and the qualities of all the included studies were assessed using the Newcastle Ottawa scale.

Results: Finally, we identified 8 and 11 studies associated with anxiety disorder and OCD for further analysis, respectively. Most consistently, the striatal dopamine D₂ receptor (D₂R) of OCD patients had decreased while no significant correlation was found between striatal D2R and disease severity. The striatal dopamine transporter (DAT) had not been significantly altered in both the anxiety disorder and OCD patients. The heterogeneity values from the meta-analyses were extremely high while those results remained stable after sensitivity analyses. Inconsistent data were found in the striatal D₂R of patients with anxiety disorder. Limited data had suggested that dopamine synthesis increased in most regions of the cerebral cortex and cerebellum in OCD patients.

Conclusions: The most convincing finding was that the D₂ receptor decreased in patients with obsessive compulsive disorder. The dopamine transporter may have no relationship with anxiety and compulsive disorder.

Neurobiological changes in striatal glutamate are associated with trait impulsivity of differential reinforcement of low-rate-response behavior in male rats

Impulsive action can be measured using rat's responses on a differential reinforcement of low-rate-response (DRL) task in which performance may be varied between rats. Nevertheless, neurobiological profiles underlying the trait impulsivity of DRL behavior remain largely unknown. Here, in vivo non-invasive proton magnetic resonance spectroscopy (¹H-MRS) and Western blot assay were performed to assess neurobiological changes in the dorsal striatum (DS) and nucleus accumbens (NAc) in relation to individual differences in DRL behavior. A cohort of rats was subjected to acquire a DRL task over 14 daily sessions. High impulsive (HI) and low impulsive (LI) rats were screened by behavioral measures displaying a lower response efficiency and performing more nonreinforced responses in HI rats and vice versa. MRS measurements indicated that the HI group had a lower NAc glutamate (Glu) level than did the LI group, whereas no such difference was found in the other five metabolites in this area. Moreover, no intergroup difference was observed in any metabolite in the DS. The results of Western blot assay revealed that protein expressions of GluN1 (but not GluN2B) subunit of N-methyl-D-aspartate receptors in the DS and NAc were higher in the HI group than in the LI group. This inherent timing impulsivity was not attributed to risky behavioral propensity because both Hl and LI rats could acquire a risk-dependent choice. The findings of this study, supported by certain correlations among behavioral, brain imaging, and neuroreceptor indices, provide evidence of the neurobiological changes of striatal Glu underlying trait impulsive action of DRL behavior.

Disrupted pathways from the frontal-parietal cortices to basal nuclei and the cerebellum are a feature of the obsessive-compulsive disorder spectrum and can be used to aid in early differential diagnosis

A marker for distinguishing patients with obsessive-compulsive disorder (OCD) spectrum has not yet been identified. Whole-brain resting-state effective and functional connectivity (rsEC and rsFC, respectively) networks were constructed for 50 unmedicated OCD (U-OCD) patients, 45 OCD patients in clinical remission (COCD), 47 treatment-resistant OCD (T-OCD) patients, 42 chronic schizophrenia patients who exhibit OCD symptoms (SCHOCD), and 50 healthy controls (HCs). Multivariate pattern analysis (MVPA) was performed to investigate the accuracy of using connectivity alterations to distinguished among the aforementioned groups. Compared to HCs, rsEC connections were significantly disrupted in the U-OCD (n = 15), COCD (n = 8), and T-OCD (n = 19) groups. Additionally, 21 rsEC connections were significantly disrupted in the T-OCD group compared to the SCHOCD group. The disrupted rsEC networks were associated mainly with the frontal-parietal cortex, basal ganglia, limbic regions, and the cerebellum. Classification accuracies for distinguishing OCD patients from HCs and SCHOCD patients ranged from 66.6% to 98.0%. In conclusion, disrupted communication from the frontal-parietal cortices to subcortical basal nuclei and the cerebellum may represent a functional pathological feature of the OCD spectrum. MVPA based on both abnormal rsEC and rsFC patterns may aid in early differential diagnosis of OCD.

Creativity and ADHD: A review of behavioral studies, the effect of psychostimulants and neural underpinnings

Attention deficit/hyperactivity disorder (ADHD) is a debilitating disorder and most research therefore focuses on its deficits and its treatment. Research on the potential positive sides of ADHD is limited, and although a comprehensive overview of empirical studies on this subject is missing, it has been suggested that ADHD is associated with enhanced creativity. To identify important relations, trends and gaps in the literature, we review 31 behavioral studies on creativity and ADHD, distinguishing different research designs, age groups, creativity measurements and effects of psychostimulants, as well as reflecting the potential underlying neural mechanisms of creativity and ADHD. Most studies find evidence for increased divergent thinking for those with high ADHD scores (subclinical) but not for those with the disorder (clinical). The rates of creative abilities/achievements were high among both clinical and subclinical groups. We found no evidence for increased convergent thinking abilities in ADHD, nor did we find an overall negative effect of psychostimulants on creativity. Neuroscientific findings suggest candidate regions as well as mechanisms that should be studied further to increase our understanding of the relationship between creativity and ADHD. We propose research opportunities to boost the knowledge needed to better understand the potential positive side of ADHD.

Comparison of plasma nucleotide metabolites and amino acids pattern in patients with binge eating disorder and obesity

Binge eating disorder (BED) increasingly affects population, but the mechanisms of the disease and its biomarkers are not well characterized. Recently, plasma purines, pyrimidines, amino acid and nicotinamide metabolites profiling attracted attention in studies on pathology and biomarkers of mental disorders but has not been adequately studied in BED. Blood and plasma samples were taken from patients with adult obese with BED (n = 20) and control adult obese without BED (n = 17). Plasma samples were analyzed for nucleotides and amino acid concentrations with high-performance liquid chromatography-mass spectrometry. BED had a significantly (p < 0.05) lower uridine and hypoxanthine to creatinine ratio compared to the control group. Among the amino acids BED patients had significantly (p < 0.05) lower concentrations of glutamic acid, leucine, isoleucine and the whole branched-chain amino acids group, while the concentration of citrulline was increased. Among nicotinamide metabolites, 1-methylnicotinamide levels were significantly (p < 0.05) lower. This study highlights potential use of profiling nucleotide metabolite and amino acid pattern in BED patients that may provide information on mechanisms and potential biomarkers. However, further investigation in larger population is necessary to identify clinical correlates of the observed changes.

Recent Advances in the Pharmacological Management of Behavioral Disturbances Associated with Autism Spectrum Disorder in Children and Adolescents

Autism spectrum disorder (ASD) is a heterogeneous neuropsychiatric condition affecting an estimated one in 36 children. Youth with ASD may have severe behavioral disturbances including irritability, aggression, and hyperactivity. Currently, there are only two medications (risperidone and aripiprazole) approved by the US Food and Drug Administration (FDA) for the treatment of irritability associated with ASD. Pharmacologic treatments are commonly used to target ASD-associated symptoms including irritability, mood lability, anxiety, and hyperactivity. However, evidence for the efficacy of many commonly used treatments is limited by the lack of large placebo-controlled trials of these medications in this population. Research into the pathophysiology of ASD has led to new targets for pharmacologic therapy including the neuroimmune system, the endocannabinoid system, and the glutamatergic neurotransmitter system. The goal of this review is to provide an overview of the current evidence base for commonly used treatments, as well as emerging treatment options for common behavioral disturbances seen in youth with ASD.

Neurochemical correlates of behavioral treatment of pediatric trichotillomania

BACKGROUND

Trichotillomania (TTM) is a chronic and impairing psychiatric disorder with suspected dysfunctional cortico-striato-thalamo-cortical (CSTC) circuit activity reflecting excitatory/inhibitory signaling imbalance. TTM neurochemistry is understudied, with no prior research using magnetic resonance spectroscopy (MRS). This pilot investigation examined associations between TTM diagnosis, symptom severity, and response to behavioral treatment with MRS neurometabolites glutamate (Glu) and γ-aminobutyric acid (GABA) in CSTC structures.

METHODS

Proton echo-planar spectroscopic imaging (PEPSI) MRS was acquired from bilateral pregenual anterior cingulate cortex (pACC), caudate, putamen, globus pallidus, thalamus, and proximal white matter in 10 unmedicated girls with TTM, ages 9-17 years, before and after treatment, and from 13 age- and sex-matched healthy controls.

RESULTS

Nine of 10 TTM patients were treatment responders. Pretreatment mean Glu and GABA did not differ significantly between participants and controls. Pretreatment TTM symptoms were correlated with Glu in (left + right) pACC (r = 0.88, p = 0.02) and thalamus (r = 0.82, p = 0.012), and were negatively correlated with pACC GABA (r = -0.84, p = 0.034). Mean GABA in putamen increased 69% (baseline to post-treatment) (p = 0.027). Higher pretreatment Glu in caudate, putamen, globus pallidus, and thalamus predicted greater symptom decreases with treatment (all r < -0.6, p < 0.05); higher caudate GABA predicted less treatment-related symptom decline (r = 0.86, p = 0.014).

LIMITATIONS

Small sample, GABA quantified with spectral fitting rather than editing.

CONCLUSION

Consistent with other neuroimaging, MRS reveals discrete CSTC chemical changes with effective behavior therapy, and possibly with TTM etiology. TTM symptoms relate to excess excitatory versus inhibitory signaling in pACC and thalamus; symptom improvement may reflect reduced excitatory drive of the CSTC direct-pathway activity.

Mental health dished up-the use of iPSC models in neuropsychiatric research

Genetic and molecular mechanisms that play a causal role in mental illnesses are challenging to elucidate, particularly as there is a lack of relevant in vitro and in vivo models. However, the advent of induced pluripotent stem cell (iPSC) technology has provided researchers with a novel toolbox. We conducted a systematic review using the PRISMA statement. A PubMed and Web of Science online search was performed (studies published between 2006–2020) using the following search strategy: hiPSC OR iPSC OR iPS OR stem cells AND schizophrenia disorder OR personality disorder OR antisocial personality disorder OR psychopathy OR bipolar disorder OR major depressive disorder OR obsessive compulsive disorder OR anxiety disorder OR substance use disorder OR alcohol use disorder OR nicotine use disorder OR opioid use disorder OR eating disorder OR anorexia nervosa OR attention-deficit/hyperactivity disorder OR gaming disorder. Using the above search criteria, a total of 3515 studies were found. After screening, a final total of 56 studies were deemed eligible for inclusion in our study. Using iPSC technology, psychiatric disease can be studied in the context of a patient’s own unique genetic background. This has allowed great strides to be made into uncovering the etiology of psychiatric disease, as well as providing a unique paradigm for drug testing. However, there is a lack of data for certain psychiatric disorders and several limitations to present iPSC-based studies, leading us to discuss how this field may progress in the next years to increase its utility in the battle to understand psychiatric disease.

Chronic HIV-1 Tat exposure alters anterior cingulate cortico-basal ganglia-thalamocortical synaptic circuitry, associated behavioral control, and immune regulation in male mice

HIV-1 selectively disrupts neuronal integrity within specific brain regions, reflecting differences in viral tropism and/or the regional differences in the vulnerability of distinct neuronal subpopulations within the CNS. Deficits in prefrontal cortex (PFC)-mediated executive function and the resultant loss of behavioral control are a particularly debilitating consequence of neuroHIV. To explore how HIV-1 disrupts executive function, we investigated the effects of 48 h, 2 and/or 8 weeks of HIV-1 Tat exposure on behavioral control, synaptic connectivity, and neuroimmune function in the anterior cingulate cortex (ACC) and associated cortico-basal ganglia (BG)-thalamocortical circuitry in adult, Tat transgenic male mice. HIV-1 Tat exposure increased novelty-exploration in response to novel food, flavor, and environmental stimuli, suggesting that Tat triggers increased novelty-exploration in situations of competing motivation (e.g., drive to feed or explore vs. fear of novel, brightly lit open areas). Furthermore, Tat induced adaptability in response to an environmental stressor and pre-attentive filtering deficits. The behavioral insufficiencies coincided with decreases in the inhibitory pre- and post-synaptic proteins, synaptotagmin 2 and gephyrin, respectively, in the ACC, and alterations in specific pro- and anti-inflammatory cytokines out of 23 assayed. The interaction of Tat exposure and the resultant time-dependent, selective alterations in CCL4, CXCL1, IL-12p40, and IL-17A levels in the PFC predicted significant decreases in adaptability. Tat decreased dendritic spine density and cortical VGLUT1 inputs, while increasing IL-1β, IL-6, CCL5, and CCL11 in the striatum. Alternatively, IL-1α, CCL5, and IL-13 were decreased in the mediodorsal thalamus despite the absence of synaptic changes. Thus, HIV-1 Tat appears to uniquely and systematically disrupt immune regulation and the inhibitory and excitatory synaptic balance throughout the ACC-BG-thalamocortical circuitry resulting in a loss of behavioral control.

Diminished Myoinositol in Ventromedial Prefrontal Cortex Modulates the Endophenotype of Impulsivity

Maladaptive impulsivity manifests in a variety of disorders, including attention-deficit hyperactivity disorder (ADHD), depression, and substance use disorder. However, the etiological mechanisms of impulsivity remain poorly understood. In the present study, we used in-vivo proton magnetic resonance spectroscopy (1H-MRS) to investigate neurometabolite content in the prefrontal cortex (PFC) and striatum of rats exhibiting low- versus high-impulsive (LI, HI) behavior on a visual attentional task. We validated our 1H-MRS findings using regionally resolved ex-vivo mass spectroscopy, transcriptomics, and site-directed RNA interference in the ventromedial PFC. We report a significant reduction in myoinositol levels in the PFC but not the striatum of HI rats compared with LI rats. Reduced myoinositol content was localized to the infralimbic (IL) cortex, where significant reductions in transcript levels of key proteins involved in the synthesis and recycling of myoinositol (IMPase1) were also present. Knockdown of IMPase1in the IL cortex increased impulsivity in nonimpulsive rats when the demand on inhibitory response control was increased. We conclude that diminished myoinositol levels in ventromedial PFC causally mediate a specific form of impulsivity linked to vulnerability for stimulant addiction in rodents. Myoinositol and related signaling substrates may thus offer novel opportunities for treating neuropsychiatric disorders comorbid with impulsive symptomology.

Insular Cell Integrity Markers Linked to Weight Concern in Anorexia Nervosa-An MR-Spectroscopy Study

Objective: An insular involvement in the pathogenesis of anorexia nervosa (AN) has been suggested in many structural and functional neuroimaging studies. This magnetic resonance spectroscopy (MRS) study is the first to investigate metabolic signals in the anterior insular cortex in patients with AN and recovered individuals (REC). Method: The MR spectra of 32 adult women with AN, 21 REC subjects and 33 healthy controls (HC) were quantified for absolute N-acetylaspartate (NAA), glutamate + glutamine (Glx), total choline, myo-inositol, creatine concentrations (mM/L). After adjusting the metabolite concentrations for age and partial gray/white matter volume, group differences were tested using one-way multivariate analyses of variance (MANOVA). Post-hoc analyses of variance were applied to identify those metabolites that showed significant group effects. Correlations were tested for associations with psychometric measures (eating disorder examination), duration of illness, and body mass index. Results: The MANOVA exhibited a significant group effect. The NAA signal was reduced in the AN group compared to the HC group. The REC and the HC groups did not differ in metabolite concentrations. In the AN group, lower NAA and Glx signals were related to increased weight concern. Discussion: We interpret the decreased NAA availability in the anterior insula as a signal of impaired neuronal integrity or density. The association of weight concern, which is a core feature of AN, with decreased NAA and Glx indicates that disturbances of glutamatergic neurotransmission might be related to core psychopathology in AN. The absence of significant metabolic differences between the REC and HC subjects suggests that metabolic alterations in AN represent a state rather than a trait phenomenon.

Investigating the Role of Glutamate in Obsessive-Compulsive Disorder: Current Perspectives

Glutamate is a ubiquitous excitatory neurotransmitter, which is involved in normal physiology, a variety of central nervous system (CNS) functions, including excitotoxicity and neuronal migration. It is implicated in the pathogenesis of various neuropsychiatric disorders including epilepsy, Parkinson's disease, Alzheimer's dementia, schizophrenia and obsessive compulsive disorder (OCD). Over the years, a growing body of evidence has helped researchers understand the mechanisms underlying glutamatergic involvement in the pathogenesis of these disorders. In this review, we attempt to elucidate the role of glutamate in OCD, which is a chronic psychiatric condition with significant morbidity. This article provides current perspectives on the role played by glutamate in the pathogenesis, clinical symptoms and treatment response in OCD, a critical analysis of existing and emerging evidence, both clinical and preclinical, followed by a summary and future directions.

Magnetic resonance spectroscopy across chronic pain disorders: a systematic review protocol synthesising anatomical and metabolite findings in chronic pain patients

BACKGROUND

Chronic pain is pain greater than 3 months duration that may result from disease, trauma, surgery, or unknown origin. The overlap between the psychological, behavioural, and management aspects of pain suggest that limbic brain neurochemistry plays a role in chronic pain pathology. Proton magnetic resonance spectroscopy (1H-MRS) can evaluate in vivo brain metabolites including creatine, N-acetylaspartate, myo-inositol, choline, glutamate, glutamine, and gamma-aminobutyric acid in chronic pain; however, a comprehensive systemic review of metabolite expression patterns across all brain areas has yet to be performed.

METHODS AND ANALYSIS

Online databases including PubMed/MEDLINE, Google Scholar, EMBASE, the Cochrane Library, OVID, and PsycINFO will be searched for articles relating to 1H-MRS and chronic pain. Study inclusion criteria will include ages of between 18 and 65 years with a definite diagnosis of chronic pain, no comorbidities, clearly stated brain volumes of interest, and imaging protocols, with comparisons to healthy controls. Two reviewers will extract data relating to volumes of interest, metabolites, study participant demographics, diagnostic method and pain scores, treatments and duration of treatment, scanner information, 1H-MRS acquisition protocols, and spectral processing software. Where possible, volumes of interest will be reassigned as regions of interest consistent with known regional anatomical and functional properties to increase the power and relevance of the analysis. Statistical analyses will then be conducted using STATA. A central common pathway may exist for chronic pain due to the behavioural manifestations and management similarities between its different types. The goal of this systemic review is to generate a comprehensive neurochemical theory of chronic pain in different brain compartments.

SYSTEMATIC REVIEW REGISTRATION

This study is registered with PROSPERO CRD42018112640.

Distinct associations between fronto-striatal glutamate concentrations and callous-unemotional traits and proactive aggression in disruptive behavior

Disruptive behavior is associated with societally and personally problematic levels of aggression and has been linked to abnormal structure and function of fronto-amygdala-striatal regions. Abnormal glutamatergic signalling within this network may play a role in aggression. However, disruptive behavior does not represent a homogeneous construct, but can be fractionated across several dimensions. Of particular interest, callous-unemotional (CU) traits have been shown to modulate the severity, neural and behavioural characterisation, and therapeutic outcomes of disruptive behaviour disorders (DBDs) and aggression. Further, individuals showing disruptive behavior differ to the extent that they engage in subtypes of aggression (i.e., proactive [PA] and reactive aggression [RA]) which may also represent distinct therapeutic targets. Here we investigated how glutamate signalling within the fronto-amygdala-striatal circuitry was altered along these dimensions in youths showing disruptive behavior (n = 140) and typically developing controls (TD, n = 93) within the age-range of 8-18 years. We used proton magnetic resonance spectroscopy (¹H-MRS) in the anterior cingulate cortex (ACC), striatum, amygdala and insula and associated glutamate concentrations with continuous measures of aggression and CU-traits using linear mixed-effects models. We found evidence of a dissociation for the different measures and glutamate concentrations. CU traits were associated with increased ACC glutamate ('callousness': b = .19, t (108) = 2.63, p = .01, r = .25; 'uncaring': b = .18, t (108) = 2.59, p = .011, r = .24) while PA was associated with decreased striatal glutamate concentration (b = -.23, t (28) = -3.02, p = .005, r = .50). These findings suggest dissociable correlates of CU traits and PA in DBDs, and indicate that the ACC and striatal glutamate may represent novel pharmacological targets in treating these different aspects.

Psychosocial deficits across autism and schizotypal spectra are interactively modulated by excitatory and inhibitory neurotransmission

Continued human and animal research has strengthened evidence for aberrant excitatory-inhibitory neural processes underlying autism and schizophrenia spectrum disorder psychopathology, particularly psychosocial functioning, in clinical and nonclinical populations. We investigated the extent to which autistic traits and schizotypal dimensions were modulated by the interactive relationship between excitatory glutamate and inhibitory GABA neurotransmitter concentrations in the social processing area of the superior temporal cortex using proton magnetic resonance spectroscopy. In total, 38 non-clinical participants (20 females; age range = 18-35 years, mean (standard deviation) = 23.22 (5.52)) completed the autism spectrum quotient and schizotypal personality questionnaire, and underwent proton magnetic resonance spectroscopy to quantify glutamate and GABA concentrations in the right and left superior temporal cortex. Regression analyses revealed that glutamate and GABA interactively modulated autistic social skills and schizotypal interpersonal features (p_corr < 0.05), such that those with high right superior temporal cortex glutamate but low GABA concentrations exhibited poorer social and interpersonal skills. These findings evidence an excitation-inhibition imbalance that is specific to psychosocial features across the autism and schizophrenia spectra.

The Interaction of Person-Affect-Cognition-Execution (I-PACE) model for addictive behaviors: Update, generalization to addictive behaviors beyond internet-use disorders, and specification of the process character of addictive behaviors

We propose an updated version of the Interaction of Person-Affect-Cognition-Execution (I-PACE) model, which we argue to be valid for several types of addictive behaviors, such as gambling, gaming, buying-shopping, and compulsive sexual behavior disorders. Based on recent empirical findings and theoretical considerations, we argue that addictive behaviors develop as a consequence of the interactions between predisposing variables, affective and cognitive responses to specific stimuli, and executive functions, such as inhibitory control and decision-making. In the process of addictive behaviors, the associations between cue-reactivity/craving and diminished inhibitory control contribute to the development of habitual behaviors. An imbalance between structures of fronto-striatal circuits, particularly between ventral striatum, amygdala, and dorsolateral prefrontal areas, may be particularly relevant to early stages and the dorsal striatum to later stages of addictive processes. The I-PACE model may provide a theoretical foundation for future studies on addictive behaviors and clinical practice. Future studies should investigate common and unique mechanisms involved in addictive, obsessive-compulsive-related, impulse-control, and substance-use disorders.

Inhibitory control in BALB/c mice sub-strains during extinction learning

Dysregulation of executive function (EF) involves alterations in cognitive flexibility / control and is underscored by learning impairments in neurodevelopmental disorders. Here, we examine cognitive inflexibility in BALB/cJ mice (a mouse model showing diminished sociability, increased anxiety and inattentive behaviour) and closely related "reference" BALB/cByJ mice. We used an appetitive extinction paradigm to investigate if cognitive flexibility measures are different between learning acquisition and extinction. The two BALB/c sub-strains learned to respond to a stimulus in a touchscreen operant chamber, after which the reward was removed and responses should be inhibited. Both mice sub-strains showed a different rate of learning while acquiring the task, in which the BALB/cJ mice were faster learners compared to the BALB/cByJ mice. This was not observed during the extinction phase, in which the BALB/cJ mice were able to extinguish responding to unrewarded stimuli equally. Within the BALB/cJ sub-strain, variation in the ability to inhibit a learnt response was observed when comparing them to similar grouped BALB/cByJ mice: BALB/cJ animals that reached the criterion were more reward driven, while BALB/cJ mice failing to reach the set criterion during extinction processing make more mistakes. Additionally, the changes observed during acquisition, were driven by animals not reaching the extinction criterion. Our results suggest that the BALB/c mice sub-strains may use different strategies to learn during appetitive extinction. This may be useful in the phenotypic dissection of cognitive flexibility in BALB/c sub-strains and their mapping on genetic variance revealed by next-generation sequencing in future studies.

A comprehensive regional neurochemical theory in depression: a protocol for the systematic review and meta-analysis of 1H-MRS studies in major depressive disorder

BACKGROUND

Magnetic resonance spectroscopy (MRS) is a non-invasive analytical technique that investigates the presence and concentrations of brain metabolites. In the context of major depressive disorder (MDD), MRS has revealed regional biochemical changes in GABA, glutamate, and choline across different brain compartments. Technical and methodological advances in MRS data acquisition, in particular proton-based 1H-MRS, have resulted in a significant increase in the incidence of reports utilizing the technique for psychiatric disorder research and diagnosis. The most recent comprehensive meta-analysis reviewing MRS in MDD stems from 2006. Using contemporary systemic reviews and meta-analysis, the aim is to first test a neurochemical circuit-based theory of depression and then to determine if clinical scores relate to metabolite concentrations before and during treatment.

METHODS

Region-specific metabolite changes in MDD will be assessed by systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Inclusion criteria will include participant age (18 to 65), English language studies, known regions of interest, and detailed documentation of 1H-MRS procedures. Reported brain regions will be standardized according neuroanatomical expertise allowing increased power of the meta-analysis. Regions of interest will initially include the hippocampus, thalamus, prefrontal cortex, anterior and posterior cingulate gyri, parietal lobe, and basal ganglia. Exclusion criteria will include comorbid psychiatric illness and drug use. Two independent reviewers will undertake all data extraction, while a third reviewer will check for reviewer discrepancies. Statistical analysis will be performed using STATA supplemented by Metan software and SPSS.

DISCUSSION

This data will shed new light on the biochemical basis of depression in different brain regions, thereby highlighting the potential of MRS in identifying biomarkers and generating models of MDD and treatment response.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018091494.

Pharmacological management of behavioral disturbances in children and adolescents with autism spectrum disorders

Autism spectrum disorder (ASD) is a heterogeneous neuropsychiatric condition that, based on recent CDC estimates affects an estimated 1 in 59 American children. Behavioral treatments remain the mainstay of treatment for the core symptoms of ASD including communication deficits, social interaction deficits and repetitive behavior. However, youth with ASD may also have severe behavioral challenges including irritability, aggression, and hyperactivity. Currently there are only two medications (risperidone and aripiprazole) approved by the FDA for the treatment of irritability associated with ASD in children. Psychiatric comorbidities are common in youth with ASD, affecting up to 70% of affected children and adolescents. Given the burden of co-occurring disorders, medications are often employed to target symptoms such as irritability, anxiety, and hyperactivity. Other common co-occurring conditions including gastrointestinal disorders and sleep disorders may be improved with pharmacologic management. Evidence for the efficacy of many commonly used psychotropic medications in ASD is limited by the lack of large placebo-controlled trials in youth with ASD. This paper reviews the current literature regarding use of medications to address co-occurring conditions in children and adolescents with ASD as well as areas of emerging research.

l-Carnosine as Adjunctive Therapy in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

OBJECTIVES

This study aimed to investigate the efficacy and tolerability of l-carnosine as an add-on to methylphenidate in management of children with attention-deficit/hyperactivity disorder (ADHD).

METHODS

This was an 8-week, randomized, double-blind placebo-controlled study. Fifty-six drug-free children and adolescents aged 6-17 years old with a diagnosis of ADHD entered the study. The patients were randomly assigned to l-carnosine (800 mg/d in two divided doses) or placebo plus methylphenidate (0.5-1.5 mg/kg/d) for 8 weeks. Children were assessed using the Teacher and Parent ADHD Rating Scale-IV (ADHD-RS-IV) at baseline and at weeks 4 and 8 postbaseline.

RESULTS

Fifty patients completed the study, and all had two postbaseline measurements. Using the general linear model repeated measures, significant effect was observed for time × treatment interaction on total and inattention subscales of the Parent ADHD-RS (Greenhouse-Geisser corrected: F = 3.783, df = 1.444, p = 0.041 and F = 4.032, df = 1.600, p = 0.030). Improvements in the Teacher ADHD-RS were not significantly different between the two groups in total (Greenhouse-Geisser corrected: F = 0.200, df = 1.218, p = 0.705), as well as inattention and hyperactivity subscale scores (p = 0.956 and 0.281, respectively). The frequency of side effects was not significantly different between the two treatment arms.

CONCLUSIONS

l-carnosine, as a supplementary medication, might be beneficial in treatment of children with ADHD. However, further investigations and different doses of l-carnosine are required to replicate these findings in children with ADHD.

Prenatal paracetamol exposure and child neurodevelopment: A review

BACKGROUND

The non-prescription medication paracetamol (acetaminophen, APAP) is currently recommended as a safe pain and fever treatment during pregnancy. However, recent studies suggest a possible association between APAP use in pregnancy and offspring neurodevelopment.

OBJECTIVES

To conduct a review of publications reporting associations between prenatal APAP use and offspring neurodevelopmental outcomes.

METHODS

Relevant sources were identified through a key word search of multiple databases (Medline, CINAHL, OVID and TOXNET) in September 2016. All English language observational studies of pregnancy APAP and three classes of neurodevelopmental outcomes (autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and intelligence quotient (IQ)) were included. One reviewer (AZB) independently screened all titles and abstracts, extracted and analyzed the data.

RESULTS

64 studies were retrieved and 55 were ineligible. Nine prospective cohort studies fulfilled all inclusion criteria. Data pooling was not appropriate due to heterogeneity in outcomes. All included studies suggested an association between prenatal APAP exposure and the neurodevelopmental outcomes; ADHD, ASD, or lower IQ. Longer duration of APAP use was associated with increased risk. Associations were strongest for hyperactivity and attention-related outcomes. Little modification of associations by indication for use was reported.

CONCLUSIONS

Together, these nine studies suggest an increased risk of adverse neurodevelopmental outcomes following prenatal APAP exposure. Further studies are urgently needed with; precise indication of use and exposure assessment of use both in utero and in early life. Given the current findings, pregnant women should be cautioned against indiscriminate use of APAP. These results have substantial public health implications.

Could dietary glutamate be contributing to the symptoms of obsessive-compulsive disorder?

A 50-year-old man who had suffered from daily obsessive-compulsive disorder (OCD) symptoms for 39 years, in addition to fibromyalgia and irritable bowel syndrome symptoms, was enrolled in a randomized double-blind placebo-controlled clinical trial to test the effects of a low-glutamate diet on fibromyalgia/irritable bowel syndrome symptoms. After 1 month on the low-glutamate diet all of his symptoms remitted, including his OCD, which had previously been nonresponsive to pharmacological treatment. This case study is limited by self-report of symptoms; however, glutamatergic neurotransmission appears to be dysregulated in OCD, suggesting biological plausibility for this observation. Future research is needed.

Anterior cingulate cortex glutamate and its association with striatal functioning during cognitive control

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by structural, functional and neurochemical alterations of the fronto-striatal circuits and by deficits in cognitive control. In particular, ADHD has been associated with impairments in top-down fronto-striatal glutamate-signalling. However, it is unknown whether fronto-striatal glutamate is related to cognitive control dysfunction. Here we explored whether and how anterior cingulate cortex (ACC) glutamate relates to striatal BOLD-responses during cognitive control. We used proton magnetic resonance spectroscopy to evaluate glutamate-to-creatine ratios in 62 participants (probands with ADHD n=19, unaffected siblings n=24 and typical controls n=19, mean age=20.4). Spectra were collected from the ACC and the dorsal striatum and glutamate-to-creatine ratios were extracted. Thirty-two participants additionally took part in a functional magnetic resonance imaging (fMRI) Stroop task to investigate neural responses during cognitive control. Given small sample sizes we report all effects with p<0.10 along with effect sizes. ADHD subjects showed decreased glutamate-to-creatine ratios in the ACC (F=3.81, p=0.059, η_p²=0.104; medium to large effect-size) compared with controls. Importantly, decreased ACC glutamate-to-creatine ratios were associated with increased striatal BOLD-responses during cognitive control (rho=-0.41, p=0.019; medium effect-size), independent of diagnosis. Increased striatal responses tended to be associated with more errors during the task and more hyperactivity/impulsivity symptoms (rho=0.34, p=0.058 and rho=0.33, p=0.068, respectively); the latter two being correlated too (rho=0.37, p=0.037), all with medium effect sizes. Our results suggest that ACC glutamate in ADHD might be associated with striatal (dys)functioning during the Stroop task, supporting the role of fronto-striatal glutamate in cognitive control.

Fasoracetam in adolescents with ADHD and glutamatergic gene network variants disrupting mGluR neurotransmitter signaling

The glutamatergic neurotransmitter system may play an important role in attention-deficit hyperactivity disorder (ADHD). This 5-week, open-label, single-blind, placebo-controlled study reports the safety, pharmacokinetics and responsiveness of the metabotropic glutamate receptor (mGluR) activator fasoracetam (NFC-1), in 30 adolescents, age 12-17 years with ADHD, harboring mutations in mGluR network genes. Mutation status was double-blinded. A single-dose pharmacokinetic profiling from 50-800 mg was followed by a single-blind placebo at week 1 and subsequent symptom-driven dose advancement up to 400 mg BID for 4 weeks. NFC-1 treatment resulted in significant improvement. Mean Clinical Global Impressions-Improvement (CGI-I) and Severity (CGI-S) scores were, respectively, 3.79 at baseline vs. 2.33 at week 5 (P < 0.001) and 4.83 at baseline vs. 3.86 at week 5 (P < 0.001). Parental Vanderbilt scores showed significant improvement for subjects with mGluR Tier 1 variants (P < 0.035). There were no differences in the incidence of adverse events between placebo week and weeks on active drug. The trial is registered at https://clinicaltrials.gov/ct2/show/study/NCT02286817 .

Association between glutamate transporter gene polymorphisms and obsessive-compulsive disorder/trait empathy in a Korean population

Accumulating evidence suggests that the glutamatergic system plays a major role in the pathophysiology of obsessive compulsive disorder (OCD) and empathic processing. Particularly, genetic influence of glutamate transporter gene (SLC1A1) on OCD has been frequently replicated in previous studies, but several studies did not replicate the result. Therefore, we aimed to replicate the associations between the SLC1A1 and OCD in a Korean population. In addition, we investigated the influence of SLC1A1 on trait empathy, impairments in which are characteristic of OCD. Six single-nucleotide polymorphisms (SNP) of SLC1A1 were genotyped in 615 patients with OCD and 508 healthy controls. The interpersonal reactivity index (IRI)—which consists of four subscales (perspective taking, PT; fantasy seeking, FS; empathic concern, EC; personal distress, PD)—was assessed from 277 patients with OCD and 395 controls. There were no significant associations between OCD and SNPs or haplotypes of SLC1A1. Patients with OCD exhibited significantly lower PT and higher PD scores than controls. The C-T-G haplotype at rs301430-rs301434-rs3087879 of SLC1A1 was significantly associated with higher PD scores after adjusted for age, sex, and OCD status. Our results suggest that six common SNPs of SLC1A1 may not contribute to the development of OCD, but may contribute to certain aspect of trait empathy such as personal distress. However, insufficient sample size and limited number of SLC1A1 SNPs may have reduced the likelihood of detecting significant associations. Therefore, further studies with larger sample size and more tag SNPs of the SLC1A1 gene were warranted.

Striatal structure and its association with N-Acetylaspartate and glutamate in autism spectrum disorder and obsessive compulsive disorder

Autism spectrum disorders (ASD) and obsessive compulsive disorder (OCD) are often comorbid and are associated with changes in striatal volumes and N-Acetylaspartate (NAA) and glutamate levels. Here, we investigated the relation between dorsal striatal volume and NAA and glutamate levels. We additionally compared striatal volume and shape between ASD, OCD and controls. T1-weighted magnetic resonance (MR) images, proton spectra (1H-MRS) in the left striatum, and phenotypic information were collected from 54 children with ASD, 32 with OCD, and 56 controls (aged 8-13 years) in a four-site study. Dorsal striatal volume and shape were determined using the FMRIB integrated registration and segmentation tool (FIRST). Spectra were processed with Linear Combination Model. The relationship of left striatal volume with NAA and glutamate was investigated, and group comparisons were performed for NAA levels and for bilateral striatal volume and shape. NAA levels were lower in subjects with ASD compared with controls (t=2.86, p=0.005) and were associated with striatal volume (β=0.37, t=2.78, p=0.008). Glutamate levels were also associated with volume in the ASD group (β=0.38, t=2.46, p=0.018). No group differences were found for striatal volume or shape, but a post-hoc diagnosis-by-hemisphere interaction (F_(2,129)=3.86, p=0.024) revealed greater asymmetry (right>left) in striatal volume for the disorder-groups compared with controls. Our findings show involvement of NAA and glutamate in striatal volume in ASD and suggest greater asymmetry in paediatric ASD and OCD compared with controls, pointing to overlapping subcortical abnormalities. The lower NAA in ASD reflects reduced neuronal integrity or impaired neuronal functioning.