Double-Blind Placebo-Controlled Study of Memantine in Trichotillomania and Skin-Picking Disorder

OBJECTIVE

Trichotillomania and skin-picking disorder are underrecognized and often disabling conditions in which individuals repeatedly pull at their hair or pick at their skin, leading to noticeable hair loss or tissue damage. To date there is a severe paucity of evidence-based treatments for these conditions. In this study, the authors sought to determine whether memantine, a glutamate modulator, is more effective than placebo in reducing hair-pulling and skin-picking behavior.

METHODS

One hundred adults with trichotillomania or skin-picking disorder (86 women; mean age, 31.4 years [SD=10.2]) were enrolled in a double-blind trial of memantine (dosing range, 10-20 mg/day) or placebo for 8 weeks. Participants were assessed with measures of pulling and picking severity. Outcomes were examined using a linear mixed-effects model. The prespecified primary outcome measure was treatment-related change on the NIMH Trichotillomania Symptom Severity Scale, modified to include skin picking.

RESULTS

Compared with placebo, memantine treatment was associated with significant improvements in scores on the NIMH scale, Sheehan Disability Scale, and Clinical Global Impressions severity scale in terms of treatment-by-time interactions. At study endpoint, 60.5% of participants in the memantine group were "much or very much improved," compared with 8.3% in the placebo group (number needed to treat=1.9). Adverse events did not differ significantly between the treatment arms.

CONCLUSIONS

This study found that memantine treatment resulted in statistically significant reductions in hair pulling and skin-picking symptoms compared with placebo, with relatively high efficacy (based on number needed to treat), and was well tolerated. The glutamate system may prove to be a beneficial target in the treatment of compulsive behaviors.

Neurochemistry of Visual Attention

Visual attention is the cognitive process that mediates the selection of important information from the environment. This selection is usually controlled by bottom-up and top-down attentional biasing. Since for most humans vision is the dominant sense, visual attention is critically important for higher-order cognitive functions and related deficits are a core symptom of many neuropsychiatric and neurological disorders. Here, we summarize the importance and relative contributions of different neuromodulators and neurotransmitters to the neural mechanisms of top-down and bottom-up attentional control. We will not only review the roles of widely accepted neuromodulators, such as acetylcholine, dopamine and noradrenaline, but also the contributions of other modulatory substances. In doing so, we hope to shed some light on the current understanding of the role of neurochemistry in shaping neuron properties contributing to the allocation of attention in the visual field.

Association between prefrontal glutamine levels and neuroticism determined using proton magnetic resonance spectroscopy

There is growing evidence for GABA and glutamate-glutamine dysfunction in the pathogenesis of mood and anxiety disorders. It is important to study this pathology in the early phases of the illness in order to develop new approaches to secondary prevention. New magnetic resonance spectroscopy (MRS) measures allow determining glutamine, the principal metabolite of synaptic glutamate that is directly related to glutamate levels in the synaptic cleft, as well as glutamate and GABA. In contrast to previous investigations, this study used community-based recruitment methods and a combined categorical and dimensional approach to psychopathology. In the study protocol, neuroticism was defined as the primary outcome. Neuroticism shares a large proportion of its genetic variance with mood and anxiety disorders. We examined young adult participants recruited from the general population in a cross-sectional study using 3-T 1H-MRS with one voxel in the left dorsolateral prefrontal cortex (DLPFC). The total sample of N = 110 (61 females) included 18 individuals suffering from MDD and 19 individuals suffering from DSM-IV anxiety disorders. We found that glutamine and glutamine-to-glutamate ratio were correlated with neuroticism in the whole sample (r = 0.263, p = 0.005, and n = 110; respectively, r = 0.252, p = 0.008, and n = 110), even when controlling for depression and anxiety disorder diagnoses (for glutamine: beta = 0.220, p = 0.047, and n = 110). Glutamate and GABA were not significantly correlated with neuroticism (r = 0.087, p = 0.365, and n = 110; r = -0.044, p = 0.645, and n = 110). Lack of self-confidence and emotional instability were the clinical correlates of glutamate-glutamine dysfunction. In conclusion, this study suggests that prefrontal glutamine is increased in early phases of mood and anxiety disorders. Further understanding of glutamate-glutamine dysfunction in stress-related disorders may lead to new therapeutic strategies to prevent and treat these disorders.

Altered relationship between prefrontal glutamate and activation during cognitive control in people with high trait anxiety

Trait anxiety can affect cognitive control resulting in ineffective and/or inefficient task performance. Moreover, previous functional Magnetic Resonance Imaging (fMRI) studies have reported altered dorsolateral prefrontal cortex (DLPFC) activity in anxious cohorts, particularly when executive control is required. Recently, it has been demonstrated that cortical glutamate levels can predict both functional activation during cognitive control, and anxiety levels. In the present study we sought to investigate the relationship between trait anxiety, prefrontal glutamate levels and functional activation in DLPFC during a cognitive control task. Thirty-nine participants assigned to either low trait anxiety (LTA) or high trait anxiety (HTA) groups underwent ¹H-Magnetic Resonance Spectroscopy (¹H-MRS) to measure levels of resting glutamate in the prefrontal cortex (PFC). Participants also completed fMRI during a Stroop task comprising congruent and incongruent colour word trials. The HTA group showed reduced task performance relative to the LTA group. In the LTA group, there was a positive association between PFC Glu levels and DLPFC activation during incongruent trials. This association was absent in the HTA group. Individual differences in trait anxiety affect the relationship between PFC glutamate levels and DLPFC activation, possibly contributing to ineffective task performance when cognitive control is required.

Memantine in the Treatment of Executive Function Deficits in Adults With ADHD

OBJECTIVE

To evaluate the efficacy and safety of memantine hydrochloride as an adjunct to stimulant pharmacotherapy for treating executive function deficits (EFDs) in adults with ADHD.

METHOD

This was a 12-week, double-blind, placebo-controlled, randomized clinical trial of memantine added to open-label treatment with stimulant medication. Because of the small sample size, we considered a standardized mean difference (equivalent to effect size) of ≥0.5 and odds ratios ≥2 as indicators of trend improvements.

RESULTS

Twelve participants received memantine and 14 received a placebo. Trend improvements favoring memantine were observed on Behavior Rating Inventory of Executive Functions-Adult Inhibition and Self-Monitor subscales when compared with Placebo. No significant changes were noted on the Cambridge Neuropsychological Test Automated Battery.

CONCLUSION

Among adults with ADHD and EFDs, adjunct treatment with memantine to osmotic release oral system-methylphenidate (OROS-MPH) was associated with improvements in selective areas of executive functioning, supporting the need for further research.

Central conduction time in auditory brainstem response and ear advantage in dichotic listening across menstrual cycle

The ovarian hormones fluctuate during the menstrual cycle in women. Such fluctuation of sex hormones, in particular estrogen, is believed to affect the central conduction time in auditory function as well as the language lateralization in cognitive function. However, findings are inconsistent. The underlying mechanisms are also unclear. This paper examined if there was any relation between the central conduction time and the language lateralization at different times during the menstrual cycle. Twenty young women with normal menstrual cycle were tested four times (5 to 7 days apart) across the menstrual cycle. The test battery included the electrophysiological measurement of auditory evoked response in brainstem and the speech performance in dichotic listening with monosyllables as stimulus pairs. The dichotic listening task was conducted under the non-forced, forced-right and forced-left attention. The central conduction time was defined by the time elapsed between two auditory elicited responses along the auditory pathway. The language lateralization in dichotic listening was expressed in ear advantage, which was the right-ear score minus the left-ear score. The results showed that the effects of test time were significant on both the central conduction time and the ear advantage under the forced-left attention. Overall, the interaural difference in the central conduction time correlates with the ear advantage (non-forced attention) at the beginning of the menstrual cycle. The change in central conduction time between two test times correlates significantly with the change in ear advantage under the non-forced and forced-left attention. Conclusively, the central conduction time depends on the time during the menstrual cycle, which in turn may affect the performance in dichotic listening.

Similarities and Differences in Neurobiology

Substance addiction is a chronic, relapsing brain disease characterized by compulsive drug seeking and use despite harmful consequences. Non-substance addiction is defined recently that people may compulsively engage in an activity despite any negative consequences to their lives. Despite differences with respect to their addictive object, substance addiction and non-substance addiction may share similarities with respect to biological, epidemiological, clinical, genetic and other features. Here we review the similarities and differences in neurobiology between these two addictions with a focus on dopamine, serotonin, opioid, glutamate and norepinephrine systems. Studies suggest the involvement of all these systems in both substance addiction and non-substance addiction while differences may exist with respect to their contributions.

Memantine and Kynurenic Acid: Current Neuropharmacological Aspects

Glutamatergic neurotransmission, of special importance in the human brain, is implicated in key brain functions such as synaptic plasticity and memory. The excessive activation of N-methyl- D-aspartate (NMDA) receptors may result in excitotoxic neuronal damage; this process has been implicated in the pathomechanism of different neurodegenerative disorders, such as Alzheimer’s disease (AD). Memantine is an uncompetitive antagonist of NMDA receptors with a favorable pharmacokinetic profile, and is therefore clinically well tolerated. Memantine is approved for the treatment of AD, but may additionally be beneficial for other dementia forms and pain conditions. Kynurenic acid (KYNA) is an endogenous antagonist of NMDA receptors which has been demonstrated under experimental conditions to be neuroprotective. The development of a well-tolerated NMDA antagonist may offer a novel therapeutic option for the treatment of neurodegenerative disease and pain syndromes. KYNA may be a valuable candidate for future drug development.

Magnetic Resonance Spectroscopy in Alzheimer's Disease: Systematic Review and Meta-Analysis

BACKGROUND

The application of non-invasive proton magnetic resonance spectroscopy (1H-MRS) could potentially identify changes in cerebral metabolites in the patients with Alzheimer's disease (AD). However, whether these metabolites can serve as biomarkers for the diagnosis of AD remains unclear.

OBJECTIVE

Using meta-analysis, we aimed to investigate the patterns of cerebral metabolite changes in several cerebral regions that are strongly associated with cognitive decline in AD patients.

METHODS

Using Hedges' g effect size, a systematic search was performed in PubMed, Cochrane Library, Ovid, Embase, and EBSCO, and 38 studies were integrated into the final meta-analysis.

RESULTS

According to the observational studies, N-acetyl aspartate (NAA) in AD patients was significantly reduced in the posterior cingulate (PC) (effect size (ES) =-0.924, p <  0.005) and bilateral hippocampus (left hippocampus: ES =-1.329, p <  0.005; right hippocampus: ES =-1.287, p <  0.005). NAA/Cr (creatine) ratio decreased markedly in the PC (ES =-1.052, p <  0.005). Simultaneously, significant elevated myo-inositol (mI)/Cr ratio was found not only in the PC but also in the parietal gray matter. For lack of sufficient data, we failed to elucidate the efficacy of pharmacological interventions with the metabolites changes.

CONCLUSION

The available data indicates that NAA, mI, and the NAA/Cr ratio might be potential biomarkers of brain dysfunction in AD subjects. Choline (Cho)/Cr and mI/NAA changes might also contribute toward the diagnostic process. Thus, large, well-designed studies correlated with cerebral metabolism are needed to better estimate the cerebral extent of alterations in brain metabolite levels in AD patients.

Glutamate as a mediating transmitter for auditory hallucinations in schizophrenia: a (1)H MRS study

This is a (1)H MR spectroscopy (MRS) study of glutamate (Glu), measured as Glx, levels in temporal and frontal lobe regions in patients with schizophrenia compared with a healthy control group with the objective of revealing aspects of the underlying neurochemistry of auditory hallucinations. We further compared and correlated Glu(Glx) levels for the patients-only against frequency and severity of auditory hallucinations and the sum of Positive symptoms, and also for frequency and severity of emotional withdrawal, and sum of Negative symptoms. The sample included 23 patients with an ICD-10 and DSM-IV diagnosis of schizophrenia, and 26 healthy control subjects without any known psychiatric or neurological disorders. Symptom scores were obtained from the Positive and Negative Syndrome Scale (PANSS). (1)H MRS data were acquired on a 3T MR scanner from two temporal and two frontal voxels, using standard sequences and analysis parameters. The results showed that schizophrenia patients as a group had reduced Glu(Glx) levels in the voxels of interest compared to the healthy control subjects, while increased levels were found for patients with frequent and severe auditory hallucinations, relative to patients with less frequent and severe hallucination. We further found significant positive correlations between frequency and severity of auditory hallucinations, and for sum Positive symptoms, and Glu(Glx) levels in all regions, not seen when the analysis was done for negative symptoms. It is concluded that the results show for the first time that glutamate may be a mediating factor in auditory hallucinations in schizophrenia.

Changes in metabolites after treatment with memantine in fibromyalgia. A double-blind randomized controlled trial with magnetic resonance spectroscopy with a 6-month follow-up

AIM

To evaluate the efficacy of memantine on metabolite levels in different areas of the brain and to determine whether changes in metabolite levels correlate with clinical variables in Fibromyalgia (FM) patients.

METHODS

Doubled-blind parallel randomized controlled trial. Twenty-five patients diagnosed with FM were enrolled in the study. Patients were administered questionnaires on pain, anxiety, depression, quality of life, and cognitive impairment, and single-voxel MRS of the brain was performed. All assessments were performed at baseline and after 6 months of treatment with memantine or placebo.

RESULTS

Patients treated with memantine exhibited a significant increase in the glutamate (P = 0.010), glutamate/creatine ratio (P = 0.013), combined glutamate + glutamine (P = 0.016) and total N-acetyl-aspartate (NAA+NAAG) (P = 0.034) in the posterior cingulate cortex compared with those on placebo. Furthermore, the memantine group exhibited increases in creatine (P = 0.013) and choline (Cho) (P = 0.025) in the right posterior insula and also a correlation between choline and the Fibromyalgia Impact Questionnaire (FIQ) in the posterior insula (P = 0.050) was observed.

CONCLUSION

Memantine treatment resulted in an increase in cerebral metabolism in FM patients, suggesting its utility for the treatment of the illness.

Associations of regional GABA and glutamate with intrinsic and extrinsic neural activity in humans—a review of multimodal imaging studies

The integration of multiple imaging modalities is becoming an increasingly well used research strategy for studying the human brain. The neurotransmitters glutamate and GABA particularly lend themselves towards such studies. This is because these transmitters are ubiquitous throughout the cortex, where they are the key constituents of the inhibition/excitation balance, and because they can be easily measured in vivo through magnetic resonance spectroscopy, as well as with select positron emission tomography approaches. How these transmitters underly functional responses measured with techniques such as fMRI and EEG remains unclear though, and was the target of this review. Consistently shown in the literature was a negative correlation between GABA concentrations and stimulus-induced activity within the measured region. Also consistently found was a positive correlation between glutamate concentrations and inter-regional activity relationships, both during tasks and rest. These findings are outlined along with results from populations with mental disorders to give an overview of what brain imaging has suggested to date about the biochemical underpinnings of functional activity in health and disease. We conclude that the combination of functional and biochemical imaging in humans is an increasingly informative approach that does however require a number of key methodological and interpretive issues be addressed before can meet its potential.

Open label smoking cessation with varenicline is associated with decreased glutamate levels and functional changes in anterior cingulate cortex: preliminary findings

Rationale: Varenicline, the most effective single agent for smoking cessation, is a partial agonist at α4β2 nicotinic acetylcholine receptors. Increasing evidence implicates glutamate in the pathophysiology of addiction and one of the benefits of treatment for smoking cessation is the ability to regain cognitive control.

Objective: To evaluate the effects of 12-week varenicline administration on glutamate levels in the dorsal anterior cingulate cortex (dACC) and functional changes within the cognitive control network.

Methods: We used single-voxel proton magnetic resonance spectroscopy (¹H-MRS) in the dACC and functional MRI (fMRI) during performance of a Stroop color-naming task before and after smoking cessation with varenicline in 11 healthy smokers (open label design). Using the dACC as a seed region, we evaluated functional connectivity changes using a psychophysiological interaction (PPI) analysis.

Results: We observed a significant decrease in dACC glutamate + glutamine (Glx)/Cr levels as well as significant blood oxygen level-dependent signal (BOLD) decreases in the rostral ACC/medial orbitofrontal cortex and precuneus/posterior cingulate cortex. These BOLD changes are suggestive of alterations in default mode network (DMN) function and are further supported by the results of the PPI analysis that revealed changes in connectivity between the dACC and regions of the DMN. Baseline measures of nicotine dependence and craving positively correlated with baseline Glx/Cr levels.

Conclusions: These results suggest possible mechanisms of action for varenicline such as reduction in Glx levels in dACC and shifts in BOLD connectivity between large scale brain networks. They also suggest a role for ACC Glx in the modulation of behavior. Due to the preliminary nature of this study (lack of control group and small sample size), future studies are needed to replicate these findings.

Targeting the glutamatergic system to treat pathological gambling: current evidence and future perspectives

Pathological gambling or gambling disorder has been defined by the DSM-5 as a behavioral addiction. To date, its pathophysiology is not completely understood and there is no FDA-approved treatment for gambling disorders. Glutamate is the principal excitatory neurotransmitter in the nervous system and it has been recently involved in the pathophysiology of addictive behaviors. In this paper, we review the current literature on a class of drugs that act as modulating glutamate system in PG. A total of 19 studies have been included, according to inclusion and exclusion criteria. Clinical trial and case series using glutamatergic drugs (N-acetylcysteine, memantine, amantadine, topiramate, acamprosate, baclofen, gabapentin, pregabalin, and modafinil) will be presented to elucidate the effectiveness on gambling behaviors and on the related clinical dimensions (craving, withdrawal, and cognitive symptoms) in PG patients. The results have been discussed to gain more insight in the pathophysiology and treatment of PG. In conclusion, manipulation of glutamatergic neurotransmission appears to be promising in developing improved therapeutic agents for the treatment of gambling disorders. Further studies are required. Finally, we propose future directions and challenges in this research area.

The latest achievements in the pharmacotherapy of gambling disorder

Gambling disorder (GD) is becoming increasingly prevalent both among adults and adolescents. Unfortunately, this disorder is largely underestimated, while it can still lead to serious social and personal consequences, including criminal behavior or suicide attempts. In the past, the only means of treating gambling were psychobehavioral therapies. Nowadays, this disorder could also respond to many drugs from different classes such as opioid antagonists, serotonin selective reuptake inhibitors, mood stabilizers, atypical antipsychotics or glutamatergic agents. This review presents current pharmacological strategies and the results of clinical trials evaluating the efficacy of pharmacotherapy for GD. It also discusses the importance of distinguishing different pathological gambler subtypes such as impulsive, obsessive-compulsive and addictive subtypes as this may have serious pharmacological implications.

Improvement in subjective and objective neurocognitive functions in patients with major depressive disorder: a 12-week, multicenter, randomized trial of tianeptine versus escitalopram, the CAMPION study

Although many patients with major depressive disorder (MDD) complain of neurocognitive impairment, the effects of antidepressant medications on neurocognitive functions remain unclear. This study compares neurocognitive effects of tianeptine and escitalopram in MDD. Patients with MDD (N = 164) were randomly assigned in a 1:1 ratio to either tianeptine (37.5 mg/d) or escitalopram (10 mg/d) for 12 weeks. Outcome measures included clinical improvement, subjective cognitive impairment on memory and concentration, the Mini-Mental State Examination, the Continuous Performance Test, the Verbal Learning Test, and the Raven Progressive Matrices, assessed every 4 weeks. After 12 weeks, the tianeptine group showed significant improvement in commission errors (P = 0.002), verbal immediate memory (P < 0.0001), Mini-Mental State Examination (P < 0.0001), delayed memory (P < 0.0001), and reasoning ability (P = 0.0010), whereas the escitalopram group improved in delayed memory and reasoning ability but not in the other measures. Both groups significantly improved in subjective cognitive impairment in memory (P < 0.0001) and concentration (P < 0.0001). Mixed effects model repeated measures analyses revealed that the tianeptine group had a significant improvement in scores of commission errors (F = 6.64, P = 0.011) and verbal immediate memory (F = 4.39, P = 0.038) from baseline to 12 weeks, compared with the escitalopram group, after controlling for age, sex, education years, baseline scores, and changes of depression severity. The treatment of MDD with tianeptine led to more improvements in neurocognitive functions, especially in commission errors and verbal immediate memory, compared with escitalopram, after controlling for changes in depression severity. Both drugs improved subjective cognitive impairment of memory and concentration.

Proton magnetic resonance spectroscopy of the substantia nigra in schizophrenia

BACKGROUND

Converging evidence in schizophrenia points to disruption of the dopamine and glutamate neurotransmitter systems in the pathophysiology of the disorder. Dopamine is produced in the substantia nigra, but few neuroimaging studies have specifically targeted this structure. In fact, no studies of the substantia nigra in schizophrenia have used proton magnetic resonance spectroscopy (MRS). We sought to demonstrate the feasibility of acquiring single-voxel MRS measurements at 3T from the substantia nigra and to determine which metabolites could be reliably quantified in schizophrenia patients and healthy controls.

METHODS

We used a turbo spin echo sequence with magnetization transfer contrast to visualize the substantia nigra and single-voxel proton MRS to quantify levels of N-acetylaspartate, glutamate and glutamine (Glx), and choline in the left substantia nigra of 35 people with schizophrenia and 22 healthy controls.

RESULTS

We obtained spectra from the substantia nigra and quantified neurometabolites in both groups. We found no differences in levels of N-acetylaspartate/creatine, Glx/creatine, or choline/creatine between the groups. We found a significant correlation between Glx/creatine and overall cognitive performance, measured with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), in controls but not patients, a difference that was statistically significant.

CONCLUSIONS

Our study demonstrates the feasibility of obtaining single-voxel MRS data from the substantia nigra in schizophrenia. Such measurements may prove useful in understanding the biochemistry underlying cellular function in a region implicated in the pathophysiology of schizophrenia.

Neuropsychopharmacology of auditory hallucinations: insights from pharmacological functional MRI and perspectives for future research

Experiencing auditory verbal hallucinations is a prominent symptom in schizophrenia that also occurs in subjects at enhanced risk for psychosis and in the general population. Drug treatment of auditory hallucinations is challenging, because the current understanding is limited with respect to the neural mechanisms involved, as well as how CNS drugs, such as antipsychotics, influence the subjective experience and neurophysiology of hallucinations. In this article, the authors review studies of the effect of antipsychotic medication on brain activation as measured with functional MRI in patients with auditory verbal hallucinations. First, the authors examine the neural correlates of ongoing auditory hallucinations. Then, the authors critically discuss studies addressing the antipsychotic effect on the neural correlates of complex cognitive tasks. Current evidence suggests that blood oxygen level-dependant effects of antipsychotic drugs reflect specific, regional effects but studies on the neuropharmacology of auditory hallucinations are scarce. Future directions for pharmacological neuroimaging of auditory hallucinations are discussed.

Metabolic changes in the auditory cortex in presbycusis demonstrated by MR spectroscopy

In humans, aging is accompanied by the deterioration of the hearing function--presbycusis. The major etiology for presbycusis is the loss of hair cells in the inner ear; less well known are changes in the central auditory system. Therefore, we used 1H magnetic resonance spectroscopy at 3T tomograph to examine metabolite levels in the auditory cortex of three groups of subjects: young healthy subjects less than 30 years old and subjects older than 65 years either with mild presbycusis corresponding to their age or with expressed presbycusis. Hearing function in all subjects was examined by pure tone audiometry (125-16,000 Hz). Significant differences were found in the concentrations of glutamate and N-acetylaspartate, with lower levels in aged subjects. Lactate was particularly increased in subjects with expressed presbycusis. Significant differences were not found in other metabolites, including GABA, between young and elderly subjects. The results demonstrate that the age-related changes of the inner ear are accompanied by a decrease in the excitatory neurotransmitter glutamate as well as a lactate increase in the auditory cortex that is more expressed in elderly subjects with large hearing threshold shifts.

Language lateralization and cognitive control across the menstrual cycle assessed with a dichotic-listening paradigm

Lateralization has been shown to vary across the menstrual cycle, however, the underlying mechanisms are not fully understood, and results are inconsistent. Additionally, it has been suggested that estradiol enhances cognitive control. By modulating attention in a consonant-vowel dichotic listening test, the current study aims to investigate the effects of cycle-related changes on language lateralization (non-forced condition), as well as the effects of estradiol-modulated cognitive control (forced left condition) on the ear advantage. Fifteen women and fifteen men tested three times on the dichotic listening test, women once in menstrual, follicular, and luteal phase (verified by hormone assays). Whereas the results from the non-forced and forced-right condition remained stable, results from the forced left condition changed across the cycle, where women in the follicular phase compared to both menstrual and luteal phases showed a stronger left ear advantage, i.e. better cognitive control performance. The increase in performance from menstrual to follicular phase correlated negatively with increase in estradiol levels, indicating a shift from a stimulus-driven right ear advantage (indicating a left hemispheric asymmetry for language) when estradiol levels were low toward a cognitively controlled left ear advantage when estradiol levels were high. This finding strongly suggests an active role of estradiol on cognitive control. The study further suggests that the degree of cognitive control demands of a given task is important to consider when investigating lateralization across the menstrual cycle.

Autism spectrum disorder, functional MRI and MR spectroscopy: possibilities and challenges

Background

In this article we provide an overview of the use of the functional magnetic resonance imaging (fMRI) and MR spectroscopy (MRS) in studies of autism spectrum disorders (ASD). We moreover provide preliminary data using these measures in cases of children with ASD and healthy controls. A hypothesis was that ASD children would show aberrant brain activation in the prefrontal and parietal cortex in an oddball stimulus situation, with predictable and unpredictable deviant tone stimuli, as an index of resistance to change in the ASD children. We also hypothesized that glutamate and GABA metabolite levels would differ between the two groups.

Methods

fMRI images were acquired from a GE Signa HDx 3T MR scanner, as were the MRS data. Behavioral data were acquired as response accuracy to the deviant tone stimulus. The tone stimuli were presented in a standard fMRI ON-OFF box-car paradigim.

Results

The fMRI results showed reduced brain activation in the ASD cases compared to the controls, preferably in the inferior and superior frontal gyrus, posterior temporal lobe, and superior and inferior parietal lobule. These areas make up an effort mode network (EMN), being activated in response to cognitive effort. The MRS results also showed differences between the groups.

Discussion

The results are discussed in a theoretical framework of resistance to unexpected changes in the environment in ASD children, and how this could have a neurobiological underpinning. The results are also discussed in relation to the brain-gut link, and the possibility that ASD may have a microbial link. A limitation with the study is the few cases reported and the preliminary quality of the results.

Ketamine as a neuroprotective and anti-inflammatory agent in children undergoing surgery on cardiopulmonary bypass: a pilot randomized, double-blind, placebo-controlled trial

OBJECTIVE

Infants are potentially more susceptible to cell death mediated via glutamate excitotoxicity attributed to cardiopulmonary bypass. We hypothesized that ketamine, via N-methyl D-aspartate receptor blockade and anti-inflammatory effects, would reduce central nervous system injury during cardiopulmonary bypass.

METHODS

We randomized 24 infants, without chromosomal abnormalities, to receive ketamine (2 mg/kg, n = 13) or placebo (saline, n = 11) before cardiopulmonary bypass for repair of ventricular septal defects. Plasma markers of inflammation and central nervous system injury were compared at the end of surgery, and 6, 24, and 48 hrs after surgery. Magnetic resonance imaging and spectroscopy before cardiopulmonary bypass and at the time of hospital discharge were performed in a subset of cases and controls (n = 5 in each group). Cerebral hemodynamics were monitored postoperatively using near-infrared spectroscopy, and neurodevelopmental outcomes were assessed using Bayley Scales of Infant Development-II before and 2-3 wks after surgery.

RESULTS

Statistically significant differences were noted in preoperative inspired oxygen levels, intraoperative cooling and postoperative temperature, respiratory rate, platelet count, and bicarbonate levels. The peak concentration of C-reactive protein was lower in cases compared to controls at 24 hrs (p = .048) and 48 hrs (p = .001). No significant differences were noted in the expression of various cytokines, chemokines, S100, and neuron-specific enolase between the cases and controls. Magnetic resonance imaging with spectroscopy studies showed that ketamine administration led to a significant decrease in choline and glutamate plus glutamine/creatine in frontal white matter. No statistically significant differences occurred between pre- and postoperative Bayley Scales of Infant Development-II scores.

CONCLUSIONS

We did not find any evidence for neuroprotection or neurotoxicity in our pilot study. A large, adequately powered randomized control trial is needed to discern the central nervous system effect of ketamine on the developing brain. brain.

TRIAL REGISTRATION

The trial is registered at www.ClinicalTrials.gov, NCT00556361.

Resting-state glutamate level in the anterior cingulate predicts blood-oxygen level-dependent response to cognitive control

The dorsal anterior cingulate cortex (dACC) is a core structure for the governing of cognitive control, and recent studies have shown that interindividual differences in dACC anatomy are associated with corresponding differences in the ability for cognitive control. However, individuals differ not only in anatomical features of dACC, but also exhibit substantial variability regarding the biochemical characteristics of the dACC. In this study, we combined magnetic resonance spectroscopy ((1)H-MRS) and functional magnetic resonance imaging (fMRI), finding that interindividual differences of glutamate levels in the dACC during resting-state predict the strength of the blood-oxygen level-dependent (BOLD) response to a task requiring cognitive control. This relationship was observed in the retrosplenial cortex, the orbitofrontal cortex, the inferior parietal lobe, and the basal ganglia. More specifically, individuals with low resting-state glutamate levels in the dACC showed an increased BOLD response when the task demands were high, whereas high-glutamate individuals showed the opposite pattern of an increased BOLD response when the task demands were low. Thus, we show here that individual variability of glutamate levels is directly related to how the brain implements cognitive control.

Similarities and differences between pathological gambling and substance use disorders: a focus on impulsivity and compulsivity

RATIONALE

Pathological gambling (PG) has recently been considered as a "behavioral" or nonsubstance addiction. A comparison of the characteristics of PG and substance use disorders (SUDs) has clinical ramifications and could help advance future research on these conditions. Specific relationships with impulsivity and compulsivity may be central to understanding PG and SUDs.

OBJECTIVES

This review was conducted to compare and contrast research findings in PG and SUDs pertaining to neurocognitive tasks, brain function, and neurochemistry, with a focus on impulsivity and compulsivity.

RESULTS

Multiple similarities were found between PG and SUDs, including poor performance on neurocognitive tasks, specifically with respect to impulsive choice and response tendencies and compulsive features (e.g., response perseveration and action with diminished relationship to goals or reward). Findings suggest dysfunction involving similar brain regions, including the ventromedial prefrontal cortex and striatum and similar neurotransmitter systems, including dopaminergic and serotonergic. Unique features exist which may in part reflect influences of acute or chronic exposures to specific substances.

CONCLUSIONS

Both similarities and differences exist between PG and SUDs. Understanding these similarities more precisely may facilitate treatment development across addictions, whereas understanding differences may provide insight into treatment development for specific disorders. Individual differences in features of impulsivity and compulsivity may represent important endophenotypic targets for prevention and treatment strategies.

Variation in the NMDA receptor 2B subunit gene GRIN2B is associated with differential language lateralization

Variations in the N-methyl-d-aspartate receptor 2B subunit gene (GRIN2B) have been associated with schizophrenia, a psychiatric disorder associated with reduced left-hemispheric language dominance. Here, we investigated, whether different polymorphisms in GRIN2B influence language lateralization and handedness in healthy individuals. In a cohort of 424 genetically unrelated participants we found significant association between the synonymous GRIN2B variation rs1806201 and language lateralization assessed using the dichotic listening task. Individuals carrying the heterozygous CT genotype exhibited more pronounced left-hemispheric language dominance as compared to both homozygous CC and TT individuals. Such an association was not identified for handedness. These findings suggest that variation in NMDA-receptors contributes to the interindividual variability of language lateralization.

Adults with attention-deficit/hyperactivity disorder - a brain magnetic resonance spectroscopy study

BACKGROUND

Impaired cognitive control in individuals with attention-deficit/hyperactivity disorder (ADHD) may be related to a prefrontal cortical glutamatergic deficit. We assessed the glutamate level in the left and the right midfrontal region including the anterior cingulate cortex in adults with ADHD and healthy controls.

METHODS

Twenty-nine adults with ADHD and 38 healthy controls were included. We used Proton Magnetic Resonance Imaging with single voxel point-resolved spectroscopy to measure the ratio of glutamate to creatine (Glu/Cre) in the left and the right midfrontal region in the two groups.

RESULTS

The ADHD group showed a significant reduction of Glu/Cre in the left midfrontal region compared to the controls.

CONCLUSION

The reduction of Glu/Cre in the left midfrontal region in the ADHD group may reflect a glutamatergic deficit in prefrontal neuronal circuitry in adults with ADHD, resulting in problems with cognitive control.

Memantine shows promise in reducing gambling severity and cognitive inflexibility in pathological gambling: a pilot study

RATIONALE

Although pathological gambling (PG) is relatively common, pharmacotherapy research for PG is limited. Memantine, an N-methyl D-aspartate receptor antagonist, appears to reduce glutamate excitability and improve impulsive decision making, suggesting it may help individuals with PG.

OBJECTIVE

This study sought to examine the safety and efficacy of Memantine in PG.

METHODS

Twenty-nine subjects (18 females) with DSM-IV PG were enrolled in a 10-week open-label treatment study of memantine (dose ranging from 10 to 30 mg/day). Subjects were enrolled from January 2009 until April 2010. Change from baseline to study endpoint on the Yale Brown Obsessive Compulsive Scale Modified for Pathological Gambling (PG-YBOCS) was the primary outcome measure. Subjects underwent pre- and post-treatment cognitive assessments using the stop-signal task (assessing response impulsivity) and the intra-dimensional/extra-dimensional (ID/ED) set shift task (assessing cognitive flexibility).

RESULTS

Twenty-eight of the 29 subjects (96.6%) completed the 10-week study. PG-YBOCS scores decreased from a mean of 21.8 ± 4.3 at baseline to 8.9 ± 7.1 at study endpoint (p < 0.001). Hours spent gambling per week and money spent gambling both decreased significantly (p < 0.001). Subjects also demonstrated a significant improvement in ID/ED total errors (p = 0.037) at study endpoint. The mean effective dose of memantine was 23.4 ± 8.1 mg/day. The medication was well-tolerated. Memantine treatment was associated with diminished gambling and improved cognitive flexibility.

CONCLUSIONS

These findings suggest that pharmacological manipulation of the glutamate system may target both gambling and cognitive deficits in PG. Placebo-controlled, double-blind studies are warranted in order to confirm these preliminary findings in a controlled design.