Pharmacological Interventions for the MATRICS Cognitive Domains in Schizophrenia: What's the Evidence?

Gender differences in cognitive improvements after two months of atypical antipsychotic treatment in first episode schizophrenia

Aims

This study aims to explore the gender differences in cognitive improvements after two months of atypical antipsychotic treatment in first episode schizophrenia (FES).

Methods

82 patients with FES, including 50 male patients and 32 female patients, were enrolled in the present study. Positive and Negative Syndrome Scale (PANSS) and MATRICS Consensus Cognitive Battery (MCCB) were respectively conducted to evaluate the clinical symptoms and cognitive function of patients with FES at baseline and after treatment. Repeated measure ANOVA was performed to compare gender differences in cognitive domains scores between baseline and 2-month follow-up. Stepwise liner regression model was performed to explore the effect factors of cognitive improvements in patients.

Results

There was no significant difference in age of onset, education years, PANSS scores, duration of untreated psychosis and Olanzapine equivalent doses between male and female patients (all p > 0.05). In the comparisons of cognition function, male patients exhibited better performance in social cognition compared with female patients at baseline (t = 3.20, p < 0.05). After treatment, improvements of attention/vigilance and working memory were both found in male patients and female patients (attention/vigilance, F = 11.867, p < 0.05; working memory, F = 18.265, p < 0.05). In addition, improvement of speed of information processing was only found in female patients (F = 11.65, p < 0.01). Significant interaction between time and gender was found in speed information of processing (F = 4.140, p = 0.045). Stepwise liner regression model revealed that improvements of negative symptoms promote improvements of cognitive function in female patients (all p < 0.05).

Conclusions

Our findings revealed gender differences of cognitive improvements in patients with FES after 2-month treatment. It provides new evidence for gender differences in cognitive symptoms of schizophrenia, and also provides preliminary clues for further individualized cognitive intervention strategies.

Association of Alexithymia With Positive Symptoms in Chinese Chronic Schizophrenia Patients With and Without Obesity

OBJECTIVE

A growing body of research suggests the presence of alexithymia (a form of social cognitive impairment) in patients with schizophrenia (SCZ), which may be related to their psychopathological symptoms. Patients with SCZ exhibit high rates of obesity. Interestingly, studies of the general population have found that alexithymia acts a pivotal role in the development and maintenance of obesity. However, little is known regarding the relationship between obesity, alexithymia, and clinical symptoms in SCZ patients. The study was aim to explore the relationship between obesity, alexithymia, and clinical symptoms in SCZ patients.

METHODS

Demographic and clinical data were collected from 507 patients with chronic SCZ. Their symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS), and alexithymia was assessed with the Toronto Alexithymia Scale (TAS).

RESULTS

Compare with nonobese SCZ patients, obese SCZ patients scored higher on PANSS positive symptoms, TAS total score, difficulty identifying feelings, and difficulty describing feelings (all p<0.05). Correlation analysis revealed a significant association between difficulty identifying feelings and positive symptoms in SCZ patients. Further correlation analysis showed that this association was only present in obese SCZ patients (p<0.05).

CONCLUSION

Obesity may moderate the association between alexithymia and positive symptoms in chronic SCZ patients.

The role of the insula in cognitive impairment of schizophrenia

Cognitive impairment is one of the core clinical symptom domains of schizophrenia. Research shows that cognitive deficits in this neuropsychiatric syndrome is associated with neurodevelopmental pathology affecting multiple brain regions such as the dorsolateral prefrontal cortex, the hippocampus and the parietal lobe. The insula is a relatively small structure that is highly connected with several brain regions as well as multiple brain networks. A large number of studies have reported the involvement of the insula in many of the psychotic and nonpsychotic manifestations of schizophrenia. Here we review the role of the insula as a hub across key neurocircuits which have been implicated in the various cognitive pathologies in schizophrenia. Structural and functional abnormalities in the right and left insulae may serve as a biomarker for susceptibility to schizophrenia.

ARAS recent onset acute phase psychosis survey, a prospective observational cohort of first episode psychosis in Iran-the cohort profile

The Middle East is underrepresented in psychosis research. The ARAS recent onset acute phase psychosis survey (ARAS) is a longitudinal cohort across multiple centers in Iran, established to investigate characteristics, determinants and early course of psychosis in a non-Western, Middle East context. Here, baseline characteristics of the ARAS cohort are reported. The ARAS cohort enrolled patients with recent onset psychosis from September 2018 to September 2021 in East Azerbaijan, Kermanshah and Tehran, including Iranian patients from different sociocultural contexts. The baseline assessment included demographics, socioeconomic status, clinical (positive, negative, depressive symptoms) and psychosocial (religiosity, social support, self-stigma) characteristics, cognitive functioning, metabolic profile, substance use and medication use measured by validated questionnaires. These assessments will be followed up after one and five years. A total of 500 patients with a first episode of psychosis were enrolled from three provinces in Iran. With 74.1% being male, the mean age (SD) of patients was 32.3 (9.7) years. Nearly a quarter of patients was diagnosed with schizophrenia and 36.8% with substance induced psychotic disorder. Amphetamine (24%) and opium (12%) use were common, cannabis use was not (5%). Only 6.1% of patients lived alone while 29% of patients was married and had children. The majority of them had achieved secondary educational level and 34% had a paid job. The most common antipsychotic treatment was risperidone. There was a wide range for scores of PANSS, with 9.4% having dominant negative symptoms. The most common prescribed medication was risperidone. Near to 40% of patients had noticeable signs of depression and prevalence of metabolic syndrome was 13.4%. The majority of patients (57.2%) had moderate and 5.4% reported to have severe disability. More than 30% reported to be highly religious. Patients had the highest satisfaction with people living with, and the lowest for finance and job.

Prevalence, profile and associations of cognitive impairment in Ugandan first-episode psychosis patients

Introduction

The MATRICS consensus cognitive battery (MCCB) is the gold standard for neuropsychological assessment in psychotic disorders but is rarely used in low resource settings. This study used the MCCB to determine the prevalence, profile and associations of various exposures with cognitive impairment in Ugandan first-episode psychosis patients.

Methods

Patients and matched healthy controls were recruited at Butabika Hospital in Uganda. Clinical variables were first collated, and after the resolution of psychotic symptoms, a neuropsychological assessment of seven cognitive domains was performed using the MCCB. Cognitive impairment was defined as two standard deviations (SD) below the mean in one domain or 1SD below the mean in two domains. Descriptive statistics determined the prevalence and profile of impairment while regression models determined the association between various exposures with cognitive scores while controlling for age, sex and education.

Results

Neuropsychological assessment with the MCCB found the burden of cognitive impairment in first-episode psychosis patients five times that of healthy controls. The visual learning and memory domain was most impaired in first-episode psychosis patients, while it was the working memory domain for the healthy controls. Increased age was associated with impairment in the domains of the speed of processing (p < 0.001) and visual learning and memory (p = 0.001). Cassava-rich diets and previous alternative and complementary therapy use were negatively associated with impairment in the visual learning (p = 0.04) and attention/vigilance domains (p = 0.012), respectively. There were no significant associations between sex, history of childhood trauma, or illness severity with any cognitive domain.

Conclusion

A significant burden of cognitive impairment in Ugandan first-episode psychosis patients is consistent with prior data from other contexts. However, the profile of and risk factors for impairment differ from that described in such work. Therefore, interventions to reduce cognitive impairment in FEP patients specific to this setting, including dietary modifications, are required.

From the Clinic to the Laboratory, and Back Again: Investigations on Cannabinoids and Endocannabinoid System Modulators for Treating Schizophrenia

The present mini-review focuses on animal models of schizophrenia that have explored the effects of cannabidiol (CBD; a non-psychoactive component of cannabis) or the pharmacological manipulation of the endocannabinoid system on behavioral and cognitive outcome measures. First, results of some relevant clinical studies in this area are summarized, and then pre-clinical work on animal models of schizophrenia based on NMDA receptor antagonism or neurodevelopmental manipulations are discussed. A brief overview is given of the theoretical framework on which these models are based, along with a concise summary of results that have been obtained. Clinical results using CBD for schizophrenia seem promising and its effects in animal models of schizophrenia support its potential as a useful pharmacotherapy. Animal models have been paramount for elucidating the actions of CBD and the function of the endocannabinoid system and for identifying novel pharmacological targets, such as cannabinoid receptors and anandamide. However, more attention needs to be placed on defining and applying independent variables and outcome measures that are comparable between pre-clinical and clinical studies. The objective of this review is, on the one hand, to emphasize the potential of such models to predict clinical response to experimental drugs, and on the other hand, to highlight areas in which research on such models could be improved.

The genetic variations in SAP97 gene and the risk of schizophrenia in the Chinese Han population: a further study

BACKGROUND AND METHODS

Based on our previous discovery that SAP97 rs3915512 polymorphism significantly affects the cognitive function of schizophrenia, we further genotyped the other 12 single-nucleotide polymorphisms (SNPs) capturing the known common haplotype variations of this gene in a sample including 1014 patients with schizophrenia and 1078 matched controls.

RESULTS

There were no significant differences in the distribution of genotypes and alleles of the 12 SNPs of SAP97 between the patients and the controls (all P > 0.05). But, in the evaluation of the phenotypic effects of these SNPs on the patients' clinical symptoms and cognitive functions. While patients with minor allele in the rs9843659 polymorphism had higher N5 (difficulty in abstract thinking) scores than that with the main genotype (P = 0.002, Pcor = 0.014), the patients with minor allele in the rs6805920, rs4916461 and rs7638423 had lower verbal memory scores (P = 0.003, 0.003, 0.001, Pcor = 0.021, 0.021, 0.007, respectively) and the P values of these SNPs were still significant after the Bonferroni correction.

CONCLUSION

Our data are further to indicate that the SAP97 gene polymorphisms may affect neurocognitive function especially verbal memory and the first to suggest that the SAP97 rs9843659 polymorphism may influence abstract thinking of schizophrenic patients in the southern Han Chinese population.

Glutamatergic and GABAergic reactivity and cognition in 22q11.2 deletion syndrome and healthy volunteers: A randomized double-blind 7-Tesla pharmacological MRS study

AIMS

22q11.2 deletion syndrome (22q11.2DS) is associated with impaired cognitive functioning. Glutamatergic pathways have been linked with cognition and are hypothesized to be disrupted in 22q11.2DS patients, possibly 'shifting' the excitatory (glutamate)/inhibitory (GABA) balance. Hence, the glutamate/GABA balance may constitute a target for pharmacological treatment. We aimed to examine alterations of glutamate/GABA metabolites in 22q11.2DS in vivo using riluzole, a compound with glutamate/GABA-modulating action, as pharmacological challenge.

METHODS

Seventeen 22q11.2DS patients and 20 matched healthy controls were enrolled in this randomized double-blind placebo-controlled crossover study. Glutamate and glutamine concentrations in the anterior cingulate cortex (ACC) and striatum, as well as ACC GABA concentrations were obtained after placebo and after a single dose of 50 mg riluzole using 7-Tesla magnetic resonance spectroscopy (MRS). Within the 22q11.2DS group, the relationship between metabolite concentrations and cognition was examined.

RESULTS

No group differences were found in ACC and striatal metabolite concentrations following placebo. Riluzole numerically decreased ACC (η2= 0.094) but not striatal glutamate concentrations as well as ACC GABA concentrations (η2= 0.176) in all subjects. In both regions, riluzole did not alter glutamine concentration. No interaction effects were found. Although not significant after Bonferroni correction, ACC glutamate concentrations were inversely correlated with cognitive functions in 22q11.2DS patients.

DISCUSSION

We did not demonstrate altered ACC and striatal metabolite concentrations in 22q11.2DS. Nevertheless, these results suggest that glutamate and GABA can be modulated with a single dose of riluzole. Possibly, riluzole may have memory-enhancing effects in 22q11.2DS. Future studies should examine the long-term effects of riluzole on cognition.

Commentary: Composite cognitive and functional measures for early stage Alzheimer's disease trials

In this commentary I consider the issues raised in Schneider and Goldberg's review of composite cognitive and functional measures. I find much to agree with in their commentary and especially their concerns regarding satisfactory psychometric validation of composite measures. I endorse also their provision for analysis by cognitive domain, backed by the use of statistical methods for grouping test variables. The authors helpfully mention the possibility that treatment effects may be peculiar to specific domains of cognitive function. I develop this view and argue for exploratory studies of new therapeutic interventions to include broad assessments of the cognitive domains known to be compromised in early Alzheimer's disease. I suggest that the results of exploratory studies be used to help identify target domains for confirmatory studies. Finally, I note that computerized cognitive composite assessments have often been validated in the fashion that the authors recommend for composite measures.

Cognition and Related Neural Findings on Methamphetamine Use Disorder: Insights and Treatment Implications From Schizophrenia Research

Despite the prevalence of methamphetamine (meth) use disorder, research on meth is disproportionately scarce compared to research on other illicit drugs. Existing evidence highlights cognitive deficits as an impediment against daily function and treatment of chronic meth use. Similar deficits are also observed in schizophrenia, and this review therefore draws on schizophrenia research by examining similarities and differences between the two disorders on cognition and related neural findings. While meth use disorder and schizophrenia are two distinct disorders, they are highly co-morbid and share impairments in similar cognitive domains and altered brain structure/function. This narrative review specifically identifies overlapping features such as deficits in learning and memory, social cognition, working memory and inhibitory/impulse control. We report that while working memory deficits are a core feature of schizophrenia, such deficits are inconsistently observed following chronic meth use. Similar structural and functional abnormalities are also observed in cortical and limbic regions between the two disorders, except for cingulate activity where differences are observed. There is growing evidence that targeting cognitive symptoms may improve functional outcome in schizophrenia, with evidence of normalized abnormal brain activity in regions associated with cognition. Considering the overlap between meth use disorder and schizophrenia, targeting cognitive symptoms in people with meth use disorder may also improve treatment outcome and daily function.

Competence to Consent and Its Relationship With Cognitive Function in Patients With Schizophrenia

Decisional capacity to consent is an emerging ethical and legal concept, and is closely related to self-determination of patients facing important medical decisions or research participations. Recently, the MacArthur Competence Assessment Tool (MacCAT), a semi-structured interview consisting of four dimensions (Understanding, Appreciation, Reasoning, and Expression of a Choice), was developed to assess the decisional capacity. Decision-making capacity in a group of patients with schizophrenia, as measured by the MacCAT, has been shown to be impaired in comparison with healthy control people. However, this does not necessarily mean the presence of impaired decisional capacity in all cases. Considering the real-world practice of obtaining informed consent from patients with schizophrenia, it is important to evaluate the relationship between psychopathological features and decisional capacity of the illness. Negative symptoms of schizophrenia have been demonstrated to be related to the ability to understand information relevant to the decision, reason rationally, and appreciate a situation and its consequences. On the other hand, positive symptoms, such as delusions and hallucinations have been an inconsistent correlate of poor capacity. Furthermore, some studies indicate that impairment of cognitive function, a core symptom of schizophrenia, could be more largely associated with decisional capacity than positive and negative symptoms. Therefore, it is reasonable to assume cognitive enhancement would enlarge the capacity to consent and promote autonomy in medical treatment and research participation in patients with schizophrenia. Further studies are warranted to elucidate this and related issues.

Neurobiology and treatment of social cognition in schizophrenia: Bridging the bed-bench gap

Social cognition refers to the psychological processes involved in the perception, encoding, storage, retrieval, and regulation of information about others and ourselves. This process is essential for survival and reproduction in complex social environments. Recent evidence suggests that impairments in social cognition frequently occur in schizophrenia, mainly contributing to poor functional outcomes, including the inability to engage in meaningful work and maintain satisfying interpersonal relationships. With the ambiguous definition of social cognition, the neurobiology underlying impaired social cognition remains unknown, and the effectiveness of currently available intervention strategies in schizophrenia remain limited. Considering the advances and challenges of translational research for schizophrenia, social cognition has been considered a high-priority domain for treatment development. Here, we describe the current state of the framework, clinical concerns, and intervention approaches for social cognition in schizophrenia. Next, we introduce translatable rodent models associated with schizophrenia that allow the evaluation of different components of social behaviors, providing deeper insights into the neural substrates of social cognition in schizophrenia. Our review presents a valuable perspective that indicates the necessity of building bridges between basic and clinical science researchers for the development of novel therapeutic approaches in impaired social cognition in schizophrenia.

Relationship between muscarinic M1 receptor binding and cognition in medication-free subjects with psychosis

Background

It is still unclear which underlying mechanisms are involved in cognitive deficits of psychotic disorders. Pro-cognitive effects of muscarinic M1 receptor agonists suggest alterations in M1 receptor functioning may modulate these symptoms. Post mortem studies in patients with schizophrenia have shown significantly reduced M1 receptor expression rates in the dorsolateral prefrontal cortex (DLPFC) compared to controls. To date no in-vivo examinations of M1 receptor binding in relation to cognitive impairments have been done. As cognitive deficits have similar course and prognostic relevance across psychotic disorders, the current study assessed M1 receptor binding in the DLPFC and hippocampus in relation to cognitive functioning.

Methods

Muscarinic M1 receptor binding potential (BPND) was measured using 123I-IDEX, single photon emission computed tomography (SPECT) in 30 medication-free subjects diagnosed with a psychotic disorder. A computerized neuropsychological test battery was used to assess cognition, and the positive and negative syndrome scale (PANSS) to assess severity of psychotic symptoms.

Results

Assessment of cognitive domains showed that lower M1 BPND in the DLPFC was related to overall lower performance in verbal learning and memory. In addition, lower M1 BPND in the DLPFC was related to greater negative symptom severity. Lastly, lower M1 BPND in the hippocampus was related to worse delayed recognition of verbal memory.

Conclusion

This is the first study to show that variation in M1 receptors in the DLPFC is related to cognitive and negative symptom outcome in psychotic disorders. The M1 receptor may be an important biomarker in biological stratification of patients with psychotic disorders.

The effect of the muscarinic M1 receptor antagonist biperiden on cognition in medication free subjects with psychosis

The acetylcholine muscarinic M₁ receptor has been implicated in both psychosis and cognition. Post-mortem research has shown reduced muscarinic M₁ receptor density in 25% of chronic patients with schizophrenia. It is unknown whether reduced M₁ receptor density is related to cognitive symptoms of psychosis. We investigated the role of the M₁ receptor in separate cognitive domains in subjects with a psychotic disorder using a muscarinic M₁ antagonist as an acute pharmacological challenge. 33 young subjects with a psychotic disorder and 30 gender, age and IQ matched healthy controls were enrolled. All participants completed a comprehensive cognitive test battery twice: once after placebo and once after oral administration of 4mg. biperiden (M₁ antagonist). The order of drug administration was counterbalanced. Biperiden significantly negatively influenced both verbal (p< 0.001 and p=0.032) and visual learning and memory (p=0.028) in both groups. A medication x group interaction effect was found for reasoning and problem solving (p=0.005). No main or interaction effects were found for other cognitive domains. These results provide further in-vivo evidence that the M₁ receptor is involved in cognitive functioning, particularly verbal and visual memory processes. Lack of differential effects of biperiden between psychotic subjects and healthy controls may suggest that decreased M₁ receptor density is only present in chronic, older schizophrenia patients. However, it remains possible that differential effects of biperiden would be present in more severe cognitive impaired subjects with psychosis after several doses of biperiden instead of a single administration.

A review on the relationship between gluten and schizophrenia: Is gluten the cause?

INTRODUCTION

Schizophrenia is a chronic disease that possesses various clinical manifestations. It presents rather heterogeneous characteristics with respect to onset type, symptoms, and the course of the disease. Although the lifetime prevalence is as low as 1%, it can cause serious disability. Thus, it is very important to develop efficient treatment methods. In some studies, it is hypothesized that removing gluten from the diet leads to a significant improvement in disease symptoms. Epidemiological studies revealed that the prevalence of celiac disease among schizophrenic patients is almost two times higher than that of the general population.

OBJECTIVE

In this review, we evaluate the effects of gluten and celiac disease on the onset of schizophrenia. Efficacy of gluten-free diet applications, antibody response against gluten, and the interaction of the brain-gut axis and the presence of common genetic points are also investigated.

METHODS

Without any publication date restriction, Pubmed database searches were made for 'schizophrenia, gluten, gliadin, celiac disease, exorphin, brain-gut axis, psychiatric disorders.' The keywords and the articles about the schizophrenia-celiac disease relationship are included in our review.

RESULTS

Several studies presented evidence to suggest that symptoms associated with schizophrenia were minimized when gluten was excluded from patients' diets. Immunological searches revealed that most schizophrenic patients with increased anti-gliadin antibodies did not possess celiac disease; yet, the presence of increased antibodies against gliadin can be the share point of the immunological abnormalities found in both of the diseases.

DISCUSSION

There were no consistent results in the clinical, immunological, microbiological, and epidemiological studies that investigated the relationship between schizophrenia and celiac disease. This presents a need for a larger scale study to confirm the presence of this suggested correlation between schizophrenia and celiac disease. The underlying mechanisms between the two diseases should be explored.

MK-801-induced impairments on the trial-unique, delayed nonmatching-to-location task in rats: effects of acute sodium nitroprusside

RATIONALE

The cognitive symptoms observed in schizophrenia are not consistently alleviated by conventional antipsychotics. Following a recent pilot study, sodium nitroprusside (SNP) has been identified as a promising adjunct treatment to reduce the working memory impairments experienced by schizophrenia patients.

OBJECTIVE

The present experiments were designed to explore the effects of SNP on the highly translatable trial-unique, delayed nonmatching-to-location (TUNL) task in rats with and without acute MK-801 treatment.

METHODS

SNP (0.5, 1.0, 2.0, 4.0, and 5.0 mg/kg) and MK-801 (0.05, 0.075, and 0.1 mg/kg) were acutely administered to rats trained on the TUNL task.

RESULTS

Acute MK-801 treatment impaired TUNL task accuracy. Administration of SNP (2.0 mg/kg) with MK-801 (0.1 mg/kg) failed to rescue performance on TUNL. SNP (5.0 mg/kg) administration nearly 4 h prior to MK-801 (0.05 mg/kg) treatment had no preventative effect on performance impairments. SNP (2.0 mg/kg) improved performance on a subset of trials.

CONCLUSION

These results suggest that SNP may possess intrinsic cognitive-enhancing properties but is unable to block the effects of acute MK-801 treatment on the TUNL task. These results are inconsistent with the effectiveness of SNP as an adjunct therapy for working memory impairments in schizophrenia patients. Future studies in rodents that assess SNP as an adjunct therapy will be valuable in understanding the mechanisms underlying the effectiveness of SNP as a treatment for schizophrenia.

Developmental vitamin D deficiency and schizophrenia: the role of animal models

Schizophrenia is a debilitating neuropsychiatric disorder that affects 1% of the US population. Based on twin and genome-wide association studies, it is clear that both genetics and environmental factors increase the risk for developing schizophrenia. Moreover, there is evidence that conditions in utero, either alone or in concert with genetic factors, may alter neurodevelopment and lead to an increased risk for schizophrenia. There has been progress in identifying genetic loci and environmental exposures that increase risk, but there are still considerable gaps in our knowledge. Furthermore, very little is known about the specific neurodevelopmental mechanisms upon which genetics and the environment act to increase disposition to developing schizophrenia in adulthood. Vitamin D deficiency during the perinatal period has been hypothesized to increase risk for schizophrenia in humans. The developmental vitamin D (DVD) deficiency hypothesis of schizophrenia arises from the observation that disease risk is increased in individuals who are born in winter or spring, live further from the equator or live in urban vs. rural settings. These environments result in less exposure to sunlight, thereby reducing the initial steps in the production of vitamin D. Rodent models have been developed to characterize the behavioral and developmental effects of DVD deficiency. This review focuses on these animal models and discusses the current knowledge of the role of DVD deficiency in altering behavior and neurobiology relevant to schizophrenia.

COMT genotype is associated with differential expression of muscarinic M1 receptors in human cortex

Catechol-O-methyltransferase (COMT) genotype has been associated with varying levels of cognitive functioning and an altered risk of schizophrenia. COMT regulates the breakdown of catecholamines, particularly dopamine, which is thought critical in maintaining cognitive function and the aetiology of schizophrenia. This hypothesis gained support from reports that the VAL allele at rs4680 was associated with poorer performance on cognitive tests and a slightly increased risk of schizophrenia. More recently, genotype at rs4818, part of a hapblock with rs4680, has been shown to impact on cognitive ability more than genotype at rs4680 but, as yet, not the risk for schizophrenia. Here, we determined if COMT genotype at rs4680 or rs4818, as well as rs165519 and rs737865, two synonymous single nucleotide polymorphisms (SNPs) with no known functional consequences, were associated with an altered risk of schizophrenia and if genotype at the four COMT SNPs was related to expression of the cortical muscarinic M1 receptor (CHRM1) because the expression of the cortical CHRM1 has been reported to be lower in schizophrenia and is important in maintaining cognitive functioning in humans. We report that the variation in gene sequence at the four COMT SNPs studied was not associated with an altered the risk of schizophrenia but genotype at rs4680 and rs4818, but not rs165519 and rs737865, were associated with varying levels of cortical CHRM1 expression in the human dorsolateral prefrontal cortex (DLPFC). These data are the first to suggest that levels of CHRM1 in the human DLPFC are, in part, determined by COMT gene sequence. © 2016 Wiley Periodicals, Inc.

Effects of the metabotropic glutamate receptor 5 positive allosteric modulator CDPPB on rats tested with the paired associates learning task in touchscreen-equipped operant conditioning chambers

Effective treatments for the cognitive symptoms of schizophrenia are critically needed. Positive allosteric modulation (PAM) of metabotropic glutamate receptor subtype 5 (mGluR5) is one strategy currently under investigation to improve these symptoms. Examining cognition using touchscreen-equipped operant chambers may increase translation between preclinical and clinical research through analogous behavioral testing paradigms in rodents and humans. We used acute CDPPB (1-30mg/kg) treatment to examine the effects of mGluR5 PAM in the touchscreen paired associates learning (PAL) task using well-trained rats with and without co-administration of acute MK-801 (0.15mg/kg). CDPPB had no consistent effects on task performance when administered alone and failed to reverse the MK-801 induced impairments at any of the examined doses. Overall, the disruptive effects of MK-801 on PAL were consistent with previous research but increasing mGluR5 signaling is not beneficial in the PAL task. Future research should test whether administration of CDPPB during PAL acquisition increases performance.

Comparing the effects of subchronic phencyclidine and medial prefrontal cortex dysfunction on cognitive tests relevant to schizophrenia

RATIONALE

It is becoming increasingly clear that the development of treatments for cognitive symptoms of schizophrenia requires urgent attention, and that valid animal models of relevant impairments are required. With subchronic psychotomimetic agent phencyclidine (scPCP), a putative model of such impairment, the extent to which changes following scPCP do or do not resemble those following dysfunction of the prefrontal cortex is of importance.

OBJECTIVES

The present study carried out a comparison of the most common scPCP dosing regimen with excitotoxin-induced medial prefrontal cortex (mPFC) dysfunction in rats, across several cognitive tests relevant to schizophrenia.

METHODS

ScPCP subjects were dosed intraperitoneal with 5 mg/kg PCP or vehicle twice daily for 1 week followed by 1 week washout prior to behavioural testing. mPFC dysfunction was induced via fibre-sparing excitotoxin infused into the pre-limbic and infralimbic cortex. Subjects were tested on spontaneous novel object recognition, touchscreen object-location paired-associates learning and touchscreen reversal learning.

RESULTS

A double-dissociation was observed between object-location paired-associates learning and object recognition: mPFC dysfunction impaired acquisition of the object-location task but not spontaneous novel object recognition, while scPCP impaired spontaneous novel object recognition but not object-location associative learning. Both scPCP and mPFC dysfunction resulted in a similar facilitation of reversal learning.

CONCLUSIONS

The pattern of impairment following scPCP raises questions around its efficacy as a model of cognitive impairment in schizophrenia, particularly if importance is placed on faithfully replicating the effects of mPFC dysfunction.

Neuropsychological Impairment in Prodromal, First-Episode, and Chronic Psychosis: Assessing RBANS Performance

BACKGROUND

Cognitive deficits are observed throughout all developmental phases of psychosis. However, prior studies have usually focused on a limited illness period and used a wide variety of cognitive instruments. Therefore, it has been difficult to characterize or highlight cognitive functioning in different stages of psychosis.

METHOD

We administered the RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) tests to 4 participant subgroups, including healthy volunteers (controls, HC, n = 28), subjects at high risk for clinical psychosis (prodrome, CHR, n = 27), first-episode schizophrenia patients (FE-Sz, n = 26), and mid-term and long-term chronic schizophrenia patients (Ch-Sz, n =147). Comparison, correlation, and regression analyses of RBANS index scores were assessed among groups. We examined clinical outcomes over 2 years between the CHR and HC subjects, and RBANS domains were used as possible predictors for conversion to psychosis.

RESULTS

Performance on all RBANS domains was significantly impaired during a post-onset stage of psychosis (FE-Sz and Ch-Sz), and RBANS scores declined along with disease progression. Regression analyses showed that for CHR and HC subjects, baseline impairment in delayed memory (DM) significantly predicted conversion to psychosis. Additionally, partial correlations showed that for FE-Sz and Ch-Sz subjects, DM was the only correlate with a later stage of psychosis.

CONCLUSIONS

Cognitive deficits broadly emerged, and diminished functioning followed along with disease progression. Impairment in DM is perhaps one domain that helps us understand the development of psychosis. A critical need is to monitor and treat memory functioning for psychotic patients throughout all phases of the disease.

Kognitive Defizite bei Schizophren Erkrankten

Zusammenfassung. Theoretischer Hintergrund: Kognitive Funktionseinschränkungen sind zentrales Merkmal schizophrener Erkrankungen und werden entsprechend im Behandlungskonzept berücksichtigt. Kognitive Remediationsprogramme gelten als wirksam, Effektstärken als moderat. Trainingsvarianten werden zur Effektoptimierung erprobt. Fragestellung: Ist gezieltes Funktionstraining in neuroplastizitäts-orientiertem Lernkontext effektiver als breitgefächertes Behandlungsprogramm und werden Effekte durch das Erkrankungsstadium moduliert? Methode: Bei 59 chronisch und 31 ersthospitalisierten schizophren Erkrankten wurden kognitive Defizite über Testleistungen der MATRICS Consensus Cognitive Test Battery gegenüber 25 gesunder Kontrollpersonen erfasst. Testleistungen vor, nach 4-wöchiger Interventionsphase mit zwei spezifischen Trainings oder Standardbehandlung und 3-monatiger Katamnese prüften den Einfluss von Interventionstypus und Erkrankungsstadium auf Leistungsverbesserung. Ergebnisse: Sowohl chronische wie erstmals behandelte Patienten aller Behandlungsgruppen verbesserten sich signifikant über die Messzeitpunkte, obwohl Defizite relativ zu Kontrollen fortbestanden. Schlussfolgerungen: Spezifisches Training verbessert kognitive Funktionen nicht über Zeit/Remissionseffekte hinaus.

Neurocognitive effects of acute choline supplementation in low, medium and high performer healthy volunteers

Novel pharmacological treatments targeting alpha 7 nicotinic acetylcholine receptor (α7 nAChR) hypofunction in schizophrenia have shown mixed success in ameliorating cognitive impairments associated with this disorder. Choline, a selective agonist at α7 receptors is increased with oral administration of cytidine 5'-diphosphocholine (CDP-choline), the cognitive effects of which were assessed in healthy volunteers. Using the CogState test battery, behavioral performance in schizophrenia-relevant cognitive domains was assessed in 24 male participants following a single low (500mg) and moderate (1000mg) dose of CDP-choline. Relative to placebo, CDP-choline improved processing speed, working memory, verbal learning, verbal memory, and executive function in low baseline performers, while exerting no effects in medium baseline performers, and diminishing cognition in high baseline performers. Dose effects varied with cognitive domain but were evident with both the 500mg and 1000mg doses. These preliminary findings of cognitive enhancement in relatively impaired performers are consistent with the α7 receptor mechanism and support further trials with CDP-choline as a potential pro-cognitive strategy for cognitive impairment in schizophrenia.

Dementia praecox redux: a systematic review of the nicotinic receptor as a target for cognitive symptoms of schizophrenia

Most individuals with schizophrenia suffer some cognitive dysfunction: such deficits are predictive of longer-term functioning; and current dopamine-blocking antipsychotics have made little impact on this domain. There is a pressing need to develop novel pharmacological agents to tackle this insidious but most disabling of problems. The acetylcholinergic system is involved in cognitive and attentional processing, and its metabotropic and nicotinic receptors are widespread throughout the brain. Deficits in acetylcholinergic functioning occur in schizophrenia, and high rates of tobacco smoking have been posited to represent a form of self-medication. The nicotinic acetylcholine receptor (nAChR) has emerged as a putative target to improve cognitive deficits in schizophrenia, and this study systematically reviewed the emerging data. Nineteen studies were identified, covering three compound classes: agonists at the α7 and α 4β2 nAChRs, and positive allosteric modulators. Overall data are underwhelming: some studies showed significant improvements in cognition but as many studies had negative findings. It remains unclear if this represents drug limitations or nascent study methodology problems. The literature is particularly hindered by variability in inclusion of smokers, generally small sample sizes, and a lack of consensus on cognitive test batteries. Future work should evaluate longer-term outcomes, and, particularly, the effects of concomitant cognitive training.

Prefrontal dopamine in associative learning and memory

Learning to associate specific objects or actions with rewards and remembering the associations are everyday tasks crucial for our flexible adaptation to the environment. These higher-order cognitive processes depend on the prefrontal cortex (PFC) and frontostriatal circuits that connect areas in the frontal lobe with the striatum in the basal ganglia. Both structures are densely innervated by dopamine (DA) afferents that originate in the midbrain. Although the activity of DA neurons is thought to be important for learning, the exact role of DA transmission in frontostriatal circuits during learning-related tasks is still unresolved. Moreover, the neural substrates of this modulation are poorly understood. Here, we review our recent work in monkeys utilizing local pharmacology of DA agents in the PFC to investigate the cellular mechanisms of DA modulation of associative learning and memory. We show that blocking both D1 and D2 receptors in the lateral PFC impairs learning of new stimulus-response associations and cognitive flexibility, but not the memory of highly familiar associations. In addition, D2 receptors may also contribute to motivation. The learning deficits correlated with reductions of neural information about the associations in PFC neurons, alterations in global excitability and spike synchronization, and exaggerated alpha and beta neural oscillations. Our findings provide new insights into how DA transmission modulates associative learning and memory processes in frontostriatal systems.

Neural Substrates of Dopamine D2 Receptor Modulated Executive Functions in the Monkey Prefrontal Cortex

Dopamine D2 receptors (D2R) play a major role in cognition, mood and motor movements. Their blockade by antipsychotic drugs reduces hallucinatory and delusional behaviors in schizophrenia, but often fails to alleviate affective and cognitive dysfunctions. The prefrontal cortex (PFC) expresses D2R and is altered in schizophrenia. We investigated how D2R modulate behavior and PFC function in monkeys. Two monkeys learned new and performed highly familiar visuomotor associations, where each cue was associated with a saccade to a right or left target. We recorded neural spikes and local field potentials from multiple electrodes while injecting the D2R antagonist eticlopride in the lateral PFC. Blocking prefrontal D2R impaired associative learning and cognitive flexibility, reduced motivation, but left the performance of familiar associations intact. Eticlopride reduced saccade-direction selectivity of prefrontal neurons, leading to a decrease in neural information about the associations, and an increase in alpha oscillations. These results, together with our recent study using a D1R antagonist, suggest that D1R and D2R in the primate lateral PFC cooperate to modulate several executive functions. Our findings help to gain insight into why antipsychotic drugs, with strong antagonistic actions on D2R, fail to ameliorate cognitive and emotional deficits in schizophrenia.