A review of molecular genetic studies of neurocognitive deficits in schizophrenia

Dissecting Schizotypy and Its Association With Cognition and Polygenic Risk for Schizophrenia in a Nonclinical Sample

Schizotypy is a multidimensional construct that captures a continuum of risk for developing schizophrenia-spectrum psychopathology. Existing 3-factor models of schizotypy, consisting of positive, negative, and disorganized dimensions have yielded mixed evidence of genetic continuity with schizophrenia using polygenic risk scores. Here, we propose an approach that involves splitting positive and negative schizotypy into more specific subdimensions that are phenotypically continuous with distinct positive symptoms and negative symptoms recognized in clinical schizophrenia. We used item response theory to derive high-precision estimates of psychometric schizotypy using 251 self-report items obtained from a non-clinical sample of 727 (424 females) adults. These subdimensions were organized hierarchically using structural equation modeling into 3 empirically independent higher-order dimensions enabling associations with polygenic risk for schizophrenia to be examined at different levels of phenotypic generality and specificity. Results revealed that polygenic risk for schizophrenia was associated with variance specific to delusional experiences (γ = 0.093, P = .001) and reduced social interest and engagement (γ = 0.076, P = .020), and these effects were not mediated via the higher-order general, positive, or negative schizotypy factors. We further fractionated general intellectual functioning into fluid and crystallized intelligence in 446 (246 females) participants that underwent onsite cognitive assessment. Polygenic risk scores explained 3.6% of the variance in crystallized intelligence. Our precision phenotyping approach could be used to enhance the etiologic signal in future genetic association studies and improve the detection and prevention of schizophrenia-spectrum psychopathology.

Illness Phase as a Key Assessment and Intervention Window for Psychosis

The phenotype of schizophrenia, regardless of etiology, represents the most studied psychotic disorder with respect to neurobiology and distinct phases of illness. The early phase of illness represents a unique opportunity to provide effective and individualized interventions that can alter illness trajectories. Developmental age and illness stage, including temporal variation in neurobiology, can be targeted to develop phase-specific clinical assessment, biomarkers, and interventions. We review an earlier model whereby an initial glutamate signaling deficit progresses through different phases of allostatic adaptation, moving from potentially reversible functional abnormalities associated with early psychosis and working memory dysfunction, and ending with difficult-to-reverse structural changes after chronic illness. We integrate this model with evidence of dopaminergic abnormalities, including cortical D1 dysfunction, which develop during adolescence. We discuss how this model and a focus on a potential critical window of intervention in the early stages of schizophrenia impact the approach to research design and clinical care. This impact includes stage-specific considerations for symptom assessment as well as genetic, cognitive, and neurophysiological biomarkers. We examine how phase-specific biomarkers of illness phase and brain development can be incorporated into current strategies for large-scale research and clinical programs implementing coordinated specialty care. We highlight working memory and D1 dysfunction as early treatment targets that can substantially affect functional outcome.

Toxoplasma gondii seropositivity and cognitive function in adults with schizophrenia

Introduction and methods

Based on the limited research focusing on the severity of cognitive deterioration in schizophrenia with preceding toxoplasmosis, we sampled 89 demographically matched paranoid schizophrenia patients (mean age 38.97 years) with (n = 42) and without (n = 47) seroprevalence of IgG type anti T. gondii antibodies as marker of past infection. They underwent examination of verbal memory (10 words Luria test), logical memory and visual memory (BVRT), processing speed (TMT-A/DSST) and executive functions (TMT-B/verbal fluency). We compared the results of both groups, taking into account the normative values for the Bulgarian population where available. We also compared the two groups in terms of clinical severity as evidenced by positive, negative and disorganization sub-scores of the PANSS.

Results

While both groups were expectedly under the population norms for verbal and logical memory, seropositive patients showed significantly bigger impairment in verbal memory (Luria Smax = 72.85 vs 78.51; p = 0.029), psychomotor speed (TMT-A 50.98 s vs 44.64 s; p = 0.017), semantic verbal fluency (27.12 vs 30.02; p = 0.011) and literal verbal fluency (17.17 vs 18.78; p = 0.014) compared to the seronegative ones. In addition to that, they gave less correct answers on the BVRT (2.98 vs 4.09; p = 0.006) while making markedly more errors (13.95 vs 10.21; p = 0.002). Despite not reaching statistical significance, past toxoplasmosis was associated with higher score on the PANSS disorganization sub-scale (16.50 points vs 14.72 points) and with lower educational attainment.

Conclusion

Our results suggest a more profound neuropathological insult(s) resulting in greater cognitive impairment in schizophrenia cases that are exposed to T. gondii infection.

A polymorphism in the glutamate metabotropic receptor 7 is associated with cognitive deficits in the early phases of psychosis

Schizophrenia is an illness characterized by positive symptoms, negative symptoms, and cognitive impairments. Cognitive impairments occur before the onset of psychosis and could reflect glutamatergic dysregulation. Thus, identifying associations between genetic variations in genes coding for glutamatergic receptors and cognitive impairment in schizophrenia may help in understanding the basis of these deficits and in identifying potential drug targets. In a discovery cohort of 144 first-episode of psychosis patients (FEP), we genotyped 58 candidate Single Nucleotide Polymorphisms (SNPs) located in NMDA and metabotropic glutamatergic receptors. These SNPs were selected according to the results from the Psychiatric Genomic Consortium and were tested for association with intellectual quotient (IQ) as assessed with the Wechsler Intelligence Scales. For replication, we used the ICAAR cohort including 121 ultra-high-risk patients (UHR) with the same cognitive assessment. A polymorphism located in GRM7, rs1396409, was significantly associated with performance IQ in the discovery cohort of FEP. This association was replicated in the UHR cohort. This polymorphism is also associated with total IQ and verbal IQ in the merged dataset, with a predominant effect on the arithmetic subtest. The rs1396409 polymorphism is significantly associated with cognitive impairment during the onset of psychosis. This genetic association highlights the possible impact of glutamatergic genes in cognitive deficits in the early phases of psychosis and enforces the interest for new therapeutic interventions targeting the glutamatergic pathway.

Association of Polymorphism within the Putative miRNA Target Site in the 3'UTR Region of the DRD2 Gene with Neuroticism in Patients with Substance Use Disorder

The study aims at looking into associations between the polymorphism rs6276 that occurs in the putative miRNA target site in the 3'UTR region of the DRD2 gene in patients with substance use disorder (SUD) comorbid with a maniacal syndrome (SUD MANIA). In our study, we did not state any essential difference in DRD2 rs6276 genotype frequencies in the studied samples of SUD MANIA, SUD, and control subjects. A significant result was found for the SUD MANIA group vs. SUD vs. controls on the Neuroticism Scale of NEO FFI test, and DRD2 rs6276 (p = 0.0320) accounted for 1.7% of the variance. The G/G homozygous variants were linked with lower results on the neuroticism scale in the SUD MANIA group because G/G alleles may serve a protective role in the expression of neuroticism in patients with SUD MANIA. So far, there have been no data in the literature on the relationship between the miRSNP rs6276 region in the DRD2 gene and neuroticism (personal traits) in patients with a diagnosis of substance use disorder comorbid with the affective, maniacal type disturbances related to SUD. This is the first report on this topic.

Association of NKAPL rs1635 With Cognitive Function in Early-Onset Schizophrenia

BACKGROUND: Schizophrenia is a severe mental disorder with high heritability, and cognitive dysfunction is one of the core features. Growing evidence suggests the genetic risk of schizophrenia may contribute to cognitive impairments. The variant rs1635 (nucleotide sequence: c.455C>A; amino acid sequence: T152N) located on the (NFKB activating protein like) NKAPL gene confers risk for schizophrenia and might play a role in the neurodevelopmental process, which is particularly relevant to cognitive function. However, the relationship between rs1635 and cognitive function remains unclear.

METHODS: A total of 130 patients with early-onset schizophrenia (EOS) and 300 patients with adult-onset schizophrenia (AOS) of Han Chinese were recruited and underwent neurocognitive tests by using the MATRICS Consensus Cognitive Battery (MCCB). The NKAPL rs1635 was genotyped by using DNA sequencing. The peripheral blood NKAPL mRNA expression level was examined in 152T or 152N carriers (n = 20) in EOS patients, by using the qRT-PCR. The phosphorylation level of NAKPL T152N polymorphism was detected by cell experiments. In utero electroporation of mouse embryos was examined to explore the effect of Nkapl on neuronal migration.

RESULTS: Compared with rs1635 AA and AC carriers, CC (the CC genotype encodes the protein NKAPL-152T) carriers of EOS patients performed better in cognitive domain of speed of processing (t = 2.644, p = 0.009), trail making test (t = 2.221, p = 0.028) and category fluency (t = 2.578, p = 0.011). However, patients with AOS exhibited no significant differences in seven domains among the three genotype groups. There were no significant differences in cognitive performance between EOS and AOS. In EOS patients, NKAPL mRNA level in NKAPL-152N carriers is significantly lower than that of NKAPL-152T carriers. The phosphorylation level of NKAPL-152N is significantly decreased compared to NKAPL-152T. In utero electroporation showed that Nkapl deletion impairs the embryonic radial migration process.

CONCLUSION: The present study found that NKAPL rs1635 was associated with cognitive impairments and peripheral blood mRNA expression level in EOS patients. The NKAPL full-length protein is required for embryonic cortical neuronal migration. The phosphorylation level of NKAPL-152N is significantly decreased. The NKAPL T152N may affect the NAKPL mRNA expression level and embryonic cortical neuronal migration by regulating the NAKPL protein phosphorylation. These data suggest that NKAPL rs1635 affects cognitive function by regulating early brain development in early-onset schizophrenia.

White matter microstructure and the clinical risk for psychosis: A diffusion tensor imaging study of individuals with basic symptoms and at ultra-high risk

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This DTI cross-sectional study compared UHR, basic symptom & control groups (n = 112).

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The splenium of UHR individuals exhibited differences in fractional anisotropy (FA).

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Basic symptoms alone were not associated with white matter microstructure changes.

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Large differences in FA & radial diffusivity were found in converters to psychosis.

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Regional FA was inversely correlated with the general psychopathology domain.

Background

Widespread white matter abnormalities are a frequent finding in chronic schizophrenia patients. More inconsistent results have been provided by the sparser literature on at-risk states for psychosis, i.e., emerging subclinical symptoms. However, considering risk as a homogenous construct, an approach of earlier studies, may impede our understanding of neuro-progression into psychosis.

Methods

An analysis was conducted of 3-Tesla MRI diffusion and symptom data from 112 individuals (mean age, 21.97 ± 4.19) within two at-risk paradigm subtypes, only basic symptoms (n = 43) and ultra-high risk (n = 37), and controls (n = 32). Between-group comparisons (involving three study groups and further split based on the subsequent transition to schizophrenia) of four diffusion-tensor-imaging-derived scalars were performed using voxelwise tract-based spatial statistics, followed by correlational analyses with Structured Interview for Prodromal Syndromes responses.

Results

Relative to controls, fractional anisotropy was lower in the splenium of the corpus callosum of ultra-high-risk individuals, but only before stringent multiple-testing correction, and negatively correlated with General Symptom severity among at-risk individuals. At-risk participants who transitioned to schizophrenia within 3 years, compared to those that did not transition, had more severe WM differences in fractional anisotropy and radial diffusivity (particularly in the corpus callosum, anterior corona radiata, and motor/sensory tracts), which were even more extensive compared to healthy controls.

Conclusions

These findings align with the subclinical symptom presentation and more extensive disruptions in converters, suggestive of severity-related demyelination or axonal pathology. Fine-grained but detectable differences among ultra-high-risk subjects (i.e., with brief limited intermittent and/or attenuated psychotic symptoms) point to the splenium as a discrete site of emerging psychopathology, while basic symptoms alone were not associated with altered fractional anisotropy.

The inconsistent mediating effect of catechol O methyl transferase Val158Met polymorphism on the sex difference of cognitive impairment in schizophrenia patients

OBJECTIVE

Schizophrenia is a multifaceted mental disorder characterized by heterogeneous positive/negative symptoms and cognitive deficits. Sex differences have been reported in various aspects of the disease. However, the underlying genetic reasons remain unelucidated. Recent studies show that the influence of COMT Val158Met (rs4680) variation is sexually dimorphic. Thus, this study aims to explore whether there is an effect of the interaction between COMT Val158Met (rs4680) polymorphism and sex on patients' clinical characteristics and cognitive function.

MATERIALS AND METHODS

We recruited 367 in patients with chronic schizophrenia (246 males and 121 females) and 419 healthy controls (172 males and 247 females). The cognitive performance was assessed by Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and the COMT Val158Met (rs4680) polymorphism is genotyped. The psychopathological symptoms of the patients were assessed by the Positive and Negative Syndrome Scale (PANSS).

RESULTS

We find that male patients had a significantly higher proportion of carrying the Val allele and Val/Val carriers exhibited more severe positive symptoms and cognitive impairment than Met carriers. COMT Val158Met (rs4680) polymorphism inconsistently mediated the relationship between sex and cognitive performance in schizophrenia patients.

CONCLUSION

These findings suggest that COMT Val158Met (rs4680) polymorphism is associated with the risk and severity of schizophrenia in a sexually dimorphic way and contributes more to the clinical symptoms and cognitive impairment in male patients with schizophrenia.

Progress and Pitfalls in Developing Agents to Treat Neurocognitive Deficits Associated with Schizophrenia

Cognitive impairments associated with schizophrenia (CIAS) represent a central element of the symptomatology of this severe mental disorder. CIAS substantially determine the disease prognosis and hardly, if at all, respond to treatment with currently available antipsychotics. Remarkably, all drugs presently approved for the treatment of schizophrenia are, to varying degrees, dopamine D₂/D₃ receptor blockers. In turn, rapidly growing evidence suggests the immense significance of systems other than the dopaminergic system in the genesis of CIAS. Accordingly, current efforts addressing the unmet needs of patients with schizophrenia are primarily based on interventions in other non-dopaminergic systems. In this review article, we provide a brief overview of the available evidence on the importance of specific systems in the development of CIAS. In addition, we describe the promising targets for the development of new drugs that have been used so far. In doing so, we present the most important candidates that have been investigated in the field of the specific systems in recent years and present a summary of the results available at the time of drafting this review (May 2022), as well as the currently ongoing studies.

Cognitive Deficit in Schizophrenia: From Etiology to Novel Treatments

Schizophrenia is a major mental illness characterized by positive and negative symptoms, and by cognitive deficit. Although cognitive impairment is disabling for patients, it has been largely neglected in the treatment of schizophrenia. There are several reasons for this lack of treatments for cognitive deficit, but the complexity of its etiology-in which neuroanatomic, biochemical and genetic factors concur-has contributed to the lack of effective treatments. In the last few years, there have been several attempts to develop novel drugs for the treatment of cognitive impairment in schizophrenia. Despite these efforts, little progress has been made. The latest findings point to the importance of developing personalized treatments for schizophrenia which enhance neuroplasticity, and of combining pharmacological treatments with non-pharmacological measures.

Association Between Cardiovascular Risk Factors and Cognitive Impairment in People With Schizophrenia: A Systematic Review and Meta-analysis

IMPORTANCE

Schizophrenia is associated with cognitive dysfunction and cardiovascular risk factors, including metabolic syndrome (MetS) and its constituent criteria. Cognitive dysfunction and cardiovascular risk factors can worsen cognition in the general population and may contribute to cognitive impairment in schizophrenia.

OBJECTIVE

To study the association between cognitive dysfunction and cardiovascular risk factors and cognitive impairment in individuals with schizophrenia.

DATA SOURCES

A search was conducted of Embase, Scopus, MEDLINE, PubMed, and Cochrane databases from inception to February 25, 2020, using terms that included synonyms of schizophrenia AND metabolic adversities AND cognitive function. Conference proceedings, clinical trial registries, and reference lists of relevant publications were also searched.

STUDY SELECTION

Studies were included that (1) examined cognitive functioning in patients with schizophrenia or schizoaffective disorder; (2) investigated the association of cardiovascular disease risk factors, including MetS, diabetes, obesity, overweight, obesity or overweight, hypertension, dyslipidemia, and insulin resistance with outcomes; and (3) compared cognitive performance of patients with schizophrenia/schizoaffective disorder between those with vs without cardiovascular disease risk factors.

DATA EXTRACTION AND SYNTHESIS

Extraction of data was conducted by 2 to 3 independent reviewers per article. Data were meta-analyzed using a random-effects model.

MAIN OUTCOMES AND MEASURES

The primary outcome was global cognition, defined as a test score using clinically validated measures of overall cognitive functioning.

RESULTS

Twenty-seven studies involving 10 174 individuals with schizophrenia were included. Significantly greater global cognitive deficits were present in patients with schizophrenia who had MetS (13 studies; n = 2800; effect size [ES] = 0.31; 95% CI, 0.13-0.50; P = .001), diabetes (8 studies; n = 2976; ES = 0.32; 95% CI, 0.23-0.42; P < .001), or hypertension (5 studies; n = 1899; ES = 0.21; 95% CI, 0.11-0.31; P < .001); nonsignificantly greater deficits were present in patients with obesity (8 studies; n = 2779; P = .20), overweight (8 studies; n = 2825; P = .41), and insulin resistance (1 study; n = 193; P = .18). Worse performance in specific cognitive domains was associated with cognitive dysfunction and cardiovascular risk factors regarding 5 domains in patients with diabetes (ES range, 0.23 [95% CI, 0.12-0.33] to 0.40 [95% CI, 0.20-0.61]) and 4 domains with MetS (ES range, 0.15 [95% CI, 0.03-0.28] to 0.40 [95% CI, 0.20-0.61]) and hypertension (ES range, 0.15 [95% CI, 0.04-0.26] to 0.27 [95% CI, 0.15-0.39]).

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, MetS, diabetes, and hypertension were significantly associated with global cognitive impairment in people with schizophrenia.

Working memory deficits in schizophrenia are associated with the rs34884856 variant and expression levels of the NR4A2 gene in a sample Mexican population: a case control study

BACKGROUND

Cognitive functions represent useful endophenotypes to identify the association between genetic variants and schizophrenia. In this sense, the NR4A2 gene has been implicated in schizophrenia and cognition in different animal models and clinical trials. We hypothesized that the NR4A2 gene is associated with working memory performance in schizophrenia. This study aimed to analyze two variants and the expression levels of the NR4A2 gene with susceptibility to schizophrenia, as well as to evaluate whether possession of NR4A2 variants influence the possible correlation between gene expression and working memory performance in schizophrenia.

METHODS

The current study included 187 schizophrenia patients and 227 controls genotyped for two of the most studied NR4A2 genetic variants in neurological and neuropsychiatric diseases. Genotyping was performed using High Resolution Melt and sequencing techniques. In addition, mRNA expression of NR4A2 was performed in peripheral mononuclear cells of 112 patients and 118 controls. A group of these participants, 54 patients and 87 controls, performed the working memory index of the WAIS III test.

RESULTS

Both genotypic frequencies of the two variants and expression levels of the NR4A2 gene showed no significant difference when in patients versus controls. However, patients homozygous for the rs34884856 promoter variant showed a positive correlation between expression levels and auditory working memory.

CONCLUSIONS

Our finding suggested that changes in expression levels of the NR4A2 gene could be associated with working memory in schizophrenia depending on patients' genotype in a sample from a Mexican population.

[A new look at the genetics of neurocognitive deficits in schizophrenia]

The article presents current literature data on genetic studies of neurocognitive deficit in schizophrenia, including the genes of neurotransmitter systems (dopaminergic, glutamatergic, and serotonergic); genes analyzed in genome-wide association studies (GWAS), as well as other genetic factors related to the pathophysiological mechanisms underlying schizophrenia and neurocognitive disorders.

The role of norepinephrine in the pathophysiology of schizophrenia

Several lines of evidence have suggested for decades a role for norepinephrine (NE) in the pathophysiology and treatment of schizophrenia. Recent experimental findings reveal anatomical and physiological properties of the locus coeruleus-norepinephrine (LC-NE) system and its involvement in brain function and cognition. Here, we integrate these two lines of evidence. First, we review the functional and structural properties of the LC-NE system and its impact on functional brain networks, cognition, and stress, with special emphasis on recent experimental and theoretical advances. Subsequently, we present an update about the role of LC-associated functions for the pathophysiology of schizophrenia, focusing on the cognitive and motivational deficits. We propose that schizophrenia phenomenology, in particular cognitive symptoms, may be explained by an abnormal interaction between genetic susceptibility and stress-initiated LC-NE dysfunction. This in turn, leads to imbalance between LC activity modes, dysfunctional regulation of brain network integration and neural gain, and deficits in cognitive functions. Finally, we suggest how recent development of experimental approaches can be used to characterize LC function in schizophrenia.

Current challenges and possible future developments in personalized psychiatry with an emphasis on psychotic disorders

A personalized medicine approach seems to be particularly applicable to psychiatry. Indeed, considering mental illness as deregulation, unique to each patient, of molecular pathways, governing the development and functioning of the brain, seems to be the most justified way to understand and treat disorders of this medical category. In order to extract correct information about the implicated molecular pathways, data can be drawn from sampling phenotypic and genetic biomarkers and then analyzed by a machine learning algorithm. This review describes current difficulties in the field of personalized psychiatry and gives several examples of possibly actionable biomarkers of psychotic and other psychiatric disorders, including several examples of genetic studies relevant to personalized psychiatry. Most of these biomarkers are not yet ready to be introduced in clinical practice. In a next step, a perspective on the path personalized psychiatry may take in the future is given, paying particular attention to machine learning algorithms that can be used with the goal of handling multidimensional datasets.

Multiple rare inherited variants in a four generation schizophrenia family offer leads for complex mode of disease inheritance

Schizophrenia is a clinically and genetically heterogeneous neuropsychiatric disorder, with a polygenic basis but identification of the specific determinants is a continuing challenge. In this study, we analyzed a multigenerational family, with all healthy individuals in the first two generations, and four progeny affected with schizophrenia in the subsequent two generations, using whole exome sequencing. We identified five rare protein sequence altering heterozygous variants, in five different genes namely SMARCA5, PDE1B, TNIK, SMARCA2 and FLRT shared among all affected members and predicted to be damaging. Variants in SMARCA5 and PDE1B were inherited from the unaffected father whereas variants in TNIK, SMARCA2 and FLRT1 were inherited from the unaffected mother in all the three affected individuals in the third generation; and notably all these five variants were transmitted by an affected mother to her affected son. Microsatellite based analysis lent a modest linkage support (LOD score of 1.2; θ=0.0 at each variant). Of note, analysis of exome data of an ancestry matched unrelated schizophrenia cohort (n = 350), revealed a total of 16 rare variants (MAF < 0.01) in these five genes. Interestingly, these five genes involved in neurodevelopmental and/or neurotransmitter signaling processes are implicated in the etiology of schizophrenia previously. This study provides good evidence for a likely cumulative contribution of multiple rare variants from disease relevant genes with a threshold effect in disease development and seems to explain the unusual disease transmission pattern generally witnessed in such conditions, but warrants extensive replication efforts in families with similar complex disease inheritance profiles.

Polygenic Risk Scores Shed Light on the Relationship between Schizophrenia and Cognitive Functioning: Review and Meta-Analysis

Schizophrenia is a multifactorial disease associated with widespread cognitive impairment. Although cognitive deficits are one of the factors most strongly associated with functional impairment in schizophrenia (SZ), current treatment strategies hardly tackle these impairments. To develop more efficient treatment strategies in patients, a better understanding of their pathogenesis is needed. Recent progress in genetics, driven by large genome-wide association studies (GWAS) and the use of polygenic risk scores (PRS), has provided new insights about the genetic architecture of complex human traits, including cognition and SZ. Here, we review the recent findings examining the genetic links between SZ and cognitive functions in population-based samples as well as in participants with SZ. The performed meta-analysis showed a negative correlation between the polygenetic risk score of schizophrenia and global cognition (p < 0.001) when the samples rely on general and healthy participants, while no significant correlation was detected when the three studies devoted to schizophrenia patients were meta-analysed (p > 0.05). Our review and meta-analysis therefore argues against universal pleiotropy for schizophrenia alleles and cognition, since cognition in SZ patients would be underpinned by the same genetic factors than in the general population, and substantially independent of common variant liability to the disorder.

β-lactolin, a whey-derived glycine-threonine-tryptophan-tyrosine lactotetrapeptide, improves prefrontal cortex-associated reversal learning in mice

Dementia and cognitive decline have become worldwide public health problems. We have previously reported that a whey-derived glycine-threonine-tryptophan-tyrosine peptide, β-lactolin, improves hippocampus-dependent memory functions in mice. The supplementation with a whey digest rich in β-lactolin improves memory retrieval and executive function in a clinical trial, but the effect of β-lactolin on prefrontal cortex (PFC)-associated cognitive function was unclear. Here we examined the effect of β-lactolin and the whey digest on PFC-associated visual discrimination (VD) and reversal discrimination (RD) learning, using a rodent touch panel-based operant system. β-Lactolin and the whey digest significantly improved the RD learning, and the whey digest enhanced the response latency during the VD task, indicating that β-lactolin and the whey digest improve PFC-associated cognitive functions. Given the translational advantages of the touch panel operant system, consumption of β-lactolin in daily life could be beneficial for improving human PFC-associated cognitive function, helping to prevent dementia.

The role of genetics in cognitive remediation in schizophrenia: A systematic review

The role of genetics in cognitive remediation therapies in schizophrenia has not been completely understood yet. Different genes involved in neurotrophic, dopaminergic and serotonin systems have reported to influence cognitive functioning in schizophrenia. These genetic factors could also be contributing to the variability in responsiveness to cognitive treatments. No comprehensive synthesis of the literature of the role of genetics in the context of cognitive remediation has been conducted until now. We aimed to systematically review the published works through three electronic database searches: PubMed, Scopus, and the Cochrane Library. Eligible studies revealed a rising interest in the field although the number of published studies was rather small (n = 10). Eventually, promising results showing a relationship between some phenotypic variations based on different polymorphisms and different levels of responsivity to cognitive remediation therapies have been described although results are still inconclusive. In case those findings will be replicated, they could be guiding future research and informing clinical decision-making in the next future.

A Novel Biomarker Renalase and Its Relationship with its Substrates in Schizophrenia

Background

Schizophrenia, particularly the form related to excessive dopamine (DA), is a chronic psychotic disorder affecting millions of people worldwide. Renalase metabolizes its catecholamine (CA) substrates, including DA, suggesting that there might be an association between renalase levels and schizophrenia occurrence. Therefore, the current study aimed to evaluate the renalase and CA levels in the serum of patients with schizophrenia.

Methods

The study was conducted with thirty-three schizophrenia patients and an age- and gender-matched group of thirty-one controls. Renalase and CA levels were measured by using an enzyme-linked immunosorbent assay (ELISA).

Results

Renalase levels were significantly lower in the schizophrenia patients than in the control group (p<0.05), whereas DA levels were significantly higher (p<0.05). The epinephrine (Epi) levels of both groups were similar (p=0.186), while the norepinephrine levels in patients with schizophrenia were significantly lower than those in the control group (p<0.05). The areas under the curves for the renalase-dopamine, renalase-norepinephrine and renalase-epinephrine ratios were 0.805, 95% confidence interval (CI): 0.699–0.912 (p<0.001); 0.726, 95% CI: 0.594–0.859 (p=0.032); and 0.656, 95% CI: 0.520–0.791 (p=0.02).

Conclusions

The high DA levels in patients with schizophrenia might be due to low renalase levels. Renalase enzyme levels may play a substantial role in the pathophysiology of schizophrenia. Thus, this enzyme might be a new future target for the treatment and diagnosis of schizophrenia after intrabrain renalase and DA dynamics have been further evaluated.

The effect of ANKK1 Taq1A and DRD2 C957T polymorphisms on executive function: A systematic review and meta-analysis

Research in healthy adults suggests that C957T polymorphism of the dopamine D2 receptor encoding DRD2 and the Taq1A polymorphism of the neighbouring gene ankyrin repeat and kinase domain containing 1 (ANKK1) alter dopaminergic signalling and may influence prefrontally-mediated executive functions. A systematic review and meta-analysis was carried out on the evidence for the association of DRD2 C957T and ANKK1 Taq1A polymorphisms in performance on tasks relating to the three core domains of executive function: working memory, response inhibition and cognitive flexibility in healthy adults. CINAHL, MEDLINE, PsycARTICLES and PsychINFO databases were searched for predefined key search terms associated with the two polymorphisms and executive function. Studies were included if they investigated a healthy adult population with the mean age of 18-65 years, no psychiatric or neurological disorder and only the healthy adult arm were included in studies with any case-control design. Data from 17 independent studies were included in meta-analysis, separated by the Taq1A and C957T polymorphisms and by executive function tests: working memory (Taq1A, 6 samples, n = 1270; C957 T, 6 samples, n = 977), cognitive flexibility (C957 T, 3 samples, n = 620), and response inhibition (C957 T, 3 samples, n = 598). The meta-analyses did not establish significant associations between these gene polymorphisms of interest and any of the executive function domains. Theoretical implications and methodological considerations of these findings are discussed.

Both Val158Met Polymorphism of Catechol-O-Methyltransferase Gene and Menstrual Cycle Affect Prepulse Inhibition but Not Attentional Modulation of Prepulse Inhibition in Younger-Adult Females

Prepulse inhibition (PPI) can be modulated by both the Val158Met (rs4680) polymorphism of the Catechol-O-Methyltransferase (COMT) gene and the menstrual-cycle-related hormone fluctuations, each of which affects the subcortical/cortical dopamine metabolism. PPI can also be modulated by attention. The attentional modulation of PPI (AMPPI) is sensitive to psychoses. Whether the Val158Met polymorphism affects the AMPPI in female adults at different menstrual-cycle phases is unknown. This study examined whether AMPPI and/or PPI are affected by the Val158Met polymorphism in 177 younger-adult females whose menstrual cycles were mutually different across the menstruation, proliferative, or secretory phases. The AMPPI was evaluated by comparing PPI under the condition of the auditory precedence-effect-induced perceptual spatial separation between the prepulse stimulus and a masking noise (PPI_PSS) against that under the condition of the precedence-effect-induced perceptual spatial co-location (PPI_PSC). The results showed that both the menstrual cycle and the COMT Val158Met polymorphism affected both PPI_PSC and PPI_PSS, but not the AMPPI (difference between PPI_PSS and PPI_PSC). Moreover, throughout the menstrual cycle, both PPI_PSC and PPI_PSS decreased monotonously in Val/Val-carrier participants. However, the decreasing pattern was not overserved in either Met/Met-carrier or Met/Val-carrier participants. Thus, in healthy younger-adult females, PPI_PSC and PPI_PSS, but not the AMPPI, is vulnerable to changes of ovarian hormones, and the COMT Val158Met polymorphism also has a modulating effect on this menstrual-cycle-dependent PPI variation. In contrast, the AMPPI seems to be more steadily trait-based, less vulnerable to ovarian hormone fluctuations, and may be useful in assisting the diagnosis of schizophrenia in female adults.

DISC1 gene polymorphisms and the risk of schizophrenia in an Iranian population: A preliminary study

BACKGROUND

Schizophrenia, schizoaffective disorder, and bipolar illness are common psychological disorders with high heritability and variable phenotypes. The disrupted in schizophrenia 1 ( DISC1) gene, on chromosome 1q42, has an essential role in neurite outgrowth and cell signaling. The purpose of this study was to investigate the association of three single-nucleotide polymorphisms (SNPs; rs6675281, rs2255340, and rs2738864) with schizophrenia disorder. These three SNPs were chosen as they had been used in most of the previous studies.

METHODS

In a case-control study of Iranian population for the first time 778 blood samples were collected including, 402 schizophrenic patients and 376 healthy controls. Genomic DNA was extracted from peripheral blood using DNA extraction kit (BioFlux Co). The genotypes of rs6675281, rs2255340, and rs2738864 were detected by nested allele-specific multiplex polymersae chain reaction (PCR).

RESULTS

Our data revealed that the three SNPs are significantly associated with schizophrenia (rs2255349 C>T: confidence interval (CI), 2.115 to 3.268; P = 0.0000 OR: 2.629; rs2738864 C>T: CI, 1.538 to 2.339; P = 0.0000 OR: 1.897; rs6675281 C>T: CI, 2.788 to 4.662; P = 0.0009241 OR: 3.605). Through applying the expectation-maximization (EM) algorithm, we calculated the haplotype frequency, and finally performed haplotype analysis with Bonferroni correction and data preprocessing methods and the results showed rs66875281 to have the highest association.

DISCUSSION

Our findings primarily showed that DISC1 gene polymorphisms contribute to schizophrenia risk and have a significant association with this disorder among Iranian population. The strategy was found to be easy, rapid, specific, and consistent for the co-occurring detection of the DISC1 polymorphisms. We could finally confirm that the polymorphisms are related to schizophrenia studied in Iranian population.

Community participation factors and poor neurocognitive functioning among persons with schizophrenia

Poor neurocognitive functioning among individuals with schizophrenia is typically conceptualized as resulting from a disease process. The objective of this article is to further expand understanding of poor neurocognition beyond pathogenesis toward a perspective that also incorporates community participation factors. This article focuses on three such factors-sedentary behavior, loneliness, and poverty-that have been demonstrated to be related to neurocognition and are highly prevalent among individuals with schizophrenia. This article provides an overview of the research on each factor and discusses its possible connection to neurocognitive challenges for individuals with schizophrenia. Implications for research, policy, and practice efforts are then proposed to broaden approaches to understanding and addressing neurocognitive challenges in this population. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Effectiveness of integrated psychological therapy on clinical, neuropsychological, emotional and functional outcome in schizophrenia: a RCT study

Background: Cognitive impairment is considered a central feature of schizophrenia (SZ) and several rehabilitation treatments have been developed to try to improve cognitive deficits.Aims: The aim of the present study was to analyze the effectiveness of integrated psychological therapy (IPT) compared with a standard treatment (TAU) in two groups of patients with SZ, using a comprehensive testing battery of clinical, cognitive, social cognition and functional outcome domains.Methods: Forty-one patients with SZ were assigned to IPT or TAU groups in a randomized controlled trial (RCT). Psychopathological, neuropsychological, emotional and functional outcome variables were assessed at baseline and after 36 weeks of treatment.Results: The IPT group showed significant improvements than the TAU group regarding clinical and functional outcome variables. Moreover, the IPT group improved significantly in the cognitive domains and emotional functioning. Finally, linear regression has highlighted that the improvement of cognitive variables depends on having done the IPT treatment.Conclusions: IPT seems to be effective in improving clinical, neuropsychological, emotional and functional outcome in chronic SZ inpatients. Further studies would be desirable to deepen the effectiveness of IPT in the field of the psychiatric rehabilitation pointing to the possibility of recovery from mental illness.

How can genetics help understand the relationship between cognitive dysfunction and schizophrenia?

Despite the consistent finding that cognitive dysfunction is a core characteristic of schizophrenia (SCZ), little is known about the underlying pathophysiology. Recent progress in human genetics, driven by large genome-wide association studies (GWAS), has provided new data about the genetic architecture of complex human traits, including cognition and SCZ. Novel analytical tools have provided unprecedented opportunities to leverage the large amount of information from GWAS. Here we review the latest findings related to genetic architecture and risk genes of SCZ and cognitive functions, and recent findings of overlapping genetic factors. The recent GWAS of SCZ implicate over 100 risk gene loci, each with a small effect. A similar genetic architecture seems to be present in cognitive domains, suggesting that these phenotypes are highly polygenic. Further, GWAS have revealed more than 20 gene loci associated with cognitive traits, including intelligence, general cognition (g-factor), reaction time and verbal-numerical reasoning. Several gene loci have been implicated in educational attainment, a proxy measure of cognitive function. Recently, overlapping gene loci were found between education and SCZ, and between SCZ and cognitive traits, suggesting common genetic risk between SCZ and cognitive dysfunction. Mathematical modeling of GWAS of cognition and SCZ indicate that only a fraction of the heritability is identified. The evidence suggests a polygenic architecture for SCZ and cognitive functions, and a large degree of shared genetic risk. This indicates novel molecular genetic mechanisms and strengthens the notion that SCZ is more likely a part of the normal distribution and not a separate entity.

Omega-3 fatty acid supplementation may prevent loss of gray matter thickness in the left parieto-occipital cortex in first episode schizophrenia: A secondary outcome analysis of the OFFER randomized controlled study

The aim of the study was to assess changes in cortical thickness related to the use of n-3 polyunsaturated fatty acids (PUFA) as add-on therapy in patients with first episode schizophrenia. A double-blind randomized controlled study was conducted using a 26-week intervention composed of concentrated fish oil containing 2.2g/d of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) or placebo (olive oil). Participants underwent MRI scanning twice to assess changes in cortical thickness: at the beginning and at the end of intervention. Data of suitable quality was obtained from 29 participants. The T1-weighted images for each participant were analyzed using FreeSurfer methodology for longitudinal pipeline. Significant differences in cortical thickness loss were observed between the groups in the parieto-occipital regions of Brodmann areas 7 and 19 of the left hemisphere, dysfunctions in which may be involved in schizophrenia symptomatology. The results of the study support the previous observations carried out in older individuals and patients with mild cognitive impairment, indicating that n-3 PUFA may have neuroprotective properties, especially at early stages of neurodegenerative diseases, such as schizophrenia. If replicated, the results of the present study may encourage clinicians to consider n-3 PUFA as a promising addition to antipsychotics for long-term treatment of schizophrenia.

Cognitive development prior to onset of psychosis

Schizophrenia patients commonly exhibit substantial and diffuse cognitive impairment. Evidence suggests that subtle cognitive deficits are already apparent in childhood and adolescence, many years prior to onset of psychosis. While there is almost unequivocal evidence of some degree of cognitive impairment in individuals who later develop schizophrenia, the literature remains inconclusive regarding the exact nature of this impairment and warrants careful review and interpretation. Meta-analytic findings suggest that individuals who later develop schizophrenia, but not related disorders, such as bipolar disorder, exhibit a premorbid IQ deficit of around 8 points. Several studies have also found evidence for premorbid deficits across most cognitive domains, such as language, processing speed and executive functions. Longitudinal studies, although rare, suggest that individuals who go on to develop schizophrenia may show a course of increasing cognitive impairment prior to onset of psychosis. While evidence regarding the etiology of premorbid deficits is scarce, common and rare genetic variants, as well as environmental factors such as obstetric complications and cannabis use may play an important role and warrant further examination. In this selected review, we give an overview of population-based studies on premorbid cognitive deficits in schizophrenia, with a special focus on evidence regarding the specificity, profile and course of these deficits.

A neurogenetic model for the study of schizophrenia spectrum disorders: the International 22q11.2 Deletion Syndrome Brain Behavior Consortium

Rare copy number variants contribute significantly to the risk for schizophrenia, with the 22q11.2 locus consistently implicated. Individuals with the 22q11.2 deletion syndrome (22q11DS) have an estimated 25-fold increased risk for schizophrenia spectrum disorders, compared to individuals in the general population. The International 22q11DS Brain Behavior Consortium is examining this highly informative neurogenetic syndrome phenotypically and genomically. Here we detail the procedures of the effort to characterize the neuropsychiatric and neurobehavioral phenotypes associated with 22q11DS, focusing on schizophrenia and subthreshold expression of psychosis. The genomic approach includes a combination of whole-genome sequencing and genome-wide microarray technologies, allowing the investigation of all possible DNA variation and gene pathways influencing the schizophrenia-relevant phenotypic expression. A phenotypically rich data set provides a psychiatrically well-characterized sample of unprecedented size (n=1616) that informs the neurobehavioral developmental course of 22q11DS. This combined set of phenotypic and genomic data will enable hypothesis testing to elucidate the mechanisms underlying the pathogenesis of schizophrenia spectrum disorders.

Identification of Genetic Loci Jointly Influencing Schizophrenia Risk and the Cognitive Traits of Verbal-Numerical Reasoning, Reaction Time, and General Cognitive Function

IMPORTANCE

Schizophrenia is associated with widespread cognitive impairments. Although cognitive deficits are one of the factors most strongly associated with functional outcome in schizophrenia, current treatment strategies largely fail to ameliorate these impairments. To develop more efficient treatment strategies in patients with schizophrenia, a better understanding of the pathogenesis of these cognitive deficits is needed. Accumulating evidence indicates that genetic risk of schizophrenia may contribute to cognitive dysfunction.

OBJECTIVE

To identify genomic regions jointly influencing schizophrenia and the cognitive domains of reaction time and verbal-numerical reasoning, as well as general cognitive function, a phenotype that captures the shared variation in performance across cognitive domains.

DESIGN, SETTING, AND PARTICIPANTS

Combining data from genome-wide association studies from multiple phenotypes using conditional false discovery rate analysis provides increased power to discover genetic variants and could elucidate shared molecular genetic mechanisms. Data from the following genome-wide association studies, published from July 24, 2014, to January 17, 2017, were combined: schizophrenia in the Psychiatric Genomics Consortium cohort (n = 79 757 [cases, 34 486; controls, 45 271]); verbal-numerical reasoning (n = 36 035) and reaction time (n = 111 483) in the UK Biobank cohort; and general cognitive function in CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) (n = 53 949) and COGENT (Cognitive Genomics Consortium) (n = 27 888).

MAIN OUTCOMES AND MEASURES

Genetic loci identified by conditional false discovery rate analysis. Brain messenger RNA expression and brain expression quantitative trait locus functionality were determined.

RESULTS

Among the participants in the genome-wide association studies, 21 loci jointly influencing schizophrenia and cognitive traits were identified: 2 loci shared between schizophrenia and verbal-numerical reasoning, 6 loci shared between schizophrenia and reaction time, and 14 loci shared between schizophrenia and general cognitive function. One locus was shared between schizophrenia and 2 cognitive traits and represented the strongest shared signal detected (nearest gene TCF20; chromosome 22q13.2), and was shared between schizophrenia (z score, 5.01; P = 5.53 × 10-7), general cognitive function (z score, -4.43; P = 9.42 × 10-6), and verbal-numerical reasoning (z score, -5.43; P = 5.64 × 10-8). For 18 loci, schizophrenia risk alleles were associated with poorer cognitive performance. The implicated genes are expressed in the developmental and adult human brain. Replicable expression quantitative trait locus functionality was identified for 4 loci in the adult human brain.

CONCLUSIONS AND RELEVANCE

The discovered loci improve the understanding of the common genetic basis underlying schizophrenia and cognitive function, suggesting novel molecular genetic mechanisms.

Chromatin Remodeling BAF (SWI/SNF) Complexes in Neural Development and Disorders

The ATP-dependent BRG1/BRM associated factor (BAF) chromatin remodeling complexes are crucial in regulating gene expression by controlling chromatin dynamics. Over the last decade, it has become increasingly clear that during neural development in mammals, distinct ontogenetic stage-specific BAF complexes derived from combinatorial assembly of their subunits are formed in neural progenitors and post-mitotic neural cells. Proper functioning of the BAF complexes plays critical roles in neural development, including the establishment and maintenance of neural fates and functionality. Indeed, recent human exome sequencing and genome-wide association studies have revealed that mutations in BAF complex subunits are linked to neurodevelopmental disorders such as Coffin-Siris syndrome, Nicolaides-Baraitser syndrome, Kleefstra's syndrome spectrum, Hirschsprung's disease, autism spectrum disorder, and schizophrenia. In this review, we focus on the latest insights into the functions of BAF complexes during neural development and the plausible mechanistic basis of how mutations in known BAF subunits are associated with certain neurodevelopmental disorders.

Translating advances in the molecular basis of schizophrenia into novel cognitive treatment strategies

The presence and severity of cognitive symptoms, including working memory, executive dysfunction and attentional impairment, contributes materially to functional impairment in schizophrenia. Cognitive symptoms have proved to be resistant to both first- and second-generation antipsychotic drugs. Efforts to develop a consensus set of cognitive domains that are both disrupted in schizophrenia and are amenable to cross-species validation (e.g. the National Institute of Mental Health Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia and Research Domain Criteria initiatives) are an important step towards standardization of outcome measures that can be used in preclinical testing of new drugs. While causative genetic mutations have not been identified, new technologies have identified novel genes as well as hitherto candidate genes previously implicated in the pathophysiology of schizophrenia and/or mechanisms of antipsychotic efficacy. This review comprises a selective summary of these developments, particularly phenotypic data arising from preclinical genetic models for cognitive dysfunction in schizophrenia, with the aim of indicating potential new directions for pro-cognitive therapeutics. Linked Articles This article is part of a themed section on Pharmacology of Cognition: a Panacea for Neuropsychiatric Disease? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.19/issuetoc.

Negative symptoms in schizophrenia

The negative symptoms have been described in association with schizophrenia since the early days of it being recognized as an entity. However, their elusive nature kept them unacknowledged until there was a revival of interest in them following the development of specific quantifying measures. Over the past three decades, there has been a tremendous surge in research on their types, measurements, status in the present classificatory system, and their implications. The developments in modern investigatory methods have provided the researchers with fresh insights into the underlying mechanisms, and a distributed functioning of the neuronal networks has emerged as the major abnormality. Accordingly, a variety of pharmacological and other treatment modalities have been developed which go beyond the traditional. Nevertheless, a lot remain unanswered. The present paper summarizes important concepts with regard to negative symptoms in schizophrenia.