Factor analysis of neurocognitive tests in a large sample of schizophrenic probands, their siblings, and healthy controls

Comparison of factor analysis models applied to the NCANDA neuropsychological test battery

The factor structure of neuropsychological functioning among a large sample (N = 831) of American youth (ages 12-21 at baseline) was investigated in order to identify an optimal model. Candidate models were selected based on their potential to provide service to the study of adolescent development and the effects of heavy episodic alcohol consumption. Data on neuropsychological functioning were obtained from the NCANDA study. This is a longitudinal community study of the effects of alcohol exposure on neurodevelopment. Three conceptually motivated and one empirically motivated factor analysis model of neuropsychological domains were compared based on penalized-likelihood selection criteria and model fit statistics. Two conceptually-motivated models were found to have adequate fit and pattern invariance to function as a measurement model for the Penn Computerized Neurocognitive Battery (Penn CNB) anchored neuropsychological battery in NCANDA. Corroboration of previous factor analysis models was obtained, in addition to the identification of an alternative factor model that has higher discriminant capacity for neuropsychological domains hypothesized to be most sensitive to alcohol exposure in human adolescents. The findings support the use of a factor model developed originally for the Penn CNB and a model developed specifically for the NCANDA project. The NCANDA 8-Factor Model has conceptual and empirical advantages that were identified in the current and prior studies. These advantages are particularly valuable when applied in alcohol research settings.

European Psychiatric Association guidance on assessment of cognitive impairment in schizophrenia

Background

Impairment in a wide range of cognitive abilities has been consistently reported in individuals with schizophrenia. Both neurocognitive and social cognitive deficits are thought to underlie severe functional disabilities associated with schizophrenia. Despite the key role in schizophrenia outcome, cognition is still poorly assessed in both research and clinical settings.

Methods

In this guidance paper, we provide a systematic review of the scientific literature and elaborate several recommendations for the assessment of cognitive functions in schizophrenia both in research settings and in real-world clinical practice.

Results

Expert consensus and systematic reviews provided guidance for the optimal assessment of cognitive functions in schizophrenia. Based on the reviewed evidence, we recommend a comprehensive and systematic assessment of neurocognitive and social cognitive domains in schizophrenia, in all phases of the disorder, as well as in subjects at risk to develop psychosis. This European Psychiatric Association guidance recommends not only the use of observer reports but also self-reports and interview-based cognitive assessment tools. The guidance also provides a systematic review of the state of the art of assessment in the first episode of psychosis patients and in individuals at risk for psychosis.

Conclusion

The comprehensive review of the evidence and the recommendations might contribute to advance the field, allowing a better cognitive assessment, and avoiding overlaps with other psychopathological dimensions. The dissemination of this guidance paper may promote the development of shared guidelines concerning the assessment of cognitive functions in schizophrenia, with the purpose to improve the quality of care and to obtain recovery.

Hippocampal Volume, Cognitive Functions, Depression, Anxiety, and Quality of Life in Patients With Cushing Syndrome

CONTEXT

Cushing syndrome (CS) is associated with hippocampal atrophy and psychopathology.

OBJECTIVE

The primary objective of this systematic review was to assess hippocampal volume (HV) in patients with CS. The secondary objectives were to assess patients' cognitive functioning, depressive and anxiety symptoms, and quality of life.

DATA SOURCES

PubMed, Embase, Cochrane, LILACs, and Scopus databases were searched for relevant studies until 1 May 2019.

STUDY SELECTION

Case-control studies comparing patients with CS with healthy control subjects, or studies assessing patients with CS before and after surgery were included. The initial search resulted in 18 studies fulfilling the inclusion criteria.

DATA EXTRACTION

Data extraction regarding all outcomes was performed independently by two reviewers. Quality assessment was assessed with the Newcastle-Ottawa Scale for case-control studies.

DATA SYNTHESIS

Meta-analysis was performed using a random effect model. The right-side HV in patients with CS was reduced by a standard mean difference of 0.68 (95% CI, -1.12 to -0.24; P = 0.002; I2 = 0%) compared with healthy control subjects, but with no increase in HV after surgery. Patients had more depressive symptoms, impaired cognitive functions, and reduced health-related QoL (HRQoL), which all responded favorably to surgery. The data did not support the presence of anxiety in patients with CS.

CONCLUSION

An overall reduction of HV in patients with CS was not suggested by the study findings. However, most cognitive domains were significantly affected and responded favorably to surgery. Depressive symptoms and reduced HRQoL were present in patients with CS and improved after surgery.

Schizotypy-Independent and Schizotypy-Modulated Cognitive Impairments in Unaffected First-Degree Relatives of Schizophrenia-spectrum Patients

Objective

The aim of the study was to compare the neurocognitive profile of unaffected first-degree relatives of schizophrenia patients with control individuals, controlling for different schizotypal traits.

Method

One hundred and fifteen adult unaffected first-degree relatives of schizophrenia-spectrum patients and 122 controls were tested for schizotypy with the Schizotypal Personality Questionnaire. They also underwent a thorough neurocognitive assessment with a range of tasks covering several aspects of executive functioning. Between-group differences in cognition were examined first with multivariate analysis of variance and then with a series of multivariate analyses of covariance, including the schizotypal dimensions as covariates.

Results

The relatives had higher scores on all schizotypal dimensions compared with controls and poorer planning, problem solving, strategy formation and working memory, irrespective of schizotypal traits. They also scored lower in executive working memory and verbal fluency. The difference in executive working memory was sensitive to the effects of paranoid and negative schizotypy (both dimensions abolished the between-group difference) whereas the difference in verbal fluency was sensitive only to the effects of paranoid schizotypy. Neither cognitive-perceptual nor disorganized schizotypy accounted for any differences in neurocognition between relatives and the controls.

Conclusions

Impairments in planning, problem solving, strategy formation and working memory are "core" impairments in the schizophrenia-spectrum, possibly due to high heritability effects in these functions. Impairments in executive working memory and verbal fluency are associated with paranoid and negative schizotypy, possibly due to alterations in a common fronto-temporo-parietal neural network.

A Polygenic Risk Score of glutamatergic SNPs associated with schizophrenia predicts attentional behavior and related brain activity in healthy humans

Multiple genetic variations impact on risk for schizophrenia. Recent analyses by the Psychiatric Genomics Consortium (PGC2) identified 128 SNPs genome-wide associated with the disorder. Furthermore, attention and working memory deficits are core features of schizophrenia, are heritable and have been associated with variation in glutamatergic neurotransmission. Based on this evidence, in a sample of healthy volunteers, we used SNPs associated with schizophrenia in PGC2 to construct a Polygenic-Risk-Score (PRS) reflecting the cumulative risk for schizophrenia, along with a Polygenic-Risk-Score including only SNPs related to genes implicated in glutamatergic signaling (Glu-PRS). We performed Factor Analysis for dimension reduction of indices of cognitive performance. Furthermore, both PRS and Glu-PRS were used as predictors of cognitive functioning in the domains of Attention, Speed of Processing and Working Memory. The association of the Glu-PRS on brain activity during the Variable Attention Control (VAC) task was also explored. Finally, in a second independent sample of healthy volunteers we sought to confirm the association between the Glu-PRS and both performance in the domain of Attention and brain activity during the VAC.We found that performance in Speed of Processing and Working Memory was not associated with any of the Polygenic-Risk-Scores. The Glu-PRS, but not the PRS was associated with Attention and brain activity during the VAC. The specific effects of Glu-PRS on Attention and brain activity during the VAC were also confirmed in the replication sample.Our results suggest a pathway specificity in the relationship between genetic risk for schizophrenia, the associated cognitive dysfunction and related brain processing.

Validation of the cognitively normal range and below normal range subtypes in chronically hospitalized patients with schizophrenia

Background

Many studies have found a substantial minority of patients whose performance puts them within the normal range of neuropsychological functioning. Recently, a study has seen the delineation of two neurocognitive subtypes of schizophrenia –‘cognitively normal range’ (CNR) and ‘below normal range’ (BNR) – based on neurocognitive performance across multiple domains.

Methods

The participants were from two studies that collected neurocognitive, psychopathology and social function data between 2008 and 2015. In total the complete data from one hundred and thirty one patients of Han Chinese ethnicity with schizophrenia were collected on 21 neurocognitive indexes (assessing the domains of processing speed, attention, working memory, verbal memory, visual memory, reasoning and problem solving and IQ). Fifty-five patients of the one hundred and thirty one participants received additional ratings on their psychopathology and social functions. An exploratory graphic analysis was conducted on the neurocognitive measures for the entire sample. Difference analyses were also performed according to the aims of the study using the Independent t test, Chi-square test, and Cohen's d effect size.

Results

Analyses revealed the existence of two patients subtypes. The post hoc tests showed that there were significant differences on all of their neurocognitive measures and on most of the psychopathology and social functions between the two subtypes. These two subtypes could be referred to as the CNR subtype and the BNR subtype respectively.

Conclusions

There are neurocognitive subtypes of schizophrenia with differential illness characteristics comparable with the CNR and the BNR in patients of Han Chinese ethnicity with schizophrenia.

The Cattell–Horn–Carroll Model of Cognition for Clinical Assessment

The Cattell–Horn–Carroll (CHC) model is a comprehensive model of the major dimensions of individual differences that underlie performance on cognitive tests. Studies evaluating the generality of the CHC model across test batteries, age, gender, and culture were reviewed and found to be overwhelmingly supportive. However, less research is available to evaluate the CHC model for clinical assessment. The CHC model was shown to provide good to excellent fit in nine high-quality data sets involving popular neuropsychological tests, across a range of clinically relevant populations. Executive function tests were found to be well represented by the CHC constructs, and a discrete executive function factor was found not to be necessary. The CHC model could not be simplified without significant loss of fit. The CHC model was supported as a paradigm for cognitive assessment, across both healthy and clinical populations and across both nonclinical and neuropsychological tests. The results have important implications for theoretical modeling of cognitive abilities, providing further evidence for the value of the CHC model as a basis for a common taxonomy across test batteries and across areas of assessment.

Cognitive structure from childhood to adulthood in kindreds densely affected by schizophrenia and bipolar disorder

The developmental aspects of cognitive structures from childhood until adulthood and across different levels of risk for psychopathology have been little studied. The aim of the current study was to explore the cognitive factorial structure in subsamples from highly familial and densely affected kindreds of schizophrenia and bipolar disorder - i.e. affected adult members, non-affected adult members and high-risk youth. The same neuropsychological battery was administered in a sample of 480 participants: schizophrenia and bipolar patients (n=51), young high-risk offspring (n=61), non-affected adult relatives of patients (n=96), and controls (n=272). Exploratory Factorial Analysis was performed in the control sample and yielded a 5-factor solution: verbal comprehension, processing speed/working memory, visual learning and memory, verbal learning and memory, reasoning and problem solving. Confirmatory factor analysis indicated that the hierarchical 5-factor solution was well suited for the young high-risk offspring, the non-affected adult relatives of patient and the patients. A hierarchical model with a "g" factor was a good fit for all subsamples. These results suggest that cognitive impairments may aggregate in highly familial individuals.

Factorial validity, measurement equivalence and cognitive performance of the Cambridge Neuropsychological Test Automated Battery (CANTAB) between patients with first-episode psychosis and healthy volunteers

BACKGROUND

The purpose of this study was to use selected Cambridge Neuropsychological Test Automated Battery (CANTAB) tests to examine the dimensional structure of cognitive dysfunction in first episode of psychosis (FEP) patients compared with cognition in healthy subjects.

METHOD

A total of 109 FEP patients and 96 healthy volunteers were administered eight CANTAB tests of cognitive function. Principal components analysis (PCA) was used to estimate dimensionality within the test results. The dimensions identified by the PCA were assumed to reflect underlying cognitive traits. The plausibility of latent factor models was estimated using confirmatory factor analysis (CFA). Multi-group CFA (MGCFA) was used to test for measurement invariance of factors between groups. The nature and severity of cognitive deficits amongst patients as opposed to controls were evaluated using a general linear model.

RESULTS

Amongst subjects PCA identified two underlying cognitive traits: (i) a broad cognitive domain; (ii) attention/memory and executive function domains. Corresponding CFA models were built that fitted data well for both FEP patients and healthy volunteers. As in MGCFA latent variables appeared differently defined in patient and control groups, differences had to be ascribed using subtest scores rather than their aggregates. At subtest score level the patients performed significantly worse than healthy subjects in all comparisons (p < 0.001).

CONCLUSIONS

Results of this study demonstrate that the structure of underlying cognitive abilities as measured by a selection of CANTAB tests is not the same for healthy individuals and FEP patients, with patients displaying widespread cognitive impairment.

Latent structure of cognition in schizophrenia: a confirmatory factor analysis of the MATRICS Consensus Cognitive Battery (MCCB)

BACKGROUND

The number of separable cognitive dimensions in schizophrenia has been debated. Guided by the extant factor analytic literature, the NIMH Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) initiative selected seven cognitive domains relevant to treatment studies in schizophrenia: speed of processing, attention/vigilance, working memory, verbal learning, visual learning, reasoning and problem solving, and social cognition. These domains are assessed in the MATRICS Consensus Cognitive Battery (MCCB). The aim of this study was to conduct a confirmatory factor analysis (CFA) of the beta battery of the MCCB to compare the fit of the MATRICS consensus seven-domain model to other models in the current literature on cognition in schizophrenia.

METHOD

Using data from 281 schizophrenia outpatients, we compared the seven correlated factors model with alternative models. Specifically, we compared the 7-factor model to (a) a single-factor model, (b) a three correlated factors model including speed of processing, working memory, and general cognition, and (c) a hierarchical model in which seven first-order factors loaded onto a second-order general cognitive factor.

RESULTS

Multiple fit indices indicated the seven correlated factors model was the best fit for the data and provided significant improvement in model fit beyond the comparison models.

CONCLUSIONS

These results support the assessment of these seven cognitive dimensions in clinical trials of interventions to improve cognition in schizophrenia. Because these cognitive factors are separable to some degree, it is plausible that specific interventions may have differential effects on the domains.

Factor structure and heritability of endophenotypes in schizophrenia: findings from the Consortium on the Genetics of Schizophrenia (COGS-1)

BACKGROUND

Although many endophenotypes for schizophrenia have been studied individually, few studies have examined the extent to which common neurocognitive and neurophysiological measures reflect shared versus unique endophenotypic factors. It may be possible to distill individual endophenotypes into composite measures that reflect dissociable, genetically informative elements.

METHODS

The first phase of the Consortium on the Genetics of Schizophrenia (COGS-1) is a multisite family study that collected neurocognitive and neurophysiological data between 2003 and 2008. For these analyses, participants included schizophrenia probands (n=83), their nonpsychotic siblings (n=151), and community comparison subjects (n=209) with complete data on a battery of 12 neurocognitive tests (assessing domains of working memory, declarative memory, vigilance, spatial ability, abstract reasoning, facial emotion processing, and motor speed) and 3 neurophysiological tasks reflecting inhibitory processing (P50 gating, prepulse inhibition and antisaccade tasks). Factor analyses were conducted on the measures for each subject group and across the entire sample. Heritability analyses of factors were performed using SOLAR.

RESULTS

Analyses yielded 5 distinct factors: 1) Episodic Memory, 2) Working Memory, 3) Perceptual Vigilance, 4) Visual Abstraction, and 5) Inhibitory Processing. Neurophysiological measures had low associations with these factors. The factor structure of endophenotypes was largely comparable across probands, siblings and controls. Significant heritability estimates for the factors ranged from 22% (Episodic Memory) to 39% (Visual Abstraction).

CONCLUSIONS

Neurocognitive measures reflect a meaningful amount of shared variance whereas the neurophysiological measures reflect largely unique contributions as endophenotypes for schizophrenia. Composite endophenotype measures may inform our neurobiological and genetic understanding of schizophrenia.

Refining the latent structure of neuropsychological performance in schizophrenia

BACKGROUND

Elucidating the cognitive architecture of schizophrenia promises to advance understanding of the clinical and biological substrates of the illness. Traditional cross-sectional neuropsychological approaches differentiate impaired from normal cognitive abilities but are limited in their ability to determine latent substructure. The current study examined the latent architecture of abnormal cognition in schizophrenia via a systematic approach.

METHOD

Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were carried out on a large neuropsychological dataset including the Brief Assessment of Cognition in Schizophrenia, Continuous Performance Test, Wisconsin Card Sorting Test, Benton Judgment of Line Orientation Test, and Wechsler Abbreviated Scale of Intelligence matrix reasoning derived from 1012 English-speaking ethnic Chinese healthy controls and 707 schizophrenia cases recruited from in- and out-patient clinics.

RESULTS

An initial six-factor model fit cognitive data in healthy and schizophrenia subjects. Further modeling, which accounted for methodological variance between tests, resulted in a three-factor model of executive functioning, vigilance/speed of processing and memory that appeared to best discriminate schizophrenia cases from controls. Factor analytic-derived g estimands and conventionally calculated g showed similar case-control discrimination. However, agreement analysis suggested systematic differences between both g indices.

CONCLUSIONS

Factor structures derived in the current study were broadly similar to those reported previously. However, factor structures between schizophrenia subjects and healthy controls were different. Roles of factor analytic-derived g estimands and conventional composite score g were further discussed. Cognitive structures underlying cognitive deficits in schizophrenia may prove useful for interrogating biological substrates and enriching effect sizes for subsequent work.

Effects of COMT genotype on cognitive ability and functional capacity in individuals with schizophrenia

Cognitive and functional impairments are core features of schizophrenia. This study examined the catechol-O-methyltransferase (COMT) genotype and its relationship to cognition and functional capacity in 188 individuals with schizophrenia or schizoaffective disorder. We found that in a dose-response fashion, individuals with more Met alleles performed significantly better on tests of learning/memory and abstraction. The effects of COMT genotype on cognition were modest, explaining about 3% of the variance in learning/memory and abstraction. Larger studies will be needed to examine the relationships between COMT and other genes and cognitive performance and everyday functioning.

Expression of DISC1-interactome members correlates with cognitive phenotypes related to schizophrenia

Cognitive dysfunction is central to the schizophrenia phenotype. Genetic and functional studies have implicated Disrupted-in-Schizophrenia 1 (DISC1), a leading candidate gene for schizophrenia and related psychiatric conditions, in cognitive function. Altered expression of DISC1 and DISC1-interactors has been identified in schizophrenia. Dysregulated expression of DISC1-interactome genes might, therefore, contribute to schizophrenia susceptibility via disruption of molecular systems required for normal cognitive function. Here, the blood RNA expression levels of DISC1 and DISC1-interacting proteins were measured in 63 control subjects. Cognitive function was assessed using neuropsychiatric tests and functional magnetic resonance imaging was used to assess the activity of prefrontal cortical regions during the N-back working memory task, which is abnormal in schizophrenia. Pairwise correlations between gene expression levels and the relationship between gene expression levels and cognitive function and N-back-elicited brain activity were assessed. Finally, the expression levels of DISC1, AKAP9, FEZ1, NDEL1 and PCM1 were compared between 63 controls and 69 schizophrenic subjects. We found that DISC1-interactome genes showed correlated expression in the blood of healthy individuals. The expression levels of several interactome members were correlated with cognitive performance and N-back-elicited activity in the prefrontal cortex. In addition, DISC1 and NDEL1 showed decreased expression in schizophrenic subjects compared to healthy controls. Our findings highlight the importance of the coordinated expression of DISC1-interactome genes for normal cognitive function and suggest that dysregulated DISC1 and NDEL1 expression might, in part, contribute to susceptibility for schizophrenia via disruption of prefrontal cortex-dependent cognitive functions.

Cluster analysis of cognitive deficits may mark heterogeneity in schizophrenia in terms of outcome and response to treatment

Cognitive impairments are central to schizophrenia, but their clinical utility for tagging heterogeneity in lifetime outcome and response to treatment is not conclusive. By exploiting four cognitive domains consistently showing large deficits in studies, we tested whether cluster analysis would define separate subsets of patients and then whether the disease heterogeneity marked by these clusters would be related to lifetime outcome and response to treatment. A total of 112 schizophrenia patients completed a neuropsychological evaluation. The PANSS, GAF-S and GAF-F were rated at the onset and endpoint of the illness trajectory. A blind judgment of the lifetime response to treatment was made. The first cluster presented near-normal cognitive performance. Two other clusters of severely impaired patients were identified: one generally impaired in the four cognitive domains and another selectively impaired in visual episodic memory and processing speed, each relating to a different lifetime evolution of disease and treatment response. Although the two impaired clusters were clinically indistinguishable in symptom severity and functioning at disease onset, patients with selective cognitive impairments demonstrated better improvement at outcome, whereas the generally impaired patients were more likely to be treatment refractory. The findings have implications for the management of patients and for clinical trials since particular combinations of cognitive deficits in patients would influence their treatment response.

Cognitive effects of methylphenidate in healthy volunteers: a review of single dose studies

Methylphenidate (MPH), a stimulant drug with dopamine and noradrenaline reuptake inhibition properties, is mainly prescribed in attention deficit hyperactivity disorder, is increasingly used by the general population, intending to enhance their cognitive function. In this literature review, we aim to answer whether this is effective. We present a novel way to determine the extent to which MPH enhances cognitive performance in a certain domain. Namely, we quantify this by a percentage that reflects the number of studies showing performance enhancing effects of MPH. To evaluate whether the dose-response relationship follows an inverted-U-shaped curve, MPH effects on cognition are also quantified for low, medium and high doses, respectively. The studies reviewed here show that single doses of MPH improve cognitive performance in the healthy population in the domains of working memory (65% of included studies) and speed of processing (48%), and to a lesser extent may also improve verbal learning and memory (31%), attention and vigilance (29%) and reasoning and problem solving (18%), but does not have an effect on visual learning and memory. MPH effects are dose-dependent and the dose-response relationship differs between cognitive domains. MPH use is associated with side effects and other adverse consequences, such as potential abuse. Future studies should focus on MPH specifically to adequately asses its benefits in relation to the risks specific to this drug.

Using the Brief Assessment of Cognition in Schizophrenia (BACS) to assess cognitive impairment in older patients with schizophrenia and bipolar disorder

OBJECTIVES

A growing body of evidence suggests that impairment in cognitive functioning is an important clinical feature of both schizophrenia and bipolar disorder, and that these cognitive alterations worsen with age. Although cognitive assessments are increasingly becoming a part of research and clinical practice in schizophrenia, a standardized and easily administered test battery for elderly patients with bipolar disorder is still lacking. The Brief Assessment of Cognition in Schizophrenia (BACS) captures those domains of cognition that are the most severely affected in patients with schizophrenia and the most strongly correlated with functional outcome. The primary aim of our study was to investigate the clinical usefulness of the BACS in assessing cognitive functioning in elderly euthymic patients with bipolar disorder, and to compare their cognitive profile to that of elderly patients with schizophrenia.

METHODS

Elderly euthymic patients with bipolar disorder or schizophrenia were assessed using the BACS and a standard cognitive test battery.

RESULTS

Fifty-seven elderly patients (aged 60 years and older) with bipolar disorder (n = 42) or schizophrenia (n = 15) were invited to participate. All of the patients were assessed by the BACS as being cognitively impaired. The patients with bipolar disorder scored significantly higher on the global scale and the verbal memory and attention sub-scores of the BACS than the patients with schizophrenia.

DISCUSSION

The BACS appears to be a feasible and informative cognitive assessment tool for elderly patients with bipolar disorder. We believe that these preliminary results merit further investigation.

"To see or not to see: that is the question." The "Protection-Against-Schizophrenia" (PaSZ) model: evidence from congenital blindness and visuo-cognitive aberrations

The causes of schizophrenia are still unknown. For the last 100 years, though, both “absent” and “perfect” vision have been associated with a lower risk for schizophrenia. Hence, vision itself and aberrations in visual functioning may be fundamental to the development and etiological explanations of the disorder. In this paper, we present the “Protection-Against-Schizophrenia” (PaSZ) model, which grades the risk for developing schizophrenia as a function of an individual's visual capacity. We review two vision perspectives: (1) “Absent” vision or how congenital blindness contributes to PaSZ and (2) “perfect” vision or how aberrations in visual functioning are associated with psychosis. First, we illustrate that, although congenitally blind and sighted individuals acquire similar world representations, blind individuals compensate for behavioral shortcomings through neurofunctional and multisensory reorganization. These reorganizations may indicate etiological explanations for their PaSZ. Second, we demonstrate that visuo-cognitive impairments are fundamental for the development of schizophrenia. Deteriorated visual information acquisition and processing contribute to higher-order cognitive dysfunctions and subsequently to schizophrenic symptoms. Finally, we provide different specific therapeutic recommendations for individuals who suffer from visual impairments (who never developed “normal” vision) and individuals who suffer from visual deterioration (who previously had “normal” visual skills). Rather than categorizing individuals as “normal” and “mentally disordered,” the PaSZ model uses a continuous scale to represent psychiatrically relevant human behavior. This not only provides a scientific basis for more fine-grained diagnostic assessments, earlier detection, and more appropriate therapeutic assignments, but it also outlines a trajectory for unraveling the causes of abnormal psychotic human self- and world-perception.

Neurocognitive profile and its association with psychopathology in first-degree relatives of patients with schizophrenia. a case-control study

BACKGROUND

People with schizophrenia show a broad range of neurocognitive deficits, which are considered as core features of the disorder and are thought to be partly heritable. Similar deficits, albeit at a lesser degree, have been also found in their healthy biological relatives. These deficits, if better characterized, might represent underlying vulnerable traits for psychosis.

METHODS

This case-control study compared neurocognitive functioning of adult first-degree relatives of patients with schizophrenia (SCZ-RELs) (n=55) with healthy control subjects (n=55) and explored its association with the negative symptoms. Subjects in both study and control group were assessed with an extensive neurocognitive test battery (Trail Making test, Phonemic Verbal fluency, Wisconsin Card Sorting Test, Bushke Fuld Test, Stroop Test, n-Back and Digit span) and a set of clinical measures (SANS, GAF and DAS).

RESULTS

SCZ-RELs were more significantly impaired on executive function tasks (i.e. Wisconsin Card Sorting Test and the Phonemic Verbal fluency) and displayed significantly more severe negative symptoms and poorer social functioning than control subjects. Significant correlations between neurocognitive measures and negative symptoms were found in the study group, whereas no significant correlations were detected among the controls.

DISCUSSION

Subtle executive impairments, associated with negative symptoms, are shown to be evident in healthy relatives of patients with schizophrenia. These deficits, which reflect subtle dysfunction in concept formation, flexibility and mental shifting, may be seen as potential phenotypic markers of vulnerability for schizophrenia. This raises the question of underlying prefrontal dysfunction as core feature of the disorder.

Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia

BACKGROUND

Recent research has identified impairment in processing speed, measured by the digit-symbol substitution task, as central to the cognitive deficit in schizophrenia. However, the underlying cognitive correlates of this impairment remain unknown.

METHODS

A sample of cases (N=125) meeting DSM-IV criteria for schizophrenia and a sample of community controls (N=272) from the same geographical area completed a set of putative measures of processing-speed ability to which we implemented confirmatory factor and structural regression modelling in order to elucidate the latent structure of processing speed. Next, we tested the degree to which the structural and relational portions of the model were equal across groups.

RESULTS

Processing-speed ability was best defined, in both controls and cases (χ(2)=38.59(26), p=0.053), as a multidimensional cognitive ability consisting of three latent factors comprising: psychomotor speed, sequencing and shifting, and verbal fluency. However, cases exhibited dedifferentiation (i.e., markedly stronger inter-correlations between factors; χ(2)=59.94(29), p<.01) and a reliance on an alternative ensemble of cognitive operations to controls when completing the digit-symbol substitution task.

CONCLUSION

Dedifferentiation of processing-speed ability in schizophrenia and subsequent overreliance on alternative (and possibly less than optimal) cognitive operations underlies the marked deficit observed on the digit-symbol substitution task.

Using confirmatory factor analysis to measure contemporaneous activation of defined neuronal networks in functional magnetic resonance imaging

Functional neuroimaging often generates large amounts of data on regions of interest. Such data can be addressed effectively with a widely-used statistical technique based on measurement theory that has not yet been applied to neuroimaging. Confirmatory factor analysis is a convenient hypothesis-driven modeling environment that can be used to conduct formal statistical tests comparing alternative hypotheses regarding the elements of putative neuronal networks. In such models, measures of each activated region of interest are treated as indicators of an underlying latent construct that represents the contemporaneous activation of the elements in the network. As such, confirmatory factor analysis focuses analyses on the activation of hypothesized networks as a whole, improves statistical power by modeling measurement error, and provides a theory-based approach to data reduction with a robust statistical basis. This approach is illustrated using data on seven regions of interest in a hypothesized mesocorticostriatal reward system in a sample of 262 adult volunteers assessed during a card-guessing reward task. A latent construct reflecting contemporaneous activation of the reward system was found to be significantly associated with a latent construct measuring impulsivity, particularly in males.

Cognitive factor structure and invariance in people with schizophrenia, their unaffected siblings, and controls

INTRODUCTION

Separable, but positively correlated, factors emerge from analyses of cognitive test data in schizophrenia and control samples (eg, verbal memory and processing speed) and these factors guide data reduction. Additionally, data support a hierarchical model of cognitive performance, in which these correlations reflect the influence of a higher-order factor, referred to as "g." We tested these findings in large, carefully screened samples of people with schizophrenia (n = 496), their unaffected siblings (n = 504), and controls (n = 823). Furthermore, we tested the hypothesis that cognitive performance in schizophrenia is more generalized across domains than among siblings and controls.

METHOD

A combination of exploratory and confirmatory factor analyses (EFA and CFA) and multiple groups CFA (MCFA) was used.

RESULTS

EFA yielded factors for verbal memory, visual memory, processing speed, working memory span, nback performance, and card sorting. The solution was consistent across groups, in terms of the factor assignments of individual cognitive variables and the magnitude of loadings. Method variance may have contributed to the card sorting, visual memory, and nback factors. CFA indicated that the hierarchical model, incorporating a "g" factor, was a good fit for data from all groups. MCFA suggested that this hierarchical structure was fully invariant for controls and siblings. While the variable/factor loadings for the schizophrenia group also were invariant with comparison groups, factor/"g" loadings were higher in schizophrenia, as were correlations among factor-based composite scores.

CONCLUSIONS

Cognitive variables sort into domains consistently in schizophrenia, unaffected siblings, and controls. However, performance in schizophrenia is more generalized and less domain specific.

Semantic fluency and executive functions as candidate endophenotypes for the early diagnosis of schizophrenia in Han Chinese

Neurocognitive deficits are recognized as core features of schizophrenia. The aim of this study was to compare the cognitive performance of antipsychotic, drug-naive patients with first-episode schizophrenia (FES patients) to their healthy siblings and to healthy controls from the Han Chinese population for exploring potential endophenotypes for the early detection of schizophrenia. A battery of cognitive assessment tools was used to measure seven cognitive domains in matched groups consisting of 56 subjects each. Cognitive tests included the grooved pegboard test (GPT), the category fluency test (CFT), the trail making test A (TMT-A), the Wechsler memory scale-III spatial span test (WMS-III SST), the Hopkins verbal learning test-revised (HVLT-R), the brief visuospatial memory test-revised (BVMT-R), the paced auditory serial addition test (PASAT), and the Wisconsin card sorting test-64 cards version (WCST-64). The performances of FEP patients were inferior to normal controls on all neuropsychological tests, while siblings were lower than healthy controls in many of the same tasks. Patients' performances were lower than siblings' on all tests except for the CFT, the WMS-III SST backward test, and four subtests of the WCST-64. Our data suggest that FEP patients exhibited pronounced impairment of fine motor skills, speed of processing, attention, verbal memory, visual memory, and executive function, while siblings exhibited deficits intermediate between those of schizophrenic patients and the control group. Semantic fluency function and executive function may be potential endophenotypes for the early diagnosis of schizophrenia.

Spanish validation of the Brief Assessment in Cognition in Schizophrenia (BACS) in patients with schizophrenia and healthy controls

Neurocognitive impairment is a core feature of schizophrenia and is closely associated with functional outcome. The importance of cognitive assessment is broadly accepted today, and an easy-to-use, internationality validated cognitive assessment tool is needed by researchers and in daily clinical practice. The Brief Assessment of Cognition in Schizophrenia (BACS) has been validated in English, French, Japanese and Italian. It is as sensitive to cognitive dysfunction as a standard test battery, with the advantage of requiring less than 35minutes to complete. In our study, we tested the psychometric characteristics of a Spanish version of the BACS in 117 patients with schizophrenia-spectrum disorders and 36 healthy controls. All BACS cognitive subtests discriminated between patients and controls (P<.001), and the concurrent validity between the BACS and a traditional neuropsychological test battery was similar to that reported in other languages. We conclude that the BACS can facilitate the comparison of the cognitive performance of patients with schizophrenia in many different countries.

A brief cognitive assessment tool for schizophrenia: construction of a tool for clinicians

Cognitive impairment in schizophrenia is often severe, enduring, and contributes significantly to chronic disability. But clinicians have difficulty in assessing cognition due to a lack of brief instruments. We evaluated whether a brief battery of cognitive tests derived from larger batteries could generate a summary score representing global cognitive function. Using data from 3 previously published trials, we calculated the corrected item-total correlations (CITCs) or the correlation of each test with the battery total score. We computed the proportion of variance that each test shares with the global score excluding that test (R(t)(2)=CITC(2)) and the variance explained per minute of administration time for each test (R(t)(2)/min). The 3 tests with the highest R(t)(2)/min were selected for the brief battery. The composite score from the trail making test B, category fluency, and digit symbol correlated .86 with the global score of the larger battery in 2 of the studies and correlated between .73 and .82 with the total battery scores excluding these 3 tests. A Brief Cognitive Assessment Tool for Schizophrenia (B-CATS) using the above 3 tests can be administered in 10-11 min. The full batteries of the larger studies have administration times ranging from 90 to 210 min. Given prior research suggesting that a single factor of global cognition best explains the pattern of cognitive deficit in schizophrenia, an instrument like B-CATS can provide clinicians with meaningful data regarding their patients' cognitive function. It can also serve researchers who want an estimate of global cognitive function without requiring a full neuropsychological battery.

Neurocognitive prediction of illness knowledge after psychoeducation in schizophrenia: results from the Munich COGPIP study

BACKGROUND

Many patients with schizophrenia exhibit neurocognitive impairments, namely, in attentional, mnestic and executive functions. While these deficits limit psychosocial rehabilitation, their effect on psychoeducation is unknown. Within the framework of the longitudinal Munich Cognitive Determinants of Psychoeducation and Information in Schizophrenic Psychoses (COGPIP) study, we examined: (a) whether illness knowledge after psychoeducation could be predicted more precisely from the neurocognitive than from the psychopathological status of the patients; (b) which neurocognitive domains are best predictors.

METHOD

A total of 116 in-patients with schizophrenic or schizoaffective disorders were randomized to a neurocognitive training or control condition (2 weeks) followed by a manualized psychoeducational group programme (4 weeks) and then observed over a 9-month follow-up. Repeated measurements included - among others - the Positive and Negative Syndrome Scale and a comprehensive neuropsychological test battery from which normative T scores were used to calculate one global and five domain-specific neurocognitive composite scores. Illness knowledge was measured by a questionnaire (WFB-52) tailored to the psychoeducational programme.

RESULTS

Multiple linear regression analyses showed that, apart from baseline illness knowledge, neurocognition significantly predicted knowledge outcome as well as knowledge gain (measured by reliable change indices) after psychoeducation. This was not true for psychopathology. Among the domain-specific neurocognitive composite scores, only memory acquisition was a significant predictor of knowledge outcome and gain.

CONCLUSIONS

Neurocognition, not psychopathology, is a significant predictor of illness knowledge after psychoeducation in schizophrenia. This finding should guide efforts to tailor psychoeducational interventions more closely to the patient's needs and resources.

Evolution of neuropsychological dysfunction during the course of schizophrenia and bipolar disorder

BACKGROUND

Neurocognitive dysfunction in schizophrenia (SZ), bipolar (BD) and related disorders represents a core feature of these illnesses, possibly a marker of underlying pathophysiology. Substantial overlap in domains of neuropsychological deficits has been reported among these disorders after illness onset. However, it is unclear whether deficits follow the same longitudinal pre- and post-morbid course across diagnoses. We examine evidence for neurocognitive dysfunction as a core feature of all idiopathic psychotic illnesses, and trace its evolution from pre-morbid and prodromal states through the emergence of overt psychosis and into chronic illness in patients with SZ, BD and related disorders.

METHOD

Articles reporting on neuropsychological functioning in patients with SZ, BD and related disorders before and after illness onset were reviewed. Given the vast literature on these topics and the present focus on cross-diagnostic comparisons, priority was given to primary data papers that assessed cross-diagnostic samples and recent meta-analyses.

RESULTS

Patients with SZ exhibit dysfunction preceding the onset of illness, which becomes more pronounced in the prodrome and early years following diagnosis, then settles into a stable pattern. Patients with BD generally exhibit typical cognitive development pre-morbidly, but demonstrate deficits by first episode that are amplified with worsening symptoms and exacerbations.

CONCLUSIONS

Neuropsychological deficits represent a core feature of SZ and BD; however, their onset and progression differ between diagnostic groups. A lifetime perspective on the evolution of neurocognitive deficits in SZ and BD reveals distinct patterns, and may provide a useful guide to the examination of the pathophysiological processes underpinning these functions across disorders.

What is it like to be a person with schizophrenia in the social world? A first-person perspective study on Schizophrenic dissociality--part 1: state of the art

This is a critical review of research on the subjective experience of social dysfunction in persons with schizophrenia. Studies from the phenomenological and cognitive paradigms are examined, and significant outcomes and shortcomings are pointed out. Clinical phenomenologists have mainly interpreted schizophrenic dissociality as an anomaly of prereflexive attunement. The main shortcoming of phenomenological research is that it lacks adequate methodology to collect reliable data since most studies are based on the analysis of a few typical cases. Cognitivism has reliably documented disorders of social functioning in large-scale experimental studies. The main shortcoming of most cognitive paradigms is that they do not properly investigate the personal level of experience in real-world functioning. We conclude that there is a need to reliably collect data through quantitative as well as qualitative methodology as established and accepted by the scientific community in the area of schizophrenic dissociality, reflecting the subjective experiences of people with schizophrenia in the real world.

Premorbid tobacco smoking is associated with later age at onset in schizophrenia

Rates of cigarette smoking in individuals with schizophrenia well exceed those in the general population and in other mental illnesses. In the present study, we examined the relationship between smoking status, clinical characteristics and cognitive functions in 230 male Chinese schizophrenia patients. They were interviewed by experienced psychiatrists using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) (SCID-P). Clinical symptoms were rated using the Positive and Negative Syndrome Scale (PANSS), and the Revised Tolerance Questionnaire (RTQ) used to evaluate the severity of nicotine dependence. Nine neuropsychological tests were used to assess cognitive function. We found that never-smokers had a younger age at examination and earlier onset and longer duration of illness than smokers and ex-smokers. The age of initiation of regular smoking in patients was significantly earlier than their age of illness onset. We found that longer duration of illness was significantly associated with higher RTQ scores. Ex-smokers with schizophrenia performed significantly more poorly on the Stroop C test than smokers. The results imply that smoking may affect cognitive function and illness onset time in patients with schizophrenia.

Genetic variation in FGF20 modulates hippocampal biology

We explored the effect of single-nucleotide polymorphisms (SNPs) in the fibroblast growth factor 20 gene (FGF20) associated with risk for Parkinson's disease on brain structure and function in a large sample of healthy young-adult human subjects and also in elderly subjects to look at the interaction between genetic variations and age (N = 237; 116 men; 18-87 years). We analyzed high-resolution anatomical magnetic resonance images using voxel-based morphometry, a quantitative neuroanatomical technique. We also measured FGF20 mRNA expression in postmortem human brain tissue to determine the molecular correlates of these SNPs (N = 108; 72 men; 18-74 years). We found that the T allele carriers of rs12720208 in the 3'-untranslated region had relatively larger hippocampal volume (p = 0.0059) and diminished verbal episodic memory (p = 0.048) and showed steeper decreases of hippocampal volume with normal aging (p = 0.026). In postmortem brain, T allele carriers had greater expression of hippocampal FGF20 mRNA (p = 0.037), consistent with a previously characterized microRNA mechanism. The C allele matches a predicted miR-433 microRNA binding domain, whereas the T allele disrupts it, resulting in higher FGF20 protein translation. The strong FGF20 genetic effects in hippocampus are presumably mediated by activation of the FGFR1 (FGF receptor 1), which is expressed in mammalian brain most abundantly in the hippocampus. These associations, from mRNA expression to brain morphology to cognition and an interaction with aging, confirm a role of FGF20 in human brain structure and function during development and aging.

Neurocognitive function in schizophrenia with comorbid posttraumatic stress disorder

Individuals with schizophrenia are at a greater risk for experiencing trauma and developing posttraumatic stress disorder (PTSD) than the general population. Despite an increased incidence of neurocognitive dysfunction in both schizophrenia and PTSD, there are few studies that have examined the potential compounding effects of these diagnoses when they co-occur. The current study examined this issue by administering comprehensive diagnostic, symptom, and neurocognitive evaluations to four groups including normal controls (C), as well as individuals with PTSD (PTSD), schizophrenia (SZ), or both schizophrenia and PTSD (SZP). Results indicated that when compared to the SZ group, the SZP group exhibited higher rates of positive symptoms, general psychopathology, and PTSD symptoms, as well as lower rates of negative symptoms. Regarding neurocognitive test performance, both schizophrenia groups performed significantly worse than the C and PTSD groups across all neurocognitive domains. However, differences were not significant between the SZP and SZ groups, although a differential pattern of performance between the groups was indicated. Results of this study do not support the idea that the presence of comorbid PTSD in SZ results in a substantial increase in cognitive impairment.

Cognitive profiles of healthy siblings of schizophrenia patients: application of the cognitive domains of the MATRICS consensus battery

Even though a large body of data suggests the presence of various types of cognitive deficits in the unaffected relatives of schizophrenia patients, more study is needed to clarify the comparative sensitivities of specific cognitive measures for relative-control differences. In this study, the authors compared the cognitive profiles of unaffected siblings of schizophrenia patients and those of patients and normal controls, and attempted to identify cognitive markers that might be associated with genetic liability to schizophrenia. Eighty-eight clinically stable schizophrenia patients, 44 healthy patient siblings, and 100 normal controls were evaluated using comprehensive neuropsychological tests. The domain structure of the MATRICS consensus cognitive battery was adopted, and both domain scores and individual test scores were used in the analysis. Performances of the sibling group were intermediate between those of patients and controls on most measures. A significant difference between the sibling and control groups was observed only in the Category Fluency Test. This cognitive deficit might be caused by familial predisposition to schizophrenia and could be a candidate of endophenotype for schizophrenia.

Factor structure of the neurocognitive tests: an application of the confirmative factor analysis in stabilized schizophrenia patients

The purpose of the present study was to identify the factor structure of neurocognitive tests used on schizophrenia patients by using the confirmative factor analysis, and to assess the factor score differences of schizophrenia patients and healthy controls. Comprehensive neurocognitive tests were administered to stabilized schizophrenia patients (N=114) and healthy controls (N=120). In the results of factor analyses on patients, the multifactorial-6-factor model, which included the speed of processing, working memory, verbal learning and memory, visual learning and memory, attention/vigilance, and reasoning/problem solving as suggested by the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS), showed the better goodness of fit than any of the other models tested. And assessing the group differences of factor scores, we found the patients performed worse than the controls in all factors, but the result showed meaningful variations of impairments across the cognitive factors. Our study identifies the six major domains with multifactorial structure of cognitive abilities in schizophrenia patients and confirms the distinctive impairment patterns of each cognitive domain. These results may have utility in better understanding the pathology of schizophrenia as well as in genetic studies.

Factor structures of the neurocognitive assessments and familial analysis in first-episode schizophrenia patients, their relatives and controls

OBJECTIVES

Schizophrenia patients have a wide range of cognitive deficits. To explore the structure of these deficits and index their psychometric properties in order to define the major separable factors, exploratory factor analysis (EFA) was performed on a series of neuropsychological test results in a sample of Han Chinese first-episode schizophrenia patients, their relatives and controls without mental illness.

METHODS

The factors derived from the composite sample were tested with confirmatory factor analysis (CFA) in each of the subsamples. The heritability of each factor was estimated by using the mixed linear model in order to determine whether the common factor scores describe the familiarity of the data.

RESULTS

A six-factor model of general mental activity, sort and shift, attention and anti-interference, logical memory, reasoning and problem-solving/executive function, and visual reproduction were extracted and confirmed on EFA and CFA. There was a hierarchy in cognitive performance deficits in relatives depending on their relatedness to probands. Patients performed more poorly than siblings/offspring in general mental activity, sort and shift, attention and anti-interference, logical memory, planning and problem-solving, but not in visual reproduction. The logical memory domain was found to be significantly heritable (h(2)=0.34), and reasoning and problem-solving had a marginal heritability of around 0.19.

CONCLUSIONS

Generalized cognitive deficit accounts for the majority of the overall variance of cognitive deficits in schizophrenia. Estimates of heritability were modest. The present results also support the hypothesis that neurocognitive deficits of schizophrenia are familial and could serve as endophenotypes, especially logical memory, which is the most heritable.

A primate-specific, brain isoform of KCNH2 affects cortical physiology, cognition, neuronal repolarization and risk of schizophrenia

Organized neuronal firing is critical for cortical processing and is disrupted in schizophrenia. Using 5’ RACE in human brain, we identified a primate-specific isoform (3.1) of the K⁺-channel KCNH2 that modulates neuronal firing. KCNH2-3.1 mRNA levels are comparable to KCNH2-1A in brain, but 1000-fold lower in heart. In schizophrenic hippocampus, KCNH2-3.1 expression is 2.5-fold greater than KCNH2-1A. A meta-analysis of 5 clinical samples (367 families, 1158 unrelated cases, 1704 controls) shows association of SNPs in KCNH2 with schizophrenia. Risk-associated alleles predict lower IQ scores and speed of cognitive processing, altered memory-linked fMRI signals, and increased KCNH2-3.1 expression in post-mortem hippocampus. KCNH2-3.1 lacks a domain critical for slow channel deactivation. Overexpression of KCNH2-3.1 in primary cortical neurons induces a rapidly deactivating K⁺ current and a high-frequency, non-adapting firing pattern. These results identify a novel KCNH2 channel involved in cortical physiology, cognition, and psychosis, providing a potential new psychotherapeutic drug target.

Genetic variation in AKT1 is linked to dopamine-associated prefrontal cortical structure and function in humans

AKT1-dependent molecular pathways control diverse aspects of cellular development and adaptation, including interactions with neuronal dopaminergic signaling. If AKT1 has an impact on dopaminergic signaling, then genetic variation in AKT1 would be associated with brain phenotypes related to cortical dopaminergic function. Here, we provide evidence that a coding variation in AKT1 that affects protein expression in human B lymphoblasts influenced several brain measures related to dopaminergic function. Cognitive performance linked to frontostriatal circuitry, prefrontal physiology during executive function, and frontostriatal gray-matter volume on MRI were altered in subjects with the AKT1 variation. Moreover, on neuroimaging measures with a main effect of the AKT1 genotype, there was significant epistasis with a functional polymorphism (Val158Met) in catechol-O-methyltransferase [COMT], a gene that indexes cortical synaptic dopamine. This genetic interaction was consistent with the putative role of AKT1 in dopaminergic signaling. Supportive of an earlier tentative association of AKT1 with schizophrenia, we also found that this AKT1 variant was associated with risk for schizophrenia. These data implicate AKT1 in modulating human prefrontal-striatal structure and function and suggest that the mechanism of this effect may be coupled to dopaminergic signaling and relevant to the expression of psychosis.

False positives in imaging genetics

Imaging genetics provides an enormous amount of functional-structural data on gene effects in living brain, but the sheer quantity of potential phenotypes raises concerns about false discovery. Here, we provide the first empirical results on false positive rates in imaging genetics. We analyzed 720 frequent coding SNPs without significant association with schizophrenia and a subset of 492 of these without association with cognitive function. Effects on brain structure (using voxel-based morphometry, VBM) and brain function, using two archival imaging tasks, the n-back working memory task and an emotional face matching task, were studied in whole brain and regions of interest and corrected for multiple comparisons using standard neuroimaging procedures. Since these variants are unlikely to impact relevant brain function, positives obtained provide an upper empirical estimate of the false positive association rate. In a separate analysis, we randomly permuted genotype labels across subjects, removing any true genotype-phenotype association in the data, to derive a lower empirical estimate. At a set correction level of 0.05, in each region of interest and data set used, the rate of positive findings was well below 5% (0.2-4.1%). There was no relationship between the region of interest and the false positive rate. Permutation results were in the same range as empirically derived rates. The observed low rates of positives provide empirical evidence that the type I error rate is well controlled by current commonly used correction procedures in imaging genetics, at least in the context of the imaging paradigms we have used. In fact, our observations indicate that these statistical thresholds are conservative.