Wisconsin Card Sorting Test: an indicator of vulnerability to schizophrenia?

Improving outcome of treatment-resistant schizophrenia: effects of cognitive remediation therapy

Treatment-Resistant Schizophrenia (TRS) represents a main clinical issue, associated with worse psychopathological outcomes, a more disrupted neurobiological substrate, and poorer neurocognitive performance across several domains, especially in verbal abilities. If cognitive impairment is a major determinant of patients' functional outcomes and quality of life, targeting cognitive dysfunction becomes even more crucial in TRS patients in order to minimize cognitive and functional deterioration. However, although Cognitive Remediation Therapy (CRT) represents the best available tool to treat cognitive dysfunction in schizophrenia, specific evidence of its efficacy in TRS is lacking. Based on these premises, our study aimed at investigating possible differences in CRT outcomes in a sample of 150 patients with schizophrenia, stratified according to antipsychotic response (TRS vs. non-TRS). Subjects were assessed for neurocognition through Brief Assessment of Cognition in Schizophrenia (BACS) and the Wisconsin Card Sorting Test (WCST) at baseline and after CRT. As expected, we observed greater baseline impairment among TRS patients in BACS-Verbal Memory and WCST-Executive Functions. Repeated measures ANCOVAs showed significant within-group pre-/post-CRT differences in the above-mentioned domains, both among non-TRS and TRS subjects. However, after CRT, no differences were observed between groups. This is the first study to indicate that CRT represents a highly valuable resource for TRS patients, since it may be able to fill the cognitive gap between treatment response groups. Our finding further highlights the importance of early implementation of CRT in addition to pharmacotherapy to reduce the cognitive and functional burden associated with the disease, especially for TRS patients.

New Insights Regarding Diagnosis and Medication for Schizophrenia Based on Neuronal Synapse-Microglia Interaction

Schizophrenia is a common psychiatric disorder that usually develops during adolescence and young adulthood. Since genetic and environmental factors are involved in the disease, the molecular status of the pathology of schizophrenia differs across patients. Recent genetic studies have focused on the association between schizophrenia and the immune system, especially microglia–synapse interactions. Microglia physiologically eliminate unnecessary synapses during the developmental period. The overactivation of synaptic pruning by microglia is involved in the pathology of brain disease. This paper focuses on the synaptic pruning function and its molecular machinery and introduces the hypothesis that excessive synaptic pruning plays a role in the development of schizophrenia. Finally, we suggest a strategy for diagnosis and medication based on modulation of the interaction between microglia and synapses. This review provides updated information on the involvement of the immune system in schizophrenia and proposes novel insights regarding diagnostic and therapeutic strategies for this disease.

Neurocognitive and linguistic correlates of positive and negative formal thought disorder: A meta-analysis

Executive dysfunction and language impairment are the most prominent neuropsychological models of formal thought disorder (FTD) in schizophrenia. However, available studies have provided contradictory findings regarding the accuracy of these models. Furthermore, specific neurocognitive underpinnings of positive FTD (PosFTD) and negative FTD (NegFTD) are not clear. Following the systematic review of schizophrenia studies, a random-effects meta-analysis of the relationship between FTD and neurocognition/language in schizophrenia was conducted in 52 reports including 2805 patients. Neurocognition was significantly associated with both PosFTD (r = -0.21, CI = -0.14 to -0.27) and NegFTD (r = -0.24, CI = -0.18 to -0.30). Both PosFTD (r = ranged from -0.18 to -0.27) and NegFTD (r = ranged from -0.19 to -0.23) were significantly correlated with verbal memory, visual memory, attention, and processing speed. In meta-analyses of executive functions, PosFTD was significantly associated with working memory (r = -0.21), planning (r = -0.19), and inhibition (r = -0.21) and NegFTD was significantly associated with planning (r = -0.27), fluency (r = -0.27), and working memory (r = -0.24). In meta-analyses of linguistic variables, PosFTD was associated with deficits in syntactic comprehension (r = -0.27) and semantic processing (r = -0.18). In contrast, NegFTD was associated only with semantic comprehension (r = -0.21). Both PosFTD and NegFTD were significantly associated with executive dysfunction, neurocognitive deficits and semantic dysfunction but syntactic deficits were more specific to PosFTD. There were also some distinct patterns of relationships between the pattern of executive dysfunction and types of FTD. Fluency deficit was associated more strongly with NegFTD and poor inhibition was more specifically related to PosFTD. Current findings suggest that neurocognitive and linguistic correlates of PosFTD and NegFTD might be partly different.

mGluR5 positive allosteric modulation and its effects on MK-801 induced set-shifting impairments in a rat operant delayed matching/non-matching-to-sample task

RATIONALE

Positive allosteric modulators (PAMs) of type 5 metabotropic glutamate receptors (mGluR5) exert pro-cognitive effects in animal models of various neuropsychiatric diseases. However, few studies to date have examined ability of mGluR5 PAMs to reverse cognitive deficits in operant delayed matching/non-matching-to-sample (DMS/DNMS) tasks.

OBJECTIVES

This study aims to determine the ability of the mGluR5 PAM 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) to reverse set-shifting deficits induced by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801.

METHODS

Male Sprague-Dawley rats were initially trained to lever press for sucrose reinforcement under either DMS or DNMS conditions. Following successful acquisition of the task, reinforcement conditions were reversed (DNMS → DMS or DMS → DNMS). In Experiment 1, rats were treated daily prior to each session with vehicle/vehicle, vehicle/MK-801 (0.06 mg/kg) simultaneously, CDPPB (20 mg/kg)/MK-801 simultaneously, or CDPPB 30 min prior to MK-801. In Experiment 2, rats were treated with either vehicle/vehicle, vehicle/MK-801, or CDPPB 30 min prior to MK-801 only prior to sessions that followed task reversal.

RESULTS

In Experiment 1, no group differences in initial task acquisition were observed. Rats treated with vehicle/MK-801 showed significant set-shifting impairments following task reversal, which were partially attenuated by simultaneous administration of CDPPB/MK-801 and completely precluded by administration of CDPPB 30 min prior to MK-801. In Experiment 2, MK-801 did not impair reversal learning, and no other group differences were observed.

CONCLUSIONS

MK-801-induced deficits in operant set-shifting ability were prevented by pretreatment with CDPPB. MK-801 did not produce deficits in task learning when treatment was initiated following task reversal.

Identifying cognitive remediation change through computational modelling--effects on reinforcement learning in schizophrenia

OBJECTIVE

Converging research suggests that individuals with schizophrenia show a marked impairment in reinforcement learning, particularly in tasks requiring flexibility and adaptation. The problem has been associated with dopamine reward systems. This study explores, for the first time, the characteristics of this impairment and how it is affected by a behavioral intervention-cognitive remediation.

METHOD

Using computational modelling, 3 reinforcement learning parameters based on the Wisconsin Card Sorting Test (WCST) trial-by-trial performance were estimated: R (reward sensitivity), P (punishment sensitivity), and D (choice consistency). In Study 1 the parameters were compared between a group of individuals with schizophrenia (n = 100) and a healthy control group (n = 50). In Study 2 the effect of cognitive remediation therapy (CRT) on these parameters was assessed in 2 groups of individuals with schizophrenia, one receiving CRT (n = 37) and the other receiving treatment as usual (TAU, n = 34).

RESULTS

In Study 1 individuals with schizophrenia showed impairment in the R and P parameters compared with healthy controls. Study 2 demonstrated that sensitivity to negative feedback (P) and reward (R) improved in the CRT group after therapy compared with the TAU group. R and P parameter change correlated with WCST outputs. Improvements in R and P after CRT were associated with working memory gains and reduction of negative symptoms, respectively.

CONCLUSION

Schizophrenia reinforcement learning difficulties negatively influence performance in shift learning tasks. CRT can improve sensitivity to reward and punishment. Identifying parameters that show change may be useful in experimental medicine studies to identify cognitive domains susceptible to improvement.

Assessment of cognition in non-affected full biological siblings of patients with schizophrenia

BACKGROUND

Schizophrenia is a devastating psychotic illness which is like the most mental disorders, shows complex inheritance; the transmission of the disorder most likely involves several genes and environmental factors. It is difficult to judge whether a particular person without schizophrenia has predisposing factors for the said disease. A few studies have shown the relative sensitivity and reliability of cognitive and psychophysiological markers of brain function as the susceptibility factors for schizophrenia which may aid us to find people with an increased risk of complex disorders like schizophrenia. The present work is an exploration on cognitive impairments in unaffected siblings of patients suffering from schizophrenia with a framework to explore why a mental disorder occurs in some families but not in others.

MATERIALS AND METHODS

This is a single point non-invasive study of non-affected full biological siblings of patients with schizophrenia, involving administration of a battery of neuropsychological tests to assess the cognitive function in the sibling group and a control group of volunteers with no history of psychiatric illness. The control group was matched for age, gender, and education. The siblings were also divided on the basis of the type of schizophrenia their siblings (index probands) were suffering from and their results compared with each other.

RESULTS

The siblings performed significantly poorly as compared to the controls on Wisconsin card sorting test (WCST), continuous performance test (CPT), and spatial working memory test (SWMT). The comparison between the sibling subgroups based on the type of schizophrenia in the index probands did not reveal any significant difference.

CONCLUSION

These findings suggest that there is a global impairment in the cognition of the non-affected siblings of patients of schizophrenia. Cognitive impairment might be one of the factors which will help us to hit upon people who are predisposed to develop schizophrenia in the future.

Spontaneous gamma coherence as a possible trait marker of schizophrenia-An explorative study

OBJECTIVES

Integration of sensory information by cortical network binding appears to be crucially involved in sensory processing activity. Studies in schizophrenia using functional neuroimaging, event-related potentials and EEG coherence indicate an impairment of cortical network coupling in this disorder. Previous electrophysiological investigations in animals and humans suggested that gamma activity (oscillations at around 30-100Hz) is essential for cortical network binding. This is the first investigation of spontaneous gamma activity in schizophrenics and their first degree relatives as compared to normal controls.

METHOD

Resting EEG was recorded in 20 drug naïve/drug free male schizophrenic patients, their pair matched male first degree relatives and 20 age-, sex-, education- and handedness-matched normal controls. Power spectrum and coherence of gamma band activity was analysed using MATLAB 6.5.

RESULTS

Schizophrenic patients had significantly less interhemispheric spontaneous gamma coherence and increased gamma power compared to normal controls. But there was no significant difference in gamma coherence between patients and their first degree relatives. Spontaneous gamma coherence had significant correlation with few PANSS subscale scores.

CONCLUSIONS

There is cortical hyperactivation and a reduced spontaneous and induced gamma coherence abnormality in schizophrenia. The abnormal gamma coherence appears explaining the psychopathology and poor performance on cognitive task in schizophrenia. This study has also generated hypotheses that the gamma band abnormality may be a trait abnormality in schizophrenics as seen by the similarity between the patient and their clinically asymptomatic first degree relatives.

White matter abnormalities and animal models examining a putative role of altered white matter in schizophrenia

Schizophrenia is a severe mental disorder affecting about 1% of the population worldwide. Although the dopamine (DA) hypothesis is still keeping a dominant position in schizophrenia research, new advances have been emerging in recent years, which suggest the implication of white matter abnormalities in schizophrenia. In this paper, we will briefly review some of recent human studies showing white matter abnormalities in schizophrenic brains and altered oligodendrocyte-(OL-) and myelin-related genes in patients with schizophrenia and will consider abnormal behaviors reported in patients with white matter diseases. Following these, we will selectively introduce some animal models examining a putative role of white matter abnormalities in schizophrenia. The emphasis will be put on the cuprizone (CPZ) model. CPZ-fed mice show demyelination and OLs loss, display schizophrenia-related behaviors, and have higher DA levels in the prefrontal cortex. These features suggest that the CPZ model is a novel animal model of schizophrenia.

Executive function impairment in first-degree relatives of persons with schizophrenia: A meta-analysis of controlled studies

A meta-analysis of past research evaluated the relationship between deficits in executive functioning among unaffected first-degree relatives of schizophrenia patients and healthy controls. The Wisconsin Cart Sorting Test (WCST), a reliable measurement of cognition and abstract thinking, was examined as the dependent variable. Unaffected first-degree relatives perform worse than controls on two important dimensions of the WCST. They achieve significantly less categories and significantly more perseverative errors.

Disorganization and reality distortion in schizophrenia: a meta-analysis of the relationship between positive symptoms and neurocognitive deficits

BACKGROUND

Factor analytic studies have shown that in schizophrenia patients, disorganization (e.g., conceptual disorganization and bizarre behavior) is a separate dimension from other types of positive symptoms such as reality distortion (delusions and hallucinations). Although some studies have found that disorganization is more strongly linked to neurocognitive deficits and poor functional outcomes than reality distortion, the findings are not always consistent.

METHODS

A meta-analysis of 104 studies (combined n=8015) was conducted to determine the magnitude of the relationship between neurocognition and disorganization as compared to reality distortion. Additional analyses were conducted to determine whether the strength of these relationships differed depending on the neurocognitive domain under investigation.

RESULTS

The relationship between reality distortion and neurocognition was weak (r=-.04; p=.03) as compared to the moderate association between disorganization and neurocognition (r=-.23; p<.01). In each of the six neurocognitive domains that were examined, disorganization was more strongly related to neurocognition (r's range from -.20 to -.26) than to reality distortion (r's range from .01 to -.12).

CONCLUSIONS

The effect size of the relationship between neurocognition and disorganization was significantly larger than the effect size of the relationship between neurocognition and reality distortion. These results hold across several neurocognitive domains. These findings support a dimensional view of positive symptoms distinguishing disorganization from reality distortion.

Haloperidol activates quiescent oligodendroglia precursor cells in the adult mouse brain

Recent human studies suggest that abnormal development of oligodendrocytes (OLs) is an important component in the pathophysiology of schizophrenia. However, less information is available regarding effects of antipsychotics on OLs' development. In the present study, young adult C57BL/6 mice were given haloperidol (HAL; 2mg/kg/day) in their drinking water for three or six weeks. At the conclusion of the drug treatment, mice were sacrificed and the numbers of NG2- and Olig2-expressing cells in the brain regions of the corpus callosum, hippocampus and cerebral cortex were quantified. NG2 is a specific marker for oligodendroglia precursor cells (OPCs); Olig2 marks glial progenitors. HAL treatment for three weeks increased the number of NG2-expressing cells in the corpus callosum; HAL treatment for three and six weeks increased the numbers of Olig2-expressing cells in all three brain regions and increased the levels of Olig2 expression in the same brain regions. These results suggest that HAL treatment activates adult OPCs, which divide infrequently under normal conditions but respond to a variety of insulting factors by proliferation and differentiation. However, our further observations showed no changes in the number of mature OLs and the amount of myelin basic protein in HAL-treated mice, suggesting the drug treatment has no effect on the maturation of OLs. In addition, HAL treatment did not increase the numbers of GFAP- and CD68-expressing cells, suggesting that no gliosis and inflammatory responses occurred while the drug activated the quiescent OPCs in adult brain. These results suggest that HAL treatment may target the development of OLs.

Longitudinal alterations of executive function in non-psychotic adolescents at familial risk for schizophrenia

Genetic diathesis to schizophrenia may involve alterations of adolescent neurodevelopment manifesting as cognitive deficits. Brain regions mediating executive function (fronto-striatal circuits) develop during adolescence while those supporting elementary aspects of attention (e.g. sustained focused attention) have a more protracted maturation beginning in childhood. We hence predicted that adolescents at risk for schizophrenia would show a failure of normal maturation of executive function. We prospectively assessed 18 offspring and 6 siblings of schizophrenia patients (HR) and 28 healthy controls at baseline, year-1 and year-2 follow-up using the Continuous Performance Test [visual-d'] and Wisconsin Card Sort Test (WCST). Perseverative errors on the WCST in HR remained stable but decreased in controls over the follow-up (study-group by assessment-time interaction, p=0.01, controlling for IQ). No significant study-group by assessment-time interactions were seen for sustained attentional performance. HR may not improve while healthy subjects progressively improve on executive function during adolescence and early adulthood. Our results suggest an altered maturational trajectory of executive function during adolescence in individuals at familial risk for schizophrenia.

Behavioral and neurobiological changes in C57BL/6 mouse exposed to cuprizone: effects of antipsychotics

Recent human studies suggest a role for altered oligodendrocytes in the pathophysiology of schizophrenia. Our recent animal study has reported some schizophrenia-like behaviors in mice exposed to cuprizone (Xu et al., 2009), a copper chelator that has been shown to selectively damage the white matter. This study was to explore mechanisms underlying the behavioral changes in cuprizone-exposed mice and to examine effects of the antipsychotics haloperidol, clozapine and quetiapine on the changes in the mice. Mice given cuprizone for 14 days showed a deficit in the prepulse inhibition of acoustic startle response and higher dopamine in the prefrontal cortex (PFC), which changes were not seen in mice given cuprizone plus antipsychotics. Mice given cuprizone for 21 days showed lower spontaneous alternations in Y-maze, which was not seen in mice treated with cuprizone plus the antipsychotics. Mice given cuprizone for 28 days displayed less social interactions, which was not seen in mice given cuprizone plus clozapine/quetiapine, but was seen in mice given cuprizone plus haloperidol. Mice given cuprizone for 42 days showed myelin sheath loss and lower myelin basic protein in PFC, caudate putamen, and hippocampus. The white matter damage in PFC was attenuated in mice given cuprizone plus clozapine/haloperidol. But the white matter damage in caudate putamen and hippocampus was only attenuated by clozapine and quetiapine, not by haloperidol. These results help us to understand the behavioral changes and provide experimental evidence for the protective effects of antipsychotics on white matter damage in cuprizone-exposed mice.

Premorbid cognitive deficits in young relatives of schizophrenia patients

Neurocognitive deficits in schizophrenia (SZ) are thought to be stable trait markers that predate the illness and manifest in relatives of patients. Adolescence is the age of maximum vulnerability to the onset of SZ and may be an opportune "window" to observe neurocognitive impairments close to but prior to the onset of psychosis. We reviewed the extant studies assessing neurocognitive deficits in young relatives at high risk (HR) for SZ and their relation to brain structural alterations. We also provide some additional data pertaining to the relation of these deficits to psychopathology and brain structural alterations from the Pittsburgh Risk Evaluation Program (PREP). Cognitive deficits are noted in the HR population, which are more severe in first-degree relatives compared to second-degree relatives and primarily involve psychomotor speed, memory, attention, reasoning, and social-cognition. Reduced general intelligence is also noted, although its relationship to these specific domains is underexplored. Premorbid cognitive deficits may be related to brain structural and functional abnormalities, underlining the neurobiological basis of this illness. Cognitive impairments might predict later emergence of psychopathology in at-risk subjects and may be targets of early remediation and preventive strategies. Although evidence for neurocognitive deficits in young relatives abounds, further studies on their structural underpinnings and on their candidate status as endophenotypes are needed.

Leukemia inhibitory factor gene is associated with schizophrenia and working memory function

Leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family, regulates the neuronal phenotype and coordinates astrocyte, oligodendrocyte, microglia, and inflammatory cell responses. The LIF gene is located on 22q12.1-q12.2, a hot spot for schizophrenia. Three polymorphisms of the LIF gene (rs929271, rs737812, and rs929273) were examined in a case-control association study of 390 patients with schizophrenia and 410 age- and sex-matched controls. Effects of a risk genotype of LIF on cognitive domains were evaluated by the Wechsler Adult Intelligence Scale-Revised, Wechsler Memory Scale-Revised, and Wisconsin Card Sorting Test (WCST) in 355 healthy volunteers. The LIF gene showed significant associations with schizophrenia at rs929271 and a haplotype consisting of rs929271-rs737812. After stratification by subtype of schizophrenia, the hebephrenic, but not paranoid, type was associated with the LIF gene at rs929271 (allele, P=0.014) and the haplotype (permutation P=0.013). Having the T-allele and T-carrier genotypes (TT and TG) of rs929271 were risks for hebephrenic schizophrenia, and the odds ratios were 1.38 (95% CI: 1.21-1.56) and 1.54 (95%CI: 1.19-1.98), respectively. Subjects with T-carrier genotypes made significantly more errors on the WCST compared with those without (P=0.04). The present study indicated that the LIF gene variant may produce susceptibility to hebephrenic schizophrenia and deterioration of working memory function.

Downregulation of oligodendrocyte transcripts is associated with impaired prefrontal cortex function in rats

Abnormalities of brain white matter and oligodendroglia are among the most consistent findings in schizophrenia (Sz) research. Various gene expression microarray studies of post-mortem Sz brains showed a downregulation of myelin transcripts, while imaging and microscopy studies demonstrated decreases in prefrontal cortical (PFC) white matter volume and oligodendroglia density. Currently, the extent to which reduced oligodendrocyte markers contribute to pathophysiological domains of Sz is unknown. We exposed adolescent rats to cuprizone (CPZ), a copper chelator known to cause demyelination in mice, and examined expression of oligodendrocyte mRNA transcripts and PFC-mediated behavior. Rats on the CPZ diet showed decreased expression of mRNA transcripts encoding oligodendroglial proteins within the medial PFC, but not in the hippocampus or the striatum. These rats also displayed a specific deficit in the ability to shift between perceptual dimensions in the attentional set-shifting task, a PFC-mediated behavioral paradigm modeled after the Wisconsin Card Sorting Test (WCST). The inability to shift strategies corresponds to the deficits exhibited by Sz patients in the WCST. The results demonstrate that a reduction in oligodendrocyte markers is associated with impaired PFC-mediated behaviors. Thus, CPZ exposure of rats can serve as a model to examine the contribution of oligodendrocyte perturbation to cognitive deficits observed in Sz.

Symptoms as mediators of the relationship between neurocognition and functional outcome in schizophrenia: a meta-analysis

BACKGROUND

Neurocognitive functioning in schizophrenia has received considerable attention because of its robust prediction of functional outcome. Psychiatric symptoms, in particular negative symptoms, have also been shown to predict functional outcome, but have garnered much less attention. The high degree of intercorrelation among all of these variables leaves unclear whether neurocognition has a direct effect on functional outcome or whether that relationship to functional outcome is partially mediated by symptoms.

METHODS

A meta-analysis of 73 published English language studies (total n=6519) was conducted to determine the magnitude of the relationship between neurocognition and symptoms, and between symptoms and functional outcome. A model was tested in which symptoms mediate the relationship between neurocognition and functional outcome. Functional outcome involved measures of social relationships, school and work functioning, and laboratory assessments of social skill.

RESULTS

Although negative symptoms were found to be significantly related to neurocognitive functioning (p<.01) positive symptoms were not (p=.97). The relationship was moderate for negative symptoms (r=-.24, n=4757, 53 studies), but positive symptoms were not at all related to neurocogniton (r=.00, n=1297, 25 studies). Negative symptoms were significantly correlated with functional outcome (r=-.42, p<.01), and again the correlation was higher than for positive symptoms (r=-.03, p=.55). Furthermore, our findings support a model in which negative symptoms significantly mediate the relationship between neurocognition and functional outcome (Sobel test p<.01).

CONCLUSIONS

Although neurocognition and negative symptoms are both predictors of functional outcome, negative symptoms might at least partially mediate the relationship between neurocognition and outcome.

Endophenotypes in schizophrenia: a selective review

BACKGROUND

Given the wealth of data in the literature on schizophrenia endophenotypes, it is useful to have one source to reference their frequency data. We reviewed the literature on disease-liability associated variants in structural and functional magnetic resonance images (MRI), sensory processing measures, neuromotor abilities, neuropsychological measures, and physical characteristics in schizophrenia patients (SCZ), their first-degree relatives (REL), and healthy controls (HC). The purpose of this review was to provide a summary of the existing data on the most extensively published endophenotypes for schizophrenia.

METHODS

We searched PubMed and MedLine for all studies on schizophrenia endophenotypes comparing SCZ to HC and/or REL to HC groups. Percent abnormal values, generally defined as >2 SD from the mean (in the direction of abnormality) and/or associated effect sizes (Cohen's d) were calculated for each study.

RESULTS

Combined, the articles reported an average 39.4% (SD=20.7%; range=2.2-100%) of abnormal values in SCZ, 28.1% (SD=16.6%; range=1.6-67.0%) abnormal values in REL, and 10.2% (SD=6.7%; range=0.0-34.6%) in HC groups.

CONCLUSIONS

These findings are reviewed in the context of emerging hypotheses on schizophrenia endophenotypes, as well as a discussion of clustering trends among the various intermediate phenotypes. In addition, programs for future research are discussed, as instantiated in a few recent large-scale studies on multiple endophenotypes across patients, relatives, and healthy controls.

Is executive impairment associated with schizophrenic syndromes? A meta-analysis

BACKGROUND

A key neuropsychological proposal in schizophrenia is that negative and disorganization symptoms are associated with different patterns of impairment on executive tasks.

METHOD

Studies reporting correlations between positive, negative or disorganization symptoms and any type of executive test were meta-analysed. The influence of moderating factors was also examined, including age, treatment and stage of illness and whether symptoms were relapsing or persistent. The magnitudes of the correlations were compared with those for general intellectual impairment.

RESULTS

Pooled correlations between executive impairment and both negative symptoms and disorganization were significant in the small-to-moderate range. That for positive symptoms ('reality distortion'), however, was close to zero. The pattern of correlations among different executive tests differed significantly for negative symptoms and disorganization. Patients with stable clinical pictures showed significantly higher correlations with executive impairment than those with relapsing and remitting illnesses. Both negative symptoms and disorganization also correlated significantly with general intellectual function as indexed by current IQ.

CONCLUSIONS

Meta-analysis supports the view that negative symptoms and disorganization are associated with partially dissociable patterns of executive impairment. However, co-existent general intellectual impairment has been an important confounding factor in the studies to date.

Schizophrenia with obsessive-compulsive disorder and obsessive-compulsive disorder with poor insight: a neuropsychological comparison

Schizophrenia patients with obsessive-compulsive disorder (OCD) may be a subgroup of schizophrenia, and OCD patients with poor insight may show psychotic-like symptoms. The aim of this work is to compare the neuropsychological performance of those patients with schizophrenic patients who do not have OCD symptoms and with OCD patients who have good insight. The sample consisted of 89 patients (16 OCD-schizophrenic patients, 30 non-OCD schizophrenic patients, 30 OCD patients with good insight, 13 OCD patients with poor insight). Neuropsychological evaluation included executive functions, verbal and visual memory and attention tasks. While schizophrenic patients with OCD did not differ from the non-OCD schizophrenia and OCD with poor insight groups on long-term visual and verbal memory performance, they showed poorer performance than the OCD group on long-term visual and verbal memory tests. Considering executive function, the OCD group with poor insight performed significantly worse than their counterparts with good insight, and the latter group performed better than the schizophrenia patients. The results of this study suggest that the neuropsychological performance of schizophrenia patients with OCD did not differ from that of non-OCD schizophrenic patients, and that OCD patients with poor insight were more likely to share similar cognitive characteristics with the schizophrenia groups. Our results also provide neuropsychological support for the hypothesis that OCD and schizophrenia may be a spectrum disorders.

Impairment of motor dexterity in schizophrenia assessed by a novel finger movement test

Schizophrenia is characterized by a series of serious mental disturbances, including social, cognitive, and emotional dysfunctions. Although motor dysfunctions as well as the cognitive impairments in schizophrenia have been noted since the era of Kraepelin, little attention has been paid to motor dysfunctions until recently. Here, we examined the characteristics of motor dysfunctions and their relationship to other cognitive functions in schizophrenia. Subjects were 27 patients who met the DSM-IV criteria for schizophrenia and 49 healthy volunteers. A series of motor tests, i.e., pegboard, mirror drawing, normal drawing, and finger movement tests, were administered, and cognitive functions were assessed with the Wechsler Adult Intelligence Scale Revised, the Wechsler Memory Scale Revised and the Wisconsin Card Sorting Test. The finger movement test is a novel motor test that we developed to assess motor dexterity independent of motor speed. A stepwise discriminant analysis revealed that the finger movement and delayed recall tests were able to distinguish patients and controls most effectively. The scores of these two tests showed no correlation. Educational level was correlated with the delayed recall score, but not with the finger movement score. A significant difference was observed in the finger movement test score between inpatients and outpatients. There was no significant correlation between dosage of antipsychotic drugs and finger movement score in the patient group. The present results suggest that impairment in motor dexterity is a major characteristic of schizophrenia, which might be independent of cognitive functions.

Cognitive factors for predicting treatment response in schizophrenic patients: one-year follow-up study

OBJECTIVE

This study was conducted to investigate the cognitive factors that can longitudinally predict the response to treatment in patients with schizophrenia.

METHODS

The subjects were 49 patients with schizophrenia who were newly hospitalized in an acute psychiatry ward and had not been treated with medication for at least 8 weeks prior to the study. The symptoms and cognitive functions of the patients were evaluated at baseline before treatment (T0), at eight weeks after treatment (T1), and one year after treatment (T2). Clinical symptoms were assessed using the PANSS, and cognitive functions were estimated using the Vigilance Test, Cognitrone Test, Wisconsin Card Sorting Test (WCST), and the Korean version of the Memory Assessment Scales (K-MAS).

RESULTS

The patient group showed marked impairments in cognitive function when compared to the normal group, but the patients' clinical symptoms and cognitive functions improved after drug treatment. The patients also showed consistent improvement in verbal and nonverbal memory function as time progressed. Furthermore, there was a significant correlation between clinical symptoms and cognitive functions in the patient group. The cognitive variables that best predicted treatment response and prognosis were total errors on the WCST and immediate list recall component of the K-MAS. It was also shown that the number of total errors on the WCST was a better cognitive predictor than the number of errors in immediate recall.

CONCLUSION

The results of the present study show that the neurocognitive functions of patients with schizophrenia can be stabilized with treatment intervention, that treatment response is related to improvement in cognitive function, and that cognitive domains, especially executive function, can predict treatment response and prognosis in patients with schizophrenia.

Early detection and intervention of psychosis. A review

The vulnerability and hybrid models for the onset of psychosis are presented. Familial liability, perinatal and developmental factors, and decreased cognitive performance associate with psychosis in adolescence and young adulthood. Genetic predisposition connected with behavioural deviances and/or mental symptoms associate with psychotic development so strongly that monitoring and intervention are indicated. Especially, in families where one or both parents or other family members are severely mentally ill, early family-centred assessments and interventions is needed. Together with familial psychosis, deficits in adolescent and young adult social development indicate thorough assessment, intensive monitoring and often also preventive interventions. During the prodromal phase of psychosis, patients often display unspecific symptoms, such as anxiety and depression, personality disorders, abuse of alcohol or drugs. Social decline, possibly associated with neurocognitive deficits, frequently occurs in the prodromal phase or in the early course of schizophrenia. Among help-seeking patients, occurrence of the Basic Symptoms represent the early initial prodromal state, while the late initial prodome state includes attenuated psychotic symptoms, brief limited intermittent psychotic symptoms, and a first degree relative with psychotic disorder, or a schizotypal personality disorder, together with decrease global functioning. These patients suffer also from other mental symptoms and functional decline, and are clearly in need of psychiatric assessment and treatment. Intervention trials have shown that patients suffering from prodromal syndromes can be successfully treated, and onset of psychosis prevented or delayed. However, more large-scale studies and clinical case descriptions of treatment of patients with sub-threshold psychotic symptoms are needed.

Frontal release signs and cognition in people with schizophrenia, their siblings and healthy controls

BACKGROUND

Frontal release signs, a subset of neurological soft signs, are common in schizophrenia.

AIMS

To explore the relationship between frontal release signs and neuropsychological tests of frontal lobe function in people with schizophrenia, their siblings and healthy controls.

METHOD

Neuropsychological tests and frontal release signs were measured in a cohort of index cases (n=302), their siblings (n=240) and healthy controls (n=346).

RESULTS

The mean total score of frontal release signs was 1.5 (s.d.=1.58) in the schizophrenia group, 0.54 (s.d.=0.92) for siblings and 0.42 (s.d.=0.77) for controls. Schizophrenia group scores were greater than healthy control or sibling cohort scores (P < 0.0001), which did not differ. In all three cohorts, right grasp reflex scores positively correlated with number of perseverative errors on the Wisconsin Card Sort Task (P < 0.05). In the schizophrenia group, frontal release signs scores showed an inverse correlation with IQ (R=-0.199, P < 0.0005).

CONCLUSIONS

Our findings of relationships between frontal release signs and cognitive assays of cortical dysfunction and the increased frequency of these signs in people with schizophrenia implicate a cortical origin for these clinical signs and evidence of frontal lobe dysfunction in this disorder.

Which perspectives can endophenotypes and biological markers offer in the early recognition of schizophrenia?

The early recognition of schizophrenia seems crucial; various studies relate a longer duration-of-untreated-psychosis to a worse prognosis. We give an overview over common psychopathological early recognition instruments (BSABS, CAARMS, SIPS, IRAOS, ERIraos). However, many clinical symptoms of prodromal schizophrenia stages are not sufficiently specific. Thus we review recent contributions of neuroimaging and electrophysiological as well as genetic studies: which new diagnostic perspectives offer endophenotypes (such as P300, P50 sensory gating, MMN, smooth pursuit eye movements; indicating a specific genetic vulnerability) together with a better understanding of schizophrenic pathophysiology (state-dependent biological markers, e.g. aggravated motor neurological soft signs during psychosis) in prodromal schizophrenia when still ambiguous clinical symptoms are present. Several examples (e.g. from COMT polymorphisms to working memory deficits) illustrate more specific underlying neuronal mechanisms behind behavioural symptoms. This way, a characteristic pattern of disturbed cerebral maturation might be distinguished in order to complement clinical instruments of early schizophrenia detection.

Theory of mind, neurocognition, and functional status in schizotypy

The present study is the first to concurrently examine social cognition, neurocognition, and social functioning in psychometric schizotypes. Screening of 2108 undergraduates with the Schizotypal Personality Questionnaire-Brief (SPQ-B) identified 52 persons high in schizotypy and 40 persons low in schizotypy. All participants were administered a test battery designed to assess two elements of neurocognition, verbal secondary memory (California Verbal Learning Test) and executive functioning (Wisconsin Card Sorting Test), two elements of social cognition, emotion perception (The Awareness of Social Inference Test-Part 1) and theory of mind (The Awareness of Social Inference Test-Parts 2 and 3), and social functioning (Social Adjustment Scale-Self Report). Although the persons with high schizotypy were impaired in social functioning relative to the persons with low schizotypy, they were not impaired in theory of mind, emotion perception, verbal secondary memory, or executive functioning. Theory of mind and verbal secondary memory were correlated in persons with high schizotypy. The present findings suggest that psychometric schizotypes are not impaired in the domains of social cognition and neurocognition examined.

Cortical blood flow during rest and Wisconsin Card Sorting Test performance in schizophrenia

BACKGROUND

The aim of this study is to examine if patients with schizophrenia differ in prefrontal, orbitofrontal, temporal, parietal and occipital blood flow from healthy controls during performance of the Wisconsin Card Sorting Test (WCST).

METHODS

We conducted a 99mTc-hexamethylpropylene amine oxime-SPECT study in patients with schizophrenia (n = 21) and in healthy controls (n = 18). The assessment of relative regional cerebral blood flow (relCBF) was achieved by comparing blood flow of well-defined cortical regions to whole brain blood flow. relCBF at rest and during WCST was compared between the groups and in the groups.

RESULTS

Significant bilateral prefrontal and right-sided parietal increases of relCBF were found in patients (p < 0.05) during resting conditions, while prefrontal and parietal interhemispheric asymetry were higher in patients (p < 0.005). However, patients failed to increase right prefrontal and frontobasal relCBF as well as orbitofrontal interhemispheric asymetry during WCST performance in contrast to the control group (p < 0.05). The right occipital relCBF increased significantly in patients only (p < 0.05).

CONCLUSIONS

In our study we could confirm the common hypothesis of schizophrenic hypofrontality at rest and during WCST performance. Moreover, due to our method, we identified significant frontal and parietal interhemispheric asymmetries in schizophrenia at rest as well as right occipital hyperperfusion during WCST.

Effects of the NMDA antagonist ketamine on task-switching performance: evidence for specific impairments of executive control

In humans, the effects of subanesthetic doses of ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, substantially impair executive control functions. Here, we consider whether ketamine exposure can provide an animal model for the effects of ketamine on executive control. Two monkeys (Macaca mulatta) performed a cued task-switching paradigm. We studied their behavior before and after a range of ketamine doses. We found that ketamine slowed overall performance and decreased overall accuracy, strongly impaired the capacity to ignore task-irrelevant information and, to a lesser degree, decreased accuracy when a task switch was required. This pattern of results is very similar to that found in studies of schizophrenic patients performing task-switching paradigms or the Stroop task. We conclude that ketamine in monkeys provides a good animal model for exploring the relationship between the glutamate system, executive control, and the symptoms of schizophrenia.

Specificity of cognitive deficits in bipolar disorder versus schizophrenia. A systematic review

BACKGROUND

More and more epidemiological, genetic and neuroimaging studies show similarities between bipolar disorder (BD) and schizophrenia (SZ). Cognitive functions are known to be highly impaired in SZ and are increasingly studied in BD. When both populations are compared, the conclusions appear to be contradictory. The purpose of this review is to help define the profile of cognitive deficits in BD and in SZ.

METHODS

A systematic review of the literature of neuropsychological studies comparing BD and SZ was made, beginning in January 1990 and ending in January 2005. Thirty-eight studies met the required quality criteria and were included in this review.

RESULTS

Bipolar patients exhibit extensive cognitive abnormalities with a pattern of deficits that is not unique to this disease. However, when compared to schizophrenic patients, bipolar patients demonstrate a lesser degree of deficits, particularly concerning premorbid and current intelligence quotient and perhaps attention, verbal memory and executive functions. When looking into effect sizes, there seem to be different profiles even in studies finding no significant differences.

CONCLUSIONS

The neuropsychological differences reported between both groups could be due to the presence of psychotic features, to environmental factors (stressful events, duration of the disease and number of hospitalisations) and could also be related to differences during the neurodevelopmental phase. Further studies should confirm whether these results are truly related to different neurobiological backgrounds.

Performance on the Wisconsin Card Sorting Test in schizophrenia and genes of dopaminergic inactivation (COMT, DAT, NET)

The aim of the study was to test an association between polymorphisms of genes connected with dopaminergic inactivation in prefrontal cortex [catechol-O-methyltransferase (COMT), dopamine transporter (DAT), norepinephrine transporter (NET)], and performance on the Wisconsin Card Sorting Test (WCST), in schizophrenic patients. The number of perseverative errors (WCST-P), non-perseverative errors (WCST-NP), completed corrected categories (WCST-CC), conceptual level responses (WCST-%CONC) and set to the first category (WCST-1st CAT) were measured. Genotyping was done for the Val108(158)Met polymorphism of the COMT gene (79 patients), the 3'UTR VNTR polymorphism of the DAT gene (124 patients) and the 1287 A/G polymorphism of the NET gene (63 patients). Male schizophrenic patients with Val/Val genotype of COMT obtained better results on WCST-P, while female patients had worse results on the WCST-NP compared with the remaining genotypes. There was a slight trend for patients with the A9/A9 genotype of DAT and with the A/A genotype of NET to perform better on some domains of the WCST, compared with other genotypes. A limitation to the interpretation of results could be small number of patients studied as well as variable psychopathological state and medication during cognitive testing.

The Val66Met polymorphism of the brain-derived neurotrophic factor gene is associated with risk for psychosis: evidence from a family-based association study

Schizophrenia (SZ) is a prevalent and severe mental disorder. One of the most favored hypotheses for the etiology of SZ is the neurodevelopmental hypothesis. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin growth factor family, promotes the development, regeneration, and survival of neurons and has been linked to the neuropathology of SZ. The present study tested, in a sample of 94 nuclear families, the hypothesis that the BDNF gene Val66Met polymorphism is associated to SZ and its psychopathologic phenotype using a multidimensional symptom approach. Furthermore, considering a reported reduction of BDNF in the frontal cortex of patients with SZ, we studied the relationship between this polymorphism and prefrontal function. The transmission disequilibrium test (TDT) showed a preferential transmission of allele Val from heterozygous parents to the affected offspring (P = 0.002), suggesting a possible role of this gene in the vulnerability to SZ spectrum disorders. The findings remained essentially unchanged when the analysis was restricted to the subgroup of patients with SZ (P = 0.009) and when a multidimensional approach to the diagnosis was used. Quantitative transmission disequilibrium test (QTDT) analyses did not demonstrate a significant association between the prefrontal tests assessed (Wisconsin Card Sorting Test and Trail Making Test) and the transmission of the BDNF alleles. Our finding suggests that the investigated BDNF polymorphism plays an important role in the phenotype of psychosis, but not in the performance of tests of prefrontal cognitive functions analyzed in these patients.

Catechol-O-methyltransferase polymorphisms and some implications for cognitive therapeutics

Catechol-O-methyltransferase (COMT) is a gene involved in the degradation of dopamine and may both increase susceptibility to develop schizophrenia and affect neuronal functions involved in working memory. A common variant of the COMT gene (val(108/158)met) has been widely reported to affect pre-frontally mediated working memory function, with the high-activity val allele associated with poorest performance across a number of tests sensitive to updating and target detection. Pharmacological manipulations of COMT val(108/158)met also have reliably produced alterations in cognitive function, in line with an inverted U function of prefrontal dopamine signaling. Furthermore, there is accumulating evidence that COMT val(108/158)met genotype may influence the cognitive response to antipsychotic treatment in schizophrenia patients, with met allele load predicting the greatest improvement with medication. Recently, other single-nucleotide polymorphisms (SNPs) across the COMT gene have emerged as possible risk alleles for schizophrenia, although little is known about whether they affect prefrontal cognition in a manner similar to COMT val(108/158)met. Preliminary evidence suggests a modest role for a SNP in the 5' region of the gene on select tests of attention and target detection. Haplotype effects also may account for a modest percentage of the variance in test performance, and are an important area for future study.

Dimensional approaches to experimental psychopathology of schizophrenia: shift learning and report of psychotic-like experiences in college students

Adopting a dimensional approach to experimental psychopathology, and taking into account inconsistencies in the previous literature, we examined whether reports of psychotic-like experiences in undergraduate students were associated with shift-learning deficits, akin to those seen in schizophrenia. The participants (N=72) were tested on a new compound stimulus discrimination task before and after a target shift, and were administered a multi-dimensional schizotypy inventory (O-LIFE). Performance impairment following a target shift was associated with the negative (introvertive anhedonia) and the impulsive (impulsive non-conformity) dimension of schizotypy, but not with the positive (unusual experiences), nor the disorganised (cognitive disorganisation) dimension. None of the schizotypy measures were associated with performance on discrimination learning before the target shift. The obtained results are in line with past evidence that shift learning is associated with the severity of the negative symptomatology of schizophrenia. The possibility that psychotic-like features may contribute differentially to performance deficits across successive stages of learning is considered.

An association study of dopamine receptors polymorphisms and the Wisconsin Card Sorting Test in schizophrenia

Dopamine (DA), an important neurotransmitter in prefrontal cortex (PFC), is involved in the pathogenesis of schizophrenia. The aim of the study was to test an association between common polymorphism of genes for DA receptors DRD1, DRD2, DRD3, DRD4, and performance on the Wisconsin Card Sorting Test (WCST), measuring various functions of PFC, in 138 schizophrenic patients. Patients with G/G genotype of DRD1 tended to obtain worse results in all domains of WCST compared to patients with remaining genotypes, particularly for number of completed corrected categories, and trials to set the first category. A relationship was also found in female patients between DRD2 polymorphism and number of perseverative errors, while no association between WCST results and DRD3 or DRD4 polymorphism was observed in patients studied. The results may suggest an association between DRD1 gene polymorphism and performance on PFC test in schizophrenia. Also, the gender-dependent role of DRD2 in this process may be presumed.

Familial cognitive deficits in schizophrenia

Susceptibility to schizophrenia is considered familial, but the mechanism for transmission has not been found. Since widespread cognitive deficits have been found in patients with schizophrenia, several of these have been proposed as candidate familial endophenotypes that may or may not be predictive of who develops the illness. The current study examines these candidates in individuals from 32 families with at least 2 members having the diagnosis of chronic schizophrenia and normal comparison subjects using an extensive neuropsychological battery. Consistent with previous literature, family members with schizophrenia were significantly impaired on all measures compared with controls. Well relatives demonstrated significantly worse performance on a measure of verbal learning, delayed visual recall, perceptual-motor, and pure motor speed. Expressive and receptive language, but not other functions, were highly correlated within both concordant for schizophrenia and discordant sibling pairs, suggesting that they are familial vulnerability endophenotypes, but not predictive of whom becomes ill. On the other hand, some measures of perceptual-motor, pure motor speed, and frontal/executive functioning were significantly correlated in concordant, but not discordant pairs. These latter correlations suggest that some cognitive measures may be genetically related to the illness.

Do schizophrenia patients make more perseverative than non-perseverative errors on the Wisconsin Card Sorting Test? A meta-analytic study

The Wisconsin Card Sorting Test (WCST) is widely used to explore executive functions in patients with schizophrenia. Among other findings, a higher number of perseverative errors has been suggested to implicate a deficit in task switching and inhibitory functions in schizophrenia. Many studies of patients with schizophrenia have focused on perseverative errors as the primary performance index in the WCST. However, do schizophrenia patients characteristically make more perseverative than non-perseverative errors compared with healthy controls? We reviewed the literature where schizophrenia patients were engaged in the WCST irrespective of the primary goal of the study. The results showed that while both schizophrenia patients and healthy participants made more perseverative than non-perseverative errors, the contrast between perseverative and non-perseverative errors is higher in schizophrenia patients only at a marginal level of significance. This result suggests that schizophrenia patients do make a comparable number of non-perseverative errors and cautions against simplistic interpretation of poor performance of schizophrenia patients in WCST as entirely resulting from impairment in set-shifting or inhibitory functions.

Cognitive deficits in relatives of patients with schizophrenia: a meta-analysis

BACKGROUND

Schizophrenia is characterized by a generalized cognitive impairment with pronounced deficits in the domains of verbal memory, executive functioning and attention.

AIM

To investigate whether cognitive deficits found in patients with schizophrenia are also found in non-affected relatives.

METHOD

A meta-analytic review of the published literature on cognitive performance between relatives of schizophrenic patients and healthy controls.

RESULTS

The meta-analyses yielded nine weighted effect sizes from 37 studies comprising 1639 relatives of schizophrenia patients and 1380 control subjects. The largest differences were found on verbal memory recall (d=0.54, 95% CI=0.43-0.66) and executive functioning (d=0.51, 0.36-0.67). Attentional functioning showed smaller effect sizes (d=0.28, 0.06-0.50). These effect sizes are in the moderate range.

CONCLUSION

Cognitive deficits found in patients with schizophrenia are also found in non-affected relatives. This finding is consistent with the idea that certain cognitive deficiencies in relatives are caused by familial predisposition to schizophrenia and that these deficiencies might be putative endophenotypes for schizophrenia. However, our results do not address genetic causes directly. Further work is needed to determine whether certain cognitive traits are familial and whether there is co-inheritance of these traits with schizophrenia within families.

Deficit of executive functions in schizophrenia: relationship to neurological soft signs and psychopathology

Cognitive deficits and neurological soft signs (NSS) have frequently been reported in schizophrenic patients and they both appear related to prominent negative symptoms. The aim of the present study was to examine the relationship between deficit of executive functioning, assessed by the Wisconsin Card Sorting Test (WCST), NSS and psychopathological dimensions of schizophrenia in order to address the issue of whether a typology of schizophrenic patients may be identifiable by clinical, neurological and neuropsychological features. A sample of 26 male schizophrenic patients was divided, on the basis of the performance on the WCST, into two subgroups ('good performers' and 'poor performers') that were compared for the prevalence and severity of NSS, assessed by the Neurological Evaluation Scale (NES), and for the psychopathological features, assessed using the Positive and Negative Syndrome Scale (PANSS). To test for between-group differences, ANOVA was conducted. The 'poor performers' group showed greater severity of NSS: significant differences emerged for the NES total score and for the 'sequencing of complex motor acts' score. However, no significant differences between the groups emerged for any PANSS score. These findings seem to indicate that a common neurobiological abnormality could underlie cognitive deficits, especially concerning executive functioning, and subtle neurological abnormalities often present in schizophrenia, but they appear to deny that such dysfunctional correlates of schizophrenia are related to a prominent negative symptomatology.

Polymorphism of the brain-derived neurotrophic factor gene and performance on a cognitive prefrontal test in bipolar patients

OBJECTIVES

The aim of the study was to test a possible association between the Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene and performance on a neurocognitive test, the Wisconsin Card Sorting Test (WCST), in bipolar patients.

METHODS

Fifty-four bipolar patients were studied, 18 male and 36 female, aged 18-72 (mean 46 years). The number of perseverative errors (WCST-P), non-perseverative errors (WCST-NP), completed corrected categories (WCST-CC), conceptual level responses (WCST-%CONC) and set to the first category (WCST-1st CAT) were measured in relation to the Val66Met genotypes of BDNF.

RESULTS

The percentages of subjects with Val/Val, Val/Met and Met/Met genotypes were respectively 81.5, 16.7 and 1.8%. Subjects with Val/Val and Val/Met genotypes did not differ on clinical factors except for the age of onset of the illness, which was earlier in Val/Val than Val/Met genotype (27 years versus 38 years). The performance in all domains of WCST was significantly better in subjects with Val/Val BDNF genotype compared with Val/Met genotype.

CONCLUSIONS

The results suggest a role of BDNF in prefrontal cognitive function in bipolar illness. The tests of prefrontal cognition may be considered as endophenotypic markers in bipolar illness.

Cognitive dysfunctions in parents of schizophrenic patients parallel the deficits found in patients

Schizophrenia is characterized by a global cognitive impairment, with varying degrees of deficit in all ability domains. Since genetic factors are important in the etiology of schizophrenia we investigated whether parents of schizophrenic patients also show cognitive deficits, particularly on those cognitive ability domains that are most severely affected in patients. Both biological parents of 37 patients with schizophrenia (N=74 subjects) and 28 comparable healthy married control couples (N=56 subjects) were included. A comprehensive and standardized cognitive battery was used including tests measuring verbal memory, executive functioning, language, attention, and psychomotor functioning. Parents of patients differed from control couples on those cognitive constructs that are generally considered to be most impaired in schizophrenic patients, i.e. global verbal memory, bilateral motor skill, continuous performance, and word fluency. In addition, parents differed significantly from control couples on some other cognitive constructs on which patients show a smaller but also significant difference compared to healthy controls, i.e. unilateral motor skill and digit span. Results suggest that the cognitive constructs on which patients show relatively most severe impairment may prove suitable as endophenotypic markers in schizophrenia.

Wisconsin Card Sorting Test performance in schizophrenia: the role of working memory

Schizophrenia typically results in reduced performance on the Wisconsin Card Sorting Test (WCST). In the current study, we used a variety of approaches to examine the role of working memory (WM) in this deficit. One approach was to examine patterns of perseverative and non-perseverative errors. A second approach involved the comparison of the standard WCST to a modified version that used visual cues to reduce demands on WM. A third approach was to quantify the impact of WM demands on performance on a trial by trial basis. Consistent with theories of WM, the schizophrenia group showed increases in both perseverative and non-perseverative errors and differences between individuals with schizophrenia and controls were largest when WM demands were high. The visual cues helped the schizophrenia group overcome the high WM demands of the test, although they did not reduce the impairment in terms of standard scoring procedures. All impairments disappeared, however, after controlling for group differences on a measure of the speed of encoding information in WM. The pattern of results supports the conclusion that WM impairment contributes to poor performance on the WCST in individuals with schizophrenia, with additional evidence that this impairment results from generalized slowing of information processing.

Perseveration and over-switching in schizophrenia

Perseveration and switching in positive and negative schizophrenic patients are usually seen as manifestations of attention disorders. They may be closely related to each other, but have not been investigated in an integrated fashion. Such integrated investigation could contribute to the neurophysiological understanding of the relationship between the regional and the pharmacological deficit in schizophrenia. This study has developed a new tool-the Combined Attention Test (CAT)-for the simultaneous measuring of perseveration and switching. Forty-one unmedicated schizophrenic patients were tested. Using the Positive and Negative Sorting Scale (PANSS), subjects were classified into the two experimental groups: positive and negative schizophrenics. The control group consisted of 24 healthy subjects. Schizophrenic patients with positive symptoms tended to switch more than schizophrenic patients with negative symptoms and normal subjects; schizophrenic patients with negative symptoms tended to perseverate more than schizophrenic patients with positive symptoms and normal subjects. Over-switching is discussed as a specific symptom related to positive schizophrenia.

Wisconsin Card Sorting deficits in the offspring of schizophrenics in the New York High-Risk Project

It has been suggested that performance on the Wisconsin Card Sorting Test (WCST) may be an indicator of vulnerability to schizophrenia. WCST deficits have been demonstrated in schizophrenic patients and their relatives, but not as yet in their offspring. This study aimed to further establish the indicator potential of WCST deficits by analyzing data collected as part of the New York High-Risk Project (NYHRP), a longitudinal study of attention, cognition and clinical functioning in the offspring of schizophrenic (HRSz, n=73), affective disordered (HRAff, n=61) and normal comparison (NC, n=120) parents. Parental Research Diagnostic Criteria diagnoses were established by semi-structured interview (SADS-L). WCST testing was carried out when offspring were in their mid-20s. HRSz subjects performed significantly more poorly on the WCST than HRAff and NC subjects. High-risk subjects who developed psychotic symptoms prior to or shortly after testing did not differ significantly from HRSz subjects who did not become ill. Thus, WCST performance in the offspring of schizophrenics resembles that of schizophrenic patients and may distinguish HRSz from offspring at risk for nonschizophrenic illness. WCST deficits may be a specific familial indicator of vulnerability, but appear not to distinguish between those subjects at risk for schizophrenia who do or do not become ill.

Perseveration in schizophrenia: failure to generate a plan and relationship with the psychomotor poverty subsyndrome

Although perseveration in the Wisconsin Card Sorting Test (WCST) has been studied extensively in schizophrenia, the underlying cognitive dysfunctions are not yet clear. In schizophrenia, perseveration has been found to relate to frontal and striatal abnormalities. Therefore, both a failure to generate a plan as seen in patients with frontal abnormalities, or a failure to execute a plan as observed in Parkinson patients, who suffer primarily from striatal abnormalities, could explain perseveration in schizophrenia. The aim of the present study was to distinguish between these two cognitive dysfunctions, which are described by Frith in his routes-to-action model. The main difference between these dysfunctions is the ability to use external guidance. In the present study, 39 schizophrenic patients and 36 healthy controls were assessed with the California Verbal Learning Test (CVLT) and the WCST, in which use of external guidance can be measured, and with the Positive and Negative Syndrome Scale (PANSS) to determine the relationship with symptomatology. The results showed that half of the schizophrenic patients showed perseveration, which could be explained by a failure to generate a plan and was related to the psychomotor poverty subsyndrome. No evidence was found for a failure to execute a plan. Type of antipsychotic medication used (atypical vs. typical) proved not relevant. The results are discussed in the light of evidence for involvement of the dorsolateral prefrontal cortex in perseveration in schizophrenia.

Visual processing and neuropsychological function in schizophrenia and schizoaffective disorder

Persons with schizophrenia and schizoaffective disorder exhibit deficits in both visual processing and neuropsychological tasks. Little is known, however, about whether these deficits are related to one another. We administered psychophysical tests of visual discrimination and recognition, and neuropsychological tests of abstract flexibility, verbal learning, visual memory, working memory and attention to 42 outpatients with stable but chronic schizophrenia or schizoaffective disorder. Multiple regression analyses were performed to determine the relationship between these measures of neuropsychological function and visual psychophysical performance. Results indicated that motion perception was associated with working memory, and that the addition of a memory component to motion perception (motion recognition) was associated with both working memory and visual memory. Visual performance was not associated with symptom severity as measured by the PANSS. These results suggest that psychophysical tests of visual processing may contribute to deficits on neuropsychological tests of visual cognition, and may also reflect cross-modal disturbances of working memory function.

Eye movement and neuropsychological studies in first-degree relatives of schizophrenic patients

The aim of the study was to compare the results of oculomotor and neuropsychological tests in first-episode schizophrenic patients, in both their parents and matched healthy controls. Eye movement tests included fixation and a smooth pursuit task and neuropsychological tests which comprised the Trail Making Test (TMT) A and B, the Stroop Test A and B, and the Wisconsin Card Sorting Test (WCST). There was a significant difference between the 21 patients and their 33 healthy parents in the results of both the eye movement tests and the TMT and WCST but not in the Stroop test. On the other hand, a significant difference between parents and their matched control subjects was found in both oculomotor tests, in the Stroop B, and in two indices of the WCST (completed categories, CC and percentage of conceptual level responses, %CONC). A correlation was obtained between patients and their fathers in the intensity of smooth pursuit disturbances and two indices of the WCST (CC and %CONC), but not between patients and their mothers. The results obtained confirm those of other studies pointing to the presence of a significant impairment on oculomotor and neuropsychological tests in first-degree nonpsychotic relatives (parents) of schizophrenic patients, which may be used as an endophenotypic markers of genetic predisposition to schizophrenia.

Arithmetic fact retrieval and working memory in schizophrenia

Despite its importance in every-day life and vocational rehabilitation, arithmetic ability has rarely been investigated in schizophrenic patients. Those few studies reporting arithmetic deficits in schizophrenia, however, administered complex calculation tasks which drew not only on arithmetic abilities, but also on working memory resources known to be impaired in schizophrenia. In the present study, arithmetic abilities and working memory functions were investigated in schizophrenic patients (n=24) and healthy control subjects (n=24). Arithmetic fact retrieval was assessed in single-digit multiplication and corresponding division problems using a result verification task which minimized working memory demands. Problem size and the disparity of the proposed result were manipulated. The storage component of working memory was tested with a digit span forward task and the executive control component with a digit span backward as well as with verbal fluency tasks. Schizophrenic patients performed worse than controls only in the executive tasks. Digit span forward was preserved. In the arithmetic tasks, groups did not differ from each other, and a similar pattern of task manipulations was obtained. Hence, despite the executive control deficit retrieval of arithmetic facts is preserved in schizophrenia. Moreover, the same underlying cognitive processes as in control subjects are involved.

Executive/attentional cognitive functions in schizophrenic patients and their parents: a preliminary study

The aim of this study was to determine whether executive/attentional cognitive performances could be considered as markers of vulnerability to schizophrenia. The Stroop Color Word and fluency tests were significantly impaired in schizophrenic patients and their parents compared to controls matched on age and sex while performances on Nelson's Modified Card Sorting Test and the Trail Making Test did not differ. The impairments on the Stroop and fluency could be considered as endophenotypic markers of schizophrenia.

Prefrontal neurons and the genetics of schizophrenia

This article reviews prefrontal cortical biology as it relates to pathophysiology and genetic risk for schizophrenia. Studies of prefrontal neurocognition and functional neuroimaging of prefrontal information processing consistently reveal abnormalities in patients with schizophrenia. Abnormalities of prefrontal information processing also are found in unaffected individuals who are genetically at risk for schizophrenia, suggesting that genetic polymorphisms affecting prefrontal function may be susceptibility alleles for schizophrenia. One such candidate is a functional polymorphism in the catechol-o-methyl transferase (COMT) gene that markedly affects enzyme activity and that appears to uniquely impact prefrontal dopamine. The COMT genotype predicts performance on prefrontal executive cognition and working memory tasks. Functional magnetic resonance imaging confirms that COMT genotype affects prefrontal physiology during working memory. Family-based association studies have revealed excessive transmission to schizophrenic offspring of the allele (val) related to poorer prefrontal function. These various data provide convergent evidence that the COMT val allele increases risk for schizophrenia by virtue of its effect on dopamine-mediated prefrontal information processing-the first plausible mechanism for a genetic effect on normal human cognition and risk for mental illness.