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

Are personality traits associated with cognitive disturbance in psychosis?

OBJECTIVE

Personality and cognition are often considered as disparate constructs, both in normal individuals and in those with a psychosis. The goal of the present study was to analyze the relationship between dimensions of personality and cognitive performance in individuals with psychosis.

METHODS

Sixty-one consecutively admitted patients with an acute psychotic episode were recruited for this study. Personality was assessed through a semistructured interview with a close relative using the Personality Assessment Schedule. A wide neuropsychological battery was applied, including attentional, executive, memory tasks and global cognition. Assessments took place when symptomatology was in remission.

RESULTS

Higher scores on a passive-dependent dimension were significantly associated with poorer memory performance. Similarly, higher levels for a schizoid dimension were significantly associated with poorer executive performance. The results remained significant after partialling out the effect of gender, psychopathological dimensions and drug status.

CONCLUSION

It is hypothesized that personality traits and cognitive performance are interrelated domains in psychosis.

Relative risk for cognitive impairments in siblings of patients with schizophrenia

BACKGROUND

Patients with schizophrenia have impairments in several domains of cognition, including working memory/executive function, verbal memory, language, oculomotor scanning/psychomotor speed, and general intelligence. Impairments have also been found in unaffected siblings, suggesting they could be heritable. To assess the suitability of cognitive dysfunction for use in genetic studies, we estimated relative risk (lambda) in a large cohort of siblings.

METHODS

One hundred forty-seven patients with schizophrenia, 193 of their siblings, and 47 control subjects were studied using a neuropsychological test battery, which included intelligence quotient (IQ), Wide Range Achievement Test, Wisconsin Card Sort, Wechsler Memory Scale (revised), California Verbal List Test, Trails A and B, and Letter and Category Fluency. Relative risk was estimated using a cutoff score of 1 SD below the control mean.

RESULTS

As expected, patients performed markedly worse than control subjects on all tests except the Wide Range Achievement Test. Siblings had impaired performance on the Wisconsin Card Sort and Trails B, with trends for reduction (p = .01-.05) on the California Verbal List Test and Letter Fluency. Relative risk to siblings was elevated on the Trails B (lambda = 4.0) and California Verbal List Test (lambda = 2.8). Trends (p = .01-.05) for increased lambda were also seen for Wisconsin Card Sort, Letter Fluency, Wechsler Memory Scale and decline in IQ (lambda = 1.74-2.4). Correlations between tests of different cognitive functions were weak, indicating they measure relatively independent processes.

CONCLUSION

Unselected siblings of patients with schizophrenia have impairments in several cognitive domains. Relative risk scores were in the moderate range, suggesting a significant genetic component. Impairments on one test only weakly predicted impairments on other tests. Thus, cognitive phenotypes identify distinct, familial traits associated with schizophrenia. Using this dimensional approach to subdividing schizophrenia may reduce the clinical and genetic heterogeneity of schizophrenia and improve the power of genetic studies.

Educational level and age influence spatial working memory and Wisconsin Card Sorting Test performance differently: a controlled study in schizophrenic patients

The influence of educational level and age on executive function, as evaluated by the Wisconsin Card Sorting Test (WCST), and 'working memory,' as evaluated by means of a visual-manual delayed-response task, has been investigated in 25 schizophrenic patients and 35 healthy controls matched for age. Different patterns of correlations between educational level, age and cognitive variables were seen for the 'working memory' task but not for the WCST. No significant correlations between the WCST and the 'working memory' task indexes have been observed. Based on multivariate analyses, poor performance of schizophrenic patients on working memory and executive function tasks was observed; after covarying for the educational level, group differences were no longer significant for executive functions, but the difference in 'working memory' performance persisted. The implications of sociodemographic variables as well as the role of statistical manipulation are evaluated and their differential impact on 'working memory' and executive functions is proposed in further support of these neurocognitive constructs that may be dissociable.

Neuropsychological performance and spectrum personality traits in the relatives of patients with schizophrenia and affective psychosis

Neuropsychological deficits are found in both schizophrenic patients and their relatives, and some studies have shown similar, but less severe, deficits in affective psychotic patients and their relatives. We set out to establish: (a) whether schizophrenia spectrum personality traits are more common in the relatives of schizophrenic patients than, in the relatives of affective psychotic patients; and (b) what the relation is between spectrum personality traits and neuropsychological deficits in these relatives. Relatives were interviewed using the International Personality Disorder Examination (IPDE), and also completed the National Adult Reading Test (NART), the Trail Making Test (TMT; Parts A and B) and Thurstone's Verbal Fluency Test (TVFT). Spectrum personality traits were equally common in 129 relatives of schizophrenic patients and 106 relatives of affective psychotic patients, but the performance of the former group was inferior to that of the latter on the NART and the TVFT. Relatives with high paranoid traits had lower NART scores than relatives without such personality traits; similarly, those with high schizoid traits took longer to complete the TMT, part B, than those without such traits; and relatives with high schizotypal traits generated significantly fewer words on the TVFT than those without such traits. We conclude that relatives of schizophrenic and affective psychotic patients share a propensity to schizophrenia spectrum traits, but relatives of the former have poorer neuropsychological performance. Furthermore, there exists an association between neuropsychological deficits and spectrum traits in both groups of relatives; in particular those with high paranoid traits have lower IQ scores than their less paranoid counterparts.

Relationship between symptom dimensions and neurocognitive functioning in schizophrenia: a meta-analysis of WCST and CPT studies. Wisconsin Card Sorting Test. Continuous Performance Test

Cognitive deficits have been hypothesized to be differentially related to the negative, positive and disorganization dimensions of schizophrenia symptoms. In this article, we quantitatively review the published literature on the relationships between symptom dimensions in schizophrenia and performance on the two most widely applied tests of executive functioning and sustained attention, the Wisconsin Card Sorting Test (WCST) and the Continuous Performance Test (CPT). Meta-analyses were conducted on studies that reported correlational data for the relations between performance on these tests and scales of positive and negative symptoms. The more recent distinction between disorganization and reality distortion was also taken into account. The results showed statistically significant relationships of negative symptoms with worse performance on the WCST and the CPT. Disorganization symptoms showed a significant positive correlation with perseverations on the WCST, but not with CPT performance. In contrast, reality distortion symptoms and general scores for all positive symptoms did not correlate with either measure. Although some correlations were statistically significant, the observed associations between psychiatric symptoms and cognitive performance were typically weak, suggesting relative independence of these disease processes.

Soft neurological signs in schizophrenic patients and their nonpsychotic siblings

This study examined neurological signs as familial vulnerability factors to schizophrenia. Fifteen Chinese schizophrenic patients, 21 of their nonpsychotic siblings, and 26 healthy volunteers, matched for age, sex, and education, were assessed by using the Cambridge Neurological Inventory. Results showed that patients and their siblings had significantly higher global neurological impairment than controls. The severity of motor coordination impairment of the siblings was in between patients and controls. This may suggest either patients have higher genetic vulnerability for the neurological abnormality and schizophrenia than their nonpsychotic siblings or the disease can further worsen the preexisting neurological deficit. Disinhibition signs were similar in patients and siblings, but significantly less in controls indicating its familial nature. Extrapyramidal and sensory integration signs were similar in siblings and controls, but significantly more severe in patients, suggesting nonfamilial abnormalities. In conclusion, these findings may imply different etiological origins for different subgroups of neurological signs.

Psychopathology and wisconsin card sorting test performance in young unmedicated schizophrenic patients

The relationship between psychopathology and Wisconsin Card Sorting Test (WCST) performance was evaluated in 25 unmedicated young acute schizophrenic female patients (14 neuroleptic-naive and 11 neuroleptic-free) and 15 female controls. The schizophrenic patients (especially the neuroleptic-free) performed more poorly than controls in the WCST. In addition, WCST impairment correlated with both negative and positive symptoms. The results suggest that the neuropsychological dysfunction in schizophrenia is present at the onset of the illness, and is neither secondary to previous neuroleptic treatment nor to chronicity of the illness.

Executive control is disturbed in schizophrenia: evidence from event-related potentials in a Go/NoGo task

BACKGROUND

Schizophrenic patients suffer from cognitive and attentional deficits, particularly from failure of executive control functions.

METHODS

This study investigated the cortical organization of executive control in schizophrenic patients and healthy control subjects using event-related potentials (ERPs). Event-related potentials were collected while subjects performed an auditory Go/NoGo task that required response inhibition. To exclude stimulus discriminability and early stimulus processing to confound results, stimuli were adjusted to the subject's individual discrimination ability and were presented in a simple and a difficult version.

RESULTS

Schizophrenic patients performed similar to control subjects in the Go condition but worse than control subjects in the NoGo condition that required response inhibition. Event-related potentials revealed the neurophysiological substrate of this dysfunction. In the Go conditions, both healthy control subjects and schizophrenic patients showed the same voltage pattern. In the NoGo condition, control subjects and patients showed similar cortical activation only during early processing (N2 time window). However, in later stages of processing (P3 time window), healthy subjects showed left lateralization of ERPs over frontal areas while schizophrenic patients did not.

CONCLUSIONS

We conclude that schizophrenic patients exhibit deficient processing in a neuronal network, including left frontal areas, that is involved in later stages of executive control function.

Cognitive deficits and cognitive training in schizophrenic patients: a review

OBJECTIVE

The aim of this paper is to review the current status of knowledge of cognitive deficits and remediation in patients with schizophrenia.

METHOD

Relevant reports were identified by a literature survey. In addition, some outstanding researchers in these areas were asked to add to the identified list relevant literature that was not included.

RESULTS

Our review focuses on the cognitive deficits observed in the areas of attention, memory and executive functions. We attempt to classify dysfunctions as vulnerability- or symptom-linked factors, and we discuss the methodological question of a general performance deficit vs. a differential deficit. Furthermore, we briefly delineate how antipsychotics affect cognitive functions. Finally, controlled studies of cognitive training are discussed in more detail.

CONCLUSION

The most outstanding cognitive dysfunctions in patients with schizophrenia can be related to the areas of attention, memory and executive functions. Interest in cognitive remediation has to some extent been rekindled in the 1990s. However, few studies on the effects of cognitive training programs have been conducted.

Differentielle Aspekte kognitiver Remediation bei schizophren Erkrankten auf der Grundlage des Wisconsin Card Sorting Tests

Zusammenfassung. Ziel der Studie ist der Nachweis interindividuell unterschiedlicher Responsivität schizophrener Patienten bei einer Maßnahme der kognitiven Remediation sowie die diagnostische Nutzung dieser Information. Theoretischer Rahmen ist das Konzept des Dynamischen Testens. 56 schizophrene Patienten erhielten den Wisconsin Card Sorting Test (WCST) zunächst unter Standardbedingung, dann mit spezifischen Instruktionen und Rückmeldungen und dann wieder unter Standardbedingung. Aufgrund des Leistungsverlaufs ließen sich 21 “durchgehend Leistungsstarke”, 22 “Lerner” und 13 “Nichtlerner” unterscheiden. In einer Generalisierbarkeitsstudie mit einer Teilstichprobe zeigte sich, daß der WCST-Lernstatus der Patienten auf das verbale Reproduktionsgedächtnis (Auditiv-Verbaler Lerntest) generalisierbar ist, wenn dessen Prüfung mit spezifischen Lernanforderungen verbunden wird. Die Ergebnisse werden hinsichtlich ihrer diagnostischen Implikationen und ihres Beitrags zur Schizophrenietheorie diskutiert.

Cognitive functions in schizotypal personality disorder

OBJECTIVE

Schizophrenia spectrum subjects have cognitive deficits in a variety of domains. Schizotypal personality disordered (SPD) subjects do not have many of the confounds seen in schizophrenic patients, but may have the same pattern of cognitive deficits in attention and executive functioning.

HYPOTHESIS

We hypothesized that SPD subjects would have impairments on measures of attention, abstract reasoning, cognitive inhibition, working memory and verbal recognition memory when compared to normal subjects, and that these deficits would be intermediate to those observed in schizophrenic patients.

METHOD

SPD subjects (N=20) were compared to age-, gender- and education-matched schizophrenic patients (N=20) and normal comparison subjects (N=20) on a battery of cognitive measures.

RESULTS

The data were analyzed using standard statistical methods, including effect sizes. Using a conservative alpha level of 0.01, schizophrenic patients had deficits on many of these measures compared to normal subjects. Although the SPD subjects did not significantly differ from normal comparison subjects at the p < 0.01 level, there were trends (p < 0.019-0.028) toward impairment on measures of working memory and general intellectual functioning. On further effect size analyses, SPD subjects performed intermediate to normals and schizophrenic patients on measures of attention, abstract reasoning, cognitive inhibition, verbal working memory, recognition memory, and general intellectual functioning, with moderate to large effect sizes separating groups.

CONCLUSIONS

These results suggest that SPD subjects have possible widespread cognitive deficits that are of lesser magnitude than those observed in schizophrenic patients.

Hippocampal N-acetyl aspartate in unaffected siblings of patients with schizophrenia: a possible intermediate neurobiological phenotype

BACKGROUND

Shared neurobiological characteristics of patients with schizophrenia and their siblings may represent "intermediate phenotypes" that may more closely reflect the genetic susceptibility underlying this illness. We sought evidence of such phenotypes using magnetic resonance spectroscopy based on previously described regional abnormalities in levels of the neuronal marker N-acetyl-aspartate (NAA) in the hippocampal area and dorsolateral prefrontal cortex of patients with schizophrenia.

METHODS

We studied 47 schizophrenics, 60 unaffected siblings, and 66 healthy control subjects with long echo time multislice proton magnetic resonance spectroscopic imaging, primarily measuring NAA, creatine plus phosphocreatine (CRE), and choline-containing compounds.

RESULTS

Both patients and their unaffected siblings had significant reductions in hippocampal area NAA/CRE as compared with control subjects. As exploratory analyses, estimates of heritability were performed. Although quantitative correlation of hippocampal NAA between patients and sibs was low (likely reflecting measurement noise), qualitatively defined "low hippocampal NAA/CRE phenotypes" yielded relative risk estimates (lambda s) of between 3.8 and 8.8, suggesting this characteristic is heritable.

CONCLUSIONS

Our finding adds to the evidence that hippocampal abnormalities are associated with schizophrenia and may represent a novel biological phenotype for genetic studies of schizophrenia.

Executive-frontal lobe cognitive dysfunction in schizophrenia: a symptom subtype analysis

Impairment of executive-frontal lobe functioning, affecting the planning, initiation and regulation of goal-directed behavior, is a common cognitive deficit in schizophrenia. However, it is unclear if deficits in these frontal-lobe-mediated abilities are differentially expressed across clinical subgroups. We analyzed executive-frontal abilities in relation to symptom expression in 53 hospitalized schizophrenic patients. Patients were assigned to one of three subgroups based on rank order analysis of Brief Psychiatric Rating Scale factors: Withdrawal-Retardation, Reality Distortion and Conceptual Disorganization. Executive-frontal tests included Visual Search, Verbal Fluency, Verbal Series Attention, Trail Making - Part B, Symbol Digit, Hopkins Verbal Learning, Digit Span, Wisconsin Card Sorting, Stroop Color-Word and Attentional Capacity. The schizophrenia group showed significant deficits relative to healthy control subjects (n = 20) on all tests. Exploratory factor analysis of test scores revealed three factors: (i) Verbal Processing/Memory; (ii) Cognitive Flexibility/Attention; and (iii) Psychomotor Speed/Visual Scanning. The three symptom subgroups were differentially impaired on executive-frontal abilities: Withdrawal-Retardation on psychomotor speed, verbal fluency, working memory, visual search and cognitive flexibility; Conceptual Disorganization on attention; Reality Distortion on verbal memory. The results have implications for syndrome definition, pharmacological intervention and prediction of outcome in schizophrenia.

Relations between neuropsychological vulnerability markers and negative symptoms in schizophrenia

In neuropsychological vulnerability research the visual backward masking task, the Span of Apprehension, the degraded stimulus Continuous Performance Test (dsCPT), and the Wisconsin Card Sorting Test have been described as putative indicators for the predisposition to develop negative (schizophrenic) symptoms. The present study assesses the stability of the association between neuropsychological tests and negative symptoms by examining clinically improved patients. The interdependence between the four cognitive measures and clinical symptomatology was examined in 31 patients with DSM III-R and ICD-10 schizophrenia suffering predominantly from negative symptoms. Backward masking performance was related to affective flattening and anxiety-depression. False alarm rate on dsCPT was associated positively with affective flattening and hallucinations, and negatively with avolition. Card sorting preseverative errors correlated negatively with anhedonia, non-preservative errors correlated positively with avolition. Correlations notwithstanding, the data provide evidence in support of the relative independence of neuropsychological functions and negative symptoms in clinically improved schizophrenics.

Executive functioning deficits in hypothetically psychosis-prone college students

Executive functioning deficits have been identified in schizophrenics, their family members, in persons with schizophrenic spectrum disorders, and in others psychometrically at high risk for future psychosis. In the present study, a group hypothesized to be at high risk for future psychosis (Chapman and Chapman, 1985; Chapman et al., 1994) showed no generalized cognitive deficit, but demonstrated impairments on two executive functioning measures (Wisconsin Card Sorting Test and Stroop Color and Word Test) as compared to control students. Results suggest that executive function deficits, particularly impaired inhibitory control, appear in individuals who may be at risk of later decompensation into a psychotic state, and thus may be important in the pathogenesis of schizophrenia and schizophrenic spectrum disorders.

Neuropsychological deficits in probands from multiply-affected schizophrenic families

This study was designed to determine if schizophrenics from families with more than one psychotic relative show more severe neuropsychological deficits than schizophrenics with only one psychotic relative, non-familial schizophrenics, and a group of matched normal controls. Eighty-one schizophrenic-spectrum patients were divided into three groups on the basis of the presence of psychotic disorder among first- and second-degree relatives. The three groups of schizophrenics and the normal controls were compared for differences on a brief neuropsychological testing battery. The four groups showed significant multivariate differences. Patients from multiply-affected families showed significantly greater neuropsychological dysfunction on measures of abstract concept formation, visuomotor-coordination, and attention than patients from families that had only one psychotic relative. Schizophrenics from low-density families showed more severe deficits in fine motor-control than non-familial schizophrenics. These data suggest that abnormalities in those frontal systems that are likely to mediate fine motor control and abstract concept formation may be related to the degree of familial loading for psychotic disorder.

No deficit in Wisconsin Card Sorting Test performance of schizophrenic patients' first-degree relatives

The Wisconsin Card Sorting Test (WCST) was administered to 92 schizophrenic patients, 25 first-degree relatives and 60 normal subjects in order to investigate whether this task could be considered a trait marker of vulnerability to schizophrenia. The schizophrenic patients performed significantly worse than either their relatives or normal subjects, but unaffected relatives did not differ from controls. Our results suggest that WCST performance is more likely a feature inherent to the disease process rather than an index of the genetic susceptibility to the illness.

Non-selective impairment of Wisconsin Card Sorting Test performance in patients with schizophrenia

Sixty-two schizophrenic patients and 26 healthy volunteers were administered the Wisconsin Card Sorting Test (WCST) a task putatively specific for frontal functions and the Wechsler Adult Intelligence Scale (WAIS). The purpose of this study was to evaluate the presence of specific frontal lobe deficits in the course of schizophrenia and the capacity of these tasks to discriminate between patients and controls. Schizophrenic patients showed a poorer performance than control subjects in both tests. No evidence emerged to support a higher discriminant power for the WCST in identifying schizophrenic subjects from healthy controls compared with the WAIS. Our data suggest that the deficit in WCST performance is not selective, but rather part of a more generalized neuropsychological impairment in schizophrenic patients.

Stability in cognitive dysfunctions in schizophrenic patients

The purpose of the present study was to classify cognitive dysfunctions in schizophrenic subjects according to a trait/state model. A sample of 15 patients was examined on 10 different cognitive measures in two distinctly different phases: an acute psychotic state and partial remission. To determine the degree of dysfunction at the two stages of illness, the schizophrenic patients were also compared to 14 non-psychiatric controls. Six of the 10 measures examined can be classified as cognitive deficits in schizophrenics. Four measures are possibly trait-dependent components: two backward masking scores and two long-term memory measures. A short-term memory measure is the only one that can be classified as an episode-linked factor. The other cognitive deficits found can be characterized as mediating vulnerability factors, i.e. they are more prominent in the acute psychotic state, but do not completely disappear during remission states.

Neuropsychological, olfactory, and hygiene deficits in men with negative symptom schizophrenia

Associations between symptom subtypes, life skills, olfactory identification, and neuropsychological ability were investigated in patients with schizophrenia and related to observations of poor personal hygiene and implied functional compromise of orbitofrontal integrity. Twenty-seven men with chronic schizophrenia were assessed using the Positive and Negative Syndrome Scale for Schizophrenia and the Life Skills Profile. Performance on the University of Pennsylvania Smell Identification Test (UPSIT), the Modified Wisconsin Card Sorting Test (MWCST), delayed response/alternation, and memory tasks derived from the Wechsler Memory Scale-Revised (WMS-R) was also compared to that of an age-, sex-, and IQ-matched control group. Patient UPSIT, MWCST, and WMS-R performance was significantly impaired in comparison to controls. Poor UPSIT performance and poor self-care were significantly associated with negative symptoms. Also, UPSIT ability was associated with performance on the MWCST in both patients and controls, whereas an association with performance on the WMS-R was only found in normal subjects rather than in the patients with schizophrenia. The importance of these findings to postulated mechanisms involving prefrontal rather than mediotemporal lobe (MTL) function in schizophrenia are discussed, as is the relevance of the use of smell identification ability to subtype identification and rehabilitative strategies.

Functional lateralization of the prefrontal cortex during traditional frontal lobe tasks

We attempted to identify brain regions functionally lateralized during cognitive tasks traditionally linked to the prefrontal cortex (PFC) by measuring regional cerebral blood flow with H2(15)O positron emission tomography (PET). Fourteen normal subjects were scanned six times while performing six different cognitive conditions comprising three task paradigms putatively sensitive to PFC integrity: the Wisconsin Card Sort (WCS), Delayed Response Alternation (DA), and the Spatial Delayed Response (SDR) Tasks, and three matched sensorimotor control tasks. Multivariate and repeated measures analyses indicated that for all three cognitive paradigms there were no significant hemisphere, hemisphere-by-condition, or hemisphere-by-region effects. However, with more liberal statistical comparison (paired t tests), the superior frontal gyrus showed lateralization during both the WCS and SDR tasks (both R > L). These results suggest that, although some asymmetries may be found using liberal analyses, there is less evidence of lateralized brain function during performance of these tasks of PFC function, than in language and motor systems. Implications for testing PFC function in neuropsychiatric groups are discussed.

A preliminary study of the neuropsychological heterogeneity of familial schizophrenia

This exploratory study describes the heterogeneity of the neuropsychological deficits that characterize familial schizophrenia. Forty-six familial schizophrenics showed significantly more variability in abstraction and problem-solving and motor control than 39 non-familial schizophrenics. Cluster analyses of these two neuropsychological parameters indicate that while the non-familial schizophrenics fall into one homogeneous cluster, the familial schizophrenics fall into three relatively distinct clusters which differ significantly in their morbid risk for schizophrenic-spectrum disorder. These preliminary data suggest that frontal lobe deficits are associated with an increased familial risk for schizophrenia.

Genetic risk of neuropsychological impairment in schizophrenia: a study of monozygotic twins discordant and concordant for the disorder

We used a paradigm involving monozygotic (MZ) twin pairs discordant for schizophrenia (n = 20) and concordant for schizophrenia (n = 8), as well as normal MZ twin pairs (n = 7) in order to study cognitive measures of genetic risk in schizophrenia. A comparison between the unaffected twins from the discordant sample and the normal twins indicated subtle attenuations in some aspects of memory and executive functioning in the unaffected group and thus provided evidence for cognitive markers of a genetic component in schizophrenia. A comparison of the affected twins from the discordant pairs and the concordant twins yielded virtually no differences, suggesting that a distinction between familial and sporadic cases is not valid in this sample. Large differences between unaffected and affected members of discordant pairs on a wide variety of variables, including IQ, attention, memory, and executive function, highlighted the magnitude of disease-specific factors.

Electrical brain activity in schizophrenia described by equivalent dipoles of FFT-data

Since results of conventional FFT-power-analysis are reference-dependent, only unambiguous neurophysiological data should be used for a functional physiological interpretation of EEG-data. FFT-approximation with successive center-of-gravity-dipole calculation gives unambiguous EEG-data with regard to recording reference. In the present investigation 22 medicated schizophrenic patients were compared with 22 healthy age- and sex-matched controls with regard to spontaneous resting EEG. More anterior and superficial equivalent-dipoles were found in the beta-bands for schizophrenic patients compared to healthy control subjects. There was a tendency of increased beta-activity in schizophrenic subjects. With more severe schizophrenic symptoms (higher BPRS-score), the more anterior was the equivalent-dipole localization in the beta 1-band, and the deeper in the theta-band. The different locations of the beta-band dipoles in schizophrenic patients suggest that different neuronal populations generate beta-activity in schizophrenia compared to healthy controls. FFT-approximation allows a substantial and meaningful data reduction in multichannel recordings and will hopefully help in understanding pathological brain functions in schizophrenia.

An assessment of the Wisconsin Card Sorting Test as an indicator of liability to schizophrenia

In order to test the hypothesis that a poor performance in the Wisconsin test (WCST) may be an indicator of liability to schizophrenia, we compared the WCST performances of patients with DSM III-R schizophrenia, normal controls, and patients with schizotypal personality disorder (SZT PD). While schizophrenic patients performed significantly worse than subjects in the other two groups, schizotypal and normal subjects showed no significant differences in the WCST execution. Moreover, patients with SZT PD with or without positive family history for the schizophrenic spectrum had similar WCST performances. Our observations are in keeping with other studies employing the WCST in paradigms of heightened liability to schizophrenia, and suggest that a poor performance in the test is more probably a feature of the disease process, than a trait marker of vulnerability to the illness demonstrable in high-risk subjects.

Patterns of neuropsychological deficit in cases of schizophrenia spectrum disorder with and without a family history of psychosis

This study was designed to identify the types of neuropsychological deficits that are unique to familial and nonfamilial forms of schizophrenia. Seventy-two patients who met Research Diagnostic Criteria for schizophrenia or schizoaffective disorder, mainly schizophrenic, were divided into two groups on the basis of the presence or absence of a family history of psychosis. The two groups were then compared for differences on six neuropsychological parameters as well as for differences in psychotic symptoms. Multivariate analyses indicated that schizophrenic patients with a family history of psychosis showed significantly higher levels of overall neuropsychological deficit and significantly greater deficits on tests of motor-control and abstraction and problem-solving. Factor analyses indicate that schizophrenic patients with a family history of psychosis show a pattern of specific neuropsychological deficits, while schizophrenic patients without a family history show a pattern of more consistent cognitive deficits. The results of this study indicate that recent-onset schizophrenic patients with and without a family history of psychosis show distinctly different patterns of neuropsychological dysfunction. These data suggest that abnormalities in the dorsolateral prefrontal cortex and nonprimary motor areas may be associated with an increased familial risk for psychotic disorder.

Unawareness of illness and neuropsychological performance in chronic schizophrenia

This research attempts to explore empirically the relationship between lack of awareness of illness and neuropsychological performance in a group of chronic schizophrenic subjects. Thirty one chronic schizophrenics were administered the recently developed Scale to Assess Unawareness of Mental Disorder (SUMD) and 3 neuropsychological tests that have demonstrated ability to assess frontal lobe performance: the Wisconsin Card Sorting Test (WCST, Verbal Fluency Test and Trials A and B. The number of categories completed and the percent perseverative responses on the WCST were found to significantly correlate with lack of illness awareness as measured by the SUMD. These two WCST variables were also able to significantly discriminate between subjects of high versus low awareness. A discriminant function analysis found that a linear combination of WCST percent perseverative responses and symptom severity could successfully categorize 84% of the aware versus unaware subjects. These results are taken to support the hypothesis that at least in some of its manifestations lack of awareness among chronic schizophrenics has an organic etiology probably mediated by the frontal lobes.

Cognitive functioning and anhedonia in subjects at risk for schizophrenia

This study investigated the performance of individuals with familiar loading of schizophrenia (healthy siblings of schizophrenic inpatients) on three neuropsychological tasks assumed to require frontal lobe functions: Trail Making Test (TMT), verbal fluency and Wisconsin Card Sorting Test (WCST). Healthy siblings of schizophrenics differed in performance from healthy controls not only on the WCST, but also on the Trail Making Test and the verbal fluency task. Furthermore, scores of physical anhedonia, assessed in a self-report rating scale (Chapman et al., 1976) were also significantly higher in the high risk group than in the control sample. However, healthy siblings of schizophrenics did not differ from controls with regard to experiences of perceptual aberrations, measured by the same method (Chapman et al., 1978). Neuropsychological performance and elevated anhedonia scores in the high risk group were interpreted under the conceptual framework of vulnerability markers: they were supposed to represent a trait shared by family members of schizophrenic probands. Amongst the neuropsychological tests, there were significant correlations between the physical anhedonia score and WCST and Trail Making test performance in the group of healthy siblings of schizophrenics, but not in the control group.

Neuropsychological indicators of the vulnerability to schizophrenia

Schizophrenia is associated with enduring deficits in neuropsychological functioning. It is widely undecided if the various aspects of neuropsychological impairment are a consequence of the disorder or if they are also present premorbidly and in populations at increased risk for schizophrenia (vulnerability markers). Neuropsychological deficits in healthy relatives of schizophrenic patients who are at an elevated risk for schizophrenia and who did not yet pass the period of risk would indicate that these deficits are vulnerability markers. This hypothesis was tested for three neuropsychological paradigms which have been proven to distinguish schizophrenic patients from controls. 33 siblings of drug-free schizophrenic probands revealed deficits has compared to 33 matched healthy controls in a blurred single target version of the Continuous Performance Test and in a multiple item version of the Span of Apprehension Test but not so in less difficult versions of both tests or in the time needed to react to stimuli with shifting modality.