Intelligence quotient and neuropsychological profiles in patients with schizophrenia and in normal volunteers

Navigating the semantic space: Unraveling the structure of meaning in psychosis using different computational language models

Speech in psychosis has long been ascribed as involving 'loosening of associations'. We pursued the aim to elucidate its underlying cognitive mechanisms by analysing picture descriptions from 94 subjects (29 healthy controls, 18 participants at clinical high risk, 29 with first-episode psychosis, and 18 with chronic schizophrenia), using five language models with different computational architectures: FastText, which represents meaning non-contextually/statically; BERT, which represents contextual meaning sensitive to grammar and context; Infersent and SBERT, which provide sentential representations; and CLIP, which evaluates speech relative to a visual stimulus. These models were used to quantify semantic distances crossed between successive tokens/sentences, and semantic perplexity indicating unexpectedness in continuations. Results showed that, among patients, semantic similarity increased when measured with FastText, Infersent, and SBERT, while it decreased with CLIP and BERT. Higher perplexity was observed in first-episode psychosis. Static semantic measures were associated with clinically measured impoverishment of thought and referential semantic measures with disorganization. These patterns indicate a shrinking conceptual semantic space as represented by static language models, which co-occurs with a widening in the referential semantic space as represented by contextual models. This duality underlines the need to separate these two forms of meaning for understanding mechanisms involved in semantic change in psychosis.

Characterising Demographic, Clinical and Functional Features of Cognitive Subgroups in Schizophrenia Spectrum Disorders: A Systematic Review

Considerable cognitive heterogeneity is present within the schizophrenia spectrum disorder (SSD) population. Several subgroups characterised by more homogenous cognitive profiles have been identified. It is not yet clear however, whether these subgroups represent different points along a continuum of cognitive symptom severity, or whether they reflect unique profiles of the disorder. One way to determine this is by comparing subgroups on their non-cognitive characteristics. The aim of the present review was to systematically summarise our current understanding of the non-cognitive features of the cognitive subgroups of schizophrenia spectrum disorder (SSD). Thirty-five relevant studies were identified from January 1980 to March 2020. Cognitive subgroups were consistently compared on age, sex, education, age of illness onset, illness duration, positive, negative and disorganised symptoms, depression and psychosocial functioning. It was revealed that subgroups were consistently distinguished by education, negative symptom severity and degree of functional impairment; with subgroups characterised by worse cognitive functioning performing/rated worse on these characteristics. The lack of consistent subgroup differences for the majority of the non-cognitive characteristics provides partial support for the notion that cognitive subgrouping in SSD is not simply reflecting a rehash of previously identified clinical subtypes. However, as subgroups were consistently distinguished by three characteristics known to be associated with cognition, our understanding of the extent to which the cognitive subgrouping approach is representing separate subtypes versus subdivisions along a continuum of symptom severity is still not definitive.

Characterising the structure of cognitive heterogeneity in schizophrenia spectrum disorders. A systematic review and narrative synthesis

The aim of the present review was to systematically summarise our current understanding of the structure of the cognitive heterogeneity that exists within schizophrenia spectrum disorder (SSD). Fifty-two relevant studies were identified from January 1980 to March 2019 that investigated cognitive subgroups within SSD. Twenty-five studies employed classification criteria based on current neuropsychological function, 14 studies employed various data-driven subgrouping methodologies and 13 studies investigated putative cognitive symptom trajectories. Despite considerable methodological variability, three distinct cognitive subgroups reliability emerged; a relatively intact cognitive subgroup characterised by high cognitive performance, an intermediate cognitive subgroup defined by mixed or moderate levels of cognitive function/dysfunction and a globally impaired subgroup characterised by severe cognitive deficits. Whilst preliminary evidence suggests that these subgroups may have further investigative relevance in and of themselves, additional research is required and discussed. A set of reporting guidelines are also presented to overcome the methodological inconsistencies identified in the reviewed literature.

Cortical structures and their clinical correlates in antipsychotic-naïve schizophrenia patients before and after 6 weeks of dopamine D2/3 receptor antagonist treatment

BACKGROUND

Schizophrenia has been associated with changes in both cortical thickness and surface area, but antipsychotic exposure, illness progression and substance use may confound observations. In antipsychotic-naïve schizophrenia patients, we investigated cortical thickness and surface area as well as mean curvature before and after monotherapy with amisulpride, a relatively selective dopamine D2/3 receptor antagonist.

METHODS

Fifty-six patients and 59 matched healthy controls (HCs) underwent T1-weighted 3T magnetic resonance imaging. Forty-one patients and 51 HCs were re-scanned. FreeSurfer-processed baseline, follow-up values and symmetrized percentage changes (SPC) in cortical structures were analysed using univariate analysis of variance. Clinical measures comprised psychopathology ratings, assessment of functioning and tests of premorbid and current intelligence. We applied false discovery rate correction to account for multiple comparisons.

RESULTS

At baseline, groups did not differ in cortical thickness or surface area; however, curvature in the left hemisphere was higher in patients (p = 0.015). In both patients and HCs, higher curvature was associated with lower premorbid (p = 0.009) and current intelligence (p 0.43). Cortical thickness SPC was negatively associated with symptom improvement (p = 0.002).

CONCLUSIONS

Schizophrenia appears associated with subtle, yet clinically relevant aberrations in cortical structures. Mean curvature holds promise as a sensitive supplement to cortical thickness and surface area to detect complex structural brain abnormalities.

Premorbid IQ subgroups in first episode non affective psychosis patients: Long-term sex differences in function and neurocognition

BACKGROUND

Low IQ has been associated with schizophrenia, even to the point of being posited as a possible causal factor for psychosis. However, individuals with normal and high IQ also develop psychotic illnesses. The aim of this study was to characterize premorbid IQ subgroups at first episode of psychosis (FEP).

METHODS

The study sample comes from a large epidemiological, 3-year longitudinal, intervention program on psychosis containing individuals living in a catchment area in Spain. Estimated premorbid IQ (epIQ) scores were used to build low (<90), normal (90-110) and high (>110) epIQ subgroups in samples of FEP patients (N=292) and healthy controls (N=199). The epIQ subgroups were compared in sociodemographic, neuropsychological, clinical and premorbid characteristics. Long-term functional and cognitive outcome, with a focus on sex differences, were also explored.

RESULTS

Low-epIQ was more frequently found in FEP patients (28.8%) than in healthy controls (14.6%). Low-epIQ patients were more likely to have worse premorbid adjustment, belong to low socioeconomic status families, have less years of education, and to be single, unemployed, and younger. They presented more severe impairments in processing speed, executive and global cognitive function. Female patients with low-epIQ showed better baseline function and more stable outcome than males.

CONCLUSIONS

Our results indicate that low premorbid IQ is a morbid manifestation, easily detected in a subgroup of FEP patients that predicts poorer outcome particularly in males. This perspective provides important information for the tailoring of subgroup-specific early intervention programs for psychosis.

A longitudinal study of cognitive insight and cortical thickness in first-episode psychosis

Among individuals with psychosis, those with poor cognitive insight (lower Self-Reflectiveness, higher Self-Certainty) show volumetric reductions in cortical structure. We evaluated whether changes in cognitive insight are associated with progressive changes in cortical structure in first-episode psychosis (FEP) and control subjects. Beck Cognitive Insight Scale ratings and magnetic resonance imaging scans were acquired at baseline for 130 FEP and 52 controls, 59 FEP and 28 controls at 1-year, and 53 FEP and 20 controls at 2-years. Cortical thickness was computed across scans and analyzed with linear mixed models. At baseline, groups did not differ on Self-Reflectiveness or Self-Certainty. At baseline, higher Self-Reflectiveness significantly correlated with thinner right occipital cortex in FEP, and higher Self-Certainty was significantly negatively correlated with cortical thickness in left posterior cingulate in controls. Longitudinal analysis showed that Self-Reflectiveness and Self-Certainty did not change over time in either group. Interestingly, the lack of change in cognitive insight aligned with longitudinal cortical thickness results, where no interaction effects were seen with cortical thickness between time and either Self-Reflectiveness or Self-Certainty. Exploratory analyses with a reduced threshold found that in FEP, across all time-points, higher Self-Certainty associated with thinner cortex in left posterior cingulate/precuneus. Results suggest that the posterior cingulate may be a common neural correlate for Self-Certainty in FEP and non-clinical subjects.

A Brief Assessment of Intelligence Decline in Schizophrenia As Represented by the Difference between Current and Premorbid Intellectual Quotient

Patients with schizophrenia elicit several clinical features, such as psychotic symptoms, cognitive impairment, and subtle decline of intelligence. The latter two features become evident around the onset of the illness, although they may exist even before the disease onset in a substantial proportion of cases. Here, we review the literature concerning intelligence decline (ID) during the progression of schizophrenia. ID can be estimated by comparing premorbid and current intellectual quotient (IQ) by means of the Adult Reading Test and Wechsler Adult Intelligence Scale (WAIS), respectively. For the purpose of brief assessment, we have recently developed the WAIS-Short Form, which consists of Similarities and Symbol Search and well reflects functional outcomes. According to the degree of ID, patients were classified into three distinct subgroups; deteriorated, preserved, and compromised groups. Patients who show deteriorated IQ (deteriorated group) elicit ID from a premorbid level (≥10-point difference between current and premorbid IQ), while patients who show preserved or compromised IQ do not show such decline (<10-point difference). Furthermore, the latter patients were divided into patients with preserved and compromised IQ based on an estimated premorbid IQ score >90 or below 90, respectively. We have recently shown the distribution of ID in a large cohort of schizophrenia patients. Consistent with previous studies, approximately 30% of schizophrenia patients had a decline of less than 10 points, i.e., normal intellectual performance. In contrast, approximately 70% of patients showed deterioration of IQ. These results indicate that there is a subgroup of schizophrenia patients who have mild or minimal intellectual deficits, following the onset of the disorder. Therefore, a careful assessment of ID is important in identifying appropriate interventions, including medications, cognitive remediation, and social/community services.

Is the association between offspring intelligence and parents' educational attainment influenced by schizophrenia or mood disorder in parents?

Results from twin, family, and adoption studies all suggest that general intelligence is highly heritable. Several studies have shown lower premorbid intelligence in individuals before the onset of both mood disorders and psychosis, as well as in children and adolescents at genetic high risk for developing schizophrenia. Based on these findings, we aim to investigate if the association between educational achievement in parents and intelligence in their offspring is influenced by schizophrenia or mood disorder in parents. In a large population-based sample of young adult male conscripts (n = 156,531) the presence of a mental disorder in the parents were associated with significantly lower offspring scores on a test of general intelligence, the Børge Priens Prøve (BPP), and higher educational attainment in parents was significantly associated with higher BPP test scores in offspring. A significant interaction suggested that the positive association between maternal education and offspring intelligence was stronger in offspring of mothers with schizophrenia compared to the control group (p = 0.03). The associations between parental education and offspring intelligence are also observed when restricting the sample to conscripts whose parents are diagnosed after 30 years of age. In conclusion, findings from this study show a more positive effect of education on offspring intelligence in mothers with schizophrenia compared to mothers from the control group. This effect could have both environmental and genetic explanations.

A New Division of Schizophrenia Revealed Expanded Bilateral Brain Structural Abnormalities of the Association Cortices

The phenomenological and, consequently, pathophysiological heterogeneity of schizophrenia may be substantially decreased by determining etiologically valid subgroups. In a cross-sectional study, we analyzed the brain structural impairments of outpatients with schizophrenia using concurrent subgrouping methods, partly to enhance the extensity of exploration, and partly to estimate the validation of the divisions. High resolution T1-weighted MR images were obtained for 21 patients and 13 healthy controls. Localized gray matter volumetric deficits were defined with optimized voxel-based morphometry. Employing two concurrent methods (i.e., the widely known deficit-non-deficit division vs. the neurocognitive clusters we identified earlier) the patient group was iteratively divided into two subgroups, and their volumetric peculiarities were compared with one another and with healthy controls. Our division revealed more significant differences demonstrating bilateral brain structural deficits, which affected the association cortices, primarily the heteromodal fields and partly the unimodal fields. This is the first study that showed that abnormalities of the association cortices can be bihemispherial and expanded in schizophrenia, even in the cases of outpatients living integrated in society. Our result suggests that the extended association cortex abnormalities could constitute substantial and determining neurological substrates in the phenomenology and aetiopathogenesis of schizophrenia, at least in a subgroup of patients with more unfavorable neurocognitive characteristics.

Familial covariation of facial emotion recognition and IQ in schizophrenia

Alterations in general intellectual ability and social cognition in schizophrenia are core features of the disorder, evident at the illness' onset and persistent throughout its course. However, previous studies examining cognitive alterations in siblings discordant for schizophrenia yielded inconsistent results. Present study aimed to investigate the nature of the association between facial emotion recognition and general IQ by applying genetically sensitive cross-trait cross-sibling design. Participants (total n=158; patients, unaffected siblings, controls) were assessed using the Benton Facial Recognition Test, the Degraded Facial Affect Recognition Task (DFAR) and the Wechsler Adult Intelligence Scale-III. Patients had lower IQ and altered facial emotion recognition in comparison to other groups. Healthy siblings and controls did not significantly differ in IQ and DFAR performance, but siblings exhibited intermediate angry facial expression recognition. Cross-trait within-subject analyses showed significant associations between overall DFAR performance and IQ in all participants. Within-trait cross-sibling analyses found significant associations between patients' and siblings' IQ and overall DFAR performance, suggesting their familial clustering. Finally, cross-trait cross-sibling analyses revealed familial covariation of facial emotion recognition and IQ in siblings discordant for schizophrenia, further indicating their familial etiology. Both traits are important phenotypes for genetic studies and potential early clinical markers of schizophrenia-spectrum disorders.

Working memory and processing speed training in schizophrenia: study protocol for a randomized controlled trial

BACKGROUND

In most domains of cognition, individuals with schizophrenia are generally found to be one standard deviation below the mean of the controls. As a result, examining the impact of cognitive remediation in individuals with schizophrenia has been a burgeoning area of research. However, the state of the literature remains unclear as to which domains of cognition should be targeted to produce the most widespread and durable benefits for individuals with schizophrenia. One suggestion is that targeting lower-level cognitive processes that are important for higher-level and more complex aspects of cognition may produce the most widespread benefits in cognition and everyday functioning. Relatively few studies have examined the effects of working memory or processing speed training in schizophrenia, as most studies examine broad-based remediation programs. Thus, a need exists for targeted working memory and processing speed training studies to better understand the mechanisms of cognitive enhancement in patients. This study aims to 1) investigate near-transfer gains (that is, the transfer of learning to related contexts) associated with working memory and processing speed training in schizophrenia patients; 2) investigate far-transfer gains (that is, the transfer of learning to new contexts) associated with working memory and processing speed training (that is, gains in other neurocognitive domains and social cognition); and 3) investigate real-world gains associated with training (that is, gains in daily functioning).

METHODS/DESIGN

A double-blind randomized controlled trial with a three parallel group design will be conducted. A random sample of 81 patients with schizophrenia or schizoaffective disorder will be recruited through outpatient clinics at Foothills Hospital and community support programs in Calgary, Alberta. Participants will be randomly assigned using a computer-generated program in a 1:1:1 ratio to a working memory-training group, a processing speed-training group, or a no-training control group. Training will be completed at home for 30 minutes per day, 5 days per week, for a total of 10 weeks. Neurocognitive, social cognitive, and daily functioning measures will be administered both pre- and post-training to detect training-related gains. The primary outcome measures will include working memory and processing speed (near-transfer measures), as well as fluid intelligence (far-transfer measure).

TRIAL REGISTRATION

Current controlled trials NCT02478827 (ClinicalTrials.gov, registered on 15 June 2015).

Comparing cognitive functions in medication adherent and non-adherent patients with schizophrenia

BACKGROUND

Medication non-adherence presents a considerable problem in patients with schizophrenia. Cognitive and executive functions can affect adherence. The association between medication non-adherence and cognitive impairment in schizophrenia is under investigated with limited and conflicting research data.

PURPOSE OF THE STUDY

To prospectively assess the rate of drug adherence among a sample of patients with schizophrenia and to compare the cognitive and executive functions between adherent and non-adherent patients.

SUBJECTS AND METHODS

109 patients with schizophrenia diagnosed according to the DSM-IV classification were initially assessed by the Wechsler Adult Intelligence Scale (WAIS), Wechsler Memory Scale-Revised (WMS-R) and Wisconsin Card Sorting Test (WCST) and six months later by the Brief Adherence Rating Scale (BARS).

RESULTS

68.8% were non-adherent to their antipsychotic medication. Adherent patients (31.2%) had significantly higher mean scores for the total, verbal and performance IQ. They had significantly higher mean scores in most of WMS subtests (orientation, information, verbal paired association, digit span, visual memory span), and higher mean scores for; total correct, conceptual level response, percentage and categories completed on the WSCT subscales (P < 0.0001). Whereas the non-adherent group had higher mean scores in; trials administered, total errors, perseverative responses, and perseverative errors (P < 0.0001). In a step regression analysis, digit span, conceptualization, total and percentage of errors were putative predictors of non-adherence.

CONCLUSION

Cognitive deficits, especially verbal memory and executive functions were the strongest patients' related factors associated with non adherence to medication. Psychiatrists ought to consider possible cognitive factors influencing adherence to enable offering proper interventions.

Cognitive deficit awareness in schizophrenia: absent, intact, or somewhere in-between?

INTRODUCTION

Cognitive impairment is a pervasive feature of schizophrenia, and is a major determinant of the functional disability that is characteristic of the disorder. However, research investigating whether patients with schizophrenia show a deficit awareness remains unclear. The present study aimed to replicate and extend previous research comparing subjective and objective measures of cognition.

METHODS

. Thirty patients with a diagnosis of schizophrenia or schizoaffective disorder were administered the subjectively assessed Schizophrenia Cognitive Rating Scale (SCoRS) and the objective Brief Assessment of Cognition in Schizophrenia (BACS), which each assess overall global functioning and four specific neurocognitive domains (i.e., Verbal Memory, Working Memory, Processing Speed, and Reasoning and Problem Solving). Because deficit awareness may influence the likelihood of patients engaging in treatments designed to improve cognitive functioning, patients' attitudes towards such therapies were also contrasted with these subjective and objective measures of cognitive functioning.

RESULTS

Patients' subjective appraisals did not significantly correlate with the objective neuropsychological assessments for global functioning or any specific neurocognitive domains. However, patients accurately deduced that their memory domains were more impaired than the other domains, and there was a trend for patients to exaggerate their Reasoning and Problem Solving deficits. This suggests that patients show some level of deficit awareness, when overestimating "deficits" for domains that are not impaired. Finally subjective, but not objective, measures of cognitive functioning correlated significantly with willingness to participate in cognitive-enhancing therapies.

CONCLUSIONS

These results suggest that although patients' perceptions of their cognitive function are no substitute for objective neuropsychological test data, patients do possess a level of deficit awareness which may, in turn, influence willingness to participate in interventions such as cognitive rehabilitation.

Community outcome in cognitively normal schizophrenia patients

Recent reports suggest that cognition is relatively preserved in some schizophrenia patients. However, little is known about the functional advantage these patients may demonstrate. The purpose of this study was to identify cognitively normal patients with a recently developed test battery and to determine the functional benefit of this normality relative to cognitively impaired patients. Average-range cognitive ability was defined by the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) composite score (T≥40) and applied to 100 patients with schizophrenia or schizoaffective disorder and to 81 non-psychiatric research participants. With group assignment adjusted for demographic variables, this procedure yielded 14 cognitively normal patients, 21 cognitively impaired patients, and 21 healthy adults with normal-range MCCB scores. Cognitively normal patients were indistinguishable from controls across all MCCB scales. Furthermore, their performance was superior to impaired patients on all scales except Social Cognition. Cognitively normal patients were also superior to impaired patients on a summary index of simulated life skills and functional competence. Nevertheless, both patient groups were equally disadvantaged relative to controls in independent community living. These findings suggest that normal-range cognition exists in schizophrenia, but fails to translate into enhanced community outcome.

Performance on the Wechsler Adult Intelligence Scale-III in Japanese patients with schizophrenia

AIM

Patients with schizophrenia have been reported to perform worse than non-schizophrenic populations on neuropsychological tests, which may be affected by cultural factors. The aim of this study was to examine the performance of a sizable number of patients with schizophrenia on the Japanese version of the Wechsler Adult Intelligence Scale-III (WAIS-III) compared with healthy controls.

METHODS

Performance on the WAIS-III was evaluated in 157 Japanese patients with schizophrenia and in 264 healthy control subjects.

RESULTS

All IQ scores and four indices from the WAIS-III were impaired for patients with schizophrenia compared with healthy controls. Processing Speed was markedly disturbed, approximately 2 SD below that of the healthy control group. Among the 13 subtests, Comprehension (z = -1.70, d = 1.55), Digit Symbol Coding (z = -1.84, d = 1.88), and Symbol Search (z = -1.85, d = 1.77) were profoundly impaired relative to the healthy controls.

CONCLUSION

These results indicate that the pattern and degree of impairment, as evaluated by the WAIS-III, in Japanese patients are similar to those previously reported in English-speaking patients and that the deficits of some neuropsychological domains relevant to functional outcomes are universally characteristic of schizophrenia.

Cognitive function, plasma MnSOD activity, and MnSOD Ala-9Val polymorphism in patients with schizophrenia and normal controls

Excessive reactive oxygen species are thought to produce oxidative damage that underlies neurodegeneration and cognitive impairment in several disorders including schizophrenia. The functional Ala-9Val polymorphism of the mitochondrial enzyme manganese superoxide dismutase (MnSOD), which detoxifies superoxide radicals to hydrogen peroxide, has been associated with schizophrenia. However, no study has reported its role in cognitive deficits of schizophrenia as mediated through MnSOD activity. We recruited 923 schizophrenic inpatients and 566 healthy controls and compared them on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), plasma MnSOD activity, and the MnSOD Ala-9Val polymorphism. We assessed patient psychopathology using the Positive and Negative Syndrome Scale. We showed that the MnSOD Ala-9Val polymorphism may not contribute directly to the susceptibility to schizophrenia. The Ala variant was associated with worse attention performance among chronic schizophrenic patients but not among normal controls. Plasma MnSOD activity was significantly decreased in patients compared with that in normal controls. Moreover, MnSOD activity among the schizophrenic Ala allele carriers was correlated with the degree of cognitive impairments, especially attention and RBANS total score. We demonstrated an association between the MnSOD Ala-9Val variant and poor attention in schizophrenia. The association between higher MnSOD activity and cognitive impairment in schizophrenia is dependent on the MnSOD Ala-9Val polymorphism.

Neurocognitive Decrements are Present in Intellectually Superior Schizophrenia

Data suggest that individuals with schizophrenia (SZ) and superior intelligence can present without specific neurocognitive deficits. However, neurocognitive decrements, defined as worse cognition than expected, have been reported in practically all SZ cases. This study investigated if neurocognitive decrements are present in intellectually superior SZ by comparing the neuropsychological profile of SZ cases with IQ-matched healthy controls (HC) across intellectual levels. Participants with SZ and HCs were stratified into three IQ-groups; intellectually low (IQ 80-95; SZ n = 65 and HC n = 13), intellectually normal (IQ = 100-115; SZ n = 111 and HC n = 115), and intellectually superior (IQ ≥ 120; SZ n = 20 and HC n = 50). A repeated measures multivariate analysis of co-variance compared performance on eight selected neuropsychological tests across IQ-strata and diagnostic group. Differences in clinical characteristics and social functioning in SZ across IQ-strata were investigated with multivariate and univariate analyses of variance. Intellectually superior SZ participants scored within normal limits, but had neurocognitive decrements compared to superior HCs. Decrements were of the same magnitude as in the low and normal IQ-strata. Levels of functional impairments and clinical characteristics in participants with SZ did not differ significantly across IQ-strata. Results indicate that neurocognitive decrements are present in intellectually superior SZ to the same extent as in intellectually low and intellectually normal SZ, supporting the notion that SZ is a neurocognitive disorder. Similar levels of social functional deficits and clinical symptoms suggest similar disease processes in SZ across intellectual level.

Impact of peripheral levels of chemokines, BDNF and oxidative markers on cognition in individuals with schizophrenia

OBJECTIVE

To investigate possible differences in peripheral levels of chemokines, BDNF and oxidative markers between patients with Schizophrenia (SZ) and matched healthy controls, and investigate the correlation of these biomarkers with cognitive performance.

METHODS

Thirty individuals with SZ and 27 healthy controls were included and the following plasmatic biomarkers' levels were determined according to manufacturers' instructions: BDNF, TBARS, protein carbonyl content (PCC) and the chemokines CXCL-10/IP-10, CXCL-8/IL-8, CCL-11, CCL-24/Eotaxin-2, CCL-2/MCP-1, CCL-3/MIP-1. Selected neuropsychological tasks were administered to assess verbal learning (Hopkins Verbal Learning Test), verbal fluency (FAS test), working memory (Visual Working Memory Task, Keep Track Task, Letter Memory Task), set shifting (Plus-minus task, Number-letter task), inhibition (Computerized Stroop Task, Semantic Generation Task) and complex executive function tasks (Tower of London and the shortened version of the WCST-64).

RESULTS

Compared with the healthy control group, individuals with SZ presented significantly higher levels of BDNF and the chemokine CCL-11, and lower levels of TBARS and the chemokine CXCL-10/IP-10. When we examined only the SZ group, BDNF levels were positively correlated with semantic generation tasks. Working memory ability was negatively correlated with PCC. Regarding chemokines, CCL-11 was negatively correlated to performance in working memory test, and positively correlated with cognitive flexibility task. CXCL-8/IL-8 was positively correlated with verbal fluency. CCL-24/Eotaxin-2 was positively correlated with semantic generation ability and letter memory task.

CONCLUSIONS

Our results indicate that cognitive performance in SZ is associated with mediators of neuroplasticity that can be measured peripherally.

Cognitive profiles of three clusters of patients with a first-episode psychosis

OBJECTIVE

The primary objective was to identify specific groups of patients with a first-episode psychosis based on family history, obstetric complications, neurological soft signs, and premorbid functioning. The secondary objective was to relate these groups with cognitive variables.

METHOD

A total of 62 first-episode psychoses were recruited from adult and child and adolescent mental health services. The inclusion criteria were patients between 7 and 65 years old (real range of the samples was 13-35 years old), two or more psychotic symptoms and less than one year from the onset of the symptoms. Premorbid functioning (PAS), soft signs (NES), obstetric complications and a neuropsychological battery (CPT, TMTA/TMTB, TAVEC/TAVECI, Stroop, specific subtest of WAIS-III/WISC-IV) were administered.

RESULTS

We found three clusters: 1) higher neurodevelopment contribution (N=14), 2) higher genetic contribution (N=30), and 3) lower neurodevelopment contribution (N=18). Statistical differences were found between groups in TMTB, learning curve of the TAVEC, digits of the WAIS and premorbid estimated IQ, the cluster 1 being the most impaired.

CONCLUSIONS

A cluster approach could differentiate several groups of patients with different cognitive performance. Neuropsychological interventions, as cognitive remediation, should be addressed specifically to patients with more impaired results.

Executive functioning in schizophrenia: the result of impairments in lower order cognitive skills?

Executive functioning (EF) impairments are common in schizophrenia. There are two propositions regarding the causes of these impairments: (1) executive impairments are the result of the compounding effects of deficits in lower order cognitive skills (e.g. processing speed, attention) or (2) EF impairments exist in their own right regardless of lower order skills. It is difficult to examine the separable effects of lower order cognitive skills on EF given the overlap required to complete most neuropsychological measures. One battery designed to parcel out the contributions of lower order skills from EF is the Delis-Kaplan Executive Function System (D-KEFS). Inhibition and switching specifically were examined using the D-KEFS versions of the Stroop and Trails task. No group differences in task performance after controlling for lower level skills would provide evidence for a generalised cognitive deficit. Group differences remaining after controlling for these influences would suggest a disproportionate deficit. Results supported both propositions. On both tasks, group differences reflecting slowed reaction time in the schizophrenia group disappeared when lower order skills were controlled for. Differences between groups performance in errors were only evident on the most complex versions of each task with more errors made by the schizophrenia group. These results suggest that (1) both RT and error data are needed to provide a full picture of performance and (2) the relationship between lower order and EF is too complex to provide support for one or the other proposal.

Insight in schizophrenia: associations with empathy

Many people with schizophrenia (50-80%) demonstrate impaired insight, something which has been associated with a poorer outcome. Two types of empathy can be distinguished: affective empathy via shared emotions and cognitive empathy, also referred to as Theory of Mind (ToM). ToM can be subdivided into cognitive ToM (knowledge about beliefs of other people via perspective taking) and affective ToM (knowledge about other people's emotions via perspective taking). Recent studies show a relationship between Theory of Mind (ToM) and insight. However, the relationship between affective empathy and insight in schizophrenia was not examined previously. This was the aim of the present study. We expected that affective empathy would show a stronger relationship with insight than both cognitive and affective ToM. We assessed forty-six patients with a diagnosis of schizophrenia, and fifty-three healthy controls were assessed with a test battery consisting of tests of social cognition (a self-rating scale for affective empathy, a ToM task assessing both cognitive and affective ToM, and two tests of emotion perception), verbal memory, executive functioning, psychomotor speed, and intelligence. Insight was assessed with item G12 of the PANSS-interview. A regression equation showed that affective empathy made the strongest unique contribution to insight, followed closely by affective ToM. Together, they explained 45% of the variance in insight. None of the other independent variables made a unique contribution to the prediction of insight. Both affective ToM and affective empathy are associated with insight in schizophrenia. Being able to take empathize with other peoples feeling at both the affective and cognitive level may enhance insight in schizophrenia.

Change in neuropsychological functioning over one year in youth at clinical high risk for psychosis

Schizophrenia and related psychotic disorders are associated with significant neuropsychological (NP) impairments. Yet the onset and developmental evolution of these impairments remains incompletely characterized. This study examined NP functioning over one year in a sample of youth at clinical high risk (CHR) for psychosis participating in a treatment study. We assessed functioning across six cognitive domains at two time points in a sample of 53 CHR and 32 healthy comparison (HC) subjects. Linear regression of HC one-year scores was used to predict one-year performance for CHR from baseline scores and relevant demographic variables. We used raw scores and MANOVAs of the standardized residuals to test for progressive impairment over time. NP functioning of CHR at one year fell significantly below predicted levels. Effects were largest and most consistent for a failure of normative improvement on tests of executive function. CHR who reached the highest positive symptom rating (6, severe and psychotic) on the Structured Interview of Prodromal Syndromes after the baseline assessment (n = 10/53) demonstrated a particularly large (d = -1.89), although non-significant, discrepancy between observed and predicted one-year verbal memory test performance. Findings suggest that, although much of the cognitive impairment associated with psychosis is present prior to the full expression of the psychotic syndrome, some progressive NP impairments may accompany risk for psychosis and be greatest for those who develop psychotic level symptoms.

Has the generalized deficit become the generalized criticism?

The "generalized cognitive deficit problem" refers to a situation in which a generalized deficit gives the false appearance of a specific deficit due to the psychometric properties of tests, and it is an important methodological consideration in schizophrenia research. However, it also generates considerable confusion and is often used indiscriminately as a scientific criticism, even in situations to which it does not apply. Further, the generalized deficit problem creates few concerns in interpretation for many central questions in contemporary schizophrenia research. The research literature has shifted away from the traditional goal of identifying generalized vs differential deficits, and the field now demonstrates (1) increased recognition that a generalized deficit, broadly defined, probably does not exist in schizophrenia, (2) increased emphasis on explaining both shared and unique variance across measures to understand the mechanisms through which cognition relates to external variables (eg, functional outcome), and (3) increased use of neuroscientific methods to explore cognition in schizophrenia in which the structure and richness of data can be used to minimize misinterpretation of the sort that can occur when using only behavioral measures. Clearly, consideration of the generalized deficit still remains essential in certain experimental contexts, but criticisms based on this concern are unwarranted in many other situations in schizophrenia research. This commentary is intended to help clarify the distinctions between these 2 situations so that concerns will be expressed in a more selective, less reflexive, manner.

Executive attention impairment in first-episode schizophrenia

BACKGROUND

We compared the attention abilities of a group of first-episode schizophrenia (FES) patients and a group of healthy participants using the Attention Network Test (ANT), a standard procedure that estimates the functional state of three neural networks controlling the efficiency of three different attentional behaviors, i.e., alerting (achieving and maintaining a state of high sensitivity to incoming stimuli), orienting (ability to select information from sensory input), and executive attention (mechanisms for resolving conflict among thoughts, feelings, and actions).

METHODS

We evaluated 22 FES patients from 17 to 29 years of age with a recent history of a single psychotic episode treated only with atypical neuroleptics, and 20 healthy persons matched with FES patients by sex, age, and educational level as the control group. Attention was estimated using the ANT in which participants indicate whether a central horizontal arrow is pointing to the left or the right. The central arrow may be preceded by spatial or temporal cues denoting where and when the arrow will appear, and may be flanked by other arrows (hereafter, flankers) pointing in the same or the opposite direction.

RESULTS

The efficiency of the alerting, orienting, and executive networks was estimated by measuring how reaction time was influenced by congruency between temporal, spatial, and flanker cues. We found that the control group only demonstrated significantly greater attention efficiency than FES patients in the executive attention network.

CONCLUSIONS

FES patients are impaired in executive attention but not in alerting or orienting attention, suggesting that executive attention deficit may be a primary impairment during the progression of the disease.

Plasma total antioxidant status and cognitive impairments in schizophrenia

Oxidative stress-induced damage to neurons may contribute to cognitive deficits during aging and in neurodegenerative disorders. Schizophrenia has a range of cognitive deficits that may evolve from oxidative stress, and this study examines this association of oxidative stress with cognitive deficits in schizophrenia. We recruited 296 chronic schizophrenia patients and 181 healthy control subjects and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and plasma total antioxidant status (TAS) in both groups. Schizophrenia symptoms were assessed using the positive and negative syndrome scale (PANSS). Our results showed that TAS levels were significantly lower in patients than controls (179.6 ± 81.0 U/ml vs. 194.8 ± 46.0 U/ml, p<0.05). Cognitive scores on the RBANS and nearly all of its five subscales (all p<0.001) except for the Visuospatial/Constructional index (p>0.05) were significantly lower in schizophrenia patients than normal controls. For the patients, TAS was inversely associated with some domains of cognitive deficits in schizophrenia, such as Attention and Immediate Memory. Our findings suggest that oxidative stress may be involved in the pathophysiology of schizophrenia, and its associated cognitive impairment.

Schizophrenia comorbid with panic disorder: evidence for distinct cognitive profiles

Patients with comorbid schizophrenia and panic symptoms share a distinct clinical presentation and biological characteristics, prompting some to propose panic psychosis as a separate subtype of schizophrenia. Less is known about these patients' neuropsychological profiles, knowledge of which may facilitate target-specific treatments and research into the etiopathophysiology for such cases. A total of 255 schizophrenia patients with panic disorder (n=39), non-panic anxiety disorder (n=51), or no anxiety disorder (n=165) were assessed with the Wechsler Adult Intelligence Scale-Revised, the Wisconsin Card Sorting Test, the Trail Making Test, the Controlled Oral Word Association Test, the Animal Naming subtest of the Boston Diagnostic Aphasia Examination, and the Wechsler Memory Scale-Revised. Psychotic symptoms were assessed with the Positive and Negative Syndrome Scale. Patients with panic disorder demonstrated a higher verbal IQ and better problem solving, set switching, delayed recall, attention, and verbal fluency as compared to schizophrenia patients without comorbid anxiety. The schizophrenia-panic group reported a higher level of dysthymia on stable medication. Our findings suggest that patients with schizophrenia and comorbid panic disorder exhibit distinct cognitive functioning when compared to other schizophrenia patients. These data offer further support for a definable panic-psychosis subtype and suggest new etiological pathways for future research.

Can genetics inform the management of cognitive deficits in schizophrenia?

There is no doubt that schizophrenia has a significant genetic component and a number of candidate genes have been identified for this debilitating disorder. Of note, several of these are implicated in cognition. Cognitive deficits constitute core symptoms of schizophrenia, and while current antipsychotic treatment strategies aim to help psychosis-related symptomatology, the cognitive symptom domain is largely inadequately treated. A number of other pharmacological approaches (e.g. using drugs that target specific neurotransmitter systems) have also been attempted for the amelioration of cognitive deficits in this population; however, these too have had limited success so far. Psychological interventions appear promising, though there has been speculation regarding whether or not these produce long-term functional improvements. Pharmacogenetic studies of the cognitive effects of currently available antipsychotics, although in relatively early stages, suggest that the treatment of cognitive deficits in schizophrenia may be advanced by focusing on genetic variants associated with specific cognitive dysfunctions in the general population and using this to match the most relevant pharmacological and/or psychological interventions with the genetic and cognitive profiles of the target population. Such a strategy would encourage bottom-up advances in drug development and provide a platform for individualised treatment of cognitive deficits in schizophrenia.

Transcranial direct current stimulation influences probabilistic association learning in schizophrenia

Schizophrenia is associated with heterogeneity in symptoms, cognition and treatment response. Probabilistic association learning, involving a gradual learning of cue-outcome associations, activates a frontal-striatal network in healthy adults. Studies of probabilistic association learning in schizophrenia have shown frontal-striatal dysfunction although considerable heterogeneity in performance has also been reported. Anodal transcranial direct current stimulation (tDCS) to the dorsolateral prefrontal cortex has been shown to improve probabilistic association learning in healthy adults. The aim of the current study was to determine the extent to which anodal tDCS to the left dorsolateral prefrontal cortex would reverse probabilistic association learning deficits in schizophrenia. Prior to tDCS, 20 people with schizophrenia performed an initial baseline assessment without stimulation. Anodal tDCS was administered continuously for 20 min at an intensity of 2.0 mA to the left dorsolateral prefrontal cortex in a single-blind, counterbalanced, sham-controlled, cross-over design while participants performed 150 trials of a probabilistic association learning test. Although anodal tDCS failed to improve probabilistic association learning based on the whole sample performance, greater variance in the active relative to the sham conditions suggested a subset of people may respond to treatment. Further correlation, regression and cluster analyses revealed differential effects of baseline performance on active tDCS and sham treatment and that there was a subset of people with schizophrenia who displayed improvement with tDCS suggesting that anodal tDCS to the dorsolateral prefrontal cortex may facilitate access to existing prefrontal cortex neural reserves in people with schizophrenia who show adequate capacity to learn at baseline.

Familial liability, obstetric complications and childhood development abnormalities in early onset schizophrenia: a case control study

BACKGROUND

Genetic and environmental risk factors and gene-environment interactions are linked to higher likelihood of developing schizophrenia in accordance with the neurodevelopmental model of disease; little is known about risk factors and early development in early-onset schizophrenia (EOS) and very early-onset schizophrenia (VEOS).

METHODS

We present a case-control study of a sample of 21 patients with EOS/VEOS and a control group of 21 patients with migraine, recruited from the Child Neuropsychiatry Unit, Department of Neurologic and Psychiatric Science, University of Bari, Italy. The aim was to assess the statistical association between VEOS/EOS and family history for psychiatric disorders, obstetric complications and childhood developmental abnormalities using 2 × 2 tables and a Chi Squared or Fisher test.

RESULTS

The results show a statistical association between EOS/VEOS and schizophrenia and related disorders (P = 0.02) and personality disorders (P = 0.003) in relatives, and between EOS/VEOS and developmental abnormalities of early relational skills (P = 0.008) and learning (P = 0.04); there is not a statistically relevant difference between cases and controls (P > 0.05) for any obstetric complications (pre, peri and postpartum).

CONCLUSIONS

This study confirms the significant role of familial liability but not of obstetric complications in the pathogenesis of VEOS/EOS; the association between childhood developmental abnormalities and EOS/VEOS supports the neurodevelopmental model of disease.

Evaluation of specific executive functioning skills and the processes underlying executive control in schizophrenia

Schizophrenia is associated with executive dysfunction. Yet, the degree to which executive functions are impaired differentially, or above and beyond underlying basic cognitive processes is less clear. Participants included 145 matched pairs of individuals with schizophrenia (SCs) and normal comparison subjects (NCs). Executive functions were assessed with 10 tasks of the Delis-Kaplan Executive Function System (D-KEFS), in terms of "achievement scores" reflecting overall performance on the task. Five of these tasks (all measuring executive control) were further examined in terms of their basic component (e.g., processing speed) scores and contrast scores (reflecting residual higher order skills adjusted for basic component skills). Group differences were examined via multivariate analysis of variance. SCs had worse performance than NCs on all achievement scores, but the greatest SC-NC difference was that for the Trails Switching task. SCs also had worse performance than NCs on all basic component skills. Of the executive control tasks, only Trails Switching continued to be impaired after accounting for impairments in underlying basic component skills. Much of the impairment in executive functions in schizophrenia may reflect the underlying component skills rather than higher-order functions. However, the results from one task suggest that there might be additional impairment in some aspects of executive control.

The relationship between IQ, memory, executive function, and processing speed in recent-onset psychosis: 1-year stability and clinical outcome

Studies commonly report poor performance in psychotic patients compared with controls on tasks testing a range of cognitive functions, but, because current IQ is often not matched between these groups, it is difficult to determine whether this represents a generalized deficit or specific abnormalities. Fifty-three first-episode psychosis patients and 53 healthy controls, one-to-one matched for sex, age, and full-scale current IQ, were compared on Wechsler Adult Intelligence Scale (WAIS) subtests representing indices of perceptual organization, verbal comprehension, processing speed, and working memory as well as other tests of executive function and episodic memory. The groups showed an equivalent pattern of performance on all WAIS subtests except digit symbol processing speed, on which the patients were significantly worse. Patients were also worse on measures where performance correlated with digit symbol score, namely working and verbal memory tasks. Standardized residual scores for each subtest were calculated for each patient using the difference between their actual subtest score and a predicted subtest score based on their full-scale IQ and the performance of controls. Scaled scores and residual scores were examined for relationships with clinical measures. Digit symbol-scaled score was significantly correlated with concurrent negative syndrome score at baseline, and digit symbol residual score significantly predicted residual negative symptoms at 1-year follow-up. In summary, our comparison of patients and controls precisely matched for IQ revealed that processing speed was attenuated in recent-onset schizophrenia, contributed significantly to working and episodic memory deficits, and was a prognostic factor for poor outcome at 1 year.

Neuropsychological functioning in first-episode schizophrenia

BACKGROUND

Identifying neurocognitive subtypes in schizophrenia may help establish neurobiologically meaningful subtypes of the disorder, but is frequently confounded by differences in intellectual function between individuals with schizophrenia and controls.

AIMS

To examine neuropsychological performance in individuals with epidemiologically based, first-onset schizophrenia and intellectually matched controls.

METHOD

Using standard IQ and reading tests, we examined the proportions of 101 people with epidemiologically derived, first-onset schizophrenia/schizoaffective disorder and 317 community controls, falling into three a priori defined intellectual categories: 'stable good', 'deteriorated poor' and 'stable poor'. Neuropsychological function was compared between intellectually matched participants with schizophrenia and control subgroups.

RESULTS

Multiple deficits in executive function, processing speed and verbal memory, but not visual/spatial perception/memory, were detected in all participant groups with schizophrenia compared with controls. The average effect size across the affected domains ranged from small to medium to large in the stable good, deteriorated poor and stable poor subgroups of participants with schizophrenia, respectively.

CONCLUSIONS

Compared with intellectually matched controls, people with epidemiologically derived, first-onset schizophrenia/schizoaffective disorder show multiple deficits in executive function, processing speed and verbal memory.

Executive dysfunction in Turkish children at high risk for schizophrenia

OBJECTIVE

To explore different aspects of executive function (i.e. sequencing, set shifting and mental flexibility) in children who are at high risk for schizophrenia by comparing them with normal controls.

METHOD

The high risk (HR) group consisted of 30 children whose parents were diagnosed as schizophrenia. As the control group (CG) 30 children, whose parents did not meet any DSM IV diagnostic criteria for any psychiatric disorder, participated. They were age and sex matched with the HR group. For the evaluation of different domains of cognitive functions Wechsler intelligence scale for children-revised (WISC-R), and a group of neuropsychological tests, including Trail Making A-B Tests, Color Form Test, and Progressive Figures Test were administered. Behavioral problems were assessed using Hacettepe Adjustment Scale.

RESULTS

The subjects in the high risk group had significantly lower scores on Trail Making A-B, Color Form, Progressive Figures Tests, as well as subtests and scores of WISC-R (Information, Comprehension, Similarities, Picture Completion, Block Design, Object Assembly and Coding subtests, Verbal, Performance and Full Scale IQ scores). There is no significant difference between the two groups in the frequency and severity of behavioral problems.

CONCLUSION

Children of parents with schizophrenia displayed significantly greater number of difficulties in several areas of executive function, such as sequencing, set shifting, and mental flexibility, when compared to their controls.

IQ decline in cross-sectional studies of schizophrenia: methodology and interpretation

Some researchers have compared neuropsychological performance in schizophrenia groups with and without presumed IQ decline. Inherent in this approach is an assumption that group differences are due to different IQ trajectories (stable vs. declining), but neuropsychological differences could be a function of current IQ regardless of the presence or absence of previous IQ decline. We examined this issue in 93 normal controls and in 80 patients classified as having preserved (27.5%), deteriorated (50%), or compromised (22.5%) intellect based on IQ and reading recognition-IQ difference scores. We also examined group differences in verbal and performance IQ. Deteriorated patients had the largest verbal performance-IQ differences. They were more neuropsychologically impaired than the preserved group (average effect size=0.43), but deteriorated patients also had significantly lower current IQs. When subgroups of preserved and deteriorated patients with equivalent current IQs were compared, neuropsychological differences were essentially eliminated (average effect size=0.10); however, both groups were significantly more impaired than controls with similar IQs. Neuropsychological impairment, even in patients with apparently preserved IQ, is consistent with a prefrontal-dysexecutive syndrome. Overall, these results strongly suggest that differences in current neuropsychological function in schizophrenia are attributable primarily to current IQ instead of to IQ trajectory over time.

Cognitive deficits in early-onset schizophrenia spectrum patients and their non-psychotic siblings: a comparison with ADHD

BACKGROUND

Previous research has shown cognitive deficits in patients with schizophrenia spectrum disorders in the areas of executive function, verbal memory and attention. Subtle deficits have been shown in healthy first-degree relatives of patients, suggesting that they may be trait markers. The specificity of these markers for schizophrenia compared with another neurodevelopmental disorder, Attention Deficit Hyperactivity Disorder (ADHD) has not been reliably established.

METHODS

The Rey Auditory Verbal Learning Test (RAVLT), Hayling Sentence Completion Test (HSCT), FAS Test of orthographic verbal fluency (FAS) and Continuous Performance Test-Identical Pairs (CPT-IP) were administered to adolescent schizophrenia spectrum patients (SZ; n=30), adolescent siblings of schizophrenia spectrum patients (SZ-SIB; n=36), healthy control participants (HC; n=72); a neurodevelopmental comparison group of adolescents with ADHD (n=27).

RESULTS

The SZ group were impaired on all measures. The SZ-SIB group were impaired on IQ, immediate recall (RAVLT), target sensitivity (CPT-IP), response initiation (HSCT); error rates for the FAS and HSCT. There were no significant differences between the SZ-SIB and ADHD groups on individual measures of cognitive function. Principal Components Analysis revealed four factors on which further analyses were conducted. The SZ-SIB and ADHD groups showed different profiles of impairment on components related to response initiation and sustained attention/vigilance when each was compared with the HC group.

CONCLUSIONS

Deficits in intellectual function, verbal memory and response initiation/inhibition were found in the SZ-SIB group indicating that these are markers of risk for schizophrenia. Subtle differences in profiles of impairment in the SZ-SIB and ADHD groups on composite measures of attention and response initiation require further investigation.

Cognitive heterogeneity in schizophrenia

PURPOSE

Further clarification of the nature of cognitive heterogeneity in schizophrenia is needed to aid the endophenotype approach to the understanding of the genetic basis of the disorder. This review summarizes recent neuropsychological studies of schizophrenia, aimed at establishing whether there are valid forms of cognitive impairment that can be defined with the use of neuropsychological measures in patients with schizophrenia, and studies that have attempted to relate specific neuropsychological findings to genetic polymorphisms.

RECENT FINDINGS

There is good evidence for significant cognitive heterogeneity in schizophrenia. It is not yet clear, however, whether this heterogeneity is better accounted for by a general loss of function, varying in degree between different patients, or by impairment in specific cognitive abilities, for example working memory. Molecular genetic studies have provided evidence for associations of single nucleotide polymorphisms with both specific and general impairments, with some additional support for a working memory deficit from neuroimaging studies.

SUMMARY

Larger, better controlled studies are needed before the genetic sources of cognitive heterogeneity in schizophrenia can be accurately characterized. This will be aided with the development and use of more specific neuropsychological tasks that can accurately discriminate between different cognitive domains.

Intellectual functioning and memory deficits in schizophrenia

BACKGROUND

There is converging evidence about the existence of different subgroups of patients with schizophrenia in relation to intellectual ability (intelligence quotient [IQ]). Studying cognitive deficits in such patients in relation to IQ, and more specifically to memory, could help determine the patterns of preserved and impaired functioning in cognitive abilities in association with patterns of preserved and compromised intellect. This information could serve to delimit the possibilities of treatment and rehabilitation in those patients.

METHODS

A total of 44 patients with schizophrenia completed a cognitive battery that included executive functioning, attention, speed of information processing, working memory, explicit memory, implicit memory, and everyday memory. Their IQ was also measured to identify 2 subgroups with an IQ of 85 as the cutoff point. Then, differences between the groups in the neurocognitive measures were studied.

RESULTS

Performance in executive functioning, attention, working memory, and everyday memory, but not that in speed of information processing, explicit memory, and implicit memory, was associated with intellectual functioning. Patients performed at the same level in perceptual implicit memory but at a lower level in conceptual implicit memory as did healthy control subjects.

DISCUSSION

Cognitive deficits in schizophrenia are associated with intellectual functioning. Implicit memory should not be considered as a unique entity. It is suggested that conceptual implicit memory deficit may be a core feature of schizophrenia.

Cognitive Development in Schizophrenia: Follow-Back from the First Episode

Despite consensus that schizophrenia is a neurodevelopmental disorder characterized by cognitive deficits, objective data documenting the course of cognitive development remain sparse. We conducted a follow-back study of patients ascertained at the time of their initial episode of schizophrenia or schizoaffective disorder, and a group of demographically matched healthy volunteers. We obtained school records containing standardized achievement test scores from the 1st through 12th grades, and scholastic aptitude test results from the 11th and 12th grades, and examined the developmental trajectories of cognitive performance with respect to prospective examinations conducted following participants' enrollment in our study. We found significant differences in academic achievement tests as early as the first grade, with scores from participants who would later develop schizophrenia lagging behind their peers by 0.8 to 1.1 grade equivalents. This gap widened resulting in a difference between groups of 1.5 to 1.8 grade equivalents by the 12th grade. In the subset of patients for whom SAT scores were available, we found that WAIS-R Full Scale IQ was 11.5 points lower than predicted from earlier SAT scores, suggesting a substantial decline in cognitive ability accompanying the initial episode of illness. These findings suggest that schizophrenia is marked by substantial cognitive deficits in the first grade, that there may be additional subtle decline preceding the overt onset of psychotic symptoms, and that the initial episode of illness is marked by additional decline. These observations may help advance concepts of premorbid cognitive ability in the schizophrenia syndrome and constrain models of pathophysiology.

A Discordant Twin Study of Premorbid Cognitive Ability in Schizophrenia

Twin studies are advantageous because sources of genetic and environmental variation are equated in ways that are not possible in standard case-control designs. We examined premorbid cognitive ability by comparing Armed Forces Qualification Test scores administered at the time of military enlistment in 21 schizophrenia-discordant twin pairs and 860 matched control twins. Scores were significantly lower in schizophrenia probands than in their nonpsychotic co-twins; co-twins were midway between probands and control twins. Effects were reduced when the discordant pairs were extended to include 33 psychosis-discordant pairs. Compared with controls, education at enlistment was significantly lower in psychosis probands and in co-twins from both schizophrenia- and psychosis-disordant pairs. Co-twins from psychosis-discordant pairs had significantly lower education at midlife than controls. Results suggest that cognitive ability is influenced by familial vulnerability for schizophrenia or psychosis, and that premorbid cognitive ability is lower in schizophrenia versus psychosis in general. Educational advancement may be slightly slowed by this familial vulnerability, but results were equivocal with regard to attenuation of one's ultimate educational attainment.

Intellectual Decline in Schizophrenia: Evidence from a Prospective Birth Cohort 28 Year Follow-up Study

It is well established that IQ is lower among persons with schizophrenia than in the general population. However, it remains unclear if there is deterioration beyond a premorbid deficit. In order to assess the question of IQ deterioration, we assessed persons pre- and-post psychosis, comparing those who developed schizophrenia with those who did not. Twenty six patients with schizophrenia and 59 normal controls, evaluated at age 7 in the prospective, longitudinal, National Collaborative Perinatal Project (NCPP), were re-tested approximately 28 years later. We assessed change in an estimate of IQ based on the Vocabulary and Block Design tests from the Wechsler intelligence scales. Persons who later developed schizophrenia were significantly impaired on IQ compared to controls at age 7, especially on measures of attention. At age 35, persons with schizophrenia demonstrated significant impairment and deterioration on both IQ sub-tests compared to controls. Because impairment occurs by early childhood and subsequent deterioration occurs at an unknown period, designs with more frequent assessment of IQ through the premorbid, prodromal and early phases of illness are required to identify the key period of decline. Future research on this sample will evaluate the prospective roles of family history and perinatal complications on cognition, and assess the specificity of these findings.

DTNBP1 genotype influences cognitive decline in schizophrenia

OBJECTIVE

Intellectual decline is common in schizophrenia and predicts functional outcome. While many patients undergo intellectual decline that typically predates the onset of symptoms, few studies have investigated the underlying mechanism through which this occurs. The current study assessed the relationship between intellectual decline in schizophrenia and genetic variation in dysbindin-1 (DTNBP1).

METHODS

We assessed cognitive decline in 183 Caucasian patients with schizophrenia using a proxy measure of premorbid IQ with which current general cognitive ability (g) was compared. We then tested for a relationship between the risk haplotype identified in previous work (CTCTAC) and intellectual decline.

RESULTS

We found that carriers of the CTCTAC haplotype, demonstrated a significantly greater decline in IQ as compared with non-carriers (p=0.05).

CONCLUSIONS

These data suggest that DTNBP1 influences the severity of intellectual decline in schizophrenia and may represent one underlying cause for heterogeneity in cognitive course.

Distinguishing neurocognitive functions in schizophrenia using partially ordered classification models

Current methods for statistical analysis of neuropsychological test data in schizophrenia are inherently insufficient for revealing valid cognitive impairment profiles. While neuropsychological tests aim to selectively sample discrete cognitive domains, test performance often requires several cognitive operations or "attributes." Conventional statistical approaches assign each neuropsychological score of interest to a single attribute or "domain" (e.g., attention, executive, etc.), and scores are calculated for each. This can yield misleading information about underlying cognitive impairments. We report findings applying a new method for examining neuropsychological test data in schizophrenia, based on finite partially ordered sets (posets) as classification models. A total of 220 schizophrenia outpatients were administered the Positive and Negative Symptom Scale (PANSS) and a neuropsychological test battery. Selected tests were submitted to cognitive attribute analysis a priori by two neuropsychologists. Applying Bayesian classification methods (posets), each patient was classified with respect to proficiency on the underlying attributes, based upon his or her individual test performance pattern. Twelve cognitive "classes" are described in the sample. Resulting classification models provided detailed "diagnoses" into "attribute-based" profiles of cognitive strength/weakness, mimicking expert clinician judgment. Classification was efficient, requiring few measures to achieve accurate classification. Attributes were associated with PANSS factors in the expected manner (only the negative and cognition factors were associated with the attributes), and a double dissociation was observed in which divergent thinking was selectively associated with negative symptoms, possibly reflecting a manifestation of Kraepelin's hypothesis regarding the impact of volitional disturbances on thought. Using posets for extracting more precise cognitive information from neuropsychological data may reveal more valid cognitive endophenotypes, while dramatically reducing the amount of testing required.

Cognitive function and symptoms in adolescents with schizotypal personality disorder

Cognitive deficits have been documented in schizophrenia and spectrum disorders. This study examines cognitive functioning and its relation to symptoms in adolescents with schizotypal personality disorder (SPD). Participants are 89 adolescents recruited for a study of youth at risk for Axis I disorders, especially psychosis. At intake, 34 met criteria for SPD, 38 for another Axis II disorder and/or conduct disorder (Other disorder-OD), and 17 did not currently meet criteria for any DSM-IV disorder (normal control-NC). At initial assessment, cognitive functioning was measured using subtests from the Wechsler Intelligence Scales and Wechsler Memory Scales (WMS), and symptoms were measured using the Structured Interview for Prodromal Symptoms (SIPS). At the time of this report, 50 were readministered the SIPS at 1-year follow-up (T2). The SPD group scored significantly below the NC group on the Arithmetic subtest of the Wechsler Intelligence Scales, but there was only limited evidence of group differences on the WMS. Poorer performance on the Wechsler Intelligence Scales was associated with greater severity of negative and disorganized symptoms. Deficits on the WMS were linked with more severe disorganized symptoms. The findings reported here are consistent with previous reports of limited cognitive deficits in adolescents with SPD, with the most marked deficits in mental arithmetic. The associations between symptoms and cognitive scores parallel those observed in adults with schizophrenia and spectrum disorder, and they are consistent with the notion that negative symptoms are more stable and partially reflect premorbid cognitive functions.

Neuropsychological test profiles in schizophrenia and non-psychotic depression

OBJECTIVE

The study examined to what degree schizophrenia is characterized by a neuropsychological (NP) test profile specific in shape and level compared with depression and normal functioning.

METHOD

Fifty-three patients with schizophrenia, 45 with non-psychotic depression, and 50 normals were assessed with a comprehensive NP test battery and clinical instruments. NP test scores were factor analyzed into seven composite scores.

RESULTS

Schizophrenia patients performed significantly below normals across all seven composite scores, whereas depression patients were impaired in two. Verbal memory was most impaired. Sixty-two percent of schizophrenia patients were moderately or severely impaired, the corresponding figure for depression was 28%. Impairment was moderately associated with IQ level and clinical symptom load in schizophrenia, but not in depression.

CONCLUSION

Schizophrenia is characterized by deficits across a wide range of NP functions. Thirty-eight percent of the patients are within normal limits. A mild and limited NP disturbance is apparent in depression.

No, it is not possible to be schizophrenic yet neuropsychologically normal

Cognitive impairment is well documented in schizophrenia, though some reports have been interpreted to suggest that it is possible to have schizophrenia without neuropsychological impairment. The authors tested this by comparing the neuropsychological profiles of closely matched patients with schizophrenia and healthy comparison participants. Sixty-four patients with schizophrenia and 64 healthy comparison cases, matched to within 3 Full-Scale IQ points, were tested using the Wechsler Adult Intelligence Scale (3rd ed.; D. Wechsler, 1997b) and the Wechsler Memory Scale (3rd ed.; D. Wechsler, 1997c). Neuropsychological profiles for these groups were markedly different, with the group of patients with schizophrenia exhibiting performance deficits in memory and speeded visual processing but superior verbal comprehension and perceptual organization relative to the group of healthy comparison participants matched on Full-Scale IQ. Thus, scoring in the normal range does not preclude neuropsychological abnormality in schizophrenia, confirming that neuropsychological impairment is a core feature of the illness.

Neuropsychological profile of cognitively impaired patients with schizophrenia

OBJECTIVE

Our purpose in undertaking the present study was to explore the existence of specific areas of cognitive deficits within the context of generalized poor performance in a group of Greek patients with schizophrenia. We also sought to identify any patients who might be cognitively normal.

METHOD

Participants were 70 patients with schizophrenia and 42 healthy control subjects. The 2 groups were matched on age and male-female ratio but differed in their level of education. A battery of neuropsychological tests was selected to assess executive functions/abstraction, fluency, verbal and spatial working memory, verbal and nonverbal memory, attention, visuospatial ability, and psychomotor speed.

RESULTS

Patients with schizophrenia performed more poorly than healthy control subjects, when we controlled for differences in level of education, on executive functions, working memory, verbal memory, nonverbal memory, fluency, visuospatial ability, and attention. In contrast, no significant differences were found between the 2 groups on psychomotor speed. Patients showed a more pronounced deficit on executive functions, verbal and visual memory, and visuospatial ability. Overall, 13% to 62% of the patients with schizophrenia scored within 1 SD of the mean z scores of healthy control group depending on the cognitive domains examined. In the entire sample of patients with schizophrenia, however, no individual scored within 1 SD of the mean z scores of the control group in all cognitive domains.

CONCLUSIONS

We found a generalized deficit in cognitive functioning in a group of patients with schizophrenia. We failed to find any individual patients who were healthy across all cognitive areas. The current neuropsychological profile, indicating widespread impairment, is comparable to that reported in the international literature and thus appears to be characteristic of schizophrenia. Our findings of increased difficulties with executive functions, verbal and visual memory, and visuospatial ability support previous suggestions of generalized brain dysfunction in the pathophysiology of schizophrenia.

Cognitive heterogeneity in first-episode schizophrenia

BACKGROUND

Studies of chronic schizophrenia suggest that there are subgroups with different profiles of cognitive impairment.

AIMS

To determine whether such heterogeneity is present at illness onset and any relationship to clinical variables.

METHOD

Ninety-three community patients with first-episode schizophrenia and 50 healthy volunteers were assessed for premorbid (Revised National Adult Reading Test) and current IQ, memory and executive function.

RESULTS

Half of those with schizophrenia had preserved IQ in the normal range but there was evidence of a specific impairment in spatial working memory even in those with high/average IQ; 37 out of 93 (40%) had generalised cognitive decline. Those with low premorbid IQ were significantly younger at illness onset. For the entire group, age at onset correlated positively with premorbid but not current IQ.

CONCLUSIONS

At illness onset, cognitive heterogeneity is present in people with schizophrenia, with a high proportion having undergone general cognitive decline. However, working memory impairment may be a common feature. Lower premorbid IQ is a risk factor for an earlier onset.