Stroop interference and facilitation effects in first-episode schizophrenic patients

Pentoxifylline as adjunctive therapy in cognitive deficits and symptoms of schizophrenia: A randomized double-blind placebo-controlled clinical trial

BACKGROUND

Due to the inflammatory factors in the pathophysiology of schizophrenia, Pentoxifylline, as anti-inflammatory medication, seems to improve the symptoms of schizophrenia. This study aims to evaluate the efficacy of Pentoxifylline as an adjunctive therapy on cognitive deficits and symptoms of schizophrenia.

METHODS

This randomized double-blind placebo-controlled clinical trial was conducted on 52 patients diagnosed with chronic schizophrenia. All patients were divided into two, treatment and control groups. They received a 400 mg dose of Pentoxifylline and the placebo in the treatment and control groups, respectively, twice a day for 8 weeks. Then, they were tested with the Positive and Negative Syndrome Scale (PANSS), Wisconsin Card Sorting Test (WCST), digit span, Stroop test, and Rey Auditory and Verbal Learning Test at baseline and the end of the weeks 4 and 8. Data analysis was done by Kolmogorov-Smirnov test, t-test, Mann-Whitney test, chi-square test, and generalized estimating equation model.

RESULTS

After analyzing the data, it was revealed that the positive symptoms of PANSS, the number of errors in the incongruent Stroop test, and reaction time in the congruent Stroop test were significantly lower in the treatment group (p < 0.05). Moreover, the number of categories of WCST was significantly higher in the treatment group (p < 0.05). There was no statistically significant difference in other parameters between the control and treatment groups (p > 0.05).

CONCLUSIONS

As evidenced by the results of this study, Pentoxifylline can help alleviate schizophrenia cognitive deficits and can reduce psychotic symptoms. Therefore, it can potentially be useful for schizophrenia treatment.

Cognitive [Computational] Neuroscience Test Reliability and Clinical Applications for Serious Mental Illness (CNTRaCS) Consortium: Progress and Future Directions

The development of treatments for impaired cognition in schizophrenia has been characterized as the most important challenge facing psychiatry at the beginning of the twenty-first century. The Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) project was designed to build on the potential benefits of using tasks and tools from cognitive neuroscience to better understanding and treat cognitive impairments in psychosis. These benefits include: (1) the use of fine-grained tasks that measure discrete cognitive processes; (2) the ability to design tasks that distinguish between specific cognitive domain deficits and poor performance due to generalized deficits resulting from sedation, low motivation, poor test taking skills, etc.; and (3) the ability to link cognitive deficits to specific neural systems, using animal models, neuropsychology, and functional imaging. CNTRICS convened a series of meetings to identify paradigms from cognitive neuroscience that maximize these benefits and identified the steps need for translation into use in clinical populations. The Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia (CNTRaCS) Consortium was developed to help carry out these steps. CNTRaCS consists of investigators at five different sites across the country with diverse expertise relevant to a wide range of the cognitive systems identified as critical as part of CNTRICs. This work reports on the progress and current directions in the evaluation and optimization carried out by CNTRaCS of the tasks identified as part of the original CNTRICs process, as well as subsequent extensions into the Positive Valence systems domain of Research Domain Criteria (RDoC). We also describe the current focus of CNTRaCS, which involves taking a computational psychiatry approach to measuring cognitive and motivational function across the spectrum of psychosis. Specifically, the current iteration of CNTRaCS is using computational modeling to isolate parameters reflecting potentially more specific cognitive and visual processes that may provide greater interpretability in understanding shared and distinct impairments across psychiatric disorders.

The MIR137 VNTR rs58335419 Is Associated With Cognitive Impairment in Schizophrenia and Altered Cortical Morphology

Genome-wide association studies (GWAS) of schizophrenia have strongly implicated a risk locus in close proximity to the gene for miR-137. While there are candidate single-nucleotide polymorphisms (SNPs) with functional implications for the microRNA's expression encompassed by the common haplotype tagged by rs1625579, there are likely to be others, such as the variable number tandem repeat (VNTR) variant rs58335419, that have no proxy on the SNP genotyping platforms used in GWAS to date. Using whole-genome sequencing data from schizophrenia patients (n = 299) and healthy controls (n = 131), we observed that the MIR137 4-repeats VNTR (VNTR4) variant was enriched in a cognitive deficit subtype of schizophrenia and associated with altered brain morphology, including thicker left inferior temporal gyrus and deeper right postcentral sulcus. These findings suggest that the MIR137 VNTR4 may impact neuroanatomical development that may, in turn, influence the expression of more severe cognitive symptoms in patients with schizophrenia.

Neuropsychological Decomposing Stroop Interference Into Different Cognitive Monitoring: An Exploratory Factor Analysis

INTRODUCTION

There are two alternative explanations of the Stroop phenomenon. Several studies have revealed that the difference in performance on congruent and incongruent trials can arise from response interference. On the contrary, many authors have claimed that Stroop interference might occur at earlier processing stages related to semantic or conceptual encoding. The present study aims to determine the number and nature of the factors necessary to account for the multiple components of Stroop interference.

METHODS

The sample consisted of 247 undergraduate and postgraduate students. We employed the computerized version of the Stroop task adapted to the Iranian population. An exploratory principal components analysis was conducted on the correlations of 6 variables (reaction time under congruent and incongruent conditions, omission error under congruent and incongruent conditions, and commission error under congruent and incongruent conditions).

RESULTS

Two factors were extracted. The first factor may be semantic interference, and the second factor may be response interference.

CONCLUSION

The findings of this research are consistent with the multiple-stage account, claiming that Stroop interference is because of both semantic and response interferences.

Neural and neuronal discoordination in schizophrenia: From ensembles through networks to symptoms

Despite the substantial knowledge accumulated by past research, the exact mechanisms of the pathogenesis of schizophrenia and causal treatments still remain unclear. Deficits of cognition and information processing in schizophrenia are today often viewed as the primary and core symptoms of this devastating disorder. These deficits likely result from disruptions in the coordination of neuronal and neural activity. The aim of this review is to bring together convergent evidence of discoordinated brain circuits in schizophrenia at multiple levels of resolution, ranging from principal cells and interneurons, neuronal ensembles and local circuits, to large-scale brain networks. We show how these aberrations could underlie deficits in cognitive control and other higher order cognitive-behavioural functions. Converging evidence from both animal models and patients with schizophrenia is presented in an effort to gain insight into common features of deficits in the brain information processing in this disorder, marked by disruption of several neurotransmitter and signalling systems and severe behavioural outcomes.

Duration of untreated psychosis and neurocognitive functioning in first-episode psychosis: a systematic review and meta-analysis

BACKGROUND

Previous reviews suggest there is minimal evidence for an association between duration of untreated psychosis (DUP) and neurocognition. This is based on tallied findings of studies with small samples and neurocognition viewed as a single construct. We aimed to conduct a systematic review and meta-analysis examining the association between DUP and individual neurocognitive domains and tests in first-episode psychosis (FEP).

METHOD

MOOSE and PRISMA guidelines were followed. Forty-three studies involving 4647 FEP patients were included. For studies providing correlations between DUP and neurocognition, 12 separate meta-analyses were performed based on neurocognitive domains/indices. The influence of demographic/clinical variables was tested using weighted linear meta-regression analyses.

RESULTS

The relationship between DUP and most neurocognitive domains/indices was not significant. Longer DUP was associated with a larger cognitive deterioration index, i.e. current minus premorbid intellectual functioning (N = 4; mean ES -0.213, 95% confidence interval (CI) (-0.344 to -0.074), p = 0.003). Findings were homogeneous, with no evidence of publication bias or significant influence from moderators. For studies providing mean and standard deviations for neurocognitive measures and DUP, 20 meta-regressions were performed on individual neurocognitive tests. One significant finding emerged showing that longer DUP was associated with fewer Wisconsin Card Sorting Test-perseverative errors (mean ES -0.031, 95% CI (-0.048 to -0.013), p < 0.001). Exploratory meta-regressions in studies with mean DUP <360 days showed longer DUP was significantly associated with poorer performance on Trail Making Test A and B and higher Full-Scale IQ.

CONCLUSION

There may not be a generalised association between DUP and neurocognition, however, specific cognitive functions may be associated with longer DUP or delayed help-seeking.

Neurophysiological Evidence of Compensatory Brain Mechanisms Underlying Attentional-Related Processes in Symptomatically Remitted Patients with Schizophrenia

A recent electrophysiological study suggests existing compensatory brain activity as a mechanism for functional recovery of visual attention detection (the capacity for detecting external cues) in symptomatically remitted schizophrenia patients. Despite such evidence, little is known about other aspects of attentional-related processes in schizophrenia during clinical remission, such as their capacity to concentrate on the task at hands without being interfered by distracting information. To this end, we recorded event-related brain potentials (ERPs) from 20 symptomatically remitted schizophrenia patients and 20 healthy controls while they engaged in a classic Stroop task. Symptomatically remitted patients showed comparable Stroop interference to healthy controls, indicating a degree of functional recovery of such a capacity in these patients. On the neural level, the N450 over the fronto-central and central regions, a component of the ERPs related to conflict detection, was found across both groups, although patients presented a reduced N450 relative to healthy controls. By contrast, the amplitude of the sustained potential (SP) (600-800 ms) over the parieto-central and parietal regions, a component of the ERPs related to conflict resolution, was significantly increased in patients relative to healthy controls. Furthermore, such increased SP amplitude correlated positively with improved behavioral accuracy in symptomatically remitted patients with schizophrenia. These findings reveal that symptomatically remitted patients with schizophrenia increasingly recruited the parietal activity involving successful conflict resolution to offset reduced conflict detection. Therefore, this provides further insight into compensatory mechanisms potentially involving a degree of functional recovery of attentional-related processes in schizophrenia during clinical remission.

What Stroop tasks can tell us about selective attention from childhood to adulthood

A rich body of research concerns causes of Stroop effects plus applications of Stroop. However, several questions remain. We included assessment of errors with children and adults (N = 316), who sat either a task wherein each block employed only trials of one type (unmixed task) or where every block comprised of a mix of the congruent, neutral, and incongruent trials. Children responded slower than adults and made more errors on each task. Contrary to some previous studies, interference (the difference between neutral and incongruent condition) showed no reaction time (RT) differences by group or task, although there were differences in errors. By contrast, facilitation (the difference between neutral and congruent condition) was greater in children than adults, and greater on the unmixed task than the mixed task. After considering a number of theoretical accounts, we settle on the inadvertent word‐reading hypothesis, whereby facilitation stems from children and the unmixed task promoting inadvertent reading particularly in the congruent condition. Stability of interference RT is explained by fixed semantic differences between neutral and incongruent conditions, for children versus adults and for unmixed versus mixed task. We conclude that utilizing two tasks together may reveal more about how attention is affected in other groups.

Are Hallucinations Due to an Imbalance Between Excitatory and Inhibitory Influences on the Brain?

This review from the International Consortium on Hallucinations Research intends to question the pertinence of the excitatory-to-inhibitory (E/I) imbalance hypothesis as a model for hallucinations. A large number of studies suggest that subtle impairments of the E/I balance are involved in neurological and psychiatric conditions, such as schizophrenia. Emerging evidence also points to a role of the E/I balance in maintaining stable perceptual representations, suggesting it may be a plausible model for hallucinations. In support, hallucinations have been linked to inhibitory deficits as shown with impairment of gamma-aminobutyric acid transmission, N-methyl-d-aspartate receptor plasticity, reductions in gamma-frequency oscillations, hyperactivity in sensory cortices, and cognitive inhibition deficits. However, the mechanisms by which E/I dysfunctions at the cellular level might relate to clinical symptoms and cognitive deficits remain unclear. Given recent data advances in the field of clinical neuroscience, it is now possible to conduct a synthesis of available data specifically related to hallucinations. These findings are integrated with the latest computational frameworks of hallucinations, and recommendations for future research are provided.

A functional variant in MIR137, a candidate gene for schizophrenia, affects Stroop test performance in young adults

MIR137, a brain expressed miRNA, has been identified as a top novel susceptibility gene for schizophrenia (SZ). 230 healthy participants completed the Stroop test and were genotyped for a functional Variable Number Tandem Repeat (VNTR) in MIR137 gene. MIR137 VNTR genotypes were associated with differences in Stroop facilitation and accuracies in congruent trials and for the total number of errors. This is the first study of the functional VNTR in MIR137 gene and Stroop test performance in healthy subjects. Our results could have important implications for the identification of genetic candidates for endophenotypes for SZ.

Do psychosis patients with poor insight show implicit awareness on the emotional stroop task?

BACKGROUND

The insight into psychosis can be assessed reliably by clinicians from interviews with patients. However, patients may retain implicit awareness of illness while lacking explicit awareness.

SAMPLING AND METHODS

In a sample of first-episode psychosis patients, we used a test of processing of mental illness-related and other negative words as a measure of implicit awareness to see how this varied in relation to insight. An emotional-counting Stroop task tested reaction times to words of three types: psychosis-related (e.g. 'crazy'), general negative (e.g. 'cancer') and neutral (e.g. 'oyster'). Data were available from 43 patients and 23 healthy controls. Patients' insight was assessed using the Schedule for the Assessment of Insight (SAI-E).

RESULTS

Patients reacted slower than controls to words across all conditions, and both patients and controls reacted slower to salient and negative words than neutral words. There was a near significant interaction between word type and group (Wilks' lambda = 0.53, p = 0.055); patients experienced greater interference from negative rather than psychosis-related words (p = 0.003), and controls experienced greater interference from salient rather than negative words (p = 0.01). Within the patient group, there was a correlation between insight and interference on salient words (r = 0.33, p = 0.05), such that those with less insight experienced less interference on psychosis-related words.

CONCLUSIONS

Psychosis-related words were less threatening and less self-relevant to psychosis patients with less insight. This suggests that the lack of awareness such patients have of their illness is genuine and more likely to be mediated by lower-level information processing mechanisms than strategies such as conscious, motivated denial.

Inflexible minds: impaired attention switching in recent-onset schizophrenia

Impairment of sustained attention is assumed to be a core cognitive abnormality in schizophrenia. However, this seems inconsistent with a recent hypothesis that in schizophrenia the implementation of selection (i.e., sustained attention) is intact but the control of selection (i.e., switching the focus of attention) is impaired. Mounting evidence supports this hypothesis, indicating that switching of attention is a bigger problem in schizophrenia than maintaining the focus of attention. To shed more light on this hypothesis, we tested whether schizophrenia patients are impaired relative to controls in sustaining attention, switching attention, or both. Fifteen patients with recent-onset schizophrenia and fifteen healthy volunteers, matched on age and intelligence, performed sustained attention and attention switching tasks, while performance and brain potential measures of selective attention were recorded. In the sustained attention task, patients did not differ from the controls on these measures. In the attention switching task, however, patients showed worse performance than the controls, and early selective attention related brain potentials were absent in the patients while clearly present in the controls. These findings support the hypothesis that schizophrenia is associated with an impairment of the mechanisms that control the direction of attention (attention switching), while the mechanisms that implement a direction of attention (sustained attention) are intact.

Impaired cognitive inhibition in schizophrenia: a meta-analysis of the Stroop interference effect

Schizophrenia has been consistently shown to be associated with impairment in executive functioning. However, although frequently treated as such, the term executive functioning does not refer to a unitary cognitive function; it rather represents a set of basic, lower-level cognitive sub-components, e.g. updating, shifting, and cognitive inhibition. This specification into sub-components allows for a further differentiation of the executive deficits found in schizophrenia. Focusing on the sub-component of cognitive inhibition, we here present a meta-analysis of interference effect as assessed with the Stroop Color-Word Interference paradigm. Including the results of 36 studies with 1081 schizophrenia patients and 1026 healthy control subjects, it was shown that schizophrenia patients exhibit an increased Stroop interference effect both in response time (mean effect size: M(g) = 0.43; 95% confidence interval, CI95%: 0.35-0.52) and accuracy (M(g) = 0.62; CI95%: 0.47-0.77) measures of interference. However, a meta-regression analysis revealed that the size of the effect varies depending on the version of the Stroop paradigm used. Regarding the response time measures of interference, studies using the classical card version of the paradigm showed a significantly larger effect size than studies using a single-trial computerized version of the paradigm (M(g) = 0.60 vs. M(g) = 0.19). Despite of the dissociation between the two versions of the paradigm, the results of the present meta-analysis indicate that the reported global deficits in executive functioning found to be associated with schizophrenia are at least partly due to a reduced ability of cognitive inhibition.

Overlapping cognitive patterns in schizophrenia and methamphetamine dependence

OBJECTIVE

To examine whether overlapping cognitive deficits exist in currently drug-abstinent chronic methamphetamine (MA) abusers and schizophrenia (SZ) patients.

BACKGROUND

Both SZ and chronic MA abuse are associated with frontostriatal disruption as well as deficits in cognitive control, such as selective attention. To identify overlapping cognitive profiles, we compared performance of the 2 groups on the Stroop attention task.

METHODS

Data were analyzed from 69 MA abusers who had been MA-abstinent for differing periods of time and from 23 SZ patients and 38 non-substance-abusing controls.

RESULTS

The MA abusers in early abstinence displayed more Stroop interference than the SZ patients (P=0.004), long-term abstinent MA abusers (P=0.009), and controls (P=0.002). In the MA abusers, the magnitude of Stroop interference correlated positively with longer drug use (P=0.01) and negatively with longer drug abstinence (P=0.04). No correlations were found between psychotic symptoms and task performance.

CONCLUSIONS

On this task of attentional selection, only the MA abusers in early stages of abstinence showed performance deficits compared with controls. More research is needed to further elucidate overlapping patterns between MA abuse and SZ.

Performance of schizophrenic patients in the Stroop Color Word Test and electrodermal responsiveness after acute administration of cannabidiol (CBD)

OBJECTIVE

The last decade has seen increasing evidence of dysfunctions in the endogenous cannabinoid system in schizophrenia and of its relationship with the typical cognitive impairment of the disorder. Studies in animal models, healthy volunteers, and psychotic patients clearly suggest an antipsychotic-like effect of cannabidiol. This study investigated the effects of cannabidiol on selective attention in 28 schizophrenic patients using the Stroop Color Word Test and on these patients' electrodermal responsiveness to auditive stimuli.

METHOD

The subjects attended two experimental sessions, the first one without the administration of drugs. In the second session the subjects were divided into three groups that received either a single dose of cannabidiol 300 mg or cannabidiol 600 mg or placebo.

RESULTS

The three groups did not differ significantly with respect to electrodermal measures in the two experimental sessions. When the first and second sessions were compared improved performance was found in all three groups, with patients who received placebo and cannabidiol 300 mg performing better than those who received cannabidiol 600 mg.

CONCLUSION

The single, acute administration of cannabidiol seems to have no beneficial effects on the performance of schizophrenic patients in the Stroop Color Word Test, although the hypothesis that chronic administration may lead to improvement cannot be disregarded.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The cognitive neuroscience of working memory: relevance to CNTRICS and schizophrenia

Working memory is one of the central constructs in cognitive science and has received enormous attention in the theoretical and empirical literature. Similarly, working memory deficits have long been thought to be among the core cognitive deficits in schizophrenia, making it a ripe area for translation. This article provides a brief overview of the current theories and data on the psychological and neural mechanisms involved in working memory, which is a summary of the presentation and discussion on working memory that occurred at the first Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) meeting (Washington, D.C.). At this meeting, the consensus was that the constructs of goal maintenance and interference control were the most ready to be pursued as part of a translational cognitive neuroscience effort at future CNTRICS meetings. The constructs of long-term memory reactivation, capacity, and strategic encoding were felt to be of great clinical interest but requiring more basic research. In addition, the group felt that the constructs of maintenance over time and updating in working memory had growing construct validity at the psychological and neural levels but required more research in schizophrenia before these should be considered as targets for a clinical trials setting.

A family history of psychopathology modifies the decrement in cognitive control among patients with HIV/AIDS

The present study was designed to evaluate the effect of HIV/AIDS on cognitive control and to determine if the effect is modified by familial risk for either alcohol or mood disorders. Sixty HIV-1 seropositive and 75 seronegative volunteers were assigned to four subgroups defined by the crossing of a diagnosis of alcohol dependence in the biological father with diagnoses of either major depressive disorder or bipolar disorder in the biological mother. Cognitive control was evaluated during a task in which subjects were asked, on occasion, to inhibit the impulse to respond in the same physical direction as the stimulus and instead respond in the opposite direction. Event related brain potentials and measures of task performance were recorded. The task evoked a negative shift in a late slow potential (SP) as well as an increment in reaction time when cognitive control was challenged. An important finding was an interaction between trial type, HIV/AIDS, and family history: HIV/AIDS and family history each attenuated the negative shift in the SP to such a degree that no further attenuation could be accomplished by the other. The effects of familial risk for alcohol versus mood disorders were equivalent. In conclusion, the absence of change in a late slow potential following a challenge to cognitive control may represent a marker of familial risk for both externalizing and internalizing disorders. The effects of familial risk on this slow potential are sufficiently robust as to attenuate the effects of HIV/AIDS on the probable generators of the response: the anterior cingulate and prefrontal cortex.

Acute serotonin and dopamine depletion improves attentional control: findings from the stroop task

Schizophrenia is associated with impairments of attentional control on classic experimental paradigms such as the Stroop task. However, at a basic level the neurochemical mechanisms that may be responsible for such impairments are poorly understood. In this study, we sought to investigate the influence of brain monoamine function on Stroop task performance in healthy participants using the established methods of acute dietary serotonin, dopamine, and combined monoamine depletion. The study was a double-blind placebo controlled design in which 12 healthy male participants completed the Stroop task under four acute treatment conditions: (a) balanced/placebo control, (b) acute tryptophan depletion, (c) acute tyrosine/phenylalanine depletion, and (d) acute tyrosine/phenylalanine/tryptophan depletion (combined monoamine depletion). Decreased Stroop interference indicating improved attentional control was observed after both tryptophan depletion and tyrosine/phenylalanine depletion, while there was no significant change in interference after combined monoamine depletion. Findings suggest that reduced tonic dopamine or serotonin activity within specific neural circuits (such as the striatum, anterior cingulate, or prefrontal cortex) may play a critical role in attentional control, possibly by improving gating of information via reducing noise in monoaminergic systems. These findings enhance our understanding of the neurochemical basis of attentional control and the possible cause of attentional control deficits in schizophrenia.

Shared cognitive processes underlying performance on the Wisconsin Card Sorting Test and the Stroop Test in patients with schizophrenia: a measurement artifact?

We explored the hypothesis that, while sensitive to different aspects of executive functioning in patients with schizophrenia, the Wisconsin Card Sorting Test (WCST) and the Stroop Test also measure the same construct, namely, inhibitory control. Specifically, our goal was to confirm and extend previous findings [A. Rossi, E. Daneluzzo, P. Mattei, M. Bustini, M. Cassachia, P. Stratta, Wisconsin Card Sorting Test and Stroop performance in schizophrenia: a shared construct, Neurosci. Lett. 226 (1997) 87-90] by demonstrating the independence of this construct from other abilities necessary to successfully perform the tasks. More importantly, we sought to improve on this previous study by eliminating the influence of the variance of speed of responding. We examined 55 patients with schizophrenia and initially found that performance on the Stroop Color-Word condition could, indeed, be predicted only by the percentage of perseverative errors on the WCST, and not variables reflective of other cognitive skills, thus replicating and extending previous findings. Once we removed the influence of speed of responding from our measure, however, thus isolating the inhibitory process, this finding disappeared. Therefore, our findings highlight the importance of isolating the individual components of interest from complex measures before drawing conclusions regarding the cognitive processes underlying particular test performance.

Depression, suicidal behavior and insight in adolescents with schizophrenia

OBJECTIVES

To investigate the interrelationships between depressive symptoms of adolescent schizophrenia, post-psychotic depression (PPD), negative signs, suicidal behavior and insights into the disease.

METHODS

Three groups of 16 adolescent inpatients were assessed with regard to: Schizophrenia alone, schizophrenia with PPD and major depressive disorder (MDD). The following measures were used: DSM IV diagnostic criteria, the Calgary Depression Scale for Schizophrenia (CDSS), the PANSS (Positive and Negative Signs of Schizophrenia Scale), (BDI) Beck Depression Inventory, (CCL) Cognitive Check List, (HS) Hopelessness Scale, (SRS) Suicide Risk Scale, (CSPS) Child Suicide Potential Scale and the (SAUMD) Scale to Assess Unawareness of Mental Disorder.

RESULTS

Compared with MDD adolescents, PPD adolescents showed few somatic and behavioral symptoms of depression but had equally severe cognitive and affective depressive symptomatology. Suicide risk scores and actual suicidal behavior was prominent in PPD adolescents. A positive and significant correlation was found between PPD symptoms, suicide risk and awareness of disease (insight). Negative symptoms of schizophrenia could be distinguished from PPD symptoms and there was a negative correlation between blunted affect and PPD scores.

CONCLUSIONS

PPD can be diagnosed in adolescent schizophrenia. The symptom pattern is different from MDD, therefore, there may be cause to modify DSM IV provisional criteria for this condition. Adolescents with schizophrenia who have insight into their illness are at higher risk for suicidal behavior and the development of PPD.

Cognitive functioning in the early course of first-episode schizophrenia spectrum disorders: timing and patterns

OBJECTIVE

The aim of this study was to examine possible cognitive changes throughout the early course of schizophrenia spectrum disorders.

METHOD

Forty-two patients, aged 15-50 years, admitted to a first episode psychosis program (PAFIP) serving to the community of Cantabria (Spain) and 43 healthy volunteers completed a brief battery of five neurocognitive tests at four time-points over 3 months. The cognitive testing comprise five domains: attention, visuomotor speed, declarative memory, working memory and executive function. Baseline assessment occurred within 72 hour after the initiation of standard pharmacological treatment, and after then parallel forms of the tests were applied at week-2, week-6, and month-3.

RESULTS

Patient scores showed a significant impairment compared to healthy volunteers in the five cognitive domains at baseline and week-2 assessments. After the first 3 months of antipsychotic treatment, the patient group performance reached healthy volunteers level on executive function (Stroop interference) and immediate verbal memory tests. In contrast, performance on working memory, sustained attention, visuomotor speed, and verbal memory delayed recall domains still remained below healthy volunteers, although visuomotor processing speed showed a significant improvement.

CONCLUSION

Schizophrenia spectrum patients show heterogeneous patterns and degrees of cognitive changes that contribute to stress the importance of when, what, and how neurocognitive functioning in the early phases of the illness is evaluated.

Amphetamine improves cognitive function in medicated individuals with schizophrenia and in healthy volunteers

BACKGROUND

Recent research on schizophrenia indicates that cognitive deficits in this illness are important predictors of functional outcome, highlighting the need for treatments that have a positive impact on cognitive function. Here we explore the hypothesis that acute administration of d-amphetamine can improve cognitive function in individuals with schizophrenia who are well-treated with typical antipsychotics, as well as in healthy controls performing under dual task conditions designed to elicit performance deficits analogous to those found in schizophrenia.

METHODS

Ten individuals with schizophrenia taking haldol or prolixin and 22 healthy controls performed spatial working memory, language production, and Stroop tasks under both placebo and 0.25 mg/kg of D-amphetamine.

RESULTS

D-Amphetamine improved reactions times on the spatial working memory and Stroop tasks for both individuals with schizophrenia and controls, and improved working memory accuracy in schizophrenia. In addition, D-amphetamine improved language production for both individuals with schizophrenia and controls.

CONCLUSIONS

These results provide support for the hypothesis that the adjunctive administration of dopamine agonist can improve cognitive in individuals with schizophrenia taking typical antipsychotics. The results are discussed in terms of their implications for understanding the nature of working memory deficits in schizophrenia, and potential future avenues for cognitive enhancement in this illness.

Factors influencing Stroop performance in schizophrenia

Recent studies suggest that individuals with schizophrenia show enhanced facilitation but similar interference in reaction times (RTs), compared with control participants, combined with increased error interference. This study examined the relationship between errors and RTs on the Stroop task among individuals with schizophrenia. The authors examined performance on a speeded Stroop task, designed to increase errors, in 29 individuals with schizophrenia and 29 nonpatient control participants. The authors also analyzed color-naming and word-reading estimates from process dissociation analyses. The findings suggest that a lack of increased RT interference among patients (compared with control participants) is not solely due to the increased number of errors they produce in the incongruent condition but is also influenced by a greater impact of the word even in the neutral condition.

Schizophrenia and the stroop effect

Conflict between irrelevant words and relevant colors in the Stroop task creates interference, long considered a measure of how well individuals focus attention. In the traditional card version of the Stroop task, schizophrenia patients exhibit increased interference, consistent with the distractibility they exhibit in everyday life. In contrast, on other versions of the Stroop task they show augmented facilitation (faster responding to congruent than to neutral trials). We suggest that schizophrenia patients possess adequate attentional resources to avoid interference when each letter string is presented individually but face difficulty when delays are imposed and multiple attentional demands appear. Although psychiatric symptomatology may contribute to different patterns of performance, there is no evidence that medication modulates this.

Conscious and subliminal conflicts in normal subjects and patients with schizophrenia: the role of the anterior cingulate

The human anterior cingulate cortex (ACC), which is active during conflict-monitoring tasks, is thought to participate with prefrontal cortices in a distributed network for conscious self-regulation. This hypothesis predicts that conflict-related ACC activation should occur only when the conflicting stimuli are consciously perceived. To dissociate conflict from consciousness, we measured the behavioral and brain imaging correlates of a motor conflict induced by task-irrelevant subliminal or conscious primes. The same task was studied in normal subjects and in patients with schizophrenia in whom the ACC and prefrontal cortex are thought to be dysfunctional. Conscious, but not subliminal, conflict affected anterior cingulate activity in normal subjects. Furthermore, patients with schizophrenia, who exhibited a hypoactivation of the ACC and other frontal, temporal, hippocampal, and striatal sites, showed impaired conscious priming but normal subliminal priming. Those findings suggest that subliminal conflicts are resolved without ACC contribution and that the ACC participates in a distributed conscious control network that is altered in schizophrenia.

Neurophysiological Evidence for Disturbances of Conflict Processing in Patients With Schizophrenia

Deficits in cognition are a hallmark of schizophrenia. In the present study, the authors investigated the effects of schizophrenia on the neural correlates of conflict processing in a single-trial version of the Stroop task by using event-related brain potentials. Relative to matched controls, patients with schizophrenia showed increased Stroop interference in response time, but this effect was eliminated when the effect of response slowing was controlled. In controls, conflict processing was associated with a negative wave peaking between 400 and 500 ms (N450) and conflict sustained potential (SP) peaking between 600 and 800 ms after stimulus onset. In patients with schizophrenia, the amplitude of the N450 was significantly attenuated and the conflict SP was absent. These results provide evidence for the existence of altered neural processes associated with conflict processing that may be associated with dysfunction of the anterior cingulate and prefrontal cortex in patients with schizophrenia.