Working Memory Performance in Poor Outcome Schizophrenia: Relationship to Age and Executive Functioning

Mechanisms underlying dorsolateral prefrontal cortex contributions to cognitive dysfunction in schizophrenia

Kraepelin, in his early descriptions of schizophrenia (SZ), characterized the illness as having "an orchestra without a conductor." Kraepelin further speculated that this "conductor" was situated in the frontal lobes. Findings from multiple studies over the following decades have clearly implicated pathology of the dorsolateral prefrontal cortex (DLPFC) as playing a central role in the pathophysiology of SZ, particularly with regard to key cognitive features such as deficits in working memory and cognitive control. Following an overview of the cognitive mechanisms associated with DLPFC function and how they are altered in SZ, we review evidence from an array of neuroscientific approaches addressing how these cognitive impairments may reflect the underlying pathophysiology of the illness. Specifically, we present evidence suggesting that alterations of the DLPFC in SZ are evident across a range of spatial and temporal resolutions: from its cellular and molecular architecture, to its gross structural and functional integrity, and from millisecond to longer timescales. We then present an integrative model based upon how microscale changes in neuronal signaling in the DLPFC can influence synchronized patterns of neural activity to produce macrocircuit-level alterations in DLPFC activation that ultimately influence cognition and behavior. We conclude with a discussion of initial efforts aimed at targeting DLPFC function in SZ, the clinical implications of those efforts, and potential avenues for future development.

General description of cognitive deficits in schizophrenia and assessment tools in Lebanon: A scoping review

Many cognitive functions are affected in schizophrenia patients, particularly memory, attention, motor skills, executive function, and social cognition. Cognitive assessment is one of the best indicators of the functional and social prognosis of schizophrenic patients. In Lebanon, no study has yet examined the assessment of cognitive functions in patients with neurological or psychiatric diseases. This review aims to provide an overview of the cognitive profiles of schizophrenia and describe the different cognitive tests used in Lebanon. The MEDLINE/PubMed database was used to conduct a literature review covering all studies related to cognition in psychosis patients from 1990 until March 2021. This screening resulted in 97 articles focused on cognition in psychiatric patients or cognitive tests in schizophrenia and required an in-depth analysis. The majority of measures developed to evaluate cognition in patients with schizophrenia were from Western countries, most of which are long and complex and may require several hours to administer. The number of neuropsychological tests available in Arab countries is unknown, although it is likely to be limited compared to what is available in Western countries. In Lebanon, some neuropsychological batteries have been locally used to assess cognition without being translated and validated to be adapted to the Lebanese sociocultural context. Clinicians in Lebanon underestimate the extent of cognitive impairment in schizophrenia patients as they have limited options, using untranslated tests or using translations that have not been validated. Future studies should target the development and adaptation of instruments that predict and measure cognition and functional ability.

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Many cognitive functions are generally impaired in patients with schizophrenia

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The number of neuropsychological tests available in Arab countries is unknown

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In Lebanon, some neuropsychological batteries have been used to assess cognition without being translated and validated

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Few studies conducted in Lebanon have used neurocognitive tests among schizophrenia.

Social Perception Predicts Awareness of Illness in Persons With Schizophrenia

Lack of clinical insight in patients with schizophrenia is an obstacle to optimal treatment. Social cognition is one of several variables central to insight deficits in schizophrenia. The aim of this study was to investigate clinical insight in relation to one domain of social cognition, social perception, while controlling for effects of nonsocial cognition and symptom severity. Clinical insight was measured in 55 patients with schizophrenia or schizoaffective disorder, using the Birchwood Insight Scale. Relationships across domains were used to assess social perception. Social perception predicted one of three subscales of clinical insight, "awareness of illness," and was the only unique contributor to this subscale. This indicates that social perception is linked to clinical insight through awareness of illness. More research is needed to fully understand the relationship between social and nonsocial cognition and symptoms in relation to clinical insight.

Dysfunction of Magnocellular/dorsal Processing Stream in Schizophrenia

Background:

Patients with schizophrenia show not only cognitive, but also perceptual deficits. Perceptual deficits may affect different sensory modalities. Among these, the impairment of visual information processing is of particular relevance as demonstrated by the high incidence of visual disturbances. In recent years, the study of neurophysiological mechanisms that underlie visuo-perceptual, -spatial and -motor disorders in schizophrenia has increasingly attracted the interest of researchers.

Objective:

The study aims to review the existent literature on magnocellular/dorsal (occipitoparietal) visual processing stream impairment in schizophrenia. The impairment of relatively early stages of visual information processing was examined using experimental paradigms such as backward masking, contrast sensitivity, contour detection, and perceptual closure. The deficits of late processing stages were detected by examining visuo-spatial and -motor abilities.

Results:

Neurophysiological and behavioral studies support the existence of deficits in the processing of visual information along the magnocellular/dorsal pathway. These deficits appear to affect both early and late stages of visual information processing.

Conclusion:

The existence of disturbances in the early processing of visual information along the magnocellular/dorsal pathway is strongly supported by neurophysiological and behavioral observations. Early magnocellular dysfunction may provide a substrate for late dorsal processing impairment as well as higher-level cognition deficits.

Diagnostic Profiles of Patients Differentially Failing Executive Functioning Measures

OBJECTIVE

Limited research exists to explain differential executive functioning impairment in clinical populations, particularly between the Wisconsin Card Sorting Task (WCST) and the Trail Making Test (TMT).

METHODS

The distribution of clinical diagnoses was examined in patients failing none, one, or both tasks, and executive task performance was compared among dementia-related diagnoses. Two hundred and sixty-six participants received evaluations through an Alzheimer's Disease Research Center, which included executive tasks. Dementia-related diagnoses were established through consensus.

RESULTS

Chi-square analyses indicated that TMT failure, with or without WCST failure, possessed higher associations with dementia diagnoses. Repeated measures analysis of variance similarly indicated that participants with dementia, especially mild and moderate severity, performed worse on TMT.

CONCLUSIONS

Executive dysfunction was observed in dementia-related diagnoses, and TMT failure was implicated in dementia in higher proportions than WCST impairment. Trail Making Test appears more sensitive than WCST for assessing executive impairment across diagnoses, especially when time and resources are limited in screening and clinical settings.

Moderators of working memory deficits in children with attention-deficit/hyperactivity disorder (ADHD): a meta-analytic review

Working memory has assumed a prominent role as a primary neurocognitive deficit or endophenotype in extant models of attention-deficit/hyperactivity disorder (ADHD). The current study updated previous reviews and employed meta-analytic techniques to examine a broad range of moderating variables of effect size heterogeneity across phonological and visuospatial working memory tasks. Collectively, results revealed large between-group effect sizes across both working memory domains. In addition, several sample (percent female) and task (number of experimental trials, recall vs. recognition tasks, and demands on the central executive) moderating variables explained significant effect size variability among phonological and visuospatial studies. These findings suggest that children with ADHD exhibit statistically significant, large magnitude working memory deficits relative to their typically developing peers.

Reduction in perseverative errors with adjunctive ethyl-eicosapentaenoic acid in patients with schizophrenia: Preliminary study

INTRODUCTION

Patients with schizophrenia have significant cognitive deficits, generally resistant to conventional treatment. This preliminary study examined the effects of ethyl-eicosapentanoate (EPA) on an executive function in early course patients.

PATIENTS AND METHODS

Patients with schizophrenia were given, after an informed consent, 2 g of an EPA daily for 24 weeks, in an open-label study. The Wisconsin Card Sort Test (WCST) was administered at baseline, weeks 4, 12 and 24.

RESULTS

The 27 patients, with a mean duration of illness of 4.2 years, were all receiving atypical antipsychotics; treatment remained unchanged for the study. Perseverative errors - the key measure derived from WCST - were significantly reduced from the baseline mean of 28.2 to 18.4 errors at week 24. Positive symptoms also improved significantly. There were no correlations between EPA levels and any clinical or other neuropsychological measures.

CONCLUSION

These findings suggest that an EPA has procognitive effects for patients with schizophrenia, but controlled trials are required.

Overgeneral memory predicts stability of short-term outcome of electroconvulsive therapy for depression

PURPOSE

To investigate the predictive value of overgeneral memory (OGM) for outcome of electroconvulsive therapy (ECT) for depression.

METHODS

The Autobiographical Memory Test was used to measure OGM in 25 patients with depression before ECT. The Hamilton Rating Scale for Depression (HRSD) was administered weekly to 1 week posttreatment.

RESULTS

Overgeneral memory did not predict HRSD scores from the last ECT treatment, but did predict HRSD change scores from the last treatment to 1-week follow-up: patients high in OGM experienced a relatively greater increase in HRSD scores after the last treatment.

CONCLUSIONS

Results further extend the status of OGM as a predictor of an unfavorable course of depression to a previously unstudied ECT population.

Effects of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism on executive function in schizophrenia

BACKGROUND

The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism has been associated with both overall schizophrenia risk and severity of negative symptoms. This study examined whether schizophrenia patients homozygous for the risk allele (T/T) exhibit greater impairment in executive function, and determined the extent to which MTHFR's effects on negative symptoms underlie this relationship.

METHODS

200 outpatients with chronic schizophrenia were evaluated with the Verbal Fluency Test (VFT), Wisconsin Card Sort Test (WCST), and California Verbal Learning Test (CVLT). Performance was stratified by MTHFR C667T genotype. Path analysis determined the extent to which MTHFR effects on negative symptoms mediated the relationship between genotype and cognitive measures.

RESULTS

T/T subjects exhibited significantly greater deficits on the VFT and had more difficulty achieving the first category on the WCST. Genotype groups did not differ in CVLT performance. C677T effects on negative symptoms contributed to, but did not fully account for, genotype effects on VFT. Negative symptoms did not mediate WCST performance.

CONCLUSIONS

MTHFR C677T genotype contributes to certain executive function deficits in schizophrenia. These deficits remained significant when taking into account mediating effects of negative symptoms. Although the intermediate mechanisms for C677T effects remain uncertain, these results suggest that MTHFR-related cognitive impairment and negative symptoms reflect differing neural substrates.

Cognitive deficits and functional outcome in schizophrenia

Cognitive dysfunction is a core feature of schizophrenia. Deficits are moderate to severe across several domains, including attention, working memory, verbal learning and memory, and executive functions. These deficits pre-date the onset of frank psychosis and are stable throughout the course of the illness in most patients. Over the past decade, the focus on these deficits has increased dramatically with the recognition that they are consistently the best predictor of functional outcomes across outcome domains and patient samples. Recent treatment studies, both pharmacological and behavioral, suggest that cognitive deficits are malleable. Other research calls into question the meaningfulness of cognitive change in schizophrenia. In this article, we review cognitive deficits in schizophrenia and focus on their treatment and relationship to functional outcome.

The catechol O-methyltransferase Val158Met polymorphism and herpes simplex virus type 1 infection are risk factors for cognitive impairment in bipolar disorder: additive gene-environmental effects in a complex human psychiatric disorder

BACKGROUND

Bipolar disorder is associated with deficits in cognitive functioning. The etiology of cognitive impairment in bipolar disorder may relate to both genetic and environmental factors. A valine/methionine polymorphism of the catechol O-methyltransferase gene at amino acid 158 (COMT Val158Met polymorphism) has been identified as a risk factor for cognitive impairment in schizophrenia. Serological evidence of infection with herpes simplex virus type 1 (HSV-1) has also been identified as a risk factor for cognitive impairment in bipolar disorder.

METHODS

We used Taqman technology to measure COMT Val158Met alleles in 107 individuals with bipolar disorder and in 95 controls. We also measured antibodies to HSV-1 in sera obtained from the same individuals. Cognitive functioning was assessed with the Repeatable Battery for the Assessment of Neuropsychological Status and the Letter-Number Sequencing Test. The effects of the COMT Val158Met polymorphism and antibodies to HSV-1 on cognitive functioning were analyzed with multinomial logistic regressions.

RESULTS

The COMT Val158Val genotype and serological evidence of infection with HSV-1 are independent risk factors for cognitive impairment in individuals with bipolar disorder, particularly in the domains of immediate and delayed memory. Individuals with bipolar disorder with the COMT158 Val/Val genotype and serological evidence of HSV-1 infection were more than 85 times more likely to be in the lowest quintile of cognitive functioning when compared with the highest quintile when controlling for potential confounding variables such as symptom severity and education. Control individuals did not display this association.

CONCLUSION

Both the COMT Val158Met polymorphism and serological evidence of HSV-1 infection affect cognitive functioning in individuals with bipolar disorder.

Cognition in schizophrenia: impairments, determinants, and functional importance

Recent findings support and add to earlier findings of cognitive dysfunction in schizophrenia. Deficits across neurocognitive domains such as attention, working memory, language skills, and executive functioning tend to be moderate, with the most pronounced deficits found in verbal learning and memory. All these neurocognitive domains are related to adaptive and social skills, with executive functions and verbal learning and memory showing more variance across more domains than other neuro-cognitive variables. Negative symptoms and neurocognitive domains, although correlated, are distinct and have differential pathways of change with treatment. General psychopathology symptoms, such as depression and anxiety, may become important treatment targets as strategies are developed for translating cognitive enhancement to real-world functional performance.

Emotion processing, the amygdala, and outcome in schizophrenia

Schizophrenia is a highly complex disorder characterized by multiple independent domains of disease-namely positive, cognitive, and affective symptom clusters. Functional deficits associated with positive and (more recently) cognitive symptoms, as well as the deconstruction of these symptoms into their corresponding neural circuits, are widely discussed in the literature. To the contrary, while a link between affective symptoms and emotion processing circuitry has been hypothesized, it has been considerably less widely discussed in the literature. Here, we review deficits in the processing of emotion in schizophrenia, the role of the amygdala in the context of these deficits, and the functional implications of this relationship upon patient outcome.