Understanding the executive functioning heterogeneity in schizophrenia

Increased whole-brain functional heterogeneity in psychosis during rest and task

Past work has shown that people with schizophrenia exhibit more cross-subject heterogeneity in their functional connectivity patterns. However, it remains unclear whether specific brain networks are implicated, whether common confounds could explain the results, or whether task activations might also be more heterogeneous. Unambiguously establishing the existence and extent of functional heterogeneity constitutes a first step toward understanding why it emerges and what it means clinically.

METHODS

We first leveraged data from the HCP Early Psychosis project. Functional connectivity (FC) was extracted from 718 parcels via principal components regression. Networks were defined via a brain network partition (Ji et al., 2019). We also examined an independent data set with controls, later-stage schizophrenia patients, and ADHD patients during rest and during a working memory task. We quantified heterogeneity by averaging the Pearson correlation distance of each subject's FC or task activity pattern to that of every other subject of the same cohort.

RESULTS

Affective and non-affective early psychosis patients exhibited more cross-subject whole-brain heterogeneity than healthy controls (ps < 0.001, Hedges' g > 0.74). Increased heterogeneity could be found in up to seven networks. In-scanner motion, medication, nicotine, and comorbidities could not explain the results. Later-stage schizophrenia patients exhibited heterogeneous connectivity patterns and task activations compared to ADHD and control subjects. Interestingly, individual connection weights, parcel-wise task activations, and network averages thereof were not more variable in patients, suggesting that heterogeneity becomes most obvious over large-scale patterns.

CONCLUSION

Whole-brain cross-subject functional heterogeneity characterizes psychosis during rest and task. Developmental and pathophysiological consequences are discussed.

Neuroimaging features of cognitive impairments in schizophrenia and major depressive disorder

Cognitive dysfunctions are one of the key symptoms of schizophrenia (SZ) and major depressive disorder (MDD), which exist not only during the onset of diseases but also before the onset, even after the remission of psychiatric symptoms. With the development of neuroimaging techniques, these non-invasive approaches provide valuable insights into the underlying pathogenesis of psychiatric disorders and information of cognitive remediation interventions. This review synthesizes existing neuroimaging studies to examine domains of cognitive impairment, particularly processing speed, memory, attention, and executive function in SZ and MDD patients. First, white matter (WM) abnormalities are observed in processing speed deficits in both SZ and MDD, with distinct neuroimaging findings highlighting WM connectivity abnormalities in SZ and WM hyperintensity caused by small vessel disease in MDD. Additionally, the abnormal functions of prefrontal cortex and medial temporal lobe are found in both SZ and MDD patients during various memory tasks, while aberrant amygdala activity potentially contributes to a preference to negative memories in MDD. Furthermore, impaired large-scale networks including frontoparietal network, dorsal attention network, and ventral attention network are related to attention deficits, both in SZ and MDD patients. Finally, abnormal activity and volume of the dorsolateral prefrontal cortex (DLPFC) and abnormal functional connections between the DLPFC and the cerebellum are associated with executive dysfunction in both SZ and MDD. Despite these insights, longitudinal neuroimaging studies are lacking, impeding a comprehensive understanding of cognitive changes and the development of early intervention strategies for SZ and MDD. Addressing this gap is critical for advancing our knowledge and improving patient prognosis.

Associations of resilience, white matter topological organization, and cognitive functions in first-episode, drug-naïve schizophrenia patients: A moderated mediation analysis

BACKGROUND

Cognitive deficits are core symptoms of schizophrenia (SZ) and are associated with impaired resilience to stress. Different cognitive functions appeared to be interrelated, and the mechanism may involve neural alterations. The disrupted topological organization indicated abnormalities in the segregation and integration of brain networks that support various cognitive processes in SZ patients. Therefore, this study aimed to assess the direct and indirect effects of resilience on cognitive functions. We hypothesized that topological properties would moderate these associations.

METHODS

Forty-nine SZ patients and fifty-two healthy controls (HCs) were recruited in this study. The Connor-Davidson Resilience Scale and the MATRICS Consensus Cognitive Battery were used to examine resilience and cognitive functions, respectively, and a graph theory approach was used to assess white matter topological organization.

RESULTS

Compared to HCs, SZ patients showed lower levels of resilience and cognitive functions in multiple domains as well as abnormal global properties and nodal metrics. In addition, shorter characteristic path length was associated with a stronger indirect effect of resilience on working memory through processing speed in SZ patients.

CONCLUSION

Characteristic path length might moderate the mediating effects of processing speed in the relationship between resilience and working memory in schizophrenia patients.

Aberrant cortico-thalamo-cerebellar network interactions and their association with impaired cognitive functioning in patients with schizophrenia

Evidence indicating abnormal functional connectivity (FC) among the cortex, thalamus, and cerebellum in schizophrenia patients has increased. However, the role of the thalamus and cerebellum when integrated into intrinsic networks and how those integrated networks interact in schizophrenia patients are largely unknown. We generated an integrative network map by merging thalamic and cerebellar network maps, which were parcellated using a winner-take-all approach, onto a cortical network map. Using cognitive networks, the default mode network (DMN), the dorsal attention network (DAN), the salience network (SAL), and the central executive network (CEN) as regions of interest, the FC of 48 schizophrenia patients was compared with that of 57 healthy controls (HCs). The association between abnormal FC and cognitive impairment was also investigated in patients. FC was lower between the SAL-CEN, SAL-DMN, and DMN-CEN and within-CEN in schizophrenia patients than in HCs. Hypoconnectivity between the DMN-CEN was correlated with impaired cognition in schizophrenia patients. Our findings broadly suggest the plausible role of the thalamus and cerebellum in integrative intrinsic networks in patients, which may contribute to the disrupted triple network and cognitive dysmetria in schizophrenia.

An ecologically sensitive measure of executive cognition (the Breakfast Task) improves prediction of functional outcome in schizophrenia

Previous work has found that the Breakfast Task (BT), a computerized, ecologically informed executive ability measure, is sensitive to group differences in aging, acquired brain injury, and Parkinson's disease. We investigated whether this measure improves the prediction of functional status over and above standard measures of general intellectual ability, relationship perception, life skills, and symptom severity in individuals with schizophrenia. Regression analyses were conducted to evaluate the joint and incremental validity of the BT in predicting functional disability scores on the World Health Organization Disability Assessment Scale (WHODAS 2.0). Analyses with combined patient (n = 25) and control (n = 32) participants showed that participant status (patients versus control) was the only significant predictor of functional outcome. However, in the patient data, the proportion of variance accounted for improved significantly (model R² of 4% vs. 25%) when BT scores were added to a model containing clinical (Brief Psychiatric Rating Scale), social (Relationships Across Domains), intellectual (Wechsler Abbreviated Scale of Intelligence), and life skills (Canadian Objective Assessment of Life Skills) measures. Results suggest that the BT, a tool that captures complex executive functioning, improves the prediction of disability in patients with schizophrenia and has potential assessment applications.

Executive deficits in schizophrenia: mediation by processing speed and its relationships with aging

BACKGROUND

Executive deficits are a core characteristic of schizophrenia. Yet, the origin of these impairments remains unclear as they may be caused by processing slowing. This issue is of particular interest for aging insofar as cognitive aging is also associated with a decline in executive functioning and a slowing of processing speed. As schizophrenia patients' life expectancy increases, a better understanding of the origin of older patients' cognitive deficits becomes essential so that healthcare can be adapted to suit them. This study aims to determine whether processing speed mediates how schizophrenia affects executive functions and whether these relationships are moderated by age.

METHODS

Sixty-two schizophrenia patients (27 women) and 62 healthy comparison subjects matched for age (range: 18-76 years), gender and education performed neurocognitive tests to evaluate their executive functions (shifting, updating, inhibition and access) and processing speed.

RESULTS

Processing speed mediated the effect of schizophrenia on the four specific executive functions, and age moderated this mediation for shifting, updating and access, but in different ways. Age moderated the effect of processing speed on shifting, the direct effect of schizophrenia on access, and both the effect of processing speed and the direct effect of schizophrenia on updating.

CONCLUSIONS

This research highlights the need to evaluate processing speed routinely during therapeutic follow-up, as it is easy and simple to assess and appears to be at the heart of the cognitive deficits in schizophrenia. Finally, processing speed abilities yield information about the evolution of cognition with aging in schizophrenia.

What Accounts for the Factors of Psychopathology? An Investigation of the Neurocognitive Correlates of Internalising, Externalising, and the p-Factor

Neurocognitive deficits have been consistently associated with a wide range of psychopathology and are proposed to not only be a consequence of the development of psychopathology but also directly involved in its aetiology. However, there is no clear understanding of what neurocognitive processes are particularly important to mental health. In this paper, we explored the association between neurocognitive abilities and the factors derived from structural models of psychopathology. Four hundred participants from a representative community sample completed measures of symptomology and substance use, as well as 8 neurocognitive tasks. We found a correlated-factors model, with internalising and externalising as the higher-order factors, and a single-factor model with only the p-factor, to be good fits for the data. Tasks that measured the speed of processing were significantly associated with internalising, externalising, and the p-factor, and accounted for significant amounts of unique variance in the factors after accounting for the common variance of the other tasks. Tasks that measured working memory, shifting, and inhibition were not significantly associated with psychopathology factors. Our findings suggest that neurocognitive abilities may not be differentially associated with psychopathology factors, but that speed of processing is a common correlate of the factors. We emphasise the importance of examining neurocognitive abilities and psychopathology on the individual level.

Executive functions in 7-year-old children of parents with schizophrenia or bipolar disorder compared with controls: The Danish High Risk and Resilience Study-VIA 7, a population-based cohort study

Cognitive impairments are strongly associated with schizophrenia (SZ) and bipolar disorder (BP) with executive functions (EF) impairments as a likely key feature. Studies of everyday behavior rated EF in young children at familial high risk of SZ (FHR-SZ) are scarce and, to our knowledge, non-existent in young children at familial high risk of BP (FHR-BP). We aimed to compare everyday behavior-rated EF of FHR-SZ, FHR-BP, and control children. A nationwide population-based cohort of 522 7-year-old children with parents diagnosed with either SZ (N = 202) or BP (N = 120) and matched controls (N = 200) were recruited using the Danish national registries. The children's EF were assessed with the Behavior Rating Inventory of Executive Functions questionnaire rated by primary caregivers and teachers. According to primary caregiver assessments, FHR-SZ children displayed widespread EF impairments and had an odds ratio of 3.7 (2.0-6.9) of having clinically significant global EF impairments compared to controls. FHR-BP children were most severely impaired regarding EF related to emotional control and had an odds ratio of 2.5 (1.2-5.1) of clinically significant global EF impairments compared to controls. Teacher assessments were overall comparable to primary caregiver assessments but teachers rated more difficulties in the FHR-SZ group than primary caregivers. Already at age 7, children with a parental history of SZ or BP displayed significant impairments of EF in everyday-life situations. FHR-SZ children displayed widespread significant impairments of EF, whereas FHR-BP children were most severely impaired on emotional control. Clinicians should be aware of potential EF impairments in FHR children.

Reduced Microstructural Lateralization in Males with Chronic Schizophrenia: A Diffusional Kurtosis Imaging Study

Decreased brain lateralization is considered a trait marker of schizophrenia. Whereas reductions in both functional and macrostructural gray matter laterality in schizophrenia are well established, the investigation of gray matter microstructural lateralization has so far been limited to a small number of ex vivo studies, which limits the understanding of neurobiological substrates involved and development of adequate treatments. The aim of the current study was to assess in vivo gray matter microstructure lateralization patterns in schizophrenia by employing the diffusion kurtosis imaging (DKI)-derived mean kurtosis (MK) metric. MK was calculated for 18 right-handed males with chronic schizophrenia and 19 age-matched healthy control participants in 46 bilateral gray matter regions of interest (ROI). Microstructural laterality indexes (μLIs) were calculated for each subject and ROI, and group comparisons were conducted across regions. The relationship between μLI values and performance on the Wisconsin Card Sorting Test (WCST) was also evaluated. We found that compared with healthy controls, males with chronic schizophrenia had significantly decreased μLI across cortical and subcortical gray matter regions, which was correlated with poorer performance on the WCST. Our results suggest the ability of DKI-derived MK to capture gray matter microstructural lateralization pathology in vivo.

Going "Up" to Move Forward: S-1 Bifactor Models and the Study of Neurocognitive Abilities in Psychopathology

Recently, structural models of psychopathology, that address the diagnostic stability and comorbidity issues of the traditional nosological approach, have dominated much of the psychopathology literature. Structural approaches have given rise to the p-factor, which is claimed to reflect an individual's propensity toward all common psychopathological symptoms. Neurocognitive abilities are argued to be important to the development and maintenance of a wide range of disorders, and have been suggested as an important driver of the p-factor. However, recent evidence argues against p being an interpretable substantive construct, limiting conclusions that can be drawn from associations between p, the specific factors of a psychopathology model, and neurocognitive abilities. Here, we argue for the use of the S-1 bifactor approach, where the general factor is defined by neurocognitive abilities, to explore the association between neurocognitive performance and a wide range of psychopathological symptoms. We use simulation techniques to give examples of how S-1 bifactor models can be used to examine this relationship, and how the results can be interpreted.

Psychopathology and Neurocognition in the Era of the p-Factor: The Current Landscape and the Road Forward

Neurocognitive abilities have frequently been claimed to be involved in the aetiology of psychopathology. Neurocognitive deficits have been reported across many disorders, and theoretical perspectives associate these deficits to the onset and maintenance of the symptomology. Recently, the heterogeneity of symptoms, and comorbidity of disorders, have motivated the development of structural models of psychopathology. Structural models indicate that factors such as internalising, externalising, thought disorder and the p-factor account for a wide variety of symptomology. It is unclear how neurocognitive abilities are best examined within these structures to advance our understanding of psychopathology. In this paper, we use Caspi et al.’s seminal writings as a framework to describe how neurocognitive abilities have been previously associated with categorical disorders and recently associated, and claimed to drive, the factors of psychopathology. We discuss the implications of the p-factor as a substantive construct or statistical artefact, and how this impacts the exploration of neurocognitive abilities and psychopathology. Further, we provide the case for alternative structural approaches, describe an innovative hypothesis of neurocognitive functioning, the multidimensional hypothesis, and explain how this may further our understanding of the heterogeneity of neurocognitive performance and psychopathology at the individual level. Finally, we provide a road forward for the future examination of neurocognitive abilities in psychopathology.

Mindfulness-Based Interventions for In-Patients With Schizophrenia Spectrum Disorders-A Qualitative Approach

In recent years, mindfulness-based interventions (MBI) have gained clinical relevance in the treatment of patients with schizophrenia spectrum disorders (SSDs). High symptom burden, long durations of hospitalization and high rehospitalization rates demonstrate the severity and cost-intensity of these disorders. MBIs have shown promising treatment outcomes in a small number of trials, primarily taking place in English-speaking countries. The current study aims to explore mechanisms and processes as well as adverse effects of MBIs on in-patients with SSDs in a German university hospital setting. A qualitative design based on inductive thematic analysis accompanied by quantitative assessments was chosen. A semi-structured interview guide was developed by psychiatrists and psychologists to assess patient experiences, perceptions, thoughts, and feelings during and after taking part in a MBI. Twenty-seven interviews were conducted between September 2017 and October 2018 with in-patients who are diagnosed with schizophrenia or schizoaffective disorder. Rater-based questionnaires, such as the Positive and Negative Syndrome Scale (PANSS), Montgomery Asberg Depression Rating Scale (MADRS), and Psychotic Symptom Rating Scales-Auditory Hallucination (PSYRATS-AH) were administered at baseline to collect clinical outcomes. Qualitative analysis revealed two domains: content and function. In the first domain related to content with the core elements "detachment and rumination", "presence and getting lost", "non-judgment and judgment", and effects with "emotions", "cognition", and "symptom changes". A second domain related to function was extracted, including the relevance of perception of context and transfer to everyday life. Overall, improvements concerning cognition, distress, and psychopathology were detected, while no adverse effects, such as increased psychotic symptoms, were revealed. As the first study of its kind, mechanisms, processes, and the safety of MBIs were explored and confirmed in a sample of German in-patients with SSDs. The results of this qualitative study are in line with recent findings on MBIs amongst patients with psychotic disorders from other countries. Results lay the ground for future research to focus on the systematic study of MBIs in large samples, its treatment processes, outcomes, and effectiveness for in-patients with SSDs.

Executive functions in schizophrenia aging: Differential effects of age within specific executive functions

There are common cognitive and brain abnormalities in schizophrenia and healthy aging which may cumulate in schizophrenia aging. However, the course of executive deficits in late-life schizophrenia is still controversial as it remains unclear whether schizophrenia patients show accelerated aging. The use of specific models of executive functions might help to shed new lights on this issue. The aim of this study was then to determine how each of the four specific executive functions (shifting, updating, inhibition and access to long-term memory) is affected by aging in schizophrenia compared to healthy aging. 20 younger (age 18-34), 17 middle-aged (age 35-49) and 25 older (age 59-76) schizophrenia patients and 62 healthy comparison participants matched for gender, age and education performed a neurocognitive battery evaluating the four specific executive functions. Schizophrenia patients performed worse than comparison participants on shifting, updating and access, whereas inhibition appeared preserved. Age affected the four functions with increased degradation of shifting and access in schizophrenia patients, whereas updating and inhibition showed a normal decline with age. These results suggest a vulnerability of prefrontal and cingulate cortexes in schizophrenia aging. Moreover, as age affected the specific executive functions differently, remediation programs should be adapted to older patients. Models of specific executive functions are useful for understanding the complexity of cognition in schizophrenia and its course during later life so that healthcare can be adapted accordingly.

A meta-analysis of executive dysfunction in patients with schizophrenia: Different degree of impairment in the ecological subdomains of the Behavioural Assessment of the Dysexecutive Syndrome

We performed meta-analyses of studies using the 6 subtests of the neuropsychological test battery, the Behavioural Assessment of the Dysexecutive Syndrome (BADS), in order to assess and compare subdomains of executive dysfunction in stable phase patients with schizophrenia relative to healthy controls. The meta-analyses were performed according to the PRISMA statement. A systematic literature search was performed yielding 10 studies for inclusion (N_SCH= 375; N_HC = 541). Meta-analyses were done using Stata IC 14. Due to large heterogeneity and the few number of studies a random-effects model was used along with Hedges' g. Results showed that relative to healthy controls, patients with schizophrenia overall performed significantly worse in all subtests of BADS. However, moderate effect sizes were seen with regard to temporal estimation and strategy-forming, while very large effect sizes were seen regarding complex forward planning, inhibition, cognitive flexibility and novel problem solving. The findings from this meta-analysis demonstrate a significant difference between patients with (primarily) longer lasting schizophrenia and healthy control subjects on all subdomains of executive functions (EF). But some aspects of EF seem to be more severely affected than others. Future research and clinical interventions need to differentiate between subdomains of EF.

Global and Specific Profiles of Executive Functioning in Prodromal and Early Psychosis

Objective: Numerous reports on neurocognitive functioning deficits in individuals at clinical high risk (CHR) and first-episode psychosis (FEP) patients suggest particular deficits in executive functioning (EF). However, to date, most of the studies have administered a single or a few EF tests to participants, and few investigations have examined the different components of EF to identify specific subdomains of relative strength and weakness. Method: Forty CHR subjects, 85 FEP patients, and 85 healthy controls (HCs) were assessed with a neuropsychological battery to elucidate the profiles of EF in the subdomains of shift, attention, fluency, and planning. Results: In the subdomains of shift, attention, and fluency, CHR individuals and FEP patients showed deficits compared to HC. The post hoc analysis revealed that CHR individuals had comparable attention shifting and phonemic fluency compared to FEP. CHR showed intermediate deficits between FEP and HCs in spatial working memory and semantic fluency, and the largest effect size was observed in semantic fluency both for CHR and FEP. Conclusion: Overall, the findings of this study, in addition to providing detailed profiles of EF in prodromal and early psychosis patients, highlight the informative value of the specific subdomains of semantic fluency and spatial working memory.

A direct examination of the cognitive underpinnings of multitasking abilities: A first study examining schizophrenia

Many real world activities are complex and require multitasking abilities. However, the nature of these abilities remains poorly understood, and in particular in schizophrenia. The aim of the present study was to provide a better understanding of such abilities with the help of a newly developed computerized tool, the Computerized Meeting Preparation Task (CMPT). Fifty-seven individuals with schizophrenia and 39 healthy controls completed the CMPT and an extensive cognitive battery. Patients were also evaluated with a series of clinical measures. During the CMPT, participants are asked to prepare a room for a meeting while, at the same time, dealing with interruptions, solving problems, and remembering prospective memory instructions. The CMPT was found to significantly differentiate patients and healthy controls for several variables. Results also showed that multitasking abilities were related to a large array of cognitive functions and, in particular, to those associated to executive functioning. These relations were not explained by the presence of a general cognitive impairment. Finally, a double dissociation between multitasking abilities and performance on standard cognitive tests was observed. Altogether, these results underline the importance of evaluating multitasking abilities in schizophrenia as it allows detecting cognitive difficulties that cannot be identified by standard cognitive tests.

Environmental dependency phenomena in schizophrenia: a pilot study

INTRODUCTION

Environmental dependency phenomena refer to the enslavement of patients' performances under the characteristics of the tasks and were first described in case of prefrontal lobe damage. Two forms of environmental dependency, executive and social, may be dissociated, which involve respectively dorsolateral and orbital prefrontal cortex (PFC) dysfunction. Schizophrenia is widely considered to be caused by PFC dysfunction, but no study to date has addressed environmental dependency in this pathology.

METHODS

We compared patients (N = 17) and healthy controls (N = 28) on a task dedicated to the study of environmental dependency.

RESULTS

Our results demonstrate the presence of environmental dependency in schizophrenia. Each form of environmental dependency can be highlighted independently, as previously demonstrated by studies with prefrontal patients.

CONCLUSIONS

These findings suggest specific prefrontal dysfunction for each subgroup of patients and demonstrate a dissociation between socio-cognitive and neurocognitive performance in schizophrenia. Additionally, we found relationships between symptomatology and environmental dependency. This pilot study supports the relevance of studying environmental dependency to highlight specific patterns of prefrontal disorders in schizophrenia, which may contribute to a better understanding of PFC dysfunction in schizophrenia.

Deficit of supramodal executive control of attention in schizophrenia

Although a deficit in executive control of attention is one of the hallmarks in schizophrenia that has significant impact on everyday functioning due to its relationship with thought processing, whether this deficit occurs across modalities, i.e., is supramodal, remains unclear. To investigate the supramodal mechanism in SZ, we examined cross-modal correlations between visual and auditory executive control of attention in a group of patients with schizophrenia (SZ, n = 55) compared to neurotypical controls (NC, n = 55). While the executive control effects were significantly correlated between the two modalities in the NC group, these effects were not correlated in the SZ group, with a significant group difference in the correlation. Further, the inconsistency and magnitude of the cross-modal executive control effects were significantly larger in the SZ group compared to the NC group. Together, these results suggest that there is a disruption of a common supramodal executive control mechanism in patients with schizophrenia, which may be related to the thought processing disorder characterizing the disorder.

French Version of the Hayling Sentence Completion Test, Part II: Clinical Utility in Schizophrenia and Parkinson's Disease

Objective

We previously developed normative data for a French version of the Hayling Sentence Completion Test (f-HSCT) for adults and elderly people. The present study aimed to evaluate the clinical utility of the f-HSCT norms in two clinical populations in which inhibition dysfunction has been largely documented, i.e., Parkinson's disease (PD) and schizophrenia.

Method

Eighty-five non-demented patients with idiopathic PD and 64 out-patients with schizophrenia completed the automatic and inhibition conditions of the f-HSCT. Time latencies and errors raw data of each patient were compared to the norms previously developed by the authors.

Results

In the automatic condition, errors were rare in both clinical groups and time latencies on this condition felt within the normative data range. Compared with the standardized norms, 46% of patients with PD and 61% of patients with schizophrenia had a deviant performance (i.e., borderline or deficit) for the inhibition error score. The proportion of patients with a deviant performance on the inhibition response time score was similar in both clinical samples (respectively, 25% and 23%). Finally, slightly more than half of patients with PD and more than two-thirds of patients with schizophrenia had a deviant performance on at least one of the f-HSCT inhibition measures.

Conclusions

Our results suggest that the f-HSCT has a strong potential for characterizing inhibition of prepotent responses in PD and schizophrenia. Furthermore, it requires only a short administration time so it may be ideal to detect response inhibition in clinical populations with cognitive fatigue.

Performance of Verbal Fluency as an Endophenotype in Patients with Familial versus Sporadic Schizophrenia and Their Parents

What’s the neurocognitive deficit as an endophenotype to familial schizophrenia? Here, we investigate the neurocognitive endophenotype in first-episode patients with familial schizophrenia (FS) and sporadic schizophrenia (SS), and their parents. 98 FS patients and their 105 parents; 190 SS patients and their 207 parents; 195 controls matched with patients, and 190 controls matched with the patients’ parents, were assessed with the short version of the Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC), the immediate and delayed logical memory tests from the Wechsler Memory Scale-Revised in China (WMS-RC), the Verbal Fluency Test (VFT), the Trail Making Test Parts A and B-Modified (TMA, TMB-M), and the Modified Wisconsin Card Sorting Test (WCST-M). The results showed that with age, gender, and education as covariates, after controlling for false discovery rates, the FS group and their parent group performed worse than the SS group and their parent group on VFT. No significant differences were found for other neurocognitive tests between the FS and SS patient groups, and their respective parent groups. Our findings suggest the patients with familial and sporadic schizophrenia and their respective parent groups may have a different genetic predisposition in relation to a cognitive endophenotype.

Executive dysfunction in psychosis following traumatic brain injury (PFTBI)

INTRODUCTION

Executive dysfunction is well established in patients with traumatic brain injury and in schizophrenia (SCZ). However, assessments of executive function in psychosis following traumatic brain injury (PFTBI) are limited and inconsistent, and often do not reflect the deficits demonstrated in patients with traumatic brain injury (TBI) or SCZ. We sought to determine the extent of executive dysfunction in PFTBI relative to three comparison cohorts.

METHOD

Measures of executive function were administered to dually diagnosed patients with PFTBI (n = 10) including tests of mental inhibition and switching, processing speed, and attention: the Stroop Task, Trail Making Test (TMT), and the Attention subtest of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Demographically comparable patients with TBI (n = 10), SCZ (n = 23), and healthy controls (n = 23) underwent an identical battery.

RESULTS

Significant executive dysfunction was evident in patients with PFTBI on all measures. Relative to all three comparison cohorts patients with PFTBI performed most poorly.

CONCLUSIONS

These data present novel evidence of substantially impaired executive function across four task types in PFTBI and suggest that TBI and psychosis have an additive influence on executive function deficits. Treatment programs requiring substantial executive engagement are not suitable for patients dually diagnosed with PFTBI.

Preserved Intention Maintenance and Impaired Execution of Prospective Memory Responses in Schizophrenia: Evidence from an Event-based Prospective Memory Study

Executive system dysfunction and impaired prospective memory (PM) are widely documented in schizophrenia. However, it is not yet clarified which components of PM function are impaired in this disorder. Two plausible target components are the maintenance of delayed intentions and the execution of PM responses. Furthermore, it is debated whether the impaired performance on frequently used executive tasks is associated with deficit in PM functions. The aim of our study was twofold. First, we aimed to investigate the specific processes involved in event-based PM function, mainly focusing on difference between maintenance of intention and execution of PM responses. Second, we aimed to unfold the possible connections between executive functions, clinical symptoms, and PM performance. An event-based PM paradigm was applied with three main conditions: baseline (with no expectation of PM stimuli, and without PM stimuli), expectation condition (participants were told that PM stimuli might occur, though none actually did), and execution condition (participants were told that PM stimuli might occur, and PM stimuli did occur). This procedure allowed us to separately investigate performances associated with intention maintenance and execution of PM responses. We assessed working memory and set-shifting executive functions by memory span tasks and by the Wisconsin Card Sorting Test (WCST), respectively. Twenty patients diagnosed with schizophrenia and 20 healthy control subjects (matched according to age and education) took part in the study. It was hypothesized that patients would manifest different levels of performance in the expectation and execution conditions of the PM task. Our results confirmed that the difference between baseline performance and performance in the execution condition (execution cost) was significantly larger for participants diagnosed with schizophrenia in comparison with matched healthy control group. However, this difference was not observed in the expectation condition. The PM performance in the execution condition was correlated with impaired executive functions in schizophrenia. Specifically, the size of execution cost positively correlated with percent of perseverative errors committed on WCST by the patient group. Our results suggest that maintenance of delayed intentions is unimpaired in schizophrenia, whereas the impairment in execution of PM responses is associated with set-shifting deficit.

Neuropsychological correlates of remission in chronic schizophrenia subjects: The role of general and task-specific executive processes

Background

Although cognitive deficits have consistently been characterized as core features of schizophrenia, they have not been incorporated into definitions of remission. Furthermore, just a few studies have examined the relationship between cognitive deficits and symptomatic remission. The main aim of the present study is to evaluate the executive functioning of nonremitted schizophrenia patients.

Methods

72 remitted and 42 nonremitted schizophrenia patients, and 119 healthy controls were examined. Subjects were tested with a comprehensive battery of cognitive tests, including a measure to assess the general components of executive functioning and individual tasks to tap the three specific executive dimensions assessed in the present study, namely updating, shifting and inhibition.

Results

Schizophrenia subjects performed poorly on general executive functioning and shifting tasks in comparison to healthy controls. Remitted subjects performed better than nonremitted on inhibition and updating tasks. Whereas being a male and showing decreases in updating increase the chances of being in the nonremitted schizophrenia subjects group, increases in shifting and updating enhance the odds of being in the healthy control group.

Conclusion

The present findings suggest that executive function deficits are present in chronic schizophrenic patients. In addition, specific executive processes might be associated to symptom remission. Future studies examining prospectively first-episode, drug naive patients diagnosed with schizophrenia may be especially elucidative.

Is duration of illness really influencing outcome in major psychoses?

BACKGROUND

An increasing number of studies identifies the duration of illness (DI) as an important predictor of outcome in patients affected by major psychoses (MP). The aim of the present paper was to revise medical literature about DI and its effects on MP, focusing in particular on the relationship between DI and outcome with particular reference to treatment response, suicidal risk, cognitive impairment and social functioning.

METHODS

A search in the main database sources has been performed to obtain a comprehensive overview. Studies with different methodologies (open and double-blinded) have been included, while papers considering other variables such as duration of untreated episode/illness were excluded. MP included the diagnoses of schizophrenia, bipolar disorder and major depressive disorder.

RESULTS

Available data show that DI influences treatment response, suicidal risk and loss of social functioning in schizophrenic patients, while results are more controversial with regard to cognitive impairment. In bipolar disorder, a long DI has been associated with less treatment response, more suicidal risk and cognitive impairment, but more data are needed to draw definitive conclusions. Finally, studies, regarding DI of illness and its predictive value of outcome in major depressive disorder show contradictory results.

CONCLUSIONS

DI appears a negative outcome factor particularly for schizophrenia, while with regard to mood disorders, more data are needed to draw definitive sound conclusions.

A comparative study of the working memory multicomponent model in psychosis and healthy controls

Working memory deficits are considered nuclear deficits in psychotic disorders. However, research has not found a generalized impairment in all of the components of working memory. We aimed to assess the components of the Baddeley and Hitch working memory model: the temporary systems-the phonological loop, the visuospatial sketchpad and the episodic buffer (introduced later by Baddeley)-and the central executive system, which includes four executive functions: divided attention, updating, shifting and inhibition. We assessed working memory performance in a sample of 21 patients with a psychotic disorder and 21 healthy controls. Patients also underwent a clinical assessment. Both univariate and repeated measures ANOVAs were applied to analyze performance in the working memory components between groups. Patients with a psychotic disorder underperformed compared to the controls in all of the working memory tasks, but after controlling for age and premorbid IQ, we only found a difference in performance in the N-Back task. Repeated measures ANCOVAs showed that patients also underperformed compared to the controls in the Digit span test and the TMT task. Not all of the components of working memory were impaired in the patients. Specifically, patients' performance was impaired in the tasks selected to assess the phonological loop and the shifting executive function. Patients' also showed worse performance than controls in the N-Back task, representative of the updating executive function. However, we did not find higher impairment in the patients' performance respect to controls when increasing the loading of the task.

Hierarchical Classes Analysis (HICLAS): A novel data reduction method to examine associations between biallelic SNPs and perceptual organization phenotypes in schizophrenia

The power of SNP association studies to detect valid relationships with clinical phenotypes in schizophrenia is largely limited by the number of SNPs selected and non-specificity of phenotypes. To address this, we first assessed performance on two visual perceptual organization tasks designed to avoid many generalized deficit confounds, Kanizsa shape perception and contour integration, in a schizophrenia patient sample. Then, to reduce the total number of candidate SNPs analyzed in association with perceptual organization phenotypes, we employed a two-stage strategy: first a priori SNPs from three candidate genes were selected (GAD1, NRG1 and DTNBP1); then a Hierarchical Classes Analysis (HICLAS) was performed to reduce the total number of SNPs, based on statistically related SNP clusters. HICLAS reduced the total number of candidate SNPs for subsequent phenotype association analyses from 6 to 3. MANCOVAs indicated that rs10503929 and rs1978340 were associated with the Kanizsa shape perception filling in metric but not the global shape detection metric. rs10503929 was also associated with altered contour integration performance. SNPs not selected by the HICLAS model were unrelated to perceptual phenotype indices. While the contribution of candidate SNPs to perceptual impairments requires further clarification, this study reports the first application of HICLAS as a hypothesis-independent mathematical method for SNP data reduction. HICLAS may be useful for future larger scale genotype-phenotype association studies.

Cognitive control and schizophrenia: The greatest reliability of the Stroop task

Three components of cognitive inhibition were compared in patients with schizophrenia and healthy controls. Nineteen patients with schizophrenia were compared to 30 healthy controls, matched for age, sex, and educational level. Cognitive inhibition was examined by (i) access to relevant information (Reading with distraction task), (ii) suppression of no longer relevant information (Trail Making Test B), and (iii) restraint of cognitive resources to relevant information (Stroop Test, Hayling Sentence Completion Test, Go/No-Go Test). Beck Depression Inventory, and Positive and Negative Syndrome Scale were also used. Compared to healthy controls, patients with schizophrenia and stabilized for at least 6 months were slower in the inhibition condition at the Stroop task, read more distractors at the RWD, and made more perseverative errors at the TMT, even after controlling for age, Mini-Mental State Examination score, information speed processing, and accuracy. This difference remained significant after taking into account the level of depressive symptoms and the severity of psychotic symptoms. In multivariate analyses, only the Stroop interference index explained cognitive inhibition deficit in patients with schizophrenia. The abnormal cognitive inhibition process observed in patients with schizophrenia could therefore concerns the ability to restraint, rather than the access or the suppression processes.

Can individuals with schizophrenia be instructed to deliberately feign memory deficits?

INTRODUCTION

Neuropsychological tests are increasingly applied in research studies and clinical practice in psychiatry. In this context, the detection of poor effort is crucial to adequately interpret data. We measured schizophrenia patients' performance on a memory test designed to detect excessive malingering (the "21-Item Test"), before examining whether a second group of schizophrenia patients would excessively malinger on this test when given an incentive to feign memory impairment.

METHODS

Two independent studies including respectively 49 schizophrenia patients and 100 controls (study 1) and 25 schizophrenia patients and 25 controls (study 2) were conducted. In study 1, participants were asked to complete the 21-Item Test to the best of their ability. In study 2, participants were given a hypothetical scenario in which having a memory impairment would be financially advantageous for them, before completing the 21-Item Test.

RESULTS

In study 1, no participant scored at levels indicative of excessive malingering. In study 2, 84% of controls but only 36% of patients scored at excessive levels of malingering, and these patients had higher executive functioning than patients who did not excessively malinger, although it should be noted that a significantly greater proportion of patients excessively malingered in study 2 compared to study 1.

CONCLUSIONS

These results indicate that schizophrenia patients do not normally feign excessive memory impairment during psychological testing. Furthermore, they are less able and/or less inclined to excessively malinger than controls in situations where a memory impairment would be advantageous, perhaps indicating a better ability to malinger without detection. Potential clinical implications are discussed.

Medial frontal gyrus alterations in schizophrenia: relationship with duration of illness and executive dysfunction

Executive functioning is consistently impaired in schizophrenia, and it has been associated with reduced gray matter volume in prefrontal areas. Abnormalities in prefrontal brain regions have also been related to the illness duration. The aim of the study was to investigate the effect of executive functioning decline and chronicity in prefrontal regions of patients with schizophrenia. Participants comprised 33 schizophrenic patients, 18 with duration of illness (DoI) shorter than 10 years and 15 with duration of illness longer than 10 years. In addition, 24 healthy controls served as a comparison group. Participants performed the Wisconsin Card Sorting Test (WCST) and underwent structural magnetic resonance imaging. Patients with longer DoI showed significant reduction of gray matter volume in the left medial frontal gyrus compared with healthy controls. Moreover, there was a trend for greater gray matter volume decrease in patients with a longer illness duration compared with patients with shorter illness duration. There was no interaction between the volume of the left medial frontal gyrus performance on the WCST. The present study supports the hypothesis that medial frontal gyrus alterations in schizophrenia are sensitive to duration of illness. These alterations were not associated with executive functioning.

Refining the latent structure of neuropsychological performance in schizophrenia

BACKGROUND

Elucidating the cognitive architecture of schizophrenia promises to advance understanding of the clinical and biological substrates of the illness. Traditional cross-sectional neuropsychological approaches differentiate impaired from normal cognitive abilities but are limited in their ability to determine latent substructure. The current study examined the latent architecture of abnormal cognition in schizophrenia via a systematic approach.

METHOD

Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were carried out on a large neuropsychological dataset including the Brief Assessment of Cognition in Schizophrenia, Continuous Performance Test, Wisconsin Card Sorting Test, Benton Judgment of Line Orientation Test, and Wechsler Abbreviated Scale of Intelligence matrix reasoning derived from 1012 English-speaking ethnic Chinese healthy controls and 707 schizophrenia cases recruited from in- and out-patient clinics.

RESULTS

An initial six-factor model fit cognitive data in healthy and schizophrenia subjects. Further modeling, which accounted for methodological variance between tests, resulted in a three-factor model of executive functioning, vigilance/speed of processing and memory that appeared to best discriminate schizophrenia cases from controls. Factor analytic-derived g estimands and conventionally calculated g showed similar case-control discrimination. However, agreement analysis suggested systematic differences between both g indices.

CONCLUSIONS

Factor structures derived in the current study were broadly similar to those reported previously. However, factor structures between schizophrenia subjects and healthy controls were different. Roles of factor analytic-derived g estimands and conventional composite score g were further discussed. Cognitive structures underlying cognitive deficits in schizophrenia may prove useful for interrogating biological substrates and enriching effect sizes for subsequent work.

Category fluency in schizophrenia research: is it an executive or semantic measure?

INTRODUCTION

The semantic fluency task is described as a measure of semantic function and utilised in schizophrenia (SZ) research to demonstrate semantic deficits. Two meta-analyses support the efficacy of this task in measuring semantic function in SZ; however, a more recent meta-analysis suggests that executive dysfunction is the predominant determinant of semantic fluency performance in this group. By (1) matching the semantic and executive fluency tasks on discriminant validity, and (2) including an additional fluency task containing both semantic and executive elements (animals by size), this study aimed to determine whether semantic fluency is in fact an appropriate measure of semantic function in SZ.

METHODS

Forty-two SZ participants and 40 healthy controls performed 3 fluency tasks: executive (F, A, S), semantic (body parts), and semantic/executive (animals by size). Performance on these tasks was analysed in two ways, (1) based on discriminant validity and (2) by matching output between the semantic and semantic/executive fluency tasks.

RESULTS

When the semantic and executive fluency tasks were matched, executive fluency performance was either (1) mildly impaired or (2) not impaired in SZ. Both semantic and semantic/executive performance was impaired in SZ regardless of calculation. Group differences on the semantic/executive task remained when executive function was controlled for, but disappeared when semantic fluency effects were controlled for.

CONCLUSIONS

The findings support earlier meta-analyses in finding that the semantic fluency task is a robust measure of semantic memory function in SZ.

Cluster analysis of cognitive deficits may mark heterogeneity in schizophrenia in terms of outcome and response to treatment

Cognitive impairments are central to schizophrenia, but their clinical utility for tagging heterogeneity in lifetime outcome and response to treatment is not conclusive. By exploiting four cognitive domains consistently showing large deficits in studies, we tested whether cluster analysis would define separate subsets of patients and then whether the disease heterogeneity marked by these clusters would be related to lifetime outcome and response to treatment. A total of 112 schizophrenia patients completed a neuropsychological evaluation. The PANSS, GAF-S and GAF-F were rated at the onset and endpoint of the illness trajectory. A blind judgment of the lifetime response to treatment was made. The first cluster presented near-normal cognitive performance. Two other clusters of severely impaired patients were identified: one generally impaired in the four cognitive domains and another selectively impaired in visual episodic memory and processing speed, each relating to a different lifetime evolution of disease and treatment response. Although the two impaired clusters were clinically indistinguishable in symptom severity and functioning at disease onset, patients with selective cognitive impairments demonstrated better improvement at outcome, whereas the generally impaired patients were more likely to be treatment refractory. The findings have implications for the management of patients and for clinical trials since particular combinations of cognitive deficits in patients would influence their treatment response.

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.