Component mechanisms of executive function in schizophrenia and their contribution to functional outcomes

Differential patterns of executive dysfunction across depressive phenotype in schizophrenia and major depressive disorder

Executive functioning (EF) deficits are common in both schizophrenia (SZ) and major depressive disorder (MDD). However, it remains unclear whether specific EF subdomains are differently affected in SZ and MDD, particularly in relation to depressive symptoms. This study aims to investigate EF subdomains in MDD, SZ with depressive symptoms (SZ-D), SZ without depressive symptoms (SZ-ND) and healthy controls (HC), and to explore the relationships between psychopathological symptoms and EF performance. A total of 213 participants were recruited, including 76 MDD, 81 SZ patients and 56 HC. EF was assessed using the n-back, Stroop color-word and more-odd shifting tasks. The 17-item Hamilton Depression Scale, Hamilton Anxiety Scale and Positive and Negative Syndrome Scale were used to assess depression, anxiety and psychopathological symptoms. In the 2-back task, SZ-D patients had longer response time (RT) (p < 0.01), while SZ-ND patients had lower accuracy rates (AR) (p < 0.01) compared to MDD patients and HC. In more-odd shifting task, SZ-D patients showed longer RT for shift cost (p < 0.01), and SZ-ND patients had lower AR for shift cost (p < 0.01) compared to MDD and HC. Multiple regression analysis revealed that negative symptoms were associated with AR in the 2-back condition in SZ-D, while in SZ-ND, negative symptoms was related to AR in the 1-back condition. SZ patients showed more severe EF dysfunction, with depressive symptoms in SZ primarily affecting response speed rather than accuracy. Negative symptoms were associated with EF dysfunction in both MDD and SZ patients.

Frontal brain volume correlates of impaired executive function in schizophrenia

Cognitive impairments affect functional capacity in individuals with schizophrenia (SZH), but their neural basis remains unclear. The Wisconsin Card Sorting Test (WCST), and the Stroop Task (SCWT), are paradigmatic tests which have been used extensively for examining executive function in SZH. However, few studies have explored how deficits on these tasks link to brain volume differences commonly seen in SZH. Here, for the first time, we tested associations between FreeSurfer-derived frontal brain volumes and performance on both WCST and SCWT, in a well-matched sample of 57 SZH and 32 control subjects. We also explored whether these associations were dissociable from links to symptom severity in SZH. Results revealed correlations between volumes and task performance which were unique to SZH. In SZH only, volumes of right middle frontal regions correlated with both WCST and Stroop performance: correlation coefficients were significantly different to those present in the control group, highlighting their specificity to the patient group. In the Stroop task, superior frontal regions also showed associations with Stroop interference scores which were unique to SZH. These findings provide important detail around how deficits on these two paradigmatic executive function tasks link to brain structural differences in SZH. Results align with converging evidence suggesting that neuropathology within right middle frontal regions (BA9 and BA46) might be of particular import in SZH. No volumetric associations with symptom severity were found, supporting the notion that the structural abnormalities underpinning cognitive deficits in SZH differ from those associated with symptomatology.

Cognitive insight in first-episode psychosis: Exploring the complex relationship between executive functions and social cognition

Social cognition (SC) and executive function (EF) have been described as important variables for social functioning and recovery of patients with psychosis. However, the relationship between SC and EF in first-episode psychosis (FEP) deserves further investigation, especially focusing on gender differences.

AIMS

To investigate the relationship between EF and different domains of SC in FEP patients and to explore gender differences in the relationship between these domains.

METHODS

A cross-sectional study of 191 patients with new-onset psychosis recruited from two multicenter clinical trials. A comprehensive cognitive battery was used to assess SC (Hinting Task, Face Test and IPSAQ) and EF (TMT, WSCT, Stroop Test and digit span - WAIS-III). Pearson correlations and linear regression models were performed.

RESULTS

A correlation between Theory of Mind (ToM), Emotional Recognition (ER) and EF was found using the complete sample. Separating the sample by gender showed different association profiles between these variables in women and men.

CONCLUSIONS

A relationship between different domains of SC and EF is found. Moreover, women and men presented distinct association profiles between EF and SC. These results should be considered in order to improve the treatment of FEP patients and designing personalized interventions by gender.

Are Executive Functions Deficits in Early-Onset Chronic Schizophrenia More Severe than in Adult-Onset Chronic Schizophrenia?

Objective

The research on the age of schizophrenia onset and cognitive impairments leads to contradictory conclusions. It is still unknown whether neurocognitive deficits in early-onset schizophrenia (EOS) are more intense than adulthood-onset schizophrenia (AOS). The study aimed to examine specific aspects of the executive functions of chronic outpatients with different ages of schizophrenia onset.

Method

Two clinical groups (EOS and AOS) consisted of 60 chronic outpatients with schizophrenia recruited from the community-based support system. The executive functions were measured with the Wisconsin Card Sorting Test (WCST), Trail Making Test A&B (TMT A&B), verbal fluency task (VFT), and the N-back test. Obtained results were compared to control groups consisting of 40 healthy subjects, matched with age, sex, and years of education, respectively.

Results

There were no differences in various aspects of executive dysfunctions between EOS and AOS outpatients. The outpatients in general, had lower scores than healthy controls regardless of their age of symptom onset. The most important finding suggests that some cognitive domains (visual working memory and processing speed) in presented schizophrenia patients were similar to those in healthy controls.

Despite the demographic differences, both clinical groups present the same level of executive functioning. In addition, similar to the healthy participants, the outpatients had no problems in working memory and processing speed.

Conclusions

These observations suggest that EOS might not be associated with more severe cognitive deterioration. Moreover, the stabilization or improvement of their functioning might be linked with long-term psycho-social rehabilitation and modern pharmacotherapy.

A network analysis and empirical validation of executive deficits in patients with psychosis and their healthy siblings

BACKGROUND

Psychopathological symptoms and cognitive impairment are core features of patients with psychotic disorders. Executive dysfunctions are commonly observed and typically assessed using tests like the Wisconsin Card Sorting Test (WCST). However, the structure of executive deficits remains unclear, and the underlying processes may be different. This study aimed to explore and compare the network structure of WCST measures in patients with psychosis and their unaffected siblings and to empirically validate the resulting network structure of the patients.

METHODS

The subjects were 298 patients with a DSM 5 diagnosis of a psychotic disorder and 89 of their healthy siblings. The dimensionality and network structure of the WCST were examined by means of exploratory graph analysis (EGA) and network centrality parameters.

RESULTS

The WCST network structure comprised 4 dimensions: perseveration (PER), inefficient sorting (IS), failure to maintain set (FMS) and learning (LNG). The patient and sibling groups showed a similar network structure, which was reliably estimated. PER and IS showed common and strong associations with antecedent, concurrent and outcome validators. The LNG dimension was also moderately associated with these validators, but FMS did not show significant associations.

CONCLUSIONS

Four cognitive processes underlying WCST performance were identified by the network analysis. PER, IS and LNG were associated with and shared common antecedent, concurrent and outcome validators, while FMS was not associated with external validators. These four underlying dysfunctions might help disentangle the neurofunctional basis of executive deficits in psychosis.

A Short Version of the EFECO Online Questionnaire for the Assessment of Executive Functions in School-Age Children

Executive function (EF) is a group of processes that allow individuals to be goal-oriented and to have adaptive functioning, so that adequate performance is essential for success in activities of daily living, at school and in other activities. The present study aims to create a short version of the Executive Functioning Questionnaire (EFECO) since there is a gap in the Spanish literature due to the lack of behavioural observation questionnaires at school age. A total of 3926 participants completed the online questionnaire. Subsequently, the validity and reliability of the data are analysed. The results show that the short version of the questionnaire, the EFECO-S, has a structure with five dimensions (emotional self-control, initiation, working memory, inhibition, and spatial organisation), as well as a second-order factor (global executive skill) and high reliability (ordinal Alpha = 0.68-0.88). The EFECO is composed of 67 items, while the EFECO-S has 20 items, four per factor, which turns it into a quick and easy to apply test. Therefore, it becomes an interesting alternative to be applied in screening processes with children who may be experiencing executive difficulties.

Interaction of oxidative stress and BDNF on executive dysfunction in patients with chronic schizophrenia

Executive dysfunction is increasingly recognized as one of the widely observed dimensions of cognitive impairments in the course of schizophrenia (SCZ). However, the potential molecular pathological mechanisms remain elusive. Previous studies have demonstrated that decreased brain-derived neurotrophic factor (BDNF) and oxidative damage may be associated with the psychopathology and cognitive impairment of SCZ. The present study aims to assess whether the interaction between BDNF and oxidative damage is involved in the disruption of executive function (EF) in patients with chronic SCZ. Serum BDNF and plasma oxidative stress markers were measured in 189 patients and 60 control subjects. EFs were evaluated by Wisconsin card sorting tests (WCST), Stroop word/color test (Stroop), and verbal fluency tests (VFT). The results showed that patients performed worse in the VFT, WCST and Stroop tests than healthy subjects. Moreover, patients had lower activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and lower BDNF levels, but higher malondialdehyde (MDA) levels than healthy controls. In patients, BDNF was negatively correlated with SOD (p < 0.01). For patients, catalase (CAT) activity was negatively associated with WCST error score (p = 0.02) and BDNF was positively correlated to VFT score (p = 0.02). However, all these correlations between biomarkers and EF domains did not pass Bonferroni corrections. Finally, multiple regression analyses identified BDNF × SOD activity and BDNF × MDA as influencing factors for VFT score in patients (both p < 0.05). Our results highlight the complex interplay between OS parameters and BDNF in the pathophysiology of EF impairment in SCZ, consistent with its neurodevelopmental hypothesis.

Scrutinizing Domains of Executive Function in Binge Eating Disorder: A Systematic Review and Meta-Analysis

BACKGROUND

Cognitive deficits are implicated in theoretical explanatory models for binge eating disorder (BED). Furthermore, evidence suggest that alterations in executive function may underlie symptoms in BED. The current systematic review and meta-analysis provides an update on executive functioning in individuals with BED.

METHODS

Literature searches (up to November 2019) were conducted in electronic databases combining binge eating or BED with executive functions. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines was used. Studies of any design comparing adults with BED with those without BED in executive function domains were selected. Methodological quality of studies was based on the Newcastle-Ottawa scale.

RESULTS

Of 1,983 citations identified, 28 case-control studies met inclusion criteria for this review. Six meta-analyses that examined four domains (decision-making, cognitive flexibility, inhibitory control, and working memory) were conducted. The only meta-analysis to show a significant difference in executive functioning between BED and obese controls was working memory (SMD = 0.32, 95% IC: -0.60, -0.03; p = 0.028), with an effect size of small magnitude. Qualitative inspection of the literature indicated mixed findings for control inhibition, decision making and cognitive flexibility in individuals with BED compared to controls (obese or normal weight). In addition, people with BED showed poorer problem solving performance, but similar planning abilities to obese controls.

CONCLUSIONS

Individuals with BED were found to show worse performance on working memory tasks compared to obese individuals without the disorder. The findings did not provide definitive evidence of alterations in other aspects of executive functioning. Interest in executive functioning in people with BED is increasing but is limited by insufficient data from small studies with varied methodology. Future studies should focus on using similar tests and outcome measures, in order to enable more pertinent comparisons across studies.

Interaction of BDNF and cytokines in executive dysfunction in patients with chronic schizophrenia

Multiple lines of evidence indicate that patients with chronic schizophrenia (SCZ) display executive dysfunction across the illness course. However, the potential molecular pathophysiologic mechanisms remain poorly elucidated. Neurodevelopmental changes caused by alterations of inflammatory mediators and neurotrophins have been shown to occur in the earliest stages of SCZ, and be associated with executive dysfunction (ED) in SCZ. Therefore, the current study was to investigate whether the interplay between BDNF and inflammatory mediators was involved in the disruption of executive function of long-term hospitalized patients with chronic SCZ. Serum cytokines and BDNF levels were measured in 112 long-term hospitalized patients with chronic SCZ and 44 healthy normal controls. Executive functions were assessed by verbal fluency tests (VFT), the Stroop word-color test (Stroop), and the Wisconsin card sorting tests (WCST).The results showed that the patients had higher IL-2, IL-6, IL-8, but lower TNF-α and BDNF compared to control subjects. In the patient group, BDNF was positively associated with IL-2 and IL-8 levels, while lower BDNF levels were correlated with ED measured by VFT and WCST tests. Multiple stepwise regression analyses confirmed that BDNF × IL-8 and BDNF × TNF-α were factors influencing the total score of VFT, while BDNF × IL-8 and BDNF × TNF-α were recognized as influencing factors for WCST scores. Our results suggest complex interactions between BDNF and cytokines were involved in the pathophysiology of executive function impairments in patients with SCZ.