Spanish validation of the Brief Assessment in Cognition in Schizophrenia (BACS) in patients with schizophrenia and healthy controls

Corollary discharge and anomalous self-experiences in schizophrenia and bipolar disorder: A specificity analysis

OBJECTIVE

The Corollary Discharge (CD) mechanism inhibits self-generated speech sound perception, appearing disrupted in schizophrenia and potentially contributing to Anomalous Self-Experiences (ASEs). However, it remains unclear if this alteration and its correlation with ASEs extend to other psychotic disorders.

METHODS

Electroencephalography was used to study the N1 Event-Related Potential (ERP) as an index of CD-mediated suppression in the auditory cortex across thirty-five participants with schizophrenia, twenty-six with bipolar disorder, and thirty healthy controls. Auditory N1 was elicited by two conditions: real-time listening to self-pronounced vowels while speaking through connected microphone and earphones (listen/talk -or talk condition in previous literature-) and passive listening to the same previously recorded self-uttered vowels (listen/no talk -or listen condition-).

RESULTS

N1 ERP amplitude was lower in the listen/talk condition compared to listen/no talk across all groups. However, N1 suppression was significantly reduced in schizophrenia, with bipolar patients showing intermediate attenuation between both groups (i.e., non-significantly different from controls). Furthermore, N1 suppression inversely correlated with ASEs severity only in schizophrenia.

CONCLUSIONS

Dysfunction of the CD mechanism may be a defining feature of schizophrenia, where it is connected to ASEs.

SIGNIFICANCE

These results corroborate previous findings linking auditory N1 ERP suppression with disrupted CD mechanism in schizophrenia, but not in bipolar disorder.

Corollary Discharge Dysfunction as a Possible Substrate of Anomalous Self-experiences in Schizophrenia

BACKGROUND AND HYPOTHESIS

Corollary discharge mechanism suppresses the conscious auditory sensory perception of self-generated speech and attenuates electrophysiological markers such as the auditory N1 Event-Related Potential (ERP) during Electroencephalographic (EEG) recordings. This phenomenon contributes to self-identification and seems to be altered in people with schizophrenia. Therefore, its alteration could be related to the anomalous self-experiences (ASEs) frequently found in these patients.

STUDY DESIGN

To analyze corollary discharge dysfunction as a possible substrate of ASEs, we recorded EEG ERP from 43 participants with schizophrenia and 43 healthy controls and scored ASEs with the 'Inventory of Psychotic-Like Anomalous Self-Experiences' (IPASE). Positive and negative symptoms were also scored with the 'Positive and Negative Syndrome Scale for Schizophrenia' (PANSS) and with the 'Brief Negative Symptom Scale' (BNSS) respectively. The N1 components were elicited by two task conditions: (1) concurrent listening to self-pronounced vowels (talk condition) and (2) subsequent non-concurrent listening to the same previously self-uttered vowels (listen condition).

STUDY RESULTS

The amplitude of the N1 component elicited by the talk condition was lower compared to the listen condition in people with schizophrenia and healthy controls. However, the difference in N1 amplitude between both conditions was significantly higher in controls than in schizophrenia patients. The values of these differences in patients correlated significantly and negatively with the IPASE, PANSS, and BNSS scores.

CONCLUSIONS

These results corroborate previous data relating auditory N1 ERP amplitude with altered corollary discharge mechanisms in schizophrenia and support corollary discharge dysfunction as a possible underpinning of ASEs in this illness.

Measuring Cognitive Impairments Associated With Schizophrenia in Clinical Practice: Overview of Current Challenges and Future Opportunities

BACKGROUND

Cognitive impairment associated with schizophrenia (CIAS) negatively impacts daily functioning, quality of life, and recovery, yet effective pharmacotherapies and practical assessments for clinical practice are lacking. Despite the pivotal progress made with establishment of the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) for clinical research, implementation of the full MCCB is too time-consuming and cost-ineffective for most clinicians in clinical practice.

STUDY DESIGN

Here we discuss current assessments in relation to delivery format (interview-based and performance-based), validity, ease of use for clinicians and patients, reliability/reproducibility, cost-effectiveness, and suitability for clinical implementation. Key challenges and future opportunities for improving cognitive assessments are also presented.

STUDY RESULTS

Current assessments that require 30 min to complete would have value in clinical settings, but the associated staff training and time required might preclude their application in most clinical settings. Initial profiling of cognitive deficits may require about 30 min to assist in the selection of evidence-based treatments; follow-up monitoring with brief assessments (10-15 min in duration) to detect treatment-related effects on global cognition may complement this approach. Guidance on validated brief cognitive tests for the strategic monitoring of treatment effects on CIAS is necessary.

CONCLUSIONS

With increased advancements in technology-based and remote assessments, development of validated formats of remote and in-person assessment, and the necessary training models and infrastructure required for implementation, are likely to be of increasing clinical relevance for future clinical practice.

Development and Evaluation of a Cognitive Battery for People With Schizophrenia in Ethiopia

BACKGROUND AND HYPOTHESIS

Cognitive difficulties significantly burdened people with schizophrenia (PWS). However, cognitive assessment is often unavailable in low- and middle-income counties (LMICs) due to a lack of validated and culturally adapted cognitive assessment tools. In this study, we developed and evaluated a culturally sensitive cognitive battery for PWS in Ethiopia.

STUDY DESIGN

This study was conducted in three phases. First, we selected appropriate tests through an instrument selection procedure and created a new battery. Then, we rigorously adapted the tests using culturally competent procedures, including cognitive interviewing and expert meetings. Finally, we tested the new battery in 208 PWS and 208 controls. We evaluated its psychometric properties using advanced statistical techniques, including Item Response Theory (IRT).

STUDY RESULTS

The Ethiopian Cognitive Assessment battery for Schizophrenia (ECAS) was developed from three different batteries. Participants reported tests were easy to complete, and the raters found them easy to administer. All tests had good inter-rater reliability, and the composite score had very high test-retest reliability (ICC = 0.91). One-factor structure better represented the data with excellent internal consistency (α = .81). ECAS significantly differentiated PWS from controls with 77% sensitivity and 62% specificity at a Z-score ≤0.12 cut-off value. IRT analysis suggested that the battery functions best among moderately impaired participants (difficulty between -0.06 and 0.66).

CONCLUSIONS

ECAS is a practical, tolerable, reliable, and valid assessment of cognition. ECAS can supplement current assessment tools in LAMICs for PWS and can be used to measure cognitive intervention outcomes.

Functional network properties in schizophrenia and bipolar disorder assessed with high-density electroencephalography

BACKGROUND

The study of the cortical functional network properties in schizophrenia (SZ) may benefit from the use of graph theory parameters applied to high-density electroencephalography (EEG). Connectivity Strength (CS) assesses global synchrony of the network, and Shannon Graph Complexity (SGC) summarizes the network distribution of link weights and allows distinguishing between primary and secondary pathways. Their joint use may help in understanding the underpinnings of the functional network hyperactivation and task-related hypomodulation previously described in psychoses.

METHODS

We used 64-sensor EEG recordings during a P300 oddball task in 128 SZ patients (96 chronic, CR, and 32 first episodes, FE), as well as 46 bipolar disorder (BD) patients, and 92 healthy controls (HC). Pre-stimulus and modulation (task-response minus pre-stimulus windows values) of CS and SGC were assessed in the theta band (4-8 Hz) and the broadband (4-70 Hz).

RESULTS

Compared to HC, SZ patients (CR and FE) showed significantly higher pre-stimulus CS values in the broadband, and both SZ and BD patients showed lower theta-band CS modulation. SGC modulation values, both theta-band and broadband, were also abnormally reduced in CR patients. Statistically significant relationships were found in the theta band between SGC modulation and both CS pre-stimulus and modulation values in patients. CS altered measures in patients were additionally related to their cognitive outcome and negative symptoms. A primary role of antipsychotics in these results was ruled out.

CONCLUSIONS

Our results linking SGC and CS alterations in psychotic patients supported a hyperactive and hypomodulatory network mainly involving connections in secondary pathways.

Self-report versus performance based executive functioning in people with psychotic disorders

Background

Although executive functioning is often measured using performance-based measures, these measures have their limits, and self-report measures may provide added value. Especially since these two types of measures often do not correlate with one another. It thus has been proposed they might measure different aspects of the same construct. To explore the differences between a performance-based measure of executive functioning and a self-report measure, we examined their associations in patients with a psychotic disorder with the following: other neurocognitive measures; psychotic symptoms; anxiety and depression symptoms, and daily-life outcome measures.

Method

This cross-sectional study consisted of baseline measures collected as part of a cohort study of people with a psychotic disorder (the UP'S study; n = 301). The Behavioral Rating Inventory of Executive Functioning Adult version (BRIEF-A) was used to assess self-rated executive functioning, and the Tower of London (TOL) to assess performance-based executive functioning. Generalized linear models (GLM) were used with the appropriate distribution and link function to study the associations between TOL and BRIEF-A, and the other variables, including the Brief Assessment of Cognition in Schizophrenia (BACS), the Positive and Negative Symptoms Scale-Remission (PANSS-R), the General Anxiety Disorder - 7 (GAD-7), the Patient Health Questionnaire - 9 (PHQ-9) and the WHO Disability Assessment Schedule 2.0 (WHODAS 2.0). Model selection was based on the Wald test.

Results

The TOL was associated with other neurocognitive measures, such as verbal list learning (β = 0.24), digit sequencing (β = 0.35); token motor task (β = 0.20); verbal fluency (β = 0.24); symbol coding (β = 0.43); and a screener for intelligence (β = 2.02). It was not associated with PANNS-R or WHO-DAS scores. In contrast, the BRIEF-A was associated not with other neurocognitive measures, but with the PANSS-R (β = 0.32); PHQ-9 (β = 0.52); and GAD-7 (β = 0.55); and with all the WHODAS domains: cognition domain (β = 0.54), mobility domain (β = 0.30) and selfcare domain (β = 0.22).

Conclusion

Performance-based and self-report measures of executive functioning measure different aspects of executive functioning. Both have different associations with neurocognition, symptomatology and daily functioning measures. The difference between the two instruments is probably due to differences in the underlying construct assessed.

Is brain perfusion correlated to switching mood states and cognitive impairment in bipolar disorder type I? A longitudinal study using perfusion imaging approach

Type I Bipolar disorder (BD-I) is a neuropsychiatric disorder characterized by manic or mixed-featured episodes, impaired cognitive functioning, and persistent work and social functioning impairment. This study aimed to investigate within-subject; (i) differences in brain perfusion using Single-photon emission computed tomography (SPECT) between manic and euthymic states in BD-I patients; (ii) explore potential associations between altered brain perfusion and cognitive status; and (iii) examine the relationship between cerebral perfusion and mania symptom ratings. Seventeen adult patients diagnosed with BD-I in a manic episode were recruited, and clinical assessments, cognitive tests, and brain perfusion studies were conducted at baseline (mania state) and a follow-up visit 6 months later. The results showed cognitive impairment during the manic episode, which persisted during the euthymic state at follow-up. However, no significant changes in brain perfusion were observed between the manic and euthymic states. During mania, trends toward decreased perfusion in the left cerebellum and right superior parietal lobule were noted. Additionally, trends indicated a higher perfusion imbalance in the left superior and middle frontal gyrus during mania and the right superior and middle frontal gyrus during euthymia. No significant correlations existed between brain perfusion, mania symptom ratings, and cognitive performance, indicating that symptomatology might represent more than neural hemodynamics. These findings suggest that cognitive impairment may persist in BD-I patients and highlight the need for therapeutic interventions targeting cognitive deficits. More extensive studies with extended follow-up periods are warranted further to investigate brain perfusion and cognitive functioning in BD-I patients.

Real-life outcomes in biotypes of psychotic disorders based on neurocognitive performance

Aiming at discerning potential biotypes within the psychotic syndrome, we have recently reported the possible existence of two clusters or biotypes across schizophrenia and bipolar disorder characterized by their cognitive performance using the Brief Assessment of Cognition in Schizophrenia (BACS) instrument and validated with independent biological and clinical indexes (Fernández-Linsenbarth et al. in Schizophr Res 229:102-111, 2021). In this previous work, the group with larger cognitive deficits (N = 93, including 69 chronic schizophrenia, 17 first episodes (FE) of schizophrenia and 7 bipolar disorder patients) showed smaller thalamus and hippocampus volume and hyper-synchronic electroencephalogram than the group with milder deficits (N = 105, including 58 chronic schizophrenia, 25 FE and 22 bipolar disorder patients). We predicted that if these biotypes indeed corresponded to different cognitive and biological substrates, their adaptation to real life would be different. To this end, in the present work we have followed up the patients' population included in that work at 1st and 3rd years after the date of inclusion in the 2021 study and we report on the statistical comparisons of each clinical and real-life outcomes between them. The first cluster, with larger cognitive deficits and more severe biological alterations, showed during that period a decreased capacity for job tenure (1st and 3rd years), more admissions to a psychiatric ward (1st year) and a higher likelihood for quitting psychiatric follow-up (3rd year). Patients in the second cluster, with moderate cognitive deficits, were less compliant with prescribed treatment at the 3rd year. The differences in real-life outcomes may give additional external validity to that yielded by biological measurements to the described biotypes based on neurocognition.

Cross-Cultural Adaptation and Validation of the Serbian Version of the Brief Assessment of Cognition in Schizophrenia Scale

The Brief Assessment of Cognition in Schizophrenia (BACS) scale was developed for the assessment of cognitive function in patients with schizophrenia. The objective of this study was to cross-culturally adapt and validate the BACS in to the Serbian language. The study was conducted at the Laza Lazarevic Clinic for Mental Disorders and the Clinic for Psychiatry of the University Clinical Center of Serbia from March 2021 to January 2022. The study enrolled 61 inpatients diagnosed with schizophrenia and 61 healthy controls matched for age and sex. Compared with the healthy control group, the schizophrenia patient group had worse cognitive function in all dimensions measured using BACS (p < 0.001 for all measures). The mean standardized composite BACS score was z = -2.46, and symbol coding (z = -2.54) was the most deficient function. Principal component analysis suggests a two-factor structure, where the first factor consisted of loading the measures of verbal and working memory, attention, speed of information processing, and executive function, while the second factor regarded the loading of motor speed. Cronbach's alpha coefficient demonstrated an excellent level of internal consistency (0.798). These outcomes suggest that the Serbian BACS neurocognitive battery's psychometric properties are satisfactory, with good overall discriminant validity and high internal consistency. The Serbian BACS appears to be a quick and reliable neuropsychological instrument for evaluating global cognition in schizophrenia patients in Serbia.

Schizophrenia induces abnormal frequency-dependent patterns of dynamic brain network reconfiguration during an auditory oddball task

OBJECTIVE

Schizophrenia is a psychiatric disorder that has been shown to disturb the dynamic top-down processing of sensory information. Various imaging techniques have revealed abnormalities in brain activity associated with this disorder, both locally and between cerebral regions. However, there is increasing interest in investigating dynamic network response to novel and relevant events at the network level during an attention-demanding task with high-temporal-resolution techniques. The aim of the work was: (i) to test the capacity of a novel algorithm to detect recurrent brain meta-states from auditory oddball task recordings; and (ii) to evaluate how the dynamic activation and behavior of the aforementioned meta-states were altered in schizophrenia, since it has been shown to impair top-down processing of sensory information.

APPROACH

A novel unsupervised method for the detection of brain meta-states based on recurrence plots and community detection algorithms, previously tested on resting-state data, was used on auditory oddball task recordings. Brain meta-states and several properties related to their activation during target trials in the task were extracted from electroencephalography (EEG) data from patients with schizophrenia and cognitively healthy controls.

MAIN RESULTS

The methodology successfully detected meta-states during an auditory oddball task, and they appeared to show both frequency-dependent time-locked and non-time-locked activity with respect to the stimulus onset. Moreover, patients with schizophrenia displayed higher network diversity, and showed more sluggish meta-state transitions, reflected in increased dwell times, less complex meta-state sequences, decreased meta-state space speed, and abnormal ratio of negative meta-state correlations.

SIGNIFICANCE

Abnormal cognition in schizophrenia is also reflected in decreased brain flexibility at the dynamic network level, which may hamper top-down processing, possibly indicating impaired decision-making linked to dysfunctional predictive coding. Moreover, the results showed the ability of the methodology to find meaningful and task-relevant changes in dynamic connectivity and pathology-related group differences.

European Psychiatric Association guidance on assessment of cognitive impairment in schizophrenia

Background

Impairment in a wide range of cognitive abilities has been consistently reported in individuals with schizophrenia. Both neurocognitive and social cognitive deficits are thought to underlie severe functional disabilities associated with schizophrenia. Despite the key role in schizophrenia outcome, cognition is still poorly assessed in both research and clinical settings.

Methods

In this guidance paper, we provide a systematic review of the scientific literature and elaborate several recommendations for the assessment of cognitive functions in schizophrenia both in research settings and in real-world clinical practice.

Results

Expert consensus and systematic reviews provided guidance for the optimal assessment of cognitive functions in schizophrenia. Based on the reviewed evidence, we recommend a comprehensive and systematic assessment of neurocognitive and social cognitive domains in schizophrenia, in all phases of the disorder, as well as in subjects at risk to develop psychosis. This European Psychiatric Association guidance recommends not only the use of observer reports but also self-reports and interview-based cognitive assessment tools. The guidance also provides a systematic review of the state of the art of assessment in the first episode of psychosis patients and in individuals at risk for psychosis.

Conclusion

The comprehensive review of the evidence and the recommendations might contribute to advance the field, allowing a better cognitive assessment, and avoiding overlaps with other psychopathological dimensions. The dissemination of this guidance paper may promote the development of shared guidelines concerning the assessment of cognitive functions in schizophrenia, with the purpose to improve the quality of care and to obtain recovery.

Event-related potentials associated to N-back test performance in schizophrenia

Mapping of Event-Related Potentials (ERP) associated with auditory and visual odd-ball paradigms has shown consistent differences between healthy controls and schizophrenia patients. It may be hypothesized that higher task attentional/cognitive demand will result in larger differences in these paradigms, which may help understanding the substrates of cognitive deficits in this syndrome. To this aim, we performed an EEG study comparing the effects of increasing the attentional/cognitive load of an auditory N-back task on the Event-Related Potential in 50 subjects with schizophrenia (11 first episodes) and 35 healthy controls. We considered a post-target window of 1000 ms to explore possible between groups differences in N100, P300, and Late Slow Wave (LSW), and compared these components between 0-back ('lower attentional/cognitive load) and 1-back ('higher attentional/cognitive load') conditions. Our results showed that N100 and LSW amplitude increase from 0- to 1-back condition was significantly larger in healthy controls compared to schizophrenia patients. Furthermore, LSW amplitude difference between 0- and 1-back conditions positively correlated with performance in the behavioral cognitive assessment. Taken together, these results support that higher task attentional/cognitive load (0-back vs. 1-back condition) increase N100 amplitude differences and reveal new findings related to the LSW component in schizophrenia.

Search for schizophrenia and bipolar biotypes using functional network properties

INTRODUCTION

Recent studies support the identification of valid subtypes within schizophrenia and bipolar disorder using cluster analysis. Our aim was to identify meaningful biotypes of psychosis based on network properties of the electroencephalogram. We hypothesized that these parameters would be more altered in a subgroup of patients also characterized by more severe deficits in other clinical, cognitive, and biological measurements.

METHODS

A clustering analysis was performed using the electroencephalogram-based network parameters derived from graph-theory obtained during a P300 task of 137 schizophrenia (of them, 35 first episodes) and 46 bipolar patients. Both prestimulus and modulation of the electroencephalogram were included in the analysis. Demographic, clinical, cognitive, structural cerebral data, and the modulation of the spectral entropy of the electroencephalogram were compared between clusters. Data from 158 healthy controls were included for further comparisons.

RESULTS

We identified two clusters of patients. One cluster presented higher prestimulus connectivity strength, clustering coefficient, path-length, and lower small-world index compared to controls. The modulation of clustering coefficient and path-length parameters was smaller in the former cluster, which also showed an altered structural connectivity network and a widespread cortical thinning. The other cluster of patients did not show significant differences with controls in the functional network properties. No significant differences were found between patients´ clusters in first episodes and bipolar proportions, symptoms scores, cognitive performance, or spectral entropy modulation.

CONCLUSION

These data support the existence of a subgroup within psychosis with altered global properties of functional and structural connectivity.

Four-subtest short-form of the WAIS-IV for assessment of patients diagnosed with schizophrenia

INTRODUCTION

The present study aimed to obtain a short form of the Spanish version of the WAIS-IV for patients diagnosed with schizophrenia that requires about half an hour to be administered. The reduced test can be very useful in clinical and research settings when an estimation of the intelligence quotient (IQ) is required to decide about intervention programs or to describe the sample.

MATERIALS AND METHODS

A sample of 143 patients participated in the study, 91 out of them were the test group, and the other 52 were used for a cross-validation analysis. To increase the content validity, the decision was made to create a short form composed of a subtest of each of the four cognitive domains that the scale measures.

RESULTS

Several analyses showed that the best combination was composed of the Information, Block Design, Arithmetic, and Symbol Search subtests. Nine different criteria were calculated to evaluate the quality of the short form.

CONCLUSIONS

The data showed very good results for the criteria: correlations, difference of means, and cross-validation. The results were satisfactory for: category agreement, band of error, clinical accuracy, and reliability.

Anomalous self-experiences are related to general cognition deficits in schizophrenia

Anomalous self-experiences (ASEs) are prevalent in schizophrenia, but its underpinnings are not completely understood. Given the likely complex substrate of the experience of the self, neurocognitive functions requiring coordinate cerebral activity may relate to ASEs. Moreover, cognitive deficits functioning may be involved in the link between self-experience disturbances and some aspects of social dysfunction in schizophrenia. We have assessed ASEs in 41 schizophrenia patients (11 first episodes) using the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE), and the general cognition using the Brief Assessment of Cognition in Schizophrenia (BACS). Besides, social cognition was assessed using two complementary tools Meyer, Salovey and Caruso Emotional Intelligence Test (MSCEIT) and GEOPTE (Grupo Español para la Optimización del Tratamiento de la Esquizofrenia). The results revealed that Self-awareness/presence and Somatization IPASE scores were inversely explained by motor speed in the BACS; Consciousness IPASE scores were inversely explained by problem solving performance in the BACS. These data reveal a significant relationship between certain domains of general cognition and anomalous self-experiences, that may be useful in further investigation on the substrates of ASEs.

Cross-cultural adaptation and validation of the Arabic version of the BACS scale (the brief assessment of cognition in schizophrenia) among chronic schizophrenic inpatients

BACKGROUND

Assessment of cognitive disorders in schizophrenia is becoming a part of clinical and research practice by using batteries that differ widely in their content. The Brief Assessment of Cognition in Schizophrenia (BACS) was developed to cover the main cognitive deficits of schizophrenia. The objective of this study was to assess concurrent validity of the Arabic version of the BACS with a standard neurocognitive battery of tests in Lebanese patients with schizophrenia and healthy controls.

METHODS

A sample of 120 stable inpatients diagnosed with schizophrenia and 60 healthy controls received the Arabic version of the BACS in a first session, and a standard battery in a second session.

RESULTS

Mean duration of completion for the BACS was 31.2 ± 5.4 min in patients with schizophrenia. All tests demonstrated significant differences between controls and patients (p < .01). Principal components analysis demonstrated that a one-factor solution best fits our dataset (64.8% of the variance). High Cronbach alpha was found (.85). The BACS composite scores were significantly correlated with the standard battery composite scores in patients (r = .73, p < .001) and healthy controls (r = .78, p < .001). Also, correlation analysis between the BACS sub-scores and the standard battery sub-scores showed significant results (p < .05).

CONCLUSION

Results showed that the Arabic version of the BACS demonstrated high ability to discriminate patients with schizophrenia from healthy controls and it is a useful tool for assessing cognition in patients with schizophrenia and could be used in clinical practice in Lebanon.

Neurobiological underpinnings of cognitive subtypes in psychoses: A cross-diagnostic cluster analysis

Schizophrenia and bipolar disorder include patients with different characteristics, which may hamper the definition of biomarkers. One of the dimensions with greater heterogeneity among these patients is cognition. Recent studies support the identification of different patients' subgroups along the cognitive domain using cluster analysis. Our aim was to validate clusters defined on the basis of patients' cognitive status and to assess its relation with demographic, clinical and biological measurements. We hypothesized that subgroups characterized by different cognitive profiles would show differences in an array of biological data. Cognitive data from 198 patients (127 with chronic schizophrenia, 42 first episodes of schizophrenia and 29 bipolar patients) were analyzed by a K-means cluster approach and were compared on several clinical and biological variables. We also included 155 healthy controls for further comparisons. A two-cluster solution was selected, including a severely impaired group and a moderately impaired group. The severely impaired group was associated with higher illness duration and symptoms scores, lower thalamus and hippocampus volume, lower frontal connectivity and basal hypersynchrony in comparison to controls and the moderately impaired group. Moreover, both patients' groups showed lower cortical thickness and smaller functional connectivity modulation than healthy controls. This study supports the existence of different cognitive subgroups within the psychoses with different neurobiological underpinnings.

Deficits of entropy modulation of the EEG: A biomarker for altered function in schizophrenia and bipolar disorder?

BACKGROUND

The synchronized activity of distributed neural assemblies — reflected in the electroencephalogram (EEG) — underpins mental function. In schizophrenia, modulation deficits of EEG spectral content during a P300 task have been replicated. The effects of treatment, chronicity and specificity in these deficits and their possible relationship with anatomic connectivity remain to be explored.

METHODS

We assessed spectral entropy modulation of the EEG during a P300 task in 79 patients with schizophrenia (of those, 31 werein their first episode), 29 patients with bipolar disorder and 48 healthy controls. Spectral entropy values summarize EEG characteristics by quantifying the irregularity of spectral content. In a subsample, we calculated the network architecture of structural connectivity using diffusion tensor imaging and graph-theory parameters.

RESULTS

We found significant spectral entropy modulation deficits with task performance in patients with chronic or first-episode schizophrenia and in patients with bipolar disorder, without significant pre-stimulus spectral entropy differences. The deficits were unrelated to treatment doses, and spectral entropy modulation did not differ between patients taking or not taking antipsychotics, lithium, benzodiazepines or antidepressants. Structural connectivity values were unrelated to spectral entropy modulation. In patients with schizophrenia, spectral entropy modulation was inversely related to negative symptoms and directly related to verbal memory.

LIMITATIONS

All patients were taking medication. Patients with bipolar disorder were euthymic and chronic. The cross-sectional nature of this study prevented a more thorough analysis of state versus trait criteria for spectral entropy changes.

CONCLUSION

Spectral entropy modulation with task performance is decreased in patients with schizophrenia and bipolar disorder. This deficit was not an effect of psychopharmacological treatment or structural connectivity and might reflect a deficit in the synchronization of the neural assemblies that underlie cognitive activity.

Identificacion of MRI-based psychosis subtypes: Replication and refinement

The identification of the cerebral substrates of psychoses such as schizophrenia and bipolar disorder is likely hampered by its biological heterogeneity, which may contribute to the low replication of results in the field. In this study we aimed to replicate in a completely new sample and supplement the results of a previous study with additional data on this topic. In the aforementioned study we identified a schizophrenia cluster characterized by high mean cortical curvature and low cortical thickness, subcortical hypometabolism and progressive negative symptoms. Here, we have used magnetic resonance images from 61 schizophrenia and 28 bipolar patients, as well as 51 healthy controls and a cluster analysis to search for possible subgroups primarily characterized by cerebral structural data. Diffusion tensor imaging (fractional anisotropy, FA), cognition, clinical data and electroencephalographic (EEG) modulation during a P300 task were used to validate the possible clusters. Two clusters of patients were identified. The first cluster (29 schizophrenia and 18 bipolar patients) showed decreased cortical thickness and area values, as well as lower subcortical volumes and higher cortical curvature in some regions, as compared to the second cluster. This first cluster also showed decreased FA in frontal lobe connections and worse cognitive performance. Although this cluster also showed longer illness duration, there were first episode patients in both clusters and treatment doses and types were not different between clusters. Both clusters of patients showed decreased EEG task-related modulation. In conclusion, our data give additional support to a distinct biologically based cluster encompassing schizophrenia and bipolar disorder patients with cortical and subcortical alterations, hampered cortical connectivity and lower cognitive performance.

Connectivity strength of the EEG functional network in schizophrenia and bipolar disorder

The application of graph theory measures in the study of functional brain networks allows for the description of their general properties and their alterations in mental illness. Among these measures, connectivity strength (CS) estimates the degree of functional connectivity of the whole network. Previous studies in schizophrenia patients have reported higher baseline CS values and modulation deficits in EEG spectral properties during cognitive activity. The specificity of these alterations and their relationships with pharmacological treatments remain unknown. Therefore, in the present study, we assessed functional CS on EEG-based brain networks in 79 schizophrenia and 29 bipolar patients in addition to 63 healthy controls. The subjects performed a P300 task during the EEG recordings from which the pre-stimulus and the task-related modulation CS values were computed in the global and theta bands. These values were compared between the groups and between the patients who had and had not received different treatments. The global band pre-stimulus CS was significantly higher in the schizophrenia group compared with the bipolar and control groups. Theta band CS modulation was decreased in schizophrenia and bipolar patients. Treatment with antipsychotics, lithium, benzodiazepines, and anticonvulsants did not significantly alter these CS values. The first-episode and chronic schizophrenia patients did not show significant differences in CS values. Higher global band pre-stimulus CS values were associated with worse general cognition in schizophrenia patients. These data support increased connectivity in the whole-brain network that is specific to schizophrenia and suggest a general hyper-synchronized basal state that might hamper cognition in this syndrome.

Four-subtest short-form of the WAIS-IV for assessment of patients diagnosed with schizophrenia

INTRODUCTION

The present study aimed to obtain a short form of the Spanish version of the WAIS-IV for patients diagnosed with schizophrenia that requires about half an hour to be administered. The reduced test can be very useful in clinical and research settings when an estimation of the intelligence quotient is required to decide about intervention programmes or to describe the sample.

MATERIALS AND METHODS

A sample of 143 patients participated in the study, 91 out of them were the test group, and the other 52 were used for a cross-validation analysis. To increase the content validity, the decision was made to create a short form composed of a subtest of each of the four cognitive domains that the scale measures.

RESULTS

Several analyses showed that the best combination was composed of the Information, Block Design, Arithmetic, and Symbol Search subtests. Nine different criteria were calculated to evaluate the quality of the short form.

CONCLUSIONS

The data showed very good results for the criteria: correlations, difference of means, and cross-validation. The results were satisfactory for: category agreement, band of error, clinical accuracy, and reliability.

Social cognition in psychosis: Predictors and effects of META-cognitive training

Social cognition deficits are found in schizophrenia and bipolar disorder, but its neural underpinnings are poorly understood. Given the complexity of psychological functions underlying this kind of cognition, we hypothesized that alterations in global structural connectivity could contribute to those deficits. To test this hypothesis, we studied a group of schizophrenia and bipolar patients with connectomics based on diffusion magnetic resonance imaging and assessments of general and social cognition. The latter was assessed using the Mayer, Salovey and Caruso Emotional Intelligence Test (MSCEIT) for emotional intelligence and the Spanish Group for Schizophrenia Treatment Optimization (Grupo Español para la OPtimización del Tratamiento de la Esquizofrenia, GEOPTE) test for behavioral aspects of social cognition. Graph theory applied to fractional anisotropy for the connections among cortical regions was used to obtain the small-world (SW) index of the structural connectivity network. In addition, we assessed the possibility of predicting the response of social cognition deficits to Meta-cognitive Training based on their possible underpinnings in a subgroup of patients. Patients showed lower scores in emotional intelligence and behavioral social cognition. MSCEIT scores were associated with SW index and working memory, and GEOPTE scores were related to verbal memory. Improvement in social cognition after Meta-cognitive Training was associated with lower scores of the social cognition in the baseline, according to the GEOPTE scale. Our findings support structural connectivity as one of the factors underlying emotional intelligence in schizophrenia, and the use of Meta-cognitive Training to improve social cognition in patients with larger deficits.

Structural connectivity in schizophrenia and bipolar disorder: Effects of chronicity and antipsychotic treatment

Previous studies based on graph theory parameters applied to diffusion tensor imaging support an alteration of the global properties of structural connectivity network in schizophrenia. However, the specificity of this alteration and its possible relation with chronicity and treatment have received small attention. We have assessed small-world (SW) and connectivity strength indexes of the structural network built using fractional anisotropy values of the white matter tracts connecting 84 cortical and subcortical regions in 25 chronic and 18 first episode (FE) schizophrenia and 24 bipolar patients and 28 healthy controls. Chronic schizophrenia and bipolar patients showed significantly smaller SW and connectivity strength indexes in comparison with controls and FE patients. SW reduction was driven by increased averaged path-length (PL) values. Illness duration but not treatment doses were negatively associated with connectivity strength, SW and PL in patients. Bipolar patients exposed to antipsychotics did not differ in SW or connectivity strength from bipolar patients without such an exposure. Executive functions and social cognition were related to SW index in the schizophrenia group. Our results support a role for chronicity but not treatment in structural network alterations in major psychoses, which may not differ between schizophrenia and bipolar disorder, and may hamper cognition.

The brief assessment of cognition in affective disorders: Normative data for the Italian population

BACKGROUND

To date there are no validated tests in Italian to assess cognitive functions in Bipolar Disorder. Therefore, this study aimed to provide normative data for the Italian version of the Brief Assessment of Cognition in Affective Disorders (BAC-A), a battery targeting neuro- and affective-cognition in affective disorders.

METHODS

Data were collected from 228 healthy participants (age range: 18-67; mean age: 34.68 ± 12.15 years) across eight recruiting sites. The influence of age, sex and education was measured and adjusted for using multivariate stepwise regression models. Normative values were established by means of the Equivalent Score approach.

RESULTS

Most of the BAC-A subtests showed patterns of association with age (inversely associated with overall cognitive performance), education (positively associated with Verbal Memory and Fluency, Digit Sequencing and Affective Processing subtests) and sex (females performed better than males in the Affective Interference Test but worse in the Emotion Inhibition Task, Digit Sequencing and Tower of London).

LIMITATIONS

The sample size was not sufficiently large for developing stratified norms, using 10-years ranges. Moreover, the participants included in the study were, on average, highly educated.

CONCLUSIONS

The normative data of the BAC-A provided in this study can serve as a cognitive functioning reference for Italian-speaking participants within the age range of the study sample. This can increase the applicability of this test in both clinical and research settings. The reliability and validity of the Italian BAC-A need to be further investigated.

Topography of activation deficits in schizophrenia during P300 task related to cognition and structural connectivity

BACKGROUND

The study of cerebral underpinnings of schizophrenia may benefit from the high temporal resolution of electromagnetic techniques, but its spatial resolution is low. However, source imaging approaches such as low-resolution brain electromagnetic tomography (LORETA) allow for an acceptable compromise between spatial and temporal resolutions.

METHODS

We combined LORETA with 32 channels and 3-Tesla diffusion magnetic resonance (Dmr) to study cerebral dysfunction in 38 schizophrenia patients (17 first episodes, FE), compared to 53 healthy controls. The EEG was acquired with subjects performing an odd-ball task. Analyses included an adaptive window of interest to take into account the interindividual variability of P300 latency. We compared source activation patters to distractor (P3a) and target (P3b) tones within- and between-groups.

RESULTS

Patients showed a reduced activation in anterior cingulate and lateral and medial prefrontal cortices, as well as inferior/orbital frontal regions. This was also found in the FE patients alone. The activation was directly related to IQ in the patients and controls and to working memory performance in controls. Symptoms were unrelated to source activation. Fractional anisotropy in the tracts connecting lateral prefrontal and anterior cingulate regions predicted source activation in these regions in the patients.

CONCLUSIONS

These results replicate the source activation deficit found in a previous study with smaller sample size and a lower number of sensors and suggest an association between structural connectivity deficits and functional alterations.

Altered predictive capability of the brain network EEG model in schizophrenia during cognition

The study of the mechanisms involved in cognition is of paramount importance for the understanding of the neurobiological substrates in psychiatric disorders. Hence, this research is aimed at exploring the brain network dynamics during a cognitive task. Specifically, we analyze the predictive capability of the pre-stimulus theta activity to ascertain the functional brain dynamics during cognition in both healthy and schizophrenia subjects. Firstly, EEG recordings were acquired during a three-tone oddball task from fifty-one healthy subjects and thirty-five schizophrenia patients. Secondly, phase-based coupling measures were used to generate the time-varying functional network for each subject. Finally, pre-stimulus network connections were iteratively modified according to different models of network reorganization. This adjustment was applied by minimizing the prediction error through recurrent iterations, following the predictive coding approach. Both controls and schizophrenia patients follow a reinforcement of the secondary neural pathways (i.e., pathways between cortical brain regions weakly connected during pre-stimulus) for most of the subjects, though the ratio of controls that exhibited this behavior was statistically significant higher than for patients. These findings suggest that schizophrenia is associated with an impaired ability to modify brain network configuration during cognition. Furthermore, we provide direct evidence that the changes in phase-based brain network parameters from pre-stimulus to cognitive response in the theta band are closely related to the performance in important cognitive domains. Our findings not only contribute to the understanding of healthy brain dynamics, but also shed light on the altered predictive neuronal substrates in schizophrenia.

Parkinsonism is associated to fronto-caudate disconnectivity and cognition in schizophrenia

The present work studies the possible relation of parkinsonism and fronto-caudate dysconnectivity, as well as its relation to cognition in schizophrenia patients. We assessed parkinsonism using Simpson-Angus scale and prefronto-caudate connectivity using diffusion magnetic resonance in 22 schizophrenia patients (11 first-episodes) and 14 healthy controls. Fractional anisotropy was calculated for the white matter tracts directly linking rostral middle prefrontal (RMPF) and superior medial prefrontal (SMPF) regions with caudate nucleus. Cognition was assessed using the Brief Assessment of Cognition in Schizophrenia Scale (BACS). Total parkinsonism scores were negatively related to fractional anisotropy in the right SMPF-caudate tract in patients, which was also found in the first-episode patients alone, but not in controls. Parkinsonism was also inversely associated in patients to performance in social cognition, verbal memory, working memory and performance speed tests. In conclusion, our data support the involvement of fronto-striatal dysconnectivity in parkinsonism in schizophrenia.

The Chinese Version of the Brief Assessment of Cognition in Schizophrenia: Data of a Large-Scale Mandarin-Speaking Population

Objective

The Brief Assessment of Cognition in Schizophrenia (BACS) is a cognitive assessment tool used to measure the broad aspects of cognition that are most frequently impaired in patients with schizophrenia. This study aims to develop the normative data of the Chinese version of the BACS among the Mandarin-speaking population.

Method

This cross-sectional study included 382 healthy participants (age range: 19-79 years; mean age: 48.0 ± 16.7 years, 47.6% men) in Taiwan, who were evaluated with the BACS. Means and standard deviations of subtests and composite scores were arranged by age group and gender. The Z-scores calculated based on the U.S. norms were compared to our scores based on the norms established in this study.

Results

The raw scores of all the BACS tests (verbal memory, digit sequencing, token motor test, verbal fluency, symbol coding, and Tower of London) were negatively correlated with participants' age. Women were superior to men in verbal memory, but inferior to them in executive function. Furthermore, applying the U.S. norms of the BACS to determine the performance of the Chinese BACS results in bias with regard to verbal memory, token motor test, verbal fluency, symbol coding, Tower of London and composite score.

Conclusions

These findings demonstrate that directly applying western cognitive norms to a Mandarin-speaking population can cause biased interpretations. The results of this study can be an important reference for clinical settings and research related to cognitive assessments in Mandarin-speaking Chinese populations.

Deficit of entropy modulation of the EEG in schizophrenia associated to cognitive performance and symptoms. A replication study

Spectral entropy (SE) is a measurement from information theory field that provides an estimation of EEG regularity and may be useful as a summary of its spectral properties. Previous studies using small samples reported a deficit of EEG entropy modulation in schizophrenia during cognitive activity. The present study is aimed at replicating this finding in a larger sample, to explore its cognitive and clinical correlates and to discard antipsychotic treatment as the main source of that deficit. We included 64 schizophrenia patients (21 first episodes, FE) and 65 healthy controls. We computed SE during performance of an odd-ball paradigm, at the windows prior (-300 to 0ms) and following (150 to 450ms) stimulus presentation. Modulation of SE was defined as the difference between post- and pre-stimulus windows. In comparison to controls, patients showed a deficit of SE modulation over frontal and central regions, also shown by FE patients. Baseline SE did not differ between patients and controls. Modulation deficit was directly associated with cognitive deficits and negative symptoms, and inversely with positive symptoms. SE modulation was not related to antipsychotic doses. Patients also showed a smaller change of median frequency (i.e., smaller slowing of oscillatory activity) of the EEG from pre- to post-stimulus windows. These results support that a deficit of fast modulation contributes to cognitive deficits and symptoms in schizophrenia patients.

Relations between structural and EEG-based graph metrics in healthy controls and schizophrenia patients

Our aim was to assess structural and functional networks in schizophrenia patients; and the possible prediction of the latter based on the former. The possible dependence of functional network properties on structural alterations has not been analyzed in schizophrenia. We applied averaged path-length (PL), clustering coefficient, and density (D) measurements to data from diffusion magnetic resonance and electroencephalography in 39 schizophrenia patients and 79 controls. Functional data were collected for the global and theta frequency bands during an odd-ball task, prior to stimulus delivery and at the corresponding processing window. Connectivity matrices were constructed from tractography and registered cortical segmentations (structural) and phase-locking values (functional). Both groups showed a significant electroencephalographic task-related modulation (change between prestimulus and response windows) in the global and theta bands. Patients showed larger structural PL and prestimulus density in the global and theta bands, and lower PL task-related modulation in the theta band. Structural network values predicted prestimulus global band values in controls and global band task-related modulation in patients. Abnormal functional values found in patients (prestimulus density in the global and theta bands and task-related modulation in the theta band) were not predicted by structural data in this group. Structural and functional network abnormalities respectively predicted cognitive performance and positive symptoms in patients. Taken together, the alterations in the structural and functional theta networks in the patients and the lack of significant relations between these alterations, suggest that these types of network abnormalities exist in different groups of schizophrenia patients.

Deficits of entropy modulation in schizophrenia are predicted by functional connectivity strength in the theta band and structural clustering

Spectral entropy (SE) allows comparing task-related modulation of electroencephalogram (EEG) between patients and controls, i.e. spectral changes of the EEG associated to task performance. A SE modulation deficit has been replicated in different schizophrenia samples. To investigate the underpinnings of SE modulation deficits in schizophrenia, we applied graph-theory to EEG recordings during a P300 task and fractional anisotropy (FA) data from diffusion tensor imaging in 48 patients (23 first episodes) and 87 healthy controls. Functional connectivity was assessed from phase-locking values among sensors in the theta band, and structural connectivity was based on FA values for the tracts connecting pairs of regions. From those data, averaged clustering coefficient (CLC), characteristic path-length (PL) and connectivity strength (CS, also known as density) were calculated for both functional and structural networks. The corresponding functional modulation values were calculated as the difference in SE and CLC, PL and CS between the pre-stimulus and response windows during the task. The results revealed a higher functional CS in the pre-stimulus window in patients, predictive of smaller modulation of SE in this group. The amount of increase in theta CS from pre-stimulus to response related to SE modulation in patients and controls. Structural CLC was associated with SE modulation in the patients. SE modulation was predictive of negative symptoms, whereas CLC and PL modulation was associated with cognitive performance in the patients. These results support that a hyperactive functional connectivity and/or structural connective deficits in the patients hamper the dynamical modulation of connectivity underlying cognition.

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Functional connectivity strength and structural clustering properties were associated to the deficit in SE modulation in schizophrenia.

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Functional connectivity strength in the theta band was larger in the baseline in the patients.

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A hyperactive pre-stimulus state hampers the capacity for adequately modulating neural activity across the brain in schizophrenia.

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The possible basis for that problem may be investigated to identify therapeutic targets.

Biological and cognitive correlates of cortical curvature in schizophrenia

Mean cortical curvature may relate to cortico-cortical connections integrity. We explored the association between prefrontal (PFC) cortical curvature and fractional anisotropy (FA) values for tracts connecting PFC and relevant cortical regions. In schizophrenia Anatomical and diffusion magnetic resonance images were obtained from 34 patients (16 of them first-episodes) and 32 healthy controls. We calculated curvature at rostral lateral prefrontal (RLPF) and superior medial prefrontal (SMPF) areas and mean FA for the tracts respectively connecting RLPF and SMPF areas with anterior caudal cingulate (ACC), superior temporal gyrus (STG) and superior parietal SP regions. Cognitive and clinical data were collected, including baseline symptoms, Clinical Global Impression change scores from baseline to follow-up, illness duration and treatment dosage. Patients showed significantly lower FA values in the tracts linking right RLPF-ACC, right SMPF-SPG and bilaterally PFC-STG. FA values in short-range cortico-cortical connections (linking PFC and ACC) were inversely associated with PFC curvature. In patients, cognitive performance was negatively associated with PFC curvature. Larger curvature values were associated to lack of clinical improvement at follow-up. We conclude that cortical curvature is influenced by integrity in short-range cortico-cortical connections and relates to cognition and clinical outcome in schizophrenia patients.

Patients with schizophrenia activate behavioural intentions facilitated by counterfactual reasoning

METHOD

The main variables assessed were: answer to complete a target task (wrong or correctly), and percentage gain in the reaction time (RT) to complete a target task correctly depending on whether the prime was a counterfactual or a neutral-control cue. These variables were assessed in 37 patients with schizophrenia and 37 healthy controls. Potential associations with clinical status and socio-demographic characteristics were also explored.

RESULTS

When a counterfactual prime was presented, the probability of giving an incorrect answer was lower for the entire sample than when a neutral prime was presented (OR 0.58; CI 95% 0.42 to 0.79), but the schizophrenia patients showed a higher probability than the controls of giving an incorrect answer (OR 3.89; CI 95% 2.0 to 7.6). Both the schizophrenia patients and the controls showed a similar percentage gain in RT to a correct answer of 8%.

CONCLUSIONS

Challenging the results of previous research, our findings suggest a normal activation of behavioural intentions facilitated by CFT in schizophrenia. Nevertheless, the patients showed more difficulty than the controls with the task, adding support to the concept of CFT as a potential new target for consideration in future therapeutic approaches for this illness.

Functional EEG network analysis in schizophrenia: Evidence of larger segregation and deficit of modulation

OBJECTIVE

Higher mental functions depend on global cerebral functional coordination. Our aim was to study fast modulation of functional networks in schizophrenia that has not been previously assessed.

METHODS

Graph-theory was used to analyze the electroencephalographic (EEG) activity during an odd-ball task in 57 schizophrenia patients (18 first episode patients, FEPs) and 59 healthy controls. Clustering coefficient (CLC), characteristic path length (PL) and small-worldness (SW) were computed at baseline ([-300 0] ms prior to stimulus delivery) and response ([150 450] ms post-stimulus) windows. Clinical and cognitive assessments were performed.

RESULTS

CLC, PL and SW showed a significant modulation between baseline and response in controls but not in patients. Patients obtained higher CLC and SW at baseline, lower CLC and higher PL at response, and diminished modulation of CLC and SW as compared to controls. In patients, CLC and SW modulation were inversely associated to cognitive performance in executive tasks and directly associated to working memory. Similar patterns were observed in FEPs. CLC and SW during the baseline were inversely associated to their respective modulation magnitudes.

CONCLUSIONS

Our results are coherent with a hyper-segregated network at baseline (higher CLC) and a decreased modulation of the functional connectivity during cognition in schizophrenia.

Alterations in prefrontal connectivity in schizophrenia assessed using diffusion magnetic resonance imaging

BACKGROUND

Spatial and biological characteristics of structural frontal disconnectivity in schizophrenia remain incompletely understood. Simultaneous streamline count (SC) and fractional anisotropy (FA) analyses may yield relevant complementary information to this end.

METHODS

Using 3T diffusion magnetic resonance imaging both SC and FA were calculated for the tracts linking lateral and medial subregions of prefrontal cortex (PFC) to cingulate, hippocampus, caudate and thalamus in 27 schizophrenia patients (14 first-episodes) and 27 controls. Relationships of these parameters with cognition, symptoms, treatment doses and illness duration were assessed where significant between-groups differences were detected.

RESULTS

Patients showed lower SC and FA in the tracts linking lateral and medial PFC to thalamus (likely corresponding to anterior thalamic peduncle) and lower FA in those linking PFC to caudate (likely through internal capsule), right caudal anterior cingulate and left hippocampus (likely corresponding to hippocampal-prefrontal pathway). Moreover, patients showed greater SC values for the tracts linking medial PFC and left caudal anterior cingulate. SC and FA values for the tracts linking PFC and caudal anterior cingulate were positively related to motor speed, executive function, problem solving and completed categories in WCST. FA for the tract linking right lateral PFC and caudate was directly related to positive symptoms and FA for the tract linking left medial PFC and left thalamus was inversely related to negative symptoms. Treatment doses were not associated with SC or FA values in any tract. Illness duration was negatively associated with SC and FA in the tracts linking PFC and subcortical areas.

CONCLUSIONS

Widespread alterations in frontal structural connectivity of PFC can be found in schizophrenia, and are related to cognition, symptoms and illness duration.

Possible Facilitative Effects of Repeated Anodal Transcranial Direct Current Stimulation on Functional Outcome 1 Month Later in Schizophrenia: An Open Trial

Recent research on neuromodulation techniques, such as transcranial direct current stimulation (tDCS), for the treatment of schizophrenia has mainly focused on psychotic symptoms. We aimed to determine whether repetitive tDCS is efficacious in improving determinants of outcome, such as cognitive function, daily living skills, and depressive mood in patients with schizophrenia. Twenty-eight patients underwent tDCS (2 mA × 20 min) two times per day for 5 consecutive days. The anodal electrode was placed over the left dorsolateral prefrontal cortex while the cathodal electrode was placed over the right supraorbital region. One month after the last stimulation, there was a significant improvement on cognitive function, measured by the brief assessment of cognition in schizophrenia (d = 0.49). Significant effects were also shown on daily living skills (functional capacity), measured by the UCSD performance-based skills assessment-brief (d = 0.70). Depressive symptoms, measured by the Calgary depression rating scale, as well as psychotic symptoms measured by on the positive and negative syndrome scale positive and general psychopathology subscales also responded to the treatment (d = 0.38, d = 0.48, and d = 0.50, respectively). This is the first study to suggest that tDCS with the anodal electrode on the left prefrontal cortex improves functional capacity and depressive symptoms in patients with schizophrenia. These results may add to the concept that tDCS provides a strategy to enhance functional outcomes in patients with schizophrenia.

TRIAL REGISTRATION

https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000018556, UMIN000015953.

Association between electroencephalographic modulation, psychotic-like experiences and cognitive performance in the general population

AIM

An association between deficit of electroencephalographic (EEG) modulation during an odd-ball task and psychotic symptoms has been described in clinical samples, in agreement with the proposed role for altered salience in psychosis. To discard the possible influence of medication, the relationship between psychotic-like experiences and EEG modulation in the general population was explored.

METHODS

EEG and psychotic-like experiences were assessed in 194 healthy subjects during a P300 paradigm. EEG modulation was assessed as changes from pre-stimulus to response windows in spectral entropy (SE, a measurement of signal irregularity), median frequency (MF, a quantifier of the frequency distribution of oscillatory activity) and theta, alpha, beta-1, beta-2 and gamma relative power (RP, a summary of the distribution of spectral components).

RESULTS

A significant widespread decrease in SE and MF from baseline to response was found, with a significant increase in RP for theta and a decrease for higher frequency bands, supporting an increase in EEG regularity and a slowing of brain oscillations during the response. Furthermore, a significant association was found between SE modulation and distress of negative psychotic-like experiences, as well as between verbal memory and RP modulation for beta-1. Performance in verbal fluency was associated with the increase in theta RP during the response.

CONCLUSION

EEG irregularity of healthy subjects decreased at the expense of a larger contribution of theta RP and a decreased contribution of fast frequency bands. Subjects with smaller modulation showed poorer cognitive scores and greater distress of negative psychotic-like experiences.

Modulation of brain network parameters associated with subclinical psychotic symptoms

OBJECTIVE

Static deficits in small-world properties of brain networks have been described in clinical psychosis, but task-related modulation of network properties has been scarcely studied. Our aim was to assess the modulation of those properties and its association with subclinical psychosis and cognition in the general population.

METHOD

Closeness centrality and small-worldness were compared between pre-stimulus baseline and response windows of an odd-ball task in 200 healthy individuals. The correlation between modulation of network parameters and clinical (scores in the Community Assessment of Psychological Experiences) and cognitive measures (performance in the dimensions included in the Brief Assessment of Cognition in Schizophrenia battery) was analyzed, as well as between these measures and the corresponding network parameters during baseline and response windows during task performance.

RESULTS

In the theta band, closeness centrality decreased and small-worldness increased in the response window. Centrality and small-worldness modulation were, respectively, directly and inversely associated with subclinical symptoms.

CONCLUSIONS

A widespread modulation of network properties in theta band was observed, with a transient increase of small-worldness during the response window, compatible with a transiently more integrated cortical activity associated to cognition. This supports the relevance of electroencephalography to study of normal and altered cognition and its substrates. A relative deficit in the ability to reorganize brain networks may contribute to subclinical psychotic symptoms.

Counterfactual Reasoning Deficits in Schizophrenia Patients

Background

Counterfactual thinking is a specific type of conditional reasoning that enables the generation of mental simulations of alternatives to past factual events. Although it has been broadly studied in the general population, research on schizophrenia is still scarce. The aim of the current study was to further examine counterfactual reasoning in this illness.

Methods

Forty schizophrenia patients and 40 controls completed a series of tests that assessed the influence of the “causal order effect” on counterfactual thinking, and the ability to generate counterfactual thoughts and counterfactually derive inferences from a hypothetical situation. Socio-demographic and clinical characteristics, as well as neurocognitive variables, were also examined.

Results

Compared to controls, the schizophrenia patients generated fewer counterfactual thoughts when faced with a simulated scenario. The pattern of response when assessing the causality effect of the order was also different between the groups, with the patients being more frequently unable to attribute any ordering of events than the control subjects. Additionally, the schizophrenia patients showed more difficulties when deriving normative counterfactual inferences from hypothetical social situations. None of the counterfactual reasoning measures was associated to any of the cognitive functions or clinical and socio-demographic variables assessed.

Conclusions

A global impairment in counterfactual thinking characterizes schizophrenia patients. Because of the potential impact of such deficits on psychosocial functioning, targeting counterfactual reasoning for improvement might be considered in future treatment approaches.

Validation of the Chinese version of Brief Assessment of Cognition in Schizophrenia

OBJECTIVE

A test battery that measures cognitive function impairment in patients with schizophrenia, the Brief Assessment of Cognition in Schizophrenia (BACS), has been translated into various languages and validated. This study aimed to test the reliability and validity of the Chinese version of the BACS in a Chinese-speaking population.

METHODS

All participants in this study (66 patients with schizophrenia [mean age: 41.2 years, 57.6% male] and 66 age- and sex-matched healthy controls) were from Taiwan and assessed using the BACS and the University of California, San Diego (UCSD) Performance-Based Skills Assessment, Brief Version (UPSA-B). Thirty-eight of the 66 patients with schizophrenia received a reassessment using the BACS.

RESULTS

The BACS had good test-retest reliability, and all BACS subtests had statistically insignificant practice effects. Principal components analysis demonstrated that a one-factor solution best fits our dataset (60.9% of the variance). In both patients and controls, the BACS composite scores were positively correlated with all BACS subscales (P<0.001) and UPSA-B scales (P<0.001). Furthermore, all BACS subtests (verbal memory, working memory, motor speed, verbal fluency, attention and processing speed, and executive function) significantly differentiated patients with schizophrenia from healthy controls (P<0.001), and the BACS composite score had the best discriminative validity (P<0.001).

CONCLUSION

The Chinese version of the BACS exhibits satisfactory psychometric properties, including high test-retest reliability, high internal consistency, acceptable concurrent validity, and good discriminant validity. We suggest that the BACS is a reliable and practical tool for assessing cognitive function in patients with schizophrenia.

[Relationship between subclinical psychotic symptoms and cognitive performance in the general population]

INTRODUCTION

Subclinical psychotic symptoms are associated to negative life outcomes in the general population, but their relationship with cognitive performance is still not well understood. Assessing the relationship between performance in cognitive domains and subclinical psychotic symptoms in the general population may also help understand the handicap attributed to clinical psychosis, in which these alterations are present.

METHODS

Subclinical and cognitive assessments were obtained in 203 participants from the general population by means of the Community Assessment of Psychic Experiences, the Brief Assessment of Cognition in Schizophrenia, the Wechsler Adults Intelligence Scale and the Wisconsin Card Sorting Test. The positive and negative subclinical symptoms and their relationship with age and cognition were examined, followed by assessing the influence of subclinical depression scores on the possible relationships between those subclinical psychotic symptoms and cognitive deficits.

RESULTS

Inverse relationships were found between frequency in the Community Assessment of Psychic Experiences positive dimension and motor speed, and frequency and distress in the Community Assessment of Psychic Experiences negative dimension and motor speed. A direct relationship was also found between distress scores of the positive dimension and executive functions. Both positive and negative subclinical symptoms were related to depression scores.

CONCLUSIONS

Psychotic symptoms, similar to those in the clinical population, may be associated with cognitive deficits in the general population.

Validity and reliability of the Brazilian Portuguese version of the BACS (Brief Assessment of Cognition in Schizophrenia)

OBJECTIVE

To assess the validity and reliability of the Brazilian Portuguese version of the Brief Assessment of Cognition in Schizophrenia by examining its temporal stability, internal consistency, and discriminant and convergent validity.

METHODS

The Brief Assessment of Cognition in Schizophrenia was administered to 116 stable patients with schizophrenia and 58 matched control subjects. To assess concurrent validity, a subset of patients underwent a traditional neuropsychological assessment.

RESULTS

The patients with schizophrenia performed significantly worse than the controls (p<0.001) on all subtests of the Brief Assessment of Cognition in Schizophrenia and on the total score, which attests to the discriminant validity of the test. The global score of the Brief Assessment of Cognition in Schizophrenia was significantly correlated with all of the subtests and with the global score for the standard battery. The Brief Assessment of Cognition in Schizophrenia also had good test-retest reliability (rho>0.8). The internal consistency of the Brief Assessment of Cognition in Schizophrenia was high (Cronbach's α  ϝ 0.874).

CONCLUSION

The Brazilian Portuguese version of the Brief Assessment of Cognition in Schizophrenia exhibits good reliability and discriminant and concurrent validity and is a promising tool for easily assessing cognitive impairment in schizophrenia and for comparing the performance of Brazilian patients with that of patients from other countries.

Evaluation of cognitive function in bipolar disorder using the Brief Assessment of Cognition in Affective Disorders (BAC-A)

BACKGROUND

Although cognitive impairment is a core feature of bipolar disorder (BD) there is no instrument of choice for the assessment of bipolar patients. The aim of this study is to assess cognitive performance using the Brief Assessment of Cognition in Affective Disorders (BAC-A), a comprehensive test battery developed specifically for BD, and determine its suitability to estimate global functioning.

METHODS

The BAC-A was administered to 93 BD patients (M ± S.E: 35.18 ± 1.39 years) and 56 healthy controls (HC - M ± S.E: 36.17 ± 1.91 years). The scores of the BAC-A were combined in eight summary scores: visuomotor, immediate affective and non-affective memory, verbal fluency, delayed affective and non-affective memory, inhibition, and problem solving. Post hoc analyses were performed on subtests of the summary scores found to be significantly different between BD patients and HC. Correlational analyses explored the association between the Global Assessment of Functioning (GAF) score and cognitive functioning.

RESULTS

Compared to HC, BD patients showed a significant impairment in short-term non-affective memory and verbal fluency. Poorer performance in verbal memory and verbal fluency summary scores correlated positively with reduced GAF.

CONCLUSIONS

Our results are consistent with previous reports of verbal memory and verbal fluency impairment in BD. The deficits in short-term memory and semantic fluency may indicate inefficient learning strategies and/or difficulties in retrieving information. The BAC-A could be used to estimate global functioning in BD patients.

Gamma power and cognition in patients with schizophrenia and their first-degree relatives

BACKGROUND

Gamma oscillations are essential for functional neural assembly formation underlying higher cerebral functions. Previous studies concerning gamma band power in schizophrenia have yielded diverse results.

METHODS

In this study, we assessed gamma band power in minimally treated patients with schizophrenia, their first-degree relatives and healthy controls during an oddball paradigm performance, as well as the relation between gamma power and cognitive performance.

RESULTS

We found a higher gamma power in the patient group than in the healthy controls at the P3, P4, Fz, Pz and T5 sites. Compared with their relatives, gamma power in the patients was only marginally higher over P3 and P4. We found a nearly significant inverse association between gamma power at F4 and Tower of London performance in the patients, as well as a significant inverse association between gamma power at T5 and verbal memory and working memory scores in the relatives.

CONCLUSION

These results support higher total gamma power in association with schizophrenia and its inverse association with cognitive performance in patients and their first-degree relatives.

A comparative study of event-related coupling patterns during an auditory oddball task in schizophrenia

OBJECTIVE

The aim of this research is to explore the coupling patterns of brain dynamics during an auditory oddball task in schizophrenia (SCH).

APPROACH

Event-related electroencephalographic (ERP) activity was recorded from 20 SCH patients and 20 healthy controls. The coupling changes between auditory response and pre-stimulus baseline were calculated in conventional EEG frequency bands (theta, alpha, beta-1, beta-2 and gamma), using three coupling measures: coherence, phase-locking value and Euclidean distance.

MAIN RESULTS

Our results showed a statistically significant increase from baseline to response in theta coupling and a statistically significant decrease in beta-2 coupling in controls. No statistically significant changes were observed in SCH patients.

SIGNIFICANCE

Our findings support the aberrant salience hypothesis, since SCH patients failed to change their coupling dynamics between stimulus response and baseline when performing an auditory cognitive task. This result may reflect an impaired communication among neural areas, which may be related to abnormal cognitive functions.

Decreased spectral entropy modulation in patients with schizophrenia during a P300 task

Spectral entropy (SE), also known as Shannon entropy, is a useful parameter for quantifying the global regularity of the electroencephalographic (EEG) signal. Hence, it is of interest in the assessment of the electrophysiological correlates of cognitive processing in schizophrenia. However, to date, SE has been barely used in studies comparing resting EEG recordings between patients and controls. In this work, we compared SE between resting baseline [-250 0] ms and active task [150 550] ms windows of a P300 task in 31 patients with schizophrenia and 38 controls. Moreover, we also calculated the median frequency (MF) and relative power in each frequency band for these windows to assess the correlates of the possible SE differences. Controls showed a significant (p < 0.0029) SE decrease (i.e., meaning higher signal regularity) from baseline to the active task window at parietal and central electrode sites. This SE decrease from baseline to active conditions was significantly lower in patients. In controls, this SE decrease was accompanied by a statistically significant decrease in MF (i.e., a significant slowing of the EEG activity), not observed in patients. In this latter group, the difference in SE between resting baseline and active task windows was inversely correlated to positive and total symptoms scores, as measured with the positive and negative symptoms scale. Our data support the relevance of SE in the study of cerebral processing in schizophrenia.

Structural correlates of cognitive deficit and elevated gamma noise power in schizophrenia

AIMS

The aim of this study was to assess the relation between cognition, gray matter (GM) volumes and gamma noise power (amount of background oscillatory activity in the gamma band) in schizophrenia.

METHODS

We explored the relation between cognitive performance and regional GM volumes using voxel-based morphometry (VBM), in order to discover if the association between gamma noise power (an electroencephalography measurement of background activity in the gamma band) and cognition is observed through structural deficits related to the disease. Noise power, magnetic resonance imaging and cognitive assessments were obtained in 17 drug-free paranoid patients with schizophrenia and 13 healthy controls.

RESULTS

In comparison with controls, patients showed GM deficits at posterior cingulate (bilateral),left inferior parietal (supramarginal gyrus) and left inferior dorsolateral prefrontal regions. Patients exhibited a direct association between performance in working memory and right temporal (superior and inferior gyri) GM densities. They also displayed a negative association between right anterior cerebellum volume and gamma noise power at the frontal midline (Fz) site.

CONCLUSION

A structural deficit in the cerebellum may be involved in gamma activity disorganization in schizophrenia. Temporal structural deficits may relate to cognitive dysfunction in this illness.

Validation of the Persian version of the brief assessment of cognition in schizophrenia in patients with schizophrenia and healthy controls

AIMS

The Brief Assessment of Cognition in Schizophrenia (BACS) is designed for assessment of cognitive function in patients with schizophrenia. Versions of the BACS in English and other languages have been shown to be as sensitive to cognitive dysfunction as a standard test battery, with the advantage of brief administration and scoring time. The present study aimed to test the concurrent validity of the Persian version of the BACS (Persian-BACS).

METHODS

A group of 50 patients with schizophrenia-spectrum disorders and a group of 50 healthy controls received the Persian-BACS in a first session, and in a second session a standard neurocognitive battery.

RESULTS

Cronbach's alpha for the Persian-BACS was 0.74. All the Persian-BACS subscales were significantly correlated with the corresponding standard neurocognitive subscales and the Pearson correlation of the composite scores from the two instruments was 0.71. Moreover, a one-factor solution was found that accounted for 67.9% of the variance. Finally, the Persian-BACS demonstrated high ability to discriminate patients with schizophrenia from healthy controls.

CONCLUSION

Good psychometric properties of the Persian-BACS suggest that it is a useful tool for assessing cognition in schizophrenic patients with Persian as their primary language.

Frontal gamma noise power and cognitive domains in schizophrenia

The cognitive deficit profile is different among individuals with schizophrenia. We quantified the amount of electroencephalographic activity unlocked to stimuli onset (noise power) over frontal regions regarding deficit in cognitive domains. Forty-six patients with schizophrenia and 27 healthy controls underwent clinical, cognitive and electrophysiological assessments. Noise power studies may be considered complementary but not equivalent to induced power studies. We compared gamma and theta noise power magnitude during a P300 paradigm between subsets of patients divided according to cognitive deficit in key domains and controls. Patients displayed higher gamma noise power activity at Fz site and significantly lower performance in all cognitive domains when compared to controls. The subset of patients with cognitive deficit for working memory and problem solving/executive functions domains displayed significantly higher frontal-lateral noise power values in comparison to the subset of patients without cognitive deficit and controls. Patients with significant cognitive deficits in domains with greater frontal contribution are also characterized by an abnormally higher gamma band noise power over the frontal region. Our data may endorse various biological subsets within schizophrenia, characterized by the presence or absence of a significant cognitive deficit in frontal domains.

Cognitive outcome and gamma noise power unrelated to neuregulin 1 and 3 variation in schizophrenia

BACKGROUND

Neuregulins are a family of signalling proteins that orchestrate a broad range of cellular responses. Four genes encoding Neuregulins 1-4 have been identified so far in vertebrates. Among them, Neuregulin 1 and Neuregulin 3 have been reported to contribute to an increased risk for developing schizophrenia. We hypothesized that three specific variants of these genes (rs6994992 and rs3924999 for Neuregulin 1 and rs10748842 for Neuregulin 3) that have been related to this illness may modify information processing capacity in the cortex, which would be reflected in electrophysiological parameters (P3b amplitude or gamma noise power) and/or cognitive performance.

METHODS

We obtained DNA from 31 patients with schizophrenia and 23 healthy controls and analyzed NRG1 rs6994992, NRG1 rs3924999 and NRG3 rs10748842 promoter polymorphisms by allelic discrimination with real-time polymerase chain reaction (PCR). We compared cognitive outcome, P300 amplitude parameters and an electroencephalographic measure of noise power in the gamma band between the groups dichotomized according to genotype.

RESULTS

Contrary to our hypothesis, we could not detect any significant influence of variation in Neuregulin 1/Neuregulin 3 polymorphisms on cognitive performance or electrophysiological parameters of patients with schizophrenia.

CONCLUSIONS

Despite our findings, we cannot discard that other genetic variants and, more likely, interactions between those variants and with genetic variation related to different pathways may still influence cerebral processing in schizophrenia.