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.

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.

Relaciones entre síntomas psicóticos subclínicos y rendimiento cognitivo en la población general / Relationship between subclinical psychotic symptoms and cognitive performance in the general population

Introducción. En la población general, los síntomas psicóticos subclínicos se han asociado con mayores dificultades funcionales en la vida real, pero desconocemos si estos síntomas están asociados a un peor rendimiento cognitivo. El estudio de la relación entre las alteraciones cognitivas y estos síntomas puede, además, ayudarnos a comprender mejor las dificultades que presentan los pacientes con psicosis, en los que estas alteraciones cognitivas están presentes. Métodos. Realizamos evaluaciones clínicas y cognitivas en 203 sujetos de la población general mediante los instrumentos Community Assessment of Psychic Experiences, Brief Assessment of Cognition in Schizophrenia, Wechsler Adult Intelligence Scale y Wisconsin Card Sorting Test. Se evaluó la relación de los síntomas psicóticos subclínicos positivos y negativos con la edad y el rendimiento cognitivo. Además, se evaluó la influencia de los síntomas depresivos subclínicos sobre la posible relación entre síntomas positivos y negativos subclínicos y las alteraciones cognitivas. Resultados. Encontramos una relación inversa del rendimiento en la prueba de velocidad motora tanto con la frecuencia de síntomas positivos como con el distrés y la frecuencia de los síntomas negativos. También encontramos una relación directa entre el distrés de los síntomas positivos y el rendimiento en función ejecutiva. La puntuación en síntomas depresivos subclínicos se asoció con ambas escalas subclínicas, positiva y negativa. Conclusiones. Los síntomas psicóticos subclínicos están relacionados con déficits cognitivos en la población general, similares a los observados en poblaciones clínicas (AU)

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 (AU)

[Relationship between subclinical psychotic symptoms and cognitive performance in the general population]. / Relaciones entre síntomas psicóticos subclínicos y rendimiento cognitivo en la población general.

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.

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.