Resting-state functional nuclear magnetic resonance imaging in patients with bipolar disorder: Beyond euthymia.

INTRODUCTION: Functional nuclear magnetic resonance imaging in the resting state (R-fMRI) allows the identification of complete functional connectivity networks and the possible neuronal correlations of psychiatric disorders. The literature on R-fMRI and bipolar disorder (BD) will be reviewed, emphasising the findings in the phases of mania, hypomania and depression. METHODS: It is a narrative review of the literature in which articles were searched in PubMed and Embase, with the key words in English "bipolar disorder" AND "resting state", without limit on the date of publication. RESULTS: The studies of BD patients in the mania and hypomania phases who underwent R-fMRI show concordant results in terms of decreased functional cerebral connectivity between the amygdala and some cortical regions, which indicates that this functional connection would have some implication in the normal affect regulation. Patients in the depressive phase show a decrease in functional brain connectivity, but as there are several anatomical structures involved and neural networks reported in the studies, it is not possible to compare them. CONCLUSIONS: There is a decrease in functional connectivity in patients with BD, but current evidence does not allow establishing specific changes in specific functional brain connectivity networks. However, there are already some findings that show correlation with the patients' symptoms.

Resonancia magnética nuclear funcional en estado de reposo en pacientes con trastorno bipolar: más allá de la eutimia / Resting-state functional nuclear magnetic resonance imaging in patients with bipolar disorder: beyond euthymia

Resumen Introducción: La resonancia magnética funcional en estado de reposo (RMf-ER) permite identificar redes de conectividad funcional completas y los posibles correlatos neuronales de trastornos psiquiátricos. Se revisa la literatura sobre RMf-ER y trastorno bipolar (TB) haciendo énfasis en los hallazgos en las fases de manía, hipomanía y depresión. Métodos: Es una revisión narrativa de la literatura en la que se buscaron artículos en PubMed y EMBASE con las palabras clave en inglés "bipolar disorder" AND "resting state", sin límite en la fecha de publicación. Resultados: Los estudios de pacientes con TB en fases de manía e hipomanía sometidos a RMf-ER muestran resultados concordantes en cuanto a la disminución de la conectividad funcional cerebral entre la amígdala y algunas regiones corticales, lo cual indica que esta conexión funcional tendría alguna implicación en la regulación normal del afecto. Los pacientes en fase depresiva muestran disminución en la conectividad funcional cerebral, pero como son varias las estructuras anatómicas implicadas y las redes neuronales reportadas en los estudios, no es posible compararlos. Conclusiones: Hay disminución en la conectividad funcional en los pacientes con TB, pero la evidencia actual no permite establecer cambios específicos en redes de conectividad funcional cerebral puntuales. Sin embargo, ya hay algunos hallazgos que muestran correlación con la clínica de los pacientes.

ABSTRACT Introduction: imaging in the resting state (R-fMRI) Functional nuclear magnetic allows the identification of complete functional connectivity networks and the possible resonance neuronal correlations of psychiatric disorders. The literature on R-fMRI and bipolar disorder (BD) will be reviewed, emphasising the findings in the phases of mania, hypomania and depression. Methods: It is a narrative review of the literature in which articles were searched in PubMed and Embase, with the key words in English "bipolar disorder" AND "resting state", without limit on the date of publication. Results: The studies of BD patients in the mania and hypomania phases who underwent R-fMRI show concordant results in terms of decreased functional cerebral connectivity between the amygdala and some cortical regions, which indicates that this functional connection would have some implication in the normal affect regulation. Patients in the depressive phase show a decrease in functional brain connectivity, but as there are seve-ral anatomical structures involved and neural networks reported in the studies, it is not possible to compare them. Conclusions: There is a decrease in functional connectivity in patients with BD, but current evidence does not allow establishing specific changes in specific functional brain connectivity networks. However, there are already some findings that show correlation with the patients' symptoms.

Estabilidad de la actividad eléctrica no lineal durante condiciones basales con los ojos cerrados / Nonlinear electrical activity stability in basal, eyes closed conditions

Introducción: El electroencefalograma permite registrar la actividad eléctrica cerebral en estado de reposo y durante la ejecución de tareas cognitivas. Objetivo: Evaluar si la actividad cerebral, analizada como dinámica no lineal, se mantiene estable durante diferentes ventanas temporales en una condición basal con ojos cerrados. Métodos: Se realizaron registros con electroencefalograma durante dos minutos a 14 estudiantes universitarios varones. Posteriormente, se compararon las medias de índices de Hurst (H) en ventanas temporales de 60, 30 y 10 segundos. Resultados: Las medias de los índices H son estables a través de diferentes ventanas temporales en las regiones prefrontales, temporales y occipitales. Conclusiones: Los registros de electroencefalograma en condiciones basales con los ojos cerrados son válidos para comparar protocolos experimentales de resolución de problemas cognitivos utilizando el exponente de Hurst en los sujetos de la muestra y en otros con características similares(AU)

Introduction: Electroencephalography makes it possible to record brain electrical activity at rest and during the performance of cognitive tasks. Objective: Determine whether brain activity analyzed as nonlinear dynamics remains stable during various time windows in basal, eyes closed conditions. Methods: Electroencephalographic records of 14 male university students were taken during two minutes. Hurst's index means (H) were then compared in time windows of 60, 30 and 10 seconds. Results: H index means are stable throughout the various time windows in the prefrontal, temporal and occipital regions. Conclusions: Electroencephalographic records in basal, eyes closed conditions are valid to compare experimental protocols for cognitive problem solving using the Hurst exponent in subjects from the sample as well as others of similar characteristics(AU)

Resting-state functional nuclear magnetic resonance imaging in patients with bipolar disorder: beyond euthymia. / Resonancia magnética nuclear funcional en estado de reposo en pacientes con trastorno bipolar: más allá de la eutimia.

INTRODUCTION: Functional nuclear magnetic resonance imaging in the resting state (R-fMRI) allows the identification of complete functional connectivity networks and the possible neuronal correlations of psychiatric disorders. The literature on R-fMRI and bipolar disorder (BD) will be reviewed, emphasising the findings in the phases of mania, hypomania and depression. METHODS: It is a narrative review of the literature in which articles were searched in PubMed and Embase, with the key words in English "bipolar disorder" AND "resting state", without limit on the date of publication. RESULTS: The studies of BD patients in the mania and hypomania phases who underwent R-fMRI show concordant results in terms of decreased functional cerebral connectivity between the amygdala and some cortical regions, which indicates that this functional connection would have some implication in the normal affect regulation. Patients in the depressive phase show a decrease in functional brain connectivity, but as there are several anatomical structures involved and neural networks reported in the studies, it is not possible to compare them. CONCLUSIONS: There is a decrease in functional connectivity in patients with BD, but current evidence does not allow establishing specific changes in specific functional brain connectivity networks. However, there are already some findings that show correlation with the patients' symptoms.

Redes en estado de reposo: revisión y aplicaciones de un concepto en evolución / Resting state networks: review and applications of an evolving concept / Redes em estado de repouso: revisão e aplicações de um conceito em evolução

El concepto de redes en estado de reposo se refiere a fluctuaciones coherentes de la actividad cerebral, presentes en forma de redes que aparecen cuando los sujetos no están ocupados en alguna actividad o proceso cognitivo superior. Estas redes han sido identificadas en estudios de resonancia magnética funcional y reflejan un alto nivel de conectividad del cerebro humano. El concepto ha crecido en notoriedad hasta tal punto que ahora es casi rutina entre los grupos que usan resonancia magnética en sus investigaciones. Se ha estudiado la actividad de las redes en estado de reposo en el envejecimiento, el deterioro cognitivo leve y diversas enfermedades neurológicas y psiquiátricas. Además, se ha demostrado su existencia en otros primates y en ratas. En esta revisión se presenta una visión general del concepto, así como de las herramientas para la adquisición y el análisis. Igualmente se discuten algunas investigaciones relevantes sobre el tema y su impacto en diversas entidades clínicas.

The concept of resting state networks refers to coherent fluctuations of brain activity, which appear when the subjects are not engaged in any task or superior cognitive process. Such networks have been identified in functional magnetic resonance studies and reflect a high connectivity level of the human brain. The concept has gained notoriety and has become routine among groups using functional magnetic resonance in their studies. The activity of the resting state networks has been studied in ageing, mild cognitive impairment and several neurological and psychiatric diseases. Additionally, its existence has been proved in non-human primates and rats. A general overview of the concept is presented here, as well as the acquisition and analysis tools. Moreover, some relevant evidence on this subject matter as well as its impact on several clinical entities are discussed.

O conceito de redes em estado de repouso se refere a flutuações coerentes da atividade cerebral, presentes em forma de redes que aparecem quando os sujeitos não estão ocupados em alguma atividade ou processo cognitivo superior. Estas redes têm sido identificadas em estudos de ressonância magnética funcional e refletem um alto nível de conectividade do cérebro humano. O conceito tem crescido em notoriedade até tal ponto que agora é quase rotina entre os grupos que usam ressonância magnética em suas investigações. A atividade das redes em estado de repouso tem sido estudada em envelhecimento, deterioro cognitivo leve e diversas doenças neurológicas e psiquiátricas. Adicionalmente se há demostrado sua existência em outros primatas e em ratos. Nesta revisão se oferece uma visão geral do conceito, assim como das ferramentas para a aquisição e a análise. Igualmente se discutem algumas investigações relevantes sobre o assunto e seu impacto em diversas entidades clínicas.

Activación cerebral en estado de reposo en Default Mode Network de pacientes eutímicos con trastorno bipolar tipo I / Brain activitivation of euthymic patients with Type I bipolar disorder in resting state Default Mode Network

Introducción: Aún existen dudas sobre la conectividad cerebral en el trastorno bipolar tipo I (TBI) y son necesarios estudios con resonancia magnética funcional en estado de reposo (RMf-ER) durante la eutimia para identificar alteraciones funcionales del trastorno. Objetivo: Evaluar con RMf-ER la diferencias de activación cerebral entre los pacientes eutí-micos con TBI y los sujetos de control y explorar el efecto del litio en esta activación. Métodos: Estudio transversal de 21 pacientes eutímicos con TBI y 12 controles, usando RMf-ER y un análisis de componentes independientes. En el grupo con TBI, también se realizó una comparación entre 10 pacientes con TBI en monoterapia con litio y 11 sin medicación. Resultados: Se encontró mayor activación en el hipocampo derecho (p = 0,049) y el cíngulo posterior (p = 0,040) en la Default Mode Network (DMN) del grupo TBI frente a los controles. No hubo diferencias estadísticamente significativas entre el grupo de TBI con litio y los pacientes con TBI sin medicación. Conclusiones: Los resultados indican alteraciones en la activación y la conectividad cerebral en el TBI durante la eutimia y principalmente en el cíngulo posteriory el hipocampo dentro de la DMN, la cual podría tener relevancia en la regulación afectiva.

Introduction: As there are still doubts about brain connectivity in type I bipolar disorder (BID), resting-state functional magnetic resonance imaging (RS-fMRI) studies are necessary during euthymia for a better control of confounding factors. Objective: To evaluate the differences in brain activation between euthymic BID patients and control subjects using resting state- functional-magnetic resonance imaging (RS-fMRI), and to identify the lithium effect in these activations. Methods: A cross-sectional study was conducted on 21 BID patients (10 receiving lithium only, and 11 non-medicated) and 12 healthy control subjects, using RS fMRI and independent component analysis (ICA). Results: Increased activation was found in the right hippocampus (P = .049) and posterior cingulate (P = .040) within the Default Mode Network (DMN) when BID and control group were compared. No statistically significant differences were identified between BID on lithium only therapy and non-medicated BID patients. Conclusions: The results suggest that there are changes in brain activation and connectivity in BID even during euthymic phase and mainly within the DMN network, which could be relevant in affect regulation.

[Brain activitivation of euthymic patients with Type I bipolar disorder in resting state Default Mode Network]. / Activación cerebral en estado de reposo en Default Mode Network de pacientes eutímicos con trastorno bipolar tipo I.

INTRODUCTION: As there are still doubts about brain connectivity in type I bipolar disorder (BID), resting-state functional magnetic resonance imaging (RS-fMRI) studies are necessary during euthymia for a better control of confounding factors. OBJECTIVE: To evaluate the differences in brain activation between euthymic BID patients and control subjects using resting state- functional-magnetic resonance imaging (RS-fMRI), and to identify the lithium effect in these activations. METHODS: A cross-sectional study was conducted on 21 BID patients (10 receiving lithium only, and 11 non-medicated) and 12 healthy control subjects, using RS fMRI and independent component analysis (ICA). RESULTS: Increased activation was found in the right hippocampus (P=.049) and posterior cingulate (P=.040) within the Default Mode Network (DMN) when BID and control group were compared. No statistically significant differences were identified between BID on lithium only therapy and non-medicated BID patients. CONCLUSIONS: The results suggest that there are changes in brain activation and connectivity in BID even during euthymic phase and mainly within the DMN network, which could be relevant in affect regulation.