What do brain network interactions tell about cognitive processes? How to seek causality?

Optimal adjustment of brain networks allows the biased processing of information in response to the demand of environments and is therefore prerequisite for adaptive behaviour. It is widely shown that a biased state of networks is associated with a particular cognitive process. However, those associations were identified by backward categorization of trials and cannot provide a causal association with cognitive processes. This problem still remains a big obstacle to advance the state of our field in particular human cognitive neuroscience. In my talk, I will present two approaches to address the causal relationships between brain network interactions and behaviour. Firstly, we combined connectivity analysis of fMRI data and a machine leaning method to predict inter-individual differences of behaviour and responsiveness to environmental demands. The connectivity-based classification approach outperforms local activation-based classification analysis, suggesting that interactions in brain networks carry information of instantaneous cognitive processes. Secondly, we have recently established a brand new method combining transcranial alternating current stimulation (tACS), transcranial magnetic stimulation (TMS), and EEG. We use the method to measure signal transmission between brain areas while introducing extrinsic oscillatory brain activity and to study causal association between oscillatory activity and behaviour. We show that phase-matched oscillatory activity creates the phase-dependent modulation of signal transmission between brain areas, while phase-shifted oscillatory activity blunts the phase-dependent modulation. The results suggest that phase coherence between brain areas plays a cardinal role in signal transmission in the brain networks. In sum, I argue that causal approaches will provide more concreate backbones to cognitive neuroscience.

Minimized Extracorporeal Circulation does not impair cognitive brain function after coronary artery bypass grafting

Gebiet: Chirurgie Abstract: Minimized Extracorporeal Circulation does not impair cognitive brain function after coronary artery bypass grafting – – Objectives – Objective evaluation of the impact of minimized extracorporeal circulation (MECC) on perioperative cognitive brain function in coronary bypass grafting (CABG) by Electroencephalogram (EEG) P 300 wave event related potentials (ERP) and number connection test ( NCT) as metrics of cognitive function. – – Methods – Cognitive brain function was assessed in 31 patients with a mean age of 65y (Standard Deviation/SD 10) undergoing coronary artery bypass grafting (CABG) by the use of MECC with P300 auditory evoked potentials (peak latencies in milliseconds [ms]) directly prior to intervention, 7 days after and 3 month later. Number connection test (NCT), serving as method of control, was performed simultaneously in all patients. – – Results – Seven days following CABG, cognitive P300 evoked potentials were comparable to preoperative baseline values (vertex [Cz] 376 (SD 11) ms vs. 378 (18) ms, p=0.39, frontal [Fz] 377 (11) vs. 379 (21) ms, p=0.53). Cognitive brain function showed at 3 months compared to baseline values ([Cz] 376 (11) ms vs. 371 (14 ms) p=0.09, [Fz] 377 (11) ms vs. 371 (15) ms, p=0.04. Between the first postoperative measurement and 3 months later, significant improvement was observed ([Cz] 378 (18) ms vs. 371 (14) ms, p=0.03, [Fz] 379 (21) vs. 371 (15) ms, p=0.02). Similar clearly corresponding patterns could be obtained via number connection test. Results could be confirmed in repeated measures analysis of variance for Cz (p = 0.05) and (Fz) results (p = 0.04). – – Conclusions

The spectrum of the non-rapid eye movement sleep electroencephalogram following total sleep deprivation is trait-like

The sleep electroencephalogram (EEG) spectrum is unique to an individual and stable across multiple baseline recordings. The aim of this study was to examine whether the sleep EEG spectrum exhibits the same stable characteristics after acute total sleep deprivation. Polysomnography (PSG) was recorded in 20 healthy adults across consecutive sleep periods. Three nights of baseline sleep [12 h time in bed (TIB)] following 12 h of wakefulness were interleaved with three nights of recovery sleep (12 h TIB) following 36 h of sustained wakefulness. Spectral analysis of the non-rapid eye movement (NREM) sleep EEG (C3LM derivation) was used to calculate power in 0.25 Hz frequency bins between 0.75 and 16.0 Hz. Intraclass correlation coefficients (ICCs) were calculated to assess stable individual differences for baseline and recovery night spectra separately and combined. ICCs were high across all frequencies for baseline and recovery and for baseline and recovery combined. These results show that the spectrum of the NREM sleep EEG is substantially different among individuals, highly stable within individuals and robust to an experimental challenge (i.e. sleep deprivation) known to have considerable impact on the NREM sleep EEG. These findings indicate that the NREM sleep EEG represents a trait.

15 Years of Microstate Research in Schizophrenia - Where Are We? A Meta-Analysis

Schizophrenia patients show abnormalities in a broad range of task demands. Therefore, an explanation common to all these abnormalities has to be sought independently of any particular task, ideally in the brain dynamics before a task takes place or during resting state. For the neurobiological investigation of such baseline states, EEG microstate analysis is particularly well suited, because it identifies subsecond global states of stable connectivity patterns directly related to the recruitment of different types of information processing modes (e.g., integration of top-down and bottom-up information). Meanwhile, there is an accumulation of evidence that particular microstate networks are selectively affected in schizophrenia. To obtain an overall estimate of the effect size of these microstate abnormalities, we present a systematic meta-analysis over all studies available to date relating EEG microstates to schizophrenia. Results showed medium size effects for two classes of microstates, namely, a class labeled C that was found to be more frequent in schizophrenia and a class labeled D that was found to be shortened. These abnormalities may correspond to core symptoms of schizophrenia, e.g., insufficient reality testing and self-monitoring as during auditory verbal hallucinations. As interventional studies have shown that these microstate features may be systematically affected using antipsychotic drugs or neurofeedback interventions, these findings may help introducing novel diagnostic and treatment options.

Inefficient Preparatory fMRI-BOLD Network Activations Predict Working Memory Dysfunctions in Patients with Schizophrenia

Patients with schizophrenia show abnormal dynamics and structure of temporally ­coherent networks (TCNs) assessed using fMRI, which undergo adaptive shifts in preparation for a cognitively demanding task. During working memory (WM) tasks, patients with schizophrenia show persistent deficits in TCNs as well as EEG indices of WM. Studying their temporal relationship during WM tasks might provide novel insights into WM performance deficits seen in schizophrenia. Simultaneous EEG-fMRI data were acquired during the performance of a verbal Sternberg WM task with two load levels (load 2 and load 5) in 17 patients with schizophrenia and 17 matched healthy controls. Using covariance mapping, we investigated the relationship of the activity in the TCNs before the memoranda were encoded and EEG spectral power during the retention interval. We assessed four TCNs – default mode network (DMN), dorsal attention network (dAN), left and right working memory networks (WMNs) – and three EEG bands – theta, alpha, and beta. In healthy controls, there was a load-dependent inverse relation between DMN and frontal midline theta power and an anti-correlation between DMN and dAN. Both effects were not significantly detectable in patients. In addition, healthy controls showed a left-lateralized load-dependent recruitment of the WMNs. Activation of the WMNs was bilateral in patients, suggesting more resources were recruited for successful performance on the WM task. Our findings support the notion of schizophrenia patients showing deviations in their neurophysiological responses before the retention of relevant information in a verbal WM task. Thus, treatment strategies as neurofeedback ­targeting prestates could be beneficial as task performance relies on the preparatory state of the brain.

Implicit memory for the content but not the speaker of sleep-played messages

We presented 28 sentences uttered by 28 unfamiliar speakers to sleeping participants to investigate whether humans can encode new verbal messages, learn voices of unfamiliar speakers, and form associations between speakers and messages during EEG-defined deep sleep. After waking, participants performed three tests which assessed the unconscious recognition of sleep-played speakers, messages, and speaker-message associations. Recognition performance in all tests was at chance level. However, response latencies revealed implicit memory for sleep-played messages but neither for speakers nor for speaker-message combinations. Only participants with excellent implicit memory for sleep-played messages also displayed implicit memory for speakers but not speaker-message associations. Hence, deep sleep allows for the semantic encoding of novel verbal messages.

An exploratory analysis of variance and volatility in epileptic electroencephalograms

The electroencephalogram (EEG) is a physiological time series that measures electrical activity at different locations in the brain, and plays an important role in epilepsy research. Exploring the variance and/or volatility may yield insights for seizure prediction, seizure detection and seizure propagation/dynamics.^ Maximal Overlap Discrete Wavelet Transforms (MODWTs) and ARMA-GARCH models were used to determine variance and volatility characteristics of 66 channels for different states of an epileptic EEG – sleep, awake, sleep-to-awake and seizure. The wavelet variances, changes in wavelet variances and volatility half-lives for the four states were compared for possible differences between seizure and non-seizure channels.^ The half-lives of two of the three seizure channels were found to be shorter than all of the non-seizure channels, based on 95% CIs for the pre-seizure and awake signals. No discernible patterns were found the wavelet variances of the change points for the different signals. ^

Biomedical informatics applications for epilepsy management: A systematic review

Epilepsy is a very complex disease which can have a variety of etiologies, co-morbidities, and a long list of psychosocial factors4. Clinical management of epilepsy patients typically includes serological tests, EEG's, and imaging studies to determine the single best antiepileptic drug (AED). Self-management is a vital component of achieving optimal health when living with a chronic disease. For patients with epilepsy self-management includes any necessary actions to control seizures and cope with any subsequent effects of the condition9; including aspects of treatment, seizure, and lifestyle. The use of computer-based applications can allow for more effective use of clinic visits and ultimately enhance the patient-provider relationship through focused discussion of determinants affecting self-management. ^ The purpose of this study is to conduct a systematic literature review on informatics application in epilepsy self-management in an effort to describe current evidence for informatics applications and decision support as an adjunct to successful clinical management of epilepsy. Each publication was analyzed for the type of study design utilized. ^ A total of 68 publications were included and categorized by the study design used, development stage, and clinical domain. Descriptive study designs comprised of three-fourths of the publications and indicate an underwhelming use of prospective studies. The vast majority of prospective studies also focused on clinician use to increase knowledge in treating patients with epilepsy. ^ Due to the chronic nature of epilepsy and the difficulty that both clinicians and patients can experience in managing epilepsy, more prospective studies are needed to evaluate applications that can effectively increase management activities. Within the last two decades of epilepsy research, management studies have employed the use of biomedical informatics applications. While the use of computer applications to manage epilepsy has increased, more progress is needed.^

Enfermedad de Creutzfeld Jakob, desafío diagnóstico : reporte de dos casos en la ciudad de Mendoza

La enfermedad de Creutzfeldt-Jakob (ECJ) es una afección neurodege-nerativa rápidamente progresiva y mortal producida por priones. Es la más común de las encefalopatías espongiformes. La hipótesis prevalente sugiere que se inicia y propaga por conversión de una proteína priónica normal (PrP) en una isoforma conformacional anormal (PrPreS), que se acumula en el cerebro causando destrucción neuronal. Se reporta el caso de dos pacientes asistido en el Servicio de Neurología del Hospital Lagomaggiore de la ciudad de Mendoza en el período de 2 años: mujer de 49 años con cuadro de deterioro cognitivo rápidamente progresivo asociado a trastorno de la marcha y ataxia de 2 meses de evolución; y varón de 54 años con conductas inapropiadas y desorientación temporo-espacial de 20 días de evolución. Ambos con EEG compatible y proteína 14.3.3 positiva, falleciendo semanas después del diagnóstico. Se discute ambos casos, los cuales representaron un desafío diagnóstico dada la baja frecuencia y escaso reconocimiento de esta entidad en nuestro medio, debiendo debe ser considerado en pacientes que evolucionan a una demencia rápidamente progresiva.

Gobernar la complejidad urbana desde la sostenibilidad. Evaluación del gobierno de la gestión visible utilizando indicadores de gobernanza (Venezuela)

Se evalúa con indicadores de gobernanza urbana la sostenibilidad de las formas de hacer ciudad hibrida compleja del gobierno de la gestión visible (GGV). Argumenta que el GGV hace ciudad para legitimarse por desempeño y fortalecer la gobernanza local, en un contexto de mutaciones múltiples y radicales que tienden a diluir y centralizar el poder local y fractalizar la ciudad, profundizando la segregación sociopolítica-territorial y la ingobernabilidad genética de la ciudad hibrida, poniendo en riesgo el Estado federal descentralizado, el derecho a la ciudad, al gobierno local y la gobernanza urbana y multinivel (hipótesis). La estrategia de evaluación de gobernanza innovadora (EEG+i) diseñada para evaluar la relación entre las formas de hacer ciudad hibrida (variables espaciales) y gobernanza (variable a-espacial) es transversal, multidimensional y se construye desde la complejidad, el análisis de escenarios, formulación de constructos, modelos e indicadores de gobernanza, entretejiendo tres campos de conocimiento, gobierno, ciudad y sostenibilidad, en cuatro fases. La Fase 1, contextualiza la gobernanza en la dramática del siglo XXI. La Fase 2, desarrolla la fundamentación teórico-práctica, nuevos conceptos y un abordaje analítico propio ‘genética territorial’, para analizar y comprehender la complejidad de la ciudad hibrida de países en desarrollo, tejiendo ontogenética territorial y el carácter autopoiético del gen informal. En la Fase 3, se caracterizan las formas de hacer ciudad desde la genética del territorio, se formulan modelos e indicadores de gobernanza con los que se evalúan, aplicando un delphi y cuestionarios, los genes tipológicos-formas de hacer ciudad y validan las conclusiones. En la Fase 4, se correlacionan los resultados de los instrumentos aplicados con la praxis urbana del GGV, durante cuatro periodos de gobierno (1996-2010). Concluyendo que, la estrategia de evaluación comprobó las hipótesis y demostró la correlación transversal y multinivel existente entre, las mutaciones en curso que contradicen el modelo de gobernanza constitucional, el paisaje de gobernanza latinoamericano y venezolano, la praxis de los regímenes híbridos ricos en recursos naturales, las perspectivas de desarrollo globales y se expresa sociopolíticamente en déficit de gobernanza, Estado de derecho y cohesión-capital social y, espaciolocalmente, en la ciudad hibrida dispersa y diluida (compleja) y en el gobierno del poder diluido centralizado. La confrontación de flujos de poder centrípetos y centrífugos en la ciudad profundiza la fragmentación socioespacial y política y el deterioro de la calidad de vida, incrementando las protestas ciudadanas e ingobernabilidad que obstaculiza la superación de la pobreza y gobernanza urbana y multinivel. La evaluación de la praxis urbana del GGV evidenció que la correlación entre gobernanza, la producción de genes formales y la ciudad por iniciativa privada tiende a ser positiva y entre gobernanza, genes y producción de ciudad informal negativa, por el carácter autopoiético-autogobernable del gen informal y de los nuevos gobiernos sublocales que dificulta gobernar en gobernanza. La praxis del GGV es contraria al modelo de gobernanza formulado y la disolución centralizada del gobierno local y de la ciudad hibrida-dispersa es socio-espacial y políticamente insostenible. Se proponen estrategias y tácticas de gobernanza multinivel para recuperar la cohesión social y de planificación de la gestión innovadora (EG [PG] +i) para orquestar, desde el Consejo Local de Gobernanza (CLG) y con la participación de los espacios y gobiernos sublocales, un proyecto de ciudad compartido y sostenible. ABSTRACT The sustainability of the forms of making the hybrid-complex city by the visible management government (VMG) is evaluated using urban governance indicators. Argues that the VMG builds city to legitimate itself by performance and to strengthen local governance in a context of multiple and radical mutations that tend to dilute and centralize local power and fractalize the city, deepening the socio-spatial and political segregation, the genetic ingovernability of the hybrid city and placing the decentralized federal State, the right to city, local government and urban governance at risk (hypothesis). The innovative governance evaluation strategy (GES+i) designed to assess the relationship between the forms of making the hybrid city (spatial variables) and governance (a-spatial variable) is transversal, multidimensional; is constructed from complexity, scenario analysis, the formulation of concepts, models and governance indicators, weaving three fields of knowledge, government, city and sustainability in four phases. Phase 1, contextualizes governance in the dramatic of the twenty-first century. Phase 2, develops the theoretical and practical foundations, new concepts and a proper analytical approach to comprehend the complexity of the hybrid city from developing countries, weaving territorial ontogenetic with the autopiethic character of the informal city gen. In Phase 3, the ways of making city are characterized from the genetics of territory; governance indicators and models are formulated to evaluate, using delphi and questionnaires, the ways of making city and validate the conclusions. In Phase 4, the results of the instruments applied are correlated with the urban praxis of the VMG during the four periods of government analyzed (1996-2010). Concluding that, the evaluation strategy proved the hypothesis and showed the transversal and multilevel correlation between, mutations that contradict the constitutional governance model, the governance landscape of Latinamerica and the country, the praxis of the hybrid regimes rich in natural resources, the perspectives of the glocal economy and expresses socio-politically the governance and rule of law and social capital-cohesion deficit and spatial-temporarily the hybrid disperse and diluted city (complex) and the diluted-centralized local government. The confrontation of flows of power centripetal and centrifugal in the city deepens the socio-spatial and political fragmentation and deterioration of the quality of life, increasing citizens' protests and ingovernability which hinders poverty eradication and, multilevel and urban governance. The evaluation of the VMG urban praxis showed the correlation between governance, the production of formal genes and city by private initiative tended to be positive and, between informal genes-city production and governance negative, due to its autopiethic-self governable character that hinders governance. The urban praxis of the VMG contradicts the formulated governance model and thecentralized dissolution of the local government and hybrid city are socio-spatial and politically unsustainable. Multiscale governance strategies are proposed to recreate social cohesion and a management planning innovative method (EG [PG] + i) to orchestrate, from the Local Governance Council (LGC) and with the participation of sublocal governments and spaces, a shared and sustainable city project.

Influencia del ruido de fondo en ambientes universitarios sobre los procesos cognitivos básicos

En este trabajo, se presenta un estudio cuyo objetivo fue determinar la influencia del ruido de fondo producido dentro de instalaciones universitarias sobre procesos cognitivos básicos tales como: la percepción y la atención. Se realizaron grabaciones de ruido de fondo en aulas de clase, bibliotecas, etc., para luego exponer a estudiantes universitarios a estos ambientes sonoros. Se registró la actividad cerebral a través de electroencefalografías (EEG), estudiando los cambios en las bandas de frecuencia relacionadas con procesos atencionales (beta 13-30 Hz. y theta 4-7 Hz.). Los resultados preliminares aquí presentados, muestran un decremento en estas bandas al exponer a los voluntarios a ruido de fondo. Así mismo, se aplicó una prueba psicométrica para determinar cambios en la atención. Los resultados obtenidos en esta prueba, no permiten relacionar directamente la influencia del ruido de fondo sobre los procesos atencionales.

Altered brain rhythms and functional network disruptions involved in patients with generalized fixation-off epilepsy

Fixation-off sensitivity (FOS) denotes the forms of epilepsy elicited by elimination of fixation. FOS-IGE patients are rare cases [1]. In a previous work [2] we showed that two FOS-IGE patients had different altered EEG rhythms when closing eyes; only beta band was altered in patient 1 while theta, alpha and beta were altered in patient 2. In the present work, we explain the relationship between the altered brain rhythms in these patients and the disruption in functional brain networks.

HERMES: Towards an Integrated Toolbox to Characterize Functional and Effective Brain Connectivity

The analysis of the interdependence between time series has become an important field of research in the last years, mainly as a result of advances in the characterization of dynamical systems from the signals they produce, the introduction of concepts such as generalized and phase synchronization and the application of information theory to time series analysis. In neurophysiology, different analytical tools stemming from these concepts have added to the ‘traditional’ set of linear methods, which includes the cross-correlation and the coherency function in the time and frequency domain, respectively, or more elaborated tools such as Granger Causality. This increase in the number of approaches to tackle the existence of functional (FC) or effective connectivity (EC) between two (or among many) neural networks, along with the mathematical complexity of the corresponding time series analysis tools, makes it desirable to arrange them into a unified-easy-to-use software package. The goal is to allow neuroscientists, neurophysiologists and researchers from related fields to easily access and make use of these analysis methods from a single integrated toolbox. Here we present HERMES (http://hermes.ctb.upm.es), a toolbox for the Matlab® environment (The Mathworks, Inc), which is designed to study functional and effective brain connectivity from neurophysiological data such as multivariate EEG and/or MEG records. It includes also visualization tools and statistical methods to address the problem of multiple comparisons. We believe that this toolbox will be very helpful to all the researchers working in the emerging field of brain connectivity analysis.

HERMES: towards an integrated toolbox to characterize functional and effective brain connectivity

The analysis of the interdependence between time series has become an important field of research in the last years, mainly as a result of advances in the characterization of dynamical systems from the signals they produce, the introduction of concepts such as generalized and phase synchronization and the application of information theory to time series analysis. In neurophysiology, different analytical tools stemming from these concepts have added to the ?traditional? set of linear methods, which includes the cross-correlation and the coherency function in the time and frequency domain, respectively, or more elaborated tools such as Granger Causality. This increase in the number of approaches to tackle the existence of functional (FC) or effective connectivity (EC) between two (or among many) neural networks, along with the mathematical complexity of the corresponding time series analysis tools, makes it desirable to arrange them into a unified, easy-to-use software package. The goal is to allow neuroscientists, neurophysiologists and researchers from related fields to easily access and make use of these analysis methods from a single integrated toolbox. Here we present HERMES (http://hermes.ctb.upm.es), a toolbox for the Matlab® environment (The Mathworks, Inc), which is designed to study functional and effective brain connectivity from neurophysiological data such as multivariate EEG and/or MEG records. It includes also visualization tools and statistical methods to address the problem of multiple comparisons. We believe that this toolbox will be very helpful to all the researchers working in the emerging field of brain connectivity analysis.

FocusDET, a new toolbox for SISCOM analysis. Evaluation of the registration accuracy using monte carlo simulation

Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epilepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate realistic SPECT studies. Simulated sinograms were reconstructed by using the Filtered BackProjection (FBP) algorithm and an Ordered Subsets Expectation Maximization (OSEM) reconstruction method that included compensation for all degradations. Registration errors in SPECT-SPECT and SPECT-MRI registration were evaluated by comparing the theoretical and actual transforms. Patient studies with well-localized epilepsy were also included in the registration assessment. Global registration errors including SPECT-SPECT and SPECT-MRI registration errors were less than 1.2 mm on average, exceeding the voxel size (3.32 mm) of SPECT studies in no case. Although images reconstructed using OSEM led to lower registration errors than images reconstructed with FBP, differences after using OSEM or FBP in reconstruction were less than 0.2 mm on average. This indicates that correction for degradations does not play a major role in the SISCOM process, thereby facilitating the application of the methodology in centers where OSEM is not implemented with correction of all degradations. These findings together with those obtained by clinicians from patients via MRI, interictal and ictal SPECT and video-EEG, show that FocusDET is a robust application for performing SISCOM analysis in clinical practice.