fMRI activation detection with EEG priors

The purpose of brain mapping techniques is to advance the understanding of the relationship between structure and function in the human brain in so-called activation studies. In this work, an advanced statistical model for combining functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) recordings is developed to fuse complementary information about the location of neuronal activity. More precisely, a new Bayesian method is proposed for enhancing fMRI activation detection by the use of EEG-based spatial prior information in stimulus based experimental paradigms. I.e., we model and analyse stimulus influence by a spatial Bayesian variable selection scheme, and extend existing high-dimensional regression methods by incorporating prior information on binary selection indicators via a latent probit regression with either a spatially-varying or constant EEG effect. Spatially-varying effects are regularized by intrinsic Markov random field priors. Inference is based on a full Bayesian Markov Chain Monte Carlo (MCMC) approach. Whether the proposed algorithm is able to increase the sensitivity of mere fMRI models is examined in both a real-world application and a simulation study. We observed, that carefully selected EEG--prior information additionally increases sensitivity in activation regions that have been distorted by a low signal-to-noise ratio

Mitigation Country Study for Germany

human development, climate change

Short-term and long-term effects of United Nations peace operations

Earlier studies have shown that United Nations peace operations make a positive contribution to peacebuilding efforts after civil wars. But do these effects carry over to the period after the peacekeepers leave? And how do the effects of UN peace operations interact with other determinants of peacebuilding in the long run? The author addresses these questions using a revised version of the Doyle and Sambanis dataset and applying different estimation methods to estimate the short-term and long-term effects of UN peace missions. He finds that UN missions have robust, positive effects on peacebuilding in the short term. UN missions can help parties implement peace agreements but the UN cannot fight wars, and UN operations contribute more to the quality of the peace where peace is based on participation, than to the longevity of the peace, where peace is simply the absence of war. The effects of UN missions are also felt in the long run, but they dissipate over time. What is missing in UN peacebuilding is a strategy to foster the self-sustaining economic growth that could connect increased participation with sustainable peace.Post Conflict Reintegration,Peace&Peacekeeping,International Affairs,Post Conflict Reconstruction,Politics and Government

Gradient‐enhanced TROSY described with Cartesian product operators

TROSY, Transverse Relaxation Optimized Spectroscopy, was developed more than a decade ago. Since that time, the 15 N‐ 1 H HSQC‐TROSY experiment has become the standard “fingerprint” correlation spectrum for proteins of high molecular weight. In addition, its implementation in protein triple resonance experiments has pushed the boundaries of NMR assignment up to about 100 kDa, making NMR a highly relevant technique in structural biology. TROSY exploits the dipole‐CSA cross‐correlated relaxation properties of the NH system and selects for the narrowest of the HSQC J‐correlation quartet in both dimensions. The original publications and reviews of TROSY use shift operators and/or single transition product operators to describe the TROSY coherence pathways selections. In this review, we offer a familiar Cartesian product operator approach to comprehensively describe all of the events in the modern TROSY pulse sequence such as multiplet selection, gradient coherence selection, gradient quadrature, and sensitivity enhancement. © 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38: 280–288, 2011.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88024/1/20228_ftp.pd

Validation of non-REM sleep stage decoding from resting state fMRI using linear support vector machines

A growing body of literature suggests that changes in consciousness are reflected in specific connectivity patterns of the brain as obtained from resting state fMRI (rs-fMRI). As simultaneous electroencephalography (EEG) is often unavailable, decoding of potentially confounding sleep patterns from rs-fMRI itself might be useful and improve data interpretation. Linear support vector machine classifiers were trained on combined rs-fMRI/EEG recordings from 25 subjects to separate wakefulness (S0) from non-rapid eye movement (NREM) sleep stages 1 (S1), 2 (S2), slow wave sleep (SW) and all three sleep stages combined (SX). Classifier performance was quantified by a leave-one-subject-out cross-validation (LOSO-CV) and on an independent validation dataset comprising 19 subjects. Results demonstrated excellent performance with areas under the receiver operating characteristics curve (AUCs) close to 1.0 for the discrimination of sleep from wakefulness (S0|SX), S0|S1, S0|S2 and S0|SW, and good to excellent performance for the classification between sleep stages (S1|S2:~0.9; S1|SW:~1.0; S2|SW:~0.8). Application windows of fMRI data from about 70 s were found as minimum to provide reliable classifications. Discrimination patterns pointed to subcortical-cortical connectivity and within-occipital lobe reorganization of connectivity as strongest carriers of discriminative information. In conclusion, we report that functional connectivity analysis allows valid classification of NREM sleep stages

Frontoparietal Connectivity and Hierarchical Structure of the Brain’s Functional Network during Sleep

Frontal and parietal regions are associated with some of the most complex cognitive functions, and several frontoparietal resting-state networks can be observed in wakefulness. We used functional magnetic resonance imaging data acquired in polysomnographically validated wakefulness, light sleep, and slow-wave sleep to examine the hierarchical structure of a low-frequency functional brain network, and to examine whether frontoparietal connectivity would disintegrate in sleep. Whole-brain analyses with hierarchical cluster analysis on predefined atlases were performed, as well as regression of inferior parietal lobules (IPL) seeds against all voxels in the brain, and an evaluation of the integrity of voxel time-courses in subcortical regions-of-interest. We observed that frontoparietal functional connectivity disintegrated in sleep stage 1 and was absent in deeper sleep stages. Slow-wave sleep was characterized by strong hierarchical clustering of local submodules. Frontoparietal connectivity between IPL and superior medial and right frontal gyrus was lower in sleep stages than in wakefulness. Moreover, thalamus voxels showed maintained integrity in sleep stage 1, making intrathalamic desynchronization an unlikely source of reduced thalamocortical connectivity in this sleep stage. Our data suggest a transition from a globally integrated functional brain network in wakefulness to a disintegrated network consisting of local submodules in slow-wave sleep, in which frontoparietal inter-modular nodes may play a role, possibly in combination with the thalamus

Tau protein is essential for stress-induced brain pathology

Exposure to chronic stress is frequently accompanied by cognitive and affective disorders in association with neurostructural adaptations. Chronic stress was previously shown to trigger Alzheimer's-like neuropathology, which is characterized by Tau hyper-phosphorylation and missorting into dendritic spines followed by memory deficits. Here, we demonstrate that stress-driven hippocampal deficits in wild-type mice are accompanied by synaptic missorting of Tau and enhanced Fyn/GluN2B-driven synaptic signaling. In contrast, mice lacking Tau [Tau knockout (Tau-KO) mice] do not exhibit stress-induced pathological behaviors and atrophy of hippocampal dendrites or deficits of hippocampal connectivity. These findings implicate Tau as an essential mediator of the adverse effects of stress on brain structure and function.We thank Dr. Peter Davies (Albert Einstein College) for the PHF1 antibody. This work was funded by Portuguese Foundation for Science & Technology (FCT) Grants PTDC/SAU-NMC/113934/2009 (to I.S.); the European Union FP7 Project SwitchBox (N.S. and O.F.X.A.); the Portuguese North Regional Operational Program (ON.2-O Novo Norte) under the National Strategic Reference Framework (QREN) through the European Regional Development Fund (FEDER); and the Education and Lifelong Learning, Supporting Postdoctoral Researchers and Large Scale Cooperative Project, cofinanced by the European Social Fund and the Greek General Secretariat for Research and Technology. J.V.-S. is a recipient of a PhD fellowship (PD/BD/105938/2014) of the University of Minho MD/PhD Program funded by the FCT

Unstable Prefrontal Response to Emotional Conflict and Activation of Lower Limbic Structures and Brainstem in Remitted Panic Disorder

Background: The neural mechanisms of panic disorder (PD) are only incompletely understood. Higher sensitivity of patients to unspecific fear cues and similarities to conditioned fear suggest involvement of lower limbic and brainstem structures. We investigated if emotion perception is altered in remitted PD as a trait feature. Methodology/Principal Findings: We used blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to study neural and behavioural responses of 18 remitted PD patients and 18 healthy subjects to the emotional conflict paradigm that is based on the presentation of emotionally congruent and incongruent face/word pairs. We observed that patients showed stronger behavioural interference and lower adaptation to interference conflict. Overall performance in patients was slower but not less accurate. In the context of preceding congruence, stronger dorsal anterior cingulate cortex (dACC) activation during conflict detection was found in patients. In the context of preceding incongruence, controls expanded dACC activity and succeeded in reducing behavioural interference. In contrast, patients demonstrated a dropout of dACC and dorsomedial prefrontal cortex (dmPFC) recruitment but activation of the lower limbic areas (including right amygdala) and brainstem. Conclusions/Significance: This study provides evidence that stimulus order in the presentation of emotional stimuli has a markedly larger influence on the brain’s response in remitted PD than in controls, leading to abnormal responses of th