3,326 research outputs found
The Added Value of EEG-fMRI in Imaging Neuroscience
No full textThe main objective of functional neuroimaging is to detect and characterize in space and time neurophysiologically relevant changes of brain states. Functional MRI (fMRI) and electro-encephalography (EEG) assume that a given brain state can be decoded from the precise anatomical localization and the detailed temporal evolution of neuro-electrical brain signals, respectively. Mapping brain states with fMRI at a spatial resolution in the millimeter range allows imaging neuroscientists to test diverse neurophysiological and neuropathological hypotheses in the normal and clinical populations. Simultaneously recorded EEG offers the possibility to greatly enrich topological results by tracking subjects’ state-representative patterns over time at the millisecond temporal scale. The main purpose of this chapter is to illustrate how the imaging neuroscientist can integrate detailed temporal information provided by simultaneously recorded EEG signals into fMRI spatio-temporal modeling. We discuss the problem of optimizing a common source space for fMRI and EEG signal projection through the use of anatomical and functional MRI models and EEG distributed inverse models, thereby gathering a fully integrated framework for the comparative analysis of simultaneously acquired EEG-fMRI data sets
Automated selection of brain regions for real-time fMRI brain-computer interfaces
No full textObjective. Brain-computer interfaces (BCIs) implemented with real-time functional magnetic resonance imaging (rt-fMRI) use fMRI time-courses from predefined regions of interest (ROIs). To reach best performances, localizer experiments and on-site expert supervision are required for ROI definition. To automate this step, we developed two unsupervised computational techniques based on the general linear model (GLM) and independent component analysis (ICA) of rt-fMRI data, and compared their performances on a communication BCI. Approach. 3 T fMRI data of six volunteers were re-analyzed in simulated real-time. During a localizer run, participants performed three mental tasks following visual cues. During two communication runs, a letter-spelling display guided the subjects to freely encode letters by performing one of the mental tasks with a specific timing. GLM- and ICA-based procedures were used to decode each letter, respectively using compact ROIs and whole-brain distributed spatio-temporal patterns of fMRI activity, automatically defined from subject-specific or group-level maps. Main results. Letter-decoding performances were comparable to supervised methods. In combination with a similarity-based criterion, GLM- and ICA-based approaches successfully decoded more than 80% (average) of the letters. Subject-specific maps yielded optimal performances. Significance. Automated solutions for ROI selection may help accelerating the translation of rt-fMRI BCIs from research to clinical applications
Classification of fMRI-independent components in a multidimensional feature space using least-square support vector machines
No full textSpatial independent component analysis of functional MRI time-series: to what extent do results depend on the algorithm used?
No full textDistributed analysis of simultaneous EEG-fMRI time-series: modeling and interpretation issues
No full textFunctional magnetic resonance imaging (fMRI) and electroencephalography (EEG) represent brain activity in terms of a reliable anatomical localization and a detailed temporal evolution of neural signals. Simultaneous EEG-fMRI recordings offer the possibility to greatly enrich the significance and the interpretation of the single modality results because the same neural processes are observed from the same brain at the same time. Nonetheless, the different physical nature of the measured signals by the two techniques renders the coupling not always straightforward, especially in cognitive experiments where spatially localized and distributed effects coexist and evolve temporally at different temporal scales. The purpose of this article is to illustrate the combination of simultaneously recorded EEG and fMRI signals exploiting the principles of EEG distributed source modeling. We define a common source space for fMRI and EEG signal projection and gather a conceptually unique framework for the spatial and temporal comparative analysis. We illustrate this framework in a graded-load working-memory simultaneous EEG-fMRI experiment based on the n-back task where sustained load-dependent changes in the blood-oxygenation-level-dependent (BOLD) signals during continuous item memorization co-occur with parametric changes in the EEG theta power induced at each single item. In line with previous studies, we demonstrate on two single-subject cases how the presented approach is capable of colocalizing in midline frontal regions two phenomena simultaneously observed at different temporal scales, such as the sustained negative changes in BOLD activity and the parametric EEG theta synchronization. We discuss the presented approach in relation to modeling and interpretation issues typically arising in simultaneous EEG-fMRI studies
Incursions of exotic pests into European rice areas - detection and management. [4127]
No full textThe total area under rice cultivation in the EU is about 450,000 ha and the main producers are Italy, Spain, Portugal, Greece and France. Due to the position of Europe in northern latitudes and its associated temperate climate, endemic local insect pests cause few problems to European rice production. In contrast, Invasive alien species (IAS) pose a significant threat to biodiversity in the EU, as they often have to be controlled with chemicals. Methods: The key IAS affecting rice in the EU, the damage they cause and the control measures that are required for their management are reviewed. The potential impact of these measures on aquatic biodiversity is examined, and alternative control strategies are discussed. Results/Conclusion: Key IAS affecting EU rice are Chilo suppressalis which is well established in Spain, Portugal and France, and Lissorhoptrus oryzophilus which was introduced to Italy in 2004 and France in 2015. Recently the polyphagous Halyomorpha halys was detected in rice areas in France (2012) and Italy (2014), but its role in rice paddies has yet to be evaluated. Rice crop management is focused on maximizing yield, however rice paddies also have conservation value, acting as surrogates for natural wetlands. Agricultural practices often include chemical applications aimed at controlling pest species, with adverse side effects on non-target aquatic invertebrates. There are potential alternatives to this approach which combine biological and agroecological control methods to optimize pest control, but with a reduced impact on the environment
Myosin-cross-reactive antigen (MCRA) protein from Bifidobacterium breve is a FAD-dependent fatty acid hydratase which has a function in stress protection
No full textpeer-reviewedBackground The aim of this study was to determine the catalytic activity and physiological role of myosin-cross-reactive antigen (MCRA) from Bifidobacterium breve NCIMB 702258. MCRA from B. breve NCIMB 702258 was cloned, sequenced and expressed in heterologous hosts (Lactococcus and Corynebacterium) and the recombinant proteins assessed for enzymatic activity against fatty acid substrates. Results MCRA catalysed the conversion of palmitoleic, oleic and linoleic acids to the corresponding 10-hydroxy fatty acids, but shorter chain fatty acids were not used as substrates, while the presence of trans-double bonds and double bonds beyond the position C12 abolished hydratase activity. The hydroxy fatty acids produced were not metabolised further. We also found that heterologous Lactococcus and Corynebacterium expressing MCRA accumulated increasing amounts of 10-HOA and 10-HOE in the culture medium. Furthermore, the heterologous cultures exhibited less sensitivity to heat and solvent stresses compared to corresponding controls. Conclusions MCRA protein in B. breve can be classified as a FAD-containing double bond hydratase, within the carbon-oxygen lyase family, which may be catalysing the first step in conjugated linoleic acid (CLA) production, and this protein has an additional function in bacterial stress protection
A multivariate approach for processing magnetization effects in triggered event-related functional magnetic resonance imaging time series
No full textTriggered event-related functional magnetic resonance imaging requires sparse intervals of temporally resolved functional data acquisitions, whose initiation corresponds to the occurrence of an event, typically an epileptic spike in the electroencephalographic trace. However, conventional fMRI time series are greatly affected by non-steady-state magnetization effects, which obscure initial blood oxygen level-dependent (BOLD) signals. Here, conventional echo-planar imaging and a post-processing solution based on principal component analysis were employed to remove the dominant eigenimages of the time series, to filter out the global signal changes induced by magnetization decay and to recover BOLD signals starting with the first functional volume. This approach was compared with a physical solution using radiofrequency preparation, which nullifies magnetization effects. As an application of the method, the detectability of the initial transient BOLD response in the auditory cortex, which is elicited by the onset of acoustic scanner noise, was used to demonstrate that post-processing-based removal of magnetization effects allows to detect brain activity patterns identical with those obtained using the radiofrequency preparation. Using the auditory responses as an ideal experimental model of triggered brain activity, our results suggest that reducing the initial magnetization effects by removing a few principal components from fMRI data may be potentially useful in the analysis of triggered event-related echo-planar time series. The implications of this study are discussed with special caution to remaining technical limitations and the additional neurophysiological issues of the triggered acquisition
- …
