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Brain Dynamics

The Experts below are selected from a list of 6717 Experts worldwide ranked by ideXlab platform

F.-xavier Alario – 1st expert on this subject based on the ideXlab platform

  • Response-Locked Brain Dynamics of Word Production
    PLoS ONE, 2013
    Co-Authors: Stéphanie Riès, Niels Janssen, Boris Burle, F.-xavier Alario

    Abstract:

    The cortical regions involved in the different stages of speech production are relatively well-established, but their spatio-temporal Dynamics remain poorly understood. In particular, the available studies have characterized neural events with respect to the onset of the stimulus triggering a verbal response. The core aspect of language production, however, is not perception but action. In this context, the most relevant question may not be how long after a stimulus Brain events happen, but rather how long before the production act do they occur. We investigated speech production-related Brain activity time-locked to vocal onset, in addition to the common stimulus-locked approach. We report the detailed temporal interplay between medial and left frontal activities occurring shortly before vocal onset. We interpret those as reflections of, respectively, word selection and word production processes. This medial-lateral organization is in line with that described in non-linguistic action control, suggesting that similar processes are at play in word production and non-linguistic action production. This novel view of the Brain Dynamics underlying word production provides a useful background for future investigations of the spatio-temporal Brain Dynamics that lead to the production of verbal responses. Citation: Riès S, Janssen N, Burle B, Alario F-X (2013) Response-Locked Brain Dynamics of Word Production. PLoS ONE 8(3): e58197.

  • Response-locked Brain Dynamics of word production.
    PLOS ONE, 2013
    Co-Authors: Stéphanie Riès, Niels Janssen, Boris Burle, F.-xavier Alario

    Abstract:

    The cortical regions involved in the different stages of speech production are relatively well-established, but their spatio-temporal Dynamics remain poorly understood. In particular, the available studies have characterized neural events with respect to the onset of the stimulus triggering a verbal response. The core aspect of language production, however, is not perception but action. In this context, the most relevant question may not be how long after a stimulus Brain events happen, but rather how long before the production act do they occur. We investigated speech production-related Brain activity time-locked to vocal onset, in addition to the common stimulus-locked approach. We report the detailed temporal interplay between medial and left frontal activities occurring shortly before vocal onset. We interpret those as reflections of, respectively, word selection and word production processes. This medial-lateral organization is in line with that described in non-linguistic action control, suggesting that similar processes are at play in word production and non-linguistic action production. This novel view of the Brain Dynamics underlying word production provides a useful background for future investigations of the spatio-temporal Brain Dynamics that lead to the production of verbal responses. Citation: Ries S, Janssen N, Burle B, Alario F-X (2013) Response-Locked Brain Dynamics of Word Production. PLoS ONE 8(3): e58197.

S. Zeki – 2nd expert on this subject based on the ideXlab platform

  • Brain Dynamics during natural viewing conditions a new guide for mapping connectivity in vivo
    NeuroImage, 2005
    Co-Authors: A Bartels, S. Zeki

    Abstract:

    We describe here a new way of obtaining maps of connectivity in the human Brain based on interregional correlations of blood oxygen level-dependent (BOLD) signal during natural viewing conditions. We propose that anatomical connections are reflected in BOLD signal correlations during natural Brain Dynamics. This may provide a powerful approach to chart connectivity, more so than that based on the ‘resting state’ of the human Brain, and it may complement diffusion tensor imaging. Our approach relies on natural Brain Dynamics and is therefore experimentally unbiased and independent of hypothesis-driven, specialized stimuli. It has the advantage that natural viewing leads to considerably stronger cortical activity than rest, thus facilitating detection of weaker connections. To validate our technique, we used functional magnetic resonance imaging (fMRI) to record BOLD signal while volunteers freely viewed a movie that was interrupted by resting periods. We used independent component analysis (ICA) to segregate cortical areas before characterizing the Dynamics of their BOLD signal during free viewing and rest. Natural viewing and rest each revealed highly specific correlation maps, which reflected known anatomical connections. Examples are homologous regions in visual and auditory cortices in the two hemispheres and the language network consisting of Wernicke’s area, Broca’s area, and a premotor region. Correlations between regions known to be directly connected were always substantially higher than between nonconnected regions. Furthermore, compared to rest, natural viewing specifically increased correlations between anatomically connected regions while it decreased correlations between nonconnected regions. Our findings therefore demonstrate that natural viewing conditions lead to particularly specific interregional correlations and thus provide a powerful environment to reveal anatomical connectivity in vivo.

  • Brain Dynamics during natural viewing conditions – A new guide for mapping connectivity in vivo
    NEUROIMAGE, 2005
    Co-Authors: S. Zeki

    Abstract:

    We describe here a new way of obtaining maps of connectivity in the human Brain based on interregional correlations of blood oxygen level-dependent (BOLD) signal during natural viewing conditions. We propose that anatomical connections are reflected in BOLD signal correlations during natural Brain Dynamics. This may provide a powerful approach to chart connectivity, more so than that based on the ‘resting state’ of the human Brain, and it may complement diffusion tensor imaging. Our approach relies on natural Brain Dynamics and is therefore experimentally unbiased and independent of hypothesis-driven, specialized stimuli. It has the advantage that natural viewing leads to considerably stronger cortical activity than rest, thus facilitating detection of weaker connections. To validate our technique, we used functional magnetic resonance imaging (fMRI) to record BOLD signal while volunteers freely viewed a movie that was interrupted by resting periods. We used independent component analysis (ICA) to segregate cortical areas before characterizing the Dynamics of their BOLD signal during free viewing and rest. Natural viewing and rest each revealed highly specific correlation maps, which reflected known anatomical connections. Examples are homologous regions in visual and auditory cortices in the two hemispheres and the language network consisting of Wernicke’s area, Broca’s area, and a premotor region. Correlations between regions known to be directly connected were always substantially higher than between nonconnected regions. Furthermore, compared to rest, natural viewing specifically increased correlations between anatomically connected regions while it decreased correlations between nonconnected regions. Our findings therefore demonstrate that natural viewing conditions lead to particularly specific interregional correlations and thus provide a powerful environment to reveal anatomical connectivity in vivo. (C) 2004 Elsevier Inc. All rights reserved.

Wen Ju Pan – 3rd expert on this subject based on the ideXlab platform

  • Instantaneous Brain Dynamics mapped to a continuous state space
    NeuroImage, 2017
    Co-Authors: Jacob C.w. Billings, Arunima Medda, Sadia Shakil, Xiaohong Shen, Amrit Kashyap, Shiyang Chen, Anzar Abbas, Xiaodi Zhang, Maysam Nezafati, Wen Ju Pan

    Abstract:

    Measures of whole-Brain activity, from techniques such as functional Magnetic Resonance Imaging, provide a means to observe the Brain‘s dynamical operations. However, interpretation of whole-Brain Dynamics has been stymied by the inherently high-dimensional structure of Brain activity. The present research addresses this challenge through a series of scale transformations in the spectral, spatial, and relational domains. Instantaneous multispectral Dynamics are first developed from input data via a wavelet filter bank. Voxel-level signals are then projected onto a representative set of spatially independent components. The correlation distance over the instantaneous wavelet-ICA state vectors is a graph that may be embedded onto a lower-dimensional space to assist the interpretation of state-space Dynamics. Applying this procedure to a large sample of resting-state and task-active data (acquired through the Human Connectome Project), we segment the empirical state space into a continuum of stimulus-dependent Brain states. Upon observing the local neighborhood of Brain-states adopted subsequent to each stimulus, we may conclude that resting Brain activity includes Brain states that are, at times, similar to those adopted during tasks, but that are at other times distinct from task-active Brain states. As task-active Brain states often populate a local neighborhood, back-projection of segments of the dynamical state space onto the Brain‘s surface reveals the patterns of Brain activity that support many experimentally-defined states.