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Zirui Huang - One of the best experts on this subject based on the ideXlab platform.

  • timescales of intrinsic bold Signal dynamics and functional connectivity in pharmacologic and neuropathologic states of unconsciousness
    The Journal of Neuroscience, 2018
    Co-Authors: Zirui Huang, George A Mashour, Anthony G Hudetz
    Abstract:

    Environmental events are processed on multiple timescales via hierarchical organization of temporal receptive windows (TRWs) in the brain. The dependence of neural timescales and TRWs on altered states of consciousness is unclear. States of reduced consciousness are marked by a shift toward slowing of neural dynamics ( SIGNIFICANCE STATEMENT Information processing in the brain occurs through a hierarchy of temporal receptive windows (TRWs) in multiple timescales. Anesthetic drugs induce a reversible suppression of consciousness and thus offer a unique opportunity to investigate the state dependence of neural timescales. Here, we demonstrate for the first time that sedation with propofol is accompanied by the prolongation of the timescales of intrinsic BOLD Signals presumably reflecting enlarged TRWs. We show that this is accomplished by an increase of local and regional Signal Synchronization, effects that may disrupt information exchange among distant brain regions. Furthermore, we show that the timescales of intrinsic BOLD Signals exhibit distinct dynamic signatures in sedation, deep anesthesia, and disorders of consciousness.

  • decoupled temporal variability and Signal Synchronization of spontaneous brain activity in loss of consciousness an fmri study in anesthesia
    NeuroImage, 2016
    Co-Authors: Zirui Huang, Jun Zhang, Jinsong Wu, Xuehai Wu, Zhiyao Wang, Yuan Li, Weimin Liang, Zhong Yang, Jianfeng Zhang
    Abstract:

    Abstract Two aspects of the low frequency fluctuations of spontaneous brain activity have been proposed which reflect the complex and dynamic features of resting-state activity, namely temporal variability and Signal Synchronization. The relationship between them, especially its role in consciousness, nevertheless remains unclear. Our study examined the temporal variability and Signal Synchronization of spontaneous brain activity, as well as their relationship during loss of consciousness. We applied an intra-subject design of resting-state functional magnetic resonance imaging (rs-fMRI) in two conditions: during wakefulness, and under anesthesia with clinical unconsciousness. In addition, an independent group of patients with disorders of consciousness (DOC) was included in order to test the reliability of our findings. We observed a global reduction in the temporal variability, local and distant brain Signal Synchronization for subjects during anesthesia. Importantly, we found a link between temporal variability and both local and distant Signal Synchronizations during wakefulness: the higher the degree of temporal variability, the higher its intra-regional homogeneity and inter-regional functional connectivity. In contrast, this link was broken down under anesthesia, implying a decoupling between temporal variability and Signal Synchronization; this decoupling was reproduced in patients with DOC. Our results suggest that there exist some as yet unclear physiological mechanisms of consciousness which “couple” the two mathematically independent measures, temporal variability and Signal Synchronization of spontaneous brain activity. Our findings not only extend our current knowledge of the neural correlates of anesthetic-induced unconsciousness, but have implications for both computational neural modeling and clinical practice, such as in the diagnosis of loss of consciousness in patients with DOC.

Alkiviadis Gourgiotis - One of the best experts on this subject based on the ideXlab platform.

  • Deconvolution of the isotopic drift in LC-MC-ICPMS coupling: a new tool for studding isotope fractionation induced by sample introduction techniques.
    Journal of Analytical Atomic Spectrometry, 2017
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Banoit Martelat, Hélène Isnard
    Abstract:

    On-line hyphenated methods between the Multi Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and a variety of introduction techniques (liquid and gas chromatography, laser ablation…) provide transient Signals with specific time-windows. It is now well-known that the isotope ratio drift which is observed during transient Signal acquisition is generated from the MC-ICPMS detection system, the introduction techniques, or a combination of both parameters. In this work, the Nd isotope ratios were investigated through a coupling of the MC-ICPMS with Liquid Chromatography (LC). The purpose was to dissociate the isotopic drift coming from the detection system to the drift caused by the introduction technique by using raw isotope data. To this end, the time constants of the MC-ICPMS amplifiers were used, and the isotope drift generated by the detection system was successfully corrected. After this correction, the isotope drift coming exclusively from the LC was highlighted. The use of the Method of Internal Signal Synchronization (MISS) allowed the correction of the chromatographic drift and the calculation of a time lag between the Nd isotopes at 0.0036 s / amu. This is the first time where for an isotope fractionation caused by a specific physicochemical process, a time lag between the isotopes was calculated. We believe that the calculation of time lag values between the isotopes could be a simple and robust method opening up new possibilities for studies of isotope fractionations generated by different introduction techniques directly coupled with the MC-ICPMS.

  • Transient Signal isotope analysis: validation of the method for isotope Signal Synchronization with the determination of amplifier first-order time constants.
    Rapid Communications in Mass Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    Rationale During transient Signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier Signal Synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier Signal Synchronization for isotope ratio drift correction. Methods Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient Signals and the Signal decay curves of the amplifiers were investigated. Results Our results show that the first part of the amplifier Signal decay curve is characterized by a pure exponential decay. This part of the Signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope Signal Synchronization and were found to be in good agreement. Conclusions This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier Signal Synchronization for isotope ratio drift correction is validated. Copyright © 2015 John Wiley & Sons, Ltd.

  • Transient Signal isotope analysis using multicollection of ion beams with Faraday cups equipped with 10 12 Ω and 10 11 Ω feedback resistors
    Journal of Analytical Atomic Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    To improve the precision of isotope analyses of low ion intensities using the Faraday detection system, amplifiers equipped with 10(12) Omega resistors (hereafter 10(12) Omega amplifiers) have been developed. While the behavior of these amplifiers for steady Signals has been well investigated, there is no ample evidence regarding the use of 10(12) Omega amplifiers for transient Signal acquisition. In this work, we investigated the simultaneous use of amplifiers equipped with 10(12) Omega and 10(11) Omega resistors for transient Signal acquisition. Using the equation describing the relationship between the input ion current and the output voltage in the amplifiers, we showed how the transient Signal duration influences the accuracy of the isotope ratio measurements. In particular, lead transient Signals were investigated using a Neptune Plus MC-ICPMS and Pb-204 and Pb-206 isotopes were measured using 10(12) Omega and 10(11) Omega amplifiers, respectively. The Pb-204/Pb-206 isotope ratio showed an important drift due to a large time lag between 10(12) Omega and 10(11) Omega amplifiers. The time lag was quantified (0.175(3) s) and the isotopic drift was corrected using a method of internal Signal Synchronization. The Pb-204/Pb-206 drift corrected data obtained from the 10(12)-10(11) Omega amplifier configuration were compared to the data obtained from 10(11)-10(11) Omega amplifiers. Our results point out that for low transient Signal intensities (

Jérôme Gaillardet - One of the best experts on this subject based on the ideXlab platform.

  • Transient Signal isotope analysis: validation of the method for isotope Signal Synchronization with the determination of amplifier first-order time constants.
    Rapid Communications in Mass Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    Rationale During transient Signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier Signal Synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier Signal Synchronization for isotope ratio drift correction. Methods Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient Signals and the Signal decay curves of the amplifiers were investigated. Results Our results show that the first part of the amplifier Signal decay curve is characterized by a pure exponential decay. This part of the Signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope Signal Synchronization and were found to be in good agreement. Conclusions This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier Signal Synchronization for isotope ratio drift correction is validated. Copyright © 2015 John Wiley & Sons, Ltd.

  • Transient Signal isotope analysis using multicollection of ion beams with Faraday cups equipped with 10 12 Ω and 10 11 Ω feedback resistors
    Journal of Analytical Atomic Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    To improve the precision of isotope analyses of low ion intensities using the Faraday detection system, amplifiers equipped with 10(12) Omega resistors (hereafter 10(12) Omega amplifiers) have been developed. While the behavior of these amplifiers for steady Signals has been well investigated, there is no ample evidence regarding the use of 10(12) Omega amplifiers for transient Signal acquisition. In this work, we investigated the simultaneous use of amplifiers equipped with 10(12) Omega and 10(11) Omega resistors for transient Signal acquisition. Using the equation describing the relationship between the input ion current and the output voltage in the amplifiers, we showed how the transient Signal duration influences the accuracy of the isotope ratio measurements. In particular, lead transient Signals were investigated using a Neptune Plus MC-ICPMS and Pb-204 and Pb-206 isotopes were measured using 10(12) Omega and 10(11) Omega amplifiers, respectively. The Pb-204/Pb-206 isotope ratio showed an important drift due to a large time lag between 10(12) Omega and 10(11) Omega amplifiers. The time lag was quantified (0.175(3) s) and the isotopic drift was corrected using a method of internal Signal Synchronization. The Pb-204/Pb-206 drift corrected data obtained from the 10(12)-10(11) Omega amplifier configuration were compared to the data obtained from 10(11)-10(11) Omega amplifiers. Our results point out that for low transient Signal intensities (

Gérard Manhès - One of the best experts on this subject based on the ideXlab platform.

  • Deconvolution of the isotopic drift in LC-MC-ICPMS coupling: a new tool for studding isotope fractionation induced by sample introduction techniques.
    Journal of Analytical Atomic Spectrometry, 2017
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Banoit Martelat, Hélène Isnard
    Abstract:

    On-line hyphenated methods between the Multi Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and a variety of introduction techniques (liquid and gas chromatography, laser ablation…) provide transient Signals with specific time-windows. It is now well-known that the isotope ratio drift which is observed during transient Signal acquisition is generated from the MC-ICPMS detection system, the introduction techniques, or a combination of both parameters. In this work, the Nd isotope ratios were investigated through a coupling of the MC-ICPMS with Liquid Chromatography (LC). The purpose was to dissociate the isotopic drift coming from the detection system to the drift caused by the introduction technique by using raw isotope data. To this end, the time constants of the MC-ICPMS amplifiers were used, and the isotope drift generated by the detection system was successfully corrected. After this correction, the isotope drift coming exclusively from the LC was highlighted. The use of the Method of Internal Signal Synchronization (MISS) allowed the correction of the chromatographic drift and the calculation of a time lag between the Nd isotopes at 0.0036 s / amu. This is the first time where for an isotope fractionation caused by a specific physicochemical process, a time lag between the isotopes was calculated. We believe that the calculation of time lag values between the isotopes could be a simple and robust method opening up new possibilities for studies of isotope fractionations generated by different introduction techniques directly coupled with the MC-ICPMS.

  • Transient Signal isotope analysis: validation of the method for isotope Signal Synchronization with the determination of amplifier first-order time constants.
    Rapid Communications in Mass Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    Rationale During transient Signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier Signal Synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier Signal Synchronization for isotope ratio drift correction. Methods Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient Signals and the Signal decay curves of the amplifiers were investigated. Results Our results show that the first part of the amplifier Signal decay curve is characterized by a pure exponential decay. This part of the Signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope Signal Synchronization and were found to be in good agreement. Conclusions This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier Signal Synchronization for isotope ratio drift correction is validated. Copyright © 2015 John Wiley & Sons, Ltd.

  • Transient Signal isotope analysis using multicollection of ion beams with Faraday cups equipped with 10 12 Ω and 10 11 Ω feedback resistors
    Journal of Analytical Atomic Spectrometry, 2015
    Co-Authors: Alkiviadis Gourgiotis, Gérard Manhès, Pascale Louvat, Julien Moureau, Jérôme Gaillardet
    Abstract:

    To improve the precision of isotope analyses of low ion intensities using the Faraday detection system, amplifiers equipped with 10(12) Omega resistors (hereafter 10(12) Omega amplifiers) have been developed. While the behavior of these amplifiers for steady Signals has been well investigated, there is no ample evidence regarding the use of 10(12) Omega amplifiers for transient Signal acquisition. In this work, we investigated the simultaneous use of amplifiers equipped with 10(12) Omega and 10(11) Omega resistors for transient Signal acquisition. Using the equation describing the relationship between the input ion current and the output voltage in the amplifiers, we showed how the transient Signal duration influences the accuracy of the isotope ratio measurements. In particular, lead transient Signals were investigated using a Neptune Plus MC-ICPMS and Pb-204 and Pb-206 isotopes were measured using 10(12) Omega and 10(11) Omega amplifiers, respectively. The Pb-204/Pb-206 isotope ratio showed an important drift due to a large time lag between 10(12) Omega and 10(11) Omega amplifiers. The time lag was quantified (0.175(3) s) and the isotopic drift was corrected using a method of internal Signal Synchronization. The Pb-204/Pb-206 drift corrected data obtained from the 10(12)-10(11) Omega amplifier configuration were compared to the data obtained from 10(11)-10(11) Omega amplifiers. Our results point out that for low transient Signal intensities (

Jianfeng Zhang - One of the best experts on this subject based on the ideXlab platform.

  • decoupled temporal variability and Signal Synchronization of spontaneous brain activity in loss of consciousness an fmri study in anesthesia
    NeuroImage, 2016
    Co-Authors: Zirui Huang, Jun Zhang, Jinsong Wu, Xuehai Wu, Zhiyao Wang, Yuan Li, Weimin Liang, Zhong Yang, Jianfeng Zhang
    Abstract:

    Abstract Two aspects of the low frequency fluctuations of spontaneous brain activity have been proposed which reflect the complex and dynamic features of resting-state activity, namely temporal variability and Signal Synchronization. The relationship between them, especially its role in consciousness, nevertheless remains unclear. Our study examined the temporal variability and Signal Synchronization of spontaneous brain activity, as well as their relationship during loss of consciousness. We applied an intra-subject design of resting-state functional magnetic resonance imaging (rs-fMRI) in two conditions: during wakefulness, and under anesthesia with clinical unconsciousness. In addition, an independent group of patients with disorders of consciousness (DOC) was included in order to test the reliability of our findings. We observed a global reduction in the temporal variability, local and distant brain Signal Synchronization for subjects during anesthesia. Importantly, we found a link between temporal variability and both local and distant Signal Synchronizations during wakefulness: the higher the degree of temporal variability, the higher its intra-regional homogeneity and inter-regional functional connectivity. In contrast, this link was broken down under anesthesia, implying a decoupling between temporal variability and Signal Synchronization; this decoupling was reproduced in patients with DOC. Our results suggest that there exist some as yet unclear physiological mechanisms of consciousness which “couple” the two mathematically independent measures, temporal variability and Signal Synchronization of spontaneous brain activity. Our findings not only extend our current knowledge of the neural correlates of anesthetic-induced unconsciousness, but have implications for both computational neural modeling and clinical practice, such as in the diagnosis of loss of consciousness in patients with DOC.