In this technical note, we introduce a new method for estimating changes in respiratory volume per unit time (RVT) from respiratory bellows recordings. By using techniques from the electrophysiological literature, in particular the Hilbert transform, we show how we can better characterise breathing rhythms, with the goal of improving physiological noise correction in functional magnetic resonance imaging (fMRI). Specifically, our approach leads to a representation with higher time resolution and better captures atypical breathing events than current peak-based RVT estimators. Finally, we demonstrate that this leads to an increase in the amount of respiration-related variance removed from fMRI data when used as part of a typical preprocessing pipeline. Our implementation is publicly available as part of the PhysIO package, which is distributed as part of the open-source TAPAS toolbox (https://translationalneuromodeling.org/tapas).
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http://dx.doi.org/10.1016/j.neuroimage.2021.117787 | DOI Listing |
Int J Neural Syst
May 2022
Computer Engineering Department, Nevsehir Hacı Bektas Veli University, Nevsehir, Turkey.
Currently, Fourier-based, wavelet-based, and Hilbert-based time-frequency techniques have generated considerable interest in classification studies for emotion recognition in human-computer interface investigations. Empirical mode decomposition (EMD), one of the Hilbert-based time-frequency techniques, has been developed as a tool for adaptive signal processing. Additionally, the multi-variate version strongly influences designing the common oscillation structure of a multi-channel signal by utilizing the common instantaneous concepts of frequency and bandwidth.
View Article and Find Full Text PDFJ Neural Eng
February 2022
Department of Neuroscience, Imaging and Clinical Sciences, Gabriele d'Annunzio University of Chieti-Pescara, Chieti, Italy.
. Being able to characterize functional connectivity (FC) state dynamics in a real-time setting, such as in brain-computer interface, neurofeedback or closed-loop neurostimulation frameworks, requires the rapid detection of the statistical dependencies that quantify FC in short windows of data. The aim of this study is to characterize, through extensive realistic simulations, the reliability of FC estimation as a function of the data length.
View Article and Find Full Text PDFNeuroimage
April 2021
Translational Neuromodeling Unit, University of Zurich & ETH Zurich, Zurich, Switzerland; Institute for Biomedical Engineering, ETH Zurich & University of Zurich, Zurich, Switzerland; Techna Institute, University Health Network, Toronto, Canada.
In this technical note, we introduce a new method for estimating changes in respiratory volume per unit time (RVT) from respiratory bellows recordings. By using techniques from the electrophysiological literature, in particular the Hilbert transform, we show how we can better characterise breathing rhythms, with the goal of improving physiological noise correction in functional magnetic resonance imaging (fMRI). Specifically, our approach leads to a representation with higher time resolution and better captures atypical breathing events than current peak-based RVT estimators.
View Article and Find Full Text PDFCirc Arrhythm Electrophysiol
October 2015
From the Arrhythmia Unit, Hospital Universitario Central de Asturias, Oviedo, Spain (D.C., J.R.); Center for Arrhythmia Research, University of Michigan, Ann Arbor (J.J., O.B.); Arrhythmia Unit, Hospital General Universitario Gregorio Marañón, Madrid, Spain (F.A., P.Á., Á.A.); Centro de Investigación e Innovación en Bioingeniería, Ci2B, Universitat Politècnica de Valencia, Valencia, Spain (J.S., L.M., A.F.); Arrhythmia Unit, Hospital Río Hortega de Valladolid and Universitario de Burgos, Valladolid-Burgos, Spain (B.H., J.G.-F.); Universitat de Valencia, Valencia, Spain (R.S.); and Department of Statistics, Hospital Universitario Central de Asturias, Oviedo, Spain (P.M.-C.).
Background: Ventricular fibrillation (VF) has been proposed to be maintained by localized high-frequency sources. We tested whether spectral-phase analysis of the precordial ECG enabled identification of periodic activation patterns generated by such sources.
Methods And Results: Precordial ECGs were recorded from 15 ischemic cardiomyopathy and 15 Brugada syndrome (type 1 ECG) patients during induced VF and analyzed in the frequency-phase domain.
Phys Rev E Stat Nonlin Soft Matter Phys
July 2011
Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China.
In this paper we present an extended version of Hilbert-Huang transform, namely arbitrary-order Hilbert spectral analysis, to characterize the scale-invariant properties of a time series directly in an amplitude-frequency space. We first show numerically that due to a nonlinear distortion, traditional methods require high-order harmonic components to represent nonlinear processes, except for the Hilbert-based method. This will lead to an artificial energy flux from the low-frequency (large scale) to the high-frequency (small scale) part.
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