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On spurious and real fluctuations of dynamic functional connectivity during rest

Résumé

Functional brain networks reconfigure spontaneously during rest. Such network dynamics can be studied by dynamic functional connectivity (dynFC); i.e., sliding-window correlations between regional brain activity. Key parameters-such as window length and cut-off frequencies for filtering-are not yet systematically studied. In this letter we provide the fundamental theory from signal processing to address these parameter choices when estimating and interpreting dynFC. We guide the reader through several illustrative cases, both simple analytical models and experimental fMRI BOLD data. First, we show how spurious fluctuations in dynFC can arise due to the estimation method when the window length is shorter than the largest wavelength present in both signals, even for deterministic signals with a fixed relationship. Second, we study how real fluctuations of dynFC can be explained using a frequency-based view, which is particularly instructive for signals with multiple frequency components such as fMRI BOLD, demonstrating that fluctuations in sliding-window correlation emerge by interaction between frequency components similar to the phenomenon of beat frequencies. We conclude with practical guidelines for the choice and impact of the window length. (C) 2014 Elsevier Inc. All rights reserved.

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Concepts associés (33)
Traitement du signal
Le traitement du signal est la discipline qui développe et étudie les techniques de traitement, d'analyse et d' des . Parmi les types d'opérations possibles sur ces signaux, on peut dénoter le contrôle, le filtrage, la compression et la transmission de données, la réduction du bruit, la déconvolution, la prédiction, l'identification, la classification Bien que cette discipline trouve son origine dans les sciences de l'ingénieur (particulièrement l'électronique et l'automatique), elle fait aujourd'hui largement appel à de nombreux domaines des mathématiques, comme la , les processus stochastiques, les espaces vectoriels et l'algèbre linéaire et des mathématiques appliquées, notamment la théorie de l'information, l'optimisation ou encore l'analyse numérique.
Time–frequency analysis
In signal processing, time–frequency analysis comprises those techniques that study a signal in both the time and frequency domains simultaneously, using various time–frequency representations. Rather than viewing a 1-dimensional signal (a function, real or complex-valued, whose domain is the real line) and some transform (another function whose domain is the real line, obtained from the original via some transform), time–frequency analysis studies a two-dimensional signal – a function whose domain is the two-dimensional real plane, obtained from the signal via a time–frequency transform.
Intermediate frequency
In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.
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