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Sources of functional magnetic resonance imaging signal fluctuations in the human brain at rest: a 7 T study.

Abstract：

:Signal fluctuations in functional magnetic resonance imaging (fMRI) can result from a number of sources that may have a neuronal, physiologic or instrumental origin. To determine the relative contribution of these sources, we recorded physiological (respiration and cardiac) signals simultaneously with fMRI in human volunteers at rest with their eyes closed. State-of-the-art technology was used including high magnetic field (7 T), a multichannel detector array and high-resolution (3 mm(3)) echo-planar imaging. We investigated the relative contribution of thermal noise and other sources of variance to the observed fMRI signal fluctuations both in the visual cortex and in the whole brain gray matter. The following sources of variance were evaluated separately: low-frequency drifts due to scanner instability, effects correlated with respiratory and cardiac cycles, effects due to variability in the respiratory flow rate and cardiac rate, and other sources, tentatively attributed to spontaneous neuronal activity. We found that low-frequency drifts are the most significant source of fMRI signal fluctuations (3.0% signal change in the visual cortex, TE=32 ms), followed by spontaneous neuronal activity (2.9%), thermal noise (2.1%), effects due to variability in physiological rates (respiration 0.9%, heartbeat 0.9%), and correlated with physiological cycles (0.6%). We suggest the selection and use of four lagged physiological noise regressors as an effective model to explain the variance related to fluctuations in the rates of respiration volume change and cardiac pulsation. Our results also indicate that, compared to the whole brain gray matter, the visual cortex has higher sensitivity to changes in both the rate of respiration and the spontaneous resting-state activity. Under the conditions of this study, spontaneous neuronal activity is one of the major contributors to the measured fMRI signal fluctuations, increasing almost twofold relative to earlier experiments under similar conditions at 3 T.

journal_name

Magn Reson Imaging

journal_title

Magnetic resonance imaging

authors

Bianciardi M,Fukunaga M,van Gelderen P,Horovitz SG,de Zwart JA,Shmueli K,Duyn JH

doi

10.1016/j.mri.2009.02.004

subject

Has Abstract

pub_date

2009-10-01 00:00:00

pages

1019-29

issue

eissn

0730-725X

issn

1873-5894

pii

S0730-725X(09)00059-9

journal_volume

pub_type

杂志文章

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Sources of functional magnetic resonance imaging signal fluctuations in the human brain at rest: a 7 T study.