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Cerebral autoregulation evidence by synchronized low frequency oscillations in blood pressure and resing-state fMRI

Whittaker, Joseph, Driver, Ian, Venzi, Marcello, Bright, Molly and Murphy, Kevin 2019. Cerebral autoregulation evidence by synchronized low frequency oscillations in blood pressure and resing-state fMRI. Frontiers in Neuroscience 13 , 433. 10.3389/fnins.2019.00433

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Abstract

Resting-state functional magnetic resonance imaging (rs-fMRI) is a widely used technique for mapping the brain’s functional architecture, so delineating the main sources of variance comprising the signal is crucial. Low frequency oscillations (LFO) that are not of neural origin, but which are driven by mechanisms related to cerebral autoregulation (CA), are present in the blood-oxygenation-level-dependent (BOLD) signal within the rs-fMRI frequency band. In this study we use a MR compatible device (Caretaker, Biopac) to obtain a non-invasive estimate of beat-to-beat mean arterial pressure (MAP) fluctuations concurrently with rs-fMRI at 3T. Healthy adult subjects (n=9; 5 male) completed two 20-minute rs-fMRI scans. MAP fluctuations were decomposed into different frequency scales using a discrete wavelet transform, and oscillations at approximately 0.1Hz show a high degree of spatially structured correlations with matched frequency fMRI fluctuations. On average across subjects, MAP fluctuations at this scale of the wavelet decomposition explain ~ 2.2% of matched frequency fMRI signal variance. Additionally, a simultaneous multi-slice multi-echo acquisition was used to collect 10-minute rs-fMRI at three echo times at 7T in a separate group of healthy adults (n=5; 5 male). Multiple echo times were used to estimate the R2* decay at every time point, and MAP was shown to strongly correlate with this signal, which suggests a purely BOLD (i.e. blood flow related) origin. This study demonstrates that there is a significant component of the BOLD signal that has a systemic physiological origin, and highlights the fact that not all localized BOLD signal changes necessarily reflect blood flow supporting local neural activity. Instead, these data show that a proportion of BOLD signal fluctuations in rs-fMRI are due to localized control of blood flow that is independent of local neural activity, most likely reflecting more general systemic autoregulatory processes. Thus, fMRI is a promising tool for studying flow changes associated with cerebral autoregulation with high spatial resolution.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff University Brain Research Imaging Centre (CUBRIC)
Medicine
Physics and Astronomy
Psychology
Subjects: Q Science > QC Physics
Q Science > QP Physiology
Publisher: Frontiers Media
ISSN: 1662-4548
Funders: Wellcome Trust
Date of First Compliant Deposit: 16 April 2019
Date of Acceptance: 15 April 2019
Last Modified: 11 Jun 2019 09:43
URI: http://orca.cf.ac.uk/id/eprint/121773

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