title: Mapping the end-tidal CO2 response function in the resting-state BOLD fMRI signal: spatial specificity, test-retest reliability and effect of fMRI sampling rate.
abstract: The blood oxygenation level dependent (BOLD) signal measures brain function indirectly through physiological processes and hence is susceptible to global physiological changes. Specifically, fluctuations in end-tidal CO2 (PETCO2), in addition to cardiac rate variation (CRV), and respiratory volume per time (RVT) variations, have been known to confound the resting-state fMRI (rs-fMRI) signal. Previous studies addressed the resting-state fMRI response function to CRV and RVT, but no attempt has been made to directly estimate the voxel-wise response function to PETCO2. Moreover, the potential interactions among PETCO2, CRV, and RVT necessitate their simultaneous inclusion in a multi-regression model to estimate the PETCO2 response. In this study, we use such a model to estimate the voxel-wise PETCO2 response functions directly from rs-fMRI data of nine healthy subjects. We also characterized the effect of sampling rate (TR=2seconds vs. 323ms) on the temporal and spatial variability of the PETCO2 response function in addition to that of CRV and RVT. In addition, we assess the test-retest reproducibility of the response functions to PETCO2, CRV and RVT. We found that despite overlaps across their spatial patterns, PETCO2 explains a unique portion of the rs-fMRI signal variance compared to RVT and CRV. We also found the shapes of the estimated responses are very similar between long- and short-TR data, although responses estimated from short-TR data have higher reproducibility.
authors.affiliation: Rotman Research Institute at Baycrest Centre, Canada. Electronic address: agolestani@research.baycrest.org.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Golestani
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), USA.
authors.forename: Catie
authors.initials: C
authors.lastname: Chang
authors.affiliation: Rotman Research Institute at Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada.
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Kwinta
authors.affiliation: Rotman Research Institute at Baycrest Centre, Canada.
authors.forename: Yasha B
authors.initials: YB
authors.lastname: Khatamian
authors.affiliation: Rotman Research Institute at Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Jean Chen
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Carbon dioxide; Cardiac variability; Heart rate variability; Multi-slice fMRI; Multiband fMRI; Physiological noise; Respiratory volume; Resting-state fMRI