title: Spontaneous physiological variability modulates dynamic functional connectivity in resting-state functional magnetic resonance imaging.
abstract: It is well known that the blood oxygen level-dependent (BOLD) signal measured by functional magnetic resonance imaging (fMRI) is influenced-in addition to neuronal activity-by fluctuations in physiological signals, including arterial CO2, respiration and heart rate/heart rate variability (HR/HRV). Even spontaneous fluctuations of the aforementioned physiological signals have been shown to influence the BOLD fMRI signal in a regionally specific manner. Related to this, estimates of functional connectivity between different brain regions, performed when the subject is at rest, may be confounded by the effects of physiological signal fluctuations. Moreover, resting functional connectivity has been shown to vary with respect to time (dynamic functional connectivity), with the sources of this variation not fully elucidated. In this context, we examine the relation between dynamic functional connectivity patterns and the time-varying properties of simultaneously recorded physiological signals (end-tidal CO2 and HR/HRV) using resting-state fMRI measurements from 12 healthy subjects. The results reveal a modulatory effect of the aforementioned physiological signals on the dynamic resting functional connectivity patterns for a number of resting-state networks (default mode network, somatosensory, visual). By using discrete wavelet decomposition, we also show that these modulation effects are more pronounced in specific frequency bands.
authors.affiliation: KIOS Research Center, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus.
authors.forename: F
authors.initials: F
authors.lastname: Nikolaou
authors.affiliation: KIOS Research Center, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus.
authors.forename: C
authors.initials: C
authors.lastname: Orphanidou
authors.affiliation: Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus.
authors.forename: P
authors.initials: P
authors.lastname: Papakyriakou
authors.affiliation: Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK.
authors.forename: K
authors.identifier: http://orcid.org/0000-0002-6516-313X
authors.initials: K
authors.lastname: Murphy
authors.affiliation: Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK.
authors.forename: R G
authors.initials: RG
authors.lastname: Wise
authors.affiliation: KIOS Research Center, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus Department of Bioengineering, McGill University, 817 Sherbrooke Ave W, MacDonald 270, Montreal, Quebec, Canada H3A 0C3 georgios.mitsis@mcgill.ca.
authors.forename: G D
authors.initials: GD
authors.lastname: Mitsis
mesh_terms: D018810:Magnetic Resonance Angiography
keywords: blood oxygen level-dependent signal; end-tidal CO2; heart rate variability; wavelets