title: Cardiorespiratory effects on default-mode network activity as measured with fMRI.
abstract: The default-mode network (DMN) consists of areas showing more activation during rest than during a task. Several authors propose some form of cognitive processing to underlie BOLD signal changes in the DMN as activity within the network is modulated by the level of effort required by the task and is positively correlated with self-referential processing. Alternatively, BOLD signal changes within the DMN may be caused by cardiorespiratory processes (CR) affecting BOLD signal measurements independent of neuronal activity. The goal of this study is to investigate whether BOLD signal changes within the DMN can be explained by CR effects. To this aim, brain activity, heartbeat, and respiration are measured during resting-state and while subjects perform a cognitive task with a high- and low-demand condition. To correct for CR effects we used RETROICOR (Glover et al., [2000]: Magn Reson Med 44:162-167) in combination with additive linear modeling of changes due to respiration volume, heart rate and heart rate variability. CR effects were present within the frequency-range of the DMN and were located in areas of the DMN, but equally so in other areas. After removal of CR effects, deactivation and resting-state connectivity between the areas of the DMN remained significant. In addition, DMN deactivation was still modulated by task demand. The same CR correction method did remove activation in task-related areas. We take these results to indicate that the BOLD signal within the DMN cannot be explained by CR effects alone and is possibly related to some form of cognitive neuronal processing.
authors.affiliation: Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, Utrecht, The Netherlands. m.vanbuuren-2@umcutrecht.nl
authors.forename: Mariët
authors.initials: M
authors.lastname: van Buuren
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Gladwin
authors.forename: Bram B
authors.initials: BB
authors.lastname: Zandbelt
authors.forename: Martijn
authors.initials: M
authors.lastname: van den Heuvel
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
authors.forename: René S
authors.initials: RS
authors.lastname: Kahn
authors.forename: Matthijs
authors.initials: M
authors.lastname: Vink
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D003071:Cognition / Q000502:physiology; D003198:Computer Simulation; D005071:Evoked Potentials / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000033:anatomy & histology / Q000502:physiology*; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult