Spatiotemporal Dynamics of fMRI Signal Changes Induced by High Concentration Normobaric Oxygen Inhalation

While it is well known that oxygen supports the brain’s metabolic demands, it remains unclear how increased oxygen concentration influences intrinsic neural activity over time and across brain regions. Using resting-state functional magnetic resonance imaging (fMRI), we examined the dynamic responses to high-concentration normobaric oxygen across distinct phases of exposure and withdrawal. We revealed three patterns in the BOLD signals: increased activation during inhalation, an undershoot following immediate oxygen withdrawal, and reactivation even without continued oxygen. These responses were most pronounced in the default mode network (DMN), but also exhibited spatiotemporally heterogeneous patterns across the brain, a map we term Brain Oxygen Sensitivity Topography (BOST). Functional connectivity analyses further revealed increased between-network connectivity during inhalation and enhanced within-network connectivity in the DMN during the aftereffect. This spatiotemporal heterogeneity and transient network reorganization suggests that distinct physiological processes are engaged at each phase, enabling us to predict how different oxygen protocols will enhance specific cognitive functions.