Resting-state Functional Connectivity During Controlled Respiratory Cycles Using Functional Magnetic Resonance Imaging.

Introduction:This study aimed to assess the effect of controlled mouth breathing during the resting state using functional magnetic resonance imaging (fMRI).Methods:Eleven subjects participated in this experiment in which the controlled "Nose" and "Mouth" breathings of 6 s respiratory cycle were performed with a visual cue at 3T MRI. Voxel-wise seed-to-voxel maps and whole-brain region of interest (ROI)-to-ROI connectome maps were analyzed in both "Nose>Mouth" and "Mouth>Nose" contrasts.Results:As a result, there were more connection pairs in the "Mouth" breathing condition, i.e., 14 seeds and 14 connecting pairs in the "Mouth>Nose" contrast, compared to 7 seeds and 4 connecting pairs in the "Nose>Mouth" contrast (false discovery rate [FDR] of P<0.05).Conclusion:The present study demonstrated that mouth breathing with controlled respiratory cycles could significantly induce alterations in functional connectivity in the resting-state network, suggesting that it can differently affect resting brain function; in particular, the brain can hardly rest during mouth breathing, as opposed to conventional nasal breathing.