Effects of mouth breathing on hippocampal activity examined by 3T fMRI

We investigated the effects of mouth breathing and typical nasal breathing on brain function, using blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI).
The study consisted of two parts: the first test was a simple contrast between mouth and nasal breathing and the second test involved combined breathing modes, e.g., mouth inspiration and nasal expiration. Eleven healthy participants performed the combined breathing task while undergoing 3T fMRI. In the group-level analysis, contrast images from the nasal or mouth breathing acquired by the participant-level analyses were analyzed using a one-sample t-test. We also performed a region-of-interest analysis comparing signal intensity changes between the breathing modes; the regions were selected using an automated anatomical labeling map. The results demonstrated that BOLD signal in the hippocampus and brainstem decreased significantly during mouth breathing, whereas the signal increased in the central gyrus. Given that the hippocampus participates in cognitive functions such as memory, decreased hippocampal activity may explain the adverse effects of mouth breathing on brain function. 
In this dataset: High resolution T1 weighted structural and BOLD contrast fMRI scans.