Novel Olfactometer Reveals Brain-Breathing Interactions During Olfactory Perception
This study introduces a novel, cost-effective olfactometer device synchronized to the respiratory cycle. Our olfactometer enables passive delivery of olfactory stimuli at specific respiratory phases during simultaneous electroencephalography (EEG) recordings, improving standardization and sensitivity. The device is more objective than bio-behavioral paradigms that are (i) prone to within-subject variation on repeated testing and (ii) dependent upon cognitive, literary, and/or motor control abilities. The device was tested on 17 healthy subjects with three odors (peppermint, oregano, grapefruit) and a no-odor control, while recording simultaneous nasal respiration and EEG. In this paper, we introduce the idea of respiratory phase-locked event-related spectral perturbations (RPL-ERSP). RPL-ERSPs in the frontal/temporal region showed that neural activity was altered halfway through the first inhalation post-odor stimulus, compared to no-odor control. Tensor decomposition underlined the separation between stimuli and classified subject-level odor identification with above-chance performance (AUC = 0.75). Overall, we propose that RPL-ERSPs are a more accurate and informative method of reporting group-level responses to olfactory stimuli, and emphasize the importance of obtaining natural respiratory responses along with neural activity.