Pleasant odors specifically promote a soothing autonomic response and brain-body coupling through respiratory...

Neuronal oscillations are tightly linked to physiological rhythms, yet little is known about how sensory stimuli influence their coupling. Here, we investigated whether pleasant odors and pleasant music modulate the coupling between respiration, autonomic activity, and brain oscillations. Using a within-subject design, we exposed participants to a personally pleasant odor and a personally pleasant music while recording respiratory and cardiac activity, feeling of relaxation, and respiration-locked EEG responses. Our results reveal that only odors induced a significant coupling between physiological and neural rhythms. Pleasant odors decreased respiratory rate, increased inspiratory volume, reduced heart rate, and enhanced heart rate variability (HRV). EEG analyses showed that this odor-induced respiratory slowing enhanced respiration-related brain activity in a temporo-parieto-central network, which is not observed with music. In contrast, music, regardless of tempo, increased subjective arousal without affecting autonomic or neural coupling. These findings suggest that pleasant odors engage an olfactomotor response, where an emotionally driven change in breathing rhythm enhances respiration-related neural oscillations. This mechanism may facilitate brain states associated with an increased feeling of relaxation and interoception, distinguishing odors as a unique sensory modality capable of promoting brain-body coupling. Our study highlights the potential of olfactory stimulation as a non-invasive tool for modulating brain rhythms and autonomic function.