Objective – At a time when the search for well-being has become a societal priority, understanding how to induce positive emotions through non-pharmacological approaches is more than welcome. Odors and music are commonly used to achieve such a goal. However, while odors have a direct access to the limbic system through the olfactory system, auditory inputs are previously processed by a thalamic relay. Moreover, odors are intimately linked to respiratory activity through olfactomotor efforts. What is the impact of such a difference on the ability of odors or music to induce a relaxation state? We hypothesized that, through the privileged access of odors to the limbic system and its impact on respiration regime, positive odors have a peculiar ability to induce a relaxation state.

Methods – 30 healthy human participants were instructed to choose the most personally pleasant (positive) odor and music among a panel of 10 samples. Then, each participant was exposed to her/his most pleasant odor, music, or no stimulus (baseline), for a duration of 10 minutes. To get objective relaxation data, brain activity was recorded by EEG (32 active electrodes), breathing was captured through a nasal cannula and a ventral belt, and heart rate variability (HRV) was extracted from ECG recording. Subjective relaxation was assessed through questionnaires.

Results – Positive odor decreased respiratory rate and increased HRV, while positive music increased respiratory rate and decreased HRV. Both odors and music were similarly able to raise brain activity related to relaxation (theta or alpha power). Data concerning subjective relaxation feelings are currently processed.

Conclusion – Preliminary results suggested a similar ability of positive odor and music to induce neuronal relaxation state while being associated with opposite physiological signatures.

Funding – Roudnitska Foundation, ANR. Odors provided by Sevessence©.