Autonomic Nervous Response to γ-Undecalactone Odor and its Relation to Subjective Evaluation

Odor is difficult t o v erbalize and its sensation varies widely between individuals. Therefore, several attempts have been made to evaluate the subjective perception of odor objectively and quantitatively via autonomic activity. This study focuses on peripheral arterial stiffness, which is innervated by the vasoconstriction of skin sympathetic nerves, and aims to evaluate its relationship with the subjective evaluation of pleasant odor. Accordingly, an experiment was conducted to measure the physiological signals and subjective evaluation of odor by presenting participants with odorless air, and low and high concentrations of $\gamma -$Undecalactone $(N \quad =10)$. Their cardiac autonomic responses were evaluated using the mean low to high-frequency ratio of heart rate (HR) variability and heart rate. In addition, skin sympathetic responses were evaluated using the mean of the peripheral arterial stiffness $\beta$ of the earlobe and fingertip. Analysis using a mixed linear model demonstrated a significant fixed effect via a positive slope $(p \lt 0. 01)$ fo r HR, earlobe arterial stiffness, and fingertip arterial stiffness relative to the first principal component of subjective evaluation, thereby interpreted as a pleasant and high-arousal state. The findings of this study suggest that HR, earlobe arterial stiffness, and fingertip arterial stiffness can be predictors for the subjective evaluation of $\gamma -$Undecalactone odor.