Neurophysiological Responses to Inhalation of Osmanthus fragrans Volatiles: A Combined Electronic Nose and Electroencephalogram (EEG) Study on Concentration-Dependent Effects

Fragrant olive (Osmanthus fragrans var. aurantiacus (O. fragrans)) extract is known to influence neurophysiological responses through inhalation, yet research on concentration-dependent effects and sex-specific variations remains insufficient. This study utilized an electronic nose (E-nose), electroencephalography (EEG), and standardized low-resolution electromagnetic tomography (sLORETA) to characterize the volatile profiles and neurophysiological impacts of O. fragrans at 3% and 5% concentrations. E-nose analysis identified 48 volatile compounds, with chemometric modeling (PCA, HCA) showing clear discrimination between concentrations. EEG results demonstrated that inhalation induced significant concentration-dependent changes—specifically increasing sedation-related alpha waves and decreasing tension-related gamma waves—with 5% O. fragrans eliciting more widespread cortical responses than the 3% concentration. Notably, no significant sex-related differences were observed in general EEG patterns; however, sLORETA revealed that 5% inhalation specifically suppressed high beta and gamma activities in male participants within Brodmann areas 13, 21, 22, and 44, regions associated with emotional and multisensory processing. In conclusion, this study successfully quantified the relationship between volatile profiles and human brain responses using an integrated biomimetic and neurophysiological approach. These findings provide objective evidence that O. fragrans inhalation, particularly at 5%, modulates neural oscillations toward a relaxed state, offering valuable data for olfactory perception and potential applications as functional volatile compounds.