Emotion recognition using an odor-induced electroencephalogram (EEG) has broad applications in human-computer interaction. However, existing studies often rely on subjective self-reporting to label emotion, lacking objective verification. While the β/α ratio has been identified as a potential objective indicator of arousal in EEG spectral analysis, its value in emotion recognition remains underexplored. This study ensured the authenticity of emotions through self-reporting and EEG spectral analysis of 50 adults after inhaling sandalwood essential oil (SEO) or bergamot essential oil (BEO). Classification models were built using discriminant analysis (DA), support vector machine (SVM), and random forest (RF) algorithms to identify low or high arousal emotions. Notably, this study introduced the β/α ratio as a novel frequency domain feature to enhance model performance for the first time. Both self-reporting and EEG spectral analysis indicated that SEO promotes relaxation, whereas BEO enhances attentiveness. In model testing, incorporating the β/α ratio enhanced the performance of all models, with the accuracy of DA, SVM, and RF increasing from 70%, 75%, and 85% to 75%, 80%, and 95%, respectively. This study validated the authenticity of emotions by employing a combination of subjective and objective methods and highlighted the importance of β/α in emotion recognition along the arousal dimension.

Alzheimer’s disease (AD) is a neurodegenerative disorder that is projected by the WHO to affect over 100 million people by 2050. Clinically, AD patients undergoing long-term antipsychotic treatment often experience severe anxiety or depression in later stages. Furthermore, early-stage AD manifests with weakened α waves in the brain, progressing to diminished α and β waves in late-stage disease, reflecting changes in emotional states and disease progression. In this study, EEG signal analysis revealed that inhalation of Dalbergia pinnata (Lour.) Prain essential oil (DPEO) enhanced δ, θ, α and β wave powers in the frontal and parietal lobes, with a rising trend in the β/α ratio in the temporal lobe. These findings suggest an alleviation of anxiety and an enhancement of cognitive functions. Treatment of the AD SH-SY5Y (human neuroblastoma cells) cell model with DPEO resulted in decreased intracellular levels of Aβ, GSK-3β, P-Tau, IL-1β, TNF-α, IL-6, COX-2, OFR, and HFR, alongside reduced AchE and BchE activities and increased SOD activity. Network pharmacology analysis indicated a potential pharmacological mechanism involving the JAK-STAT pathway. Our study provides evidence supporting DPEO’s role in modulating anxiety and slowing AD pathological progression.