# Using the \(\beta\)/\(\alpha\) Ratio to Enhance Odor-Induced EEG Emotion Recognition
## 3 Results
### EEG Spectral Analysis
#### 3.3.2 Analysis of Spectrograms  
For the \(\alpha\)1 and \(\alpha\)2 frequency bands, different ROIs exhibited similar patterns (Figure 3H,I), which supports the presence of a spatial ambiguity effect [39] in EEG signals. This effect occurs because voltage fluctuations measured at any electrode on the scalp result from the combined activity of multiple sources across different locations. Figure 3: Comparison of topographic maps and spectrum maps under different conditions. (**A–C**) Topographic comparison of the average power spectral density (PSD) between the three groups of subjects in the resting state (RS), those who inhaled sandalwood essential oil (SEO), and those who inhaled bergamot essential oil (BEO), where PSD increases from blue to red. (**D,E**) RS was compared with inhaled SEO or BEO, respectively. The average PSD between the two groups of subjects was subjected to a one-tailed paired _t_-test to obtain a topographic map of the _p_-value, with a significance level of 0.05. For (**D**), \(p\) < 0.05 indicates that the average PSD of RS is significantly smaller than that of the SEO group (\(\alpha\)1, \(\alpha\)2), and \(p\) < 0.05 indicates that the average PSD of RS is significantly larger than that of the SEO group (\(\beta\)/\(\alpha\) ratio). For (**E**), the mean PSD of RS was significantly smaller than that of the BEO group (_p_ < 0.05). (**F,G**) Topographic maps of the _t_-value based on the statistical test method used for (**D,E**). When t < 0, the topographic map color is red; the darker the color, the greater the difference, and vice versa. For **F**, the average PSD of RS is smaller than that of the SEO group (\(\alpha\)1, \(\alpha\)2) when \(t\) < 0, and the average PSD of RS is significantly larger than that of the SEO group (\(\beta\)/\(\alpha\) ratio) when \(t\) < 0. For (**G**), the mean PSD of RS is smaller than that of the BEO group when \(t\) < 0. See Supplementary Tables S2 and S3 for specific _p_-values and _t_-values. (**H,I**) RS, SEO, and BEO are represented by three different colored lines, indicating intersubject \(\alpha\)1 and \(\alpha\)2 average PSD in different regions of interest (ROIs) under different conditions. The F-ROI, T-ROI, C-ROI, P-ROI, and O-ROI correspond to the frontal lobe area, temporal lobe area, central area, parietal lobe area, and occipital lobe area, respectively. The shaded areas of different colors represent the standard error (SE) of the mean PSD between subjects in different groups. A one-tailed paired _t_-test was performed on the average PSD between subjects in different ROIs for each frequency band of RS and SEO (marked in orange font) or BEO (marked in red font), with a significance level of 0.05. It is noteworthy that when \(p\) < 0.05, the font is bolded. * \(p\) < 0.05, **_p_ < 0.01. See Supplementary Tables S4 and S5 for specific _t_-values. The spectrogram results show that, compared to the RS group, inhalation of either SEO or BEO led to varying degrees of increase in the PSD of \(\alpha\)1 and \(\alpha\)2 across all ROIs. (Figure 3H,I). Specifically, for the alpha1 rhythm (Figure 3H), inhalation of SEO resulted in a significant PSD rise in all ROIs (F-ROI: \(t=-2.192\), \(p=0.017\); T-ROI: \(t=-1.916\), \(p=0.031\); C-ROI: \(t=-2.436\), \(p=0.009\); P-ROI: \(t=-1.820\), \(p=0.038\); O-ROI: \(t=-1.766\), \(p=0.042\)), whereas inhalation of BEO led to a significant increase solely in the F-ROI (F-ROI: \(t=-1.700\), \(p=0.048\); T-ROI: \(t=-1.482\), \(p=0.072\); C-ROI: \(t=-1.593\), \(p=0.059\); P-ROI: \(t=-1.385\), \(p=0.086\); O-ROI: \(t=-0.502\), \(p=0.309\)).