The spectrum analysis was performed to evaluate the significantly different channels between male and female groups. Figure 8 shows the spectrogram of each channel from male (Fig. 8(a)) and female (Fig. 8(b)) groups. Overall, we can observe that the intensity of power spectrum of PFC region (such as Ch. 3 to 8; Ch. 13 to 19; Ch. 23 to 30; Ch. 34 to 40 and Ch. 45 to 50) in female group is greater than male group. The PFC regions of 0.01 to 0.08 Hz were intercepted on the bottom of Fig. 8. In this processing, the values of other regions outside the PFC were filled in value of 0 to highlight the PFC regions. In the detail, the intensity of power spectrum of PFC region in male group is greater than female group around 0.023 Hz. Conversely, the intensity of PFC region in female group is greater than male group around 0.03 Hz. Additionally, the distribution of spectrogram is obvious differences between male and female groups.
