The average power spectrum of each channel on PFC area was used to analyze the significantly different channel between male and female groups through the following steps of Figs. 2(a)-2(d). In the Fig. 2(b), the power spectrum of the low-frequency (0.01 to 0.08 Hz) of ΔHbO2, ΔHb, and ΔtHb were obtained from time series signal by using FFT method. Then the spectrogram (Fig. 2(c)) of ΔtHb of each channel was structured from power spectrum curve to determine the significantly different channel (Fig. 2(d)) between male and female groups by using two-sample t-test with p value < 0.001.
