participant. This process is employed in previous studies of fNIRS field [21, 23]. The band-passed optical signal analysis avoids the physiological noise of low and high frequency such as respiratory (0.1-0.3 Hz) and cardiac-related fluctuations (0.75-1 Hz) in oxygen supply [2–6]. In our study, the optical signal of each fOT channel was filtered through a band-pass filter within 0.01 to 0.08 Hz to reduce the effects of physiological noise [2, 6, 24]. The butterworth low pass filter (cutoff frequency is 0.08 Hz) and butterworth high pass filter (cutoff frequency is 0.01 Hz) were used for band-pass filtering with MATLAB after raw data of ΔHbO2 and ΔHb were obtained from the system. Then the average data was obtained for group-level analysis to reduce the effects of individual differences. The distribution of the filtered signals of the time series and spectrum data are demonstrated in Fig. 2(b) and 2(e), respectively. In the Fig. 2(b), the power spectrum of a filtered signal shows that the physiological-noise (include respiratory and cardiac frequencies) are completely filtered. These remaining signals after filtering are used to perform subsequent data analysis. Three different analyses of gender-specific effects of hemispheric asymmetry in PFC were performed with processed fOT data
