Fig. 2.

Representative example of resting state signals and the effect of physiological noise on resting-state functional connectivity (a) Configuration of the optode montage with 10 sources (red dots), eight detectors (blue dots) and 16 long distance channels (solid gray lines). A representative homologous channel pair (marked in black and green) and a control channel pair (marked in black and pink) are shown in the montage. (b) Sample time traces of resting-state HbO concentration changes of subject #3. The time series signals are color-coded with the channel colors of Fig. 2(a). (c) The power spectrum of the three signals depicting the presence of systemic physiological noise in fNIRS signals such as Mayer waves ($\sim 0.1\mathrm{Hz}$), respiration (0.2 to 0.3 Hz) and heartbeat ($\sim 1\mathrm{Hz}$). The partial overlap between the Mayer wave frequencies (M-band: 0.05 to 0.15 Hz) and the frequency band of interest for resting-state functional connectivity (RSFC-band: 0.009 to 0.1 Hz) is also highlighted.