TABLE 2.

Summary of peak coherent frequencies between PPG‐derived signals and fMRI signals

All values in Hz	PPG	HRV	SDPPG	PIR
Lateral ventricles	0.70 ± 0.07	0.14 ± 0.02	0.85 ± 0.06	0.02 ± 0.002
3rd ventricle	1.02 ± 0.03	0.20 ± 0.02	1.06 ± 0.03	0.03 ± 0.005
Gray matter	0.28 ± 0.08	0.09 ± 0.02	0.50 ± 0.07	0.02 ± 0.002
White matter	0.15 ± 0.08	0.09 ± 0.01	0.44 ± 0.07	0.03 ± 0.003
Arteries	1.00 ± 0.05	0.16 ± 0.03	1.00 ± 0.04	0.02 ± 0.002
Veins	0.57 ± 0.11	0.06 ± 0.01	0.78 ± 0.09	0.02 ± 0.002
Aqueduct	0.19 ± 0.03	0.25 ± 0.03	0.87 ± 0.07	0.02 ± 0.002

Note: The frequency range of interest is 0.008–1 Hz. These frequencies are derived from the weighted average of the ridge frequencies extracted from the cross‐spectrograms.