TABLE 2.

Summary of the most common rs-fMRI CVR methodologies based on BOLD signal variation metrics.

		Metric	Computation
Signal Variation	Whole spectrum	RSFA	σEPI
		CV	$\frac{{\mathrm{\sigma }}_{EPI}}{{\mathrm{\mu }}_{EPI}}$
		PF	$\frac{\sqrt{{\mathrm{\sigma }}_{EPI}^2-{\mathrm{\sigma }}_{thermal}^2}}{{\mathrm{\mu }}_{EPI}}$
	Low frequency	ALFF	$\frac{{\sum }_{k:f_k[f_{min};f_{max}]}\sqrt{\frac{{\left|FFT\right|}_{f_k}^2}{N}}}{n_k}$
		fALFF	$\frac{\text{ALFF}}{\begin{array}{c}\hfill \frac{{\sum }_{\text{m}:f_m[0_{};f_{max}]}\sqrt{\frac{{\left|FFT\right|}_{f_m}^2}{N}}}{n_m}\hfill \end{array}}$

σ, temporal standard deviation; μ, temporal mean; ${\mathrm{\sigma }}_{\mathit{thermal}}^2$, temporal variance due to thermal noise; FFT, Fast Fourier transform; f, frequency range; k, number of bins within a specific frequency range; m, number of bins of the entire frequency range; f_min, minimum frequency; f_max, maximum frequency; N, number of time points; n, number of frequency bins.