Fig. 3.

(A) Multiplicative scaling of noise. The variance estimate for subsets of voxels with increasing voxel-specific variances, separately calculated on images with high noise (black dashed line) and low noise (gray line). (B) Spatial distribution of the noise process. Correlation coefficient of the time series of the squared residuals $(r_{n,1}^2,\dots ,r_{n,T}^2)$ with the time series of the overall estimated variance scaling parameters $({\widehat{s}}_1,\dots ,{\widehat{s}}_T)$.