Reply to Spreng et al.: Multiecho fMRI denoising does not remove global motion-associated respiratory signals

In 2 human functional magnetic resonance imaging (fMRI) datasets (89 “ME” subjects; 12 “NA” subjects), we used signal decay properties to separate 2 kinds of signals: S0 artifacts, which were spatially specific, and T2* modulations, which occurred over the whole brain (1). We established that whole-brain (global) fMRI signals were nearly unchanged before and after removal of S0 signals. Hence, most global signals are T2* signals, compatible with...