suggesting that an increase in hemodynamic signals is associated with a shift of electrophysiological power spectrum from low to high frequencies (i.e. a loss in low-frequency power relative to a gain in high-frequency power). As the authors admit, the model may be oversimplified. Its value to neuroimaging also remains to be demonstrated. Moreover, the validity of this model is obviously challenged by the fact that the stimulus-driven low-frequency power increase is associated with an increase in the BOLD response. For instance, visual stimuli presented with low temporal frequency (e.g. 4~5 Hz) induce a noticeable increase in the occipital EEG/MEG power at the stimulus frequency to accompany a positive increase of the BOLD fMRI signals in the primary visual cortex.
