size, represents the relative strength of the regional BOLD response, since it reflects the ratio between the measured and predicted BOLD time courses (i.e. f (r,t)/p(t)). More importantly, the model shown in Fig 4 gives the BOLD effect size a clear biophysical interpretation meaningful to EEG/MEG. That is, the BOLD effect size provides an fMRI-based estimate for the time integral of the power of the regional EEG/MEG source activity during an effective duration of the ERP/ERF. As discussed later in this review, such a biophysical implication serves as the theoretical basis for important developments in fMRI-EEG/MEG integrated neuroimaging [24].
