The most common approach for the EEG–fMRI integration is based on the use of spatial constraints, where information from the location of fMRI activation is used for event-related potential (ERP) source reconstruction (Bledowski et al., 2004b; Mulert et al., 2004). An interesting method for direct ERP/fMRI fusion has been recently proposed by Calhoun et al. (2006). However, methods based on ERP analysis do not use the valuable information that can be provided by concurrent EEG and fMRI data (Debener et al., 2006; Eichele et al., 2005, 2008; Benar et al., 2007; Strobel et al., 2008). In fact, only simultaneous recordings protocols capture the temporal dynamics in both modalities, and therefore provide a unique means for the study of EEG–fMRI coupling. From this standpoint, simultaneous EEG–fMRI can be considered a promising technique for the analysis of single-trial responses to rare and frequent events during the oddball task (Benar et al., 2007).
