In order to define which cerebral structures are involved in the P300 generation, several methodologies have been employed, among which intracranial recordings (Halgren et al., 1998), EEG/MEG (Basile et al., 1997; Tarkka and Stokic, 1998) and fMRI (Clark et al., 2000; Kiehl et al., 2005). It has been suggested that the large number of activated areas, mainly found in frontal, temporal and parietal cortices, might belong to different functional systems that are simultaneously active during target detection (Bledowski et al., 2004a; Horn et al., 2003). In the perspective of gaining further information about the dynamics of these systems, the fusion of EEG and fMRI has been recently suggested, because it might in principle allow to combine the high spatial and temporal resolution of fMRI and EEG respectively (Mulert et al., 2004; Calhoun et al., 2006; Eichele et al., 2008).
