ERP differences with vs. without concurrent fMRI.

The acquisition of ERPs concurrently with fMRI in cognitive paradigms is appealing, but technically challenging. Little is known about the effects of the fMRI environment on the time-course and topography of previously documented ERP effects. We examined the replicability of ERP differences in the scanner at the level of individual subjects, using two cognitive paradigms and two statistical procedures. ERP P3 differences found outside the scanner in both paradigms were also robustly detected in the ERPs acquired during fMRI scanning. These P3 effects had equivalent time-courses and scalp topographies inside and outside the scanner. This replication at the level of individual data-sets has implications for the clinical applicability of ERP-fMRI and, more generally, for the quality of scanner recorded ERPs.