Simultaneous recording is challenging but necessary in fMRI-EEG integrated neuroimaging and neuroscience research. Advances, mainly in signal processing techniques, have allowed us to remove various MR-related artifacts from the EEG data recorded during concurrent fMRI scans. Future development of hardware and software will no doubt further improve the quality of EEG and fMRI from simultaneous recordings. Although the simultaneous fMRI-EEG recording is desirable for a variety of purposes, it is not always necessary when studying some passive sensory evoked responses. In this regard, one has to base his/her own choice on the reproducibility of the task (or stimulus) of interest vs. the possible risk of dealing with largely contaminated EEG data if recorded simultaneously with fMRI. Regardless of the theoretical efficacy of artifact reduction algorithms, the outcome of these algorithms is after all partly artificial and inevitably “worse” than artifact-free signals. For some simple paradigms only involving passive stimulus-evoked responses, it might not always be worthwhile to obtain these simultaneously-collected signals and, rather, ensure clear signals by conducting separate but highly reproducible experiments.
