I am trying to get my head around what questions I can expect to have answered about brain activity that cannot be answered by doing two separate EEG and fMRI experiments.
I am aware that fMRI records the BOLD signal and EEG records a collective electrical response from pyramidal neurons; so even if the first one provides good spatial resolution across the whole brain and the second one provides good time resolution for the exposed parts of the cortex (gyri), the two recording methods do not seem to be very complementary/symmetrical, in other words they do not measure the same quantities/qualities of the brain activity.
I am unsure to what is the actual benefit of using them in combination in an experiment although I acknowledge that combined EEG-fMRI can perhaps address certain questions in a within-subject analysis but this is still a bit vague.
I found this paper by Huster et al. (2012) helpful but if anyone has more suggestions/directions, that would be much more than welcome.
Huster, R. J., Debener, S., Eichele, T., & Herrmann, C. S. (2012). Methods for simultaneous EEG-fMRI: an introductory review. Journal of Neuroscience, 32(18), 6053-6060.