Frequency- and Distance-Dependent Relation Between Event-Related EEG Activity and BOLD Responses in an Auditory Stroop Paradigm

The exact relationship between electroencephalogram (EEG) and blood oxygenation level-dependent (BOLD) responses in functional magnetic resonance imaging (fMRI) recordings is still an open question, in particular for event-related cognitive paradigms. Here, we investigated how the relationship between event-related power changes in the EEG (ERPC) and BOLD responses varies for the typical EEG frequency bands and depending on the distance between the fMRI voxel and the EEG recording site. As cognitive task we chose an auditory Stroop experiment. We observed that for small distances event-related BOLD responses were positively correlated with ERPC in the gamma band, just as, in contrast to previous studies, in the alpha band. BOLD responses were negatively correlated with EEG power in the delta range for regions close to the EEG recording site.