Our EEG variability results also differ from the many EEG-fMRI reports of P3-variability correlates in the insula (Bledowski et al., 2004a, 2004b; Eichele et al., 2005; Warbrick et al., 2009). However, we did find bilateral insula correlates of the average event-related response, and additional RT-variability correlates (max z-score 3.78 in right insula and 3.38 in left insula) that were slightly too small to pass cluster threshold. Using a visual target-detection task,Warbrick et al. (2009) also found bilateral insula correlates with a traditional analysis, and conversely with P3 amplitude variability but not RT variability. Together with their findings, our results suggest that variance of the BOLD signal within the insula can be explained primarily via the average event-related response, with only minor contributions observable in EEG-component and RT variability.
