Our results differ from converging evidence of the literature in that we did not find any EEG variability correlates in the ACC. This region is thought to be involved in both top-down and bottom-up attentional control related to sensory processing (Crottaz-Herbette and Menon, 2006) and has been linked to early EEG component modulations. The N1 has been shown to correlate with ACC activity during auditory discrimination tasks using EEG-fMRI (Mulert et al., 2008) and fMRI-constrained EEG source localization (Esposito et al., 2009b). The latter technique was applied to both visual and auditory oddball data to find correlates in the early N2b and P3a components (Crottaz-Herbette and Menon, 2006). However, we did find ACC correlates of RT variability, which was not regressed out of the single-trial-variability models in these previous investigations. This finding is in accordance withWarbrick et al. (2009), who used a visual target-detection task to discover similar ACC correlates for both RT variability and P3 latency variability, but did not tease these effects apart. We demonstrate that attention-related ACC coupling with EEG components is reflected in the variability of externally-observable behavioral response events.
