In the group comparison of N2 peak amplitudes, control subjects were found to have larger N2 peak amplitudes than alcoholics for both task conditions. For the Go N2, this difference was statistically significant at the frontal and central regions, whereas for the NoGo N2, it was significant at the frontal, central, parietal, and right-temporal regions (Table 5). However, in the sLORETA findings it was observed that although controls showed larger current densities at the source compared to alcoholics on both Go and NoGo trials in the N2 time-range, this difference was statistically significant only for the NoGo trials in the bilateral anterior prefrontal regions, with a maximum difference at the Brodmann area 10 of the left hemisphere (Table 6, Figures 6a, b). Therefore, these findings suggest that in general, alcoholics show reduced N2 amplitudes and current density at the source compared to control subjects, and this reduction is more pronounced for NoGo N2 amplitudes and current density in the anterior prefrontal cortical regions that are suggested to be involved in “cognitive branching” (see for a review Koechlin and Hyafil, 2007) or act as a “supervisory attentional gateways” (SAG; Burgess et al., 2007b; see for a review Burgess et al., 2007a).
