In a previous study of theta EROs during loss and gain in the same monetary gambling task, we reported topographic differences between the younger (12–15) and older (16–25) subsamples of the COGA prospective study in the same baseline condition (Kamarajan et al., 2015a). In that study, we found that the younger subsample (12–15) showed more theta power and less frontalization, particularly for the loss condition, than the older subsample (16–25) (see Figs. 3 and 4 in Kamarajan et al., 2015a). Although the age range in the current study is not ‘ideal’ to examine these developmental changes in brain oscillations, when the topographic maps of late adolescents (17–18 years) and young adults (19–25 years were compared (see Fig. A2 in Appendix), it was found that overall, the adolescent group showed more theta power and more diffuse posterior topography than the adult group, regardless of genotype. Furthermore, the subgroups with minor allele(s) (AG and GG) showed a more diffuse topography with less frontalization than those with the AA genotype, perhaps suggesting a delay in brain maturation. Electrophysiological (Matousek and Petersen, 1973; Gasser
