Specifically, it is clear that the group difference in ERP response to feedback is confined to the delta-P300 component, with no significant difference evident for the theta-FRN component. Notably, both low and high externalizing groups show robust amplification of theta oscillatory activity following loss feedback relative to gain feedback. In fact, the groups are so similar in this component of responding that corresponding waveforms for gain and loss trials nearly overlap (Figure 3, left filtered line plot). In contrast, the delta-P300 waveforms for low and high externalizing groups clearly diverge (see Figure 3, right filtered line plot). The statistical topographical maps depicting correlations between continuous Externalizing (ESI-100) scores and theta and delta TF component scores at varying scalp sites (Figure 3, bottom section) corroborate this visual impression—significant effects are observed broadly for delta-P300, but not at all for theta-FRN. Specifically, higher externalizing proneness is associated with reduced delta-P300 response to both gain and loss feedback. Evidence of a significant Externalizing × Gain/Loss trial interaction was found (i.e., significant correlations between ESI-100 scores and gain-minus-loss difference scores were evident at some scalp sites), reflecting somewhat lesser modulation of delta-P300 response following gain feedback as compared to loss feedback among individuals higher
