In the current study, HR older male and younger female subgroups exhibited significantly lower P3 amplitude during reward processing than the comparison LR subgroups. In stimulus discrimination paradigms, P3 amplitude has been theorized to reflect a capacity or set of brain resources related to mental processes (Kok, 1997, 2001), or subjective probability, stimulus meaning, and information transmission (Johnson, 1986). On the other hand, in the reward paradigms, P3 amplitude has been shown to index both valence and/or magnitude of the reward (e.g., Homberg et al., 1981; Begleiter et al., 1983; Otten et al., 1995; Yeung and Sanfey, 2004; Goldstein et al., 2006). Distinct topographic patterns and specific brain sources for different outcomes (i.e., loss and gain) have also been reported (Kamarajan et al., 2009; Kamarajan et al., 2010). This suggests that lower P3 amplitude in a monetary gambling paradigm may be due to dysfunctional reward processing at the neural level.
