Consistent with the data described above is the fact that numerous neuroimaging studies have found abnormal OFC function associated with substance abuse (Boettiger et al., 2007; Dom et al., 2005; Ersche et al., 2005; London et al., 2000; Volkow and Fowler, 2000). The OFC is thought to moderate impulsive choice (Mobini et al., 2002; Rudebeck et al., 2006), and to represent subjective value during decision-making (Izquierdo et al., 2004; Padoa-Schioppa and Assad, 2006; Roesch and Olson, 2004; Schoenbaum and Roesch, 2005). Alcoholics have decreased densities of neurons and glia in OFC (Miguel-Hidalgo et al., 2006) and ethanol drinking in rats alters glia in frontal prelimbic cortex (Miguel-Hidalgo, 2006). Recently, we have found that reduced OFC activity during decision-making among abstinent alcoholics is correlated with their tendency to choose immediate over delayed rewards (Boettiger et al., 2007), indicating a dysfunction of the OFC that may contribute to the persistence of addictive disorders. The dysfunction in delayed discounting reward tests involves learning initial rewards and continually assessing outcomes to improve results. This requires a form of relearning that initial learned rewards can
