Reduced posterior mesofrontal cortex activation by risky rewards in substance-dependent patients

Substance-dependent individuals show disadvantageous decision-making, as well as alterated frontocortical recruitment when performing experimental tasks. We investigated whether substance-dependent patients (SDP) would show blunted recruitment of posterior mesofrontal cortex (PMC) by a conflict between concurrently increasing reward and risk of penalty in a monetary game of "chicken." SDP and controls performed: motor control (no reward) trials, guaranteed reward trials in which reward was not at risk, and risky trials where subjects were required to terminate their reward accrual before a secret varying time limit or else "bust" and forfeit that trial's winnings (low penalty) or the current trial's winnings plus an equal amount of previous winnings (high penalty). Reward accrual duration at risk of "busting" correlated negatively with trait neuroticism. The contrast between winning guaranteed reward versus non-reward activated the caudate head bilaterally in SDP but not controls. Accumulation of money at risk of low- or high-penalty (contrasted with accumulating guaranteed money) activated the PMC in both groups, but with a greater magnitude and more anterior extent in controls. Pre-decision signal increase in a PMC volume of interest negatively correlated with risk-taking in low-penalty trials, and was blunted in SDP relative to controls under both penalty conditions after controlling for individual differences in actual risk-taking and the higher neuroticism of SDP. These data suggest that SDP are characterized by a combination of: (a) striatal hypersensitivity to reward, and (b) under-recruitment of the specialized conflict-monitoring circuitry of the PMC when reward entails potential penalties.