Developmental Differences in Posterior Mesofrontal Cortex Recruitment by Risky Rewards

Abstract

Might increased risk taking in adolescence result in part from underdeveloped conflict-monitoring circuitry in the posterior mesofrontal cortex (PMC)? Adults and adolescents underwent functional magnetic resonance imaging during a monetary game of "chicken." As subjects watched ostensible winnings increase over time, they decided when to press a button to bank their winnings, knowing that if they did not stop pursuing money reward before a secret varying time limit, they would "bust" and either lose the money accrued on the current trial (low-penalty trials) or forfeit trial winnings plus a portion of previous winnings (high-penalty trials). Reward accrual at risk of low penalty (contrasted with guaranteed reward) activated the PMC in adults but not in adolescents. Across all subjects, this activation (1) correlated positively with age but negatively with risk exposure and (2) was greater when subjects busted on the previous low-penalty trial. Reward accrual at risk of high penalty was terminated sooner and recruited the PMC in both adults and adolescents when contrasted with guaranteed reward. Predecision PMC activation in the high-penalty trials was significantly reduced in trials when subjects busted. These data suggest that (1) under threat of an explicit severe penalty, recruitment of the PMC is similar in adolescents and adults and correlates with error avoidance, and (2) when potential penalties for a rewarding behavior are mild enough to encourage some risk taking, predecision PMC activation by a reward/risk conflict is sensitive to previous error outcomes, predictive of risk-aversive behavior in that trial, and underactive in adolescents.

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

“…Interestingly, the PMC recruitment deficit in SDP resembles that found in healthy adolescents (Bjork et al, 2007), raising the possibility that chronic alcohol/drug intoxication by the SDP resulted in stunted development of the PMC. In clinical interviews, most SDP reported onset of regular heavy drinking by late adolescence.…”

“…Regressors of interest were convolved with a canonical gammavariate blood-oxygen level-dependent (BOLD) hemodynamic responses time-locked to the presentation of the ($) cue. Because penalty trials do not have outcome notifications that are temporally separated from the pre-decision period, and because they elicit a protracted activation beginning at the time of the $ cue that precludes separate deconvolution of notifications (Bjork et al, 2007), notifications were not modeled. Time series correlations with modeled responses were linearly contrasted (LC) between trial types.…”

“…We scanned SDP and controls while they performed a recently-introduced monetary risk-taking task (RTT) (Bjork et al, 2007). In the RTT, subjects passively accrued potential rewards, but were required to voluntarily terminate the accrual before a secret, varying time limit or they would "bust" and suffer a penalty of either non-reward or money loss.…”

“…First, it enabled detection of brain activation by reward accrual itself, which may be normal (or increased) in SPD--by contrasting fMRI signal change during guaranteed reward trials with signal change during motor control trials. Second, it enabled isolation of risk/reward conflictelicited brain activation, which may be lower in SDP --by contrasting signal change during risky reward accrual with signal change during reward accrual with no risk of a bad outcome (Bjork et al, 2007).…”

Menstrual cycle phase modulates cognitive control over male but not female stimuli

“…While the precise description of the ACCs function in monitoring behaviour is still a matter of some considerable investigation, there is nonetheless a reasonable consensus that it performs an evaluative function of either one's performance, a task's demands or one's effort/arousal in responding to those demands (Brown and Braver, 2005;Critchley et al, 2001;Magno et al, 2006). Given this important yet broad role it is plausible that reduced activity in this region may also be relevant to important facets of social interaction including, for example, the risky decision-making of adolescents (Bjork et al, 2007).…”