![]() ![]() In contrast, activity in dorsofrontal structures, most notably the dorsolateral prefrontal cortex (PFC), is associated with mediating behaviour in the direction of safer over risky prospects ( Campbell-Meiklejohn et al., 2008) and with delaying gratification in favour of superior but delayed rewards ( McClure et al., 2004). This region responds preferentially to (i) low-probability rewards that are better-than-expected and so more subjectively gratifying ( Yacubian et al., 2006 Smith et al., 2009) and (ii) immediate rewards over those that are superior in the longer-term ( McClure et al., 2004). The nucleus accumbens, part of the ventral striatum, has been shown to code both probability and delay features of rewards indiscriminately, pointing towards a common ‘neural currency’ ( Peters and Büchel, 2009). Ventral frontostriatal regions have largely been implicated both in motivating behaviour towards obtaining desired outcomes-or rewards-and, subsequently, in the hedonic impact of rewards once obtained. ![]() The functional basis of optimal decision-making Here, we present recent developments on the functional basis of self-control in decision-making to examine suboptimal decision-making in bipolar disorder during a probabilistic task in which safe and risky reward prospects are evaluated. Common frontostriatal regions are implicated in optimal versus impulsive decision-making, whether the decision involves selecting a tastier over a healthier food option ( Hare et al., 2011), or a safe but low-return prospect over a risky but potentially more lucrative investment ( Peters and Büchel, 2009). Impulsivity can be conceptualized as a diminished self-control to suppress behaviours that afford preferred (highly desirable) outcomes, but which contravene higher-order or longer-term goals and so are ultimately suboptimal in the long run ( Hare et al., 2009 Diekhof et al., 2012). Impulsive and risky decision-making is characteristic of several psychiatric disorders including substance dependence ( Rogers et al., 2010), bipolar disorder ( Swann et al., 2009), attention deficit hyperactivity disorder ( Scheres et al., 2010), pathological gambling ( Rogers et al., 2010) and psychopathy ( Vitacco and Rogers, 2001). The findings extend a functional neuroanatomical account of disorders characterized by clinically impulsive decision-making, and provide targets for evaluating interventions that foster self-control. Our findings suggest that clinically impulsive and risky decision-making are related to subjective valuation that is biased towards lower-order preference, with diminished integration of higher-order goals. Response to high-probability rewards in dorsolateral prefrontal cortex was inversely associated with trait impulsivity and risk-taking in the bipolar disorder group. In control subjects, however, ventromedial prefrontal activation was positively associated with both ventral striatum and dorsolateral prefrontal activity patients evidenced a strong positive association with ventral striatum, but a negative association with dorsolateral prefrontal cortex. This group also showed increased anticipatory and outcome-locked activity in ventral striatum in response to rewards. ![]() The bipolar disorder group showed the opposite pattern with preferential response to risky rewards. In control subjects, anticipatory and outcome-locked activity in dorsolateral prefrontal cortex was greater for safe than risky reward prospects. Activity in response to high-probability (‘safe’) and low-probability (‘risky’) prospects was measured during both anticipation, and outcome. Twenty euthymic patients with bipolar disorder not in receipt of antipsychotic medication and 20 case-matched controls performed a roulette task during functional magnetic resonance imaging. We hypothesized that in bipolar disorder the weighting of valuation signals converging on ventromedial prefrontal cortex are more heavily weighted towards ventral striatum inputs (lower-order), with less weighting of dorsolateral prefrontal cortex inputs (higher-order). We sought to determine whether this is driven by a failure to effectively weight the lower-order goal of obtaining a strongly desired reward in relation to higher-order goals, and how this relates to trait impulsivity and risk-taking. Bipolar disorder is characterized by impaired decision-making captured in impulsivity and risk-taking. ![]()
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