Making decisions that involve risk is part of everyday life. Some risks are greater than others (i.e., choosing a new job vs. choosing a new shampoo), and individuals vary in their tolerance of risk. Increased risk-taking is characteristic of specific developmental periods (i.e., adolescence) and psychopathological conditions (i.e., pathologic gambling, substance use). As a result, the neural basis of risk-taking has been the focus of numerous investigations. These studies often use “safe” decisions as a control condition rather than as a condition of interest per se. However, extreme avoidance of risk can also be impairing. For example, excessive avoidance of situations perceived as risky is a primary characteristic of anxiety disorders such as agoraphobia and social phobia. Therefore, identification of the neural correlates of risk avoidance can inform pathophysiological models of these disorders and their response to treatments which aim to reduce such avoidance. The present study takes an initial step in this process by using functional MRI to examine brain activity associated with risk avoidance behavior.
Converging evidence from animal and human studies implicates a distributed network of brain regions in decision-making under risk or uncertainty (Ernst & Paulus, 2005; Krain, Wilson, Arbuckle, Castellanos, & Milham, 2006; Fellows, 2004). The assessment of risk during the initial phase of decision-making involves regions implicated in reward processing, probability estimation, and action selection. For example, the orbitofrontal cortex (Elliott, Dolan, & Frith, 2000; Rogers et al., 1999) and striatum (Delgado, Nystrom, Fissell, Noll, & Fiez, 2000; Delgado, Locke, Stenger, & Fiez, 2003; Rogers et al., 2004) have been shown to track reward and loss magnitude. The anterior cingulate cortex (ACC) has been implicated in conflict detection and action selection (Milham & Banich, 2005; Hampton & O’Doherty, 2007), while parietal cortex is involved in representation of possible responses (Bunge, Hazeltine, Scanlon, Rosen, & Gabrieli, 2002). Studies of risk-taking demonstrate involvement of many of these regions in the process of selecting a risky choice. For example, increased activity in ventral striatum (Kuhnen & Knutson, 2005) and ACC has been associated with an increased probability of making a risky choice (Christopoulos, Tobler, Bossaerts, Dolan, & Schultz, 2009). The insula has been implicated in the signaling of aversive outcomes (O’Doherty, Critchley, Deichmann, & Dolan, 2003; Simmons, Matthews, Stein, & Paulus, 2004; Clark et al., 2008) and, as such, shows increased activity during selection of risky choices over safe ones (Paulus, Rogalsky, Simmons, Feinstein, & Stein, 2003). Although they have received less attention, medial posterior regions such as the posterior cingulate cortex and precuneus have also been implicated in risky decision-making. Precuneus activation has been observed in adults when making risky, as opposed to safe, decisions (Paulus et al., 2003) and studies of non-human primates show that increased neuronal activity in posterior cingulate cortex is associated with a subjective preference for risky options (McCoy & Platt, 2005).
Though fewer studies have examined the neural basis of risk avoidance, there is evidence that selection of safe choices involves an alternate set of prefrontal and temporal regions. For example, the inferior frontal gyrus (Christopoulos et al., 2009; Matthews, Simmons, Lane, & Paulus, 2004), dorsolateral prefrontal cortex (Fecteau et al., 2007; Gianotti et al., 2009; Knoch et al., 2006), and superior and middle temporal gyri (Matthews et al., 2004) have been implicated in the selection of safe choices. While insula activity increases during risky choices, activity in this region prior to a decision appears to predict risk avoidance (Kuhnen & Knutson, 2005). These studies suggest that selecting a safe or riskless choice is not simply the converse of making a risky choice, but likely involves unique neural processes.
The primary aim of the current study was to examine neural responses to the avoidance of risk. Towards this end, we developed a Wheel of Fortune task that allows participants to choose between taking a risk and passing on each trial, thereby avoiding risk. Based on previous studies, we predicted heightened activation in prefrontal and temporal regions associated with risk avoidance. Decision-making involves the consideration of multiple factors including the expected value of the choice, which represents the combination of the probability and magnitude of reward and loss. The current study parametrically varied these factors to examine their impact on risk avoidance and associated neural activity. We predicted that individuals would pass more often on trials involving greater risk and/or a smaller expected value. While laboratory measures provide important information regarding the neural correlates of risk avoidance, the relationship between brain activity and real-world avoidance of risk has not been thoroughly examined. A recent fMRI study found nucleus accumbens activity in response to reward to be significantly correlated with self-ratings of the predicted frequency of risky behaviors in adults and adolescents (Galvan, Hare, Voss, Glover, & Casey, 2007). However, the relationship between such self-ratings and neural activity associated with risk avoidance has not been studied. Therefore, we obtained a self-report measure of the frequency of risky behaviors to evaluate whether laboratory measures of risk avoidance and associated neural activity reflect real-world risk avoidance.