br Introduction Compared with both

Introduction Compared with both adults and children, adolescents have an enhanced propensity to engage in rewarding, risky behavior (Somerville et al., 2010). Sexual risk behavior – including early sexual debut, higher number of partners, or unprotected intercourse – is a particularly important domain of risk behavior that emerges during adolescence, as it involves decisions to engage in potentially highly rewarding experiences that can lead to serious health consequences, including HIV and other sexually transmitted infections (STIs), or unplanned pregnancy (Abma et al., 2010; Kann, 2016). Changes in risky behavior occur in tandem with greater behavioral and neural sensitivity to rewards during adolescence, the transitional developmental period between the completion of puberty and the attainment of adulthood status (Casey et al., 2008; Somerville et al., 2010). Conceptual models of the rise in sensation seeking during adolescence have focused on the balance among the brain’s affective and control systems, positing a more protracted developmental course in control systems than reward systems (Casey et al., 2008; Somerville et al., 2010; Steinberg, 2005) or a temporary imbalance of influence among threat, reward, and control systems (Ernst and Fudge, 2009). In addition, development in the dopamine system over the course of adolescence leads to greater innervation of medial prefrontal cortex (mPFC), with implications for enhanced capacity for inhibitory control generally and regulation of basic striatal reward responding (Gomes et al., 2016; Luna et al., 2015). Models of adolescent neurodevelopment have recently been extended to adolescents’ sexual behavior (Victor and Hariri, 2016), with the hypothesis that increased reward responsiveness, decreased threat detection and reactivity, and immature behavioral regulation capacity underlie risky sexual behavior. Social context and the evaluation of social information relative to oneself (e.g. self-referential processing) are critical factors in adolescent alzheimer\'s disease and sexual development. During adolescence, the aforementioned changes in the neurodevelopmental balance of threat, reward, and control systems co-occurs with a heightened sensitivity to social stimuli, in which youth are highly motivated to affiliate and gain status with peers (Albert et al., 2013; Crone and Dahl, 2012). Further, the neural circuitry underlying self-referential processing undergoes maturation during adolescence, with particular implications for social behavior, including sexual behavior (Sebastian et al., 2008). Specifically, adolescents are increasingly aware of others’ evaluation of them and that they may change their behavior in order to receive more positive evaluation. Indeed, adolescents’ engagement in risky behaviors is often met with peer rewards, such as increased social status (Brechwald and Prinstein, 2011). It is thus unsurprising that most of adolescents’ risky behaviors occur in peer social contexts (Albert et al., 2013). Social context—while relevant for a broad range of adolescent risk behaviors—may be especially salient in sexual risk behavior. Sexual behavior is inherently interpersonal, and is unique among health risk behaviors because it involves high emotional arousal in response to both environmental and interoceptive stimuli (Victor and Hariri, 2016). During adolescence, sexual activity is a novel social experience that can have a variety of meanings including status changes among peers (e.g., Mayeux et al., 2008) and the formation of intimate romantic relationships (e.g., Williams and Russell, 2013). The integration of the brain’s social and self-referential circuitry with key regions including precuneus and temporoparietal junction (Amft et al., 2015), reward circuitry (e.g., ventral striatum (VS), anterior insula (aIns), and dorsal mPFC; Haber and Knutson, 2010), and emotion regulation circuitry (e.g., ventrolateral PFC (vlPFC), anterior cingulate cortex (ACC); Steinberg, 2005) may play a role in adolescent sexual development. Studies in healthy adults demonstrate that viewing sexual stimuli indeed elicits activation of these regions independent of general emotional arousal (Wehrum et al., 2013; Wehrum-Osinsky et al., 2014), and greater vs responsiveness to sexual images predicts future sexual desire and “indulgence in” sexual behavior (Demos et al., 2012). Interactions among pubertal gonadal hormones are also postulated to impact development of these neural reward systems (for review, see Sinclair et al., 2014) and adolescent sexual behavior (for review, see Baams et al., 2015). Further, brain development and social experience can have a bidirectional influence. Based on non-human primate findings of hormonal changes in relation to sexual experience, it has been proposed that sexual behavior itself may exert an influence on adolescent brain development (Forbes and Dahl, 2010).