This maturational gap in development of PFC-based control relative to more advanced motivational circuitry is said to result in an inevitable period of risk for adolescents ( Casey et al., 2008 Nelson, Bloom, Cameron, Amaral, Dahl, & Pine, 2002 Steinberg, 2008). In particular, the PFC and its connections with other brain regions are thought to be structurally inadequate to provide the control that is optimal for adolescent behavior. Not surprisingly, many of these activities are fraught with a certain amount of risk (e.g., driving, sex).Īt the same time that the adolescent is engaging in novel and risky activities, it is argued that the PFC has not yet matured to the point where risks can be adequately assessed and control over risk taking can be sufficiently exerted to avoid unhealthy outcomes. These circuits mature relatively early ( Fuster, 2002) and encourage the adolescent to venture away from the family and toward increasingly novel and adult-like activities ( Spear, 2007). One process that emerges early in adolescence is driven by frontostriatal reward circuits involving the ventral striatum (e.g., the nucleus accumbens) ( Casey, Getz, & Galvan, 2008 Chambers, Taylor, & Potenza, 2003 Galvan, Hare, Parra, Penn, Voss, Glover, et al., 2006). Indeed, adolescents have long been described as excessively prone to risk taking and impulsivity as exemplified by drug use, unintentional injuries (especially car accidents), and unprotected sexual activity ( Arnett, 1992).īased on these patterns of brain development and behavior, researchers from different disciplines have proposed two-processes of brain maturation that predispose the adolescent to risk taking and impulsivity. However, many researchers have argued that the protracted pruning of the PFC represents growing frontal control over behavior, the absence of which is associated with impulsivity and poor decision-making. The significance of these maturational changes has yet to be established. At the same time, there appears to be an increase in neuronal myelination. It appears that around age 11, the PFC and parietal lobes begin a period of prolonged pruning of neuronal axons resulting in thinning of cortical grey matter. The perhaps most impressive findings concern the protracted maturation of the prefrontal cortex (PFC) and parietal regions.
The dramatic growth of developmental neuroscience in the last decade has produced remarkable findings regarding brain development during childhood and adolescence ( Giedd, Blumenthal, Jeffries, Castellanos, Liu, Zijdenbos, et al., 1999 Sowell, Thompson, Tessner, & Toga, 2001).
Continued translational research will help to identify strategies that protect youth as they transition to adulthood. Instead, it is argued that lack of experience with novel adult behavior poses a much greater risk to adolescents than structural deficits in brain maturation. However, a review of the evidence for the hypothesis that limitations in brain development during adolescence restrict the ability to control impulsivity suggests that any such limitations are subtle at best. One form of impulsivity, sensation seeking, rises dramatically during adolescence and increases risks to healthy development. However, early interventions appear able to reduce the severity and impact of these traits by increasing control over behavior and persistence toward valued goals, such as educational achievement. Individual differences in impulsivity underlie a good deal of the risk taking that is observed during adolescence, and some of the most hazardous forms of this behavior are linked to impulsivity traits that are evident early in development.
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