A novel implementation of local fractal dimension to calculate vessel density and FAZ area was demonstrated. Age did not impact vessel density but sectoral analyses showed greater vessel density in the inferior zone.

Aims 1) To evaluate the role of pre-existing weakness in working memory ability (WM) as a risk factor for early alcohol use as mediated by different forms of impulsivity. 2) To assess the adverse effects of progressive alcohol use on variations in WM over time. Design, Setting and Participants A community sample of 358 adolescents [48% males, Meanage(baseline) = 11.4± 0.87 years] from a longitudinal cohort design, assessed annually over four consecutive years with less than 6% attrition. Measurements Repeated assessments were conducted for the following key variables: WM (based on performance on four separate tasks), frequency of alcohol use (AU), and three forms of impulsivity, namely sensation seeking (SS), acting-without-thinking (AWT) and delay discounting (DD). Latent growth curve modeling procedures were used to identify individual trajectories of change for all key variables. Findings Weakness in WM (at baseline) significantly predicted both concurrent alcohol use and increased frequency of use over the four waves (p <.05). This effect was entirely mediated by two forms of impulsivity, AWT and DD, both of which were characterized by underlying weakness in WM. No individual variation was observed in the slopes of WM, which suggests that individual variations in alcohol use were not associated with changes in WM in our early adolescent sample. Conclusions Early adolescent alcohol use may be a consequence of (pre-existing) weaknesses in working memory (WM) rather than a cause of it. Efforts to reduce early alcohol use should consider the distinct roles of different impulsivity dimensions, in addition to WM, as potential targets of intervention.

With many adolescents using the internet to communicate with their peers, online harassment is on the rise among youth. The purpose of this study was to understand how parental monitoring and strategies parents use to regulate children's internet use (i.e., internet restriction) can help reduce online harassment among adolescents. Online survey data were collected from a nationally representative sample of parents and their 12-17 year old adolescents (n = 629; 49 % female). Structural equation modeling was used to test direct and indirect effects of parental monitoring and internet restriction on being a victim of online harassment. Potential mediators included adolescents' frequency of use of social networking websites, time spent on computers outside of school, and internet access in the adolescent's bedroom. Age and gender differences were also explored. Adolescents' reports of parental monitoring and efforts to regulate specific forms of internet use were associated with reduced rates of online harassment. Specifically, the effect of parental monitoring was largely direct and 26 times greater than parental internet restriction. The latter was associated with lower rates of harassment only indirectly by limiting internet access in the adolescent's bedroom. These effects operated similarly for younger and older adolescents and for males and females. Adolescents' perceptions of parental monitoring and awareness can be protective against online harassment. Specific restriction strategies such as regulating internet time and content can also help reduce the risk of online harassment.

Although deficits in working memory ability have been implicated in suboptimal decision making and risk taking among adolescents, its influence on early sexual initiation has so far not been examined. Analyzing 2 waves of panel data from a community sample of adolescents (N = 347; Mean age [baseline] = 13.4 years), assessed 1 year apart, the present study tested the hypothesis that weak working memory ability predicts early sexual initiation and explored whether this relationship is mediated by sensation seeking and 2 forms of impulsivity, namely acting-withoutthinking and temporal discounting. The 2 forms of impulsivity were expected to be positively associated with early sexual initiation, whereas sensation seeking was hypothesized to be unrelated or to have a protective influence, due to its positive association with working memory. Results obtained from structural equation modeling procedures supported these predictions and in addition showed that the effects of 3 prominent risk factors (Black racial identity, low socioeconomic background, and early pubertal maturation) on early sexual initiation were entirely mediated by working memory and impulsivity. The findings are discussed in regard to their implications for preventing early sexual onset among adolescents. Keywordsearly sexual debut; working memory; impulsivity; sensation seeking; delay discounting Adolescence has long been recognized as a period of heightened vulnerability to adverse health outcomes. Relative to both children and adults, adolescent rates of morbidity and mortality are disturbingly high and are linked to suboptimal decisions to engage in healthcompromising behaviors (Arnett, 1992;Dahl, 2004). Contrary to the popular notion that teenagers make light of the risks associated with their behaviors, research finds that adolescents are not only sensitive to the risks but also tend to overestimate them (Reyna & Farley, 2006). Nevertheless, whether all adolescents use these risk appraisals in an adaptive manner when making decisions regarding health-compromising behaviors, such as early sexual initiation, remains open to question.Adolescence is the developmental period when romantic and sexual exploration begins (Craver, Joyner, & Udry, 2003;B. C. Miller & Benson, 1999), with the initiation of vaginal intercourse becoming common during mid-to late adolescence (ages 16-19) Mosher, 2006). Although sexual activity among adolescents is often unprotected, sexual initiation at younger ages is found to be associated with greater involvement in risky sexual behaviors, including inconsistent condom use (Manlove, Ryan, & Franzetta, 2007;Manning, Longmore, & Giordano, 2000) and involvement with multiple sexual partners (O'Donnell, O'Donnell, & Stueve, 2001) that can increase the risk of unintended pregnancies and sexually transmitted infections (Cates, Herndon, Schulz, & Darroch, 2004;Coker et al., 1994;Greenberg, Magder, & Aral, 1992). The high individual and social costs associated with early sexual initiation are nevertheless largely preve...

Developmental imbalance models attribute the rise in risk-taking during adolescence to a universal imbalance between rising reward sensitivity and lagging cognitive control. This study tested predictions of an alternate Lifespan Wisdom Model that distinguishes between exploratory/adaptive (e.g., sensation seeking) and maladaptive (e.g., acting-without-thinking, delay discounting) risk-taking propensities and attributes the latter to a sub-set of youth with weak cognitive control. Latent trajectory modeling of six waves of data from 387 adolescents (52% females; spanning average ages of 11-18 years) revealed distinct sub-groups with heterogeneous trajectory patterns for acting-without-thinking and delay-discounting. Only those trajectory groups with weak cognitive control, characterized as "high-increasing" acting-without thinking and "high-stable" delay discounting were predictive of a maladaptive risk-taking outcome, namely substance use disorder. Sensation seeking demonstrated a universal peak, but high levels of sensation seeking were not associated with weakness in cognitive control and were unrelated to substance use disorder, controlling for impulsivity. The findings suggest that maladaptive risk-taking characterized by weak cognitive control over reward-driven impulses is a phenomenon limited to only a sub-set of youth.

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. 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. One form of impulsivity, sensation seeking, rises dramatically during adolescence and increases risks to healthy development. 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. 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. Continued translational research will help to identify strategies that protect youth as they transition to adulthood.

Based on an emerging neuroscience model of addiction, this study examines how an imbalance between two neurobehavioral systems (reward motivation and executive control) can distinguish between early adolescent progressive drug use and mere experimentation with drugs. Data from four annual assessments of a community cohort (N= 382) of 11–13 year olds were analyzed to model heterogeneity in patterns of early drug use. Baseline assessments of working memory (an indicator of the functional integrity of the executive control system) and three dimensions of impulsivity (characterizing the balance between reward-seeking and executive control systems) were used to predict heterogeneous latent classes of drug use trajectories from early-mid adolescence. Findings revealed that an imbalance resulting from weak executive control and heightened reward seeking was predictive of early progression in drug use, while heightened reward seeking balanced by a strong control system was predictive of occasional experimentation only. Implications of these results are discussed in terms of preventive interventions that can target underlying weaknesses in executive control during younger years, and potentially enable at-risk adolescents to exercise greater self-restraint in the context of rewarding drug-related cues.

Aims To test a neurobehavioral model of adolescent substance use disorder (SUD) resulting from an imbalance between a hyperactive reward motivation system and a hypoactive executive control system. Specifically, we tested (1) if early weakness in working memory (WM) and associated imbalance indicators of acting-without-thinking (AWT) and delay discounting (DD) predict SUD in late adolescence, and (2) if early drug use progression mediates this relation. Design Five waves of longitudinal data collected annually from 2005–2010, with a final follow-up in 2012. Setting & Participants Sample of 387 community adolescents (baseline ages 11–13) recruited from the Philadelphia, Pennsylvania, USA area. Measurements WM was assessed at baseline using 4 different computerized tasks. AWT and DD were assessed at baseline using self-reports. Early drug use patterns were modeled using annual self-reports of recent drug use across the first four waves. Final outcome of SUD was assessed at last wave using self-reports matched to the DSM-5 criteria for three commonly used substances: alcohol, marijuana, and tobacco. Findings Weakness in WM at baseline, associated with neurobehavioral imbalance indicators of AWT, B (SE) = −0.06(0.02), p<0.01, and DD, B (SE) = −7.30(1.93), p<0.01, was a significant predictor of SUD at final follow-up. WM predicted SUD both independent of early drug use, B (SE) = −0.36(0.12), p<0.01, and as mediated by early drug use progression, B (SE) = −0.06(0.02), p<0.01. Conclusions Adolescents with weak working memory have less control over impulsive urges, placing them at risk for later substance use disorder with some of the effects mediated by early drug use progression.