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1.  Working Memory Ability Predicts Trajectories of Early Alcohol Use in Adolescents: The Mediational Role of Impulsivity 
Addiction (Abingdon, England)  2012;108(3):506-515.
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.
doi:10.1111/add.12001
PMCID: PMC3568437  PMID: 23033972
2.  Early Adolescent Sexual Debut: The Mediating Role of Working Memory Ability, Sensation Seeking, and Impulsivity 
Developmental psychology  2012;48(5):1416-1428.
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-without-thinking 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.
doi:10.1037/a0027491
PMCID: PMC3896330  PMID: 22369334
early sexual debut; working memory; impulsivity; sensation seeking; delay discounting
3.  Is Executive Cognitive Function Associated with Youth Gambling? 
Journal of Gambling Studies  2012;28(2):225-238.
Our objectives for this report were to identify trajectories of youth gambling behavior, and to examine their relation to executive cognitive function (ECF) and associated problem behaviors. Philadelphia school children, enrolled at ages 10–12 years (n = 387; 49% male), completed three annual assessments of risk behaviors, ECF, impulsivity, problem behaviors and demographics. Across ages 10–15 years, using methods from Nagin et al., two groups were identified: Early Gamblers (n = 111) initiated early and continued in later assessments, and Later Gamblers (n = 276) initiated at later ages and gambled less. Betting money on cards and sports were the most frequently reported gambling behaviors. Using gambling group as outcome, final backward selection logistic regression model showed Early Gamblers are more likely male (P = 0.001), report more active coping (P = 0.042), impulsive behaviors (P ≤ 0.008), and have friends who gamble (P = 0.001). Groups were similar in ECF, parental monitoring, marital status, SES, and race. Early Gamblers had higher incidence of problem behaviors and drug use (all P ≤ 0.006). Two gambling groups were identified in early adolescence with Early Gamblers showing higher levels of impulsivity and comorbid problems but similar levels of ECF compared to Late Gamblers. As more gambling groups are identified through later adolescence, ECF may emerge as a relevant precursor of problem gambling at this later time.
doi:10.1007/s10899-011-9256-y
PMCID: PMC3217082  PMID: 21698342
Youth gambling; Trajectories; Executive cognitive function; Impulsivity; Adolescence
4.  Correction: Selective Impact of Early Parental Responsivity on Adolescent Stress Reactivity 
PLoS ONE  2013;8(4):10.1371/annotation/9294793a-c267-46db-94de-16a3b6705a1e.
doi:10.1371/annotation/9294793a-c267-46db-94de-16a3b6705a1e
PMCID: PMC3643845
5.  Selective Impact of Early Parental Responsivity on Adolescent Stress Reactivity 
PLoS ONE  2013;8(3):e58250.
Research in animals has shown that early life experience, particularly parenting behaviors, influences later-life stress reactivity. Despite the tremendous relevance of this finding to human development and brain function, it has not been tested prospectively in humans. In this study two aspects of parenting were measured at age 4 in a sample of healthy, low socioeconomic status, African American children, and stress reactivity was measured in the same children 11–14 years later using a modified version of the Trier Social Stress Test (n = 55). Salivary cortisol was measured before, during and after the stressor and data were analyzed using piecewise hierarchical linear modeling. Parental responsivity, independent of the use of physical discipline, was positively related to cortisol reactivity. Effects were independent of subjective appraisals of the stressor and were also independent of other environmental risk factors and current psychosocial functioning. Therefore this study demonstrates in a novel and precise fashion that early childhood parental responsivity prospectively and independently predicts stress reactivity in adolescence.
doi:10.1371/journal.pone.0058250
PMCID: PMC3596401  PMID: 23555573
6.  Longitudinal Follow-up of Poor Inner-city Youth Between Ages 8 and 18: Intentions Versus Reality 
Pediatrics  2012;129(3):473-479.
OBJECTIVES:
(1) To document, at ages 8 to 10, children’s perceptions of their future and, at ages 16 to 18, youth outcomes; and (2) to assess early childhood factors associated with trajectory-altering events (TAEs), defined as youth risk behaviors that may modify developmental trajectories.
METHODS:
A prospective longitudinal study of 97 poor, inner-city, African American youth followed since birth who completed (1) early childhood environment, cognitive, and social-emotional evaluations, as well as an inventory at ages 8 to 10 of perceptions of their futures; and (2) evaluation for presence or absence of 4 TAEs documented at ages 16 to 18: drug use, adjudication, school failure, and teen parenthood.
RESULTS:
At age 9.4 ± 0.5, 94% of participants felt it unlikely they would try marijuana; 93% felt they were unlikely to get arrested; 92% felt they were likely to attend college or trade school; 81% did not know one could become pregnant with first-time sex. Age 18.1 ± 0.8 outcomes showed that 33% had used drugs, 33% had been adjudicated, 19% had school failure, and 20% had become parents. Fifty-six percent had ≥1 TAE. No relationship was found between childhood perceptions and intentions and documented outcomes. Odds of having a TAE increased with greater exposure to violence and poorer home environment.
CONCLUSIONS:
Young inner-city children are idealistic regarding their future. By ages 16 to 18 however, more than half of this cohort had a TAE. Factors most strongly associated with a TAE were greater exposure to violence and poorer home environment.
doi:10.1542/peds.2011-2111
PMCID: PMC3289529  PMID: 22351882
poverty; urban population; home environment; early intervention; risk taking
7.  Does Adolescent Risk Taking Imply Weak Executive Function? A Prospective Study of Relations between Working Memory Performance, Impulsivity, and Risk Taking in Early Adolescence 
Developmental science  2011;14(5):1119-1133.
Studies of brain development suggest that the increase in risk taking observed during adolescence may be due to insufficient prefrontal executive function compared to a more rapidly developing subcortical motivation system. We examined executive function as assessed by working memory ability in a community sample of youth (n = 387, ages 10 to 12 at baseline) in three annual assessments to determine its relation to two forms of impulsivity (sensation seeking and acting without thinking) and a wide range of risk and externalizing behavior. Using structural equation modeling, we tested a model in which differential activation of the dorsal and ventral striatum produces imbalance in the function of these brain regions. For youth high in sensation seeking, both regions were predicted to develop with age. However, for youth high in the tendency to act without thinking, the ventral striatum was expected to dominate. The model predicted that working memory ability would exhibit (1) early weakness in youth high in acting without thinking but (2) growing strength in those high in sensation seeking. In addition, it predicted that (3) acting without thinking would be more strongly related to risk and externalizing behavior than sensation seeking. Finally, it predicted that (4) controlling for acting without thinking, sensation seeking would predict later increases in risky and externalizing behavior. All four of these predictions were confirmed. The results indicate that the rise in sensation seeking that occurs during adolescence is not accompanied by a deficit in executive function and therefore requires different intervention strategies from those for youth whose impulsivity is characterized by early signs of acting without thinking.
doi:10.1111/j.1467-7687.2011.01061.x
PMCID: PMC3177153  PMID: 21884327
8.  Adolescents with and without Gestational Cocaine Exposure: Longitudinal Analysis of Inhibitory Control, Memory and Receptive Language 
Neurotoxicology and teratology  2011;33(1):36-46.
doi:10.1016/j.ntt.2010.08.004
PMCID: PMC3052975  PMID: 21256423
gestational cocaine exposure; latent effects; GEE; attention; working memory; language; incidental memory; longitudinal
9.  Neighborhood disadvantage and adolescent stress reactivity 
Lower socioeconomic status (SES) is associated with higher levels of life stress, which in turn affect stress physiology. SES is related to basal cortisol and diurnal change, but it is not clear if SES is associated with cortisol reactivity to stress. To address this question, we examined the relationship between two indices of SES, parental education and concentrated neighborhood disadvantage, and the cortisol reactivity of African–American adolescents to a modified version of the Trier Social Stress Test (TSST). We found that concentrated disadvantage was associated with cortisol reactivity and this relationship was moderated by gender, such that higher concentrated disadvantage predicted higher cortisol reactivity and steeper recovery in boys but not in girls. Parental education, alone or as moderated by gender, did not predict reactivity or recovery, while neither education nor concentrated disadvantage predicted estimates of baseline cortisol. This finding is consistent with animal literature showing differential vulnerability, by gender, to the effects of adverse early experience on stress regulation and the differential effects of neighborhood disadvantage in adolescent males and females. This suggests that the mechanisms underlying SES differences in brain development and particularly reactivity to environmental stressors may vary across genders.
doi:10.3389/fnhum.2012.00277
PMCID: PMC3469875  PMID: 23091454
socioeconomic status; neighborhood disadvantage; parental education; stress reactivity; cortisol; HPA axis
10.  In vivo Venous Blood T1 Measurement using Inversion Recovery TrueFISP in Children and Adults 
A time-efficient method is described for in-vivo venous blood T1 measurement using multi-phase inversion-recovery prepared balanced steady-state free precession imaging (IR-TrueFISP). Computer simulations and validation experiments using a flow phantom were carried out to demonstrate the accuracy of the proposed method for measuring blood T1, by taking advantage of the continuous inflow of fresh blood with longitudinal magnetization undisturbed by previous RF pulses. In vivo measurement of venous blood T1 in the sagittal sinus was carried out in 26 healthy children and adults aged 7 to 39 years. The measured venous blood T1 values decreased with age as a whole (p=0.006) and were higher in females than males (p =0.013), matching the expected developmental changes and gender differences in human hematocrit level. The estimated mean blood T1 values were highly correlated with normal hematocrit levels across age and gender groups (Spearman r=0.93, p=0.008). The longitudinal repeatability of this technique was 4.0% as measured by the within-subject coefficient of variation. The proposed multi-phase IR-TrueFISP method is a feasible technique for fast (< 1 min) and reliable in-vivo venous blood T1 measurement, and may serve as an index of hematocrit level in individual subjects.
doi:10.1002/mrm.22484
PMCID: PMC2946493  PMID: 20564586
Blood T1; longitudinal relaxation; inversion recovery; TrueFISP
11.  Early Parental Care Is Important for Hippocampal Maturation: Evidence from Brain Morphology in Humans 
NeuroImage  2009;49(1):1144-1150.
The effects of early life experience on later brain structure and function have been studied extensively in animals, yet the relationship between childhood experience and normal brain development in humans remains largely unknown. Using a unique longitudinal data set including ecologically valid in-home measures of early experience during childhood (at age 4 and 8 years) and high-resolution structural brain imaging during adolescence (mean age 14 years), we examined the effects on later brain morphology of two dimensions of early experience: parental nurturance and environmental stimulation. Parental nurturance at age 4 predicts the volume of the left hippocampus in adolescence, with better nurturance associated with smaller hippocampal volume. In contrast, environmental stimulation did not correlate with hippocampal volume. Moreover, the association between hippocampal volume and parental nurturance disappears at age 8, supporting the existence of a sensitive developmental period for brain maturation. These findings indicate that variation in normal childhood experience is associated with differences in brain morphology, and hippocampal volume is specifically associated with early parental nurturance. Our results provide neuroimaging evidence supporting the important role of warm parental care during early childhood for brain maturation.
doi:10.1016/j.neuroimage.2009.07.003
PMCID: PMC2764790  PMID: 19595774
Childhood experience; Parental nurturance; Environmental stimulation; Hippocampus; Morphology
13.  Executive Cognitive Functions and Impulsivity as Correlates of Risk Taking and Problem Behavior in Preadolescents 
Neuropsychologia  2009;47(13):2916-2926.
Early initiation of drugs and other risk behaviors portends dysfunctional developmental outcomes. For example, youth who initiate drug use prior to age 14 exhibit the highest rates of lifetime drug use and substance use disorder (SUD) (Grant & Dawson, 1998). Early users of drugs also tend to engage in other externalizing behaviors, such as aggressive behavior and rule breaking that place them at risk for poor developmental trajectories (McGue, Iacono, & Krueger, 2006; Moffitt, 1993, 1996; Moffitt & Caspi, 2001). Early intervention may be able to alter these trajectories toward a healthier course. We examine and test neuropsychological explanations for these early manifestations of problem behavior to help identify potential points of intervention.
doi:10.1016/j.neuropsychologia.2009.06.019
PMCID: PMC2780004  PMID: 19560477
14.  Cerebral hemodynamics in preterm infants during positional intervention measured with diffuse correlation spectroscopy and transcranial Doppler ultrasound 
Optics express  2009;17(15):12571-12581.
Four very low birth weight, very premature infants were monitored during a 12° postural elevation using diffuse correlation spectroscopy (DCS) to measure microvascular cerebral blood flow (CBF) and transcranial Doppler ultrasound (TCD) to measure macrovascular blood flow velocity in the middle cerebral artery. DCS data correlated significantly with peak systolic, end diastolic, and mean velocities measured by TCD (pA =0.036, 0.036, 0.047). Moreover, population averaged TCD and DCS data yielded no significant hemodynamic response to this postural change (p>0.05). We thus demonstrate feasibility of DCS in this population, we show correlation between absolute measures of blood flow from DCS and blood flow velocity from TCD, and we do not detect significant changes in CBF associated with a small postural change (12°) in these patients.
PMCID: PMC2723781  PMID: 19654660

Results 1-14 (14)