Diffusion tensor imaging-based tissue segmentation: validation and application to the developing child and adolescent brain. (25/524)

We present and validate a novel diffusion tensor imaging (DTI) approach for segmenting the human whole-brain into partitions representing grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF). The approach utilizes the contrast among tissue types in the DTI anisotropy vs. diffusivity rotational invariant space. The DTI-based whole-brain GM and WM fractions (GMf and WMf) are contrasted with the fractions obtained from conventional magnetic resonance imaging (cMRI) tissue segmentation (or clustering) methods that utilized dual echo (proton density-weighted (PDw)), and spin-spin relaxation-weighted (T2w) contrast, in addition to spin-lattice relaxation weighted (T1w) contrasts acquired in the same imaging session and covering the same volume. In addition to good correspondence with cMRI estimates of brain volume, the DTI-based segmentation approach accurately depicts expected age vs. WM and GM volume-to-total intracranial brain volume percentage trends on the rapidly developing brains of a cohort of 29 children (6-18 years). This approach promises to extend DTI utility to both micro and macrostructural aspects of tissue organization.  (+info)

Cannabis and cognitive dysfunction: parallels with endophenotypes of schizophrenia? (26/524)

Currently, there is a lot of interest in cannabis use as a risk factor for the development of schizophrenia. Cognitive dysfunction associated with long-term or heavy cannabis use is similar in many respects to the cognitive endophenotypes that have been proposed as vulnerability markers of schizophrenia. In this overview, we examine the similarities between these in the context of the neurobiology underlying cognitive dysfunction, particularly implicating the endogenous cannabinoid system, which plays a significant role in attention, learning and memory, and in general, inhibitory regulatory mechanisms in the brain. Closer examination of the cognitive deficits associated with specific parameters of cannabis use and interactions with neurodevelopmental stages and neural substrates will better inform our understanding of the nature of the association between cannabis use and psychosis. The theoretical and clinical significance of further research in this field is in enhancing our understanding of underlying pathophysiology and improving the provision of treatments for substance use and mental illness.  (+info)

Risk and promotive factors in families, schools, and communities: a contextual model of positive youth development in adolescence. (27/524)

OBJECTIVE: Emerging evidence about optimal youth development highlights the importance of both reducing negative behavior and promoting positive behavior. In our study we tested a contextual model derived from positive youth-development theory by examining the association of family, school, and community risk and promotive factors, with several outcome indices of both positive and negative adolescent development. METHODS: A sample of 42305 adolescents aged 11 to 17 (51% girls) was drawn from the 2003 National Survey of Children's Health. Survey item composites were formed representing promotive and risk factors in the family (eg, closeness, aggression) and school and community (eg, community connectedness, school violence). Outcome composites reflected positive (social competence, health-promoting behavior, self-esteem) and negative (externalizing, internalizing, academic problems) developmental outcomes. Ordinary least squares regression was used to test the overall model. RESULTS: Between 0.10 and 0.50 of the variance in each outcome was explained by the contextual model. Multiple positive family characteristics were related to adolescent social competence and self-esteem, as well as lowered levels of internalizing and externalizing behavior and academic problems. Family communication, rules about television, and parents' own healthy behavior were related to adolescent health-promoting behavior. School and community safety were associated with increased social competence and decreased externalizing behavior. School violence was related to adolescent internalizing and externalizing behavior, as well as academic problems and lower self-esteem. CONCLUSIONS: Our results support the proposition that healthy adolescent development has roots in multiple contexts. Youth who were involved in contexts that provided positive resources from important others (ie, parents, schools, and communities) not only were less likely to exhibit negative outcomes, but also were more likely to show evidence of positive development. These findings provide important implications for intervention and prevention efforts and, more generally, for the promotion of positive, competent, and healthy youth development.  (+info)

A multilevel study of the associations between economic and social context, stage of adolescence, and physical activity and body mass index. (28/524)

OBJECTIVE: Prevention efforts targeting adolescent risk behavior have had limited effectiveness, partly because of the reliance on individual-level interventions that do not consider the context within which behavior occurs. In addition, the role of development has not been well studied regarding its possible moderating effects on contextual influences on behavior. The purpose of this study was to examine the influence of economic and social context on the odds of being inactive or having above-normal weight and whether the influence differed on the basis of stage of adolescence. METHODS: Analysis used a subset of adolescents aged 10 to 17 years from the National Survey of Children's Health (n = 37930) from all states and the District of Columbia (n = 51). Dependent variables included physical activity and BMI. State-level economic context was measured by the proportion of families living below 200% of the federal poverty level. Social context was measured by aggregated means of responses to 2 indicators of social capital: mutual aid and social trust. Multilevel modeling was conducted to investigate associations between state-level economic and social context and physical activity and BMI, while controlling for individual sociodemographic characteristics, and whether these associations were dependent on an individual's stage of adolescence. RESULTS: Both state-level mutual aid and social trust were significantly related to the odds of an adolescent not meeting current physical activity recommendations, yet state-level poverty was not. For BMI, all 3 state-level variables were significant predictors of having an above-normal BMI. Evidence was found of the moderating influence of stage of adolescence for both outcomes. CONCLUSIONS: These findings point to the need for the inclusion of contextual-level data in surveillance systems assessing risk behavior in adolescents and consideration of the multilevel nature of the growing problem of inactivity and above-normal weight when focusing public health prevention efforts.  (+info)

Development of age-specific adolescent metabolic syndrome criteria that are linked to the Adult Treatment Panel III and International Diabetes Federation criteria. (29/524)

OBJECTIVES: The study objectives were to develop age-specific adolescent metabolic syndrome (MetS) criteria that were linked to the health-based Adult Treatment Panel III (ATP) and International Diabetes Federation (IDF) adult criteria. BACKGROUND: There has been no consistency in the criteria used to diagnose the MetS in adolescents. Studies have either applied adult criteria or arbitrarily chosen adolescent high-risk cut-points. METHODS: The adolescent (12 to 19 years old) MetS criteria developed in this study were linked to the ATP and IDF adult criteria with LMS growth curve modeling for each MetS component (waist circumference, systolic and diastolic blood pressure, high-density lipoprotein cholesterol, triglycerides, and glucose). Nationally representative data from the National Health and Nutrition Examination Surveys were used to develop the growth curves. RESULTS: The growth curves for each MetS component passed through the ATP and IDF cut-points at 20 years of age such that adolescent cut-points were linked to the adult values. Age- and gender-specific cut-points for each MetS component were developed that can be used to define high-risk values in 12- to 19-year-olds. The prevalence of MetS in adolescents nearly doubled over the last decade and was 7.6% on the basis of the newly developed ATP adolescent criteria and 9.6% on the basis of the newly developed IDF adolescent criteria. CONCLUSIONS: These new criteria should provide improved and age-appropriate approaches for diagnosing MetS among adolescents.  (+info)

Meat supplementation improves growth, cognitive, and behavioral outcomes in Kenyan children. (30/524)

A randomized, controlled school feeding study was conducted in rural Embu District, Kenya to test for a causal link between animal-source food intake and changes in micronutrient nutrition and growth, cognitive, and behavioral outcomes. Twelve primary schools were randomly assigned to 1 of 4 groups. Children in Standard I classes received the local plant-based dish githeri as a midmorning school snack supplemented with meat, milk, or fat added to equalize energy content in all feedings. The Control children received no feedings but participated in data collection. Main outcome measures assessed at baseline and longitudinally were 24-h food intake recall, anthropometry, cognitive function, physical activity, and behaviors during school free play. For cognitive function, the Meat group showed the steepest rate of increase on Raven's Progressive Matrices scores and in zone-wide school end-term total and arithmetic test scores. The Plain githeri and Meat groups performed better over time than the Milk and Control groups (P < 0.02-0.03) on arithmetic tests. The Meat group showed the greatest increase in percentage time in high levels of physical activity and in initiative and leadership behaviors compared with all other groups. For growth, in the Milk group only younger and stunted children showed a greater rate of gain in height. The Meat group showed near doubling of upper midarm muscle area, and the Milk group a smaller degree of increase. This is the first randomized, controlled feeding study to examine the effect of meat- vs. milk- vs. plant-based snacks on functional outcomes in children.  (+info)

Early sexual maturation, central adiposity and subsequent overweight in late adolescence. a four-year follow-up of 1605 adolescent Norwegian boys and girls: the Young HUNT study. (31/524)

BACKGROUND: Early sexual maturation has been associated with overweight that may persist after the completion of biological growth and development. We have prospectively examined the influence of early sexual maturation on subsequent overweight in late adolescence and assessed if this association was modified by central adiposity in early adolescence. METHODS: 1605 Norwegian adolescents were followed from early (baseline, mean age 14.2 years) to late adolescence (follow-up, mean age 18.2 years). Maturational timing was assessed by self-reports of pubertal status (PDS) in boys and age at menarche (AAM) in girls. Central adiposity was classified according to waist circumference (waist) measured at baseline, using age and gender specific medians as cut off. Overweight was classified according to International Obesity Task Force (IOTF) standards. RESULTS: At follow-up, early sexual maturation in girls, but not in boys, was associated with overweight. This association, however, was restricted to girls with high waist circumference (> median) at baseline (OR, 2.7, 95% CI 1.5-4.9). Thus, age at menarche was not associated with overweight in girls with low waist (< or = median) at baseline. Central adiposity was, independent of maturational timing, associated with higher BMI at follow-up in both genders, but differences were more pronounced among early matured girls (3.5 kg/m2), than among intermediate (2.7 kg/m2) and late matured girls (1.2 kg/m2). CONCLUSION: In girls, the combination of central adiposity and early age at menarche appears to increase the risk of being overweight in late adolescence.  (+info)

Social outcomes in childhood brain disorder: a heuristic integration of social neuroscience and developmental psychology. (32/524)

The authors propose a heuristic model of the social outcomes of childhood brain disorder that draws on models and methods from both the emerging field of social cognitive neuroscience and the study of social competence in developmental psychology/psychopathology. The heuristic model characterizes the relationships between social adjustment, peer interactions and relationships, social problem solving and communication, social-affective and cognitive-executive processes, and their neural substrates. The model is illustrated by research on a specific form of childhood brain disorder, traumatic brain injury. The heuristic model may promote research regarding the neural and cognitive-affective substrates of children's social development. It also may engender more precise methods of measuring impairments and disabilities in children with brain disorder and suggest ways to promote their social adaptation.  (+info)