Neuroimaging studies examining the effects of aging and neuropsychiatric disorders on the cerebral cortex have largely been based on measures of cortical volume. Given that cortical volume is a product of thickness and surface area, it is plausible that measures of volume capture at least 2 distinct sets of genetic influences. The present study aims to examine the genetic relationships between measures of cortical surface area and thickness. Participants were men in the Vietnam Era Twin Study of Aging (110 monozygotic pairs and 92 dizygotic pairs). Mean age was 55.8 years (range: 51-59). Bivariate twin analyses were utilized in order to estimate the heritability of cortical surface area and thickness, as well as their degree of genetic overlap. Total cortical surface area and average cortical thickness were both highly heritable (0.89 and 0.81, respectively) but were essentially unrelated genetically (genetic correlation = 0.08). This pattern was similar at the lobar and regional levels of analysis. These results demonstrate that cortical volume measures combine at least 2 distinct sources of genetic influences. We conclude that using volume in a genetically informative study, or as an endophenotype for a disorder, may confound the underlying genetic architecture of brain structure.

Experiments with young infants provide evidence for early-developing capacities to represent physical objects and to reason about object motion. Early physical reasoning accords with 2 constraints at the center of mature physical conceptions: continuity and solidity. It fails to accord with 2 constraints that may be peripheral to mature conceptions: gravity and inertia. These experiments suggest that cognition develops concurrently with perception and action and that development leads to the enrichment of conceptions around an unchanging core. The experiments challenge claims that cognition develops on a foundation of perceptual or motor experience, that initial conceptions are inappropriate to the world, and that initial conceptions are abandoned or radically changed with the growth of knowledge.

Purpose The current study examined gender and racial/ethnic (Hispanics, Non-Hispanic Caucasians, Non-Hispanic African Americans, and Non-Hispanic Asians) differences in developmental trajectories of alcohol use, heavy drinking, smoking, and marijuana use from early adolescence to young adulthood using a nationally representative sample. Methods Participants from the National Longitudinal Study of Adolescent Health (N=20,160) reported rates of alcohol use, heavy drinking, smoking and marijuana use between the ages of 12 and 34. Data analyses were completed using longitudinal multilevel modeling analyses. Results Levels of substance use increased from early adolescence to middle 20s, and then declined thereafter. Females showed higher levels of substance use in early adolescence, although males exhibited greater changes overtime and higher levels of use in mid-adolescence and early adulthood. Overall, Hispanic youth had higher initial rates of substance use, while Caucasian adolescents showed higher rates of change and had the highest levels of substance use from mid-adolescence through the early 30s. Racial/ethnic differences largely disappeared after age 30, except that African Americans showed higher final levels of smoking and marijuana use than the other racial/ethnic groups. Results provide evidence for both similarities and differences in general patterns of development and in gender and racial/ethnic differences across different forms of substance use. Conclusion Findings from the current study suggest that the critical periods for intervention and prevention of substance use may differ across gender and race/ethnicity, and that future research needs to identify common and unique mechanisms underlying developmental patterns of different forms of substance use.

In an adult population-based sample of male twins, both the genetic and the shared environmental effects on risk for the use and misuse of six classes of illicit substances were largely or entirely nonspecific in their effect. Environmental experiences unique to the person largely determine whether predisposed individuals will use or misuse one class of psychoactive substances rather than another.

High neuroticism appears to be a broad vulnerability factor for comorbid psychiatric disorders. Novelty seeking is modestly important for comorbid externalising disorders.