Genetic and environmental influences on neuroimaging phenotypes: A meta-analytical perspective on twin imaging studies

Because brain structure and function are affected in neurological and psychiatric disorders, it is important to disentangle the sources of variation in these phenotypes. Over the past 15 years, twin studies have found evidence for both genetic and environmental influences on neuroimaging phenotypes, but considerable variation across studies makes it difficult to draw clear conclusions about the relative magnitude of these influences. Here we performed the first meta-analysis of structural MRI data from 48 studies on >1,250 twin pairs, and diffusion tensor imaging data from 10 studies on 444 twin pairs. The proportion of total variance accounted for by genes (A), shared environment (C), and unshared environment (E), was calculated by averaging A, C, and E estimates across studies from independent twin cohorts and weighting by sample size. The results indicated that additive genetic estimates were significantly different from zero for all metaanalyzed phenotypes, with the exception of fractional anisotropy (FA) of the callosal splenium, and cortical thickness (CT) of the uncus, left parahippocampal gyrus, and insula. For many phenotypes there was also a significant influence of C. We now have good estimates of heritability for many regional and lobar CT measures, in addition to the global volumes. Confidence intervals are wide and number of individuals small for many of the other phenotypes. In conclusion, while our meta-analysis shows that imaging measures are strongly influenced by genes, and that novel phenotypes such as CT measures, FA measures, and brain activation measures look especially promising, replication across independent samples and demographic groups is necessary.

Intersectionality, rural criminology, and re-imaging the boundaries of critical criminology

One of the significant shortcomings of the criminological canon, including its critical strands – feminist, cultural and green – has been its urbancentric bias. In this theoretical model, rural communities are idealised as conforming to the typical small-scale traditional societies based on cohesive organic forms of solidarity and close density acquaintance networks. This article challenges the myth that rural communities are relatively crime free places of ‘moral virtue’ with no need for a closer scrutiny of rural context, rural places, and rural peoples about crime and other social problems. This challenge is likewise woven into the conceptual and empirical narratives of the other articles in this Special Edition, which we argue constitute an important body of innovative work, not just for reinvigorating debates in rural criminology, but also critical criminology. For without a critical perspective of place, the realities of context are too easily overlooked. A new criminology of crime and place will help keep both critical criminology and rural criminology firmly anchored in the sociological and the criminological imagination. We argue that intersectionality, a framework that resists privileging any particular social structural category of analysis, but is cognisant of the power effects of colonialism, class, race and gender, can provide the theoretical scaffolding to further develop such a project.

Development of insula connectivity between ages 12 and 30 revealed by high angular resolution diffusion imaging

The insula, hidden deep within the Sylvian fissures, has proven difficult to study from a connectivity perspective. Most of our current information on the anatomical connectivity of the insula comes from studies of nonhuman primates and post mortem human dissections. To date, only two neuroimaging studies have successfully examined the connectivity of the insula. Here we examine how the connectivity of the insula develops between ages 12 and 30, in 307 young adolescent and adult subjects scanned with 4-Tesla high angular resolution diffusion imaging (HARDI). The density of fiber connections between the insula and the frontal and parietal cortex decreased with age, but the connection density between the insula and the temporal cortex generally increased with age. This trajectory is in line with well-known patterns of cortical development in these regions. In addition, males and females showed different developmental trajectories for the connection between the left insula and the left precentral gyrus. The insula plays many different roles, some of them affected in neuropsychiatric disorders; this information on the insula's connectivity may help efforts to elucidate mechanisms of brain disorders in which it is implicated.