Genetic influences on neonatal cortical thickness and surface area

Abstract

Genetic and environmental influences on cortical thickness (CT) and surface area (SA) are thought to vary in a complex and dynamic way across the lifespan. It has been established that CT and SA are genetically distinct in older children, adolescents, and adults, and that heritability varies across cortical regions. Very little, however, is known about how genetic and environmental factors influence infant CT and SA. Using structural MRI, we performed the first assessment of genetic and environmental influences on normal variation of SA and CT in 360 twin neonates. We observed strong and significant additive genetic influences on total SA (a2 = 0.78) and small and nonsignificant genetic influences on average CT (a2 = 0.29). Moreover, we found significant genetic overlap (genetic correlation = 0.65) between these global cortical measures. Regionally, there were minimal genetic influences across the cortex for both CT and SA measures and no distinct patterns of genetic regionalization. Overall, outcomes from this study suggest a dynamic relationship between CT and SA during the neonatal period and provide novel insights into how genetic influences shape cortical structure during early development.

Keywords: MRI; brain development; gray matter; heritability; infant; twin.

© 2018 Wiley Periodicals, Inc.

Figures

Figure 1

Genetic, common environmental, and unique environmental influences on neonatal (a) cortical thickness and (b) surface area for 78 cortical regions. Genetic influences are displayed in blue, common environmental influences are displayed in orange, and unique environmental influences are displayed in gray. Genetic influences are also projected onto the cortical surface. Subcortical regions are in gray and were not analyzed

Figure 2

Heatmap of genetic correlations between 78 ROIs of (a) neonatal cortical thickness and (b) neonatal surface area. Dendrograms are displayed on each heatmap to present the results from a hierarchal cluster analysis. Clusters are visually displayed on the neonatal brain surface

Figure 3

Genetic correlations (rG) between neonatal cortical thickness and surface area for each ROI projected onto the cortical surface. Subcortical regions are in gray and were not analyzed

Figure 4

Genetic, common environmental, and unique environmental influences for regional neonatal (a) cortical thickness and (b) surface area without adjustments for global brain measures. Genetic influences are displayed in blue, common environmental influences are displayed in orange, and unique environmental influences are displayed in gray

Figure 5

Genetic, common environmental, and unique environmental influences for regional neonatal (a) cortical thickness and (b) surface area with adjustments for brain size, age, sex, and scanner parameters. Genetic influences are displayed in blue, common environmental influences are displayed in orange, and unique environmental influences are displayed in gray