title: Twin-singleton developmental study of brain white matter anatomy.
abstract: Twin studies provide valuable insights into the analysis of genetic and environmental factors influencing human brain development. However, these findings may not generalize to singletons due to differences in pre- and postnatal environments. One would expect the effect of these differences to be greater during the early years of life. To address this concern, we compare longitudinal diffusion data of white matter regions for 26 singletons and 76 twins (monozygotic and dizygotic) from birth to 2 years of age. We use nonlinear mixed effect modeling where the temporal changes in the diffusion parameters are described by the Gompertz function. The Gompertz function describes growth trajectory in terms of intuitive parameters: asymptote, delay, and speed. We analyzed fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) for 21 regions of interest (ROIs). These ROIs included areas in the association, projection, and commissural fiber tracts. We did not find any differences in the diffusion parameters between monozygotic and dizygotic twins. In addition, FA and RD showed no developmental differences between singletons and twins for the regions analyzed. However, the delay parameter of the Gompertz function of AD for the anterior limb of the internal capsule and anterior corona radiata was significantly different between singletons and twins. Further analysis indicated that the differences are small, and twins "catch up" by the first few months of life. These results suggest that the effects of differences of pre- and postnatal environments between twins and singletons are minimal on white matter development and disappear early in life. Hum Brain Mapp 38:1009-1024, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Neda
authors.initials: N
authors.lastname: Sadeghi
authors.affiliation: Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Gilmore
authors.affiliation: Tandon School of Engineering, Department of Computer Science and Engineering, NYU, Brooklyn, USA.
authors.forename: Guido
authors.initials: G
authors.lastname: Gerig
mesh_terms: D000367:Age Factors; D001921:Brain / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000254:growth & development*; D002675:Child, Preschool; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D017711:Nonlinear Dynamics; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D066127:White Matter / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000254:growth & development*
keywords: DTI; Gompertz function; diffusion; early brain development; longitudinal brain imaging; nonlinear mixed effects modeling; twins; white matter