The genetics of cortical myelination in young adults and its relationships to cerebral surface area, cortical thickness, and intelligence: A magnetic resonance imaging study of twins and families

• Published in: NeuroImage (Orlando, Fla.) Vol. 206; p. 116319
• Main Authors: Schmitt, J. Eric, Raznahan, Armin, Liu, Siyuan, Neale, Michael C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2020; Elsevier Limited; Elsevier
• Subjects: Adult; Brain Cortical Thickness; Brain mapping; Cerebral cortex; Cerebral Cortex - anatomy & histology; Cerebral Cortex - diagnostic imaging; Child development; Cognition; Cognition & reasoning; Computed tomography; Connectome; Cortical myelination; Cortical thickness; Family; Female; Gene mapping; Genetic diversity; Genetic factors; Genetics; Heritability; Humans; Intelligence; Intelligence - genetics; Investigations; Magnetic Resonance Imaging; Male; MRI; Myelin Sheath - genetics; Myelination; Neuroimaging; Organ Size; Statistical analysis; Surface area; Temporal cortex; Temporal lobe; Twins; Twins - genetics; Twins, Dizygotic - genetics; Twins, Monozygotic - genetics; Young Adult; Young adults; Genetics; Cortical myelination; Cortical thickness; Intelligence; Surface area; MRI
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2019.116319

The cerebral cortex contains a significant quantity of intracortical myelin, but the genetics of cortical myelination (CM) in humans is not well understood. Relatively novel MRI-derived measures now enable the investigation of cortical myelination in large samples. In this study, we use a genetically-informative neuroimaging sample of 1096 young adult subjects from the Human Connectome Project in order to investigate genetic and environmental variation in CM and its relationships with cerebral surface area (SA) and cortical thickness (CT). We found that genetic factors account for approximately 50% of the observed individual differences in mean cortical myelin, 75% of the variation in total SA, and 85% of the variance in global mean CT. Although significant genetic influences were found throughout the cortex, both CM and SA demonstrated a posterior predominance, with disproportionately strong effects in the parietal and occipital lobes and significantly overlapping heritability maps (p < 0.001). Yet despite showing similar spatial heritability patterns, we found evidence that CM is genetically independent from SA at both global and vertex levels; genetically-mediated relationships between CM and CT were similarly small in magnitude. We also found small but statistically significant genetic associations between NIH Toolbox Total Cognition score and CM in the temporal lobe and insula. SA-cognition and CT-cognition correlations were less widespread compared to CM and both patterns were similar to those reported in prior studies. •We examined the genetics of cortical myelination using a twin and family design.•Cortical myelination was heritable, particularly in the posterior cerebrum.•Myelination was genetically independent from surface area and cortical thickness.•Cortical myelin was weakly correlated with intelligence via genetic factors.