What twin studies tell us about the heritability of brain development, morphology, and function: a review

Abstract

The development of brain structure and function shows large inter-individual variation. The extent to which this variation is due to genetic or environmental influences has been investigated in twin studies using structural and functional Magnetic Resonance Imaging (MRI). The current review presents an overview of twin studies using MRI in children, adults and elderly, and focuses on cross-sectional and longitudinal designs. The majority of the investigated brain measures are heritable to a large extent (60-80%), although spatial differences in heritability are observed as well. Cross-sectional studies suggest that heritability estimates slightly increase from childhood to adulthood. Long-term longitudinal studies are better suited to study developmental changes in heritability, but these studies are limited. Results so far suggest that the heritability of change over time is relatively low or absent, but more studies are needed to confirm these findings. Compared to brain structure, twin studies of brain function are scarce, and show much lower heritability estimates (~40%). The insights from heritability studies aid our understanding of individual differences in brain structure and function. With the recent start of large genetic MRI consortia, the chance of finding genes that explain the heritability of brain morphology increases. Gene identification may provide insight in biological mechanisms involved in brain processes, which in turn will learn us more about healthy and disturbed brain functioning.

Fig. 1

With publisher’s [Nature Publishing Group] and first author’s permission copied from Thompson et al. , Genetic Influences on Brain Structure. Nature Neuroscience, 4(12); 1253–1258. The correlations between MZ and DZ twins in gray matter distribution. MZ twin pairs are almost perfectly correlated in their gray matter distribution while DZ twin pairs show less resemblance. Note: F frontal, S/M sensory motor, W Wernicke’s cortices

Fig. 2

With publisher’s [Oxford University Press] and first author’s permission copied from Baaré et al. , Quantitative Genetic Modeling of Variation in Human Brain Morphology. Cerebral Cortex, 11; 816–824. The brains of female MZ (upper row) and DZ (lower row) twin pairs, and their female siblings. The upper block shows transverse slices through the anterior and posterior commissures. The lower blocks show three-dimensional brain renderings showing the top and left side from the brains respectively