Cerebral morphometry in monozygotic and dizygotic twins: A study of heritability

This study investigates whether there is a genetic component in cerebral development as measured by: (1) the degree of asymmetry between the frontal and occipital lobes; and (2) the complexity of gyral patterns, as measured by the gyrification index (GI). We measured frontal and occipital lobe volumes and the GI in 9 strongly right-handed normal dizygotic (DZ) twins pairs and 9 strongly right-handed normal monozygotic (MZ) twin pairs. Results confirmed normal asymmetry of lobe volume in both sets of twins, and GI measurements were comparable to those in previous studies. Within-twin comparisons of the relationship between frontal and occipital lobe volume showed a significant association for MZ, but not DZ, twin pairs, indicating strong heritability for this asymmetry. Within-twin comparisons of the GI showed a strong association for both MZ and DZ twins, indicating a strong environmental component in the development of gyral patterns.