Planum temporale asymmetry in monozygotic and dizygotic twins: A study of heritability

This study investigates whether there is a genetic component in the development of the well-documented asymmetry of the planum temporale (PT), a structure associated with language processing. We measured PT area in 9 strongly right-handed normal dizygotic (DZ) twin pairs and 9 strongly right-handed normal monozygotic (MZ) twin pairs using three-dimensional surface renderings of the supratemporal cortex from magnetic resonance imaging (MRI) scans. Results confirmed normal PT asymmetry in both sets of twins. Within-twin comparisons of PT asymmetry showed a strong association for MZ, but not DZ, twin pairs, indicating a strong heritability for PT asymmetry. This study offers evidence of a substantial genetic factor in the development of planum temporale asymmetry.