title: Asymmetries of the arcuate fasciculus in monozygotic twins: genetic and nongenetic influences.
abstract: We assessed cerebral asymmetry for language in 35 monozygotic twin pairs. Using DTI, we reconstructed the arcuate fasciculus in each twin. Among the male twins, right-handed pairs showed greater left-sided asymmetry of connectivity in the arcuate fasciculus than did those with discordant handedness, and within the discordant group the right-handers had greater left-sided volume asymmetry of the arcuate fasciculus than did their left-handed co-twins. There were no such effects in the female twins. Cerebral asymmetry for language showed more consistent results, with the more left-cerebrally dominant twins also showing more leftward asymmetry of high anisotropic fibers in the arcuate fasciculus, a result applying equally to female as to male twins. Reversals of arcuate fasciculus asymmetry were restricted to pairs discordant for language dominance, with the left-cerebrally dominant twins showing leftward and the right-cerebrally dominant twins rightward asymmetry of anisotropic diffusion in the arcuate fasciculus. Because monozygotic twin pairs share the same genotype, our results indicate a strong nongenetic component in arcuate fasciculus asymmetry, particularly in those discordant for cerebral asymmetry.
authors.affiliation: Research Centre for Cognitive Neuroscience and Department of Psychology, The University of Auckland, Auckland, New Zealand. i.haberling@auckland.ac.nz
authors.forename: Isabelle S
authors.initials: IS
authors.lastname: Häberling
authors.forename: Gjurgjica
authors.initials: G
authors.lastname: Badzakova-Trajkov
authors.forename: Michael C
authors.initials: MC
authors.lastname: Corballis
mesh_terms: D000293:Adolescent; D000328:Adult; D019521:Body Patterning; D001921:Brain / Q000033:anatomy & histology* / Q000473:pathology; D001931:Brain Mapping; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology* / Q000473:pathology; D007839:Functional Laterality; D005838:Genotype; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D008957:Models, Genetic; D012737:Sex Factors; D013702:Temporal Lobe / Q000033:anatomy & histology* / Q000473:pathology; D014430:Twins, Monozygotic; D055815:Young Adult