title: Age-Related Differences and Heritability of the Perisylvian Language Networks.
abstract: Acquisition of language skills depends on the progressive maturation of specialized brain networks that are usually lateralized in adult population. However, how genetic and environmental factors relate to the age-related differences in lateralization of these language pathways is still not known. We recruited 101 healthy right-handed subjects aged 9-40 years to investigate age-related differences in the anatomy of perisylvian language pathways and 86 adult twins (52 monozygotic and 34 dizygotic) to understand how heritability factors influence language anatomy. Diffusion tractography was used to dissect and extract indirect volume measures from the three segments of the arcuate fasciculus connecting Wernicke's to Broca's region (i.e., long segment), Broca's to Geschwind's region (i.e., anterior segment), and Wernicke's to Geschwind's region (i.e., posterior segment). We found that the long and anterior arcuate segments are lateralized before adolescence and their lateralization remains stable throughout adolescence and early adulthood. Conversely, the posterior segment shows right lateralization in childhood but becomes progressively bilateral during adolescence, driven by a reduction in volume in the right hemisphere. Analysis of the twin sample showed that genetic and shared environmental factors influence the anatomy of those segments that lateralize earlier, whereas specific environmental effects drive the variability in the volume of the posterior segment that continues to change in adolescence and adulthood. Our results suggest that the age-related differences in the lateralization of the language perisylvian pathways are related to the relative contribution of genetic and environmental effects specific to each segment.
  
  
  CONCLUSIONS
  Our study shows that, by early childhood, frontotemporal (long segment) and frontoparietal (anterior segment) connections of the arcuate fasciculus are left and right lateralized, respectively, and remain lateralized throughout adolescence and early adulthood. In contrast, temporoparietal (posterior segment) connections are right lateralized in childhood, but become progressively bilateral during adolescence. Preliminary twin analysis suggested that lateralization of the arcuate fasciculus is a heterogeneous process that depends on the interplay between genetic and environment factors specific to each segment. Tracts that exhibit higher age effects later in life (i.e., posterior segment) appear to be influenced more by specific environmental factors.
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences, Natbrainlab, Centre for Neuroimaging Sciences, NeMo Laboratory, Department of General Psychology, University of Padova, 35131 Padova. Italy, sanja.budisavljevic@gmail.com m.catani@iop.kcl.ac.uk.
authors.forename: Sanja
authors.initials: S
authors.lastname: Budisavljevic
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences, Natbrainlab, Centre for Neuroimaging Sciences.
authors.forename: Flavio
authors.initials: F
authors.lastname: Dell'Acqua
authors.affiliation: Social, Genetic and Developmental Psychiatry Research Centre.
authors.forename: Frühling V
authors.initials: FV
authors.lastname: Rijsdijk
authors.affiliation: Department of Psychological Medicine, and.
authors.forename: Fergus
authors.initials: F
authors.lastname: Kane
authors.affiliation: Department of Psychological Medicine, and.
authors.forename: Marco
authors.identifier: http://orcid.org/0000-0001-6681-147X
authors.initials: M
authors.lastname: Picchioni
authors.affiliation: Department of Psychological Medicine, and.
authors.forename: Philip
authors.initials: P
authors.lastname: McGuire
authors.affiliation: Department of Psychological Medicine, and Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom, Department of Psychology and State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, and.
authors.forename: Timothea
authors.initials: T
authors.lastname: Toulopoulou
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Anna
authors.initials: A
authors.lastname: Georgiades
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Sridevi
authors.initials: S
authors.lastname: Kalidindi
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Kravariti
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Murray
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences.
authors.forename: Declan G
authors.initials: DG
authors.lastname: Murphy
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences, Natbrainlab, Centre for Neuroimaging Sciences, National Autism Unit, South London and Maudsley NHS Foundation Trust, United Kingdom.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Craig
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences, Natbrainlab, Centre for Neuroimaging Sciences, sanja.budisavljevic@gmail.com m.catani@iop.kcl.ac.uk.
authors.forename: Marco
authors.initials: M
authors.lastname: Catani
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D001369:Axons / Q000648:ultrastructure; D065711:Broca Area / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology* / Q000648:ultrastructure; D002648:Child; D056324:Diffusion Tensor Imaging; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D007804:Language Development; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009929:Organ Size; D019655:Quantitative Trait, Heritable; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D065813:Wernicke Area / Q000502:physiology; D055815:Young Adult
keywords: arcuate fasciculus; diffusion tensor tractography; heritability; language; lateralization; network asymmetry