Background. It has been suggested that failure to establish cerebral lateralisation may be related to developmental language disorder (DLD). There has been weak support for any link with handedness, but more consistent reports of associations with functional brain lateralisation for language. The consistency of lateralisation across different functions may also be important. We aimed to replicate previous findings of an association between DLD and reduced laterality on a quantitative measure of

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... hand preference (reaching across the midline) and on language laterality assessed using functional transcranial Doppler ultrasound (fTCD). Methods. From a sample of twin children aged from 6;0 to 11;11 years, we identified 107 cases of DLD and 156 typically-developing comparison cases for whom we had useable data from fTCD yielding a laterality index (LI) for language function during an animation description task. Handedness data were also available for these children. Results. Indices of handedness and language laterality for this twin sample were similar to those previously reported for single-born children. There were no differences between the DLD and TD groups on measures of handedness or language lateralisation, or on a categorical measure of consistency of left hemisphere dominance. Contrary to prediction, there was a greater incidence of right lateralisation for language in the TD group (19.90%) than the DLD group (9.30%), confirming that atypical laterality is not inconsistent with typical language development. We also failed to replicate associations between language laterality and language test scores. Discussion and Conclusions. Given the large sample studied here and the range of measures, we suggest that previous reports of atypical manual or language lateralisation in DLD may have been false positives. Bishop DVM, Watt H, Papadatou-Pastou M. 2009. An efficient and reliable method for measuring cerebral lateralization during speech with functional transcranial Doppler ultrasound. Neuropsychologia 47(2):587-590 Hadfield JD. 2010. MCMC methods for multi-response generalized linear mixed models: the MCMCglmm R package. Journal of Statistical Software 33(2):1-22 DOI 10.18637/jss.v033.i02. Harris PA, Taylor R, Thielke R, Payne J, Gonzalez N, Conde JG. 2009. Research electronic data capture (REDCap): a metadata-driven methodology and workflow process for providing translational research informatics support. Journal of Biomedical Informatics 42(2):Knake S. 2011. Determination of hemispheric dominance with mental rotation using functional transcranial Doppler sonography and fMRI. Hill EL, Bishop DVM. 1998. A reaching test reveals weak hand preference in specific language impairment and developmental co-ordination disorder. Laterality: Asymmetries of Body, Brain and Cognition 3(4):295-310 Sherr EH, Nagarajan SS. 2016. The contribution of the corpus callosum to language lateralization. The Journal of Neuroscience 36(16):4522-4533 DOI 10.1523/JNEUROSCI.3850-14.2016. Illingworth S, Bishop DVM. 2009. Atypical cerebral lateralisation in adults with compensated developmental dyslexia demonstrated using functional transcranial Doppler ultrasound. Brain and Language 111(1):61-65 Knecht S. 2006. The assessment of hemispheric lateralization in functional MRI: robustness and reproducibility. NeuroImage 33(1):204-217 Knecht S, Dräger B, Deppe M, Bobe L, Lohmann H, Flöel A, Ringelstein E-B, Henningsen H. 2000. Handedness and hemispheric language dominance in healthy humans. Brain 123(12):2512-2518 DOI 10.1093/brain/123.12.2512. Korkman M, Kirk U, Kemp SI. 1998. NEPSY: a developmental neuropsychological assessment. San Antonio: Psychological Corporation. Kuznetsova A, Brockhoff P, Christensen R. 2016. lmerTest: tests in linear mixed effects models. R Package Version, 3.0.0. Available at https:// cran.r-project.org/ package= lmerTest . Levinson HN. 1988. The cerebellar-vestibular basis of learning disabilities in children, adolescents and adults: hypothesis and study. Perceptual and Motor Skills 67(3):983-1006 DOI 10.2466/pms.1988.67.3.983. Lindell AK, Hudry K. 2013. Atypicalities in cortical structure, handedness, and functional lateralization for language in autism spectrum disorders. Neuropsychology Review 23(3):257-270 . R Core Team. 2016. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing. Available at https:// www.r-project.org/ . Rutter M, Yule W. 1970. Neurological aspects of intellectual retardation and specific reading retardation. In: Rutter M, Tizard J, Whitmore K, eds. Education, health and behavior. London: Longman, 54-74. Satz P, Fletcher JM. 1987. Left-handedness and dyslexia: an old myth revisited. Journal of Pediatric Psychology 12(2):291-298 DOI 10.1093/jpepsy/12.2.291. Somers M, Aukes MF, Ophoff RA, Boks MP, Fleer W, De Visser KC, Kahn RS, Sommer IE. 2015a. On the relationship between degree of hand-preference and degree of language lateralization. Brain and Language 144:10-15