Cerebral lateralization of writing in students at risk for dyslexia using functional transcranial Doppler ultrasonography

Abstract It is well established that the left hemisphere is dominant for oral language production in the majority of neurotypical individuals, while a more symmetrical pattern of activation is observed in cases of conditions such as dyslexia. Cerebral lateralization of written language, however, despite the critical role of writing in education and in everyday communication and the fact that children with dyslexia present with writing difficulties, has been investigated by only a few studies, none of which has sampled children, neurotypical or not. Here we aim to investigate the cerebral lateralization of written language in 20 children at risk for dyslexia compared with 20 neurotypical children using functional transcranial Doppler ultrasonography. We hypothesized that the linguistic component of writing would be less lateralized in children at risk for dyslexia compared with controls; however, there was not enough evidence to either confirm or reject this hypothesis. Furthermore, we explored the correlation between writing competence and the cerebral lateralization of the linguistic component of written language, which, as hypothesized, were not correlated. These findings suggest that, in middle childhood, cerebral lateralization for the linguistic component of writing may not be a biomarker of dyslexia risk, highlighting the need for further research into alternative neural or cognitive mechanisms underlying reading difficulties. (Preregistered Stage 1 protocol: https://osf.io/u54tk (date of in-principle acceptance: 1 December 2022).)