Cerebral lateralization of language in children at risk for dyslexia: A review of neuroscientific evidence

Abstract

Dyslexia is a neurodevelopmental disorder of word-level processing. Ιt is typically diagnosed at school age, when children are expected to learn to read and spell accurately and fluently. One of the neurobiological traits that characterize children with dyslexia is the atypical cerebral lateralization of language. Typical cerebral lateralization of language -meaning increased activation of the left hemisphere compared to the right one during language tasks- is shown for the majority of neurotypical individuals. However, hemispheric activation in children with dyslexia during language processing is more bilateral or right-lateralized. There is evidence that cerebral lateralization of language is partially or completely established before the onset of literacy training, in infancy or kindergarten years. Therefore, atypical lateralization can also be observed in that age and provide an indication of the risk for dyslexia prior to diagnosis. In the present review, our main focus is to present neuroscientific evidence that has associated different components of the cerebral lateralization of language -namely, functional, structural, functional connectivity, and neurogenetic- with the risk for dyslexia. In addition, we stress out the gap of knowledge regarding the cerebral lateralization of written language in children and we present our future goals to address this gap.