Neuroanatomical correlates of developmental dyslexia by Irène Altarelli (Brain and Learning Lab., University of Geneva)
Developmental dyslexia is a specific learning disorder that impacts reading abilities, despite normal education, intelligence and perception. The aim of the present work is to determine its neuroanatomical correlates, with the broader goal of identifying associations between genetic variants, brain anatomy and cognitive impairments. To this end, three studies were conducted, comparing magnetic resonance images of dyslexic and control subjects. In a first study, we analysed a variety of cortical measures with both a region of interest and a global vertex-by-vertex approach. In a second study, we focused on the ventral temporo-occipital regions, looking at the structure of functionally defined areas. We defined the subject-by-subject location of cortical regions preferentially responding to written words, faces or houses. A cortical thickness reduction in dyslexic subjects was observed in the left-hemisphere word-responsive region, an effect exclusively driven by dyslexic girls. Finally, in a third study we examined the anatomical asymmetry of the planum temporale, a region which importance in dyslexia has been widely debated. By manually labelling this structure, we observed an abnormal pattern of asymmetry in dyslexic boys only. To conclude, a number of anatomical correlates of dyslexia have emerged from the work presented here, offering a better characterisation of its brain basis.Importantly, our results also stress the importance of gender, a long neglected factor in dyslexia
