Neural dissociation of phonological and visual attention span disorders in developmental dyslexia: FMRI evidence from two case reports |
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Authors: | Peyrin C Lallier M Démonet J F Pernet C Baciu M Le Bas J F Valdois S |
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Institution: | a CNRS UMR 5105, 38040 Grenoble, France b Laboratoire de Psychologie et NeuroCognition, Université Pierre Mendès France, 38040 Grenoble Cedex 09, France c Basque Center on Cognition Brain and Language, 20009 San Sebastian, Spain d INSERM U825, Pôle Neurosciences, Hôpital Purpan, 31059 Toulouse Cedex 03, France e SFC Brain Imaging Research Center, University of Edinburgh, Edinburgh, EH4 2XU Scotland, United Kingdom f Institut Universitaire de France, 75005 Paris, France g INSERM U836/Université Joseph Fourier, Institut des Neurosciences, 38043 Grenoble Cedex 09, France |
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Abstract: | A dissociation between phonological and visual attention (VA) span disorders has been reported in dyslexic children. This study investigates whether this cognitively-based dissociation has a neurobiological counterpart through the investigation of two cases of developmental dyslexia. LL showed a phonological disorder but preserved VA span whereas FG exhibited the reverse pattern. During a phonological rhyme judgement task, LL showed decreased activation of the left inferior frontal gyrus whereas this region was activated at the level of the controls in FG. Conversely, during a visual categorization task, FG demonstrated decreased activation of the parietal lobules whereas these regions were activated in LL as in the controls. These contrasted patterns of brain activation thus mirror the cognitive disorders’ dissociation. These findings provide the first evidence for an association between distinct brain mechanisms and distinct cognitive deficits in developmental dyslexia, emphasizing the importance of taking into account the heterogeneity of the reading disorder. |
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Keywords: | Developmental dyslexia Heterogeneity Phonological disorder Visual attention span Dyslexia subtypes Parietal dysfunction Broca&rsquo s area |
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