title: The role of parieto-temporal connectivity in pure neglect dyslexia.
abstract: The initial stages of reading are characterised by parallel and effortless access to letters constituting a word. Neglect dyslexia is an acquired reading disorder characterised by omission or substitution of the initial or the final letters of words. Rarely, the disorder appears in a'pure' form that is, without other signs of spatial neglect. Neglect dyslexia is linked to damage involving the inferior parietal lobe and regions of the temporal lobe, but the precise anatomical basis of the pure form of the disorder is unknown. Here, we show that pure neglect dyslexia is associated with decreased structural connectivity between the inferior parietal and lateral temporal lobe. We examined patient DM, who following bilateral occipito-parietal damage presented left neglect dyslexia together with right visual field loss, but no signs of spatial neglect. DM's reading errors were affected by word length and were much more frequent for pseudowords than for existing words. Most errors were omissions or substitutions of the first or second letter, and the spatial distribution of errors was similar for stimuli presented left or right of fixation. The brain lesions of DM comprised the inferior and superior parietal lobule as well as the cuneus and precuneus of the left hemisphere, and the angular gyrus and lateral occipital cortex of the right hemisphere. Diffusion tensor imaging revealed bilateral decrease of fibre tracts connecting the inferior parietal lobule with the superior and middle temporal cortex. These findings suggest that parieto-temporal connections play a significant role for the deployment of attention within words during reading.
authors.affiliation: Division of Neurorehabilitation, Department of Clinical Neurosciences, University Hospitals Geneva, Geneva, Switzerland; Laboratory of Cognitive Neurorehabilitation, Faculty of Medicine, University of Geneva, Switzerland; Faculty of Psychology and Educational Sciences, University of Geneva, Geneva, Switzerland. Electronic address: radek.ptak@hcuge.ch.
authors.forename: Radek
authors.initials: R
authors.lastname: Ptak
authors.affiliation: Division of Neurorehabilitation, Department of Clinical Neurosciences, University Hospitals Geneva, Geneva, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Di Pietro
authors.affiliation: Unit of Acute Neurorehabilitation, Department of Clinical Neurosciences, University Hospital Lausanne, 1011 Lausanne, Switzerland.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Pignat
mesh_terms: D056324:Diffusion Tensor Imaging; D004410:Dyslexia / Q000209:etiology / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000503:physiopathology; D010296:Parietal Lobe / Q000503:physiopathology*; D010468:Perceptual Disorders / Q000150:complications; D011932:Reading; D013702:Temporal Lobe / Q000503:physiopathology*; D014794:Visual Fields / Q000502:physiology
keywords: Disconnection; Neglect dyslexia; Parietal lobe; Reading; Spatial neglect; Temporal lobe; Visual attention